Detection of Antibodies Against Bovine Leukemia Virus

A modified syncytium-induction inhibition test which is more sensitive than the immunodiffusion test, was developed using rabbit complement. In this test, fetal lamb kidney cells continuously infected with bovine leukemia virus were used as effector cells, and the CC81 cat cells transformed with murine sarcoma virus, were used as indicator cells. The syncytiuminduction inhibition effect of anti-bovine leukemia virus serum was enhanced significantly by the addition of rabbit complement. The syncytiuminduction inhibition titers had a statistically significant correlation with the immunodiffusion titers and were four to 64 times higher than immunodiffusion titers. In 12 experimentally infected cattle, the syncytiuminduction inhibition test detected the antibodies earlier than the immunodiffusion test and continuously detected them when immunodiffusion antibody changed to negative. In the 81 sera from naturally infected herds, 35 (43.2%) were positivre by the immunodiffusion test and 55 (67.9%) by the syncytiuminduction inhibition test.