title: Immunosuppressive properties of a virion polypeptide, a 15,000-dalton protein, from feline leukemia virus.
abstract: The 15,000-molecular-weight polypeptide (p15) of feline leukemia virus (FeLV) was shown to impair normal lymphocyte function in vitro and to abrogate immunity to feline oncornavirus disease in vivo. FeLVp15 suppressed concanavalin A-induced blast transformation of normal feline lymphocytes by 68%, while other virion proteins had no effect. p15 suppression was not due to toxicity, nor was p15 a competitive inhibitor of concanavalin A binding. Capping of receptors for concanavalin A on normal feline lymphocytes also was inhibited by either inactivated FeLV or FeLV p15. Groups of cats were immunized with either killed feline oncornavirus-associated cell membrane antigen bearing tumor cells or tumor cells plus FeLV p15. After challenge with feline sarcoma virus, three of four p15-treated cats developed progressive fatal fibrosarcoma as compared to one of five non-p15-treated cats. The cats receiving p15 also had lower cytotoxic antibody titers against feline oncornavirus-associated cell membrane antigen (mean peak titer, 1:6) than did the non-p15 group (1:74). These data support the hypothesis that the immunosuppression in cats infected with FeLV is mediated by FeLV p15.
mesh_terms: D000818:Animals; D000956:Antigens, Viral / Q000008:administration & dosage; D002415:Cats; D003208:Concanavalin A / Q000494:pharmacology; D007109:Immunity; D007152:Immunologic Capping; D007165:Immunosuppression Therapy; D066298:In Vitro Techniques; D005256:Leukemia Virus, Feline / Q000276:immunology*; D007942:Leukemia, Experimental / Q000276:immunology*; D008213:Lymphocyte Activation; D008970:Molecular Weight; D014412:Tumor Virus Infections / Q000276:immunology; D014764:Viral Proteins / Q000008:administration & dosage / Q000276:immunology*
chemical_list: D000956:Antigens, Viral; D014764:Viral Proteins; D003208:Concanavalin A