COMPARISON OF 4 SEROLOGIC TESTS FOR THE DETECTION OF ANTIBODIES TO BOVINE LEUKEMIA-VIRUS

  • 1 January 1981
    • journal article
    • research article
    • Vol. 42  (1) , 5-8
Abstract
Four tests for detection of antibodies to bovine leukemia virus (BLV), the primary cause of lymphosarcoma in cattle, were compared. The sera that were tested came from cattle in naturally infected commercial dairy herds, cattle that were infected under experimental conditions and cattle in an isolated BLV-free herd. The test that were compared included a radioimmunoprecipitation assay (RIA) with p24 antigen, a RIA with glycoprotein (gp) antigen, an agar-gel immunodiffusion (AGID) test with gp antigen and a virus neutralization (VN) test that was based on inhibition of BLV-induced syncytia in cell culture. Results of the 4 serologic tests agreed for 96.8% of the sera from cattle in commercial herds. The gp RIA detected the greatest number of positive sera (188); it was followed in turn by the p24 RIA (187), the VN test (183) and the AGID test (176). The gp RIA titers of the 12 sera that gave negative AGID results were 175 or less. In RIA, the percentage of precipitation of labeled antigen BLV-positive sera was almost always higher with gp antigen than with p24 antigen. Satisfactory sensitivity in the p24 RIA required the acceptance of a low level of antigen precipitation, 15% as a positive test. In the gp RIA, almost all positive sera precipitated at least 50% of the labeled antigen. Nonspecific precipitation of antigen in the RIA by sera from BLV-free cattle ranged from 4-10%. Examination of sequential serum samples from 17 experimentally infected cattle showed that BLV antibody was 1st detected 2-8 wk after inoculation. In 9 cattle, seroconversion was detected simultaneously by all of the tests. Results from the other 8 cattle indicated that seroconversion could be detected 1st by p24 RIA, followed by the gp RIA and the VN test. The longest interval between RIA seroconversion and AGID seroconversion was 10 days. Monthly tests of sera from 10 laboratory cattle that were infected by contact exposure showed that 7 animals seroconverted in all tests at the same time. Two cattle were positive 1st in RIA but by the next month they were also positive in the VN and AGID tests. One animal was positive in the RIA and the VN test for 2 mo. before antibody was detected by AGID.