Baboon serum samples were tested for HBsAg and for antibodies against HBV core antigen (anti-HBc) by using commercially available assays (Abbott Laboratories, Abbott Park, IL, USA). Alanine and aspartate aminotransferase levels were measured by using a 747 Automatic Analyzer (Hitachi, Tokyo, Japan).
Formalin-fixed liver tissue from baboon 9732 was used for histologic and immunohistologic preparations. Liver tissue was embedded in paraffin and sectioned. The sections were stained with hematoxylin and eosin for histologic examination or with immunoperoxidase and polyclonal antibodies to HBsAg and HBV core antigen (HBcAg) to detect HBsAg and HBcAg in hepatocytes.