Neutralization of Cholera Enterotoxin-induced Steroidogenesis by Specific Antibody

A clonal line of adrenal cells in tissue culture responds to picogram quantities of cholera enterotoxin by undergoing morphologic changes and increasing its production of ketosteroids. When toxin is preincubated with antisera prepared against the purified enterotoxin or the naturally occurring toxoid, choleragenoid, both morphologic and steroidogenic changes are prevented. Partial, but not complete, neutralization of the effects of several crude preparations of toxigenic Escherichia coli was achieved when these toxin-containing preparations were incubated with antisera to cholera enterotoxin. This tissue culture system is a simple, reliable, relatively inexpensive, and sensitive (capable of detecting < 0.25 unit) assay system for the detection of cholera antitoxin. The results of several recent studies have emphasized the importance of the adenyl cyclaseadenosine-3',5'-monophosphate (cyclic AMP) system in the mediation of the effects of cholera enterotoxin [1-7]. Based on this information, extraintestinal models have been developed to simplify the study of the toxin's effects [1, 8-10]. We have recently described a tissue culture system of adrenal cells that respond to adrenocorticotropic hormone (ACTH), cyclic AMP, and cholera enterotoxin by undergoing morphologic changes and increasing their production and secretion of corticosteroids [11]. This system is simple, reliable, and capable of detecting as few as 5 pg of cholera toxin. Since there is currently a great deal of interest in systems capable of assaying small quantities of antibodies to cholera toxin, we decided to evaluate this tissue culture system for its sensitivity to neutralization of the effects of the toxin by antitoxin-containing sera. The results of these studies suggest that the adrenal cell system will be an effective and sensitive means for assessing the specific antibody content of sera.