Production and characterization of a mouse monoclonal antibody against the Gag p26 protein of human immunodeficiency virus type 2: identification of a new antigenic epitope.

One anticapsid (p26) mouse monoclonal antibody was developed after immunization with recombinant p26 Gag protein and was tested for reactivity with different HIV-1 and HIV-2 isolates by ELISA and Western blot analysis. This antibody, named R26.1, reacted with all HIV-2 isolates tested and with recombinant p26 proteins, but no HIV-1 isolates. The epitope of antibody R26.1 was mapped to residues 50-71 in the N-terminal domain of the capsid protein, a highly conserved region in all HIV-2 isolates sequenced to date. This monoclonal antibody may be useful for the detection of HIV-2, and for the discrimination between HIV-1 and HIV-2 infections. Likewise, the identified epitope may be useful for the detection of p26 antibodies in HIV-2-infected individuals.