Molecular epidemiological study of hepatitis B virus genotypes in Southwest, China.

Hepatitis B virus (HBV) is highly endemic in Southwest China; an area with many ethnic minorities. Information about the genetic distribution of HBV is still limited. In 2010, a multistage cluster sampling method was carried out in the Southwest China. Five hundred forty serum samples of participants were collected. Polymerase chain reaction followed by nucleotide sequencing of parts of the HBV S and C genes was performed. HBV genotype and subgenotype were determined. Recombination analysis was carried out. HBV infectious markers, HBV DNA and mutations in the basic core promoter (BCP) A1762T/G1764A and G1896A were analyzed. The results show us that HBV genotypes C/D recombinant (38.6%), B (31.6%), and C (23.3%), were predominant in Southwest China. C/D4 (96.8%) was endemic in the Tibetan and B2 (43.5%) in Han, and C1 (66.7%) was predominant in the Yi minority. 67.5% (56/83) of genotype C/D was Hepatitis B surface antigen (HBsAg) positive/Hepatitis B e antigen (HBeAg) positive/HBV DNA≥20,000 IU/ml, BCP A1762T/G1764A double mutation was frequent in genotype C and C/D, and G1896A was frequent in B and B/C. Thus, HBV genotypes distribution differed significantly in area and minority in Southwest China. C/D recombinant is endemic in the Tibetan, while B, C genotypes are predominant in Han minority. C/D recombinant exhibits higher frequency with HBeAg positive, high level of HBV DNA and BCP A1762T/G1764A double mutation.