Biologically active epitopes of bovine leukemia virus glycoprotein gp51: their dependence on protein glycosylation and genetic variability.

A panel of monoclonal antibodies to the bovine leukemia virus envelope glycoprotein (BLV gp51) has previously demonstrated the association of the biological activities of the virus (infectivity, syncytia induction) with three out of eight epitopes of gp51. In BLV-infected cells, the unglycosylated homolog of the precursor to the BLV envelope glycoproteins (gPr72env) is a 47,000-MW polypeptide. Immunoprecipitation studies with monoclonal antibodies show that the neutralizing antibody-inducing sites, although present in gPr72env, are not conserved in the 47,000-MW unglycosylated homolog. Finally, it is demonstrated that the neutralizing antibody-inducing sites of gp51 are subject to antigenic variation among BLV isolates of the same or different geographical origins.