Development of an in vitro potency test for tetanus vaccines: an immunoassay based on Hc fragment determination

In the three Rs rule context, we have developed a method to quantify tetanus toxoid by ELISA detection of the specific Hc fragment. This fragment and several anti Hc fragment antibodies have been described as protective in mice models. By developing this assay, we have detected Hc presence in tetanus toxoid. Therefore, this functional in vitro assay could replace in vivo potency assays. We have evaluated the analytical performances of this ELISA in specificity, sensitivity, precision, and linearity tests on different combined vaccine formulations. This in vitro assay has been applied to various multi-component vaccines. Results are expressed in Lf Hc/ml with reference to a purified tetanus toxoid standard expressed in Lf/ml.