Collaborative study for the establishment of a European Pharmacopoeia Biological Reference Preparation for Clostridia antiserum for serological potency testing of veterinary clostridial vaccines.

This research focuses on the work carried out by the European Directorate for the Quality of Medicines to establish standard reference serum for evaluating the potency of clostridial vaccines used in livestock, as part of an effort to ensure vaccine consistency.

Background and Purpose of the Study

• The European Directorate for the Quality of Medicines (EDQM) organized this study to produce a suitable reference serum for potency testing of clostridial vaccines. Clostridial vaccines are used to prevent diseases caused by bacteria from the Clostridium genus in animals, such as tetanus and botulism.
• The main aim of the study was to ensure the consistency of vaccine production batches using serological potency testing. Serological testing measures the effectiveness of a vaccine by evaluating the body’s immune response to it.
• The study was divided into two parts. The first phase involved producing a blend of sera (plural of serum) representative of the range normally elicited by the vaccines. The second phase involved a larger group of laboratories comparing the activity of the proposed rabbit multicomponent reference serum with the existing standard.

Phase 1: Production of Reference Serum

• In the first phase, various sera, provided by each manufacturer and raised against a wide range of antigens (protein structures that trigger an immune response), were blended together.
• This blended serum was aimed to represent the range of responses that these vaccines normally elicit. However, detailed statistical analysis of the data was not possible due to limited lab participation and assay replication.
• Despite these constraints, enough data was collected to conclude that this blended serum would serve as a suitable reference material for all manufacturers and regulatory authorities.
• The serum was primarily designed to test five components – Clostridium (C.) perfringens beta and epsilon, septicum, novy, and tetani.

Phase 2: Comparison of Reference Serum with Existing Standard

• The second phase of the study saw participation from a larger group of laboratories. These labs were tasked with comparing the activity of the newly created rabbit multicomponent reference serum with the existing equine monovalent World Health Organization standard.
• This comparison was conducted using the toxin neutralisation test in mice, providing a definitive value for the antitoxin activity of the reference preparation for the five components studied.
• The researcher’s long-term aim through this work is to establish this serum as a Biological Reference Preparation for clostridia antiserum. Once established, it would be used to ensure the effectiveness and consistency of future clostridia vaccines.