Full genome characterization and phylogenetic analysis of hepatitis B virus in gibbons and a caretaker in Central Kalimantan, Indonesia

Hepatitis B virus (HBV) from gibbons was characterized, and the possibility of horizontal transmission between gibbons and humans was examined in a gibbon rehabilitation center in Central Kalimantan, Indonesia. Ten gibbons that were positive for the hepatitis B surface antigen (HBsAg) on arrival and 13 caretakers for those gibbons were included in this study. The duration of stay at the rehabilitation center ranged from 1 to 10 years. Serological and molecular analyses were performed. Six gibbons were positive for HBsAg, whereas HBV DNA was detected in all ten of the gibbons sampled. On the other hand, HBsAg was detected in only 1 of the 13 caretakers. HBV samples from seven gibbons and from the one infected human were chosen for complete genome sequencing. A phylogenetic analysis revealed that the cluster of gibbon strains in this study was distinct from strains previously reported from other countries. In the pre-S1 region, we found a unique amino acid residue substitution (P89K), three insertions between T87 and L88 in the genomes of three gibbons, and a 33-nucleotide deletion at the start of pre-S1 that is common in non-human primates. The caretaker sample was identified as HBV subgenotype B3, the most common type in Indonesia. For the complete HBV sequences, the similarity between gibbons in this study and other non-human primate and human HBV isolates was 90–91.9 % and 85.5–89.6 %, respectively. In conclusion, the gibbon HBV genotype was influenced by geographic location and species. To the best of our knowledge, this is the first report characterizing the HBV genes and genomes of indigenous gibbons in Indonesia.