Human immunodeficiency virus contains an epitope immunoreactive with thymosin alpha 1 and the 30-amino acid synthetic p17 group-specific antigen peptide HGP-30.

We have reported that an antiserum prepared against thymosin alpha 1 [which shares a region of homology with the p17 protein of the acquired immunodeficiency syndrome (AIDS)-associated human immunodeficiency virus] effectively neutralized the AIDS virus and prevented its replication in H9 cells. Using HPLC and immunoblot analysis, we have identified from a clone B, type III human T-lymphotropic virus (HTLV-IIIB) extract a protein with a molecular weight of 17,000 that is immunoreactive with thymosin alpha 1. In contrast, no immunoreactivity was found in retroviral extracts from a number of nonhuman species including feline, bovine, simian, gibbon, and murine retroviruses. Heterologous antiserum prepared against a 30-amino acid synthetic peptide analogue (HGP-30) does not cross-react with thymosin alpha 1 but does react specifically with the p17 protein of the AIDS virus in a manner identical to that seen with an HTLV-IIIB p17-specific monoclonal antibody. The demonstration that this synthetic analogue is immunogenic and that antibodies to HGP-30 cross-react not only with the synthetic peptide but also with the HTLV-IIIB p17 viral protein provides an additional, and potentially more specific, candidate for development of a synthetic peptide vaccine for AIDS. In addition, the p17 synthetic peptide (HGP-30) may prove to be useful in a diagnostic assay for the detection of AIDS virus infection in seronegative individuals.