Complex structural variations in non-human primate hepatitis B virus

Recent genome sequence technology has revealed a novel type of genetic rearrangement referred to as complex structural variations (SVs). Previous studies have elucidated the complex SVs in human hepatitis B viruses (HBVs). In this study, we investigated the existence of complex SVs in HBVs from non-human primates (NHPs). Searches for nucleotide sequences of NHP HBV were conducted using the PubMed, and genetic sequences were retrieved from databases. The candidate genetic sequences harboring complex SVs were analyzed using the CLUSTALW program and MAFFT. Additional bioinformatical analyses were performed to determine strains with complex SVs and to elucidate characteristics of NHP HBV strains. One hundred and fifty-four HBV strains from NHPs were identified from databases. SVs and complex SVs were observed in 11 (7.1%) strains. Three gibbon HBV (GiHBV) strains showed complex SVs consisting of an insertion and a deletion in the pre-S1 region. One GiHBV strain possessed a 6-nt insertion, which are normally specific to human HBV genotype A (HBV/A) in the Core region, and further analyses clarified that the 6-nt insertion was not caused by recombination, but rather by simple insertion. Another chimpanzee HBV strain showed complex SVs in the pre-S1 region, which were composed of human HBV/E, G-specific polymorphic SV, and an additional 6-nt insertion. In this study, complex SVs were observed in HBV strains from NHPs, in addition to human HBV strains, as shown in previous studies. These data suggest that complex SVs could also be found in other members of hepadnaviruses, and may play a role in their genetic diversity.