Occurrence of AUSAB test positivity unrelated to prior exposure to hepatitis B virus

Positive AUSAB test results in the absence of all other serological markers for hepatitis B have been seen frequently in serial serum specimens from quarantined chimpanzees. In this study the responsible reactant was found to be similar to IgM in terms of both size and charge. After the inoculation of hepatitis B virus, AUSAB-positive and AUSAB-negative chimpanzees were found to be equally susceptible to hepatitis B infection. Thus, the presence of this reactant did not confer immunity to hepatitis B or modulate the course of the disease. At present, hepatitis B virus-seronegative chimpanzees are excluded from use in research on hepatitis B because of the occurrence of this "false-positive" AUSAB test result. It is likely that humans may be denied active or passive immunization for similar reasons.