Variation of hepatitis C virus hypervariable region 1 in immunocompromised patients

The viral variability of 5 hepatitis C virus (HCV)-infected immunocompromised patients was analyzed and compared with that in isolates from immunocompetent subjects. The patients were followed longitudinally with regard to changes in hypervariable region 1 (HVR1) of HCV using a direct DNA sequencing approach. For the immunocompromised patients, viral nucleotide sequence variability was markedly lower than in immunocompetent HCV-positive patients. For 1 agammaglobulinemic patient and 1 AIDS patient, no variation in the major amino acid sequence of HCV HVR1 could be observed, while another agammaglobulinemic patient exhibited transient variations and amino acid substitutions despite the lack of functioning humoral immune response. The study supports the general hypothesis of humoral immune selection as the main force of sequence variation in the HVR1 region but suggests that other selection mechanisms may contribute to modulation of the composition of the viral population.