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

Joseph Erume and 2Harris Partidos
lDepartment of Veterinary Parasitology and Microbiology, Makerere University Box 7062 Kampala, Uganda.
2Department of Pathology and Infectious diseases, The Royal Veterinary College, London NWl OTU.

ABSTRACT
The adjuvanticity and immunogeniclty of the heat-labile enterotoxin (LT) ofEscherichia coliand of its non-toxic mutant, LTK63, was evaluated after Intranasal administration of CBA mice with recombinant measles virus nucleoprotein (rMVNP) with or without LTor LTK63.Both LTand LTK63were 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 wildtype LTproduced significantly high antibody responses (p<O.Ol). Mice that received the rMVNPwith LTK63also generated strongantibody responses to rMVNP.These antibodies were also significantly higher than those of rMVNPalone (p< 0.05).

No significant differences were observed between groups of mice Immunized intranasally withfMVNP plus LTor LTK63(p> 0.05). Data on IgGantibody isotype profiles showed that IgG 1 and IgG 2a were predominant in mice immunized with rMVNP+ LTor LTK63whereasIgG 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 LTas a safe vaccine adjuvant.