Analysis of CD8+ T cell-mediated inhibition of hepatitis C virus replication using a novel immunological model

While virus-specific CD8+ T cells are required for the control of hepatitis C virus (HCV) infection, the extent to which different effector functions contribute to the inhibition of viral replication has not been well defined. To address this important issue, we developed a novel immunological model by stably transducing the HLA-A2 gene into the replicon system, matching the epitope sequence of the replicon to the sequence targeted by an HCV-specific CD8+ T cell clone, and using luciferase activity to quantitate HCV RNA replication. Our findings demonstrate that HCV-specific CD8+ T cells strongly inhibit viral replication through cytolytic and noncytolytic mechanisms in a dose-dependent manner. While HCV replication was almost completely inhibited at an E: T ratio of 1: 1 with significant cell killing, inhibition of HCV replication by >95% occurs even at ratios as low as 1: 100. Importantly, at these low E: T ratios, cell killing was not observed, indicating a dominant effect of noncytolytic effector functions that was confirmed by transwell experiments. Neutralization experiments revealed that IFN-gamma mediates the noncytolytic inhibition. Taken together, our analyses demonstrate that only a very few HCV-specific CD8+ T cells are needed to inhibit HCV replication by primarily noncytolytic effector functions.

HCV infection - HCV-specific CD8+ T cells - IFN-gamma