Division

X1 The blocking or competitive ELISA test shall be carried out according to the following protocol:

The competitive ELISA using monoclonal antibody 3-17-A3 is capable of identifying antibodies to all known serotypes of bluetongue virus (BTV).

The principle of the test is the interruption of the reaction between BTV antigen and a group-specific monoclonal antibody (3-17-A3) by the addition of test serum. Antibodies to BTV present in the test serum block the reactivity of the monoclonal antibody (Mab) and result in a reduction in the expected colour development after the addition of enzyme labelled anti-mouse antibody, and chromogen/ substrate. Sera can be tested at a single dilution of 1:5 (spot test – Appendix 1) or may be titrated (serum titration – Appendix 2) to give dilution end-point. Inhibition values higher than 50 % may be regarded as positive.