Control of Clostridium perfringens vaccines using an indirect competitive ELISA for the epsilon toxin component - examination of the assay by a collaborative study.

Investigations on the replacement of the mouse neutralisation test for proving vaccine batches of Clostridium (C.) perfringens toxoid vaccines were performed since several years. The European Pharmacopoeia (Ph. Eur.) monograph Clostridium perfringens vaccines for veterinary use (0363) is prescribing a potency test by immunisation of rabbits and checking the induction of specific antibodies against the toxins in a mouse neutralisation test. Since the monograph was revised, immunochemical methods are favoured to detect directly specific antibodies in the rabbit sera. An indirect competitive ELISA using a monoclonal antibody was established at the Paul-Ehrlich-Institut for the detection of antibodies against the epsilon toxin component of C. perfringens. It was revised using the Clostridia rabbit antiserum Ph. Eur. Biological Reference Preparation (BRP) Batch 1 as reference serum. With a defined content of 11 International Units (IU) of C. perfringens epsilon antitoxin this reference serum enables the calculation of the potency of rabbit sera under test. For the collaborative study vaccine products of different composition licensed for the German and European markets were used. Seven international laboratories were included. Aim was to make a prediction on the transferability and precision of the test method. The results showing a satisfactory intermediate precision and transferability of the test confirmed the applicability of the ELISA method for the batch control of C. perfringens vaccines. Therefore a replacement of the mouse neutralisation test is available.