Detection of antibodies against the core protein p24 of the bovine leukaemia virus in cattle for confirmatory serological testing

An electrophoretic immunoblotting technique which was developed recently wa s evaluated for the identification of serum antibodies against the bovine l eukaemia virus core protein p24 by using 167 sera from a bovine leukaemia v irus-negative herd and 144 sera from herds naturally infected with the viru s. The sensitivity of the immunoblot was 97.4%, relative to sera which were positive in the polymerase chain reaction and in a commercial EBL-ELISA. T he specificity of the immunoblot was 99.4% for the sera from a cattle herd in which all animals were negative by a commercial EBL-ELISA, and it was 96 .7% relative to sera which were negative by the polymerase chain reaction a nd by the agar gel immunodiffusion test from bovine leukaemia virus-infecte d cattle herds. A p24-specific ELISA was developed, using a monoclonal anti -p24 antibody for coating microtitre plates, a crude antigen preparation, a nd a monoclonal anti-bovine IgG-horse radish peroxidase conjugate as compon ents. All reagents were commercially available. While the p24-ELISA worked well with sera from serial bleeds from calves infected experimentally with the bovine leukaemia virus and its sensitivity with sera from the naturally -infected cattle was 96.5%, its specificity was relatively low at 85.0 or 5 3.3%, respectively for the two negative sera groups. (C) 1999 Elsevier Scie nce B.V. All rights reserved.