ABSTRACT:
A recombinant protein comprising the maltose-binding protein (MBP) of
Escherichia coli
fused to amino acids 5 to 337 of the FlaA flagellin of
Campylobacter coli
VC167 was evaluated for immunogenicity and protective efficacy against challenge by a heterologous strain of campylobacter,
Campylobacter jejuni
81-176, in two murine models. The sequence of the
flaA
gene of strain 81-176 revealed a predicted protein which was 98.1% similar to that of VC167 FlaA over the region expressed in the fusion protein. Mice were immunized intranasally with two doses of 3 to 50 μg of MBP-FlaA, given 8 days apart, with or without 5 μg of the mutant
E. coli
heat-labile enterotoxin (LT
R192G
) as a mucosal adjuvant. The full range of MBP-FlaA doses were effective in eliciting antigen-specific serum immunoglobulin G (IgG) responses, and these responses were enhanced by adjuvant use, except in the highest dosing group. Stimulation of FlaA-specific intestinal secretory IgA (sIgA) responses required immunization with higher doses of MBP-FlaA (≥25 μg) or coadministration of lower doses with the adjuvant. When vaccinated mice were challenged intranasally 26 days after immunization, the best protection was seen in animals given 50 μg of MBP-FlaA plus LT
R192G
. The protective efficacies of this dose against disease symptoms and intestinal colonization were 81.1 and 84%, respectively. When mice which had been immunized with 50 μg of MBP-FlaA plus LT
R192G
intranasally were challenged orally with 8 × 10
10
, 8 × 10
9
, or 8 × 10
8
cells of strain 81-176, the protective efficacies against intestinal colonization at 7 days postinfection were 71.4, 71.4, and 100%, respectively.