Evaluation of the flocculation limit technique for quality control of Clostridial vaccines

Abstract

This study was carried out to assess and standardize the ‘Limit of Flocculation’ in vitro test to be used in the quality control of vaccine against enterotoxemy. This study used experimental vaccines against enterotoxemy and toxicoid produced from the epsilon toxin of Clostridium perfringens type D, previously evaluated by serum neutralization in mice and TCP test. The ‘Limit of Flocculation’ technique was performed by mixing variable amounts of antitoxin and a fixed value of toxicoid to each tube. It was proposed, in the first tube to flocculate, that its Fl would be the unit of flocculation of the tested sample. The main results indicated that the lower degree of antitoxin detectable both in rabbit and in sheep serum through the ‘Limit of Flocculation’ technique is equivalent to 10 UI/mL. The TCP and ‘Limit of Flocculation’ correlation ratio was 99.97%. In conclusion, the Limit of Flocculation is suitable to replace in vivo methods for the analysis of epsilon. Nevertheless, the referred technique is less effective to be used for the potency test of vaccines against enterotoxemy in substitution to serum neutralization in mice. Keywords: Clostridiosis, in vitro methods, potency test, epsilon toxicoid analysis.