Collaborative study for the establishment of two European Pharmacopoeia Biological Reference Preparations for serological potency testing of tetanus vaccines for veterinary use.

This study focuses on the creation and verification of two reference sera for checking the potency of tetanus vaccines used in veterinary medicine, in accordance with the standards set by the European Pharmacopoeia.

Objective and Methodology of the Study

• The European Directorate for the Quality of Medicines (EDQM) spearheaded an international study split into two phases. Its main objective was to generate and authenticate two reference sera to examine the potency of tetanus vaccines used in veterinary medicine.
• In the first phase, pools of sera were created by immunising guinea pigs and rabbits with a tetanus toxoid adhering to the immunisation schedule set by the European Pharmacopoeia for this particular potency testing.
• Post immunisation, the resultant materials were aliquoted (divided into smaller portions) and freeze-dried for future use.
• These sera were then characterised using various immunochemical and biological assays, establishing their suitability as reference materials, particularly for in-vitro tests pertaining to Clostridium tetani, the bacterium causing tetanus.

Validation and Calibration of the Reference Sera

• In the second phase of the study, the respective candidate Biological Reference Preparations (BRP) were calibrated using the Toxin Binding Inhibition Test (ToBI).
• This calibration process involved a wide range of laboratories, including those associated with manufacturers and official medicines control laboratories (OMCL).
• The reference sera’s anti-tetanus activity was benchmarked against the already established equine monovalent World Health Organization (WHO) International Standard (IS).
• Thus, the study enabled the researchers to assign a precise value to the antitoxin activity of the reference preparations based on their content of anti-tetanus antibodies, therefore providing a standard for veterinary use.