Antigen quantification as in vitro alternative for potency testing of inactivated viral poultry vaccines

Routine batch control of licensed inactivated viral vaccines for poultry us ually includes a potency assay as a measure of vaccine efficacy. Potency as says often consist of vaccination-challenge experiments in the target speci es or in laboratory animals. Instead of measuring the protection of vaccina ted animals against virulent pathogens, the serological response after vacc ination can be quantified for some vaccines. In vitro antigen quantificatio n assays would be attractive alternatives for the current potency assays be cause the time and costs involved could be greatly reduced and animal use c ould be avoided. Such ill vitro assays will only be acceptable when the cor relation between results and efficacy or potency has been demonstrated conv incingly. The results of our studies on antigen quantification assays indicate that, in principle, quantification of viral antigens from inactivated oil-adjuvan ted vaccines is feasible and reproducible using specially developed antigen capture ELISAs in combination with specific software for statistical analy sis of the ELISA data. We have developed methods to quantify the haemagglut ination-neuraminidase (HN) and fusion (F) proteins of Newcastle disease vir us (NDV), the viral protein 3 (VP3) of the infectious bursal disease virus (IBDV), and the spike-1 (S1) protein of the infectious bronchitis virus (IB V), Vaccination experiments with inactivated ND vaccines indicate that the in vitro quantified HN- or F-proteins of NDV are reliable indicators of the serological response after vaccination.