Lymphosarcoma and persistent feline leukemia virus infection of pet cats: a system to study responses during extracorporeal treatments.

Pet cats, persistently infected with feline leukemia virus and having lymphosarcoma, were treated by extracorporeal immunoadsorption using Staphylococcus aureus Cowan I (which has protein A on its surface) to remove immunoglobulin G and circulating immune complexes. Complete viral clearance and long-lasting tumor regression were achieved following such treatments in 9 of 16 cats. In addition, in vitro immunologic assays have been developed that are useful in the clinical evaluation of cats during treatment.