Recombinant enterotoxins as vaccines against escherichia-coli-mediated diarrhea

A fusion protein, comprising the B subunit of the heat-labile enterotoxin and a portion of the precursor to the heat-stable enterotoxin of Escherichia coli, has been created by recombinant genetic techniques. It is exported successfully to the bacterial periplasm and assembles into pentamers which retain the ability to bind to GM1 ganglioside. Native toxin epitopes are displayed and the molecule can be easily purified from periplasmic extracts of cells expressing the gene fusion. Although the protein carries the natural sequence of the heat-stable enterotoxin, it is greatly attenuated in toxicity. Systemic immunization of mice or oral administration of the fusion elicits antibody responses against both classes of E. coli enterotoxin.