Differential antibody responses of individuals infected with AIDS-associated retroviruses surveyed using the viral core antigen p25gag expressed in bacteria.

Infection with the retrovirus that is the etiological agent of acquired immune deficiency syndrome (AIDS) is characterized by the development of antiviral antibodies. To generate reagents for studying immune responses to individual viral proteins, we have produced viral antigens in microorganisms by recombinant DNA techniques. Large amounts of the major core protein (p25gag) of an isolate of the AIDS retrovirus (AIDS-associated retrovirus; ARV-2) have been directly expressed in Escherichia coli. Recombinant p25gag (R-p25gag) has been purified and used in an enzyme-linked immunosorbent assay (ELISA) for antibodies to p25gag. Serum samples obtained from 100 individuals with AIDS, AIDS-related complex (ARC), or potential exposure to the virus through sexual contact with AIDS or ARC patients (contacts) were tested first in an ELISA with disrupted whole virus to determine which of the subjects had mounted an antibody response to the virus (virus seropositive) and then in the p25gag ELISA to determine if they had antibodies to this particular viral antigen. We observed a decrease in the proportion of virus seropositive individuals with antibodies to p25gag among patients groups in which the disease was more advanced; contacts were often positive (71%), ARC patients less frequently positive (48%), and AIDS patients only rarely positive (16%). Our results suggest that monitoring p25gag seropositivity of infected individuals may be useful for predicting either the prognosis or the stage of the disease.