Influence of adrenal corticosteroids on the susceptibility of cats to feline leukemia virus infection.

The natural resistance of adult specific-pathogen-free cats to feline leukemia virus (FeLV) was abrogated by treatment with various doses of a synthetic corticosteroid, methylprednisolone acetate (MPA), prior to either oral-nasal or i.p. inoculation of FeLV. Persistent viremia was induced in 82% (18 of 22) of MPA-treated cats versus 11% (1 of 9) of age-matched control cats. MPA-treated FeLV-inoculated cats developed prolonged lymphopenia (2 to 8 weeks postinoculation) and a delayed antibody response to the feline oncornavirus-associated cell membrane antigen. The distribution of FeLV group specific antigen in tissues of MPA-treated, FeLV-inoculated cats suggested that corticosteroids enhanced susceptibility to FeLV by impairing early viral containment in the reticuloendothelial and lymphoid tissues.