Mutagenic effect of ribavirin on hepatitis C nonstructural 5B quasispecies in vitro and during antiviral therapy.

BACKGROUND AND AIMS: Addition of ribavirin to interferon alfa treatment has substantially increased sustained virologic response rates in patients with chronic hepatitis C (CHC). Ribavirin acts as an RNA virus mutagen in vitro, thereby leading to error catastrophe. However, data in CHC are controversial. METHODS: The nonstructural (NS) 5B quasi-species heterogeneity was analyzed in Huh7 cells harboring a subgenomic hepatitis C virus (HCV) replicon system treated with ribavirin or levovirin. Accordingly, NS5B quasi-species were studied in 14 patients with CHC who received ribavirin alone or combined with pegylated interferon alfa both at baseline and during the first weeks of therapy. Analysis of NS3 quasi-species served as control. RESULTS: Cultivation of HCV replicon cells with ribavirin led to higher NS5B mutational frequencies compared with levovirin-treated or untreated cells (P < .05). Patients receiving ribavirin monotherapy showed higher overall mutational frequencies within NS3 and NS5B during therapy as compared with baseline (P < .01). Proportions of ribavirin-specific G-to-A and C-to-T transitions increased (P < .01). Paired analysis confirmed significant mean increases of mutational frequencies of approximately 5%. Ribavirin serum concentrations were positively correlated with mutational frequency changes (P < .05). In patients receiving combination therapy, a decrease of NS5B mutational frequencies ( approximately 10%) and lower proportions of G-to-A and T-to-C mutations (P < .01) were detectable. CONCLUSIONS: Ribavirin, but not its L-enantiomer levovirin, is a mutagen in HCV replicon cells. In patients with CHC, ribavirin monotherapy exhibits a moderate mutagenic effect early during therapy that is not detectable in combination with pegylated interferon alfa.

Mutations within the CD81-binding sites and hypervariable region 2 of the envelope 2 protein: correlation with treatment response in hepatitis C virus-infected patients.

The hepatitis C virus (HCV) envelope 2 (E2) protein interacts with the cellular receptor CD81 in vitro. Within E2, 2 CD81-binding sites were described. E2-CD81 interaction has been shown to modulate B and T cell function. The clinical importance of mutations within the CD81-binding sites and overlapping hypervariable region 2 (HVR2) in correlation with response to antiviral treatment is unknown. Fifty-five patients infected with HCV-1b or HCV-3a underwent interferon-alpha-based treatment. The E2 gene, comprising the CD81-binding sites and HVR2, was sequenced from pretreatment serum samples. The number of mutations within CD81-binding sites was not correlated with virologic treatment response in HCV-1b- and HCV-3a-infected patients. Within HVR2, the total number of mutations was significantly higher in HCV-1b-infected patients with a sustained response to interferon-alpha-based treatment (3.9; range, 1-6) than in those with relapse (2.9; range, 1-5) or those who did not respond (2.8; range, 1-5) (P = .041). However, when the same analyses were based only on functionally nonconserved mutations, no significant differences were observed.