Changes of HCV quasispecies during combination therapy with interferon and ribavirin.

Treatment of chronic hepatitis C virus (HCV) infection with interferon (IFN) and ribavirin improves the rate of eradication of HCV, but only about 13-14% of non-responders (NR) with HCV of genotype 1b previously treated with IFN achieve a sustained virological response (SVR). To determine whether HCV quasispecies diversity correlates with the outcome of therapy with IFN and ribavirin, we studied 13 patients undergoing combination therapy with IFN-alpha2b and ribavirin after failure of IFN monotherapy. HCV quasispecies diversity was assessed by cloning and sequencing before and during combination therapy. During therapy, quasispecies diversity diminished in NR patients, both in the hypervariable region (HVR) 1 of the envelope 2 (E2) domain and in the interferon sensitivity-determining region (ISDR) in the NS5A. Pre-treatment nucleotide quasispecies diversity was lower in SVR and end-of-therapy viral response (ETR) patients than in NR patients. Resistance to ribavirin was associated with high pre-treatment heterogeneity and the selection of quasispecies of the HCV genome. HVR quasispecies may be a predictor of efficacy of combination therapy with IFN and ribavirin.