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Comparison of HIV1Bru and HIV2Rod external envelope glycoprotein sequences enabled us to select ten highly conserved peptide sequences. The corresponding peptides were chemically synthesized, then coupled to bovine serum albumin before injection in rabbits. Although all peptides were immunogenic, only antibodies directed against peptides P1 (amino acid residues 33-55), P22 (418-462), P8 (487-508) and P21 (487-534) were able to interact with significant affinity (K0.5 about 10(-6) to 10(-8) M) with the native glycoprotein by radioimmunoassay. Noteworthy was the capacity of anti-P1 antibodies to also recognize the glycoprotein of HIV2. Anti-peptide antibodies were tested for their ability to interfere with the gp120-CD4 interaction, membrane fusion and virus replication. Preincubation of gp120 with antibodies directed to the region previously described as the putative CD4-binding site, P22 (418-462), did not abolish gp120 binding to CD4-positive cells.

The effect of carbohydrate structures on the adsorption of HIV-1 or of recombinant envelope glycoprotein gp 160 (rgp 160) to cells of the CEM line was investigated with an indirect immunofluorescence assay using gp 120-specific mouse monoclonal antibodies (mAbs) directed to envelope gp 120. The beta-D-galactosyl, alpha-D-mannosyl, beta-D-glucosyl, N-acetyl-beta-D-glucosaminyl, sialosyl, and L-fucosyl derivatives tested had no effect on this binding. However, preincubation of HIV-1 (or rgp 160) with the neoglycoprotein, beta-D-GlcNAc47-BSA, specifically inhibited the labeling, by some of the mAb used, of HIV-1 (or rgp 160) bound at the cell membrane. This inhibition occurred only with mAbs that were specific for the immunodominant "neutralizing" third variable region (V3) of gp 120. Competition for the binding to rgp 160 between beta-D-GlcNAc47-BSA and mAb was further demonstrated by use of affinity matrices substituted with one of the relevant mAb (110-4), or with beta-D-GlcNAc47-BSA. Besides beta-D-GlcNAc47-BSA-Sepharose, rgp 160 also bound with low affinity, but high specificity, to two other N-acetyl-beta-D-glucosaminyl affinity matrices, beta-D-GlcNAc-divinylsulfone-agarose and asialoagalactothyroglobulin-agarose. Conversely, beta-D-[125I]GlcNAc47-BSA bound specifically to gp 160-Sepharose. These results indicated that rgp 160 behaves as a N-acetyl-beta-D-glucosaminyl-binding protein for GlcNAc residues presented at high density on a carrier, the carbohydrate-binding site of which is close to, or located on the V3 region of gp 120.