2 NEW HUMAN MONOCLONAL-ANTIBODIES AGAINST HIV TYPE-1 GLYCOPROTEIN-120- CHARACTERIZATION AND NEUTRALIZING ACTIVITIES AGAINST HIV TYPE-1 STRAINS

Two human IgG(kappa) monoclonal antibodies (HuMAbs), termed 48-16 and 50-61A, were derived by Epstein-Barr virus transformation of B cells f rom two HIV-1-infected donors, These HuMAbs recognized discrete, nonov erlapping, and conformational or discontinuous epitopes on the gp120 e nvelope protein of HIV-1, The binding affinities of 48-16 and 50-61A f or recombinant gp120 from HIV-1(LAI) strain, reflected by their dissoc iation constants, were estimated to be 2-5 x 10(-9) and 2.4 x 10(-10) M, respectively, 48-16 was shown to react with a conserved determinant present on a variety of divergent laboratory isolates, residing outsi de the CD4-binding site and the V3 region, which remains to be determi ned, 48-16 did not display, however, any detectable functional activit y, 50-61A exhibited a more restricted recognition pattern, but was abl e to completely inhibit the 2 HIV-1 laboratory strains LAI and SF2 in a concentration range of 0.5-10 mu g/ml, as measured by an antigen cap ture assay, The ability of 50-61A to block the interaction between rec ombinant gP120(LAI) and recombinant as well as cellular CD4 indicated that 50-61A epitope was localized near or within the CD4-binding site, We also demonstrated that 50-61A- and 48-16-defined epitopes (or clos ely related epitopes) were immunogenic in infected humans, since serum samples from 45 seropositive subjects were able to inhibit both gp120 (LAI)-HuMAb recognitions, However, the presence of ''50-61A-like'') an tibodies in these sera could not be associated with their neutralizing activities of HIV-1(LAI) infection, Interest in producing such antibo dies for characterization of the human B cell repertoire to HIV-1 and their potential use in passive immunotherapy or vaccination strategy a gainst AIDS are discussed.