Differences in viral kinetics between genotypes 1 and 2 of hepatitis C virus after single administration of standard interferon‐alpha

Hepatitis C virus (HCV) kinetics were determined after a single administration of standard interferon (IFN) according to the HCV genotype that affects the response to antiviral therapy with IFN/peginterferon. A total of 208 patients were investigated. All patients received a single administration of 6 megaunits of standard IFN-alpha. HCV RNA concentration was measured before, and at 24, 48, 72, and 120 hr after administration. Changes in HCV RNA concentration were compared between genotypes. The patient group consisted of 132 patients with genotype 1B, 58 with genotype 2A, and 18 with genotype 2B. In the comparison between genotypes 1 and 2, the reduction in HCV RNA concentration after a single IFN administration was less marked in patients with genotype 1B at both 24 and 48 hr after administration (P < 0.0001). In contrast, an increase in HCV RNA concentration during 24–48 or 24–72 hr after a single administration was comparable between genotypes 1 and 2. In the comparison between genotypes 2A and 2B, the reduction in HCV RNA concentration after a single administration was more marked in patients with genotype 2A, despite the similar rate of sustained virologic response to peginterferon and ribavirin combination therapy. The results of the study indicate that the rapid decrease in HCV RNA concentration observed during IFN or peginterferon therapy in patients with genotype 2 appeared to be due to the difference in sensitivity to IFN. Within genotype 2, HCV genotype 2A was more sensitive to IFN than genotype 2B. J. Med. Virol. 81:1354–1362, 2009. © 2009 Wiley-Liss, Inc.