Recent results of clinical trials suggest that combination of
interferon and
ribavirin exhibits an enhanced
antiviral effect in the treatment of
chronic hepatitis C. To investigate the effect of
ribavirin on hepatitis C virus (HCV)
infection, we analysed the evolution of the genetic heterogeneity of HCV in relation to the anti-HCV humoral response in patients treated by
ribavirin alone. The study population included 35 patients with liver biopsy proven
chronic hepatitis C infected with HCV genotype 1. Among them, 26 were treated with
ribavirin for at least 12 months and nine untreated patients served as a control group. Serum samples were analysed before and at 6 and 12 months of
therapy. Three regions of the HCV genome, i.e. HVR1, a domain of NS5A including part of the
interferon sensitivity determining region (ISDR), and a segment of NS5B, were amplified by RT-PCR using specific primers. The PCR products were then studied using single-strand conformation polymorphism (SSCP) analysis followed by either direct sequencing, or cloning and sequencing. In parallel, the humoral anti-E1 response was studied using an ELISA (Innotest HCV E1Ab, Innogenetics). The results of HCV genome analysis showed no significant effect on the amino acid sequence evolution of the HVR1, NS5A and NS5B regions of HCV. Analysis of a phylogenetic tree from the major quasispecies variants showed the absence of correlation with
ribavirin response, and the absence of selection of viral strains during
ribavirin treatment. A trend towards a decrease in the anti-E1 Ab response was also observed. Altogether these results suggest that
ribavirin may not exhibit a direct
antiviral effect, but may trigger a favourable response to
interferon by modulating the immune response against HCV.