Phylogenetic analyses of the complete genome showed that HBV from the baboon was closely related to HBV subgenotype A2 (Figure 3). This finding was confirmed by comparison of mean ± SD nucleotide divergence calculations compared to subgenotype A2 (1.00 ± 0.55) and to subgenotype A1 (4.52 ± 0.42). Similar results were obtained for each of the 4 open reading frames. The baboon HBV had mutations in the basic core promoter and precore regions not found in subgenotype A2. These mutations included the G1809T/C1812T double mutation in the Kozak sequence preceding the precore protein start codon and G1888A in the precore region. G1809T/C1812T mutations are characteristic of subgenotype A1, and G1888A is unique to subgenotype A1 (4,24). Translation of the 4 open reading frames showed them to be well conserved relative to the consensus sequence of subgenotype A2 with the following exceptions: T380C resulting in an rtV84A in conserved region A of the polymerase and a C76R in HBsAg; A2019G resulting in an E40G in the core protein; and C1470T resulting in a P33G in the X protein and T1765C resulting in a P145S in the X protein.
Expression of HBV RNA in Baboon Liver Tissue