Serological studies in cholera. 3. Serum toxin neutralization--rise in titre in response to infection with Vibrio cholerae, and the level in the "normal" population of East Pakistan.

A method has been evaluated for the titration of antibodies to Vibrio cholerae, based on the ability of sera containing such antibodies to neutralize the inflammatory effect of a factor from V. cholerae cultures on the skin of test animals.Ninefold or greater rises in toxin-neutralization titre were found in 73% of 111 bacteriologically confirmed cholera patients in an endemic area of East Pakistan, and in 2.5% of bacteriologically negative patients. This method compares well with the microtechniques developed for the titration of vibrio-agglutinating and vibriocidal antibodies to V. cholerae.The toxin-neutralization method has the advantage that no titre rise is produced in response to vaccination with the whole-cell vaccine in current use in East Pakistan.Relatively high toxin-neutralization titres were noted among children under 15 years of age without vibriocidal or agglutinating antibodies, and without a history of prior infection with V. cholerae.