Last update:
06-Feb-2008

Hepatitis B virus (HBV) is of the most common pathogens that infect human and non-human primates, and which may cause either acute or chronic infection. The uniquity of the HBV virus lies in the fact that it possesses a partially double-stranded DNA genome and the virus life cycle contains an intermediate reverse transcription stage catalyzed by the viral reverse transcriptase. Because of this and the ability of the virus to recombine, HBV exhibits a wide range of genetic heterogeneity. The global distribution of HBV genotypes as described by molecular epidemiology shows that there is a specific geographic model which is probably associated with the models of transmission and, mainly, with the origin and the evolutionary history of the virus. As far as the scenario of zoonosis is concerned, it should be noted that HBV has been isolated from non-human primates but not from old world monkeys. Regarding the association between genotype and phenotype, other differences have been observed as far as the prevalence of mutations which are connected with important viral biological properties are concerned, such as precore mutants and basal core promoter mutants. There are also explicit indications that recombination affects the biological properties of HBV, since recombinant strains possess properties which constitute a combination of the properties of the parental strains. HBV genotypes, apart from genomic differences, also appear to differ considerably also in their biological properties. HBV genotypes may play an important role in the pathogenesis of hepatitis B, in the responses to antiretroviral therapy, such as the manifestation of hepatic cirrhosis and the evolution to hepatocellular carcinoma, and in the response to treatment with interferon.

Key words: Genotypes, Hepatitis B virus, Molecular epidemiology, Recombination, Serotypes.