Copyright ©2009 The WJG Press and Baishideng. All rights reserved.
World J Gastroenterol. Dec 14, 2009; 15(46): 5761-5769
Published online Dec 14, 2009. doi: 10.3748/wjg.15.5761
Clinical relevance and public health significance of hepatitis B virus genomic variations
Guang-Wen Cao
Guang-Wen Cao, Department of Epidemiology, Second Military Medical University, Shanghai 200433, China
Author contributions: Cao GW solely contributed to this paper.
Supported by Ministry of Health of China, No. 2008ZX10002-15; National Natural Science Foundation of China, No. 30921006; Shanghai Science & Technology Committee, No. 08XD14001; Shanghai Board of Health, No. 08GWD02; 08GWZX0201
Correspondence to: Guang-Wen Cao, MD, PhD, Professor of Medicine, Chairman, Department of Epidemiology, Second Military Medical University, 800 Xiangyin Road, Shanghai 200433, China. gcao@smmu.edu.cn
Telephone: +86-21-81871060 Fax: +86-21-81871060
Received: October 22, 2009
Revised: November 5, 2009
Accepted: November 12, 2009
Published online: December 14, 2009

Ten hepatitis B virus (HBV) genotypes (A-J) and 34 HBV subgenotypes have been identified so far. HBV genotypes and subgenotypes have distinct geographical distributions, and have been shown to differ with regard to clinical outcome, prognosis, and response to interferon treatment. Infection with subgenotype A2 is frequently associated with high viral load, resulting in acute infection via horizontal transmission. Genotypes A and B are more sensitive to interferon treatment than genotypes D and C, respectively. Genotype B is more frequent in acute hepatitis than genotype C, whereas genotype C (C2) is more frequently associated with an increased risk of hepatocellular carcinoma (HCC), mostly cirrhotic, as compared with genotype B (B2). Genotype mixture is associated with high viral load and worse outcome of HBV infection. HBV mutations in the S genes, especially amino acids substitution at position 145 (G145R), are associated with immune escape, whereas mutations in the PreS or S genes which impair HBsAg secretion could present a risk to blood safety. HBV variants harboring mutations in the viral polymerase gene that confer resistance to nucleoside analogs may be selected during antiviral therapy. Different genotypes have distinct mutation patterns in the PreS and EnhII/BCP/Precore regions. PreS deletions, C1653T, T1753V, and A1762T/G1764A are associated with an increased risk of HCC. HCC-associated HBV mutants may not transmit via mother-to-child transmission, and are likely generated during HBV-induced pathogenesis. Examination of HBV mutations alone or in combination and host genetic susceptibility will be helpful in classifying the HBV-infected subjects who will develop HCC and need active anti-viral treatments.

Keywords: Hepatitis B virus, Genotype, Subgenotype, Mutation, Clinical, Public health, Evolution