An ELISA system for tetanus toxoid potency tests: An alternative to lethal challenge

For a long time, a widely used method for tetanus toxoid (Ttd) potency has been the challenge test, in which animals are immunized and then challenged with tetanus toxin in lethal or non-lethal way. In the context of animal welfare, an alternative is desired because the method causes unsustainable distress to animals.

We aimed to replace the system for describing test results, in which scores are assigned to symptoms exhibited by challenged animals, with scores assigned to antibody ELISA titers in immunized mouse sera. The potency values and confidence intervals calculated by the absorbance score system were equivalent to those calculated by the symptom score system. We also attempted to utilize the raw ELISA absorbance instead of the assigned absorbance score and obtained similar results. ELISA may serve as an alternative to the lethal challenge for Ttd potency tests, not only in Japan but also in other countries in which mouse challenge tests are employed.