Effect of alpha interferon on the hepatitis C virus replicon

Chronic hepatitis C virus (HCV) infections can be cured only in a fraction of patients treated with alpha interferon (IFN-alpha) and ribavirin combina tion therapy. The mechanism of the IFN-alpha response against HCV is not un derstood, but evidence for a role for viral nonstructural protein 5A (NS5A) in IFN resistance has been provided. To elucidate the mechanism by which N S5A and possibly other viral proteins inhibit the cellular antiviral progra m, we have constructed a subgenomic replicon from a known infectious HCV cl one and demonstrated that it has an approximately 1,000-fold-higher transdu ction efficiency than previously used subgenomes. We found that IFN-alpha r educed replication of HCV subgenomic replicons approximately 10-fold. The e stimated half-life of viral RNA in the presence of the cytokine was about 1 2 h. HCV replication was sensitive to IFN-alpha independently of whether th e replicon expressed an NS5A protein associated with sensitivity or resista nce to the cytokine. Furthermore, our results indicated that HCV replicons can persist in Huh7 cells in the presence of high concentrations of IFN-alp ha. Finally, under our conditions, selection for IFN-alpha -resistant varia nts did not occur.