[Molecular evolutionary analysis of hepatitis B virus (HBV) and genetic classification]

HBsAg of Hepatitis B virus (HBV) has been classified into four major subtypes (adw, adr, ayw, ayr) by the serological methods. Using molecular evolutionary analysis technique, we constructed the phylogenetic tree for the partial S gene (HBsAg gene) of HBV. The tree shows that 51 strains of HBV can be classified into following four genetic subgroups: (1) strains of subtypes ayw and adyw, (2) those of adw and adr, (3) another of adw, and (4) other subgroup of adr, adw, ayr, ar and ad. We propose that these subgroups be designated gyw, gdw-1, gdw-2, and gdr, respectively, with "g" standing for genetic classification. It is important that the genetic classification of HBVs is not always compatible with conventional serological subtypes. It is possible that the conventional subtypes do not represent a classification according to the degree of genetic difference among strains of HBVs. Thus, our genetic classification is more suitable for studies of epidemiological and virological features of HBVs.