Non-toxic derivatives of LT as potent adjuvants.

The heat-labile enterotoxin of Escherichia coli (LT) consists of an enzymatically active A subunit (LTA) and a pentameric B subunit (LTB). LT has been extensively studied as a potent modulator of immune responses but wild-type LT is toxic and therefore unsuitable for clinical use. Approaches pursued to avoid the toxicity associated with the use of the native toxin while retaining its adjuvant properties have included isolation of subunit B (LTB) and construction of non-toxic LT AB complex mutants, such as LTK63 mutant. Here we review the immunomodulatory characteristics of LTB and LTK63 and their potential as mucosal and parenteral vaccine adjuvants.