IMMUNOSUPPRESSIVE PROPERTIES OF A VIRION POLYPEPTIDE, A 15,000-DALTON PROTEIN, FROM FELINE LEUKEMIA-VIRUS

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  • 1 January 1979
    • journal article
    • research article
    • Vol. 39  (3) , 950-955
Abstract
The 15,000 MW polypeptide (p15) of feline leukemia virus (FeLV) impaired normal lymphocyte function in vitro and abrogated immunity to feline oncornavirus disease in vivo. FeLV p15 suppressed concanavalin [Con] 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 Con A binding. Capping of receptors for Con A on normal feline lymphocytes was inhibited by inactivated FeLV or FeLV p15. Groups of cats were immunized with killed feline oncornavirus-associated cell membrane antigen-bearing tumor cells or tumor cells plus FeLV p15. After challenge with feline sarcoma virus, 3 of 4 p15-treated cats developed progressive fatal fibrosarcoma as compared to 1 of 5 non-p15-treated cats. The cats receiving p15 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). The immunosuppression in cats infected with FeLV may be mediated by FeLV p15.