Viral interference in feline leukemia-sarcoma complex.

Feline leukemia viruses replicate in feline embryo fibroblast cultures without causing visible effects. The virus-infected cultures acquire a resistance to superinfection with the closely related focus-forming feline leukemia pseudotypes of murine sarcoma virus and the feline sarcoma viruses. This induction of viral interference in tissue cultures with the cell-transforming effects of the challenge viruses can be used as a quantitative in vitro assay for the detection of feline leukemia viruses. Preliminary observations indicate that the interference is virus strain-specific (type-specific) and suggest the existence of distinct differences in viral envelope characteristics demonstrable in the viral interference tests.