Circulating levels of feline leukemia and sarcoma viruses and fibrosarcoma regression in persistently viremic cats
de Noronha, F.; Grant, C.K.; Lutz, H.; Keyes, A.; Rowston, W.
Cancer Research 43(4): 1663-1668
1983
ISSN/ISBN: 0008-5472 PMID: 6299527 Document Number: 208907
Eighty specific-pathogen-free kittens 3-4 mo. old received a single s.c. injection of Snyder-Theilen feline sarcoma virus; this isolate contained helper feline leukemia virus (FeLV) at a sarcoma:leukemia ratio of 1:1.5. Recipients developed fibrosarcomas 13-15 days later at the virus injection site; then, for 10 days, the tumors grew rapidly in all animals and reached a mean diameter of 2.7 cm. Tumors subsequently regressed in 45% of the cats and disappeared by 40 days; regressor animals then remained tumor free. Tumors progressed in all other cats, and death occurred 30-90 days of disseminated secondary deposits. Although circulating FeVL was detected in the blood from all cats before or at tumor appearance, Snyder-Theilen feline sarcoma virus was detected only in tumor progessors during the last 2 wk of life. Peak FeLV burdens exceeded 1000 infectious particles and 2.0 .mu.g of protein with a MW of 30,000/ml blood, but no correlation was found betwen tumor progress and leukemia virus load. One-half of the tumor regressor group also eliminated their virus infections. In these animals, virus-neutralizing antibody to both FeLV and Snyder-Theilen feline sarcoma virus was detected at high titer. In remaining regressor cats, the tumors disappeared, but viremia persisted, and no virus-neutralizing antibody activity to either virus was detected. Cytotoxic activity to feline oncornavirus-associated cell membrane antigen was detected in high titer only in sera from the tumor regression and the FeLV-negative group of cats, indicating that fibrosarcoma rejection and virus immunity are mediated by distinct mechanisms.