Evaluation of a chimpanzee colony for antibodies to hepatitis C virus

The chimpanzee is the only species other than man that is generally susceptible to infection by hepatitis C virus (HCV). Aspects of future studies on vaccines and therapeutics for HCV may continue to depend on the chimpanzee. In an attempt to determine the HCV status of the animals in a chimpanzee colony, the recently developed enzyme immunoassay (EIA) for antibodies to HCV was used. The results of the assay indicated that only 31.3% of the animals that had previously been inoculated with a non‐A, non‐B hepatitis agent were currently positive in the assay. A retrospective analysis suggested that an additional 20% of the chimpanzees had been positive at some time following infection. Seroconversion to an anti‐HCV antibody response using this assay did not appear to correlate with the severity of the initial disease or the development of chronic liver damage. Examination of the EIA‐positive samples using the second generation recombinant immunoblot assay (RIBA) containing four HCV antigens suggested that chimpanzees responded differentially to these antigens. Examination of serum samples from 139 uninoculated animals by EIA revealed seven positive samples and ten samples with borderline values. The nature of the reactivities in most of the positive samples could not be resolved, but analysis by RIBA indicated that at least one animal in the breeder colony had been exposed to HCV. Due to the low seroconversion rate and the uncertainties surrounding many of the positive reactions, this assay cannot be used to determine the initial source or extent of spread of HCV infections in the uninoculated animals.