Establishment of an equine tetanus antitoxin reference standard for veterinary use in Japan.

The research article describes the process of creating the first National Veterinary Assay Laboratory (NVAL) standard for equine tetanus antitoxin in Japan. In short, researchers manufactured a candidate antitoxin, quality tested it, estimated its potency, and then distributed prepared vials for use as the new standard.

Manufacturing and Quality Testing of Candidate Antitoxin

• The researchers first developed vials of a candidate antitoxin. This is the initial step towards creating a reference standard for equine tetanus antitoxin in veterinary use across the country.
• These vials were subjected to multiple quality tests. They were checked for moisture content, vacuum, color, clarity, and the absence of foreign objects to ensure that the antitoxin developed would be safe and effective for use in animals.
• After these quality control measures, a total of 115 vials of the antitoxin were prepared.

Estimating Antitoxin Potency

• To determine the potency (i.e. the strength or efficacy) of the candidate antitoxin, they carried out parallel line assays, which is a standard method for determining dosages of medical drug substances, at three different laboratories.
• This testing was done alongside the existing antitoxin standard, which served as a reference to compare the candidate’s efficacy with.
• The potency estimates, based on the results from these tests, ranged between 38 to 42 International Units (IU).
• Researchers also found that this antitoxin activity was maintained even two years after manufacture when compared with a fresh vial, indicating its longevity.
• Statistical tests revealed no significant non-linearity or non-parallelism of the regression lines (p > 0.05), indicating a consistent potency.

Statistical Assessment and Potency Calculation

• The researchers performed statistical assessments of inter- and intra-laboratory variability which revealed acceptable coefficients of variation. This indicates that their findings were consistent across different laboratories and multiple trials.
• Based on these results, the potency of the potential standard was calculated to be 40 units of antitoxin activity per 1-mL vial.

Distribution and Use of this New Standard

• After the successful development, quality testing, and potency estimation of the candidate antitoxin, these vials were distributed in September 2015 for general use.
• This marked a significant milestone in veterinary medicine in Japan, as it represented the establishment of the first equine tetanus antitoxin reference standard for veterinary use in the country.