In vitro detection of antibody to cholera enterotoxin in cholera patients and laboratory animals.

Two new in vitro microtests for anticholeragen (cholera exo-enterotoxin) antibodies are described and compared. In both tests, choleragen and choleragenoid, antigenically identical purified moieties which differ in size, charge, and toxicity, may be used as sensitizing antigens with apparently equal facility. The passive hemagglutination (PHA) test in which sensitized tanned chicken erythrocytes are used was found to be more sensitive than the sensitized bentonite flocculation test. Tests with sera from cholera patients almost invariably demonstrated a rise in titer on convalescence. Results with the PHA test were directly correlated with results derived from in vivo toxin neutralization assays involving inhibition of skin reactivity and the ileal loop reaction. These observations strengthen the hypothesis that choleragen is involved in the pathogenesis of cholera in man and support the unitarian concept that skin reactivity and choleragenesis are manifestations of the same toxin acting in different tissues. Both of the tests described have been modified and used as inhibition tests in the detection and assay of choleragen antigen.