Immunologic cross-reactions of enterotoxins from escherichia coli and vibrio cholerae

Immunologic similarities among enterotoxins from four serotypes of Escherichia coli and from one strain of Vibrio cholerae, all isolated in India from adults with severe diarrhea, were studied in the ileal-loop model in rabbits. The animals were immunized with preparations of enterotoxin of known biological activity and consisting of dialyzed, lyophilized culture filtrates; antitoxin activity of the immune sera was determined by neutralization of the different enterotoxins. These enterotoxins produced by different serotypes of E. coli were immunologically crossreactive, related to cell-wall antigens, and antigenically related to V. cholerae enterotoxin. Immunization with E. coli enterotoxins, however, failed to protect ileal loops against challenge with enterotoxin, while immunization with V. cholerae enterotoxin conferred protection against homologous challenge, but did not protect against challenge with E. coli enterotoxin. These results indicate the theoretical feasibility of further study of preparations of common antigen as possible vaccines against enterotoxic diarrhea mediated by E. coli.