Immunobiological relationships among new cholera toxins produced by CT gene-negative strains of Vibrio cholerae O1.

The enterotoxic activities of partially purified new cholera toxins (NCT) prepared from the CT gene-negative strains of Vibrio cholerae serotype O1 isolated from cases of diarrhoea in man and from diverse environmental sources were assayed in the rabbit ileal-loop model and the toxin unit was calculated in micrograms of protein content. The secretory activities of one unit of homologous and heterologous enterotoxins were completely neutralised by 2.5 units of crude antiserum raised against one NCT preparation. In immunodiffusion tests, the NCT preparations from all strains tested gave precipitin bands against one antiserum showing reaction of complete identity. Thus, the present study clearly demonstrated that NCTs elaborated by CT gene-negative strains of V. cholerae O1 are immunobiologically similar.