TLR3 Reduces Hepatitis C Viral Replication in Human Hepatocytes

Background: During an acute viral infection the intracellular innate immune defense is activated through the production of type I IFN and not well understood. We have developed an experimental model showing that HCV can induce IFN in LH86 cells, which have wild type TLR3 and RIG-I expression. The aim of this study is to examine how HCV induces IFN and the role of TLR in acute infection. Methods: LH86 and Huh7.5 cells and their transfected counter parts (LH86 siRIG-I, siTLR3 and siTLR7and Huh7.5 RIG-I, TLR3 and TLR7) were tested in an infectious JFH-1 HCV cell culture system. The IFN induction and antiviral efficacy of RIG-I in HCV infection was determined using real-time PCR. We also measured apoptosis by light microscopy and by flow cytometric analysis of Annexin-V expression. Results: Our data show that TLR3 is important for the induction of IFNβ in LH86 cells since silencing it prevents its production as well as the cytopathic effects normally observed in this cell line. Forced stable expression of wild type TLR3 and TLR7 in Huh7.5 cells partially restored the induction of IFN and significantly reduced the replication of the virus in an 80 day culture, with TLR3 having the greatest impact. The induction of IFN is strongly correlated with this antiviral effect. At the same time the virus decreases the expression of TLRs. Conclusion: Our study indicates that TLR3 and RIG-I in liver cells play a key role in anti-HCV defense.