Collaborative study for the calibration of a replacement International Standard for Diphtheria Antitoxin Equine.

This research focusses on the calibration of a new International Standard for Diphtheria Antitoxin, derived from equine serum. The potency of this new standard was validated through both in-vivo and in-vitro testing, and was subsequently established by a World Health Organisation Committee in 2021.

Research Context and Purpose

• The study is linked with the development of a new International Standard for Diphtheria Antitoxin, which is hepatoglobin obtained from horse serum.
• The article underscores the importance of these standards in maintaining quality control and accuracy when determining the potency of therapeutic diphtheria antitoxin products.
• The main focus of the research is to describe the process of production, characterization and calibration of this new standard.

Methods Used in Research

• The new antitoxin standard was calibrated using both in-vivo (within living organisms) and in-vitro (outside living organisms, in a controlled environment) methods.
• The in-vitro testing was performed using a Vero cell assay, a method that involves exposing Vero cells (normal cells derived from the kidney of an African green monkey) to the antitoxin.
• The potency of this new standard was then compared to the first International Standard, thereby ensuring the continuity of the International Unit, a measure used universally to express the potency of the antitoxin.

Results

• The collaborative study involved 14 laboratories in 9 different countries. The trial outcomes confirmed the potency of the new standard, known as NIBSC product code 18/180.
• It was determined that the new standard had a potency of 57 International Units per ampoule (a small sealed vial used to preserve the potency of substances like the antitoxin).
• Based on the obtained results, the World Health Organisation’s Expert Committee on Biological Standardization approved the new standard in 2021.