Novel hepatitis B virus subgenotype in the southern Yunnan Province of China.

Hepatitis B virus (HBV) infection is highly prevalent in China. To identify the genotypes of HBV in the southern Yunnan Province of China, full-length HBV genomes were extracted from 1 Dai and 4 Hani HBV carriers and linked with the pMD T-18 vector. For each patient, 3-10 clones were sequenced directly and a consensus sequence was created. Genotypic and serotypic analysis revealed 4 HBV/B (2 B2 with adw2 and 2 new subgenotypes with ayw1) and 1 HBV/C (C1 with adrq+) genotypes. The divergences of the entire genome sequences of the new subgenotype were 0-0.9% and 2.99-6.48% between other known HBV/B. Divergences in other coding regions revealed that it was more similar to B3 and B4 in the precore/core gene (2.02 and 2.09%, respectively), and similar to B3 and B5 in the preS1/S2/S gene (2.24 and 2.78%, respectively). Phylogenetic trees using the precore/core and X genes both revealed a new clad separating from the major trunk of genotype B with a 99% bootstrap value. These results show that the 2 consensus isolates are a mosaic of B3-B5, which we designated to subgenotype B6. Considering the geographical distances, the relationship between B6 and other HBV/B subgenotypes (B3-B5) and HBV evolution needs to be further studied.