RESUMO
Recent results of clinical trials suggest that combination of interferon and ribavirin exhibits an enhanced antiviral effect in the treatment of chronic 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 ribavirin alone. The study population included 35 patients with liver biopsy proven chronic hepatitis C infected with HCV genotype 1. Among them, 26 were 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 (ISDR), and a segment of NS5B, were amplified by RT-PCR using specific primers. The PCR products were then studied using single-strand conformation polymorphism (SSCP) analysis followed by either direct sequencing, or cloning and sequencing. In parallel, the humoral anti-E1 response was studied using an ELISA (Innotest HCV E1Ab, Innogenetics). The results of HCV genome analysis showed no significant effect on the amino acid sequence evolution of the HVR1, NS5A and NS5B regions of HCV. Analysis of a phylogenetic tree from the major quasispecies variants showed the absence of correlation with ribavirin response, and the absence of selection of viral strains during ribavirin treatment. A trend towards a decrease in the anti-E1 Ab response was also observed. Altogether these results suggest that ribavirin may not exhibit a direct antiviral effect, but may trigger a favourable response to interferon by modulating the immune response against HCV.
Assuntos
Antivirais/uso terapêutico , Genoma Viral , Hepacivirus/efeitos dos fármacos , Hepatite C Crônica/virologia , Ribavirina/uso terapêutico , Sequência de Aminoácidos , Evolução Molecular , Feminino , Genótipo , Hepacivirus/genética , Hepatite C , Anticorpos Anti-Hepatite C/sangue , Hepatite C Crônica/sangue , Hepatite C Crônica/tratamento farmacológico , Humanos , Interferons/farmacologia , Masculino , Pessoa de Meia-Idade , Dados de Sequência Molecular , Alinhamento de Sequência , Proteínas não Estruturais Virais/genética , Proteínas Virais/genética , Proteínas Estruturais Virais/imunologiaRESUMO
Hepatitis C virus (HCV) is a small enveloped virus whose genome is a RNA molecule encoding a polyprotein that is processed by cellular and viral proteases to produce the 3 structural proteins (the core protein C and the 2 envelope proteins E1 and E2) and the 6 nonstructural proteins (NS2, NS3, NS4A, NS4B, NS5A and NS5B). The HCV genome exhibits a significant genetic heterogeneity. HCV isolates can be divided into genetically distinct groups referred to as genotypes, whereas the population of HCV genomes, within an infected individual, is present as a group of heterogeneous but closely related sequences referred to as quasi-species. Studies of the molecular biology of HCV and of new vaccinal or therapeutic strategies are hampered by the lack of easy to use cellular culture systems and of animal models.