Hepatitis B virus genotypes: Epidemiology and therapeutic implications

Hepatitis B virus (HBV) is a global health problem. Effective and individualized treatment of chronic hepatitis B to prevent progression to end-stage liver diseases and hepatocellular carcinoma is thus needed. HBV has been designated eight genotypes (A-H) based on genome sequence divergence. Each genotype has its distinct geographic and ethnic distribution. The epidemiology of HBV genotypes and their implications on the responses to antiviral therapy have become increasingly recognized. Recent studies suggested that sustained responses to standard interferon in patients with genotype A or B are better than those with genotype C or D. However, conflicting results exist regarding the response to peginterferon. Furthermore, therapeutic responses to nucleoside/nucleotide analogous are comparable among different HBV genotypes. In summary, clinical and pathogenic differences exist among HBV genotypes and future research should focus on molecular and virologic mechanisms underlying the clinical phenotypes of different HBV genotypes.