Objective: The RNA genome of hepatitis C virus varies considerably, especially within the hypervariable region 1 (HVR1), a domain located on the 5' end of the E2/NS1 envelope region. Our previous study has suggested there were greater numbers of quasispecies in the liver than in matched serum, independent of the viral load. However, the significance of this finding has not been examined extensively at genetic and serological levels.
Methods: By large scale cloning and sequencing, we studied the genetic complexity of HVR1 quasispecies in two selected patients with cirrhosis. The serum reactivity of peptides representing different HVR1 quasispecies isolated from these cases was also estimated by standard ELISA format.
Results: We found the same major (dominant and/or subdominant) viral quasispecies variants in serum and in the cirrhotic liver. Genetic analysis suggested that the evolutionary pressure on HVR1 was higher than on its flanking region in quasispecies derived from the liver, whereas this trend is attenuated in quasispecies from serum. The immunoreactivity to peptides representing different HVR1 quasispecies variants showed considerable cross-reactivity with heterologous sera, whereas the reactivity was strongest against the dominant HVR1 peptide over time in homologous sera.
Conclusions: These findings indicate that the formation and selection of HVR1 quasispecies may not be driven solely by humoral immune pressure, at least in these two cases.