SPECIFICITY AND NEUTRALIZING CAPACITY OF 3 MONOCLONAL-ANTIBODIES PRODUCED AGAINST THE ENVELOPE GLYCOPROTEIN OF SIMIAN IMMUNODEFICIENCY VIRUS ISOLATE-251

Three mouse monoclonal antibodies (mAb) were produced against soluble recombinant vaccinia virus gp140 from SIV-mac251. Two mAbs (1B9 and 6C 11) were mapped at the aa 411-430 sequence within the V4 domain, and t he third mAb (3C8) recognizes a conformation-dependent epitope on the external envelope glycoprotein. This was shown by its loss of reactivi ty in Western blot and ELISA with dithiothreitol-reduced gp140. mAb 3C 8, but not 1B9 and 6C11, cross-reacts well with gp140 and gp125 from H IV-2ROD, indicating that this discontinuous epitope includes conserved regions localized within the external envelope glycoprotein. Analysis of the neutralizing activities of the mAbs showed that only mAb 1B9 i s able to inhibit both syncytium formation and SIVmac251 infection of human peripheral blood lymphocytes. (C) 1995 Academic Press, Inc.