title: Antigenic and immunogenic characteristics of nuclear and membrane-associated simian virus 40 tumor antigen.
abstract: Antisera were prepared in syngeneic hosts against subcellular fractions of simian virus 40 (SV40)-transformed cells (MoalphaPM, MoalphaNuc), glutaraldehydefixed SV40-transformed cells (HaalphaH-50-G, MoalphaVLM-G), and electrophoretically purified denatured SV40 tumor antigen (T-ag) (RaalphaT). Immune sera were also collected from animals bearing tumors induced by SV40-transformed cells (HaalphaT, MoalphaT, HAF) and from SV40-immunized animals that had rejected a transplant of SV40-transformed cells (HaalphaS, MoalphaS). Immunological reagents prepared against cell surface (MoalphaPM, HaalphaS, MoalphaS, HaalphaH-50-G, MoalphaVLM-G) reacted exclusively with the surface of SV40-transformed cells by indirect immunofluorescence or protein A surface antigen radioimmunoassay. Immunological reagents prepared against the nuclear fraction (MoalphaNuc) or whole-cell determinants (HaalphaT, MoalphaT, HAF, RaalphaT) reacted with both the nuclei and surface of SV40-transformed or -infected cells. All reagents were capable of immunoprecipitating 96,000-molecular weight large T-ag from solubilized whole cell extracts of SV40-transformed cells. The exclusive surface reactivity of HaalphaS exhibited in immunofluorescence tests was abolished by solubilization of subcellular fractions, which then allowed immunoprecipitation of T-ag by HaalphaS from both nuclear and plasma membrane preparations. Specificity was established by the fact that all T-reactive reagents failed to react in serological tests against chemically transformed mouse cells, and sera from mice bearing transplants chemically transformed mouse cells (MoalphaDMBA-2) failed to react with SV40-transformed mouse or hamster cells. Reagents demonstrating positive surface immunofluorescence and protein A radioimmunoassay reactions against SV40-transformed cells were capable of blocking the surface binding of RaalphaT to SV40-transformed cells in a double-antibody surface antigen radioimmunoassay. This blocking ability demonstrated directly that a component specificity of each surface-reactive reagent is directed against SV40 T-ag. A model is presented which postulates that the differential detection of T-ag by the various serological reagents is a reflection of immunogenic and antigenic differences between T-ag polypeptides localized in nuclei and plasma membranes.
mesh_terms: D000818:Animals; D000951:Antigens, Neoplasm / Q000276:immunology*; D000954:Antigens, Surface / Q000276:immunology; D000956:Antigens, Viral / Q000276:immunology*; D000957:Antigens, Viral, Tumor; D002458:Cell Fractionation; D002462:Cell Membrane / Q000276:immunology; D002467:Cell Nucleus / Q000276:immunology; D002472:Cell Transformation, Viral; D006224:Cricetinae; D000939:Epitopes / Q000276:immunology; D005455:Fluorescent Antibody Technique; D008647:Mesocricetus; D051379:Mice; D008807:Mice, Inbred BALB C; D011233:Precipitin Tests; D011863:Radioimmunoassay; D013539:Simian virus 40 / Q000276:immunology*
chemical_list: D000951:Antigens, Neoplasm; D000954:Antigens, Surface; D000956:Antigens, Viral; D000957:Antigens, Viral, Tumor; D000939:Epitopes