Role of fimbriae-mediated adherence for neutrophil migration across Escherichia coli-infected epithelial cell layers

This study examined the role of P and type 1 fimbriae for neutrophil migrat ion across Escherichia coil-infected uroepithelial cell layers in vitro and for neutrophil recruitment to the urinary tract in vivo. Recombinant E. co il K-12 strains differing in P or type 1 fimbrial expression were used to i nfect confluent epithelial layers on the underside of transwell inserts. Ne utrophils were added to the upper well, and their passage across the epithe lial cell layers was quantified. Infection with the P- and type l-fimbriate d recombinant E. coil strains stimulated neutrophil migration to the same e xtent as a fully Virulent clinical E. coil isolate, but the isogenic non-fi mbriated vector control strains had no stimulatory effect. The enhancement of neutrophil migration was adhesion dependent; it was inhibited by soluble receptor analogues blocking the binding of P fimbriae to the globoseries o f glycosphingolipids or of type 1 fimbriae to mannosylated glycoprotein rec eptors. P- and type 1-fimbriated E. coil triggered higher interleukin (IL) 8 secretion and expression of functional IL-8 receptors than nonfimbriated controls, and the increase in neutrophil migration across infected cell lay ers was inhibited by anti-IL-8 antibodies. In a mouse infection model, P- o r type l-fimbriated E. coil stimulated higher chemokine (MIP-2) and neutrop hil responses than the non-fimbriated Vector controls. The results demonstr ated that transformation with the pap or firn DNA sequences is sufficient t o convert an E. coil K-12 strain to a host response inducer, and that fimbr iation enhances neutrophil recruitment in vitro and in vivo. Epithelial che mokine production provides a molecular link between the fimbriated bacteria that adhere to epithelial cells and tissue inflammation.