title: Type 1 fimbrial adhesin FimH elicits an immune response that enhances cell adhesion of Escherichia coli.
abstract: Escherichia coli causes about 90% of urinary tract infections (UTI), and more than 95% of all UTI-causing E. coli express type 1 fimbriae. The fimbrial tip-positioned adhesive protein FimH utilizes a shear force-enhanced, so-called catch-bond mechanism of interaction with its receptor, mannose, where the lectin domain of FimH shifts from a low- to a high-affinity conformation upon separation from the anchoring pilin domain. Here, we show that immunization with the lectin domain induces antibodies that exclusively or predominantly recognize only the high-affinity conformation. In the lectin domain, we identified four high-affinity-specific epitopes, all positioned away from the mannose-binding pocket, which are recognized by 20 separate clones of monoclonal antibody. None of the monoclonal or polyclonal antibodies against the lectin domain inhibited the adhesive function. On the contrary, the antibodies enhanced FimH-mediated binding to mannosylated ligands and increased by severalfold bacterial adhesion to urothelial cells. Furthermore, by natural conversion from the high- to the low-affinity state, FimH adhesin was able to shed the antibodies bound to it. When whole fimbriae were used, the antifimbrial immune serum that contained a significant amount of antibodies against the lectin domain of FimH was also able to enhance FimH-mediated binding. Thus, bacterial adhesins (or other surface antigens) with the ability to switch between alternative conformations have the potential to induce a conformation-specific immune response that has a function-enhancing rather than -inhibiting impact on the protein. These observations have implications for the development of adhesin-specific vaccines and may serve as a paradigm for antibody-mediated enhancement of pathogen binding.
authors.affiliation: Department of Microbiology, University of Washington, Seattle, Washington 98195, USA.
authors.forename: Veronika
authors.initials: V
authors.lastname: Tchesnokova
authors.forename: Pavel
authors.initials: P
authors.lastname: Aprikian
authors.forename: Dagmara
authors.initials: D
authors.lastname: Kisiela
authors.forename: Sarah
authors.initials: S
authors.lastname: Gowey
authors.forename: Natalia
authors.initials: N
authors.lastname: Korotkova
authors.forename: Wendy
authors.initials: W
authors.lastname: Thomas
authors.forename: Evgeni
authors.initials: E
authors.lastname: Sokurenko
mesh_terms: D018830:Adhesins, Escherichia coli / Q000737:chemistry / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D000818:Animals; D000907:Antibodies, Bacterial / Q000276:immunology / Q000378:metabolism; D000911:Antibodies, Monoclonal / Q000276:immunology / Q000378:metabolism; D001422:Bacterial Adhesion / Q000502:physiology*; D002460:Cell Line; D004847:Epithelial Cells / Q000382:microbiology*; D004926:Escherichia coli / Q000235:genetics / Q000276:immunology / Q000472:pathogenicity* / Q000502:physiology; D036781:Fimbriae Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D054884:Host-Pathogen Interactions; D006801:Humans; D037601:Mannose-Binding Lectin / Q000378:metabolism; D051379:Mice; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D011817:Rabbits; D001743:Urinary Bladder / Q000166:cytology / Q000382:microbiology*
chemical_list: D018830:Adhesins, Escherichia coli; D000907:Antibodies, Bacterial; D000911:Antibodies, Monoclonal; D037601:Mannose-Binding Lectin; C058769:fimH protein, E coli; D036781:Fimbriae Proteins