PURIFICATION OF THE B-SUBUNIT OLIGOMER OF ESCHERICHIA-COLI HEAT-LABILE ENTEROTOXIN BY HETEROLOGOUS EXPRESSION AND SECRETION IN A MARINE VIBRIO

Heat-labile enterotoxins (Etx) are plasmid-encoded, multimeric protein s produced by certain diarrheagenic strains of Eschenichia coli. The n ontoxic, receptor-binding B subunit (EtxB) of such toxins may be usefu l as a component of vaccines against enterotoxigenic E. coli, or as a carrier for the delivery of heterologous epitopes to the mucosal immun e system. Here we describe a simple method for the purification of Etx B from a marine vibrio harboring a broad-host range controlled express ion vector containing the etxB gene. Induction of EtxB resulted in its specific secretion to the medium, to a concentration of greater than 25 mg/liter of culture. The techniques of ultrafiltration and hydropho bic interaction chromatography were used to purify EtxB to homogeneity from the medium of this organism (with a yield of 60.7%). EtxB-epitop e fusion proteins were also successfully expressed and secreted in thi s marine vibrio, suggesting that this system may be of general use in the preparation of EtxB-based vaccines. (C) 1991 Academic Press,Inc.