[The genetic diversity of hepatitis C virus and its implications for pathogenesis and resistance to treatment]

Hepatitis C virus (HCV) is characterized by a high genetic variability mainly due to the lack of proofreading activity of its RNA polymerase. Noncoding regions located on 5' and 3' ends of the HCV genome are conserved, whereas the hypervariable regions of the E2 envelope gene are highly mutated. This genetic heterogeneity is observed both between patients and between strains isolated at different time from a given patient. Identification of six major genotypes and of a large number of subtypes has resulted from the phylogenetic analysis of HCV strains isolated from different continents. In infected individuals, HCV exists as pools of related genetic variants, referred to as quasispecies. The role of the genetic variability of HCV in primary resistance to treatment or in the emergence of escape mutants has been described but remains controversial.