Construction of prokaryotic expression vectors for the production of high levels of human immunodeficiency virus-1 (HIV-1)- and human T-cell leukemia virus-I (HTLV-1)-specific proteins has been accomplished. Using these systems, eight HIV-envelope-specific polypeptides have been expressed at high levels and have been purified to near homogeneity. Using these purified proteins as antigens, it has been possible to elicit specific polyclonal and monoclonal antibodies against these specific retroviral proteins that are able to react against the authentic cellular proteins in vivo. One clone, 566, expresses a protein which is highly immuno- reactive after a 1OO,OOO-fold dilution of acquired immunodeficiency syndrome (AIDS)-positive human sera; further, this antigen is able to recognize all HIV-positive sera by enzyme-linked immunosorbent assay (ELISA) testing and is as sensitive in these assays as the natural gp41 viral env-encoded protein. We have also expressed a portion of the HIV-genome encoding the non-structural proteins 3'- orf and sor in our prokaryotic vector systems. We have been able to obtain specific antibodies, using these reagent-antigens, that recognize the native viral product in HIV-infected cellular systems. Our monoclonal antibody against the HIV-1 3'-orf also recognizes the bacterially-expressed HIV-2 3'-orf polypeptide and preliminary studies using the expressed 3'-orf for biochemical analysis shows that the HIV-2 3' orf is capable of binding guanosine triphosphate (GTP). Our bacterially expressed sor protein has been used to screen a panel of sera from homosexual men that showed no reactivity to commercial HIV-antigens; five out of nine individuals tested prior to seroconversion were positive in a Western immunoblot assay using the bacterially-expressed sor product. These results would suggest that sor may be a valuable reagent to employ for the immunodiagnosis of HIV-reactivity during preclinical stages of infection.