57: Pivotal role of the IKK-related kinase IKK epsilon to modulate IL29 or type I IFN induction during hepatitis C virus infection

Abstract

Acute HCV infection can induce IL-29, a type III IFN, in hepatocytes but the mechanism of this induction is not known. Here, kinetics of IL-29 induction was analysed in the Huh7.25/CD81 cells infected with cell-culture HCV JFH1. IL-29 was produced and secreted early in infection (day 4) and able to activate the JAK/STAT-mediated induction of ISGs while IFN β was either absent or produced at low levels and at later times (6–7 days). Involvement of the RIG-I/MAVS or TLR3 pathways in IL-29 induction was ruled out since the HCV NS3/4A sensitive-MAVS was fully cleaved at day 2 post infection and since IFN was not induced in polyIC-treated cells. However, IRF3 and IRF7 were activated at day 4 of infection, as shown by IRF3-Gal4 and IRF7-Gal4 assays. We also found that JFH1 infection triggered induction of IRF7, the IKK-related kinase IKK e and IL8 between day 2 and day 4. Importantly, infection of human primary hepatocytes with JFH1 or with HCV of genotype 1b or 3 confirmed the data observed in the Huh7.25/CD81. We then infected the cells in presence of MRT67307, a specific inhibitor of IKK e /TBK1, previously used to demonstrate the ability of these non-canonical IKKs to impair NF-KB activation by the canonical IKKs. MRT67307 triggered increase in the induction of IL8, an NF-KB-dependent cytokine, as expected, but strinkingly it inhibits strongly induction of IL29 while that of IFN β was increased. IFN β , however, represented only a minor fraction of the IFN produced by these cells, suggesting the presence of other type I IFN isotypes. Taken together, these results suggest that the balance between type I and type III IFN induction during HCV infection can be modulated as a function of inflammation related to NF-KB activation and pinpoint a role for the IKK-related kinases, such as IKK e , in this process.