[Serial amino acid sequence change in the hypervariable region of hepatitis C virus].

The hypervariable region 1 of the hepatitis C virus genome has attracted much scientific interest as higher degrees of variability of the region have been reported to be a predictive factor of poor response to interferon treatment. We analyzed sequential changes in the amino acid sequence of this region before, during and after two courses of interferon treatment. A major strain seen before treatment was overtaken by another strain which had been a relatively minor population before therapy. Later a transient emergence of two minor populations was observed during interferon treatment. We also found that the disappearance of some strains could be explained by cloning artifact due to polymerase chain reaction (PCR). Such artifact should be taken into account when analyzing this region by means of PCR.