Case study of development, validation, and acceptance of a non-animal method for assessing veterinary vaccine potency

Abstract

This paper describes the development of an in vitro assay to replace in vivo potency testing for the batch release of inactivated Newcastle Disease virus vaccines. The assay involves the extraction of inactivated antigen from oil emulsion vaccines, the most common adjuvant for poultry vaccines. An enzyme-linked immunosorbent assay (ELISA) is used to quantify the hemagglutinin-neuraminidase (HN) protein of the virus, which was demonstrated to correlate with protection levels.

Validation experiments showed that the method could be used for HN antigen regardless of virus strain or method of inactivation. From the results of these tests it was concluded that this method could replace the in vivo methods that were prescribed in European Pharmacopoeia (Ph. Eur.) Monograph 0870 on inactivated Newcastle Disease vaccines. Large quantities of the necessary reagents and reference materials were prepared and tested. The materials were subjected to stability studies to demonstrate their suitability for long-term storage in order to guarantee long-term availability to the international community. A study in three laboratories demonstrated a good correlation of the candidate assay with two existing in vivo assays, good transferability of the assay, and excellent reproducibility of the proposed assay. A collaborative study was organized by the European Directorate for the Quality of Medicines & Healthcare (EDQM) to demonstrate the repeatability and the reproducibility of the candidate in vitro assay. The suitability of the reference reagent as a Ph. Eur. Biological Reference Preparation was also determined. Fourteen laboratories participated in this study. As a result of these efforts, the assay was included in the relevant Ph. Eur. monograph (01/2007:0870). This paper will address not only the technical aspect of this process but also factors that are considered critical for the success of this project.