title: CbpA: a novel surface exposed adhesin of Clostridium difficile targeting human collagen.
abstract: Clostridium difficile is the leading cause of antibiotic-associated diarrhoea and pseudomembranous colitis. While the role of toxins in pathogenesis has been extensively described, the contribution of surface determinants to intestinal colonization is still poorly understood. We focused our study on a novel member of the MSCRAMM family, named CbpA (Collagen binding protein A), for its adhesive properties towards collagen. We demonstrate that CbpA, which carries an LPXTG-like cell wall anchoring domain, is expressed on the bacterial surface of C. difficile and that the recombinant protein binds at high affinity to collagens I and V (apparent Kd in the order of 10(-9 ) M). These findings were validated by confocal microscopy studies showing the colocalization of the protein with type I and V collagen fibres produced by human fibroblasts and mouse intestinal tissues. However, the collagen binding activity of the wild-type C. difficile 630 strain was indistinguishable to the cbpA knock-out strain. To overcome this apparent clostridial adherence redundancy, we engineered a Lactococcus lactis strain for the heterologous expression of CbpA. When exposed on the surface of L. lactis, CbpA significantly enhances the ability of the bacterium to interact with collagen and to adhere to ECM-producing cells. The binding activity of L. lactis-CbpA strain was prevented by an antiserum raised against CbpA, demonstrating the specificity of the interaction. These results suggest that CbpA is a newsurface-exposed adhesin contributing to the C. difficile interaction with the host.
authors.affiliation: Novartis Vaccines and Diagnostics Srl, Siena, Italy.
authors.forename: Lorenza
authors.initials: L
authors.lastname: Tulli
authors.forename: Sara
authors.initials: S
authors.lastname: Marchi
authors.forename: Roberto
authors.initials: R
authors.lastname: Petracca
authors.forename: Helen Alexandra
authors.initials: HA
authors.lastname: Shaw
authors.forename: Neil F
authors.initials: NF
authors.lastname: Fairweather
authors.forename: Maria
authors.initials: M
authors.lastname: Scarselli
authors.forename: Marco
authors.initials: M
authors.lastname: Soriani
authors.forename: Rosanna
authors.initials: R
authors.lastname: Leuzzi
mesh_terms: D018829:Adhesins, Bacterial / Q000378:metabolism*; D000818:Animals; D001422:Bacterial Adhesion; D001426:Bacterial Proteins / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D016360:Clostridioides difficile / Q000502:physiology*; D003094:Collagen / Q000378:metabolism*; D005347:Fibroblasts / Q000378:metabolism / Q000382:microbiology; D054884:Host-Pathogen Interactions; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism / Q000382:microbiology; D007700:Kinetics; D013294:Lactococcus lactis / Q000235:genetics / Q000502:physiology; D051379:Mice; D018613:Microscopy, Confocal; D011485:Protein Binding
chemical_list: D018829:Adhesins, Bacterial; D001426:Bacterial Proteins; D002352:Carrier Proteins; C074074:cellulose binding protein A, Clostridium cellulovorans; D003094:Collagen