Evolution of hepatitis C virus genome in chronically infected patients receiving ribavirin monotherapy

Recent results of clinical trials suggest that combination of interferon an d ribavirin exhibits an enhanced antiviral effect in the treatment of chron ic 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 ri bavirin alone. The study population included 35 patients with liver biopsy proven chronic hepatitis C infected with HCV genotype 1. Among them, 26 wer e 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 (I SDR), and a segment of NS5B, were amplified by RT-PCR using specific primer s. The PCR products were then studied using single-strand conformation poly morphism (SSCP) analysis followed by either direct sequencing, or cloning a nd sequencing. In parallel, the humoral anti-E1 response was studied using an ELISA (Innotest HCV E1Ab, Innogenetics). The results of HCV genome analy sis showed no significant effect on the amino acid sequence evolution of th e HVR1, NS5A and NS5B regions of HCV. Analysis of a phylogenetic tree from the major quasispecies variants showed the absence of correlation with riba virin response, and the absence of selection of viral strains during ribavi rin treatment. A trend towards a decrease in the anti-E1 Ab response was al so observed. Altogether these results suggest that ribavirin may not exhibi t a direct antiviral effect, but may trigger a favourable response to inter feron by modulating the immune response against HCV.