Tissue-Culture Assay of Antibodies to Heat-Labile Escherichia coli Enterotoxins

Serums of volunteers challenged orally with either toxigenic or invasive strains of Escherichia coli were analyzed for antibody content by means of an adrenal tumor-cell tissue-culture system and by the standard rabbit ileal-loop method. The tissue-culture assay system depends on the ability of specific antibody to neutralize the morphogenic effects of heat-labile Esch. coli enterotoxins. Six of seven volunteers receiving the toxigenic strains demonstrated fourfold or greater increases in antibody titers to heat-labile Esch. coli enterotoxins by the tissue-culture method, whereas eight of nine receiving the invasive Esch. coli strains did not demonstrate any such increases. These results compared favorably with those obtained by the ileal-loop method. The adrenal cell morphologic assay method can be used in seroepidemiologic and clinical studies designed to assess the importance of heat-labile enterotoxigenic Esch. coli diarrheal disease. (N Engl J Med 291:117–121, 1974). ENTEROTOXIGENIC Escherichia coli are probably the cause of many cases of diarrhea, not only in underdeveloped countries and other parts of the world but in the United States as well.1 2 3 Other strains of Esch. coli that are not enterotoxigenic but possess invasive properties have also been implicated in diarrheal disease.4,5 Two types of Esch. coli enterotoxin have been described, and both may be important in enteric disease of human beings and animals.6 7 8 One toxin is of low molecular weight, is heat stable and effects changes in intestinal secretion that begin rapidly after exposure of small bowel to the toxin9,10;.