MAPPING OF EPITOPES EXPOSED ON INTACT HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 (HIV-1) VIRIONS - A NEW STRATEGY FOR STUDYING THE IMMUNOLOGICAL RELATEDNESS OF HIV-1

To study the antigenic conservation of epitopes of human immunodeficie ncy virus type 1 (HIV-1) isolates of different clades, the abilities o f human anti-HIV-1 gp120 and gp ll monoclonal antibodies (MAbs) to bin d to intact HIV-1 virions were determined by a newly developed virus-b inding assay. Eighteen human anti-HIV MAbs, which were directed at the V2, V3 loop, CD4-binding domain (CD4bd), C5, or gp41 regions, were us ed. Nine HIV-1 isolates from clades A, B, D, F, G, and H were used. Mi crotiter wells were coated with the MAbs, after which virus was added. Bound virus was detected after lysis by testing for p24 antigen with a noncommercial p24 enzyme-linked immunosorbent assay. The anti-V3 MAb s strongly bound the four clade B viruses and viruses from the non-B c lades, although binding was weaker and more sporadic with the latter, The degrees of binding by the anti-V3 MAbs to CXCR4- and CCR5-tropic v iruses were similar, suggesting that the V3 loops of these two categor ies of viruses are similarly exposed, The anti-C5 MAbs bound isolates of clades A, B, and D. Only weak and sporadic binding of all the virus es tested with anti-CD4bd, anti-V2, and anti-gp41 MAbs was detected. T hese results suggest that V3 and C5 structures are shared and well exp osed on intact virions of different clades compared to the CD4bd, V2, and gp41 regions.