The dominant hepatitis B virus genotype identified in Tibet is a C/D hybrid

There are no reports on DNA sequences of hepatitis B virus (HBV) strains from Tibet, although this highland area has a high HBsAg-positive population. We characterized HBV isolates from sera of 26 HBsAg-positive Tibetans. To determine the HBV genotypes and their phylogenetic relationships, we sequenced two genomic regions, one including the pre-S1/pre-S2/S region and the other including the pre-C/C region. The sequences were classified into two different genotypes based on different regions of the genome, except for one isolate. To clarify this finding, two complete HBV genomes that represented the two groups of isolates were sequenced. From the sequencing results, we concluded that HBV strains in Tibet may be classified as genotype C, and there are at least two subgroups. The dominant subgroup is a C/D hybrid with serotype ayw2, and the other is genotype C with serotype adw. This is the first report of complete nucleotide sequences of HBV from Tibet. These results contribute to the investigation of recombinant HBV strains throughout the world and should encourage further study of genotypes and recombination in HBV from this particular region.