Immunological relationship of the B subunits of Campylobacter jejuni and Escherichia coli heat-labile enterotoxins

Abstract

The application of dissociation techniques, involving gel filtration in the presence of guanidine, to a semipurified preparation of Campylobacter jejuni heat-labile enterotoxin yielded a material whose functional and immunological properties resemble those of the B subunits of cholera toxin and Escherichia coli heat-labile toxin (LT). The C. jejuni toxin B subunit reacted with GM1 ganglioside in an enzyme-linked immunosorbent assay, but lacked the holotoxin's cytotonic activity in the Chinese hamster ovary tissue culture assay and its ability to cause fluid secretion in rat ileal ligated loops. The C. jejuni toxin B subunit showed lines of partial identity with the B subunits of both cholera toxin and LT in gel immunodiffusion; it appeared to be more closely related immunologically to the LT B subunit than to the cholera toxin B subunit in enzyme-linked immunosorbent assays that used antisera either to LT or to its B subunit. Rats immunized with LT B subunit were significantly protected against challenge with either the semipurified C. jejuni toxin or a viable enterotoxigenic strain of C. jejuni, although twice the immunization dosage was required to achieve protection comparable to that against the homologous toxin or viable bacteria. These observations indicate that the C. jejuni enterotoxin contains a B subunit that bears an immunological relationship with the B subunits of cholera toxin and LT.