A feline leukaemia virus- and sarcoma virus-induced tumour-specific antigen

Abstract

BIOCHEMICAL and immunological methods of distinguishing between normal and malignant cells have had limited success. When studying cellular transformation, it is advantageous to study tumour viruses since they contain a definable quantity of genetic information for viral replication and for cell transformation. Viral gene products, such as viral structural antigens, can be studied in both normal infected and virus-transformed cells. Oncornavinis antigens are found in the cytoplasm and cell membrane of both normal and transformed infected cells1,2. These antigens are glycoproteins of the viral envelope or are internal viral proteins3–5. Non-viral tumour-specific antigens resulting from transformation of the host cell by the causative virus, are found in the tumour cell membrane of some tumours induced experimentally by polyoma6 and SV407 DNA viruses; and in cells transformed by an oncornavirus, the Rous sarcoma virus8,9, but have not yet been found in any oncornavirus-induced leukaemic cell. Lymphosarcoma (LSA) or leukaemia of pet cats is caused by a contagiously spread oncornavirus, the feline leukaemia virus (FeLV)10. Antibody to the feline oncornavirus-associated cell membrane antigen (FOCMA)11,12 is associated with resistance to LSA development in FeLV-infected pet cats13,14 and with regression of feline sarcoma virus (FeSV) experimentally-induced fibrosarcomas15. To determine whether FOCMA is a tumour-specific antigen, we tested normal, LSA and fibrosarcoma cat cells for both FeLV antigens and FOCMA. We report here that FOCMA is a tumour-specific antigen induced by naturally occurring feline leukaemia and sarcoma viruses. Our observation, which was made in a random bred species, the pet cat, may have particular relevance for the diagnosis and therapy of naturally occurring lymphoid tumours of other animals, including man.