Genotypes, subtypes, and genetic variability of hepatitis B virus from blood donors in Timor-Leste

Timor-Leste experiences high hepatitis B endemicity; however, information about hepatitis B virus (HBV) variants in Timor-Leste is still limited. In this study, we determined genotypes and subtypes and identified mutations in the surface (S), polymerase (P), basal core promoter (BCP), precore (PC), and core (C) genes of HBV isolates from blood donors in Timor-Leste. Sera were examined using serological tests and PCR sequencing. Out of 127 sera tested, 38 (30%) were positive for the hepatitis B S antigen (HBsAg). Thirty-eight sequences of the S and P genes, 22 sequences of the BCP and PC regions, and 23 sequences of C genes were determined and analyzed. The most common genotype/subtype was C/adrq+, followed by B/ayw1, B/adw2, and C/adw2. Several mutations in the S protein that are associated with vaccine escape were identified in samples of genotype C (I110L, S113T, T126I, T143S, Y161F) and B (K122R), some of which might have been from vaccinated individuals. None of the healthy carriers had taken anti-HBV drugs, but one was infected with a virus with a mutation in the P gene associated with anti-HBV drug resistance (Y141F). The mutations A1762T and G1764A in BCP were detected in 18.1-22.7% of the samples. In the PC region, the mutation C1858T was the most frequent, followed by G1896A and G1899A. In the C gene, 13 mutations (P5T, T67N, E77Q, P79Q/A, E83D, V91T, I97L/F, L116I, and P130I/P/T) associated with severe liver disease were identified. Viruses obtained from four healthy carriers who were later found to have died of hepatocellular carcinoma also showed those mutations. In conclusion, among blood donors in Timor-Leste, HBV genotype/subtype C/adrq+ and several mutations in the S and C genes were prevalent. Routine implementation of a national immunization program and monitoring of disease progression in healthy carriers should be considered.