| Budget Amount *help |
¥3,400,000 (Direct Cost: ¥3,400,000)
Fiscal Year 2006: ¥1,500,000 (Direct Cost: ¥1,500,000)
Fiscal Year 2005: ¥1,900,000 (Direct Cost: ¥1,900,000)
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| Research Abstract |
We established the cell-based hepatitis C virus (HCV) replication system with recombinant adenovirus vectors and with T7 stable cell lines. With pH77 and Ad-T7pol, HCV positive and negative strand RNA expression was strongest in the first 2 to 3 days post-infection and diminished thereafter, but were expressed throughout the 9 days. This sustained expression of HCV-RNA was also seen in the system with T7 stable cell lines. In these systems, interferon (IFN) inhibits HCV replication, and upregulates the protein kinase R (PKR) pathway.
IFN and ribavirin (RBV) combination therapy is the current standard of antiviral therapy for chronic HCV. Among IFN-induced proteins, PKR is considered as a key molecule to eliminate HCV. On the other hand, interleukin-8 (IL-8) has been reported to inhibit IFN-induced antiviral responses. In our replication model, both HCV expression and IFN, induced PKR and its regulated proteins effectively. HCV protein expression in turn was directly regulated by PKR. From our experiments, PKR is directly antiviral for HCV, and is a central mediator of IFN' s effects against HCV. About IL-8, it was induced by both IFN and RBV in our systems. We speculate that IL-8 induction by both agents might not produce sufficiently antiviral effects. Rather, increased IL-8 might have an indirect role as an immunomodulator or as a chemokine in recruitment of cells that eliminate HCV.
Additionally, we did in vivo assay by collecting peripheral blood T cells from the chronic hepatitis C patients who were treated by IFN and RBV combination therapy. In the patients with early viral response (EVR), HCV-RNA become undetectable within 12 weeks, PKR mRNA in T cells are significantly higher than that in the patients with non-EVR.
From these results, we concluded that PKR and IL-8 will be key molecules for HCV replication as well as HCV persistence. Moreover, we have to consider to establish the protocol which can upregulate PKR effectively for the stronger anti-HCV therapy.
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