Use of monoclonal antibody in a blocking ELISA to detect group specific antibodies to bluetongue virus.

An enzyme-linked immunosorbent assay (ELISA) in the form of a blocking test is described for the detection of group specific antibodies to bluetongue virus (BTV). The test relies upon interruption of the reaction between BTV antigen and a group specific murine monoclonal antibody against BTV by addition of serial dilutions of bovine or ovine test sera containing specific antibodies to BTV which inhibit binding of the monoclonal antibody to the BTV antigen. This is detected as a reduction in the optical density (O.D.) reading obtained with the monoclonal antibody alone. The test is capable of specific detection of antibodies to all 22 serotypes of BTV but, unlike the agar gel precipitin (AGP) test, does not show cross-reactions with antibodies to epizootic haemorrhagic disease of deer (EHD) viruses. Furthermore, antibodies to cellular proteins which complicate interpretation of the AGP test and the indirect ELISA are not detected in the blocking ELISA. The high sensitivity and specificity of the blocking ELISA make it an ideal alternative to the AGP test. The use of a monoclonal antibody would facilitate standardisation of diagnostic testing between laboratories.