An aberrant genotype revealed in recombinant hepatitis B virus strains from Vietnam

Six genotypes of hepatitis B virus (HBV) have been described. However, rela tively few complete genomes originating from East Asia, where most of the w orld's HBV carriers live, have been studied. We analysed five complete HBV genomes of Vietnamese origin, which in our previous studies had produced at ypical genotyping patterns. All five strains had HBsAg sequences with marke rs for serotype adw. In phylogenetic tree analysis, two of the genomes clus tered with genotype C, and three clustered on a separate branch between gen otypes A, B and C, suggesting a new genotype, However, these three strains showed signs of recombination in similarity plot and bootscanning analysis. Phylogenetic tree analysis of two segments separately supported recombinat ion between genotype C and a putative new genotype (or possibly a subgroup of genotype A). The segment between nt 1801 and 2865 was clearly of genotyp e C origin, while the major part of the genome (nt 2866-1800) was placed on a branch close to genotype A. The findings encourage further study of geno types and recombination in HBV from this geographical region.