大場 靖子(オオバ ヤスコ)
人獣共通感染症国際共同研究所 分子病態・診断部門



  • 人獣共通感染症国際共同研究所 分子病態・診断部門


  • 准教授


  • 博士(医学)(北海道大学)


J-Global ID


  • アルボウイルス   蚊媒介性ウイルス   ポリオーマウイルス   JCウイルス   


  • ライフサイエンス / ウイルス学


  • 日本分子生物学会   日本ウイルス学会   



  • Fumihiro Kodama, Hiroki Yamaguchi, Eunsil Park, Kango Tatemoto, Mariko Sashika, Ryo Nakao, Yurino Terauchi, Keita Mizuma, Yasuko Orba, Hiroaki Kariwa, Katsuro Hagiwara, Katsunori Okazaki, Akiko Goto, Rika Komagome, Masahiro Miyoshi, Takuya Ito, Kimiaki Yamano, Kentaro Yoshii, Chiaki Funaki, Mariko Ishizuka, Asako Shigeno, Yukari Itakura, Lesley Bell-Sakyi, Shunji Edagawa, Atsushi Nagasaka, Yoshihiro Sakoda, Hirofumi Sawa, Ken Maeda, Masayuki Saijo, Keita Matsuno
    Nature communications 12 1 5539 - 5539 2021年09月20日 
    The increasing burden of tick-borne orthonairovirus infections, such as Crimean-Congo hemorrhagic fever, is becoming a global concern for public health. In the present study, we identify a novel orthonairovirus, designated Yezo virus (YEZV), from two patients showing acute febrile illness with thrombocytopenia and leukopenia after tick bite in Hokkaido, Japan, in 2019 and 2020, respectively. YEZV is phylogenetically grouped with Sulina virus detected in Ixodes ricinus ticks in Romania. YEZV infection has been confirmed in seven patients from 2014-2020, four of whom were co-infected with Borrelia spp. Antibodies to YEZV are found in wild deer and raccoons, and YEZV RNAs have been detected in ticks from Hokkaido. In this work, we demonstrate that YEZV is highly likely to be the causative pathogen of febrile illness, representing the first report of an endemic infection associated with an orthonairovirus potentially transmitted by ticks in Japan.
  • Kentaro Uemura, Haruaki Nobori, Akihiko Sato, Takao Sanaki, Shinsuke Toba, Michihito Sasaki, Akiho Murai, Noriko Saito-Tarashima, Noriaki Minakawa, Yasuko Orba, Hiroaki Kariwa, William W Hall, Hirofumi Sawa, Akira Matsuda, Katsumi Maenaka
    iScience 103120 - 103120 2021年09月11日 
    Newly emerging or re-emerging viral infections continue to cause significant morbidity and mortality every year worldwide, resulting in serious effects on both health and the global economy. Despite significant drug discovery research against dengue viruses (DENV) and severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), no fully effective and specific drugs directed against these viruses have been discovered. Here, we examined the anti-DENV activity of tubercidin derivatives from a compound library from Hokkaido University and demonstrated that 5-hydroxymethyltubercidin (HMTU, HUP1108) possessed both potent anti-flavivirus and anti-coronavirus activities at submicromolar levels without significant cytotoxicity. Furthermore, HMTU inhibited viral RNA replication and specifically inhibited replication at the late stages of the SARS-CoV-2 infection process. Finally, we demonstrated that HMTU 5'-triphosphate inhibited RNA extension catalyzed by the viral RNA-dependent RNA-polymerase. Our findings suggest that HMTU has the potential of serving as a lead compound for the development of a broad-spectrum of antiviral agents, including SARS-CoV-2.
  • Michihito Sasaki, Mai Kishimoto, Yukari Itakura, Koshiro Tabata, Kittiya Intaruck, Kentaro Uemura, Shinsuke Toba, Takao Sanaki, Akihiko Sato, William W Hall, Yasuko Orba, Hirofumi Sawa
    Biochemical and biophysical research communications 577 146 - 151 2021年09月10日 
    The human lung cell A549 is susceptible to infection with a number of respiratory viruses. However, A549 cells are resistant to Severe Acute Respiratory Syndrome-Coronavirus-2 (SARS-CoV-2) infection in conventional submerged culture, and this would appear to be due to low expression levels of the SARS-CoV-2 entry receptor: angiotensin-converting enzyme-2 (ACE2). Here, we examined SARS-CoV-2 susceptibility to A549 cells after adaptation to air-liquid interface (ALI) culture. A549 cells in ALI culture yielded a layer of mucus on their apical surface, exhibited decreased expression levels of the proliferation marker KI-67 and intriguingly became susceptible to SARS-CoV-2 infection. We found that A549 cells increased the endogenous expression levels of ACE2 and TMPRSS2 following adaptation to ALI culture conditions. Camostat, a TMPRSS2 inhibitor, reduced SARS-CoV-2 infection in ALI-cultured A549 cells. These findings indicate that ALI culture switches the phenotype of A549 cells from resistance to susceptibility to SARS-CoV-2 infection through upregulation of ACE2 and TMPRSS2.
  • Hayato Harima, Michihito Sasaki, Yasuko Orba, Kosuke Okuya, Yongjin Qiu, Christida E Wastika, Katendi Changula, Masahiro Kajihara, Edgar Simulundu, Tomoyuki Yamaguchi, Yoshiki Eto, Akina Mori-Kajihara, Akihiko Sato, Satoshi Taniguchi, Ayato Takada, Masayuki Saijo, Bernard M Hang'ombe, Hirofumi Sawa
    PLoS neglected tropical diseases 15 9 e0009768  2021年09月07日 
    BACKGROUND: Pteropine orthoreovirus (PRV) is an emerging bat-borne zoonotic virus that causes severe respiratory illness in humans. Although PRVs have been identified in fruit bats and humans in Australia and Asia, little is known about the prevalence of PRV infection in Africa. Therefore, this study performed an PRV surveillance in fruit bats in Zambia. METHODS: Egyptian fruit bats (Rousettus aegyptiacus, n = 47) and straw-colored fruit bats (Eidolon helvum, n = 33) captured in Zambia in 2017-2018 were screened for PRV infection using RT-PCR and serum neutralization tests. The complete genome sequence of an isolated PRV strain was determined by next generation sequencing and subjected to BLAST and phylogenetic analyses. Replication capacity and pathogenicity of the strain were investigated using Vero E6 cell cultures and BALB/c mice, respectively. RESULTS: An PRV strain, tentatively named Nachunsulwe-57, was isolated from one Egyptian fruit bat. Serological assays demonstrated that 98% of sera (69/70) collected from Egyptian fruit bats (n = 37) and straw-colored fruit bats (n = 33) had neutralizing antibodies against PRV. Genetic analyses revealed that all 10 genome segments of Nachunsulwe-57 were closely related to a bat-derived Kasama strain found in Uganda. Nachunsulwe-57 showed less efficiency in viral growth and lower pathogenicity in mice than another PRV strain, Miyazaki-Bali/2007, isolated from a patient. CONCLUSIONS: A high proportion of Egyptian fruit bats and straw-colored fruit bats were found to be seropositive to PRV in Zambia. Importantly, a new PRV strain (Nachunsulwe-57) was isolated from an Egyptian fruit bat in Zambia, which had relatively weak pathogenicity in mice. Taken together, our findings provide new epidemiological insights about PRV infection in bats and indicate the first isolation of an PRV strain that may have low pathogenicity to humans.
  • Michihito Sasaki, Shinsuke Toba, Yukari Itakura, Herman M Chambaro, Mai Kishimoto, Koshiro Tabata, Kittiya Intaruck, Kentaro Uemura, Takao Sanaki, Akihiko Sato, William W Hall, Yasuko Orba, Hirofumi Sawa
    mBio 12 4 e0141521  2021年08月31日 
    Severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) possesses a discriminative polybasic cleavage motif in its spike protein that is recognized by the host furin protease. Proteolytic cleavage activates the spike protein, thereby affecting both the cellular entry pathway and cell tropism of SARS-CoV-2. Here, we investigated the impact of the furin cleavage site on viral growth and pathogenesis using a hamster animal model infected with SARS-CoV-2 variants bearing mutations at the furin cleavage site (S gene mutants). In the airway tissues of hamsters, the S gene mutants exhibited low growth properties. In contrast to parental pathogenic SARS-CoV-2, hamsters infected with the S gene mutants showed no body weight loss and only a mild inflammatory response, thereby indicating the attenuated variant nature of S gene mutants. This transient infection was sufficient for inducing protective neutralizing antibodies that cross-react with different SARS-CoV-2 lineages. Consequently, hamsters inoculated with S gene mutants showed resistance to subsequent infection with both the parental strain and the currently emerging SARS-CoV-2 variants belonging to lineages B.1.1.7 and P.1. Taken together, our findings revealed that the loss of the furin cleavage site causes attenuation in the airway tissues of hamsters and highlighted the potential benefits of S gene mutants as potential immunogens. IMPORTANCE SARS-CoV-2 uses its spike protein to enter target cells. The spike protein is cleaved by a host protease, and this event facilitates viral entry and broadens cell tropism. In this study, we employed SARS-CoV-2 mutants lacking the S protein cleavage site and characterized their growth and pathogenicity using hamsters, a laboratory animal model for SARS-CoV-2 infection. These mutants exerted low pathogenicity but induced sufficient levels of neutralizing antibodies in hamsters, which protected hamsters from rechallenge with pathogenic clinical SARS-CoV-2 strains. These virus mutants may be used as protective immunogens against SARS-CoV-2 infection.
  • Taishi Onodera, Shunsuke Kita, Yu Adachi, Saya Moriyama, Akihiko Sato, Takao Nomura, Shuhei Sakakibara, Takeshi Inoue, Takashi Tadokoro, Yuki Anraku, Kohei Yumoto, Cong Tian, Hideo Fukuhara, Michihito Sasaki, Yasuko Orba, Nozomi Shiwa, Naoko Iwata, Noriyo Nagata, Tateki Suzuki, Jiei Sasaki, Tsuyoshi Sekizuka, Keisuke Tonouchi, Lin Sun, Shuetsu Fukushi, Hiroyuki Satofuka, Yasuhiro Kazuki, Mitsuo Oshimura, Tomohiro Kurosaki, Makoto Kuroda, Yoshiharu Matsuura, Tadaki Suzuki, Hirofumi Sawa, Takao Hashiguchi, Katsumi Maenaka, Yoshimasa Takahashi
    Immunity 2021年08月24日 
    Potent neutralizing SARS-CoV-2 antibodies often target the spike protein receptor-binding site (RBS), but the variability of RBS epitopes hampers broad neutralization of multiple sarbecoviruses and drifted viruses. Here, using humanized mice, we identified an RBS antibody with a germline VH gene that potently neutralized SARS-related coronaviruses, including SARS-CoV and SARS-CoV-2 variants. X-ray crystallography revealed coordinated recognition by the heavy chain of non-RBS conserved sites and the light chain of RBS with a binding angle mimicking the angiotensin-converting enzyme 2 (ACE2) receptor. The minimum footprints in the hypervariable region of RBS contributed to the breadth of neutralization, which was enhanced by immunoglobulin G3 (IgG3) class switching. The coordinated binding resulted in broad neutralization of SARS-CoV and emerging SARS-CoV-2 variants of concern. Low-dose therapeutic antibody treatment in hamsters reduced the virus titers and morbidity during SARS-CoV-2 challenge. The structural basis for broad neutralizing activity may inform the design of a broad spectrum of therapeutics and vaccines.
  • Rachel Milomba Velu, Geoffrey Kwenda, Liyali Libonda, Caroline Cleopatra Chisenga, Bumbangi Nsoni Flavien, Obvious Nchimunya Chilyabanyama, Michelo Simunyandi, Samuel Bosomprah, Nicholus Chintu Sande, Katendi Changula, Walter Muleya, Monicah Mirai Mburu, Benjamin Mubemba, Simbarashe Chitanga, John Tembo, Matthew Bates, Nathan Kapata, Yasuko Orba, Masahiro Kajihara, Ayato Takada, Hirofumi Sawa, Roma Chilengi, Edgar Simulundu
    Pathogens (Basel, Switzerland) 10 8 2021年08月10日 
    Emerging and re-emerging mosquito-borne viral diseases are a threat to global health. This systematic review aimed to investigate the available evidence of mosquito-borne viral pathogens reported in Zambia. A search of literature was conducted in PubMed and Google Scholar for articles published from 1 January 1930 to 30 June 2020 using a combination of keywords. Eight mosquito-borne viruses belonging to three families, Togaviridae, Flaviviridae and Phenuiviridae were reported. Three viruses (Chikungunya virus, Mayaro virus, Mwinilunga virus) were reported among the togaviruses whilst four (dengue virus, West Nile virus, yellow fever virus, Zika virus) were among the flavivirus and only one virus, Rift Valley fever virus, was reported in the Phenuiviridae family. The majority of these mosquito-borne viruses were reported in Western and North-Western provinces. Aedes and Culex species were the main mosquito-borne viral vectors reported. Farming, fishing, movement of people and rain patterns were among factors associated with mosquito-borne viral infection in Zambia. Better diagnostic methods, such as the use of molecular tools, to detect the viruses in potential vectors, humans, and animals, including the recognition of arboviral risk zones and how the viruses circulate, are important for improved surveillance and design of effective prevention and control measures.
  • Taisho Yamada, Seiichi Sato, Yuki Sotoyama, Yasuko Orba, Hirofumi Sawa, Hajime Yamauchi, Michihito Sasaki, Akinori Takaoka
    Nature immunology 22 7 820 - 828 2021年07月 
    Efficient immune responses against viral infection are determined by sufficient activation of nucleic acid sensor-mediated innate immunity1,2. Coronavirus disease 2019, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), remains an ongoing global pandemic. It is an urgent challenge to clarify the innate recognition mechanism to control this virus. Here we show that retinoic acid-inducible gene-I (RIG-I) sufficiently restrains SARS-CoV-2 replication in human lung cells in a type I/III interferon (IFN)-independent manner. RIG-I recognizes the 3' untranslated region of the SARS-CoV-2 RNA genome via the helicase domains, but not the C-terminal domain. This new mode of RIG-I recognition does not stimulate its ATPase, thereby aborting the activation of the conventional mitochondrial antiviral-signaling protein-dependent pathways, which is in accordance with lack of cytokine induction. Nevertheless, the interaction of RIG-I with the viral genome directly abrogates viral RNA-dependent RNA polymerase mediation of the first step of replication. Consistently, genetic ablation of RIG-I allows lung cells to produce viral particles that expressed the viral spike protein. By contrast, the anti-SARS-CoV-2 activity was restored by all-trans retinoic acid treatment through upregulation of RIG-I protein expression in primary lung cells derived from patients with chronic obstructive pulmonary disease. Thus, our findings demonstrate the distinctive role of RIG-I as a restraining factor in the early phase of SARS-CoV-2 infection in human lung cells.
  • Masahiro Kajihara, Martin Simuunza, Ngonda Saasa, George Dautu, Akina Mori-Kajihara, Yongjin Qiu, Ryo Nakao, Yoshiki Eto, Hayato Furumoto, Bernard M Hang'ombe, Yasuko Orba, Hirofumi Sawa, Edgar Simulundu, Shuetsu Fukushi, Shigeru Morikawa, Masayuki Saijo, Jiro Arikawa, Swithine Kabilika, Mwaka Monze, Victor Mukonka, Aaron Mweene, Ayato Takada, Kumiko Yoshimatsu
    PLoS neglected tropical diseases 15 6 e0009452  2021年06月 
    Crimean-Congo hemorrhagic fever (CCHF) is a tick-borne zoonosis with a high case fatality rate in humans. Although the disease is widely found in Africa, Europe, and Asia, the distribution and genetic diversity of CCHF virus (CCHFV) are poorly understood in African countries. To assess the risks of CCHF in Zambia, where CCHF has never been reported, epidemiologic studies in cattle and ticks were conducted. Through an indirect immunofluorescence assay, CCHFV nucleoprotein-specific serum IgG was detected in 8.4% (88/1,047) of cattle. Among 290 Hyalomma ticks, the principal vector of CCHFV, the viral genome was detected in 11 ticks. Phylogenetic analyses of the CCHFV S and M genome segments revealed that one of the detected viruses was a genetic reassortant between African and Asian strains. This study provides compelling evidence for the presence of CCHFV in Zambia and its transmission to vertebrate hosts.
  • Michihito Sasaki, Yukari Itakura, Mai Kishimoto, Koshiro Tabata, Kentaro Uemura, Naoto Ito, Makoto Sugiyama, Christida E Wastika, Yasuko Orba, Hirofumi Sawa
    Journal of virology 2021年03月24日 
    Group A rotaviruses (RVAs) are representative enteric virus species and major causes of diarrhea in humans and animals. The RVA virion is a triple-layered particle, and the outermost layer consists of the glycoprotein VP7 and spike protein VP4. To increase the infectivity of RVA, VP4 is proteolytically cleaved into VP5* and VP8* subunits by trypsin; and these subunits form a rigid spike structure on the virion surface. In this study, we investigated the growth of RVAs in cells transduced with type II transmembrane serine proteases (TTSPs), which cleave fusion proteins and promote infection by respiratory viruses, such as influenza viruses, paramyxoviruses, and coronaviruses. We identified TMPRSS2 and TMPRSS11D as host TTSPs that mediate trypsin-independent and multi-cycle infection by human and animal RVA strains. In vitro cleavage assays revealed that recombinant TMPRSS11D cleaved RVA VP4. We also found that TMPRSS2 and TMPRSS11D promote the infectious entry of immature RVA virions, but they could not activate nascent progeny virions in the late phase of infection. This observation differed from the TTSP-mediated activation process of paramyxoviruses, revealing the existence of virus species-specific activation processes in TTSPs. Our study provides new insights into the interaction between RVAs and host factors, and TTSP-transduced cells offer potential advantages for RVA research and development.ImportanceProteolytic cleavage of the viral VP4 protein is essential for virion maturation and infectivity in group A rotaviruses (RVAs). In cell culture, RVAs are propagated in culture medium supplemented with the exogenous protease trypsin, which cleaves VP4 and induces the maturation of progeny RVA virions. In this study, we demonstrated that the host proteases TMPRSS2 and TMPRSS11D mediate the trypsin-independent infection and growth of RVA. Our data revealed that the proteolytic activation of RVAs by TMPRSS2 and TMPRSS11D occurs at the viral entry step. Because TMPRSS2 and TMPRSS11D gene expression induced similar or higher levels of RVA growth as trypsin-supplemented culture, this approach offers potential advantages for RVA research and development.
  • Kentaro Uemura, Michihito Sasaki, Takao Sanaki, Shinsuke Toba, Yoshimasa Takahashi, Yasuko Orba, William W Hall, Katsumi Maenaka, Hirofumi Sawa, Akihiko Sato
    Scientific reports 11 1 5376 - 5376 2021年03月08日 
    Although the spread of Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) has resulted in a worldwide pandemic, there are currently no virus-specific drugs that are fully effective against SARS-CoV-2. Only a limited number of human-derived cells are capable of supporting SARS-CoV-2 replication and the infectivity of SARS-CoV-2 in these cells remains poor. In contrast, monkey-derived Vero cells are highly susceptibility to infection with SARS-CoV-2, although they are not suitable for the study of antiviral effects by small molecules due to their limited capacity to metabolize drugs compared to human-derived cells. In this study, our goal was to generate a virus-susceptible human cell line that would be useful for the identification and testing of candidate drugs. Towards this end, we stably transfected human lung-derived MRC5 cells with a lentiviral vector encoding angiotensin-converting enzyme 2 (ACE2), the cellular receptor for SARS-CoV-2. Our results revealed that SARS-CoV-2 replicates efficiently in MRC5/ACE2 cells. Furthermore, viral RNA replication and progeny virus production were significantly reduced in response to administration of the replication inhibitor, remdesivir, in MRC5/ACE2 cells compared with Vero cells. We conclude that the MRC5/ACE2 cells will be important in developing specific anti-viral therapeutics and will assist in vaccine development to combat SARS-CoV-2 infections.
  • Hayato Harima, Yasuko Orba, Shiho Torii, Yongjin Qiu, Masahiro Kajihara, Yoshiki Eto, Naoya Matsuta, Bernard M Hang'ombe, Yuki Eshita, Kentaro Uemura, Keita Matsuno, Michihito Sasaki, Kentaro Yoshii, Ryo Nakao, William W Hall, Ayato Takada, Takashi Abe, Michael T Wolfinger, Martin Simuunza, Hirofumi Sawa
    Scientific reports 11 1 4883 - 4883 2021年03月01日 
    Tick-borne flaviviruses (TBFVs) infect mammalian hosts through tick bites and can cause various serious illnesses, such as encephalitis and hemorrhagic fevers, both in humans and animals. Despite their importance to public health, there is limited epidemiological information on TBFV infection in Africa. Herein, we report that a novel flavivirus, Mpulungu flavivirus (MPFV), was discovered in a Rhipicephalus muhsamae tick in Zambia. MPFV was found to be genetically related to Ngoye virus detected in ticks in Senegal, and these viruses formed a unique lineage in the genus Flavivirus. Analyses of dinucleotide contents of flaviviruses indicated that MPFV was similar to those of other TBFVs with a typical vertebrate genome signature, suggesting that MPFV may infect vertebrate hosts. Bioinformatic analyses of the secondary structures in the 3'-untranslated regions (UTRs) revealed that MPFV exhibited unique exoribonuclease-resistant RNA (xrRNA) structures. Utilizing biochemical approaches, we clarified that two xrRNA structures of MPFV in the 3'-UTR could prevent exoribonuclease activity. In summary, our findings provide new information regarding the geographical distribution of TBFV and xrRNA structures in the 3'-UTR of flaviviruses.
  • Mai Kishimoto, Kentaro Uemura, Takao Sanaki, Akihiko Sato, William W Hall, Hiroaki Kariwa, Yasuko Orba, Hirofumi Sawa, Michihito Sasaki
    Viruses 13 3 2021年02月28日 
    Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) utilizes host proteases, including a plasma membrane-associated transmembrane protease, serine 2 (TMPRSS2) to cleave and activate the virus spike protein to facilitate cellular entry. Although TMPRSS2 is a well-characterized type II transmembrane serine protease (TTSP), the role of other TTSPs on the replication of SARS-CoV-2 remains to be elucidated. Here, we have screened 12 TTSPs using human angiotensin-converting enzyme 2-expressing HEK293T (293T-ACE2) cells and Vero E6 cells and demonstrated that exogenous expression of TMPRSS11D and TMPRSS13 enhanced cellular uptake and subsequent replication of SARS-CoV-2. In addition, SARS-CoV-1 and SARS-CoV-2 share the same TTSPs in the viral entry process. Our study demonstrates the impact of host TTSPs on infection of SARS-CoV-2, which may have implications for cell and tissue tropism, for pathogenicity, and potentially for vaccine development.
  • Mai Kishimoto, Bernard M Hang'ombe, William W Hall, Yasuko Orba, Hirofumi Sawa, Michihito Sasaki
    The Journal of general virology 2021年02月03日 
    Encephalomyocarditis virus (EMCV) infects a wide range of hosts and can cause encephalitis, myocarditis, reproductive disorders and diabetes mellitus in selected mammalian species. As for humans, EMCV infection seems to occur by the contact with animals and can cause febrile illnesses in some infected patients. Here we isolated EMCV strain ZM12/14 from a natal multimammate mouse (Mastomys natalensis: M. natalensis) in Zambia. Pairwise sequence similarity of the ZM12/14 P1 region consisting of antigenic capsid proteins showed the highest similarity of nucleotide (80.7 %) and amino acid (96.2%) sequence with EMCV serotype 1 (EMCV-1). Phylogenetic analysis revealed that ZM12/14 clustered into EMCV-1 at the P1 and P3 regions but segregated from known EMCV strains at the P2 region, suggesting a unique evolutionary history. Reverse transcription PCR (RT-PCR) screening and neutralizing antibody assays for EMCV were performed using collected tissues and serum from various rodents (n=179) captured in different areas in Zambia. We detected the EMCV genome in 19 M. natalensis (19/179=10.6 %) and neutralizing antibody for EMCV in 33 M. natalensis (33/179=18.4 %). However, we did not detect either the genome or neutralizing antibody in other rodent species. High neutralizing antibody litres (≧320) were observed in both RT-PCR-negative and -positive animals. Inoculation of ZM12/14 caused asymptomatic persistent infection in BALB/c mice with high antibody titres and high viral loads in some organs, consistent with the above epidemiological results. This study is the first report of the isolation of EMCV in Zambia, suggesting that M. natalensis may play a role as a natural reservoir of infection.
  • Yasuko Orba, Keita Matsuno, Ryo Nakao, Kirill Kryukov, Yumi Saito, Fumihiko Kawamori, Ariel Loza Vega, Tokiko Watanabe, Tadashi Maemura, Michihito Sasaki, William W Hall, Roy A Hall, Juan Antonio Pereira, So Nakagawa, Hirofumi Sawa
    The Journal of general virology 2021年01月08日 
    The genus Flavivirus includes a range of mosquito-specific viruses in addition to well-known medically important arboviruses. Isolation and comprehensive genomic analyses of viruses in mosquitoes collected in Bolivia resulted in the identification of three novel flavivirus species. Psorophora flavivirus (PSFV) was isolated from Psorophora albigenu. The coding sequence of the PSFV polyprotein shares 60 % identity with that of the Aedes-associated lineage II insect-specific flavivirus (ISF), Marisma virus. Isolated PSFV replicates in both Aedes albopictus- and Aedes aegypti-derived cells, but not in mammalian Vero or BHK-21 cell lines. Two other flaviviruses, Ochlerotatus scapularis flavivirus (OSFV) and Mansonia flavivirus (MAFV), which were identified from Ochlerotatus scapularis and Mansonia titillans, respectively, group with the classical lineage I ISFs. The protein coding sequences of these viruses share only 60 and 40 % identity with the most closely related of known lineage I ISFs, including Xishuangbanna aedes flavivirus and Sabethes flavivirus, respectively. Phylogenetic analysis suggests that MAFV is clearly distinct from the groups of the current known Culicinae-associated lineage I ISFs. Interestingly, the predicted amino acid sequence of the MAFV capsid protein is approximately two times longer than that of any of the other known flaviviruses. Our results indicate that flaviviruses with distinct features can be found at the edge of the Bolivian Amazon basin at sites that are also home to dense populations of human-biting mosquitoes.
  • Edgar Simulundu, Francis Mupeta, Pascalina Chanda-Kapata, Ngonda Saasa, Katendi Changula, Walter Muleya, Simbarashe Chitanga, Miniva Mwanza, Paul Simusika, Herman Chambaro, Benjamin Mubemba, Masahiro Kajihara, Duncan Chanda, Lloyd Mulenga, Sombo Fwoloshi, Aaron Lunda Shibemba, Fred Kapaya, Paul Zulu, Kunda Musonda, Mwaka Monze, Nyambe Sinyange, Mazyanga L Mazaba, Muzala Kapin'a, Peter J Chipimo, Raymond Hamoonga, Davie Simwaba, William Ngosa, Albertina N Morales, Nkomba Kayeyi, John Tembo, Mathew Bates, Yasuko Orba, Hirofumi Sawa, Ayato Takada, King S Nalubamba, Kennedy Malama, Victor Mukonka, Alimuddin Zumla, Nathan Kapata
    International journal of infectious diseases : IJID : official publication of the International Society for Infectious Diseases 102 455 - 459 2021年01月 
    Since its first discovery in December 2019 in Wuhan, China, COVID-19, caused by the novel coronavirus SARS-CoV-2, has spread rapidly worldwide. While African countries were relatively spared initially, the initial low incidence of COVID-19 cases was not sustained for long due to continuing travel links between China, Europe and Africa. In preparation, Zambia had applied a multisectoral national epidemic disease surveillance and response system resulting in the identification of the first case within 48 h of the individual entering the country by air travel from a trip to France. Contact tracing showed that SARS-CoV-2 infection was contained within the patient's household, with no further spread to attending health care workers or community members. Phylogenomic analysis of the patient's SARS-CoV-2 strain showed that it belonged to lineage B.1.1., sharing the last common ancestor with SARS-CoV-2 strains recovered from South Africa. At the African continental level, our analysis showed that B.1 and B.1.1 lineages appear to be predominant in Africa. Whole genome sequence analysis should be part of all surveillance and case detection activities in order to monitor the origin and evolution of SARS-CoV-2 lineages across Africa.
  • Michihito Sasaki, Kentaro Uemura, Akihiko Sato, Shinsuke Toba, Takao Sanaki, Katsumi Maenaka, William W Hall, Yasuko Orba, Hirofumi Sawa
    PLoS pathogens 17 1 e1009233  2021年01月 
    The spike (S) protein of Severe Acute Respiratory Syndrome-Coronavirus-2 (SARS-CoV-2) binds to a host cell receptor which facilitates viral entry. A polybasic motif detected at the cleavage site of the S protein has been shown to broaden the cell tropism and transmissibility of the virus. Here we examine the properties of SARS-CoV-2 variants with mutations at the S protein cleavage site that undergo inefficient proteolytic cleavage. Virus variants with S gene mutations generated smaller plaques and exhibited a more limited range of cell tropism compared to the wild-type strain. These alterations were shown to result from their inability to utilize the entry pathway involving direct fusion mediated by the host type II transmembrane serine protease, TMPRSS2. Notably, viruses with S gene mutations emerged rapidly and became the dominant SARS-CoV-2 variants in TMPRSS2-deficient cells including Vero cells. Our study demonstrated that the S protein polybasic cleavage motif is a critical factor underlying SARS-CoV-2 entry and cell tropism. As such, researchers should be alert to the possibility of de novo S gene mutations emerging in tissue-culture propagated virus strains.
  • Haruaki Nobori, Kentaro Uemura, Shinsuke Toba, Takao Sanaki, Takao Shishido, William W Hall, Yasuko Orba, Hirofumi Sawa, Akihiko Sato
    Antiviral research 184 104969 - 104969 2020年12月 
    Dengue virus (DENV) infection is one of the most important infectious diseases in tropical and subtropical regions around the world. Previously, we performed an initial phenotypic screening of 7000 compounds using DENV type 2 (DENV2)-infected BHK-21 cells to identify small molecules which could inhibit virus replication. In this study, we describe two novel compounds with anti-DENV2 activity, tentatively named Compound-X and Compound-Y. Both compounds possess a quinolone skeleton, and the EC50s of Compound-X and Compound-Y against DENV2 were 3.9 μM and 9.2 μM, respectively. Based on a DENV replicon assay, it was suggested that these compounds have anti-DENV2 activity by inhibition of a step in virus replication. Furthermore, using mutational analysis we obtained compounds-resistant to DENV2 infection and identified a mutation, V130A in the NS5 methyltransferase (MTase) domain. However, these compounds did not inhibit MTase activity. In addition, incorporation of an additional NS1 N246D mutation with the NS5 V130A mutation in DENV2 resulted in recovery of viral replication and a further reduction of the sensitivity to the quinolone compounds by an unknown mechanism. Therefore further investigations are required to clarify the antiviral mechanisms of these quinolone compounds.
  • Lucky R Runtuwene, Shuichi Kawashima, Victor D Pijoh, Josef S B Tuda, Kyoko Hayashida, Junya Yamagishi, Chihiro Sugimoto, Shoko Nishiyama, Michihito Sasaki, Yasuko Orba, Hirofumi Sawa, Tomohiko Takasaki, Anthony A James, Takashi Kobayashi, Yuki Eshita
    International journal of molecular sciences 21 20 2020年10月12日 
    Efforts to determine the mosquito genes that affect dengue virus replication have identified a number of candidates that positively or negatively modify amplification in the invertebrate host. We used deep sequencing to compare the differential transcript abundances in Aedes aegypti 14 days post dengue infection to those of uninfected A. aegypti. The gene lethal(2)-essential-for-life [l(2)efl], which encodes a member of the heat shock 20 protein (HSP20) family, was upregulated following dengue virus type 2 (DENV-2) infection in vivo. The transcripts of this gene did not exhibit differential accumulation in mosquitoes exposed to insecticides or pollutants. The induction and overexpression of l(2)efl gene products using poly(I:C) resulted in decreased DENV-2 replication in the cell line. In contrast, the RNAi-mediated suppression of l(2)efl gene products resulted in enhanced DENV-2 replication, but this enhancement occurred only if multiple l(2)efl genes were suppressed. l(2)efl homologs induce the phosphorylation of eukaryotic initiation factor 2α (eIF2α) in the fruit fly Drosophila melanogaster, and we confirmed this finding in the cell line. However, the mechanism by which l(2)efl phosphorylates eIF2α remains unclear. We conclude that l(2)efl encodes a potential anti-dengue protein in the vector mosquito.
  • Christida E Wastika, Hayato Harima, Michihito Sasaki, Bernard M Hang'ombe, Yuki Eshita, Yongjin Qiu, William W Hall, Michael T Wolfinger, Hirofumi Sawa, Yasuko Orba
    Viruses 12 9 2020年09月11日 
    To monitor the arthropod-borne virus transmission in mosquitoes, we have attempted both to detect and isolate viruses from 3304 wild-caught female mosquitoes in the Livingstone (Southern Province) and Mongu (Western Province) regions in Zambia in 2017. A pan-flavivirus RT-PCR assay was performed to identify flavivirus genomes in total RNA extracted from mosquito lysates, followed by virus isolation and full genome sequence analysis using next-generation sequencing and rapid amplification of cDNA ends. We isolated a newly identified Barkedji virus (BJV Zambia) (10,899 nt) and a novel flavivirus, tentatively termed Barkedji-like virus (BJLV) (10,885 nt) from Culex spp. mosquitoes which shared 96% and 75% nucleotide identity with BJV which has been isolated in Israel, respectively. These viruses could replicate in C6/36 cells but not in mammalian and avian cell lines. In parallel, a comparative genomics screening was conducted to study evolutionary traits of the 5'- and 3'-untranslated regions (UTRs) of isolated viruses. Bioinformatic analyses of the secondary structures in the UTRs of both viruses revealed that the 5'-UTRs exhibit canonical stem-loop structures, while the 3'-UTRs contain structural homologs to exoribonuclease-resistant RNAs (xrRNAs), SL-III, dumbbell, and terminal stem-loop (3'SL) structures. The function of predicted xrRNA structures to stop RNA degradation by Xrn1 exoribonuclease was further proved by the in vitro Xrn1 resistance assay.
  • Herman M Chambaro, Michihito Sasaki, Edgar Simulundu, Isaac Silwamba, Yona Sinkala, Gabriel Gonzalez, David Squarre, Paul Fandamu, Caesar H Lubaba, Musso Munyeme, Alikhadio Maseko, Choopa Chimvwele, Liywalii Mataa, Lynnfield E Mooya, Andrew N Mukubesa, Hayato Harima, Kenny L Samui, Hetron M Munang'andu, Martin Simuunza, King S Nalubamba, Yongjin Qiu, Michael J Carr, William W Hall, Yuki Eshita, Hirofumi Sawa, Yasuko Orba
    Viruses 12 9 2020年08月31日 
    Bluetongue (BT) is an arthropod-borne viral disease of ruminants with serious trade and socio-economic implications. Although the disease has been reported in a number of countries in sub-Saharan Africa, there is currently no information on circulating serotypes and disease distribution in Zambia. Following surveillance for BT in domestic and wild ruminants in Zambia, BT virus (BTV) nucleic acid and antibodies were detected in eight of the 10 provinces of the country. About 40% (87/215) of pooled blood samples from cattle and goats were positive for BTV nucleic acid, while one hartebeest pool (1/43) was positive among wildlife samples. Sequence analysis of segment 2 revealed presence of serotypes 3, 5, 7, 12 and 15, with five nucleotypes (B, E, F, G and J) being identified. Segment 10 phylogeny showed Zambian BTV sequences clustering with Western topotype strains from South Africa, intimating likely transboundary spread of BTV in Southern Africa. Interestingly, two Zambian viruses and one isolate from Israel formed a novel clade, which we designated as Western topotype 4. The high seroprevalence (96.2%) in cattle from Lusaka and Central provinces and co-circulation of multiple serotypes showed that BT is widespread, underscoring the need for prevention and control strategies.
  • Hayato Harima, Michihito Sasaki, Masahiro Kajihara, Gabriel Gonzalez, Edgar Simulundu, Eugene C Bwalya, Yongjin Qiu, Kosuke Okuya, Mao Isono, Yasuko Orba, Ayato Takada, Bernard M Hang'ombe, Aaron S Mweene, Hirofumi Sawa
    The Journal of general virology 2020年07月24日 [査読有り][通常論文]
    Mammalian orthoreovirus (MRV) has been identified in humans, livestock and wild animals; this wide host range allows individual MRV to transmit into multiple species. Although several interspecies transmission and genetic reassortment events of MRVs among humans, livestock and wildlife have been reported, the genetic diversity and geographic distribution of MRVs in Africa are poorly understood. In this study, we report the first isolation and characterization of MRVs circulating in a pig population in Zambia. In our screening, MRV genomes were detected in 19.7 % (29/147) of faecal samples collected from pigs by reverse transcription PCR. Three infectious MRV strains (MRV-85, MRV-96 and MRV-117) were successfully isolated, and their complete genomes were sequenced. Recombination analyses based on the complete genome sequences of the isolated MRVs demonstrated that MRV-96 shared the S3 segment with a different MRV isolated from bats, and that the L1 and M3 segments of MRV-117 originated from bat and human MRVs, respectively. Our results suggest that the isolated MRVs emerged through genetic reassortment events with interspecies transmission. Given the lack of information regarding MRVs in Africa, further surveillance of MRVs circulating among humans, domestic animals and wildlife is required to assess potential risk for humans and animals.
  • Shiho Torii, Yasuko Orba, Michihito Sasaki, Koshiro Tabata, Yuji Wada, Michael Carr, Jody Hobson-Peters, Roy A Hall, Ayato Takada, Takasuke Fukuhara, Yoshiharu Matsuura, William W Hall, Hirofumi Sawa
    The Journal of biological chemistry 295 23 7941 - 7957 2020年06月05日 [査読有り][通常論文]
    Chikungunya fever is a re-emerging zoonotic disease caused by chikungunya virus (CHIKV), a member of the Alphavirus genus in the Togaviridae family. Only a few studies have reported on the host factors required for intracellular CHIKV trafficking. Here, we conducted an imaging-based siRNA screen to identify human host factors for intracellular trafficking that are involved in CHIKV infection, examined their interactions with CHIKV proteins, and investigated the contributions of these proteins to CHIKV infection. The results of the siRNA screen revealed that host endosomal sorting complexes required for transport (ESCRT) proteins are recruited during CHIKV infection. Co-immunoprecipitation analyses revealed that both structural and nonstructural CHIKV proteins interact with hepatocyte growth factor-regulated tyrosine kinase substrate (HGS), a component of the ESCRT-0 complex. We also observed that HGS co-localizes with the E2 protein of CHIKV and with dsRNA, a marker of the replicated CHIKV genome. Results from gene knockdown analyses indicated that, along with other ESCRT factors, HGS facilitates both genome replication and post-translational steps during CHIKV infection. Moreover, we show that ESCRT factors are also required for infections with other alphaviruses. We conclude that during CHIKV infection, several ESCRT factors are recruited via HGS and are involved in viral genome replication and post-translational processing of viral proteins.
  • Herman M Chambaro, Michihito Sasaki, Yona Sinkala, Gabriel Gonzalez, David Squarre, Paul Fandamu, Caesar Lubaba, Liywalii Mataa, Misheck Shawa, Kabemba E Mwape, Sarah Gabriël, Mwelwa Chembensofu, Michael J Carr, William W Hall, Yongjin Qiu, Masahiro Kajihara, Ayato Takada, Yasuko Orba, Edgar Simulundu, Hirofumi Sawa
    Transboundary and emerging diseases 2020年05月20日 [査読有り][通常論文]
    African swine fever (ASF) causes persistent outbreaks in endemic and non-endemic regions in Zambia. However, the epidemiology of the disease is poorly understood, particularly during the inter-epidemic periods. We conducted surveillance for ASF in asymptomatic domestic pigs and soft ticks in selected Zambian provinces. While serum samples (n = 1,134) were collected from crossbred pigs from all study sites between 2014 and 2017, whole blood (n = 300) was collected from both crossbred and indigenous pigs in Eastern Province (EP) in 2017. Soft ticks were collected from Mosi-oa-Tunya National Park in Southern Province (SP) in 2019. Sera were screened for antibodies against ASF by ELISA while genome detection in whole blood and soft ticks was conducted by PCR. Ticks were identified morphologically and by phylogenetic analysis of the 16S rRNA gene. Seroprevalence was highest in EP (50.9%, 95% CI [47.0-54.9]) compared to significantly lower rates in SP (2.9%, 95% CI [1.6-5.1]). No antibodies to ASFV were detected in Lusaka Province. In EP, the prevalence of ASFV genome was 11.7% (35/300), significantly higher (OR = 6.2, 95% CI [2.4-16.6]) in indigenous pigs compared to crossbred pigs. The pooled prevalence of ASFV genome in ticks was 11.0%, 95% CI [8.5-13.9]. Free-range husbandry system was the only factor that was significantly associated with seropositive (p < .0001, OR = 39.3) and PCR-positive results (p < .001, OR = 5.7). Phylogenetically, based on the p72 gene, ASFV from Ornithodoros moubata ticks detected in this study belonged to genotype I, but they separated into two distinct clusters. Besides confirming ASF endemicity in EP and the presence of ASFV-infected ticks in SP, these results provide evidence for exposure of domestic pigs to ASFV in non-endemic regions during the inter-epidemic period.
  • Hayato Harima, Michihito Sasaki, Masahiro Kajihara, Akina Mori-Kajihara, Bernard M Hang'ombe, Katendi Changula, Yasuko Orba, Hirohito Ogawa, Martin Simuunza, Reiko Yoshida, Aaron Mweene, Ayato Takada, Hirofumi Sawa
    The Journal of veterinary medical science 82 2 162 - 167 2020年02月04日 [査読有り][通常論文]
    Orthoreoviruses have been indentified in several mammals, however, there is no information about orthoreoviruses in shrews. In this study, we screened wild animals in Zambia, including shrews, rodents, and bats for the detection of orthoreoviruses. Two orthoreovirus RNA genomes were detected from a shrew intestinal-contents (1/24) and a bat colon (1/96) sample by reverse-transcription (RT)-PCR targeting the RNA-dependent RNA polymerase gene of orthoreoviruses. Phylogenetic analyses revealed that each of the identified orthoreoviruses formed a distinct branch among members of the Orthoreovirus genus. This is the first report that shrews are susceptible to orthoreovirus infection. Our results suggest the existence of undiscovered orthoreoviruses in shrews and provide important information about the genetic diversity of orthoreoviruses.
  • Shintaro Kobayashi, Kentaro Yoshii, Wallaya Phongphaew, Memi Muto, Minato Hirano, Yasuko Orba, Hirofumi Sawa, Hiroaki Kariwa
    PLoS pathogens 16 1 e1008238  2020年01月 [査読有り][通常論文]
    West Nile virus (WNV) belongs to the Flaviviridae family and has emerged as a significant cause of viral encephalitis in birds and animals including humans. WNV replication directly induces neuronal injury, followed by neuronal cell death. We previously showed that accumulation of ubiquitinated protein aggregates was involved in neuronal cell death in the WNV-infected mouse brain. In this study, we attempted to elucidate the mechanisms of the accumulation of protein aggregates in the WNV-infected cells. To identify the viral factor inducing the accumulation of ubiquitinated proteins, intracellular accumulation of ubiquitinated proteins was examined in the cells expressing the viral protein. Expression of capsid (C) protein induced the accumulation, while mutations at residues L51 and A52 in C protein abrogated the accumulation. Wild-type (WT) or mutant WNV in which mutations were introduced into the residues was inoculated into human neuroblastoma cells. The expression levels of LC3-II, an autophagy-related protein, and AMP-activated protein kinase (AMPK), an autophagy inducer, were reduced in the cells infected with WT WNV, while the reduction was not observed in the cells infected with WNV with the mutations in C protein. Similarly, ubiquitination and degradation of AMPK were only observed in the cells infected with WT WNV. In the cells expressing C protein, AMPK was co-precipitated with C protein and mutations in L51 and A52 reduced the interaction. Although the viral replication was not affected, the accumulation of ubiquitinated proteins in brain and neurological symptoms were attenuated in the mouse inoculated with WNV with the mutations in C protein as compared with that with WT WNV. Taken together, ubiquitination and degradation of AMPK by C protein resulted in the inhibition of autophagy and the accumulation of protein aggregates, which contributes to the development of neurological disease.
  • Carr M, Gonzalez G, Martinelli A, Wastika CE, Ito K, Orba Y, Sasaki M, Hall WW, Sawa H
    Virus genes 55 5 630 - 642 2019年10月 [査読有り][通常論文]
  • Satoshi Tanikawa, Mishie Tanino, Lei Wang, Marin Ishikawa, Masaya Miyazaki, Masumi Tsuda, Yasuko Orba, Hirofumi Sawa, Kotarou Matoba, Nishio Nakamura, Kazuo Nagashima, William W Hall, Shinya Tanaka
    Neuropathology : official journal of the Japanese Society of Neuropathology 39 5 374 - 377 2019年10月 [査読有り][通常論文]
    Dropped head syndrome (DHS) has been rarely observed in amyotrophic lateral sclerosis (ALS), and the neuropathological findings of this condition have almost never been described. The identification of transactivation response DNA-binding protein 43 kDa (TDP-43), which binds to RNA/DNA has provided a new method for studying ALS and frontotemporal lobar degeneration (FTLD). Post-mortem examination of an adult sudden death case of a 71-year-old patient who complained of DHS exhibited severe loss of anterior motor neurons in the cervical cord (C4-6). Loss of nerve fibers of the anterior roots was striking compared with posterior roots, together with marked neurogenic atrophy of posterior muscles semispinalis cervicis. Bunina bodies were found in large neurons of Betz giant cells, but not in the motor neurons of spinal cords, or neurons of bulbar regions. Phosphorylated TDP-43 (p-TDP-43)-positive structures were detected in the residual neurons of the cervical, thoracic and lumber cords, hypoglossal nucleus, cerebellar dentate nucleus and parahippocampal cortex, together with ubiquitin-positive inclusions. Phosphorylated Tau positive structures in neuronal cytoplasm were found in the amygdala, entorhinal cortex and parahippocampal cortex, some of which co-expressed p-TDP-43. The medial zone of cervical cords may be the first onset site, and that is the cause of head drop in the early stage of ALS. In spite of detailed examination, the direct cause of sudden death was not verified. This autopsy report revealed the relation of DHS which is a rare clinical manifestation of ALS, and neuropathological findings.
  • Christida E Wastika, Michihito Sasaki, Kentaro Yoshii, Paulina D Anindita, Bernard M Hang'ombe, Aaron S Mweene, Shintaro Kobayashi, Hiroaki Kariwa, Michael J Carr, William W Hall, Yuki Eshita, Yasuko Orba, Hirofumi Sawa
    Archives of virology 164 8 2165 - 2170 2019年08月 [査読有り][通常論文]
    Zika virus (ZIKV) circulation occurs between non-human primates (NHPs) in a sylvatic transmission cycle. To investigate evidence of flavivirus infection in NHPs in Zambia, we performed a plaque reduction neutralization test (PRNT) to quantify neutralizing antibodies. PRNT revealed that sera from NHPs (African green monkeys and baboons) exhibited neutralizing activity against ZIKV (34.4%; 33/96), whereas a PRNT for yellow fever virus using NHP sera showed no neutralization activity. ZIKV genomic RNA was not detected in splenic tissues from NHPs, suggesting that the presence of anti-ZIKV neutralizing antibodies represented resolved infections. Our evidence suggests that ZIKV is maintained in NHP reservoirs in Zambia.
  • Masahiro Kajihara, Bernard M Hang'ombe, Katendi Changula, Hayato Harima, Mao Isono, Kosuke Okuya, Reiko Yoshida, Akina Mori-Kajihara, Yoshiki Eto, Yasuko Orba, Hirohito Ogawa, Yongjin Qiu, Hirofumi Sawa, Edgar Simulundu, Daniel Mwizabi, Musso Munyeme, David Squarre, Victor Mukonka, Aaron Mweene, Ayato Takada
    Emerging infectious diseases 25 8 1577 - 1580 2019年08月 [査読有り][通常論文]
    We detected Marburg virus genome in Egyptian fruit bats (Rousettus aegyptiacus) captured in Zambia in September 2018. The virus was closely related phylogenetically to the viruses that previously caused Marburg outbreaks in the Democratic Republic of the Congo. This finding demonstrates that Zambia is at risk for Marburg virus disease.
  • Anindita PD, Sasaki M, Gonzalez G, Phongphaew W, Carr M, Hang'ombe BM, Mweene AS, Ito K, Orba Y, Sawa H
    Scientific reports 9 1 8502  2019年06月 [査読有り][通常論文]
  • Kyoko Hayashida, Yasuko Orba, Patricia C Sequeira, Chihiro Sugimoto, William W Hall, Yuki Eshita, Yutaka Suzuki, Lucky Runtuwene, Patricia Brasil, Guilherme Calvet, Cintia D S Rodrigues, Carolina C Dos Santos, Maria A M Mares-Guia, Junya Yamagishi, Ana M B de Filippis, Hirofumi Sawa
    PLoS neglected tropical diseases 13 6 e0007480  2019年06月 [査読有り][通常論文]
    Detection and sequencing of chikungunya virus (CHIKV) genome was performed using a combination of a modified reverse transcription loop-mediated isothermal amplification (RT-LAMP) method and a MinION sequencer. We developed the protocol for drying all the reagents for the RT-LAMP in a single reaction tube. Using this system, the CHIKV genome was effectively amplified under isothermal conditions, and used as a template for MinION sequencing with a laptop computer. Our in-house RT-LAMP method and MinION sequencing system were also validated with RNAs and serum samples from recent outbreaks of CHIKV patients in Brazil. The obtained sequence data confirmed the CHIKV outbreaks and identified the genotype. In summary, our established inexpensive on-site genome detection and sequencing system is applicable for both diagnosis of CHIKV infected patients and genotyping of the CHIKV virus in future outbreak in remote areas.
  • Anindita PD, Sasaki M, Gonzalez G, Phongphaew W, Carr M, Hang'ombe BM, Mweene AS, Ito K, Orba Y, Sawa H
    Scientific reports 9 1 5045  2019年04月 [査読有り][通常論文]
  • Lin Sun, Naoko Kono, Hiroyuki Toh, Hanbing Xue, Kaori Sano, Tadaki Suzuki, Akira Ainai, Yasuko Orba, Junya Yamagishi, Hideki Hasegawa, Yoshimasa Takahashi, Shigeyuki Itamura, Kazuo Ohnishi
    Journal of visualized experiments : JoVE 145 2019年03月15日 [査読有り][通常論文]
    The immense adaptability of antigen recognition by antibodies is the basis of the acquired immune system. Despite our understanding of the molecular mechanisms underlying the production of the vast repertoire of antibodies by the acquired immune systems, it has not yet been possible to arrive at a global view of a complete antibody repertoire. In particular, B cell repertoires have been regarded as a black box because of their astronomical number of antibody clones. However, next-generation sequencing technologies are enabling breakthroughs to increase our understanding of the B cell repertoire. In this report, we describe a simple and efficient method to visualize and analyze whole individual mouse and human antibody repertoires. From the immune organs, representatively from spleen in mice and peripheral blood mononuclear cells in humans, total RNA was prepared, reverse transcribed, and amplified using the 5'-RACE method. Using a universal forward primer and antisense primers for the antibody class-specific constant domains, antibody mRNAs were uniformly amplified in proportions reflecting their frequencies in the antibody populations. The amplicons were sequenced by next-generation sequencing (NGS), yielding more than 105 antibody sequences per immunological sample. We describe the protocols for antibody sequence analyses including V(D)J-gene-segment annotation, a bird's-eye view of the antibody repertoire, and our computational methods.
  • Ishida Y, Tsuda M, Sawamura Y, Fujii K, Murai H, Horiuchi N, Orba Y, Sawa H, Hall WW, Nagashima K, Tanaka S
    Pathology international 68 12 694 - 699 2018年12月 [査読有り][通常論文]
  • Michihito Sasaki, Masahiro Kajihara, Katendi Changula, Akina Mori-Kajihara, Hirohito Ogawa, Bernard M. Hang'ombe, Aaron S. Mweene, Martin Simuunza, Reiko Yoshida, Michael Carr, Yasuko Orba, Ayato Takada, Hirofumi Sawa
    Infection, Genetics and Evolution 63 104 - 109 2018年09月01日 [査読有り][通常論文]
    Group A rotavirus (RVA) is a major cause of diarrhea in children worldwide. Although RVA infects many animals, little is known about RVA in bats. The present study investigated the genetic diversity of RVA in Zambian bats. We identified RVA from two straw-colored fruit bats (Eidolon helvum) and an Egyptian fruit bat (Rousettus aegyptiacus), and analyzed the genome sequences of these strains. Genome segments of the RVA strains from Zambian E. helvum showed 97%–99% nucleotide sequence identity with those of other RVA strains from E. helvum in Cameroon, which is 2800 km from the sampling locations. These findings suggest that migratory straw-colored fruit bat species, distributed across sub-Saharan Africa, have the potential to disseminate RVA across long distances. By contrast, the RVA strain from Zambian R. aegyptiacus carried highly divergent NSP2 and NSP4 genes, leading us to propose novel genotypes N21 and E27, respectively. Notably, this RVA strain also shared the same genotype for VP6 and NSP3 with the RVA strains from Zambian E. helvum, suggesting interspecies transmission and genetic reassortment may have occurred between these two bat species in the past. Our study has important implications for RVA dispersal in bat populations, and expands our knowledge of the ecology, diversity and evolutionary relationships of RVA.
  • Keita Matsuno, Noriyuki Nonoue, Ayako Noda, Nodoka Kasajima, Keita Noguchi, Ai Takano, Hiroshi Shimoda, Yasuko Orba, Mieko Muramatsu, Yoshihiro Sakoda, Ayato Takada, Shinji Minami, Yumi Une, Shigeru Morikawa, Ken Maeda
    Emerging infectious diseases 24 9 1726 - 1729 2018年09月 [査読有り][通常論文]
    Two captive cheetahs from a zoo in Japan died of a severe fever with thrombocytopenia syndrome-like illness. Severe fever with thrombocytopenia syndrome virus, an endemic tickborne phlebovirus, was detected systemically with secretion of infectious viruses into the saliva. These cases highlight the risk for exposure of captive animals to endemic arthropodborne pathogens.
  • Orba Y, Hang'ombe BM, Mweene AS, Wada Y, Anindita PD, Phongphaew W, Qiu Y, Kajihara M, Mori-Kajihara A, Eto Y, Sasaki M, Hall WW, Eshita Y, Sawa H
    Transboundary and emerging diseases 65 4 933 - 938 2018年08月 [査読有り][通常論文]
  • Haruaki Nobori, Shinsuke Toba, Ryu Yoshida, William W. Hall, Yasuko Orba, Hirofumi Sawa, Akihiko Sato
    Antiviral Research 155 60 - 66 2018年07月01日 [査読有り][通常論文]
  • Fujiki J, Nobori H, Sato A, Sasaki M, Carr M, Hall WW, Orba Y, Sawa H
    Japanese journal of infectious diseases 71 6 448 - 454 2018年07月 [査読有り][通常論文]
  • Anindita PD, Sasaki M, Okada K, Ito N, Sugiyama M, Saito-Tarashima N, Minakawa N, Shuto S, Otsuguro S, Ichikawa S, Matsuda A, Maenaka K, Orba Y, Sawa H
    Antiviral research 154 1 - 9 2018年06月 [査読有り][通常論文]
  • Shiho Torii, Yasuko Orba, Bernard M Hang'ombe, Aaron S Mweene, Yuji Wada, Paulina D Anindita, Wallaya Phongphaew, Yongjin Qiu, Masahiro Kajihara, Akina Mori-Kajihara, Yoshiki Eto, Hayato Harima, Michihito Sasaki, Michael Carr, William W Hall, Yuki Eshita, Takashi Abe, Hirofumi Sawa
    Virus research 250 31 - 36 2018年05月02日 [査読有り][通常論文]
    Mosquito-borne alphaviruses are disseminated globally and cause febrile illness in humans and animals. Since the prevalence and diversity of alphaviruses has not been previously investigated in Zambia, reverse transcription PCR was employed as a broad-spectrum approach for the detection of alphaviruses in mosquitoes. From 552 mosquito pools, a novel alphavirus, tentatively named Mwinilunga alphavirus (MWAV), was discovered from a single Culex quinquefasciatus mosquito pool. The full genome of MWAV was subsequently determined, and pairwise comparisons demonstrated that MWAV represented a new alphavirus species. Phylogenetic analyses and a linear discriminant analysis based on the dinucleotide ratios in various virus sequences indicated that MWAV is related to a mosquito-specific alphavirus distinct from other known mosquito-borne alphaviruses due to its inability to replicate in vertebrate cell lines. Further analyses of these novel alphaviruses will help to facilitate a greater understanding of the molecular determinants of host range restriction and the evolutionary relationships of alphaviruses.
  • Sasaki M, Anindita PD, Ito N, Sugiyama M, Carr M, Fukuhara H, Ose T, Maenaka K, Takada A, Hall WW, Orba Y, Sawa H
    The Journal of infectious diseases 217 11 1740 - 1749 2018年05月 [査読有り][通常論文]
  • Yuji Wada, Michihito Sasaki, Agus Setiyono, Ekowati Handharyani, Ibenu Rahmadani, Siswatiana Taha, Sri Adiani, Munira Latief, Zainal Abidin Kholilullah, Mawar Subangkit, Shintaro Kobayashi, Ichiro Nakamura, Takashi Kimura, Yasuko Orba, Hirofumi Sawa
    Journal of Medical Microbiology 67 3 415 - 422 2018年03月01日 [査読有り][通常論文]
    Bats are an important natural reservoir of zoonotic viral pathogens. We previously isolated an alphaherpesvirus in fruit bats in Indonesia, and here establish the presence of viruses belonging to other taxa of the family Herpesviridae. We screened the same fruit bat population with pan-herpesvirus PCR and discovered 68 sequences of novel gammaherpesvirus, designated ‘megabat gammaherpesvirus’ (MgGHV). A phylogenetic analysis of approximately 3.4 kbp of continuous MgGHV sequences encompassing the glycoprotein B gene and DNA polymerase gene revealed that the MgGHV sequences are distinct from those of other reported gammaherpesviruses. Further analysis suggested the existence of co-infections of herpesviruses in Indonesian fruit bats. Our findings extend our understanding of the infectious cycles of herpesviruses in bats in Indonesia and the phylogenetic diversity of the gammaherpesviruses.
  • Taiyu Tazaki, Koshiro Tabata, Akira Ainai, Yuki Ohara, Shintaro Kobayashi, Takafumi Ninomiya, Yasuko Orba, Hideyuki Mitomo, Tetsuo Nakano, Hideki Hasegawa, Kuniharu Ijiro, Hirofumi Sawa, Tadaki Suzuki, Kenichi Niikura
    RSC Advances 8 30 16527 - 16536 2018年 [査読有り][通常論文]
    Intranasal inactivated influenza vaccines can elicit mucosal immune responses that protect against virus infection. For the development of intranasal inactivated influenza vaccines, effective adjuvants inducing minimal adverse reactions are required. Generally, however, lower toxicity adjuvants have lower adjuvanticity. In this research, we fabricated nanoparticle-based adjuvants to enhance its adjuvanticity. Herein, we focused on low-molecular-weight polyinosinic-polycytidylic acid, referred to as uPIC(40:400), as a weak and less toxic RNA adjuvant. We conjugated uPIC(40:400) with different shaped gold nanoparticles (AuNPs) electrostatically. Conjugation with gold nanorods, but not spherical AuNPs, markedly enhanced the adjuvanticity of uPIC(40:400), leading to the suppression of viral infection in mice. Notably, conjugation with gold nanorods did not increase the inflammatory cytokine production in dendritic cells. These data indicated that gold nanorods can provide a good platform for enhancing the weak adjuvanticity of uPIC(40:400) while maintaining low inflammatory cytokine production toward the development of intranasal inactivated influenza vaccines.
  • Michihito Sasaki, Paulina D. Anindita, Wallaya Phongphaew, Michael Carr, Shintaro Kobayashi, Yasuko Orba, Hirofumi Sawa
    VIRUS RESEARCH 243 69 - 74 2018年01月 [査読有り][通常論文]
    Subviral particles (SVPs) self-assemble and are released from cells transfected with expression plasmids encoding flavivirus structural proteins. Flavivirus-like particles (VLPs), consisting of flavivirus structural proteins and a subgenomic replicon, can enter cells and cause single-round infections. Neither SVPs or VLPs possess complete viral RNA genomes, therefore are replication-incompetent systems; however, they retain the capacity to fuse and bud from target cells and follow the same maturation process as whole virions. SVPs and VLPs have been previously employed in studies analyzing entry and release steps of viral life cycles. In this study, we have developed quantitative methods for the detection of cellular entry and release of SVPs and VLPs by applying a luciferase complementation assay based on the high affinity interaction between the split NanoLuc luciferase protein, LgBiT and the small peptide, HiBiT. We introduced HiBiT into the structural protein of West Nile virus and generated SVPs and VLPs harboring HiBiT (SVP-HiBiT and VLP-HiBiT, respectively). As SVP-HiBiT emitted strong luminescence upon exposure to LgBiT and its substrate, the nascently budded SVP-HiBiT in the supernatant was readily quantified by luminometry. Similarly, the cellular entry of VLP-HiBiT generated luminescence when VLP-HiBiT was infected into LgBiT-expressing cells. These methods utilizing SVP-HiBiT and VLP-HiBiT will facilitate research into life cycles of flaviviruses, including WNV.
  • Michael Carr, Gabriel Gonzalez, Michihito Sasaki, Serena E. Dool, Kimihito Ito, Akihiro Ishii, Bernard M. Hang'ombe, Aaron S. Mweene, Emma C. Teeling, William W. Hall, Yasuko Orba, Hirofumi Sawa
    JOURNAL OF GENERAL VIROLOGY 98 11 2771 - 2785 2017年11月 [査読有り][通常論文]
    Polyomaviruses (PyVs) are considered to be highly host-specific in different mammalian species, with no well-supported evidence for host-switching events. We examined the species diversity and host specificity of PyVs in horseshoe bats (Rhinolophus spp.), a broadly distributed and highly speciose mammalian genus. We annotated six PyV genomes, comprising four new PyV species, based on pairwise identity within the large T antigen (LTAg) coding region. Phylogenetic comparisons revealed two instances of highly related PyV species, one in each of the Alphapolyomavirus and Betapolyomavirus genera, present in different horseshoe bat host species (Rhinolophus blasii and R. simulator), suggestive of short-range host-switching events. The two pairs of Rhinolophus PyVs in different horseshoe bat host species were 99.9 and 88.8% identical with each other over their respective LTAg coding sequences and thus constitute the same virus species. To corroborate the species identification of the bat hosts, we analysed mitochondrial cytb and a large nuclear intron dataset derived from six independent and neutrally evolving loci for bat taxa of interest. Bayesian estimates of the ages of the most recent common ancestors suggested that the near-identical and more distantly related PyV species diverged approximately 9.1 E4 (5E3-2.8E5) and 9.9E6 (4E6-18E6) years before the present, respectively, in contrast to the divergence times of the bat host species: 12.4E6 (10.4E6-15.4E6). Our findings provide evidence that short-range host-switching of PyVs is possible in horseshoe bats, suggesting that PyV transmission between closely related mammalian species can occur.
  • Youhei Takagi, Kouhei Matsui, Haruaki Nobori, Haruka Maeda, Akihiko Sato, Takeshi Kurosu, Yasuko Orba, Hirofumi Sawa, Kazunari Hattori, Kenichi Higashino, Yoshito Numata, Yutaka Yoshida
    BIOORGANIC & MEDICINAL CHEMISTRY LETTERS 27 15 3586 - 3590 2017年08月 [査読有り][通常論文]
    NS2B-NS3 protease is an essential enzyme for the replication of dengue virus (DENV), which continues to be a serious threat to worldwide public health. We designed and synthesized a series of cyclic peptides mimicking the substrates of this enzyme, and assayed their activity against the DENV-2 NS2B-NS3 protease. The introduction of aromatic residues at the appropriate positions and conformational restriction generated the most promising cyclic peptide with an IC50 of 0.95 mu M against NS2B-NS3 protease. Cyclic peptides with proper positioning of additional arginines and aromatic residues exhibited antiviral activity against DENV. Furthermore, replacing the C-terminal amide bond of the polybasic amino acid sequence with an amino methylene moiety stabilized the cyclic peptides against hydrolysis by NS2B-NS3 protease, while maintaining their enzyme inhibitory activity and antiviral activity. (C) 2017 Elsevier Ltd. All rights reserved.
  • Yuji Wada, Yasuko Orba, Michihito Sasaki, Shintaro Kobayashi, Michael J. Carr, Haruaki Nobori, Akihiko Sato, William W. Hall, Hirofumi Sawa
    VIROLOGY 505 102 - 112 2017年05月 [査読有り][通常論文]
    Chikungunya fever (CHIKF) is caused by chikungunya virus (CHIKV) infection which is a re-emerging mosquito-borne zoonosis. At present, there are no approved therapeutics for CHIKF. Herein, we have investigated candidate compounds which can inhibit CHIKV infection. Screening of chemical compound libraries were performed and one candidate, a benzimidazole-related compound designated Compound-A was found to inhibit infection by several CHIKV strains and a Sindbis virus strain at nanomolar concentrations. To investigate the inhibitory mechanism of action, a Compound-A resistant CHIKV (res-CHIKV) was isolated and a key mutation associated with resistance was identified by reverse-genetic recombinant CHIICVs containing amino acid substitutions present in res-CHIKV. These results demonstrated that the target site of Compound-A was the M2295 residue in the nonstructural protein 4 (nsP4), which is located in one of the functional domains of RNA-dependent RNA-polymerase (RdRp). We also confirmed that Compound-A inhibits RdRp function of CHIKV by using CHIKV replicons.
  • Michael Carr, Gabriel Gonzalez, Michihito Sasaki, Kimihito Ito, Akihiro Ishii, Bernard M. Hang'ombe, Aaron S. Mweene, Yasuko Orba, Hirofumi Sawa
    JOURNAL OF GENERAL VIROLOGY 98 4 726 - 738 2017年04月 [査読有り][通常論文]
    Bat species represent natural reservoirs for a number of high-consequence human pathogens. The present study investigated the diversity of polyomaviruses (PyVs) in Zambian insectivorous and fruit bat species. We describe the complete genomes from four newly proposed African bat PyV species employing the recently recommended criteria provided by the Polyomaviridae Study Group of the International Committee on Taxonomy of Viruses. A comprehensive phylogenetic and recombination analysis was performed to determine genetic relationships and the distribution of recombination events in PyV from mammalian and avian species. The novel species of PyV from Zambian bats segregated with members of the genera Alphapolyomavirus and Betapolyomavirus, forming monophyletic clades with bat and non-human primate PyVs. Miniopterus schreibersii polyomavirus 1 and 2 segregated in a clade with South American bat PyV species, Old World monkey and chimpanzee PyVs and Human polyomavirus 13 (New Jersey PyV). Interestingly, the newly described Egyptian fruit bat PyV, tentatively named Rousettus aegyptiacus polyomavirus 1, had the highest nucleotide sequence identity to species of PyV from Indonesian fruit bats, and Rhinolophus hildebrandtii polyomavirus 1 was most closely related to New World monkey PyVs. The distribution of recombination events in PyV genomes was non-random: recombination boundaries existed in the intergene region between VP1 and LTAg and also at the 3' end of VP2/3 in the structural genes, whereas infrequent recombination was present within the LTAg gene. These findings indicate that recombination within the LTAg gene has been negatively selected against during polyomaviral evolution and support the recent proposal for taxonomic classification based on LTAg to define novel PyV species.
  • Michael Carr, Akira Kawaguchi, Michihito Sasaki, Gabriel Gonzalez, Kimihito Ito, Yuka Thomas, Bernard M. Hang'ombe, Aaron S. Mweene, Guoyan Zhao, David Wang, Yasuko Orba, Akihiro Ishii, Hirofumi Sawa
    ARCHIVES OF VIROLOGY 162 2 543 - 548 2017年02月 [査読有り][通常論文]
    To investigate the diversity of simian immunodeficiency virus (SIV) among nonhuman primates (NHPs) in Zambia, next-generation sequencing was performed to determine the complete genome sequence of a novel SIV recovered by co-culturing African green monkey (AGM) peripheral blood lymphocytes with human CD4(+) T-cell lines. We report the first described SIV (SIVagmMAL-ZMB) from a malbrouck (Chlorocebus cynosuros). SIVagmMAL-ZMB was detected by real-time PCR analysis of splenic RNA in 3.2% (3/94) of AGMs and was undetectable in baboons (0/105). SIVagmMAL-ZMB possessed < 80% nucleotide sequence identity to known SIV isolates and was located basally to vervet monkey SIV strains in all phylogenies.
  • Wallaya Phongphaew, Shintaro Kobayashi, Michihito Sasaki, Michael Carr, William W. Hall, Yasuko Orba, Hirofumi Sawa
    VIRUS RESEARCH 228 114 - 123 2017年01月 [査読有り][通常論文]
    Valosin-containing protein (VCP) is classified as a member of the type II AAA(+) ATPase protein family. VCP functions in several cellular processes, including protein degradation, membrane fusion, vesicular trafficking and disassembly of stress granules. Moreover, VCP is considered to play a role in the replication of several viruses, albeit through different mechanisms. In the present study, we have investigated the role of VCP in West Nile virus (WNV) infection. Endogenous VCP expression was inhibited using either VCP inhibitors or by siRNA knockdown. It could be shown that the inhibition of endogenous VCP expression significantly inhibited WNV infection. The entry assay revealed that silencing of endogenous VCP caused a significant reduction in the expression levels of WNV-RNA compared to control siRNA-treated cells. This indicates that VCP may play a role in early steps either the binding or entry steps of the WNV life cycle. Using WNV virus like particles and WNV-DNA-based replicon, it could be demonstrated that perturbation of VCP expression decreased levels of newly synthesized WNV genomic RNA. These findings suggest that VCP is involved in early steps and during genome replication of the WNV life cycle. (C) 2016 Elsevier B.V. All rights reserved.
  • Keita Matsuno, Yasuko Orba, Kimberly Maede-White, Dana Scott, Friederike Feldmann, Mifang Liang, Hideki Ebihara
    FRONTIERS IN MICROBIOLOGY 8 104  2017年01月 [査読有り][通常論文]
    The pathogenesis of clinical manifestations caused by newly emerging tick-borne phleboviruses [i.e., Severe fever with thrombocytopenia syndrome virus (SFTSV) and Heartland virus (HRTV)], such as severe thrombocytopenia and lymphocytopenia, are not yet fully understood. In the present study, to establish an animal model mimicking the profile of fatal human cases, we examined the susceptibilities of adult mice from 12 strains, aged mice from two strains, and cynomolgus macaques to SFTSV and/or HRTV infections. However, none of these immunocompetent animals developed lethal diseases after infection with SFTSV or HRTV. Thus, we tested a lethal animal model of SFTSV infection using interferon-alpha/beta receptor knock-out (IFNAR(-/-)) mice to identify the target cell(s) of virus infection, as well as lesions that are potentially associated with hematological changes. IbaI-positive macrophages and Pax5-positive immature B cells overlapped with SFTSV-positive cells in the spleen and lymph nodes of IFNAR(-/-) mice, and IbaI- SFTSV-double positive cells were also observed in the liver and kidney, thereby suggesting crucial roles for macrophages in the pathogenesis of SFTSV infection in mice. In the mandibular lymph nodes and spleens of infected mice, we observed extensive necrosis comprising B220-positive B cells, which may be associated with severe lymphocytopenia. The results of this study suggest a resemblance between the IFNAR(-/-) mouse model and lethal infections in humans, as well as roles for multiple cells during pathogenesis in mice.
  • Michihito Sasaki, Yasuko Orba, Satoko Sasaki, Gabriel Gonzalez, Akihiro Ishii, Bernard M. Hang'ombe, Aaron S. Mweene, Kimihito Ito, Hirofumi Sawa
    JOURNAL OF GENERAL VIROLOGY 97 10 2488 - 2493 2016年10月 [査読有り][通常論文]
    Group A rotavirus is a major cause of diarrhoea in humans, especially in young children. Bats also harbour group A rotaviruses, but the genetic backgrounds of bat rotavirus strains are usually distinct from those of human rotavirus strains. We identified a new strain of group A rotavirus in the intestinal contents of a horseshoe bat in Zambia. Whole genome sequencing revealed that the identified virus, named RVA/Bat-wt/ZMB/LUS12-14/2012/G3P[3], possessed the genotype constellation G3-P[3]-I3-R2-C2-M3-A9-N2-T3-E2-H3. Several genome segments of LUS12-14 were highly similar to those of group A rotaviruses identified from humans, cows and antelopes, indicating interspecies transmission of rotaviruses between bats and other mammals with possible multiple genomic reassortment events.
  • Paulina Duhita Anindita, Michihito Sasaki, Haruaki Nobori, Akihiko Sato, Michael Carr, Naoto Ito, Makoto Sugiyama, Yasuko Orba, Hirofumi Sawa
    VIRUS RESEARCH 215 121 - 128 2016年04月 [査読有り][通常論文]
    Rabies is an invariably fatal disease caused by Rabies virus (RABV), a member of the family Rhabdoviridae, genus Lyssavirus. Once central nervous infection occurs and symptoms develop, the case fatality rate approaches 100% despite availability of post-exposure prophylaxis. Therefore, new antiviral therapies for rabies are urgently required. Antivirals which can inhibit virus replication can be identified through screening of small compounds, however, as RABV infection does not generate easily discernible cytopathic effects in vitro, cell viability assays may not be feasible to observe antiviral activity of small compounds against RABV. In this study, recombinant RABVs (rRABVs) encoding NanoLuc luciferase (NanoLuc) were generated to facilitate the screening of small compound libraries. NanoLuc expression was confirmed in single-step growth cures of virus infection and showed that the rRABVs were capable of viral replication without decrease of luciferase activity through ten serial passages. Furthermore, the rRABVs were able to quantify the antiviral activity of the nucleoside analogue ribavirin against RABV in vitro. These findings confirm the potential of the rRABV encoding NanoLuc system to facilitate screening of small compounds to inhibit RABV infection. (C) 2016 Elsevier B.V. All rights reserved.
  • Michihito Sasaki, Gabriel Gonzalez, Yuji Wada, Agus Setiyono, Ekowati Handharyani, Ibenu Rahmadani, Siswatiana Taha, Sri Adiani, Munira Latief, Zainal Abidin Kholilullah, Mawar Subangkit, Shintaro Kobayashi, Ichiro Nakamura, Takashi Kimura, Yasuko Orba, Kimihito Ito, Hirofumi Sawa
    SCIENTIFIC REPORTS 6 24257  2016年04月 [査読有り][通常論文]
    Bufavirus is a recently recognized member of the genus Protoparvovirus in the subfamily Parvovirinae. It has been reported that human bufavirus was detected predominantly in patients with diarrhoea in several countries. However, little is known about bufavirus or its close relatives in nonhuman mammals. In this study, we performed nested-PCR screening and identified bufavirus from 12 megabats of Pteropus spp. in Indonesia. Furthermore, we determined nearly the full genome sequence of a novel megabat-borne bufavirus, tentatively named megabat bufavirus 1. Phylogenetic analyses showed that megabat bufavirus 1 clustered with known protoparvoviruses, including human bufavirus but represented a distinct lineage of bufavirus. Our analyses also inferred phylogenetic relationships among animal-borne bufaviruses recently reported by other studies. Recombination analyses suggested that the most common recent ancestor of megabat bufavirus 1 might have arisen from multiple genetic recombination events. These results characterized megabat bufavirus 1 as the first protoparvovirus discovered from megabats and indicates the high genetic divergence of bufavirus.
  • Shintaro Kobayashi, Tadaki Suzuki, Akira Kawaguchi, Wallaya Phongphaew, Kentaro Yoshii, Tomohiko Iwano, Akihiro Harada, Hiroaki Kariwa, Yasuko Orba, Hirofumi Sawa
    JOURNAL OF BIOLOGICAL CHEMISTRY 291 12 6559 - 6568 2016年03月 [査読有り][通常論文]
    West Nile virus (WNV) particles assemble at and bud into the endoplasmic reticulum (ER) and are secreted from infected cells through the secretory pathway. However, the host factor related to these steps is not fully understood. Rab proteins, belonging to the Ras superfamily, play essential roles in regulating many aspects of vesicular trafficking. In this study, we sought to determine which Rab proteins are involved in intracellular trafficking of nascent WNV particles. RNAi analysis revealed that Rab8b plays a role in WNV particle release. We found that Rab8 and WNV antigen were colocalized in WNV-infected human neuroblastoma cells, and that WNV infection enhanced Rab8 expression in the cells. In addition, the amount of WNV particles in the supernatant of Rab8b-deficient cells was significantly decreased compared with that of wild-type cells. We also demonstrated that WNV particles accumulated in the recycling endosomes in WNV-infected cells. In summary, these results suggest that Rab8b is involved in trafficking of WNV particles from recycling endosomes to the plasma membrane.
  • Michihito Sasaki, Yasuko Orba, Paulina D. Anindita, Akihiro Ishii, Keisuke Ueno, Bernard M. Hang'ombe, Aaron S. Mweeile, Kimihito Ito, Hirofumi Sawa
    EMERGING INFECTIOUS DISEASES 21 7 1230 - 1233 2015年07月 [査読有り][通常論文]
    Viral metagenomic analysis identified a new parvovirus genome in the intestinal contents of wild shrews in Zambia. Related viruses were detected in spleen tissues from wild shrews and nonhuman primates. Phylogenetic analyses showed that these viruses are related to human bufaviruses, highlighting the presence and genetic diversity of bufaviruses in wildlife.
  • Paulina Duhita Anindita, Michihito Sasaki, Agus Setiyono, Ekowati Handharyani, Yasuko Orba, Shintaro Kobayashi, Ibnu Rahmadani, Siswatiana Taha, Sri Adiani, Mawar Subangkit, Ichiro Nakamura, Hirofumi Sawa, Takashi Kimura
    ARCHIVES OF VIROLOGY 160 4 1113 - 1118 2015年04月 [査読有り][通常論文]
    Bats have been shown to serve as natural reservoirs for numerous emerging viruses including severe acute respiratory syndrome coronavirus (SARS-CoV). In the present study, we report the discovery of bat CoV genes in Indonesian Moluccan naked-backed fruit bats (Dobsonia moluccensis). A partial RNA-dependent RNA polymerase gene sequence was detected in feces and tissues samples from the fruit bats, and the region between the RdRp and helicase genes could also be amplified from fecal samples. Phylogenetic analysis suggested that these bat CoVs are related to members of the genus Betacoronavirus.
  • Shintaro Kobayashi, Michihito Sasaki, Ryo Nakao, Agus Setiyono, Ekowati Handharyani, Yasuko Orba, Ibnu Rahmadani, Siswatiana Taha, Sri Adiani, Mawar Subangkit, Ichiro Nakamura, Takashi Kimura, Hirofumi Sawa
    ARCHIVES OF VIROLOGY 160 4 1075 - 1082 2015年04月 [査読有り][通常論文]
    Bats are an important natural reservoir for a variety of viral pathogens, including polyomaviruses (PyVs). The aims of this study were: (i) to determine which PyVs are present in bats in Indonesia and (ii) to analyze the evolutionary relationships between bat PyVs and other known PyVs. Using broad-spectrum polymerase chain reaction (PCR)-based assays, we screened PyV DNA isolated from spleen samples from 82 wild fruit bats captured in Indonesia. Fragments of the PyV genome were detected in 10 of the 82 spleen samples screened, and eight full-length viral genome sequences were obtained using an inverse PCR method. A phylogenetic analysis of eight whole viral genome sequences showed that BatPyVs form two distinct genetic clusters within the proposed genus Orthopolyomavirus that are genetically different from previously described BatPyVs. Interestingly, one group of BatPyVs is genetically related to the primate PyVs, including human PyV9 and trichodysplasia spinulosa-associated PyV. This study has identified the presence of novel PyVs in fruit bats in Indonesia and provides genetic information about these BatPyVs.
  • Yasuko Orba, Michihito Sasaki, Hiroki Yamaguchi, Akihiro Ishii, Yuka Thomas, Hirohito Ogawa, Bernard M. Hang'ombe, Aaron S. Mweene, Shigeru Morikawa, Masayuki Saijo, Hirofumi Sawa
    JOURNAL OF GENERAL VIROLOGY 96 390 - 394 2015年02月 [査読有り][通常論文]
    Human monkeypox is a viral zoonosis caused by monkeypox virus, an orthopoxvirus (OPXV). The majority of human monkeypox cases have been reported in moist forested regions in West and Central Africa, particularly in the Democratic Republic of the Congo (DRC). In this study we investigated zoonotic OPXV infection among wild animals in Zambia, which shares a border with DRC, to assess the geographical distribution of OPXV. We screened for OPXV antibodies in sera from non-human primates (NHPs), rodents and shrews by ELISA, and performed real-time PCR to detect OPXV DNA in spleen samples. Serological analysis indicated that 38 of 259 (14.7 %) rodents, 14 of 42 (33.3%) shrews and 4 of 188 (2.1 %) NHPs had antibodies against OPXV. The OPXV DNA could not be detected in spleens from any animals tested. Our results indicated that wild animals living in rural human habitation areas of Zambia have been infected with OPXV.
  • Michihito Sasaki, Yasuko Orba, Keisuke Ueno, Akihiro Ishii, Ladslav Moonga, Bernard M. Hang'ombe, Aaron S. Mweene, Kimihito Ito, Hirofumi Sawa
    JOURNAL OF GENERAL VIROLOGY 96 440 - 452 2015年02月 [査読有り][通常論文]
    Shrews are small insectivorous mammals that are distributed worldwide. Similar to rodents, shrews live on the ground and are commonly found near human residences. In this study, we investigated the enteric virome of wild shrews in the genus Crocidura using a sequence-independent viral metagenomics approach. A large portion of the shrew enteric virome was composed of insect viruses, whilst novel viruses including cyclovirus, picornavirus and picorna-like virus were also identified. Several cycloviruses, including variants of human cycloviruses detected in cerebrospinal fluid and stools, were detected in wild shrews at a high prevalence rate. The identified picornavirus was distantly related to human parechovirus, inferring the presence of a new genus in this family. The identified picorna-like viruses were characterized as different species of calhevirus 1, which was discovered previously in human stools. Complete or nearly complete genome sequences of these novel viruses were determined in this study and then were subjected to further genetic characterization. Our study provides an initial view of the diversity and distinctiveness of the shrew enteric virome and highlights unique novel viruses related to human stool-associated viruses.
  • Akihiro Ishii, Keisuke Ueno, Yasuko Orba, Michihito Sasaki, Ladslav Moonga, Bernard M. Hang'ombe, Aaron S. Mweene, Takashi Umemura, Kimihito Ito, William W. Hall, Hirofumi Sawa
    NATURE COMMUNICATIONS 5 5651  2014年12月 [査読有り][通常論文]
    Bats can carry important zoonotic pathogens. Here we use a combination of next-generation sequencing and classical virus isolation methods to identify novel nairoviruses from bats captured from a cave in Zambia. This nairovirus infection is highly prevalent among giant leaf-nosed bats, Hipposideros gigas (detected in samples from 16 individuals out of 38). Whole-genome analysis of three viral isolates (11SB17, 11SB19 and 11SB23) reveals a typical bunyavirus tri-segmented genome. The strains form a single phylogenetic clade that is divergent from other known nairoviruses, and are hereafter designated as Leopards Hill virus (LPHV). When i.p. injected into mice, the 11SB17 strain causes only slight body weight loss, whereas 11SB23 produces acute and lethal disease closely resembling that observed with Crimean-Congo Haemorrhagic Fever virus in humans. We believe that our LPHV mouse model will be useful for research on the pathogenesis of nairoviral haemorrhagic disease.
  • Shintaro Kobayashi, Yasuko Orba, Hiroki Yamaguchi, Kenta Takahashi, Michihito Sasaki, Rie Hasebe, Takashi Kimura, Hirofumi Sawa
    VIRUS RESEARCH 191 83 - 91 2014年10月 [査読有り][通常論文]
    Autophagy is a lysosomal degradation pathway that is implicated in many viral infections. However, its role in West Nile virus (WNV) infection remains controversial. In the present study, we examined the relationship between WNV infection and autophagy in infected cells. We demonstrated that LC3-II expression, a molecular marker for autophagosomal membranes, was enhanced in WNV-infected cells 6 h post-infection. LC3-II expression was further enhanced in WNV-inoculated cells when treated with a lysosomal protease inhibitor. Meanwhile, WNV replication in cells lacking Atg5, an essential factor for autophagy, was increased compared with replication in wild-type cells. In addition, WNV replication was inhibited in cells lacking Atg5 when they were transfected with an ATG5 expression plasmid. These results suggest an antiviral role for autophagy in WNV-infected cells. We also examined which viral replication stages were affected by autophagy by using a Tat-beclin 1 peptide to induce autophagy and pseudo-infectious WNV reporter virus particles (WNV-RVPs) that monitor viral genome replication and gene expression stages via GFP expression. We found that autophagy induction in HeLa cells by Tat-beclin 1 peptide 3 h after WNV inoculation inhibited viral replication, and GFP expression was significantly inhibited in wild-type cells when compared with cells lacking Atg5. Taken together, these results suggest that autophagy is induced by WNV infection, and that this induction inhibits WNV replication at the viral genome replication and gene expression stages. (C) 2014 Elsevier B.V. All rights reserved.
  • Jesca Nakayima, Kyoko Hayashida, Ryo Nakao, Akihiro Ishii, Hirohito Ogawa, Ichiro Nakamura, Ladslav Moonga, Bernard M. Hang'ombe, Aaron S. Mweene, Yuka Thomas, Yasuko Orba, Hirofumi Sawa, Chihiro Sugimoto
    PARASITES & VECTORS 7 490  2014年10月 [査読有り][通常論文]
    Background: Wildlife may harbor infectious pathogens that are of zoonotic concern acting as a reservoir of diseases transmissible to humans and domestic animals. This is due to human-wildlife conflicts that have become more frequent and severe over recent decades, competition for the available natural habitats and resources leading to increased human encroachment on previously wild and uninhabited areas. Methods: A total of 88 spleen DNA samples from baboons and vervet monkeys from Zambia were tested for zoonotic pathogens using genus or species-specific PCR. The amplified products were then subjected to sequencing analysis. Results: We detected three different pathogenic agents, including Anaplasma phagocytophilum in 12 samples (13.6%), Rickettsia spp. in 35 samples (39.8%) and Babesia spp. in 2 samples (2.3%). Conclusion: The continuously increasing contacts between humans and primate populations raise concerns about transmission of pathogens between these groups. Therefore, increased medical and public awareness and public health surveillance support will be required to detect and control infections caused by these agents at the interface between humans and wildlife.
  • Hiroki Yamaguchi, Shintaro Kobayashi, Junki Maruyama, Michihito Sasaki, Ayato Takada, Takashi Kimura, Hirofumi Sawa, Yasuko Orba
    JOURNAL OF VETERINARY MEDICAL SCIENCE 76 5 637 - 644 2014年05月 [査読有り][通常論文]
    Recently, we detected novel vervet monkey polyomavirus 1 (VmPyV) in a vervet monkey. Among amino acid sequences of major capsid protein VP1s of other polyomaviruses, VmPyV VP1 is the longest with additional amino acid residues in the C-terminal region. To examine the role of VmPyV VP1 in virion formation, we generated virus-like particles (VLPs) of VmPyV VP1, because VLP is a useful tool for the investigation of the morphological characters of polyomavirus virions. After the full-length VmPyV VP1 was subcloned into a mammalian expression plasmid, the plasmid was transfected into human embryonic kidney 293T (HEK293T) cells. Thereafter, VmPyV VLPs were purified from the cell lysates of the transfected cells via sucrose gradient sedimentation. Electron microscopic analyses revealed that VmPyV VP1 forms VLPs with a diameter of approximately 50 nm that are exclusively localized in cell nuclei. Furthermore, we generated VLPs consisting of the deletion mutant VmPyV VP1 (Delta C VP1) lacking the C-terminal 116 amino acid residues and compared its VLP formation efficiency and morphology to those of VLPs from wild-type VmPyV VP1 (WT VP1). WT and Delta C VP1 VLPs were similar in size, but the number of Delta C VP1 VLPs was much lower than that of WT VP1 VLPs in VP1-expressing HEK293T cells. These results suggest that the length of VP1 is unrelated to virion morphology; however, the C-terminal region of VmPyV VP1 affects the efficiency of its VLP formation.
  • Walter Muleya, Michihito Sasaki, Yasuko Orba, Akihiro Ishii, Yuka Thomas, Emiko Nakagawa, Hirohito Ogawa, Bernard Hang'ombe, Boniface Namangala, Aaron Mweene, Ayato Takada, Takashi Kimura, Hirofumi Sawa
    JOURNAL OF VETERINARY MEDICAL SCIENCE 76 4 611 - 614 2014年04月 [査読有り][通常論文]
    In this study, we describe the detection of novel paramyxoviruses from the Eidolon helvum species of fruit bats. We extracted RNA from 312 spleen samples from bats captured in Zambia over a period of 4 years (2008-2011). Semi-nested RT-PCR detected a total of 25 (8%) positive samples for paramyxoviruses which were then directly sequenced and analyzed using phylogenetic analysis. Among the positive samples, seven novel paramyxoviruses were detected. Five viruses were closely related to the genus Henipavirus, while two viruses were related to the unclassified Bat paramyxoviruses from Ghana and Congo Brazzaville. Our study identified novel Henipavirus-related and unrelated viruses using RT-PCR in fruit bats from Kansaka National Park and indicated the presence of similar Bat paramyxoviruses originating from wide geographic areas, suggesting the ability of bats to harbor and transmit viruses. The presence of these viruses in fruit bats might pose a public health risk.
  • Michihito Sasaki, Walter Muleya, Akihiro Ishii, Yasuko Orba, Bernard M. Hang'ombe, Aaron S. Mweene, Ladslav Moonga, Yuka Thomas, Takashi Kimura, Hirofumi Sawa
    JOURNAL OF GENERAL VIROLOGY 95 325 - 330 2014年02月 [査読有り][通常論文]
    Rodents and shrews are known to harbour various viruses. Paramyxoviruses have been isolated from Asian and Australian rodents, but little is known about them in African rodents. Recently, previously unknown paramyxovirus sequences were found in South African rodents. To date, there have been no reports related to the presence and prevalence of paramyxoviruses in shrews. We found a high prevalence of paramyxoviruses in wild rodents and shrews from Zambia. Seminested reverse transcription-PCR assays were used to detect paramyxovirus RNA in 21% (96/ 462) of specimens analysed. Phylogenetic analysis revealed that these viruses were novel paramyxoviruses and could be classified as morbillivirus- and henipavirus-related viruses, and previously identified rodent paramyxovirus-related viruses. Our findings suggest the circulation of previously unknown paramyxoviruses in African rodents and shrews, and provide new information regarding the geographical distribution and genetic diversity of paramyxoviruses.
  • Sawa H, Kobayashi S, Suzuki T, Orba Y
    Uirusu 64 25 - 34 1 2014年 [査読有り][通常論文]
  • Tadaki Suzuki, Yasuko Orba, Yoshinori Makino, Yuki Okada, Yuji Sunden, Hideki Hasegawa, William W. Hall, Hirofumi Sawa
    Viroporins, which are encoded by a wide range of animal viruses, oligomerize in host cell membranes and form hydrophilic pores that can disrupt a number of physiological properties of the cell. Little is known about the relationship between host cell proteins and viroporin activity. The human JC polyomavirus (JCV) is the causative agent of progressive multifocal leukoencephalopathy. The JCV-encoded agnoprotein, which is essential for viral replication, has been shown to act as a viroporin. Here we demonstrate that the JCV agnoprotein specifically interacts with adaptor protein complex 3 through its delta subunit. This interaction interrupts adaptor protein complex 3-mediated vesicular trafficking with suppression of the targeting of the protein to the lysosomal degradation pathway and instead permits the transport of agnoprotein to the cell surface with resulting membrane permeabilization. The findings demonstrate a previously undescribed paradigm in virus-host interactions allowing the host to regulate viroporin activity and suggest that the viroporins of other viruses may also be highly regulated by specific interactions with host cell proteins.
  • Shintaro Kobayashi, Tadaki Suzuki, Manabu Igarashi, Yasuko Orba, Noriko Ohtake, Keita Nagakawa, Kenichi Niikura, Takashi Kimura, Harumi Kasamatsu, Hirofumi Sawa
    PLoS ONE 8 10 e76668  2013年10月09日 [査読有り][通常論文]
    The capsid of the human polyomavirus JC virus (JCV) consists of 72 pentameric capsomeres of a major structural protein, Vp1. The cysteine residues of the related Vp1 of SV40 are known to contribute to Vp1 folding, pentamer formation, pentamer-pentamer contacts, and capsid stabilization. In light of the presence of a slight structural difference between JCV Vp1 and SV40 counterpart, the way the former folds could be either different from or similar to the latter. We found a difference: an important contribution of Vp1 cysteines to the formation of infectious virions, unique in JCV and absent in SV40. Having introduced amino acid substitution at each of six cysteines (C42, C80, C97, C200, C247, and C260) in JCV Vp1, we found that, when expressed in HeLa cells, the Vp1 level was decreased in C80A and C247A mutants, and remained normal in the other mutants. Additionally, the C80A and C247A Vp1-expressing cell extracts did not show the hemagglutination activity characteristic of JCV particles. The C80A and C247A mutant Vp1s were found to be less stable than the wild-type Vp1 in HeLa cells. When produced in a reconstituted in vitro protein translation system, these two mutant proteins were stable, suggesting that some cellular factors were responsible for their degradation. As determined by their sucrose gradient sedimentation profiles, in vitro translated C247A Vp1 formed pentamers, but in vitro translated C80A Vp1 was entirely monomeric. When individually incorporated into the JCV genome, the C80A and C247A mutants, but not the other Vp1 cysteine residues mutants, interfered with JCV infectivity. Furthermore, the C80A, but not the C247A, mutation prevented the nuclear localization of Vp1 in JCV genome transfected cells. These findings suggest that C80 of JCV Vp1 is required for Vp1 stability and pentamer formation, and C247 is involved in capsid assembly in the nucleus.
  • Takashi Kimura, Megumi Okumura, Eunmi Kim, Michihito Sasaki, Yasuko Orba, Hirofumi Sawa
    MICROBIOLOGY AND IMMUNOLOGY 57 10 723 - 731 2013年10月 [査読有り][通常論文]
    Neurons are the major target cell of Japanese encephalitis virus (JEV). Rats intracerebrally inoculated with JEV show an age-dependent pattern of resistance to infection in which resistance is closely associated with neuronal maturation. However, because there is no reliable and convenient cell culture system that mimics the in vivo properties of JEV infection of immature and mature neurons, the mechanisms underlying this association remain poorly understood. The aim of the present study was to examine JEV infection in immortalized CSM14.1 rat neuronal cells, which can be induced to differentiate into neurons by culture under non-permissive conditions. JEV infected undifferentiated CSM14.1 cells more efficiently than differentiated cells, resulting in production of more progeny virus in the former setting than in the latter. An infectious virus recovery assay detected more internalized virions in undifferentiated cells. On the other hand, JEV infection of differentiated cells induced more rapid and stronger expression of interferon- gene, along with smaller amounts of JEV RNA. Taken together, these results show that the initial phase of viral infection and the later IFN response play roles in the viral susceptibility of undifferentiated and differentiated CSM14.1 cells. Because CSM14.1 cells became more resistant to JEV infection as they mature, this culture system can be used as an in vitro model for studying age-dependent resistance of neurons to JEV infection.
  • Michihito Sasaki, Akihiro Ishii, Yasuko Orba, Yuka Thomas, Bernard M. Hang'ombe, Ladslav Moonga, Aaron S. Mweene, Hirohito Ogawa, Ichiro Nakamura, Takashi Kimura, Hirofumi Sawa
    EMERGING INFECTIOUS DISEASES 19 9 1500 - 1503 2013年09月 [査読有り][通常論文]
    Human parainfluenza virus type 3 (HPIV3) genome was detected in 4 baboons in Zambia. Antibody for HPIV3 was detected in 13 baboons and 6 vervet monkeys in 2 distinct areas in Zambia. Our findings suggest that wild nonhuman primates are susceptible to HPIV3 infection.
  • Ichiro Nakamura, Bernard Mudenda Hang'ombe, Hirofumi Sawa, Shintaro Kobayashi, Yasuko Orba, Akihiro Ishii, Yuka Thomas, Rie Isozumi, Kumiko Yoshimatsu, Aaron S. Mweene, Ayato Takada, Chihiro Sugimoto, Jiro Arikawa
    JOURNAL OF VETERINARY MEDICAL SCIENCE 75 6 819 - 825 2013年06月 [査読有り][通常論文]
    A total of 466 rodents were captured in the Republic of Zambia from 2006 to 2010. Based on morphological observations and phylogenetic analyses of mitochondrial gene sequences, rodents were divided into 10 groups consisting of 39 Rattus rodents, 263 multimammate rats, 18 other Murinae rodents, 95 gerbils, 11 pouched mice, 1 giant-pouched rat, 38 fat mice and 1 dormouse. Rodent antibodies except that from Rattus were examined for their cross-reactivity to commercially available antibody detection reagents. Anti-mouse immunoglobulin G (IgG) was most cross-reactive to heterologous antibodies including multimammate rat, gerbil, pouched mouse and fat mouse. Thus, anti-mouse IgG would be a useful detection tool in serological examination of the Zambian rodent population. Preliminary sero-surveillance for plague, leptospirosis and hantavirus infection was performed by ELISA.
  • Hiroki Yamaguchi, Shintaro Kobayashi, Akihiro Ishii, Hirohito Ogawa, Ichiro Nakamura, Ladslav Moonga, Bernard M. Hang'ombe, Aaron S. Mweene, Yuka Thomas, Takashi Kimura, Hirofumi Sawa, Yasuko Orba
    Journal of General Virology 94 6 1357 - 1364 2013年06月01日 [査読有り][通常論文]
    To examine polyomavirus (PyV) infection in wildlife, we investigated the presence of PyVs in Zambia with permission from the Zambia Wildlife Authority. We analysed 200 DNA samples from the spleens and kidneys (n5100 each) of yellow baboons and vervet monkeys (VMs) (n550 each). We detected seven PyV genome fragments in 200 DNA samples using a nested broadspectrum PCR method, and identified five full-length viral genomes using an inverse PCR method. Phylogenetic analysis of virally encoded proteins revealed that four PyVs were closely related to either African green monkey PyV or simian agent 12. Only one virus detected from a VM spleen was found to be related, with relatively low nucleotide sequence identity (74 %), to the chimpanzee PyV, which shares 48% nucleotide sequence identity with the human Merkel cell PyV identified from Merkel cell carcinoma. The obtained entire genome of this virus was 5157 bp and had large T- and small t-antigens, and VP1 and VP2 ORFs. This virus was tentatively named vervet monkey PyV 1 (VmPyV1) as a novel PyV. Comparison with other PyVs revealed that VmPyV1, like chimpanzee PyV, had a longer VP1 ORF. To examine whether the VmPyV1 genome could produce viral proteins in cultured cells, the whole genome was transfected into HEK293T cells. We detected VP1 protein expression in the transfected HEK293T cells by immunocytochemical and immunoblot analyses. Thus, we identified a novel PyV genome from VM spleen. © 2013 SGM.
  • Kenichi Niikura, Tatsuya Matsunaga, Tadaki Suzuki, Shintaro Kobayashi, Hiroki Yamaguchi, Yasuko Orba, Akira Kawaguchi, Hideki Hasegawa, Kiichi Kajino, Takafumi Ninomiya, Kuniharu Ijiro, Hirofumi Sawa
    ACS NANO 7 5 3926 - 3938 2013年05月 [査読有り][通常論文]
    This paper demonstrates how the shape and size of gold nanoparticles (AuNPs) affect immunological responses in vivo and in vitro for the production of antibodies for West Nile virus (WNV). We prepared spherical (20 and 40 nm in diameter), rod (40 x 10 nm), and cubic (40 x 40 x 40 nm) AuNPs as adjuvants and coated them with WNV envelope (E) protein. We measured anti-WNVE antibodies after inoculation of these WNVE-coated AuNPs (AuNP-Es) into mice. The 40 nm spherical AuNP-Es (Sphere40-Es) induced the highest level of WNVE-specific antibodies, while rod AuNP-Es (Rod-Es) induced only 50% of that of Sphere40-E. To examine the mechanisms of the shape-dependent WNVE antibody production, we next measured the efficiency of cellular uptake of AuNP-Es into RAW264.7 macrophage cells and bone-marrow-derived dendritic cells (BMDCs) and the subsequent cytokine secretion from BMDCs. The uptake of Rod-Es into the cells proceeded more efficiently than those of Sphere-Es or cubic WNVE-coated AuNPs (Cube-Es), suggesting that antibody production was not dependent on the uptake efficiency of the different AuNP-Es. Cytokine production from BMDCs treated with the AuNP-Es revealed that only Rod-E-treated cells produced significant levels of interleukin-1 beta (IL-1 beta) and interleukin-18 (IL-18), indicating that Rod-Es activated inflammasome-dependent cytokine secretion. Meanwhile, Sphere40-Es and Cube-Es both significantly induced inflammatory cytokine production, including tumor necrosis factor-alpha (TNF-alpha), IL-6, IL-12, and granulocyte macrophage colony-stimulating factor (GM-CSF). These results suggested that AuNPs are effective vaccine adjuvants and enhance the immune response via different cytokine pathways depending on their sizes and shapes.
  • Kenta Takahashi, Yasuko Orba, Taichi Kimura, Lei Wang, Shinji Kohsaka, Masumi Tsuda, Mishie Tanino, Hiroshi Nishihara, Kazuo Nagashima, Hirofumi Sawa, Shinya Tanaka
    JAPANESE JOURNAL OF INFECTIOUS DISEASES 66 2 126 - 132 2013年03月 [査読有り][通常論文]
    JC virus (JCV) is a causative agent of progressive multifocal leukoencephalopathy (PML). Methyl CpG binding protein 2 (MeCP2) is a transcriptional control nuclear protein that is abundantly expressed in neurons. We previously observed that the MeCP2 protein is expressed in JCV large T antigen (TAg)-expressing glial cells in PML brains. To investigate the relationship between MeCP2 and JCV TAg, we examined the promoter activity and mRNA and protein expression levels of MeCP2 in JCV TAg-expressing cells. We found that JCV TAg enhances the promoter activity of MeCP2, but does not enhance the mRNA and protein levels of MeCP2. These results suggest that post-transcriptional mechanisms may play a role in MeCP2 expression.
  • Tadaki Suzuki, Shingo Semba, Yuji Sunden, Yasuko Orba, Shintaro Kobayashi, Kazuo Nagashima, Takashi Kimura, Hideki Hasegawa, Hirofumi Sawa
    MICROBIOLOGY AND IMMUNOLOGY 56 9 639 - 646 2012年09月 [査読有り][通常論文]
    JC virus (JCV) belongs to the polyomavirus family of double-stranded DNA viruses and causes progressive multifocal leukoencephalopathy in humans. JCV encodes early proteins (large T antigen, small T antigen, and T' antigen) and four late proteins (agnoprotein, and three viral capsid proteins, VP1, VP2, and VP3). In the current study, a novel function for JCV agnoprotein in the morphogenesis of JC virion particles was identified. It was found that mature virions of agnoprotein-negative JCV are irregularly shaped. Sucrose gradient sedimentation and cesium chloride gradient ultracentrifugation analyses revealed that the particles of virus lacking agnoprotein assemble into irregularly sized virions, and that agnoprotein alters the efficiency of formation of VP1 virus-like particles. An in vitro binding assay and immunocytochemistry revealed that agnoprotein binds to glutathione S-transferase fusion proteins of VP1 and that some fractions of agnoprotein colocalize with VP1 in the nucleus. In addition, gel filtration analysis of formation of VP1-pentamers revealed that agnoprotein enhances formation of these pentamers by interacting with VP1. The present findings suggest that JCV agnoprotein plays a role, similar to that of SV40 agnoprotein, in facilitating virion assembly.
  • Shintaro Kobayashi, Yasuko Orba, Hiroki Yamaguchi, Takashi Kimura, Hirofumi Sawa
    NEUROPATHOLOGY 32 4 398 - 405 2012年08月 [査読有り][通常論文]
    West Nile virus (WNV) belongs to the Flaviviridae family of viruses and has emerged as a significant cause of viral encephalitis in humans, animals and birds. It has been reported that WNV replication directly induces neuronal injury, followed by neuronal cell death proven as apoptosis. Therefore, it is important to understand the mechanism of neuronal apoptosis caused by this virus to develop strategies to control its pathogenicity. Accumulation of ubiquitinated abnormal proteins has been reported to be associated with neuronal apoptosis in some pathological conditions. A lot of cellular stresses prevent cellular protein quality control mechanisms, resulting in the accumulation of ubiquitinated abnormal proteins. To obtain a better understanding of the mechanisms of WNV-induced neuronal apoptosis, we evaluated the accumulation of ubiquitinated proteins in the WNV-infected neuronal cells. We have observed that WNV infection caused massive neuronal injury in the brains of mice. Viral antigen was detected in the neuronal cytoplasm of the cells exhibiting neuronal apoptosis. Notably, ubiquitinated proteins were detected in WNV-infected neuronal cells. In addition, accumulation of ubiquitinated proteins was markedly enhanced in mouse neuroblastoma, Neuro-2a cells after WNV infection. Our histopathological and in vitro studies suggest that accumulation of ubiquitinated proteins in neuronal cells might be associated with neuronal apoptosis caused by WNV infection.
  • Shigetomo Fukuhara, Szandor Simmons, Shunsuke Kawamura, Asuka Inoue, Yasuko Orba, Takeshi Tokudome, Yuji Sunden, Yuji Arai, Kazumasa Moriwaki, Junji Ishida, Akiyoshi Uemura, Hiroshi Kiyonari, Takaya Abe, Akiyoshi Fukamizu, Masanori Hirashima, Hirofumi Sawa, Junken Aoki, Masaru Ishii, Naoki Mochizuki
    JOURNAL OF CLINICAL INVESTIGATION 122 4 1416 - 1426 2012年04月 [査読有り][通常論文]
    The bioactive lysophospholipid mediator sphingosine-l-phosphate (SIP) promotes the egress of newly formed T cells from the thymus and the release of immature B cells from the bone marrow. It has remained unclear, however, where and how SIP is released. Here, we show that in mice, the SIP transporter spinster homolog 2 (Spns2) is responsible for the egress of mature T cells and immature B cells from the thymus and bone marrow, respectively. Global Spns2-KO mice exhibited marked accumulation of mature T cells in thymi and decreased numbers of peripheral T cells in blood and secondary lymphoid organs. Mature recirculating B cells were reduced in frequency in the bone marrow as well as in blood and secondary lymphoid organs. Bone marrow reconstitution studies revealed that Spns2 was not involved in SW release from blood cells and suggested a role for Spns2 in other cells. Consistent with these data, endothelia-specific deletion of Spns2 resulted in defects of lymphocyte egress similar to those observed in the global Spns2-KO mice. These data suggest that Spns2 functions in ECs to establish the S1P gradient required for T and B cells to egress from their respective primary lymphoid organs. Furthermore, Spns2 could be a therapeutic target for a broad array of inflammatory and autoimmune diseases.
  • Yasuko Orba, Shintaro Kobayashi, Ichiro Nakamura, Akihiro Ishii, Bernard M. Hang'ombe, Aaron S. Mweene, Yuka Thomas, Takashi Kimura, Hirofumi Sawa
    JOURNAL OF GENERAL VIROLOGY 92 4 789 - 795 2011年04月 [査読有り][通常論文]
    To investigate polyomavirus infection in wild rodents, we analysed DNA samples from the spleens of 100 wild rodents from Zambia using a broad-spectrum PCR-based assay. A previously unknown polyomavirus genome was identified in a sample from a multimammate mouse (Mastomys species) and the entire viral genome of 4899 bp was :subsequently sequenced. This viral genome contained potential ORFs for the capsid proteins, VP1, VP2 and VP3, and early proteins, small t antigen and large T antigen. Phylogenetic analysis showed that it was a novel member of the family Polyomaviridae, and thus the virus was tentatively named mastomys polyomavirus. After transfection of the viral genome into several mammalian cell lines, transient expression of the VP1 and large T antigen proteins was confirmed by immunoblotting and immunocytochemical analyses. Comparison of large T antigen function in mastomys polyomavirus with that in rhesus monkey polyomavirus SV40 and human polyomavirus JC virus revealed that the large T antigen from mastomys polyomavirus interacted with the tumour suppressor protein pRb, but not with p53.
  • Tadaki Suzuki, Satoko Yamanouchi, Yuji Sunden, Yasuko Orba, Takashi Kimura, Hirofumi Sawa
    JOURNAL OF MEDICAL VIROLOGY 82 7 1229 - 1235 2010年07月 [査読有り][通常論文]
    The human polyomavirus JC virus (JCV) infects 70-80% of humans and establishes latent infection in the kidney. In immunosuppressed patients, JCV reactivates and causes a fatal and progressive neurological disease known as progressive multifocal leukoencephalopathy (PML). Over the past three decades, PML has become an important neurological complication in acquired immunodeficiency syndrome (AIDS) patients. Recently, it was reported that patients treated with therapeutics that target the integrin receptor very late antigen (VLA)-4 are at increased risk of developing PML. However, the relationship between Natalizumab and this unexpected onset of PML has yet to be elucidated. Here, we investigated the effect of Natalizumab on the growth of JCV in the permissive human neural cell line IMR-32 following viral inoculation. Natalizumab had no effect either on the expression levels of viral proteins as determined by immunoblot analysis using specific antibodies or on the hemagglutination activity of cellular lysates from infected cells. These results suggest that there is no direct effect of Natalizumab on JCV infectivity in IMR-32 cells in vitro. J. Med. Virol. 82:1229-1235, 2010. (C) 2010 Wiley-Liss, Inc.
  • Tadaki Suzuki, Yasuko Orba, Yuki Okada, Yuji Sunden, Takashi Kimura, Shinya Tanaka, Kazuo Nagashima, William W. Hall, Hirofumi Sawa
    PLOS PATHOGENS 6 3 e1000801  2010年03月 [査読有り][通常論文]
    Virus infections can result in a range of cellular injuries and commonly this involves both the plasma and intracellular membranes, resulting in enhanced permeability. Viroporins are a group of proteins that interact with plasma membranes modifying permeability and can promote the release of viral particles. While these proteins are not essential for virus replication, their activity certainly promotes virus growth. Progressive multifocal leukoencephalopathy (PML) is a fatal demyelinating disease resulting from lytic infection of oligodendrocytes by the polyomavirus JC virus (JCV). The genome of JCV encodes six major proteins including a small auxiliary protein known as agnoprotein. Studies on other polyomavirus agnoproteins have suggested that the protein may contribute to viral propagation at various stages in the replication cycle, including transcription, translation, processing of late viral proteins, assembly of virions, and viral propagation. Previous studies from our and other laboratories have indicated that JCV agnoprotein plays an important, although as yet incompletely understood role in the propagation of JCV. Here, we demonstrate that agnoprotein possesses properties commonly associated with viroporins. Our findings demonstrate that: (i) A deletion mutant of agnoprotein is defective in virion release and viral propagation; (ii) Agnoprotein localizes to the ER early in infection, but is also found at the plasma membrane late in infection; (iii) Agnoprotein is an integral membrane protein and forms homo-oligomers; (iv) Agnoprotein enhances permeability of cells to the translation inhibitor hygromycin B; (v) Agnoprotein induces the influx of extracellular Ca(2+); (vi) The basic residues at amino acid positions 8 and 9 of agnoprotein key are determinants of the viroporin activity. The viroporin-like properties of agnoprotein result in increased membrane permeability and alterations in intracellular Ca(2+) homeostasis leading to membrane dysfunction and enhancement of virus release.
  • Yasuko Orba, Tadaki Suzuki, Yoshinori Makino, Kanako Kubota, Shinya Tanaka, Takashi Kimura, Hirofumi Sawa
    JOURNAL OF BIOLOGICAL CHEMISTRY 285 2 1544 - 1554 2010年01月 [査読有り][通常論文]
    Large T antigen (TAg) of the human polyomavirus JC virus (JCV) possesses DNA binding and helicase activities, which, together with various cellular proteins, are required for replication of the viral genome. We now show that JCV-infected cells expressing TAg accumulate in the G(2) phase of the cell cycle as a result of the activation of ATM- and ATR-mediated G(2) checkpoint pathways. Transient transfection of cells with a TAg expression vector also induced G(2) checkpoint signaling and G(2) arrest. Analysis of TAg mutants with different subnuclear localizations suggested that the association of TAg with cellular DNA contributes to the induction of G(2) arrest. Abrogation of G(2) arrest by inhibition of ATM and ATR, Chk1, and Wee1 suppressed JCV genome replication. In addition, abrogation of the G(2)-M transition by Cdc2 depletion disabled Wee1 depletion induced suppression of JCV genome replication, suggesting that JCV replication is facilitated by G(2) arrest resulting from G(2) checkpoint signaling. Moreover, inhibition of ATM and ATR by caffeine suppressed JCV production. The observation that oligodendrocytes productively infected with JCV in vivo also undergo G(2) arrest suggests that G(2) checkpoint inhibitors such as caffeine are potential therapeutic agents for JCV infection.
  • Akira Kawaguchi, Yasuko Orba, Takashi Kimura, Hidekatsu Iha, Masao Ogata, Takahiro Tsuji, Akira Ainai, Tetsutaro Sata, Takashi Okamoto, William W. Hall, Hirofumi Sawa, Hideki Hasegawa
    BLOOD 114 14 2961 - 2968 2009年10月 [査読有り][通常論文]
    Adult T-cell leukemia (ATL) is a T-cell malignancy caused by human T lymphotropic virus type I, and presents as an aggressive leukemia with characteristic widespread leukemic cell infiltration into visceral organs and skin. The molecular mechanisms associated with leukemic cell infiltration are poorly understood. We have used mouse models of ATL to investigate the role of chemokines in this process. Transfer of splenic lymphomatous cells from transgenic to SCID mice reproduces a leukemia and lymphoma that is histologically identical to human disease. It could be shown that lymphomatous cells exhibit specific chemotactic activity in response to stromal cell-derived factor-1 alpha (SDF-1 alpha). Lymphomatous cells exhibited surface expression of CXCR4, the specific receptor of SDF-1 alpha. AMD3100, a CXCR4 antagonist, was found to inhibit both SDF-1 alpha-induced migration and phosphorylation of extracellular signal-related kinase 1/2. Investigation of cultured cells from human ATL patients revealed identical findings. Using the SCID mouse model, it could be demonstrated that AMD3100 inhibited infiltration of lymphomatous cells into liver and lung tissues in vivo. These results demonstrate the involvement of the SDF-1 alpha/CXCR4 interaction as one mechanism of leukemic cell migration and this may provide a novel target as part of combination therapy for ATL. (Blood. 2009; 114: 2961-2968)
  • Tomoko Matoba, Yasuko Orba, Tadaki Suzuki, Yoshinori Makino, Hideo Shichinohe, Satoshi Kuroda, Takahiro Ochiya, Hiroshi Itoh, Shinya Tanaka, Kazuo Nagashima, Hirofumi Sawa
    NEUROPATHOLOGY 28 3 286 - 294 2008年06月 [査読有り][通常論文]
    JC virus (JCV) is the etiological agent of the demyelinating disease progressive multifocal leukoencephalopathy (PML). Because JCV has a very narrow host range, it has been difficult to develop an animal model of JCV infection; as a result, no effective therapy for PML has been established. In this study, we have tried to create an animal model that replaces an in vivo JCV infection. As a result, we have obtained a stable persistence of JCV-infected human cells in the mouse brain by inoculating the virus-infected cells into the nude mice brains. In this model, the JCV-infected cells were well preserved in the nude mouse brains for 2 weeks. We then treated JCV-injected brains with an siRNA against the JCV agnoprotein that is known to be an effective inhibitor of JCV infection in vitro. A highly purified type I collagen, atelocollagen, was used as a carrier for the siRNA. The siRNA inhibited the expression of JCV protein in inoculated JCV-infected cells in the mouse brain, compared to the medium containing only atelocollagen used as a placebo. Thus, the combination of siRNA and atelocollagen might be a candidate therapeutic agent for the treatment of JCV infection.
  • Hayashi Y, Kimura A, Kato S, Koumura A, Sakurai T, Tanaka Y, Hozumi I, Sunden Y, Orba Y, Sawa H, Takahashi H, Inuzuka T
    Journal of the neurological sciences 268 1-2 195 - 198 1-2 2008年05月 [査読有り][通常論文]
    We report progressive multifocal leukoencephalopathy (PML) and CD4+ T-lymphocytopenia in a 71-year-old man with Sjogren syndrome (SjS). The patient was admitted to our hospital because of progressive dementia and gait disturbance. T2-weighted MR images showed high-intensity lesions in his left frontal white matter thalamus, cerebellum and brainstem. A pathological diagnosis of PML was made by brain biopsy. SjS is frequently accompanied with immunological complications; however, there are few reports on PML in patients with SjS. Recently, isolated CD4+ T-lymphocytopenia is reported to be one of the based immunological conditions associated with the development of PML. In the present case, CD4+ T-lymphocytopenia was also observed on admission, which is also associated with SjS. (C) 2007 Elsevier B.V. All rights reserved.
  • Jun Nakae, Yongheng Cao, Miyo Oki, Yasuko Orba, Hirofumi Sawa, Hiroshi Kiyonari, Kristy Iskandar, Koji Suga, Marc Lombes, Yoshitake Hayashi
    DIABETES 57 3 563 - 576 2008年03月 [査読有り][通常論文]
    OBJECTIVE-Adipose tissue serves as an integrator of various physiological pathways, energy balance, and glucose homeostasis. Forkhead box-containing protein O subfamily (FoxO) 1 mediates insulin action at the transcriptional level. However, physiological roles of FoxO1 in adipose tissue remain unclear. RESEARCH DESIGN AND METHODS-In the present study, we generated adipose tissue-specific FoxO1. transgenic mice (adipocyte protein 2 [aP(2)]-FLAG-Delta 256) using an aP(2) promoter/enhancer and a mutant FoxO1 (FLAG Delta 256) in which the carboxyl terminal transactivation domain was deleted. Using these mice, we analyzed the effects of the overexpression of FLAG Delta 256 on glucose metabolism and energy homeostasis. RESULTS-The aP(2)-FLAG-Delta 256 mice showed improved glucose tolerance and insulin sensitivity accompanied with smaller-sized adipocytes and increased adiponectin (adipoq) and Glut 4 (Slc2a4) and decreased tumor necrosis factor alpha (Tnf) and chemokine (C-C motif) receptor 2 (Ccr2) gene expression levels in white adipose tissue (WAT) under a high-fat diet. Furthermore, the aP(2)-FLAG-Delta 256 mice had increased oxygen consumption accompanied with increased expression of peroxisome proliferator-activated receptor gamma coactivator (PGC)-1 alpha protein and uncoupling protein (UCP)-1 (Ucp1), UCP-2 (Ucp2), and beta 3-AR (Adrb3) in brown adipose tissue (BAT). Overexpression of FLAG Delta 256 in T37i cells, which are derived from the hibernoma of SV40 large T antigen transgenic mice, increased expression of PGC-1 alpha protein and Ucp1. Furthermore, knockdown of endogenous FoxO1 in T37i cells increased Pgc1 alpha (Ppargc1a), Pgc1 beta (Ppargc1b), Ucp1, and Adrb3 gene expression. CONCLUSIONS-These data suggest that FoxO1 modulates energy homeostasis in WAT and BAT through regulation of adipocyte size and adipose tissue-specific gene expression in response to excessive calorie intake.
  • Yasuko Orba, Yuji Sunden, Tadaki Suzuki, Kazuo Nagashima, Takashi Kimura, Shinya Tanaka, Hirofumi Sawa
    VIROLOGY 370 1 173 - 183 2008年01月 [査読有り][通常論文]
    The human Polyomavirus JC virus (JCV) utilizes cellular proteins for viral replication and transcription in the host cell nucleus. These cellular proteins represent potential targets for antiviral drugs against the JCV. In this study, we examined the antiviral effects of the pharmacological cyclin-dependent kinase (cdk) inhibitor R-Roscovitine, which has been shown to have antiviral activity against other viruses. We found that Roscovitine significantly inhibited the viral production and cytopathic effects of the JCV in a JCV-infected cell line. Roscovitine attenuated the transcriptional activity of JCV late genes, but not early genes, and also prevented viral replication via inhibiting phosphorylation of the viral early protein, large T antigen. These data suggest that the JCV requires cdks to transcribe late genes and to replicate its own DNA. That Roscovitine exhibited antiviral activity in JCV-infected cells suggests that Roscovitine might have therapeutic utility in the treatment of progressive multifocal leukoencephalopathy (PML). (c) 2007 Elsevier Inc. All rights reserved.
  • Hirofumi Sawa, Tadaki Suzuki, Yasuko Orba, Yuji Sunden, Kazuo Nagashima
    Brain and Nerve 59 2 101 - 108 2007年02月 [査読有り][通常論文]
    JC virus (JCV) is a causative agent of progressive multifocal leukoencephalopathy and belongs to Polyomavirus. In this article we describe our recent research relating to this virus. First, JCV's major capsid protein VP1 possesses a nuclear localization signal (NLS) and has the ability to construct a virus-like particle (VLP). We have investigated the mechanism of nuclear entry of JCV using VLP, and clarified the role of NLS. In vitro transport assay revealed that wild type VLP (wtVLP), but not ANLSVLP, entered the nuclei of cells. The nuclear transport of wtVLP was dependent on the addition of importins α and β and was prevented by antibodies to nuclear pore complex (NPC). These results suggested that JCV VLP binds to cellular importins via the NLS of VP1 and is transported into the nucleus through the NPC. Second, a yeast two-hybrid screen of a human brain cDNA library demonstrated that the fasciculation and elongation protein zeta 1 (FEZ1) and the heterochromatin protein 1α (HP1α) are proteins that interacted with JCV agnoprotein (Agno). In vitro binding assay showed that Agno interacts directly with FEZ1 and HP1α. We have also shown that Agno induces the dissociation of FEZ1 from microtubules and dissociates the interaction between HP1α and lamin B receptor. We have demonstrated that interaction between Agno and these host proteins inhibited nuclear egress of JCV. Third, in order to inhibit JCV infection in infected cells, we synthesized siRNA which is specific for JCV Agno. Immunoblotting and immunocytochemical analysis demonstrated that expression levels of agnoprotein and VP1 were significantly inhibited by specific siRNA. In addition, levels of viral mRNAs and viral production were decreased in the cells transfected with Agno siRNA. Furthermore, viral production of cell treated with Agno siRNA was significantly inhibited. These results indicate that post-infection treatment with siRNAs, that targets JCV Agno suppresses virus production in JCV infected cells. Thus, siRNA directed against JCV encoding genes may provide a useful tool for suppression of JCV infection.
  • Sawa H, Suzuki T, Orba Y, Sunden Y, Nagashima K
    Brain and nerve = Shinkei kenkyu no shinpo 59 101 - 108 2 2007年02月 [査読有り][通常論文]
  • Yuji Sunden, Shingo Semba, Tadaki Suzuki, Yuki Okada, Yasuko Orba, Kazuo Nagashima, Takashi Umemura, Hirofumi Sawa
    MICROBIOLOGY AND IMMUNOLOGY 51 3 327 - 337 2007年 [査読有り][通常論文]
    To investigate the mechanism behind JC virus (JCV) cell specificity we performed electrophoretic mobility shift assays (EMSA) using probes derived from the JCV transcriptional control region (JCV-TCR). Using nuclear extracts from the JCV-susceptible neuroblastoma cell line IMR-32, EMSA revealed a 670 kDa JCV-TCR-binding protein complex designated as #3-bp. This complex could not be detected in nuclear extracts from non-susceptible cell lines. Using column chromatographic purification and microsequencing, we identified cleavage stimulation factor (CstF) as a component of #3-bp. However, as CstF is present in many cell types, we speculated that the IMR-32-specific component(s) of #3bp bind CAR We performed a yeast two-hybrid assay using CstF-77 as the bait against a HeLa cDNA-subtracted IMR-32 cDNA library. This analysis detected binding between CstF-77 and the RNA helicase DDX1. Subsequently, biotinylated DNA affinity precipitation and chromatin immunoprecipitation assays also confirmed that DDX1 binds specifically to JCV-TCR. Our findings indicate that an association between DDX1 and the JCV-TCR may play a significant role in JCV infection in IMR-32 cells.
  • Yuji Sunden, Shingo Semba, Tadaki Suzuki, Yuki Okada, Yasuko Orba, Kazuo Nagashima, Takashi Umemura, Hirofumi Sawa
    MICROBIOLOGY AND IMMUNOLOGY 51 3 339 - 347 2007年 [査読有り][通常論文]
    Recently, we demonstrated that the DEAD box protein 1 (DDX1), an RNA helicase, and the cleavage stimulation factor (CstF) form a complex that binds to the JC virus transcriptional control region (JCV-TCR). Here, we examined the function of DDX1, which is expressed at much higher levels in the JCV-susceptible cell line IMR-32 than in non-susceptible cell lines. DDX1 had no effect on the replication efficiency of JCV, but overexpression of DDX1 significantly increased transactivation of the JCV promoter. Furthermore, DDX1 enhanced the expression of JCV proteins in JCV infected cells, and knockdown of DDX1 using small interfering (si) RNA suppressed the expression of JCV proteins. Our results clearly demonstrate that DDX1 regulates proliferation of JCV in vitro through transcriptional activation.
  • Tomohiro Omura, Masayuki Kaneko, Yasunobu Okuma, Yasuko Orba, Kazuo Nagashima, Ryosuke Takahashi, Noboru Fujitani, Satoshi Matsumura, Akihisa Hata, Kyoko Kubota, Karin Murahashi, Takashi Uehara, Yasuyuki Nomura
    JOURNAL OF NEUROCHEMISTRY 99 6 1456 - 1469 2006年12月 [査読有り][通常論文]
    It has been proposed that in autosomal recessive juvenile parkinsonism (AR-JP), a ubiquitin ligase (E3) Parkin, which is involved in endoplasmic reticulum-associated degradation (ERAD), lacks E3 activity. The resulting accumulation of Parkin-associated endothelin receptor-like receptor (Pael-R), a substrate of Parkin, leads to endoplasmic reticulum stress, causing neuronal death. We previously reported that human E3 HRD1 in the endoplasmic reticulum protects against endoplasmic reticulum stress-induced apoptosis. This study shows that HRD1 was expressed in substantia nigra pars compacta (SNC) dopaminergic neurons and interacted with Pael-R through the HRD1 proline-rich region, promoting the ubiquitylation and degradation of Pael-R. Furthermore, the disruption of endogenous HRD1 by small interfering RNA (siRNA) induced Pael-R accumulation and caspase-3 activation. We also found that ATF6 overexpression, which induced HRD1, accelerated and caused Pael-R degradation; the suppression of HRD1 expression by siRNA partially prevents this degradation. These results suggest that in addition to Parkin, HRD1 is also involved in the degradation of Pael-R.
  • Y Sunden, T Suzuki, Y Orba, T Umemura, M Asamoto, K Nagashima, S Tanaka, H Sawa
    ACTA NEUROPATHOLOGICA 111 4 379 - 387 2006年04月 [査読有り][通常論文]
    Polyomavirus JC virus (JCV) is the causative agent of progressive multifocal leukoencephalopathy, a fatal demyelinating disease of the central nervous system. Similar to other polyomaviruses, such as simian vacuolating virus 40 (SV40) and BK virus (BKV), JCV is also associated with human tumours. The Polyomavirus early protein large T antigen (TAg) plays a crucial role in tumour pathogenesis. An antibody to SV40 TAg (PAb416), which cross-reacts with TAgs of both JCV and BKV, has been used widely for the detection of JCV and BKV TAgs. As a consequence, it is difficult to discriminate between the TAgs of SV40, BKV and JCV by immunohistochemical analyses. In the present study, we generated JCV TAg-specific polyclonal antibodies (JCT629 and JCT652) by immunization of New Zealand white rabbits with synthetic peptides reproducing the JCV TAg carboxyl-terminal region as immunogens. Immunoblotting analyses indicated that the new antibodies bind specifically to JCV TAg, and not to those of SV40 or BKV. We also demonstrated that these antibodies can be used for immunoprecipitation, immunocytochemical analyses and immunohistochemical staining of routinely processed specimens. In conclusion, the newly generated JCV-specific TAg antibodies may be useful both in the investigation of the pathophysiological function of JCV TAg and in discriminating between Polyomavirus-related clinical samples.
  • H Hasegawa, H Sawa, MJ Lewis, Y Orba, N Sheehy, Y Yamamoto, T Ichinohe, Y Tsunetsugu-Yokota, H Katano, H Takahashi, J Matsuda, T Sata, T Kurata, K Nagashima, WW Hall
    NATURE MEDICINE 12 4 466 - 472 2006年04月 [査読有り][通常論文]
    Adult T-cell leukemia-lymphoma (ATLL) is a group of T-cell malignancies caused by infection with human T-lymphotropic virus type I (HTLV-I). Although the pathogenesis of ATLL remains incompletely understood, the viral regulatory protein Tax is centrally involved in cellular transformation. Here we describe the generation of HTLV-I Tax transgenic mice using the Lck proximal promoter to restrict transgene expression to developing thymocytes. After prolonged latency periods, transgenic mice developed diffuse large-cell lymphomas and leukemia with clinical, pathological and immunological features characteristic of acute ATLL. Transgenic mice were functionally immunocompromised and they developed opportunistic infections. Fulminant disease also developed rapidly in SCID mice after engraftment of lymphomatous cells from transgenic mice. Flow cytometry showed that the cells were CD4(-) and CD8(-), but CD44(+), CD25(+) and cytoplasmic CD3(+). This phenotype is indicative of a thymus-derived pre-T-cell phenotype, and disease development was associated with the constitutive activation of NF-kappa B. Our model accurately reproduces human disease and will provide a tool for analysis of the molecular events in transformation and for the development of new therapeutics.
  • T Suzuki, Y Okada, S Semba, Y Orba, S Yamanouchi, S Endo, S Tanaka, T Fujita, S Kuroda, K Nagashima, H Sawa
    JOURNAL OF BIOLOGICAL CHEMISTRY 280 26 24948 - 24956 2005年07月 [査読有り][通常論文]
    The human polyomavirus JC virus (JCV) is the causative agent of a fatal demyelinating disease, progressive multifocal leukoencephalopathy, and encodes six major proteins, including agnoprotein. Agnoprotein colocalizes with microtubules in JCV-infected cells, but its function is not fully understood. We have now identified fasciculation and elongation protein zeta 1 (FEZ1) as a protein that interacted with JCV agnoprotein in a yeast two-hybrid screen of a human brain cDNA library. An in vitro binding assay showed that agnoprotein interacted directly with FEZ1 and microtubules. A microtubule co-sedimentation assay revealed that FEZ1 also associates with microtubules and that agnoprotein induces the dissociation of FEZ1 from microtubules. Agnoprotein inhibited the promotion by FEZ1 of neurite outgrowth in PC12 cells. Conversely, overexpression of FEZ1 suppressed JCV protein expression and intracellular trafficking in JCV-infected cells. These results suggest that FEZ1 promotes neurite extension through its interaction with microtubules, and that agnoprotein facilitates JCV propagation by inducing the dissociation of FEZ1 from microtubules.
  • Y Okada, T Suzuki, Y Sunden, Y Orba, S Kose, N Imamoto, H Takahashi, S Tanaka, WW Hall, K Nagashima, H Sawa
    EMBO REPORTS 6 5 452 - 457 2005年05月 [査読有り][通常論文]
    The nuclear envelope is one of the chief obstacles to the translocation of macromolecules that are larger than the diameter of nuclear pores. Heterochromatin protein 1 (HP1) bound to the lamin B receptor (LBR) is thought to contribute to reassembly of the nuclear envelope after cell division. Human polyomavirus agnoprotein ( Agno) has been shown to bind to HP1 alpha and to induce its dissociation from LBR, resulting in destabilization of the nuclear envelope. Fluorescence recovery after photobleaching showed that Agno increased the lateral mobility of LBR in the inner nuclear membrane. Biochemical and immunofluorescence analyses showed that Agno is targeted to the nuclear envelope and facilitates the nuclear egress of polyomavirus-like particles. These results indicate that dissociation of HP1a from LBR and consequent perturbation of the nuclear envelope induced by polyomavirus Agno promote the translocation of virions out of the nucleus.
  • C Henmi, H Sawa, H Iwata, Y Orba, S Tanaka, K Nagashima
    Polyomavirus JC (JCV) infection causes the fatal human demyelinating disease, progressive multifocal leukoencephalopathy. Although the initial interaction of JCV with host cells occurs through direct binding of the major viral capsid protein (VP1) with cell-surface molecules possessing sialic acid, these molecules have not yet been identified. In order to isolate monoclonal antibodies which inhibit attachment of JCV, we established an immunoscreening system using virus-like particles consisting of the VP1. Using this system, among monoclonal antibodies against the cell membrane fraction from JCV-permissive human neuroblastoma IMR-32 cells, we isolated a monoclonal antibody designated as 24132 that specifically inhibited attachment and infection of JCV to IMR-32 cells. The antibody 24132 recognized a single molecule of around 60 kDa in molecular weight in the IMR-32 membrane fraction. Immunohistochemical staining with 24132 demonstrated immunoreactivity in the cell membrane of JCV-permissive cell lines and glial cells of the human brain. These results suggested that the molecule recognized by 24132 plays a role in JCV infection, and that it might participate as a receptor or a co-receptor in JCV attachment and entry into the cells. (C) 2004 Elsevier Inc. All rights reserved.
  • K Matsumoto, T Sato, S Oka, Y Orba, H Sawa, K Kabayama, J Inokuchi, H Ariga
    GENES TO CELLS 9 8 737 - 748 2004年08月 [査読有り][通常論文]
    Tenascin-X (TNX) is a member of the tenascin family of glycoproteins of the extracellular matrix. Here, we observed abnormalities in the skin of TNX-deficient mice in comparison with that of wild-type mice. Histological analysis with Oil Red O staining demonstrated that there was considerable accumulation of lipid in the skin of TNX-deficient (TNX-/-) mice. By thin-layer chromatography of total lipids, it was found that the level of triglyceride was significantly increased in TNX-/- mice. The mRNA levels of most of the lipogenic enzyme genes examined were remarkably increased in TNX-/- mice. By gas chromatography-mass spectrometry analysis of triglyceride-associated fatty acids in the skin, saturated fatty acid palmitoic acid was decreased, whereas unsaturated fatty acids palmitoleic acid and oleic acid were increased in TNX-/- mice compared with those in wild-type mice. Conversely, fibroblast cell lines transfected with TNX showed a significant decrease in the amount of triglyceride. An increase in the saturated fatty acid stearic acid and decreases in the unsaturated fatty acids palmitoleic acid, oleic acid and linoleic acid, compared to those in mock-transfected cells were also caused by over-expression of TNX. These results indicate that TNX is involved in the regulation of triglyceride synthesis and the regulation of composition of triglyceride-associated fatty acids.
  • Y Orba, H Sawa, H Iwata, S Tanaka, K Nagashima
    JOURNAL OF VIROLOGY 78 13 7270 - 7273 2004年07月 [査読有り][通常論文]
    RNA interference has been applied for the prevention of virus infections in mammalian cells but has not succeeded in eliminating infections from already infected cells. We now show that the transfection of JC virus-infected SVG-A human glial cells with small interfering RNAs that target late viral proteins, including agnoprotein and VP1, results in a marked inhibition both of viral protein expression and of virus production. RNA interference directed against JC virus genes may thus provide a basis for the development of new strategies to control infections with this polyomavirus.
  • K Matsumoto, T Minamitani, Y Orba, M Sato, H Sawa, H Ariga
    EXPERIMENTAL CELL RESEARCH 297 2 404 - 414 2004年07月 [査読有り][通常論文]
    The results of our previous study showed that tumor invasion and metastasis are promoted in extracellular matrix (ECM) tenascin-X-deficient (TNX-/-) mice via increased expression of matrix metalloproteinases (MMPs). However, little is known about the relationship between TNX deficiency and activation of MMP genes. In this study, we investigated the molecular mechanism by which TNX deficiency activates the MMP-2 gene. We examined the intracellular signaling pathways that regulate gene expression of the proteinase in isolated fibroblasts. Results of gelatin zymography showed that MMP-2 was induced to a greater extent in TNX-/- fibroblasts embedded in type I collagen than in wild-type fibroblasts. RT-PCR analysis revealed that the increased level of MMP-2 expression was caused at the transcription level. Conversely, stable overexpression of TNX in a fibroblast cell line reduced MMP-2 expression and suppressed MMP-2 promoter activity. In addition, treatment of TNX-/- fibroblasts with SP600125, a c-Jun N-terminal kinase (JNK) inhibitor, and genistein, a tyrosine kinase inhibitor, suppressed the increased level of proMMP-2 and increased MMP-2 promoter activity in TNX-/- fibroblasts. Furthermore, increased activation of JNK and tyrosine phosphorylation of certain proteins were observed in TNX-/- fibroblasts. These findings suggest that induction of MMP-2 by TNX deficiency is mediated, at least in part, through the JNK and protein tyrosine kinase phosphorylation pathway. (C) 2004 Elsevier Inc. All rights reserved.
  • T Nagashima, Y Mizutani, H Kawahara, S Maguchi, Y Terayama, T Shinohara, Y Orba, T Chuma, Y Mano, T Itoh, H Sawa, K Sakai, M Motomura, K Nagashima
    NEUROPATHOLOGY 23 3 230 - 238 2003年09月 [査読有り][通常論文]
    Paraneoplastic syndrome (PNS) with two distinct neurological features was reported in a 50-year-old man who presented initially with vertigo, ataxia, dysarthria, tremor, confusion, urinary retention and hypotension. Pulmonary X-ray findings, class IIIb sputum cytology, and positive anti-Hu antibody established the diagnosis of PNS associated with small-cell lung cancer (SCLC). Two cycles of combined chemotherapy resulted in shrinkage of the lung tumor together with complete recovery of neurological symptoms and disappearance of anti-Hu antibody. Relapse of SCLC 4 months later with re-appearance of anti-Hu antibody required additional chemotherapy and irradiation. Eight months later, when multiple liver metastasis of SCLC was noticed, muscular weakness with positive waxing phenomenon compatible with Lambert-Eaton myasthenic syndrome (LEMS) developed. Postmortem examinations revealed residual SCLC in the primary lung, and massive liver metastasis with generalized lymph node involvement, but no tumors in the CNS. In the cerebellum, there was a slight loss of Purkinje cells with torpedo formation but without apparent lymphocytic infiltration. The present PNS was unique in that the relapse of SCLC was accompanied by the appearance of anti-Hu antibody, and that initial signs of brainstem-cerebellar symptoms, encephalopathy and autonomic failure were replaced by LEMS coinciding with the tumor recurrence.
  • Y Orba, S Tanaka, H Nishihara, N Kawamura, T Itoh, M Shimizu, H Sawa, K Nagashima
    CANCER CYTOPATHOLOGY 99 4 198 - 204 2003年08月 [査読有り][通常論文]
    BACKGROUND. The demonstration of the monoclonality of immunoglobulin heavy chain (IgH) gene rearrangement is an indispensable method for the diagnosis of B-cell lymphoma as well as histocytochemical analysis. For the detection of IgH gene rearrangement, the extraction of DNA from a homogenous cell population is necessary. Recently, the laser capture microdissection (LCM) technique was shown to isolate specific cells from histopathologic specimens for molecular analysis. However, to the authors' knowledge the applicability of LCM to cytologic specimens has not yet been well established. METHODS. Using LCM, a homogenous population of B-cell lymphoma cells as both histologic sections and cytologic specimens was captured, and genomic DNA was extracted from the captured cells. IgH gene rearrangement was analyzed by the polymerase chain reaction (PCR)-based single-strand conformational polymorphism (SSCP) method. RESULTS. Genomic DNAs were extracted successfully from ethanol-fixed cytologic specimens, but cells were not captured from air-dried specimens. Using PCR-SSCP analysis, the monoclonality of the IgH gene rearrangement was detected in five cases of tissue sections among nine analyzed cases of malignant lymphoma diagnosed immunohistochemically. However, analysis of the cytologic specimens with LCM demonstrated the monoclonality of the IgH gene rearrangement in seven cases of lymphoma. CONCLUSIONS. The results of the current study suggest that the novel application of LCM to cytologic specimens occasionally exhibits high sensitivity for the detection of IgH gene rearrangement monoclonality compared with the use of histologic sections.
  • Nakagawa T, Orba Y, Nagashima K
    Nihon rinsho. Japanese journal of clinical medicine 61 Suppl 2 122 - 127 2003年02月 [査読有り][通常論文]
  • S Endo, Y Okada, Y Orba, H Nishibara, S Tanaka, K Nagashima, H Sawa
    JOURNAL OF NEUROVIROLOGY 9 10 - 14 2003年 [査読有り][通常論文]
    The human polyomavirus JC (JCV) encodes an agnoprotein that consists of 71 amino acid residues, with a molecular weight of approximately 8 kDa, from the late protein coding region. The agnoprotein of JCV shares 50% to 60% homology with those of simian virus 40 (SV40) and BK virus (BKV), and the carboxyl-terminal region of JCV agnoprotein is relatively unique. By using specific antibody to the carboxyl-terminal region of JCV agnoprotein, the authors have demonstrated that JCV agnoprotein expressed in the JCV-infected cells, where it localized predominantly in the perinuclear region of the cytoplasm, and colocalizes with the cellular cytoskeletal protein, tubulin. The results suggest that JCV agnoprotein may play a role in the stability of microtubules and the preservation of JCV infected cells via an interaction with tubulin.
  • T Nagashima, BZ Cao, N Takeuchi, T Chuma, Y Mano, M Fujimoto, M Nunomura, T Oshikiri, K Miyazaki, M Dohke, N Kashimura, T Shinohara, Y Orba, S Ishizawa, K Nagashima
    NEUROPATHOLOGY 22 4 299 - 307 2002年12月 [査読有り][通常論文]
    Clinicopathological studies were performed on the visceral organs and the sural nerve of a male patient with Churg-Strauss syndrome (CSS) in order to understand the mechanisms of peripheral nervous system damage. A 67-year-old man, with a 2-year history of bronchial asthma, developed acutely painful paraplegia and dyspnea. Laboratory data showed a leukocytosis, an elevated serum creatinine kinase (CK) and marked eosionophilia. Autoantibodies including p- and c-ANCA were negative. Electro-physiological studies revealed a severe sensory-motor neuropathy of multiple mononeuritis type. Steroid pulse therapy performed a day after biopsy of skin, muscle and sural nerve was effective in resolving his respiratory and neurological dysfunction but a perforation of an intestinal ulcer occurred which required surgical intervention. In the biopsied sural nerve and the surgically resected intestine and mesentery there was vasculitis with fibrinoid necrosis accompanied by numerous eosinophils and macrophages containing eosinophil cationic protein (ECP). These findings suggest that in addition to ischemic changes due to vasculitis some neurotoxic substances generated by the eosinophils may be involved in the development of neuropathy in CSS.
  • K Matsumoto, H Sawa, M Sato, Y Orba, K Nagashima, H Ariga
    ACTA NEUROPATHOLOGICA 104 5 448 - 454 2002年11月 [査読有り][通常論文]
    Tenascin-X (TNX) is an extracellular matrix protein that is highly expressed in the peripheral nervous system as well as muscular tissues, especially the heart and skeletal muscle. However, the expression manner and the physiological role of TNX in the peripheral nervous system have not been fully investigated. In this study, we elucidated its distribution in adult mouse sciatic nerves by immunohistochemical staining. TNX was found to be localized in the perineurium and the endoneurium of sciatic nerve fibers. To examine the physiological role of TNX, we investigated sciatic nerves of TNX-deficient mice that are viable and fertile and have no obvious deficits in general performance. The thickness of myelin sheaths and the size of the individual axons in these mice appeared normal. The ultrastructure of the sciatic nerves of TNX-deficient mice were similar to those of wild-type mice. Thus, the lack of a discernible phenotype in the sciatic nerves of TNX-deficient mice suggests that TNX has either a redundant or a very subtle function in the macromolecular organization in the peripheral nerve.
  • Y Okada, H Sawa, S Endo, Y Orba, T Umemura, H Nishihara, AC Stan, S Tanaka, H Takahashi, K Nagashima
    ACTA NEUROPATHOLOGICA 104 2 130 - 136 2002年08月 [査読有り][通常論文]
    To examine the function of JC virus (JCV) agnoprotein, we examined the brains of cases of progressive multifocal leukoencephalopathy (PML), which is caused by JCV infection, using a newly generated antibody. The antibody reacted with 8 kDa protein specific for JCV agnoprotein by Western blotting. In vitro analyses showed that JCV capsid protein VP1 and large T antigen (T-Ag) were localized in the nuclei, but that agnoprotein was mainly detected in the cytoplasm of JCV-infected cells with an occasional nuclear staining. In the PML brain, an immunoreactive signal for agnoprotein was distributed in the perinuclear areas and cytoplasmic processes with occasional punctate staining in demyelinating lesions as well as adjacent myelinated areas. Agnoprotein presented mostly in the infected oligodendrocytes and partly in the astrocytes. Using double immunostaining, agnoprotein was seen to be expressed in the cytoplasmic processes of the cells, the nuclei of which were labeled with VP1 and T-Ag, where virus particles existed. Thus, JCV agnoprotein was mostly expressed in the infected oligodendrocytes and mainly localized in the cytoplasmic processes apart from virus particles in the demyelinated lesions.
  • T Nagashima, F Sato, T Chuma, Y Mano, Sasaki, I, M Mori, T Higa, N Masauji, M Kasai, Y Orba, T Shinohara, K Nagashima
    NEUROPATHOLOGY 22 1 1 - 8 2002年03月 [査読有り][通常論文]
    In recent years a novel problem has arisen in organ transplantation medicine, namely GVHD. The nervous system has been involved mainly at the level of the CNS and this can lead to a serious outcome for the patient. In rare cases, peripheral nerves may be affected and show acute or chronic polyneuropathy, Here a case is reported of polyneuropathy associated with chronic GVHD. A 32-year-old man, suffering from chronic GVHD following an allogeneic bone marrow transplantation (BMT) for malignant lymphoma at the age of 25, developed a motor dominant polyneuropathy 5 years later. Electrophysiologic studies demonstrated the demyelinating type of polyneuropathy. Biopsy specimens from skin and skeletal muscle disclosed perivascular lymphocytic infiltrates expressing T-cell markers. The sural nerve showed a loss of myelinated nerve fibers with epineurial fibrosis and rare occurrence of T cells, but without obvious vasculitic changes. The present case suggested that polyneuropathy could develop in association with chronic GVHD in some patients with a long-standing disease course.
  • T Itoh, Y Orba, H Takei, Y Ishida, M Saitoh, H Nakamura, T Meguro, S Horita, M Fujita, K Nagashima
    MODERN PATHOLOGY 15 2 110 - 115 2002年02月 [査読有り][通常論文]
    After radiofrequency ablation (RFA), hepatocellular carcinoma undergoes complete necrosis and an ongoing necrosis that is irreversible and characterized histologically by disrupted cell outlines, homogenous cytoplasmic eosinophilia, and preserved nuclear staining, with the cells appearing quite distinct from viable cancer cells. Antibody to detect single-stranded DNA (ssDNA) specifically labeled nuclei in the setting of ongoing necrosis, but not viable tumor cells, whereas human mitochondrial antibody labeled the cytoplasm of viable cells but not cells of ongoing necrosis. The results demonstrate that RFA causes denaturation of both DNA and proteins and that the immunohistochemistry of ssDNA and mitochondrial protein is useful in detection of ongoing necrosis after RFA and provides pathological information on the validity of this procedure.
  • Yasuko Orba, Hirofumi Sawa, Kazuo Nagashima
    Brain and Nerve 54 2 101 - 109 2002年 [査読有り][通常論文]


  • 河岡, 義裕 
    集英社 2021年03月 (ISBN: 9784087211597) 315p
  • グローバル時代のウイルス感染症
    澤 洋文, 江下 優樹, 大場靖子 (担当:共著範囲:リフトバレー熱フレボウイルス感染症)
    日本医事新報社 2019年01月
  • 蚊のはなし -病気との関わり-
    大場靖子 (担当:共著範囲:蚊のうつす病気)
    朝倉書店 2017年08月


  • 多種の蚊に内在するフラビウイルスエレメント  [通常講演]
    第67回ウイルス学会 2019年10月 ポスター発表
  • Research activities of Hokkaido Univ. CZC in Zambia  [招待講演]
    筑波会議2019 2019年10月 シンポジウム・ワークショップパネル(指名)
  • ザンビアに生息する蚊から同定されたウエストナイルウイルス  [通常講演]
    第66回日本ウイルス学会学術集会 2018年10月 ポスター発表
  • 節足動物媒介性ウイルス  [招待講演]
    熱研サマースクール2018 2018年08月 公開講演,セミナー,チュートリアル,講習,講義等
  • 蚊に潜むウイルス  [招待講演]
    LOVE LABO 2018 2018年08月 公開講演,セミナー,チュートリアル,講習,講義等
  • 病原体を見える化?  [招待講演]
    WinterSchool2017@微研 2017年12月 公開講演,セミナー,チュートリアル,講習,講義等
  • An RNA virus enrichment approach for viral metagenomics using Ribonuclease R  [通常講演]
    ConBio2017 2017年12月 ポスター発表
  • Discovery of diverse mosquito-borne bunyaviruses in field-collected mosquitoes  [通常講演]
    第65回日本ウイルス学会 2017年10月 ポスター発表


  • 大場靖子, 澤洋文, 松野啓太 ウイルス 70 (1) 3 -14 2020年 
    "Arbovirus" is a term for a virus transmitted to mammals by hematophagous arthropods; arboviruses; replicate in both mammals and arthropods. Since the life cycle of arboviruses is highly dependent on arthropods, control of the arthropods (vectors) is generally considered important for the control of arbovirus infection. Various pathogens that cause diseases in the medical and veterinary fields are grouped into arboviruses with a history of their discoveries since the early 20th century. Furthermore, because of recent advances in sequencing technology, new arboviruses have been discovered one after another. Here we would like to overview the known arboviruses and their infections.
  • 田畑耕史郎, 田畑耕史郎, 鈴木忠樹, 佐野芳, 齊藤慎二, 相内章, 大場靖子, 長谷川秀樹, 長谷川秀樹, 澤洋文, 澤洋文 日本分子生物学会年会プログラム・要旨集(Web) 42nd 2019年
  • 板倉友香里, 大場靖子, 澤洋文, 澤洋文, 佐々木道仁 日本分子生物学会年会プログラム・要旨集(Web) 42nd 2019年
  • 小林進太郎, 好井健太朗, PHONGPAEW Wallaya, 武藤芽未, 平野港, 大場靖子, 澤洋文, 苅和宏明 日本分子生物学会年会プログラム・要旨集(Web) 42nd 2019年
  • 佐々木道仁, 伊藤直人, 杉山誠, 大場靖子, 澤洋文, 澤洋文 日本分子生物学会年会プログラム・要旨集(Web) 42nd 2019年
  • 鳥居志保, 鳥居志保, 大場靖子, 佐々木道仁, 和田雄治, HOBSON-PETERS Jody, HALL Roy A., 澤洋文 日本分子生物学会年会プログラム・要旨集(Web) 42nd 2019年
  • 大場靖子, HANG’OMBE Bernard M., MWEENE Aaron S., 佐々木道仁, 江下優樹, 澤洋文, 澤洋文, 澤洋文 日本分子生物学会年会プログラム・要旨集(Web) 42nd 2019年
  • 鳥居志保, 鳥居志保, 大場靖子, 佐々木道仁, 和田雄治, HOBSON-PETERS Jody, HALL Roy, 澤洋文, 澤洋文, 澤洋文 日本ウイルス学会学術集会プログラム・予稿集(Web) 67th 2019年
  • 佐々木道仁, 伊藤直人, 杉山誠, GONZALEZ Gabriel, 伊藤公人, 伊藤公人, 大場靖子, 澤洋文, 澤洋文 日本ウイルス学会学術集会プログラム・予稿集(Web) 67th 2019年
  • 佐藤彰彦, 佐藤彰彦, 登治謙, 鳥羽晋輔, 鳥羽晋輔, 上村健太朗, 上村健太朗, 吉田立, 宍戸貴雄, 大場靖子, 澤洋文, 澤洋文 日本ウイルス学会学術集会プログラム・予稿集(Web) 67th 2019年
  • 大場靖子, HANG’OMBE Bernard M., MWEENE Aaron S., 佐々木道仁, 江下優樹, 澤洋文, 澤洋文, 澤洋文 日本ウイルス学会学術集会プログラム・予稿集(Web) 67th 2019年
  • 梶原将大, CHANGULA Katendi, HANG’OMBE Bernard, 播磨勇人, 宮本洋子, 衛藤芳樹, 奥谷公亮, 磯野真央, 吉田玲子, 邱永晋, 森(梶原)亜紀奈, 大場靖子, 澤洋文, 澤洋文, 小川寛仁, SIMULUNDU Edgar, SQUARRE David, MUKONKA Victor, MWEENE Aaron, 高田礼人, 高田礼人 日本ウイルス学会学術集会プログラム・予稿集(Web) 67th 2019年
  • 播磨勇人, 鳥居志保, 邱永晋, 梶原将大, 衛藤芳樹, 大場靖子, 江下優樹, ハンゴンベ バーナード, 好井健太朗, シムンザ マーティン, 高田礼人, 澤洋文 日本ウイルス学会学術集会プログラム・予稿集(Web) 67th 2019年
  • 上村健太朗, 上村健太朗, 鳥羽晋輔, 鳥羽晋輔, 登治謙, 吉田立, 宍戸貴雄, 佐々木道仁, 伊藤直人, 大場靖子, 澤洋文, 澤洋文, 佐藤彰彦, 佐藤彰彦 日本ウイルス学会学術集会プログラム・予稿集(Web) 67th 2019年
  • 鳥羽晋輔, 鳥羽晋輔, 登治謙, 上村健太朗, 上村健太朗, 垰田善之, 佐藤健司, 吉田立, 宍戸貴雄, 大場靖子, 澤洋文, 澤洋文, 佐藤彰彦, 佐藤彰彦 日本ウイルス学会学術集会プログラム・予稿集(Web) 67th 2019年
  • 松野啓太, 松野啓太, 中尾亮, 草木迫浩大, 大場靖子, 澤洋文, 澤洋文 日本獣医学会学術集会講演要旨集 162nd 2019年
  • ウエストナイルウイルス感染で起こるオートファジーの抑制と神経病態形成の関係
    小林 進太郎, 好井 健太朗, Wallaya Phongpaew, 武藤 芽未, 平野 港, 大場 靖子, 澤 洋文, 苅和 宏明 日本獣医学会学術集会講演要旨集 161回 395 -395 2018年08月 [査読無し][通常論文]
  • 江下 優樹, 和田 雄治, 林田 京子, 山岸 潤也, 杉本 千尋, 佐々木 道仁, 大場 靖子, 澤 洋文, 飛弾野 真也, 神山 長慶, 小林 隆志, 高崎 智彦, 加藤 文博, 田島 茂, 倉根 一郎, 林 昌宏 衛生動物 69 (Suppl.) 51 -51 2018年03月 [査読無し][通常論文]
  • ウエストナイルウイルスのカプシドタンパク質によるオートファジーの抑制による変性タンパク質の蓄積と神経病態形成についての解析
    小林 進太郎, 好井 健太朗, Phonqphaew Wallaya, 武藤 芽未, 平野 港, 大場 靖子, 澤 洋文, 苅和 宏明 生命科学系学会合同年次大会 2017年度 [3P -1110] 2017年12月 [査読無し][通常論文]
  • 澤洋文, 澤洋文, 佐々木道仁, 大場靖子 ウイルス 67 (2) 151‐160 2017年12月 [査読無し][通常論文]
  • In vitroでの狂犬病ウイルスに対する5-エチニル-1-リボフラノシルイミダゾール-4-カルボキサミド(EICAR)の抗ウイルス活性に関する検討(Examination of antiviral activity of 5-ethynyl-1-ribofuranosylimidazole-4-carboxamide(EICAR) against rabies virus in vitro)
    Anindita Paulina Duhita, 佐々木 道仁, 伊藤 直人, 杉山 誠, 南川 典昭, 周東 智, 乙黒 聡子, 市川 聡, 松田 彰, 前仲 勝実, 大場 靖子, 澤 洋文 日本獣医学会学術集会講演要旨集 160回 390 -390 2017年08月 [査読無し][通常論文]
  • Examination of antiviral activity of 5-ethynyl-1-ribofuranosylimidazole-4-carboxamide(EICAR) against rabies virus in vitro(和訳中)
    Anindita Paulina Duhita, 佐々木 道仁, 伊藤 直人, 杉山 誠, 南川 典昭, 周東 智, 乙黒 聡子, 市川 聡, 松田 彰, 前仲 勝実, 大場 靖子, 澤 洋文 日本獣医学会学術集会講演要旨集 160回 390 -390 2017年08月 [査読無し][通常論文]
  • 【One Healthの視点からみた感染症の現状と対策】 野生動物が保有するウイルスを対象とする研究
    佐々木 道仁, 大場 靖子, 澤 洋文 最新医学 72 (4) 508 -512 2017年04月 [査読無し][通常論文]
  • 江下優樹, SRISAWAT Raweewan, RUNTUWENE Lucky Ronald, 飛弾野真也, 林田京子, 大場靖子 臨床と微生物 43 (6) 701‐707 2016年11月 [査読無し][通常論文]
  • ウエストナイルウイルスの粒子放出過程におけるRab8bタンパク質の役割
    小林 進太郎, 鈴木 忠樹, 川口 晶, Phongphaew Wallaya, 好井 健太朗, 苅和 宏明, 大場 靖子, 澤 洋文 日本獣医学会学術集会講演要旨集 159回 409 -409 2016年08月 [査読無し][通常論文]
  • 佐々木道仁, アニンディタ パウリナ, 伊藤直人, 杉山誠, 福原秀雄, 尾瀬農之, 前仲勝実, 大場靖子, 澤洋文, 澤洋文 日本分子生物学会年会プログラム・要旨集(Web) 39th ROMBUNNO.2P‐0314 (WEB ONLY) 2016年 [査読無し][通常論文]
  • ウエストナイルウイルス感染による変性タンパク質蓄積機構の解析
    小林 進太郎, Phongphaew Wallaya, 好井 健太朗, 平野 港, 武藤 芽未, 大場 靖子, 澤 洋文, 苅和 宏明 日本生化学会大会・日本分子生物学会年会合同大会講演要旨集 88回・38回 [1P1135] -[1P1135] 2015年12月 [査読無し][通常論文]
  • 澤洋文, 鈴木忠樹, 大場靖子 プリオン病及び遅発性ウイルス感染症の分子病態解明・治療法開発に関する研究 平成26年度 委託業務成果報告書 67 -70 2015年 [査読無し][通常論文]
  • 澤 洋文, 小林 進太郎, 鈴木 忠樹, 大場 靖子 ウイルス 64 (1) 25 -34 2014年06月 [査読無し][通常論文]
    ポリオーマウイルスはポリオーマウイルス科に属する哺乳類動物由来のOrthopolyomavirusとWukipolyomavirus、及び鳥類由来のAvipolyomavirusに分類されている。我々は疫学研究を通じて新規のポリオーマウイルスであるMastomys Polyoamvirus(MasPyV)及びVervet monkey Polyoamvirus-1(VmPyV-1)を単離し、そのゲノムがコードするウイルスタンパク質の機能解析を実施した。更に、ヒトポリオーマウイルスであるJC polyomavirus(JCPyV)についての基礎研究を推進し、最近、早期タンパク質であるLarge T抗原の感染細胞における機能解析、後期タンパク質であるVP1のシステイン残基の粒子形成への影響、及び後期タンパク質であるAgnoのウイルス粒子の細胞外放出機構に対する影響について知見を得たのでその内容を紹介する。(著者抄録)
  • K. Miura, Y. Wakayama, M. Tanino, Y. Orba, H. Sawa, M. Hatakeyama, S. Tanaka, H. Sabe, N. Mochizuki Oncogene 32 (45) 5292 -5301 2013年11月07日 [査読無し][通常論文]
    Shp2 is a positive regulator for Erk activation downstream of receptor tyrosine kinases for growth factors. It has been controversial how Shp2 induces Erk activation. We here demonstrate that EphA2 is responsible for Shp2-mediated Erk activation by phosphorylating Tyr542 and Tyr580 of Shp2 in the cells stimulated with growth factors. In NMuMG mammary epithelial cells stimulated with hepatocyte growth factor (HGF), HGF-dependent Erk phosphorylation was prolonged only in the presence of EphA2. This Erk activation paralleled the phosphorylation of Tyr542/580 of Shp2 and the association of Grb2 with Shp2, suggesting the positive signal involving Grb2 signal to activate Ras-Erk pathway. Immunohistochemical studies of mammary cancer specimens revealed that the cancer progression was associated with both Tyr580 phosphorylation of Shp2 and increased expression of EphA2, which were also correlated with increased Erk phosphorylation. Overexpression of either Shp2Thr468Met (a phosphatase- defective mutant found in Lentigines, Electrocardiographic abnormalities, Ocular hypertelorism, Pulmonary stenosis, Abnormal genitalia, Retardation of growth and sensorineural Deafness (LEOPARD) syndrome) or Shp2Asn308Asp (a phosphatase-active mutant found in Noonan syndrome) with EphA2 exhibited comparable activation of Erk and stronger activation than wild-type Shp2, suggesting the phosphatase-independent Erk activation. Expression of Shp2Thr468Met with Tyr542/580Phe mutations resulted in the suppression of Erk activation. Phosphatase-active and -inactive, and wild-type Shp2s bound equally to Grb2, suggesting that phosphorylation of Tyr542/580 of Shp2 was essential but not sufficient for Shp2-mediated Erk activation. We found that Gab1 (Grb2-associated binder 1) was involved in the mutant Shp2-mediated Erk activation. Zebrafish injected with Shp2Thr468Met mRNA showed cardiac edema, whereas those depleted of EphA2b showed less phenotype, suggesting that EphA2 might partly account for the phenotype of LEOPARD syndrome. Collectively, tyrosine phosphorylation of Shp2 by EphA2 contributes to the phosphatase-independent Shp2-mediated activation of Erk and might be involved in Shp2-associated diseases. © 2013 Macmillan Publishers Limited.
  • 鈴木忠樹, 澤洋文, 大場靖子, 片野晴隆, 佐藤由子, 長谷川秀樹, 長嶋和郎 日本病理学会会誌 102 (1) 207 2013年04月26日 [査読無し][通常論文]
  • 大場靖子, 石井秋宏, トーマス 由佳, 小川寛人, 中村一郎, 木村享史, 森川茂, 西條政幸, 澤洋文 日本ウイルス学会学術集会プログラム・抄録集 60th 443 2012年10月31日 [査読無し][通常論文]
  • 大場靖子, 小林進太郎, 中村一郎, 石井秋宏, 木村享史, 澤洋文 日本ウイルス学会学術集会プログラム・抄録集 58th 445 2010年10月15日 [査読無し][通常論文]
  • Tadaki Suzuki, Yasuko Orba, Yoshinori Malcino, Yuki Okada, Yuji Sunden, Takashi Kimura, Hideki Hasegawa, Tetsutaro Sata, William W. Hall, Hirofumi Sawa JOURNAL OF NEUROVIROLOGY 16 84 -84 2010年10月 [査読無し][通常論文]
  • Yasuko Orba, Tadaki Suzuki, Takashi Kimura, Hirofumi Sawa JOURNAL OF NEUROVIROLOGY 16 64 -65 2010年10月 [査読無し][通常論文]
  • A. Kawaguichi, Hidekatsu, I, H. Hasegawa, H. Sawa, M. Ogata, T. Tsuji, T. Kimura, T. Sata, W. W. Hall, Y. Orba AIDS RESEARCH AND HUMAN RETROVIRUSES 25 (11) 1212 -1212 2009年11月 [査読無し][通常論文]
  • 川口晶, 辻隆裕, 大場靖子, 木村享史, 相内章, 伊波英克, 緒方正男, 佐多徹太郎, 澤洋文, 長谷川秀樹 日本ウイルス学会学術集会プログラム・抄録集 57th 445 2009年10月01日 [査読無し][通常論文]
  • Tadaki Suzuki, Yasuko Orba, Yuji Sunden, Takashi Kimura, Hirofumi Sawa JOURNAL OF NEUROVIROLOGY 15 96 -97 2009年 [査読無し][通常論文]
  • 川口晶, 大場靖子, 木村享史, 伊波英克, 緒方正男, 辻隆裕, 佐多徹太郎, 澤洋文, 長谷川秀樹 日本ウイルス学会学術集会プログラム・抄録集 56th 247 2008年10月01日 [査読無し][通常論文]
  • 川口晶, 大場靖子, 木村享史, 伊波英克, 緒方正男, 佐多徹太郎, 澤洋文, 長谷川秀樹 補体シンポジウム講演集 45th 179 2008年07月 [査読無し][通常論文]
  • 【進行性多巣性白質脳症の新しい展開 PMLが治る時代へ向けて】 JCウイルスの最近の基礎的知見
    澤 洋文, 鈴木 忠樹, 大場 靖子, 寸田 祐嗣, 長嶋 和郎 BRAIN and NERVE: 神経研究の進歩 59 (2) 101 -108 2007年02月 [査読無し][通常論文]
  • Tadaki Suzuki, Yuki Okada, Yasuko Orba, Yuji Sunden, Takashi Kimura, Kazuo Nagashima, Hirofumi Sawa JOURNAL OF NEUROVIROLOGY 13 128 -128 2007年 [査読無し][通常論文]
  • Yasuko Orba, Yuji Sunden, Tadaki Suzuki, Takashi Kimura, Shinya Tanaka, Kazuo Nagashima, Hirofumi Sawa JOURNAL OF NEUROVIROLOGY 13 109 -110 2007年 [査読無し][通常論文]
  • Tadaki Suzuki, Satoko Yamanouchi, Yuji Sunden, Yasuko Orba, Shinya Tanaka, Takashi Kimura, Hirofumi Sawa JOURNAL OF NEUROVIROLOGY 13 127 -127 2007年 [査読無し][通常論文]
  • H Hasegawa, H Sawa, M Lewis, Y Orba, T Sata, T Kurata, K Nagashima, N Sheehy, WW Hall AIDS RESEARCH AND HUMAN RETROVIRUSES 21 (5) 454 -455 2005年05月 [査読無し][通常論文]
  • Hirofumi Sawa, Tadaki Suzuki, Yuki Okada, Yasuko Orba, Yuji Sunden, Shingo Semba, Kazuo Nagashima JOURNAL OF NEUROVIROLOGY 14 63 -63 2005年 [査読無し][通常論文]
  • Tadaki Suzuki, Hirofumi Sawa, Yuki Okada, Yasuko Orba, Shingo Semba, Kazuo Nagashima JOURNAL OF NEUROVIROLOGY 10 131 -131 2004年 [査読無し][通常論文]
  • C. Henmi, H. Sawa, Y. Orba, S. Tanaka, K. Nagashima JOURNAL OF NEUROVIROLOGY 14 42 -42 2004年 [査読無し][通常論文]
  • H. Sawa, Y. Okada, T. Suzuki, Y. Orba, Y. Sunden, C. Henmi, S. Semba, H. Takahashi, S. Tanaka, K. Nagashima JOURNAL OF NEUROVIROLOGY 14 33 -33 2004年 [査読無し][通常論文]
  • 除負荷がin situ凍結解凍処理膝蓋腱のサイトカイン発現に与える効果
    内田 尚哉, 遠山 晴一, 松本 秀男, 戸山 芳昭, 大場 靖子, 長嶋 和郎, 安田 和則 膝 28 (2) 72 -75 2003年12月 [査読無し][通常論文]
  • 除負荷後の再負荷が膝蓋腱の力学的特性と線維芽細胞におけるサイトカイン発現に与える効果
    内田 尚哉, 遠山 晴一, 松本 秀男, 戸山 芳昭, 大場 靖子, 長嶋 和郎, 安田 和則 日本臨床バイオメカニクス学会誌 24 77 -82 2003年11月 [査読無し][通常論文]
  • 【新世紀の感染症学 ゲノム・グローバル時代の感染症アップデート】 グローバル時代の感染症学 ウイルス感染症 中枢神経系疾患 JCウイルス感染症(進行性多巣性白質脳症)
    中川 智子, 大場 靖子, 長嶋 和郎 日本臨床 61 (増刊2 新世紀の感染症学(上)) 122 -127 2003年02月 [査読無し][通常論文]
  • AC Stan, Y Okada, H Sawa, S Endo, Y Orba, T Umemura, H Nishihara, S Tanaka, H Takahashi, K Nagashima ACTA NEUROPATHOLOGICA 104 (5) 570 -570 2002年11月 [査読無し][通常論文]
  • 大場靖子, 西原広史, 田中伸哉, 沢洋文, 伊藤智雄, 長嶋和郎 日本病理学会会誌 91 (1) 298 2002年02月28日 [査読無し][通常論文]
  • JC virusの分子神経病理学
    大場 靖子, 澤 洋文, 長嶋 和郎 脳と神経 54 (2) 101 -109 2002年02月 [査読無し][通常論文]
  • 除負荷がラット膝蓋腱の力学的特性とTransforming Growth Factor-βの発現に与える効果に関する解析
    内田 尚哉, 遠山 晴一, 安田 和則, 松本 秀男, 戸山 芳昭, 大場 靖子, 長嶋 和郎 膝 26 184 -188 2001年12月 [査読無し][通常論文]
  • 除負荷が膝蓋腱の力学的特性とサイトカイン発現に与える効果
    内田 尚哉, 遠山 晴一, 安田 和則, 大場 靖子, 長嶋 和郎, 松本 秀男, 戸山 芳昭 日本整形外科学会雑誌 75 (8) S1111 -S1111 2001年08月 [査読無し][通常論文]
  • S Suzuki, H Sawa, R Komagome, Y Orba, M Yamada, Y Okada, Y Ishida, H Nishihara, S Tanaka, K Nagashima VIROLOGY 286 (1) 100 -112 2001年07月 [査読無し][通常論文]
    To investigate the early events of JC virus (JCV) infection, including attachment, penetration, transport to the nuclei, and replication of the virus, we analyzed the susceptibility of 15 different cell lines to infection using a semiquantitative polymerase chain reaction (PCR) assay, in situ hybridization, laser scanning confocal microscopy, and a viral replication assay. The cell lines examined were human permissive and nonpermissive cells as well as cells of monkey and mouse origin. JCV entry into the nuclei of the all cell lines was observed within 10 min after inoculation, demonstrating that the virus receptor is widely distributed among mammalian cells. inhibition of viral entry by an anti-JCV VP1 antibody and sialidase treatment to remove sialic acid residues, which are considered a candidate for the JCV receptor, suggested that VP1 may interact with the cellular surface sialic acid. In addition, chlorpromazine, a clathrin-dependent pathway inhibitor, significantly suppressed entry of JCV into nuclei. In spite of the broad spectrum of cells susceptible to JCV entry, replication of the virus occurred exclusively in human neuroblastoma cell lines. These results suggest that whereas JCV can enter a wide variety of cell types and localize to the nuclei, cell-specific intranuclear mechanisms are required for virus replication. (C) 2001 Academic Press.
  • 岡田由紀, 沢洋文, 遠藤秀一, 大場靖子, 西原広史, 田中伸哉, 長嶋和郎 日本病理学会会誌 90 (1) 349 2001年03月01日 [査読無し][通常論文]
  • 大場靖子, 西原広史, 伊藤智雄, 清水道生, 藤田美とし, 長嶋和郎 日本臨床細胞学会雑誌 39 327 2000年09月22日 [査読無し][通常論文]
  • H Sawa, Y Okada, S Tanaka, Y Orba, S Endo, M Sasada, Y Hara, M Shintaku, K Nagashima BRAIN PATHOLOGY 10 (4) 757 -757 2000年09月 [査読無し][通常論文]
  • 自家移植膝蓋腱へ浸潤する外来性細胞は生理的力学環境下においてもIII型コラーゲンを産生する
    遠山 晴一, 安田 和則, 東 裕隆, 大場 靖子, 長嶋 和郎 日本整形外科学会雑誌 73 (8) S1846 -S1846 1999年08月 [査読無し][通常論文]


  • 国立研究開発法人科学技術振興機構:ムーンショット型研究開発事業
    研究期間 : 2020年12月 -2024年03月 
    代表者 : 大場 靖子
  • 昆虫特異的ウイルスによるアルボウイルス制御
    日本学術振興会:科学研究費助成事業 挑戦的研究(萌芽)
    研究期間 : 2020年07月 -2023年03月 
    代表者 : 大場 靖子
  • 日本学術振興会:科学研究費助成事業 基盤研究(B)
    研究期間 : 2019年04月 -2023年03月 
    代表者 : 松野 啓太, 大場 靖子, 梶原 将大
  • Development of small compounds for pan-arenavirus therapy
    国立研究開発法人日本医療研究開発機構:地球規模保健課題解決推進のための研究事業 日米医学協力計画の若手・女性育成のための日米共同研究公募
    研究期間 : 2021年10月 -2023年03月
  • フラビウイルス感染症における抗原特異的免疫応答の網羅的評価法の開発および重症化リスク選定とワクチン開発に向けた応用に関する研究
    研究期間 : 2020年07月 -2023年03月
  • 日本学術振興会:科学研究費助成事業 新学術領域研究(研究領域提案型)
    研究期間 : 2016年06月 -2021年03月 
    代表者 : 澤 洋文, 松野 啓太, 中尾 亮, 大場 靖子
    本計画研究は、吸血性節足動物の内在性ウイルス (エレメント)が宿主に及ぼす影響、及び節足動物内の微生物叢における役割を解明することを目的とし、平成29年度に引き続き、1)新規内在性フラビウイルスエレメント・フレボウイルスの同定、2)蚊内在性フラビウイルスエレメント・マダニ内在性フレボウイルスの機能・動態解析、3)微生物叢の解析と節足動物実験室内コロニーの樹立、4)蚊・マダニに共生する新規ウイルスの同定と機能解析、の4項目を実施している。平成30年度の実施実績は下記の通り。 1) 日本国内、シエラレオネ、ザンビア、ボリビアにおいて採集した蚊、マダニを用いてウイルス遺伝子のスクリーニングを実施した。内在性フラビウイルスを保有する蚊種を新たに同定し、遺伝子解析、性状解析を実施した。マダニ中から検出されたフレボウイルスの遺伝子配列と既知のフレボウイルス遺伝子配列との相同性を解析し、系統樹解析によりウイルスの進化およびマダニとの共進化に関する新たな知見を得た。 2)および3) 内在性フラビウイルスエレメントに対するdsRNAを作製し、ネッタイシマカ由来細胞、およびネッタイシマカ継代個体に導入し、遺伝子発現抑制効果を検証した。また、マダニに内在する新規フレボウイルスのRNAポリメラーゼ、および核タンパク質の活性を、既存のダニ媒介性フレボウイルスミニゲノムアッセイ系を用いて評価した。 3) 新たに3種のマダニについて実験室内コロニーを樹立した。また、17種のマダニについてミトコンドリアゲノムの遺伝子配列を決定し、系統解析を行った。 4) 野外で採集した蚊・マダニを用いて、メタゲノム解析および細菌・ウイルス分離培養を試みた。野外で採集したマダニのミトゲノム情報による集団遺伝構造解析を実施した。
  • Virome解析による中南米・東南アジアに潜在する病原性ウイルスの探索
    日本学術振興会:科学研究費助成事業 基盤研究(B)
    研究期間 : 2016年04月 -2020年03月 
    代表者 : 澤 洋文, 大場 靖子, 佐々木 道仁
    本研究は、現在申請者が有している国際ネットワークを活用し、調査フィールドを線として繋げ、Virome解析手法等を用いて、新興・再興感染症の原因となる新規及び既知の病原体の分布状況を把握すること、得られた情報を既得の情報と比較することにより病原性ウイルスの分布・進化・生活環を把握することを目指す。 平成30年10月17日から27日にかけて、新たな調査地域として南米に位置するボリビアを共同研究者研究分担者の大場靖子講師と共に訪問し、現地に生息する蚊、およびマダニを採集した。 現地での活動は、Gabriel Rene Moreno大学の獣医学部の川森先生、副学長のPereira教授、Ariel研究員との共同研究で実施し、現地JICA海外協力隊の田中さん、松尾さんにも協力を得て、ボリビア北部のアマゾン川流域のトリニダ、サンタクルス近郊のアンブロ国立公園、日本人移住地域であるサンファンの農場において、蚊、ダニを採集した。蚊は、捕虫網、CDCトラップ、およびBGセンチネルトラップを用いて、宿舎の周囲、また、密林で採集した。その結果、Psorophora属を含む計2,214匹のメスの蚊を捕獲した。その後、冷凍して死んだ蚊を北海道大学人獣共通感染症リサーチセンターに輸送し、RNAを抽出し、フラビウイルス、アルファウイルス、ブニヤウイルス等をRT-PCR法を用いて解析した。その結果、新規ウイルスを8種同定し、1種の新規ウイルスを単離した。現在得られたゲノム情報を用いて分子進化学的解析を実施し、他の地域で得られている情報と比較している段階である。 また、インドネシアのボゴール大学の獣医学部の副部長であるAgus Setiyono教授が、平成30年10月に北大人獣共通感染症リサーチセンターを訪問し、次年度の研究の打ち合わせを実施した。
  • 文部科学省:科学研究費補助金(基盤研究(C))
    研究期間 : 2015年 -2018年 
    代表者 : 大場 靖子
  • 日本学術振興会:科学研究費助成事業 基盤研究(B)
    研究期間 : 2012年04月 -2016年03月 
    代表者 : 澤 洋文, 大場 靖子, 石井 秋宏
    本研究は、野生動物の腸管から採集した糞便検体から、ウイルスゲノムを濃縮する方法を確立し、Virome解析を実施し、ヒトから単離されたブファウイルスに相同性を有する新規ブファウイルス(Mpulungu bufavirus)を検出することに成功した。また、解析により得られたブファウイルスのゲノム配列を基にしたnested PCR法を構築し、野生動物由来の536検体を用いて、ブファウイルスの感染状況を検索した結果、ジネズミ類の約1/3(17/49=34.7%)にブファウイルスのゲノムを検出した。本検出系はブファウイルスのスクリーニングに有用であることを明らかにした。
  • 文部科学省:科学研究費補助金(若手研究(B))
    研究期間 : 2011年 -2013年 
    代表者 : 大場 靖子
    本研究は、ヒトポリオーマウイルスであるJCウイルス(JCV)が発現する長鎖RNAの機能を明らかにし、それらが宿主細胞内にてウイルス増殖を制御するメカニズムを解明することを目的としている。JCVゲノムから転写されていることが判明した10kb前後の後期遺伝子方向の長鎖RNAの機能を解析するため、長鎖RNAをin vitroで合成しウイルスゲノムと共に細胞内に導入した結果、ウイルスmRNAの発現に顕著な変化は認められなかった。また、長鎖RNAのノンコーディング領域に対するsiRNAを作成し発現抑制を試みたが、十分な抑制効果が確認できなかった。後期遺伝子方向のRNAを詳細に解析した結果、Agnoproteinのコーディング領域内約120bpの繰り返し配列が様々な数で生じていることが判明した。このことから約5kbのRNAスプライシングが数回にわたり起こっていると考えられた。このスプライシングがウイルス遺伝子発現に与える影響について今後検討を行う。こうしたウイルス遺伝子の転写、翻訳に関わる細胞内因子を探索するため、siRNAライブラリーを用いた網羅的解析を行う予定である。この解析に用いるレポーターウイルスを作製するため、後期遺伝子のVP2、VP3、VP1領域をそれぞれGFPに置換したウイルスゲノムを作成し、蛍光タンパク質発現、ゲノム複製、他のウイルスタンパク質発現の効率を比較検討した。IMR-32細胞では3種類のレポーターウイルスはGFPを発現し、ゲノム複製も確認できた。これらのレポーターゲノムの早期タンパク質TAgの開始コドンを停止コドンに置換したものでは、GFP発現が顕著に低下したことから、これらのレポーターウイルスはゲノム複製および早期、後期タンパク質発現を反映するものと考えられた。
  • 文部科学省:科学研究費補助金(若手研究(スタートアップ))
    研究期間 : 2008年 -2009年 
    代表者 : 大場 靖子
  • ATLモデルマウスを用いたT-cell腫瘍化機構の解明と治療法の開発
    日本学術振興会:科学研究費助成事業 特別研究員奨励費
    研究期間 : 2005年 -2007年 
    代表者 : 大場 靖子
    HTLV-1 Taxトランスジェニックマウスで発症するT-cell腫瘍は、ATL患者由来の腫瘍細胞と同様にアポトーシス抑制因子であるsurvivinの発現が顕著に亢進していることから、これまでにsurvivinを標的とした腫瘍細胞の増殖抑制の検討を行ってきた。HMG-CoA還元酵素阻害剤であるスタチン系薬剤は高脂血症治療薬として臨床で広く用いられているが、白血病細胞をはじめとした多くの腫瘍細胞でapoptosisを誘導することが報告されている。スタチンの一つであるロバスタチンはsurvivinの発現を抑制効果、apoptosis誘導効果を検討した。本マウス由来のT-cell腫瘍細胞を培養し、ロバスタチン(5,10,20μM)またはDMSO(control)を培養液中に加え、48時間後に細胞を回収しapoptosisの測定を行った。その結果、ロバスタチンの濃度依存性にsurvivinのタンパク質発現量が低下し、それに伴いcaspase3の活性化が見られ、Annexin-Vに陽性のapoptosis細胞が増加することが明らかとなった。また、Tax発現細胞でのsurvivin発現増加はNF-kB経路の活性化を介していることから、IkBのリン酸化をimmunoblotにより検討した結果、ロバスタチンの濃度依存性にIkBのリン酸化が低下していた。このことから、ロバスタチンはNF-kBの活性化を抑制し、survivinの発現を低下させる可能性が示唆された。今後、腫瘍細胞を腹腔内接種したSCIDマウスまたはTaxトランスジェニックマウスを用いて、ロバスタチンのin vivoにおける効果を検討する予定である。



  • 人獣共通感染症対策専門特論
    開講年度 : 2020年
    課程区分 : 博士後期課程
    開講学部 : 獣医学研究科
  • 感染病理学特論
    開講年度 : 2020年
    課程区分 : 博士後期課程
    開講学部 : 国際感染症学院
    キーワード : 病理、感染症、細胞応答
  • 人獣共通感染症対策専門特論
    開講年度 : 2020年
    課程区分 : 博士後期課程
    開講学部 : 国際感染症学院

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