A CONSERVED NEUTRALIZING EPITOPE ON GP41 OF HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1

Vaccination against human immunodeficiency virus type 1 (HIV-1) requir es an immunogen which will elicit a protective immunity against viruse s that show a high degree of genetic polymorphism. Therefore, the iden tification of neutralizing epitopes which are shared by many strains w ould be useful. In previous studies, we established a human monoclonal antibody (2F5) that neutralizes a variety of laboratory strains and c linical isolates of HIV-1. In the present report, we define the amino acid sequence Glu-Leu-Asp-Lys-Trp-Ala (ELDKWA) on the ectodomain of gp 41 as the epitope recognized by this antibody. The sequence was found to be conserved in 72% of otherwise highly variable HIV-1 isolates. Es cape mutants were not detected in cells infected with HIV-1 isolates M N and RF in the presence of antibody 2F5. Since sequence variability o f neutralizing epitopes is considered to be a major obstacle to HIV-1 vaccine development, the conserved B-cell epitope described here is a promising candidate for inclusion in a vaccine against AIDS.