Immunogenic and antigenic properties of an HIV-1 gp120-derived multiple chain peptide.

An HIV-1 envelope protein gp120-derived monomeric peptide (amino acid residues 419-439) and its homologous multiple chain peptide (MCP) construct were compared for immunogenicity in mice. The Abs stimulated by the MCP recognized epitopes on the MCP that were not present on the homologous monomer. The anti-419-439 MCP sera recognized a conformational determinant on the native envelope glycoprotein, as indicated by: 1) detection of native but not denatured recombinant envelope glycoprotein by ELISA and dot blot and 2) reaction with infected cell lines expressing gp120 on their surface as detected by flow cytometry. In contrast, the anti-monomer sera were highly specific for the monomer and recognized the envelope glycoprotein at lower titers. The low reactivity of the anti-monomer sera with the envelope glycoprotein was not decreased by denaturation. Reciprocally, murine antiserum to HIV-1 envelope glycoprotein gp160 recognized the MCP construct but not the homologous monomeric peptide. The data indicate that the MCP construct forms additional antigenic determinants not present on the homologous monomer, and that the anti-419-439 MCP Abs recognize a conformational determinant on the envelope glycoprotein not recognized by Abs against the homologous monomer. Furthermore, antisera against another envelope-derived MCP (amino acid residues 105-117) also recognize conformational determinants on the envelope glycoprotein, whereas antisera against the homologous monomeric peptide do not.