Molecular epidemiology of hepatitis B virus variants in nonhuman primates

We characterized hepatitis B virus (HBV) isolates from sera of 21 hepatitis B virus surface antigen-positive apes, members of the families Pongidae an d Hylobatidae (19 gibbon spp., 1 chimpanzee, and 1 gorilla). Sera originate from German, French, Thai, and Vietnamese primate-keeping institutions. To estimate the phylogenetic relationships, we sequenced two genomic regions, one located within the pre-S1/pre-S2 region and one including parts of the polymerase and the X protein open reading frames. By comparison with publi shed human and ape HBV isolates, the sequences could be classified into six genomic groups. Four of these represented new genomic groups of gibbon HBV variants. The gorilla HBV isolate was distantly related to the chimpanzee isolate described previously. To confirm these findings, the complete HBV g enome from representatives of each genomic group was sequenced. The HBV iso lates from gibbons living in different regions of Thailand and Vietnam coul d be classified into four different phylogenetically distinct genomic group s. The same genomic groups were found in animals from European toes. Theref ore, the HBV infections of these apes might have been introduced into Europ ean primate-keeping facilities by direct import of already infected animals from different regions in Thailand. Taken together, our data suggest that HBV infections are indigenous in the different apes, One event involving tr ansmission between human and nonhuman primates in the Old World of a common ancestor of human HBV genotypes A to E and the ape HBV variants might have occurred.