title: Therapeutic implications of hepatitis B virus genotypes.
abstract: OBJECTIVE
  Hepatitis B virus (HBV) is a global health problem. In addition to the implementation of universal hepatitis B vaccination, effective and individualized treatment of chronic hepatitis B to prevent progression into end-stage liver diseases and hepatocellular carcinoma is still needed. HBV has been designated eight genotypes (A-H) based on genome sequence divergence. The epidemiology of HBV genotypes and their implications on the responses to antiviral therapy have become increasingly recognized in both Asian and Western countries.
  
  
  METHODS
  Published data are thus reviewed.
  
  
  RESULTS
  Each genotype has its distinct geographical and ethnic distribution. Genotypes A and D occur frequently in Africa, Europe, and India, while genotypes B and C are prevalent in Asia. Genotype E is restricted to West Africa, and genotype F is found in Central and South America. The distribution of genotypes G and H is less clear. Accumulating evidence indicates a better sustained response to conventional interferon in patients with genotype B than those with C, and in patients with genotype A than those with D. In contrast, conflicting results exist regarding the response to pegylated interferon. On the other hand, the therapeutic responses to nucleoside/nucleotide analogues are comparable among patients with different HBV genotypes. The impact of HBV subgenotypes, mixed genotype infections, and recombinants of different genotypes on the response to antiviral treatments awaits further examinations.
  
  
  CONCLUSIONS
  Remarkable clinical and pathogenic differences do exist among HBV genotypes; however, researches on molecular and virologic mechanisms underlying the clinical phenotypes of different HBV genotypes are urgently needed.
authors.affiliation: Department of Internal Medicine, Division of Gastroenterology, National Taiwan University Hospital, National Taiwan University College of Medicine, Taipei, Taiwan.
authors.forename: Chun-Jen
authors.initials: CJ
authors.lastname: Liu
authors.forename: Jia-Horng
authors.initials: JH
authors.lastname: Kao
authors.forename: Ding-Shinn
authors.initials: DS
authors.lastname: Chen
mesh_terms: D000998:Antiviral Agents / Q000627:therapeutic use*; D006528:Carcinoma, Hepatocellular / Q000821:virology; D005814:Genes, Viral; D005838:Genotype; D006509:Hepatitis B / Q000188:drug therapy* / Q000821:virology; D006515:Hepatitis B virus / Q000145:classification / Q000235:genetics*; D006801:Humans; D016898:Interferon-alpha / Q000627:therapeutic use; D019259:Lamivudine / Q000627:therapeutic use; D008113:Liver Neoplasms / Q000821:virology
chemical_list: D000998:Antiviral Agents; D016898:Interferon-alpha; D019259:Lamivudine