To characterize the function of these surface proteins, we expressed both factors in Escherichia coli K-12 and demonstrated the attachment of Ifp- and InvC-expressing bacteria to human-, mouse-, and pig-derived intestinal epithelial cells.
Ifp also was found to mediate microcolony formation and internalization into polarized human enterocytes.
The ifp and invC genes were not expressed under in vitro conditions but were found to be induced in the Peyer's patches of the mouse intestinal tract.
In a murine coinfection model, the colonization of the Peyer's patches and the mesenteric lymph nodes of mice by the ifp-deficient strain was significantly reduced, and considerably fewer bacteria reached liver and spleen.
The absence of InvC did not have a severe influence on bacterial colonization in the murine infection model, and it resulted in only a slightly reduced number of invC mutants in the Peyer's patches.
The analysis of the host immune response demonstrated that the presence of Ifp and InvC reduced the recruitment of professional phagocytes, especially neutrophils, in the Peyer's patches.
These findings support a role for the adhesins in modulating host-pathogen interactions that are important for immune defense.