Model of the functioning of the V3 loop central epitope of HIV-1 gp120 in complex with antibodies

The influence of the amino acid sequence of the gp120 V3 loop central epito pe of HIV-1 variants and V3-mimicking synthetic peptides on their interacti on with antisera was studied by ELISA. A model is proposed to describe the interaction of 10 residues of the central epitope with antibodies, whereby the specificity is determined by residues at positions 315 and 320 (numerat ion for HIV-1(MN)) and depends on the hydrophobicity of residues 314, 316, and 321-323. Analysis of the pertinent sequences in various subtypes of HIV -1 group M (database of the Los Alamos National Laboratory, 1996) showed th at the most frequent are residue combination that enhance the efficacy of e pitope interaction with Fab. The mechanism of epitope functioning in the an tibody complex appears to be also realized during virus penetration into th e target cell.