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有泉 拓馬 (アリイズミ タクマ)
| 人獣共通感染症国際共同研究所 分子病態・診断部門 | 博士研究員 |
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■ 受賞- 2025年10月, 北大・部局横断シンポジウム実行委員会, ベストプレゼンター賞
ザンビア共和国に生息する蚊から分離されたレオウイルスの性状解析
有泉拓馬 - 2024年10月, 日本獣医学会, 日本獣医学会学術集会優秀発表賞
新規オルソナイロウイルス（エゾウイルス）感染症の病理学的解析および治療薬探索を目的とした致死感染マウスモデルの樹立
有泉拓馬, 53276353
- Universal and quantitative detection of double-stranded RNAs as a signature of pan-virus infections using a luciferase-based biosensor.
Michihito Sasaki; Eri Fujii; Satoko Sasaki; Takuma Ariizumi; Kei Konishi; Akihiko Sato; William W Hall; Hirofumi Sawa; Yasuko Orba
Journal of biological engineering, 20, 1, 11, 11, 2025年12月16日, ［国際誌］
英語, 研究論文（学術雑誌）, BACKGROUND: Infections with various RNA viruses and certain DNA viruses may produce double-stranded RNA (dsRNA) during replication, which trigger host innate immune responses. Immunoassays using anti-dsRNA antibodies have been widely employed to detect viral dsRNA. In this study, we used a luciferase-based dsRNA biosensor for viral dsRNA detection, which consists of protein kinase R (PKR)-derived dsRNA binding domains fused to split luciferase subunits and is available as part of a commercial system. RESULTS: We demonstrate the use of the dsRNA biosensor to measure viral dsRNA in RNA specimens extracted from cells infected with Japanese encephalitis virus (JEV). Moreover, the biosensor reacts to a broad-spectrum of dsRNAs from infection with representatives of various viral families including positive- and negative-sense single-stranded RNA (ssRNA) viruses, dsRNA viruses, and DNA viruses. We validated the specific interaction between the dsRNA biosensor and viral RNA including subgenomic flavivirus RNA (sfRNA) through RNA immunoprecipitation. Additionally, we observed luminescence signals directly from lysates of JEV-infected cells after cell lysis and phase separation with Triton X-114. Finally, we used the biosensor to assess the activity of antiviral compounds. CONCLUSIONS: Our results demonstrate that the luciferase-based dsRNA biosensor offers a simple, homogeneous, and high-throughput platform for quantifying viral replication, presenting a promising alternative to antibody-based dsRNA detection methods. - Spatial gene expression analysis reveals pathological niches in Japanese encephalitis virus neuroinvasion
Yasuko Orba; Yukie Kashima; Koshiro Tabata; Yukari Itakura; Takuma Ariizumi; William W. Hall; Hirofumi Sawa; Yutaka Suzuki; Michihito Sasaki
Proceedings of the National Academy of Sciences, 2025年10月28日
研究論文（学術雑誌） - Mosquito-borne alphaviruses in Zambia: Isolation and characterization of Eilat and Sindbis viruses.
De'Sean Mears C; Tabata K; Ariizumi T; Hang'ombe BM; Qiu Y; Harima H; Kajihara M; Hall WW; Sasaki M; Sawa H; Orba Y
Virus research, 2025年07月07日
研究論文（学術雑誌）, Alphaviruses in the family Togaviridae include zoonotic arthropod-borne viruses, including Sindbis virus (SINV), chikungunya virus, as well as insect-specific viruses such as Eilat virus (EILV). Previous investigations of alphaviruses in Zambia have identified a novel insect-specific alphavirus, Mwinilunga alphavirus in mosquitoes. Further ongoing surveillance resulted in the isolation of EILV and SINV for the first time in Zambia. Here, these alphaviruses were characterized in terms of growth kinetics in cells, and molecular phylogenetic relatedness to other alphaviruses. Zambian EILV (strain zmq19_M44) exhibited a close phylogenetic relationship with other insect-specific alphaviruses and shared a close nucleotide identity to those of EILV isolate (90.4 %) and Mwinilunga alphavirus (75.5 %). EILV zmq19_M44 attained a saturating titer in C6/36 cells at 6-8-days post infection but was unable to replicate in mammalian cells. Phylogenetic analysis revealed the Zambian SINV (strain zmq17_M115) belongs in Clade D of SINV Genotype 1 along with the Kenyan isolate BONI 584 from Central Africa. The growth of the SINV zmq17_M115 was comparable to that of the prototype SINV strain AR339 in mammalian cells but was statistically different in insect cells. Our findings will contribute to public health measures for the control of alphaviral diseases in Zambia. - Transboundary Movement of Yezo Virus via Ticks on Migratory Birds, Japan, 2020-2021.
Nishino A; Tatemoto K; Ishijima K; Inoue Y; Park ES; Yamamoto T; Taira M; Kuroda Y; Virhuez-Mendoza M; Harada M; Nakamura N; Morimoto G; Yamaguchi H; Ariizumi T; Takano A; Shimoda H; Matsuno K; Maeda K
Emerging infectious diseases, 2024年12月01日
研究論文（学術雑誌）, Migratory birds carry ticks harboring various pathogens, including the zoonotic Yezo virus. In Hokkaido, Japan, we collected ticks from migratory birds during 2020-2021. Eight of 385 pools, comprising 2,534 ticks, tested positive for Yezo virus RNA, suggesting Yezo virus might be spread through the flyways of migratory birds. - Environmental and host factors underlying tick-borne virus infection in wild animals: Investigation of the emerging Yezo virus in Hokkaido, Japan.
Ito M; Minamikawa M; Kovba A; Numata H; Itoh T; Ariizumi T; Shigeno A; Katada Y; Niwa S; Taya Y; Shiraki Y; Pandey GS; Nonaka N; Nakao R; Omori R; Ohari Y; Isoda N; Shimozuru M; Tsubota T; Matsuno K; Sashika M
Ticks and tick-borne diseases, 2024年11月29日
研究論文（学術雑誌）, Yezo virus (YEZV) is an emerging tick-borne virus that causes acute febrile illness. It has been continuously reported in patients and ticks in Japan and China since its first identification in Hokkaido, Japan. While serological tests have demonstrated that YEZV infections are prevalent in wild animals, such as raccoons (Procyon lotor), the determinants of infection in wild animals remain largely unknown. We examined the prevalence of YEZV in invasive raccoons, native tanukis (raccoon dogs, Nyctereutes procyonoides albus), and ticks in six study areas in Hokkaido between 2018 and 2023 to identify ecological factors underlying YEZV infection in wild animals. YEZV RNA fragments were detected in 0.22% of the 1,857 questing ticks. Anti-YEZV antibodies were detected in 32 of the 514 (6.2%) raccoon serum samples and in 5 of the 40 (12.5%) tanuki serum samples. Notably, the seroprevalence in raccoons varied significantly in one of the study areas over the years, that is, 0.0%, 60.0%, and 28.6% in 2021, 2022, and 2023, respectively, implying the temporary emergence of YEZV microfoci. By analyzing the tick load and YEZV seropositivity in raccoons in a field-based setting, we found a positive correlation between adult Ixodes ovatus load and YEZV-antibody positivity, highlighting the importance of I. ovatus in YEZV infection in wild animals. We also explored the environmental and host factors influencing YEZV seropositivity in raccoons and tanukis and found that landscape factors, such as the size of forest area around the trap site, were crucial for YEZV seropositivity in these animals. The significant variables for YEZV seropositivity in raccoons were partially different from those affecting tick infestation intensity in raccoons. The present results extend our understanding of tick-borne virus circulation in the field, emphasizing the unique ecology of the emerging YEZV. - African lineage 1a West Nile virus isolated from crocodiles exhibits low neuroinvasiveness in mice.
Kobayashi H; Chambaro H; Tabata K; Ariizumi T; Phongphaew W; Ndashe K; Ndebe J; Fandamu P; Kobayashi S; Ito N; Sasaki M; Hang'ombe BM; Simulundu E; Orba Y; Sawa H
The Journal of general virology, 2024年11月01日
研究論文（学術雑誌）, West Nile virus (WNV) is a mosquito-borne flavivirus that causes encephalitis in humans and infects crocodiles, resulting in rashes and neurological signs. In Zambia, two distinct lineages of WNV have been detected in neighbouring areas: lineage 2 in mosquitoes and lineage 1a in farmed crocodiles. Considering the risk of direct or vector-mediated WNV transmission from crocodiles to mammals, it is necessary to elucidate the pathogenicity of WNV strains derived from crocodiles. In this study, WNV was successfully isolated from naturally infected farmed crocodiles (Croc110/2019/1/ZM, Croc110). We then investigated its proliferation and pathogenicity in mice in comparison with a WNV isolate from mosquitoes in Zambia (Zmq16) and two reference strains, including one highly pathogenic (NY99) and one low pathogenic (Eg101) strain. Although viral proliferation in Vero and mammalian neuronal cells was comparable among the strains, Croc110 exhibited low cell-to-cell transmission efficiency. In vivo, more than 70% of mice (C57BL/6) intracerebrally inoculated with Croc110 displayed neurological signs, and Croc110-infected mice exhibited similarly high mortality rates as NY99- and Zmq16-infected mice. Meanwhile, comparable virus growth was observed among the strains in the brain. However, the virulence of Croc110 was significantly lower than that of Zmq16 and NY99 following intradermal (ID) and intraperitoneal inoculation. Consistently, Croc110 displayed lower growth than Zmq16 and NY99 in the brain and peripheral tissues after ID inoculation. Our study revealed that the crocodile-derived WNV strain is less neuroinvasive in mice, and it exhibits distinct pathogenicity from the highly pathogenic mosquito-derived WNV strain circulating in Zambia. - Reverse genetic approaches allowing the characterization of the rabies virus street strain belonging to the SEA4 subclade.
Kawaguchi N; Itakura Y; Intaruck K; Ariizumi T; Harada M; Inoue S; Maeda K; Ito N; Hall WW; Sawa H; Orba Y; Sasaki M
Scientific reports, 2024年08月09日
研究論文（学術雑誌）, Rabies virus (RABV) is the causative agent of rabies, a lethal neurological disease in mammals. RABV strains can be classified into fixed strains (laboratory strains) and street strains (field/clinical strains), which have different properties including cell tropism and neuroinvasiveness. RABV Toyohashi strain is a street strain isolated in Japan from an imported case which had been bitten by rabid dog in the Philippines. In order to facilitate molecular studies of RABV, we established a reverse genetics (RG) system for the study of the Toyohashi strain. The recombinant virus was obtained from a cDNA clone of Toyohashi strain and exhibited similar growth efficiency as the original virus in cultured cell lines. Both the original and recombinant strains showed similar pathogenicity with high neuroinvasiveness in mice, and the infected mice developed a long and inconsistent incubation period, which is characteristic of street strains. We also generated a recombinant Toyohashi strain expressing viral phosphoprotein (P protein) fused with the fluorescent protein mCherry, and tracked the intracellular dynamics of the viral P protein using live-cell imaging. The presented reverse genetics system for Toyohashi strain will be a useful tool to explore the fundamental molecular mechanisms of the replication of RABV street strains. - Establishment of a lethal mouse model of emerging tick-borne orthonairovirus infections
Takuma Ariizumi; Koshiro Tabata; Yukari Itakura; Hiroko Kobayashi; William W. Hall; Michihito Sasaki; Hirofumi Sawa; Keita Matsuno; Yasuko Orba
PLOS Pathogens, 2024年03月19日
英語, 研究論文（学術雑誌）, - Combination therapy with oral antiviral and anti-inflammatory drugs improves the efficacy of delayed treatment in a COVID-19 hamster model.
Sasaki M; Sugi T; Iida S; Hirata Y; Kusakabe S; Konishi K; Itakura Y; Tabata K; Kishimoto M; Kobayashi H; Ariizumi T; Intaruck K; Nobori H; Toba S; Sato A; Matsuno K; Yamagishi J; Suzuki T; Hall WW; Orba Y; Sawa H
EBioMedicine, 2023年12月30日
研究論文（学術雑誌）,Background
Pulmonary infection with SARS-CoV-2 stimulates host immune responses and can also result in the progression of dysregulated and critical inflammation. Throughout the pandemic, the management and treatment of COVID-19 has been continuously updated with a range of antiviral drugs and immunomodulators. Monotherapy with oral antivirals has proven to be effective in the treatment of COVID-19. However, treatment should be initiated in the early stages of infection to ensure beneficial therapeutic outcomes, and there is still room for further consideration on therapeutic strategies using antivirals.Methods
We studied the therapeutic effects of monotherapy with the oral antiviral ensitrelvir or the anti-inflammatory corticosteroid methylprednisolone and combination therapy with ensitrelvir and methylprednisolone in a delayed dosing model of hamsters infected with SARS-CoV-2.Findings
Combination therapy with ensitrelvir and methylprednisolone improved respiratory conditions and reduced the development of pneumonia in hamsters even when the treatment was started after 2 days post-infection. The combination therapy led to a differential histological and transcriptomic pattern in comparison to either of the monotherapies, with reduced lung damage and down-regulation of expression of genes involved in the inflammatory response. Furthermore, we found that the combination treatment is effective in case of infection with either the highly pathogenic delta or circulating omicron variants.Interpretation
Our results demonstrate the advantage of combination therapy with antiviral and corticosteroid drugs in COVID-19 treatment from the perspective of lung pathology and host inflammatory responses.Funding
Funding bodies are described in the Acknowledgments section. - Development of flavivirus subviral particles with low cross-reactivity by mutations of a distinct antigenic domain.
Tabata K; Itakura Y; Ariizumi T; Igarashi M; Kobayashi H; Intaruck K; Kishimoto M; Kobayashi S; Hall WW; Sasaki M; Sawa H; Orba Y
Applied microbiology and biotechnology, 2023年10月13日
研究論文（学術雑誌）, The most conserved fusion loop (FL) domain present in the flavivirus envelope protein has been reported as a dominant epitope for cross-reactive antibodies to mosquito-borne flaviviruses (MBFVs). As a result, establishing accurate serodiagnosis for MBFV infections has been difficult as anti-FL antibodies are induced by both natural infection and following vaccination. In this study, we modified the most conserved FL domain to overcome this cross-reactivity. We showed that the FL domain of lineage I insect-specific flavivirus (ISFV) has differences in antigenicity from those of MBFVs and lineage II ISFV and determined the key amino acid residues (G106, L107, or F108), which contribute to the antigenic difference. These mutations were subsequently introduced into subviral particles (SVPs) of dengue virus type 2 (DENV2), Zika virus (ZIKV), Japanese encephalitis virus (JEV), and West Nile virus (WNV). In indirect enzyme-linked immunosorbent assays (ELISAs), these SVP mutants when used as antigens reduced the binding of cross-reactive IgG and total Ig induced by infection of ZIKV, JEV, and WNV in mice and enabled the sensitive detection of virus-specific antibodies. Furthermore, immunization of ZIKV or JEV SVP mutants provoked the production of antibodies with lower cross-reactivity to heterologous MBFV antigens compared to immunization with the wild-type SVPs in mice. This study highlights the effectiveness of introducing mutations in the FL domain in MBFV SVPs with lineage I ISFV-derived amino acids to produce SVP antigens with low cross-reactivity and demonstrates an improvement in the accuracy of indirect ELISA-based serodiagnosis for MBFV infections. KEY POINTS: • The FL domain of Lineage I ISFV has a different antigenicity from that of MBFVs. • Mutated SVPs reduce the binding of cross-reactive antibodies in indirect ELISAs. • Inoculation of mutated SVPs induces antibodies with low cross-reactivity. - S-217622, a SARS-CoV-2 main protease inhibitor, decreases viral load and ameliorates COVID-19 severity in hamsters
Michihito Sasaki; Koshiro Tabata; Mai Kishimoto; Yukari Itakura; Hiroko Kobayashi; Takuma Ariizumi; Kentaro Uemura; Shinsuke Toba; Shinji Kusakabe; Yuki Maruyama; Shun Iida; Noriko Nakajima; Tadaki Suzuki; Shinpei Yoshida; Haruaki Nobori; Takao Sanaki; Teruhisa Kato; Takao Shishido; William W. Hall; Yasuko Orba; Akihiko Sato; Hirofumi Sawa
Science Translational Medicine, 2023年01月18日
研究論文（学術雑誌） - Characterization of a Novel Cysteine Protease Inhibitor from Poultry Red Mites: Potential Vaccine for Chickens.
Fujisawa S; Murata S; Isezaki M; Ariizumi T; Sato T; Oishi E; Taneno A; Maekawa N; Okagawa T; Ichii O; Konnai S; Ohashi K
Vaccines, 2021年12月13日
研究論文（学術雑誌）, Poultry red mite (PRM; Dermanyssus gallinae) is a hazardous, blood-sucking ectoparasite of birds that constitutes a threat to poultry farming worldwide. Acaricides, commonly used in poultry farms to prevent PRMs, are not effective because of the rapid emergence of acaricide-resistant PRMs. However, vaccination may be a promising strategy to control PRM. We identified a novel cystatin-like molecule in PRMs: Dg-Cys. Dg-Cys mRNA expression was detected in the midgut and ovaries, in all stages of life. The PRM nymphs that were artificially fed with the plasma from chickens that were immunized with Dg-Cys in vitro had a significantly reduced reproductive capacity and survival rate. Moreover, combination of Dg-Cys with other antigen candidates, like copper transporter 1 or adipocyte plasma membrane-associated protein, enhanced vaccine efficacies. vaccination and its application as an antigen for cocktail vaccines could be an effective strategy to reduce the damage caused by PRMs in poultry farming. - In vitro evaluation of a cysteine protease from poultry red mites, Demanyssus gallinae, as a vaccine antigen for chickens.
Ariizumi T; Murata S; Fujisawa S; Isezaki M; Sato T; Oishi E; Taneno A; Ichii O; Maekawa N; Okagawa T; Konnai S; Ohashi K
Poultry science, 2021年12月01日
研究論文（学術雑誌）, Poultry red mites (PRMs, Dermanyssus gallinae) are hematophagous ectoparasites that negatively affect egg production, which causes serious economic losses to the poultry industry worldwide. Currently, the emergence of acaricide-resistant PRMs has impeded PRM control in poultry farms. Several alternatives for acaricide use have been described for managing PRM-caused problems. Vaccination is among the methods for controlling PRMs in poultry houses. Currently, several candidates for vaccine antigens have been identified. This study identified a cysteine protease, Deg-CPR-2, which differs from 2 other previously reported cysteine proteases in PRMs, from previously obtained data from RNA-sequencing (RNA-seq) analysis. We investigated the characteristics of Deg-CPR-2 and assessed its efficacy as a vaccine antigen in vitro. Phylogenetic analysis revealed that Deg-CPR-2 belonged to a different cluster from those of other cysteine proteases in PRMs. This cluster also included cathepsin L-like proteases, enzymes thought to be involved in hemoglobin digestion in ticks. Expression analysis revealed Deg-CPR-2 expression in midguts and all the life-stages; however, there were differences in the expression levels across the life-stages. The enzyme activity of recombinant Deg-CPR-2 was inhibited in the presence of a cysteine protease inhibitor, which suggests that Deg-CPR-2 functions as a cysteine protease in PRMs. Finally, there was an in vitro increase in the mortality of PRMs, mainly protonymphs that were artificially fed with plasma from chickens immunized with Deg-CPR-2. These findings suggest that Deg-CPR-2 may contribute to protein digestion in the midgut of PRMs and is crucially involved in physiological processes in PRMs. Additionally, immunization with Deg-CPR-2 may reduce the number of protonymphs, and Deg-CPR-2 should be considered as a candidate antigen for anti-PRM vaccine development. - Characterization of a copper transporter 1 from Dermanyssus gallinae as a vaccine antigen.
Fujisawa S; Murata S; Isezaki M; Ariizumi T; Sato T; Oishi E; Taneno A; Maekawa N; Okagawa T; Ichii O; Konnai S; Ohashi K
Parasitology, 2021年09月10日
研究論文（学術雑誌）, Poultry red mites (Dermanyssus gallinae, PRM) are dangerous ectoparasites that infest chickens and threaten the poultry industry worldwide. PRMs usually develop resistance to chemical acaricides, necessitating the development of more effective preventive agents, and vaccination could be an alternative strategy for controlling PRMs. The suitability of plasma membrane proteins expressed in the midguts as vaccine antigens was evaluated because these molecules are exposed to antibodies in the ingested blood and the binding of antibodies could potentially induce direct damage to midgut tissue and indirect damage via inhibition of the functions of target molecules. Therefore, in the present study, a copper transporter 1-like molecule (Dg-Ctr1) was identified and its efficacy as a vaccine antigen was assessed in vitro. Dg-Ctr1 mRNA was expressed in the midguts and ovaries and in all the life stages, and flow cytometric analysis indicated that Dg-Ctr1 was expressed on the plasma membrane. Importantly, nymphs fed on plasma derived from chickens immunized with the recombinant protein of the extracellular region of Dg-Ctr1 showed a significant reduction in the survival rate. These data indicate that the application of Dg-Ctr1 as a vaccine antigen could reduce the number of nymphs in the farms, contributing to reduction in the economic losses caused by PRMs in the poultry industry. To establish an effective vaccination strategy, the acaricidal effects of the combined use of Dg-Ctr1 with chemical acaricides or other vaccine antigens must be examined. - In vitro characterization of adipocyte plasma membrane-associated protein from poultry red mites, Dermanyssus gallinae, as a vaccine antigen for chickens.
Fujisawa S; Murata S; Takehara M; Aoyama J; Morita A; Isezaki M; Win SY; Ariizumi T; Sato T; Oishi E; Taneno A; Maekawa N; Okagawa T; Ichii O; Konnai S; Ohashi K
Vaccine, 2021年09月09日
研究論文（学術雑誌）, The poultry red mite (Dermanyssus gallinae; PRM) is a blood-sucking ectoparasite of chickens that is a threat to poultry farming worldwide and significantly reduces productivity in the egg-laying industry. Chemical acaricides that are widely used in poultry farms for the prevention of PRMs are frequently ineffective due to the emergence of acaricide-resistant PRMs. Therefore, alternative control methods are needed, and vaccination is a promising strategy for controlling PRMs. A novel adipocyte-plasma membrane-associated protein-like molecule (Dg-APMAP) is highly expressed in blood-fed PRMs according to a previous RNA sequencing analysis. Here, we attempted to identify the full sequence of Dg-APMAP, study its expression in different life stages of PRMs, and evaluate its potential as a vaccine antigen. Dg-APMAP mRNA was expressed in the midgut and ovaries, and in all life stages regardless of feeding states. Importantly, in vitro feeding of PRMs with plasma derived from chickens immunized with the recombinant protein of the extracellular region of Dg-APMAP significantly reduced their survival rate in nymphs and adults, which require blood meals. Our data suggest that the host immune responses induced by vaccination with Dg-APMAP could be an effective strategy to reduce the suffering caused by PRMs in the poultry industry. - Selection of reference genes for quantitative PCR analysis in poultry red mite (Dermanyssus gallinae).
Ariizumi T; Murata S; Fujisawa S; Isezaki M; Maekawa N; Okagawa T; Sato T; Oishi E; Taneno A; Konnai S; Ohashi K
The Journal of veterinary medical science, 2021年02月11日
研究論文（学術雑誌）, Poultry red mites (PRMs, Dermanyssus gallinae) are harmful ectoparasites that affect farmed chickens and cause serious economic losses in the poultry industry worldwide. Acaricides are used for PRM control; however, some PRMs have developed acaricide-resistant properties, which have indicated the need for different approaches for PRM control. Therefore, it is necessary to elucidate the biological status of PRMs to develop alternative PRM control strategies. Quantitative polymerase chain reaction (qPCR) allows analysis of the biological status at the transcript level. However, reference genes are preferable for accurate comparison of expression level changes given the large variation in the quality of the PRM samples collected in each farm. This study aimed to identify candidate reference genes with stable expression levels in the different blood feeding states and life stages of PRMs. First, we selected candidates based on the following criteria: sufficient expression intensity and no significant expression difference between fed and starved states. We selected and characterized seven candidate reference genes. Among them, we evaluated the gene expression stability between the starved and fed states using RefFinder; moreover, we compared their expression levels in each life-stage and identified two reference genes, Elongation factor 1-alpha (ELF1A)-like and apolipophorins-like. Finally, we evaluated the utility of the candidates as reference genes, and the use of ELF1A-like and apolipophorins-like successfully normalized ATP synthase subunit g -like gene expression. Thus, ELF1A-like and apolipophorins-like could be suitable reference genes in PRMs.
- 吸血性節足動物が媒介するアルボウイルスの皮内感染モデルの樹立
科学研究費助成事業
2023年03月08日 - 2025年03月31日
有泉 拓馬
アルボウイルスは蚊やダニなどの節足動物の吸血によって唾液と共に皮膚へ侵入する。したがって、感染初期を標的とした予防法および治療法の開発には皮内におけるウイルス、節足動物唾液および哺乳類宿主免疫系の相互作用を理解することが重要である。本研究では蚊由来組換えタンパク質を作製し、宿主免疫応答やウイルス感染に及ぼす影響を細胞株やマウスを用いて調べた。
組換えタンパク質をマウスマクロファージ様細胞（RAW264）の培養上清へ加え免疫応答に関わる遺伝子の発現を定量した結果、炎症性サイトカインの遺伝子であるIL-6およびT N F-αの発現量が対称群と比較して有意に上昇していた。次に、RAW264細胞またはマウス胎児線維芽細胞（NIH3T3）に組換えタンパク質と共にデングウイルス2型を接種し、ウイルス遺伝子量をqPCR法により定量した。その結果、組換えタンパク質を添加した群で増幅したウイルス遺伝子量は対照群と比較して差が認められなかった。次に、マウスの耳介に組換えタンパク質を皮内接種し、耳介における免疫応答に関わる遺伝子の発現量を調べた。その結果、一部の組み換えタンパクを接種した耳介では炎症性サイトカインの遺伝子であるIFN-βやケモカインの遺伝子であるCXCL-1、CXCL-2の遺伝子発現量の上昇傾向が認められたが顕著な変化ではなかった。
本研究では単独の蚊唾液タンパク質が宿主の免疫応答やウイルス感染に与える影響を評価したが、本来蚊の唾液中には多様なタンパク質が含まれている。また、タンパク質だけでなく核酸や常在微生物も宿主の免疫応答に影響を及ぼすことが報告されている。今後蚊の唾液に含まれる複数の成分が混在した条件でウイルス感染や免疫応答に及ぼす影響を調べることでアルボウイルス感染初期の予防・治療標的の発見につながることが期待される。
日本学術振興会, 特別研究員奨励費, 北海道大学, 22KJ0127
