Collaborative study for the establishment of a candidate equine influenza subtype 2 American-like strain A/EQ/South Africa/4/03 - horse antiserum biological reference preparation.

In 2004, the Office International des Epizooties (OIE) Expert Surveillance Panel on equine influenza recommended that the American lineage component (H3N8) of equine influenza vaccines (A/eq/Newmarket/1/93-like) be updated to an A/eq/South Africa/4/03-like virus. As a consequence the common European Pharmacopoeia (Ph. Eur.) - OIE reference for equine influenza subtype 2 American-like antiserum had to be complemented by an antiserum raised in horses against an A/eq/South Africa/4/03 strain. An international collaborative study run by the European Directorate for the Quality of Medicines (EDQM) in the frame of its Biological Standardisation Programme (BSP) under the aegis of the Ph. Eur. and the OIE was organised. The study was aimed at evaluating a candidate reference horse anti-serum using the single radial haemolysis (SRH) and haemagglutination inhibition (HI) tests. The standard was to be established for use in immunogenicity and batch potency assay of equine influenza vaccines as a Ph. Eur. BRP and for use in clinical diagnostic tests as an OIE-approved International Standard. The evaluation performed in the collaborative study enabled the suitability of the candidate to be demonstrated and an SRH value to be assigned. The candidate was adopted as a BRP by the Ph. Eur. Commission and approved by the OIE Biological Standards Commission as an International Standard Serum in June and September 2006, respectively.