Virus isolation test for feline leukemia virus

A method was developed for detecting feline leukemia virus (FeLV) infection in cats by coculturing separated blood lymphocytes and platelets with clone 81 cells carrying a murine sarcoma genome but free of leukemia virus (S+L-). FeLV caused cell transformation that was easily visible 3-12 days after infection. This method is simple, sensitive, and easily read; it has the advantage of directly detecting infectious FeLV rather than viral antigens.