Discrimination between HIV-1 and HIV-2-seropositive individuals using mouse monoclonal antibodies directed to HIV transmembrane proteins

Mouse monoclonal antibodies directed against the transmembrane proteins of HIV-1 or HIV-2 provided site-directed, unambiguous discrimination between HIV-1 and HIV-2 antibody-positive sera, when employed in immunoassays as competitive probes against serum antibodies. These monoclonal antibodies mapped to epitopes outside of the well-characterized immunodominant regions (IDR) of the transmembrane proteins. The monoclonal competitive immunoassay was a superior method for discrimination compared with immunoprecipitation of metabolically radiolabeled HIV envelope glycoproteins, Western blot against viral envelope glycoproteins, or noncompetitive enzyme immunoassays employing HIV recombinant transmembrane proteins or synthetic IDR peptides as serological targets. The monoclonal competitive assay was not affected by antigenic cross reactivity or nonspecific reactivity exhibited by selected serum samples toward envelope proteins or peptides, respectively. Results of the monoclonal competitive immunoassay were supported by results of a peptide inhibition assay employing free IDR peptides in competition with IDR peptides on a solid support for binding of serum antibody. IDR peptide inhibition clearly demonstrated non-cross-reactive antigenic specificity of sera toward either the HIV-1 IDR or the HIV-2 IDR. The monoclonal competitive assay also identified samples containing antibody to both HIV-1 and HIV-2 transmembrane proteins. Analysis of these samples by IDR peptide inhibition indicated they contained two distinct, non-cross-reactive populations of antibodies, one directed to the HIV-1 IDR and the other directed to the HIV-2 IDR.