Escherichia coli heat-labile enterotoxin B subunit is a more potent mucosal adjuvant than its closely related homologue, the B subunit of cholera toxin

Although cholera toxin (Ch) and Escherichia coli heat-labile enterotoxin (Etx) are known to be potent mucosal adjuvants, it remains controversial whether the adjuvanticity of the holotoxins extends to their nontoxic, receptor-binding B subunits, Here, ave halle systematically evaluated the comparative adjuvant properties of highly purified recombinant EtxB and CtxB, EtxB was found to be a more potent adjuvant than CtxB, stimulating responses to hell egg lysozyme when the two were coadministered to mice intranasally, as assessed by enhanced serum and secretory antibody titers as well as by stimulation of lymphocyte proliferation in spleen and draining lymph nodes. These results indicate that, although structurally very similar, EtxB and CtxB have strikingly different immunostimulatory propel ties and should not be considered equivalent as prospective vaccine adjuvants.