Characterization of monoclonal antibodies to heat-labile enterotoxin encoded by a plasmid from a clinical isolate of Escherichia coli

Abstract

Eight selected hybridoma cell lines that produced monoclonal antibodies against heat-labile enterotoxin from an Escherichia coli strain of human origin (LT(h)) were characterized. Antibodies produced by these cell lines were tested for binding specificity in a series of solid-phase radioimmunoassays and Western blots by using as test antigens LT(h), the A, A1, A2, and B polypeptides of LT(h), the heat-labile enterotoxin from an E. coli strain of porcine origin, and cholera toxin. The monoclonal antibodies were also tested for isotype and ability to neutralize LT(h). Two of the anti-LT(h) monoclonal antibodies cross-reacted with cholera toxin, and six were specific for determinants of LT(h) that were not present on cholera toxin. One was specific for a unique epitope of LT(h) that was not shared by the heat-labile enterotoxin from an E. coli strain of porcine origin or cholera toxin. Four antibodies specific for epitopes on the B subunit of LT(h) (LT(h)-B) reacted with pentameric LT(h)-B but did not react in Western blots with monomeric LT(h)-B. The remaining four antibodies were specific for epitopes on LT(h)-A; two of these antibodies bound to A1, one reacted with A2, and one recognized only intact LT(h)-A. Only one monoclonal antibody had detectable neutralizing activity, and it was specific for LT(h)-A.