The objective of the current studies was to evaluate whether the potency of a genetically detoxified mucosal adjuvant, derived from heat-labile enterotoxin of Escherichia coli (LTK63), was adversely affected by preexisting immunity. Studies of mice and pigs have involved consecutive intranasal immunization with LTK63 and 2 different vaccines (influenza virus hemagglutinin and a protein-polysaccharide conjugate of Neisseria meningitidis group C). The antibody responses to the vaccines plus LTK63

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... in naive animals were compared with the responses achieved in animals that previously had been immunized with the alternate vaccine plus LTK63. The data showed that the responses of both animal models to intranasal immunization were not adversely affected by the presence of preexisting immunity to the LTK63 adjuvant.