Development and prevalidation of two different ELISA systems for the potency testing of Clostridium perfringens beta- and epsilon-toxoid containing veterinary vaccines

The potency testing of Clostridium perfringens mono- and multicomponent vet erinary vaccines is currently performed with the mouse neutralisation test (MNT) to estimate levels of C. perfringens beta- and epsilon-antitoxin leve ls in the sera of rabbits immunised with the vaccine. Two in vitro methods based on monoclonal antibodies (mAb) have been developed for the determinat ion of specific antibodies against C. perfringens beta-toxin (capture ELISA ) and epsilon-toxin (competitive ELISA) in these sera. Both test systems sh ow high specificity and good reproducibility. These ELISA procedures were u sed in addition to the routine batch potency test in mice (MNT) to determin e beta- and epsilon-antitoxin levels in 523 samples of rabbit serum. There was good agreement between the rank order of sera determined in vivo and th e rank order determined in vitro. Linear repression analysis gave correlati on coefficients of 0.88 for the capture ELISA and 0.41 for the competitive ELISA, with a significance level of P < 0.01 in both cases. Furthermore, a prevalidation study was carried out in four laboratories to evaluate the tr ansferability of the ELISA procedures and the interlaboratory reproducibili ty of the results. Three coded serum samples were tested several times. The results indicated that both ELISA systems are suitable candidates to repla ce the MNT used for the potency testing of beta- and epsilon-toxoid in mono - and multicomponent veterinary vaccines. However, these assays still need to be validated in an international collaborative study. (C) 1999 Federatio n of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.