Susceptibility of chacma baboons (Papio ursinus orientalis) to infection by hepatitis B virus

Background. Because baboons are being considered as a source of xenografts for human liver transplantation in patients with hepatitis B virus- (HBV) induced cirrhosis to forestall infection of the graft by the virus, we undertook a study to ascertain if baboons are resistant to HBV infection. Methods. Six chacma baboons were inoculated with serum containing HBV and were followed for 52 weeks to detect transmission of infection. Results. Anti-HBc was detected in the serum of four baboons 16 weeks after inoculation. Virions, small spherical particles, and tubular forms were seen at this time in the serum of the one baboon studied by transmission electron microscopy. HBV DNA was detected by polymerase chain reaction in the serum of the same four baboons throughout the period of follow-up, as well as in liver tissue obtained after 52 weeks. The specificity of the DNA was confirmed by Southern hybridization. Nucleotide sequences showed complete sequence identity between the HBV DNA in each of the baboon sera and one of the two HBV genotypes inoculated. Serum transaminase levels tested at 4-weekly intervals were always normal and histological examination of liver tissue after 52 weeks showed no evidence of chronic hepatitis. Examination of squash preparations of liver tissue by electron microscopy in one baboon revealed core-like particles. Conclusions. Chacma baboons are susceptible to HBV infection and appear to develop a chronic carrier state. The use of xenografts from baboons should preferably be avoided, but if they are used again for HBV-infected patients it would be prudent to treat the patients as if they had received an organ from a human donor.