Validation of a new ELISA method for in vitro potency testing of hepatitis A vaccines

The goal of the project was to standardise a new in vitro method in replacement of the existing standard method for the determination of hepatitis A virus antigen content in hepatitis A vaccines (HAV) marketed in Europe. This became necessary due to issues with the method used previously, requiring the use of commercial test kits. The selected candidate method, not based on commercial kits, had already been used for many years by an Official Medicines Control Laboratory (OMCL) for routine testing and batch release of HAV. After a pre-qualification phase (Phase 1) that showed the suitability of the commercially available critical ELISA reagents for the determination of antigen content in marketed HAV present on the European market, an international collaborative study (Phase 2) was carried out in order to fully validate the method. Eleven laboratories took part in the collaborative study. They performed assays with the candidate standard method and, in parallel, for comparison purposes, with their own in-house validated methods where these were available. The study demonstrated that the new assay provides a more reliable and reproducible method when compared to the existing standard method. A good correlation of the candidate standard method with the in vivo immunogenicity assay in mice was shown previously for both potent and sub-potent (stressed) vaccines. Thus, the new standard method validated during the collaborative study may be implemented readily by manufacturers and OMCLs for routine batch release but also for in-process control or consistency testing. The new method was approved in October 2012 by Group of Experts 15 of the European Pharmacopoeia (Ph. Eur.) as the standard method for in vitro potency testing of HAV. The relevant texts will be revised accordingly. Critical reagents such as coating reagent and detection antibodies have been adopted by the Ph. Eur. Commission and are available from the EDQM as Ph. Eur. Biological Reference Reagents (BRRs).