Impact of NS5A Sequences of Hepatitis C Virus Genotype 1a on Early Viral Kinetics during Treatment with Peginterferon-α2a plus Ribavirin

Background. Hepatitis C virus (HCV) genotype 1 is the most prevalent genotype in Western countries, and treatment with pegylated interferon (pegIFN) plus ribavirin fails in 50%–60% of patients. Genetic variability within the NS5A dsRNA-dependent protein kinase binding domain (PKRbd) of HCV-1b has been associated with responsiveness to IFN-α. Little is known about NS5A sequences of HCV-1a.We investigated whether genetic variability of HCV-1a NS5A correlates with the early HCV kinetics during treatment. Methods. Twenty-four treatment-naive, HCV-1a-infected patients were treated with standard doses of pegIFNα2a plus ribavirin. HCV viremia was quantitated at days 0, 1, 2, and 3 and weeks 1, 2, 4, 8, and 12 of treatment. According to HCV kinetics, patients were classified as early rapid responders, early moderate responders, or early slow responders. The full-length HCV NS5A was sequenced at baseline and at week 1. Results. At baseline, variability of the NS5A C terminus (concentrated in the PKRbd) is associated with interferon efficacy but not with the second phase of the early viral decline that has been associated with a sustained virologic response. Comparisons between baseline and week-1 full-length sequences did not show significant increases in mutations. Conclusions. Genetic variability of HCV-1a NS5A does not predict responsiveness to IFN-α. Differences in early kinetics during combination therapy are not due to selection of IFN-resistant HCV strains.