| Budget Amount *help |
¥3,860,000 (Direct Cost: ¥3,500,000、Indirect Cost: ¥360,000)
Fiscal Year 2007: ¥1,560,000 (Direct Cost: ¥1,200,000、Indirect Cost: ¥360,000)
Fiscal Year 2006: ¥2,300,000 (Direct Cost: ¥2,300,000)
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| Research Abstract |
Interleukin-27 (IL-27) is a heterodimeric cytokine composed of two polypeptide subunits, IL-27 p28 and EBV-induced protein 3 (Ebi3). The IL-27 signal is mediated through the heterodimeric receptor complex that consists of IL-27R_(WSX-1, TCCR)and gp130 and is expressed on various cells including naive CD4 positive T cells. Activation of JAK1/STAT1 pathway is crucially involved in the signal transduction downstream of the IL-27R complex. IL-27 provokes naive CD4 positive T cells to express T-bet and, subsequently, IL-12R62. IL-27 sequentially cooperates with IL-12 to induce initiation and maintenance of Th1 immune responses. IL-27 also synergize with IL-12 to induce interferon (IFN)-y production. Recently it was shown that generation of Th17 cells is suppressed by IL-27 in a STAT1 dependent manner. Taken together, IL-27 is involved in the key step for Th1 commitment where naive Th precursor cells commence differentiation into Th1 cells, and it is now considered that IL-27 is associated w
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ith many human diseases including malignant, allergic and inflammatory disorders. In this project, we found that IL-27 is also involved in a novel defense mechanism against virus infection. C57BI/6 mice that had been infected with Encephalomyocarditis virus (EMCV) were transfected in vivo with IL-27 gene, and their longevity was analyzed. All the control mice that received the virus but not IL-27 gene died within 10 days after the infection, whereas survival rate of the IL-27 gene-transfected mice remained 100% during this period. To clarify the mechanism of the anti-virus activity of IL-27, we also performed in vitro experiments, which strongly suggested that IL-27 directly acted on virus-infected cardiomyocytes to suppress virus replication, whereas induction of acquired immune responses did not contribute to the virus clearance. As an intracellular innate machinery against virus infection, MDA5-mediated pathway is widely known, but little is known on molecular mechanisms to regulate MDA5 expression. Then we assessed whether MDA5 participates in the IL-27-mediated virus suppression. Primary cardiac muscle cells were established form the day 16 mouse embryos and stimulated with IL-27, which led to drastic induction of mRNA for MDA5. Infected with EMCV, the IL-27-treated cells showed massive production of IFN-6 immediately after the infection, which was in sharp contrast to the lower level of IFN production by the cells that were not treated with IL-27. Specific silencing of MDA5 by means of the short interfering RNA completely cancelled the and-virus effect that was otherwise produced in cardiomyocytes after the IL-27 provocation. These findings indicate that IL-27 signaling augments expression of MDA5 in cardiac muscle cells, resulting in a strengthening of MDA5 pathway triggered by virus infection, which in turn generates robust induction of type I IFN at an early phase of infection to effectively suppress virus replication. Less
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