Isolation and characterization of the neutralizable epitope of simian retrovirus-1 (SRV-1) and of the cell receptor for the virus.

An area encompassing residues 142-167 of the envelope protein of type D simian retrovirus (SRV-1) has been shown to contain the epitope to which neutralizing antibodies are directed. This area has been synthesized and shown to bind to monkey and mouse antiviral antibodies and to a virus neutralizing mouse monoclonal antibody. Protein conjugates of this peptide as well as the cross-linked or the free peptide induce antibodies capable of neutralizing, in vitro, viral infectivity. The cell receptor to the virus was isolated following extraction of Raji cells with non-ionic detergents. The receptor was isolated and characterized following radioimmuno-precipitation of 125I labeled cell extract bound to viral envelope protein. This immunoprecipitation could be inhibited by antiserum to peptide 142-167. Analysis in gels indicate that the receptor is of molecular weight of approximately 60 KDa. These results indicate that the neutralizing antibodies and the receptor recognize the same area on the viral envelope protein and that neutralization is the result of blocking the virus-receptor interaction by antibodies.