Immunological characterization of the gag gene products of bovine immunodeficiency virus

The bovine immunodeficiency virus (BIV) gag gene encodes a 53-kDa precursor (Pr53Yq) that is involved in virus particle assembly and is further processed into the putative matrix (MA), capsid (CA), and nucleocapsid (NC) functional domains in the mature virus. Gag determinants are also found in the Gag-Pol polyprotein precursor. To immunologically identify the major precursors and processed products of the BIV gag gene, monospecific rabbit sera to recombinant BIVMA protein and Pr5315g and peptides predicted to correspond to the CA and NC proteins and the MA-CA cleavage site were developed and used in immunoprecipitations and immunoblots ofBIV antigens. Monospecific antisera to native and recombinant human immunodeficiency virus type 1 proteins were also used to identify analogous BIV Gag proteins and to determine whether cross-reactive epitopes were present in the BIV Gag precursors or processed products. The BIV MA, CA, and NC Gag proteins were identified as p16, p26, and p13, respectively. In addition to BIV Pr531"9, the major Gag precursor, two other Gag-related precursors of 170 and 49 kDa were identified that have been designated pPr17091'85PI and Pr49ag, respectively; pPr179fa"Pl is the Gag-Pol polyprotein precursor, and Pr49B"9 is the transframe Gag precursor present in pPrI700a'"*. Several alternative Gag cleavage products were also observed, including p23, which contains CA and NC determinants, and plO, which contains a peptide sequence conserved in the CA proteins of most lentiviruses. The monospecific antisera to human immunodeficiency viru