Multiple antigenic determinants on the major surface glycoprotein of murine mammary tumor viruses

The major external protein of murine mammary tumor viruses (MMTVs) is a glycoprotein of molecular weight 52,000 (gp52). We report here that the gp52s of MMTVs from different mouse strains contain both type-specific and group-specific antigenic determinants. Competitive radioimmunoassays with externally labeled virion preparations were used to demonstrate that MMTV virions from C3H, RIII, and GR mice competed identically in "group-specific" assays but either competed with altered slopes or competed incompletely in the appropriate "type-specific" assays. Similar results were obtained with purified gp52 preparations as competitors. MMTVs of RIII, C3H, and GR mice, grown in feline cells, competed similarly to the corresponding murine-derived MMTVs, thus demonstrating that the observed type-specific and group-specific antigenic reactivities are viral coded. In competitive radioimmunoassays using an antiserum against MMTV of C3H mice that was preabsorbed with MMTV of GR mice, type-specific reactivities were further magnified; MMTV of C3H mice competed completely whereas no competition was observed with MMTV of GR mice as a competitor. These studies are in agreement with previous biological and molecular hybridization studies on the diversity of MMTVs from different mouse strains.