Hepatitis B virus genotypes and response to antiviral therapy.

Hepatitis B virus (HBV) infection is an important health problem worldwide. The virus has been classified according to 8 genotypes (A-H) based on sequence divergence. Most genotypes have specific geographic distributions; genotypes A and D are prevalent in Western Europe and North America, and genotypes B and C are prevalent in East Asia and Oceania. Currently accepted treatment for chronic hepatitis B includes interferon alpha, or the nucleoside/nucleotide analogues lamivudine and adefovir. The impact of HBV genotypes on response to antiviral therapy has been studied. HBV genotypes D and C are associated with a lower rate of favorable response to interferon alpha therapy than genotypes A and B, respectively. A study in Germany suggested that the rate of resistance to lamivudine was higher in patients with HBV genotype A infection than in patients with genotype D infection. No difference in the risk of lamivudine resistance is found between patients with genotype B and patients with genotype C. In patients with genotype C infection, however, virological response is worse during lamivudine therapy, and is also less durable after the discontinuation of therapy than in patients with genotype B infection. Determining the genotype could be helpful for predicting the outcome of antiviral therapy in patients with chronic hepatitis B.