[Testing of vaccines. The challenge of testing complex combination vaccines]. / Prüfung von Impfstoffen. Die Herausforderung der Prüfung komplexer Kombinationsimpfstoffe.

Vaccines are biologicals. This group of medicinal products is produced with a predefined variability based on the biological starting materials used. Vaccines are subject to official control authority batch release performed by the Paul-Ehrlich-Institut (PEI). To release batches to the market, experimental testing has to be conducted by an official medicines control laboratory as the PEI. It is the aim of this independent testing to demonstrate the conformity of quality criteria with conditions set in the marketing authorization for each lot produced. The testing is performed on the basis of vaccine specific batch release guideline and due to the difficult and time consuming testing procedures often run in parallel with manufacturers testing. If test results comply with the predefined criteria, the lot in question is released. This article describes the challenge of official control authority batch release testing of two complex combination vaccines.

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 veterinary vaccines is currently performed with the mouse neutralisation test (MNT) to estimate levels of C. perfringens beta- and epsilon-antitoxin levels in the sera of rabbits immunised with the vaccine. Two in vitro methods based on monoclonal antibodies (mAb) have been developed for the determination of specific antibodies against C. perfringens beta-toxin (capture ELISA) and epsilon-toxin (competitive ELISA) in these sera. Both test systems show high specificity and good reproducibility. These ELISA procedures were used in addition to the routine batch potency test in mice (MNT) to determine 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 the rank order determined in vitro. Linear regression analysis gave correlation 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 transferability of the ELISA procedures and the interlaboratory reproducibility of the results. Three coded serum samples were tested several times. The results indicated that both ELISA systems are suitable candidates to replace 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.

The structural polypeptide VP3 of infectious bursal disease virus carries group- and serotype-specific epitopes.

Two independent non-overlapping epitopes could be demonstrated on the structural protein VP3 of infectious bursal disease virus by non-neutralizing monoclonal antibodies produced against serotypes I and II. Both serotypes have one epitope in common, whereas the second epitope is distinct for serotype I and serotype II.

Heterogeneity of the antigenic site responsible for the induction of neutralizing antibodies in infectious bursal disease virus.

Using neutralizing monoclonal antibodies, three categories of escape mutants were selected from a stock of wild-type infectious bursal disease virus (IBDV). Additional mutants were found, where alterations coexisted in two or three of these epitopes. Although each group of mutants had a distinct reaction pattern with neutralizing monoclonal antibodies, all types of mutants were neutralized by convalescent chicken sera to the same extent. In spite of the lack of homogeneity in these antigenic sites located on IBDV structural polypeptide VP2, all neutralizing monoclonal antibodies reacted with epitopes in extracts prepared from the bursa of Fabricius from animals that had died during recent outbreaks of infectious bursal disease in the F.R.G. and Africa. Since binding to VP2 of the escape mutants, demonstrable by immunoprecipitation, correlated with the neutralizing capacity of these antibodies, a combined immunoprecipitation-immunoblotting technique was established as equivalent for a neutralization assay. The results of our experiments indicate that IBDV did not undergo a major antigenic variation in these two areas of Europe and Africa. The significance of protein conformation for the interaction of VP2 with neutralizing antibodies was underlined by the finding that renatured VP2 was capable of binding neutralizing antibodies; the antibodies induced in animals by immunization with this protein, however, were not neutralizing.