Characterization of a feline sarcoma virus-coded antigen (FOCMA-S) by radioimmunoassay.

Abstract
A radioimmunoassay was developed that detects a unique antigen encoded by the genome of the feline sarcoma virus (FeSV). Pseudotype viral particles containing an FeSV-specific polyprotein (p85) were used both as a source of antigen and to prepare specific antisera in rabbits. Because p85 contains antigens related to 2 structural proteins (p15 and p12) of feline leukemia virus (FeLV), antibodies directed to these were adsorbed with purified FeLV proteins. The adsorbed rabbit antiserum bound to antigenic determinants (designated FOCMA-S) which are also present in p85 and reacted specifically in immunofluorescence tests with rat cells transformed by FeSV and with FOCMA[feline oncornavirus associated cell membrane antigen]-positive cat lymphoid tumor cells. Competition assays detect FOCMA-S in pseudotype type C viruses rescued from FeSV-transformed mink and rat cells but not in heterologous type C helper viruses or in FeLV. A crossreactive antigen was also detected in pseudotypes of Kirsten sarcoma virus. The assay permits the quantitative measurement of an FeSV-coded protein whose expression is associated with viral transformation.