Establishment of a candidate equine influenza Florida Clade 2 strain A/eq/Richmond/1/07 horse antiserum as Ph. Eur. Biological Reference Preparation/OIE International Reference Reagent.

This research discusses the establishment of a reference antiserum for Equine Influenza Virus (EIV) Florida Clade 2 strain A/eq/Richmond/1/07, to aid in vaccine development and potency assays for equine influenza. The study confirms the suitability of the reference antiserum for use in efficacy tests and clinical diagnostics, paving the way for improved vaccinations for horses.

Underlying Issue – Equine Influenza Virus

• Equine Influenza (EI), a major respiratory disease in horses, has significant welfare and economic impacts, making vaccination an essential prevention method.
• The continuous evolution of the Equine Influenza Virus necessitates the regular updating of EI vaccines.
• In 2010, the World Organisation for Animal Health recommended the addition of representative EIV strains from both the Florida Clade 1 and Clade 2 sub-lineages to the EI vaccine strain composition.

The Project Objective – Creating A Reference Preparation

• To complement the existing reference panel for EI, a horse antiserum against the representative EIV strain of the Florida Clade 2 (FC2) was needed.
• The European Pharmacopoeia and the World Organisation for Animal Health organized an international collaborative study, managed by the European Directorate for the Quality of Medicines and HealthCare, aimed at evaluating candidate references.
• The intent was to establish a European Pharmacopoeia Biological Reference Preparation (BRP) and an OIE International Standard for subsequent use in immunogenicity, efficacy, and potency assays of EI vaccines.

Outcome of The Study

• The collaborative study established the suitability of the candidate serum through the use of ‘Single Radial Hemolysis’ (SRH) and Hemagglutination Inhibition (HI) tests.
• The candidate was then assigned an SRH titre, indicating its concentration and potency.
• In November 2017 and February 2018, the Ph.Eur Commission and the OIE Biological Standards Commission respectively accepted the candidate serum. It was approved as a Biological Reference Preparation (BRP) for use in trial batch potency assays of EI vaccines, and as an International Standard Serum useful in clinical diagnostic tests.