Evaluation of the adjuvant effect of Escherichia coli heat-la-bile enterotoxin mutant (LTK63) on the systematic immune responses to intranasally co-administered measles virus nucleoprotein. Part I: Antibody responses

ABSTRACT

The adjuvanticity and immunogenicity of the heat-labile enterotoxin (LT) of Escherichia coli and of its non-toxic mutant; LTK63; was evaluated after intranasal administration of CBA mice with recombinant measles virus nucleoprotein (rMVNP) with or without LT or LTK63. Both LT and LTK63 were shown to be highly immunogenic with higher responses observed 4 weeks after the booster immunization. Although the nucleoprotein was immunogenic on its own; mice immunized with the nucleoprotein plus wild type LT produced significantly high antibody responses (p0.03). Mice that received the rMVNP with LTJ63 also generated strong antibody responses to rMVNP. These antibodies were also significantly higher than those of rMVNP alone (p>0.05). Data on IgG antibody isotype profiles showed that IgG 1 and IgG 2a were predominant in mice immunized with rMVNP + LT or LTK63 whereas IgG 1 predominated when rMVNP was given on its own implying that LT and LTK63 induce both Th1 and Th2-type immune responses. These results highlight the great potential of this non-toxic mutant of LT as a safe vaccine adjuvant