HCV structural proteins interfere with interferon-alpha Jak/STAT signalling pathway.

Hepatitis C virus (HCV) is remarkably efficient at establishing persistent infection. The current treatment with IFN-alpha given alone or in combination with ribavirin is ineffective in eliminating the virus in a large proportion of individuals with chronic hepatitis C. Recent data suggest that HCV blocks IFN-alpha signalling, an effect that facilitates viral persistence. We have used the HCV genomic and subgenomic replicon system to analyze the effect of structural and non-structural viral proteins on the activation of the Jak/STAT pathway and induction of antiviral activity by IFN-alpha. Our results show that IFN-alpha-mediated STAT activation (but not IFN-gamma-stimulated STAT phosphorylation) is blocked in Huh7 cell line containing the genomic replicon, while this is not observed in cells with the subgenomic replicon. In agreement with these findings, the transcriptional activity and the antiviral effect of IFN-alpha were significantly lower in cells harboring the genomic replicon than in cells with the subgenomic replicon. These results indicate that HCV structural proteins play an important role in the escape of HCV from the interferon system.