Linear B-cell epitopes of the major core protein of human immunodeficiency virus types 1 and 2.

Nine murine monoclonal antibodies directed to the major core protein p24 of human immunodeficiency virus type 1 (HIV-1) were obtained and then tested by using an epitope mapping system (Pepscan) covering the whole p24HIV1 protein to characterize antigenic domains. Four different linear epitopes were identified. Monoclonal antibodies recognizing three of these epitopes also reacted to p26HIV2 in Western blotting (immunoblotting). A monoclonal antibody specific for the fourth epitope, located at position 179 to 188 of the gag polyprotein p55HIV1 (human T-cell lymphotropic virus type 3B strain), did not react with HIV type 2 (HIV-2) core proteins. The corresponding sequence is constant in all known HIV-2 and simian immunodeficiency virus (SIV) isolates, including a very divergent SIV strain from African green monkeys (SIVagm/tyo). This observation may be relevant to the phylogeny of primate lentiviruses. Two of the conserved epitopes might be immunogenic during natural infection and could therefore be used for diagnosis and prognosis purposes. These two epitopes are AAEWDRVHP and EIYKRWII, starting at positions 209 and 260 of the polyprotein p55HIV1, respectively.