Natural and experimental infection of woodchucks with woodchuck hepatitis virus, as measured by new, specific assays for woodchuck surface antigen and antibody.

Solid-phase radioimmunoassays for woodchuck hepatitis virus (WHV) surface antigen (WHsAg) and antibody to it (anti-WHs) were developed. The test for WHsAg could detect as little as 10 ng/ml. In both tests it was necessary to employ radiolabeled WHsAg instead of anti-WHs as the probe because the latter appeared to be labile to the conditions of labeling. The tests were used to characterize naturally acquired and experimental WHV infections of woodchucks. Forty-three of 72 wild-caught woodchucks had serological evidence of WHV infections; 16 of these resulted in chronic infection, and the remainder were self-limiting. All chronically infected animals were positive for WHsAg and DNA polymerase activity. During 3 years of observation, 11 of the 16 WHsAg-positive animals and 3 of the 27 anti-WHs-positive animals, but none of the 21 uninfected animals developed hepatocellular carcinoma. Seroconversion, possibly resulting from infection with WHV, was documented in a chimpanzee inoculated with WHV. An immune adherence hemagglutination test for WHsAg was also developed by using anti-WHs of chimpanzee origin as a reagent, but the test was not useful for detecting anti-WHs of woodchuck origin because of the lability of the latter.