RESUMO
There are limited data on diversity within the hepatitis C virus polymerase (NS5B). In concordance with its key functional role during the life cycle, NS5B intrapatient variability was low. Moreover, differences between NS5B nonsynonymous (dN) and synonymous (dS) mutation rates (dN - dS) were positively correlated with CD4 cell count, while nonsynonymous mutations were strongly correlated with reduced replication in vivo.
Assuntos
Variação Genética , Hepacivirus/classificação , Hepacivirus/genética , Hepatite C/virologia , Proteínas não Estruturais Virais/genética , Sequência de Aminoácidos , Contagem de Linfócito CD4 , Feminino , Hepacivirus/imunologia , Hepacivirus/isolamento & purificação , Hepatite C/imunologia , Humanos , Dados de Sequência Molecular , Análise de Sequência de DNARESUMO
OBJECTIVES: Hepatitis C virus (HCV) non-nucleoside inhibitors (NNIs) target the viral RNA-dependent RNA polymerase encoded by the NS5B gene. Several NNIs share a similar allosteric binding site, and their antiviral efficacy is attenuated by a cysteine-to-tyrosine mutation at amino acid 316 (C316Y). In the current study, we assessed NS5B resistance mutations in treatment-naive individuals from a prospective natural history study of viral infections in women. METHODS: Partial NS5B sequences from HCV-positive women were amplified by RT-PCR. Additionally, subcloning was performed to evaluate intrapatient variability in selected samples. RESULTS: HCV NS5B genotypes were 45 genotype 1a (57.0%), 11 genotype 1b (13.9%), 5 genotype 2a (6.3%), 3 genotype 2b (3.8%), 9 genotype 3a (11.4%) and 6 genotype 4a (7.6%). One HCV genotype 1a-infected patient was found to have the C316Y mutation (1.3%). Clonal analysis further revealed that all NS5B sequences from this individual--representing three serum samples collected 4 years apart--contained the C316Y mutation. In contrast, the S282T resistance mutation was not found in any samples. CONCLUSIONS: The C316Y polymerase resistance mutation was found in 1.3% of samples from HCV-infected women. The presence of this mutation over time suggests significant replicative fitness of this variant and has implications for development of new specifically targeted antiviral therapies against HCV (STAT-C) targeting this region.