The relation of immune response to pathogenesis, vaccination and epidemiology in virus induced leukaemia.

The antigenic systems of oncornaviruses and particularly feline leukaemia virus (FeLV) are reviewed briefly. The use of immunological methods in studying the epidemiology of the disease is described. The incidence of FeLV infection as judged by a serological survey is at least 100 times greater than that of leukaemia in the cat population. Horizontal transmission, due to virus replication in respiratory and alimentary epithelial cells, is common. A method of producing high titres of antibody against membrane antigens of virus infected cells is described; the use of such vaccination is discussed in relation to several epidemiological facets of feline leukaemia virus infection. Leukaemia viruses are well known to cause immunodepression to heterologous antigens. The hypothesis is advanced that depression of the humoral antibody response to leukaemia virus antigens and cell membrane antigens may be an early event allowing establishment and replication of virus in haemic and the lymphatic tissues. Subsequent depression of cell mediated immunity through direct action of thymic cells is known to take place in the cat system. This may allow further spread of the virus with replication in epithelial cells which are not susceptible to cytotoxic action. Thus the primary events leading to leukaemogenesis may be an interplay between immunostimulation and immunodepression.