Adjuvant Activity of a Nontoxic Mutant of Escherichia coli Heat-Labile Enterotoxin on Systemic and Mucosal Immune Responses Elicited against a Heterologous Antigen Carried by a Live Salmonella enterica Serovar Typhimurium Vaccine Strain

Systemic and mucosal antibody responses against both the major subunit of colonization factor antigen I (CFA/I) of enterotoxigenic Escherichia coli (ETEC) and the somatic lipopolysaccharide expressed by recombinant bivalent Salmonella vaccine strains were significantly enhanced by coadministration of a detoxified derivative with preserved adjuvant effects of the ETEC heat-labile toxin, LT((R192G)). The results further support the adjuvant effects of LT((R192G)) and represent a simple alternative to improve responses against passenger antigens expressed by orally delivered Salmonella vaccine strains.