Hepatitis C viral quasispecies

Analysing significant numbers of cDNA clones of the hepatitis C virus (HCV) from single isolates provides unquestionable proof that the viral genome c annot be defined by a single sequence, but rather by a population of varian t sequences closely related to one another. This way of organizing the gene tic information is referred to as quasispecies. Throughout HCV infection, t he number and composition of the variants in the viral population keeps cha nging owing to environmental influences, resulting in a virus that is const antly redefining itself both genetically and phenotypically, Therefore, the virus has often been investigated in population terms. Many clinical studi es have tried to unravel, through the parameters that characterize the HCV quasispecies, prognostic markers of the disease and its response to treatme nt. Other investigations have focused on discovering how the virus and host interact during chronic infection. The consensus sequence, the rate of fix ation of mutations and the complexity of the viral population are useful pa rameters for describing the viral population behaviour and its interaction with the host. In addition to sequencing, several other methods, based on e lectrophoretic mobility, have been used to study these parameters. such as temperature gradient-gel electrophoresis, single-strand conformation polymo rphism and gel-shift analysis. The viral region examined, the source of cli nical specimen, as well as the methodology employed, will be decisive in in terpreting the information obtained.