title: A role for TLR4 in Clostridium difficile infection and the recognition of surface layer proteins.
abstract: Clostridium difficile is the etiological agent of antibiotic-associated diarrhoea (AAD) and pseudomembranous colitis in humans. The role of the surface layer proteins (SLPs) in this disease has not yet been fully explored. The aim of this study was to investigate a role for SLPs in the recognition of C. difficile and the subsequent activation of the immune system. Bone marrow derived dendritic cells (DCs) exposed to SLPs were assessed for production of inflammatory cytokines, expression of cell surface markers and their ability to generate T helper (Th) cell responses. DCs isolated from C3H/HeN and C3H/HeJ mice were used in order to examine whether SLPs are recognised by TLR4. The role of TLR4 in infection was examined in TLR4-deficient mice. SLPs induced maturation of DCs characterised by production of IL-12, TNFα and IL-10 and expression of MHC class II, CD40, CD80 and CD86. Furthermore, SLP-activated DCs generated Th cells producing IFNγ and IL-17. SLPs were unable to activate DCs isolated from TLR4-mutant C3H/HeJ mice and failed to induce a subsequent Th cell response. TLR4⁻/⁻ and Myd88⁻/⁻, but not TRIF⁻/⁻ mice were more susceptible than wild-type mice to C. difficile infection. Furthermore, SLPs activated NFκB, but not IRF3, downstream of TLR4. Our results indicate that SLPs isolated from C. difficile can activate innate and adaptive immunity and that these effects are mediated by TLR4, with TLR4 having a functional role in experimental C. difficile infection. This suggests an important role for SLPs in the recognition of C. difficile by the immune system.
authors: Immunomodulation Research Group, School of Biotechnology, Dublin City University, Ireland.
authors: Anthony
authors: A
authors: Ryan
authors: Mark
authors: M
authors: Lynch
authors: Sinead M
authors: SM
authors: Smith
authors: Sylvie
authors: S
authors: Amu
authors: Hendrik J
authors: HJ
authors: Nel
authors: Claire E
authors: CE
authors: McCoy
authors: Jennifer K
authors: JK
authors: Dowling
authors: Eve
authors: E
authors: Draper
authors: Vincent
authors: V
authors: O'Reilly
authors: Ciara
authors: C
authors: McCarthy
authors: Julie
authors: J
authors: O'Brien
authors: Déirdre
authors: D
authors: Ní Eidhin
authors: Mary J
authors: MJ
authors: O'Connell
authors: Brian
authors: B
authors: Keogh
authors: Charles O
authors: CO
authors: Morton
authors: Thomas R
authors: TR
authors: Rogers
authors: Padraic G
authors: PG
authors: Fallon
authors: Luke A
authors: LA
authors: O'Neill
authors: Dermot
authors: D
authors: Kelleher
authors: Christine E
authors: CE
authors: Loscher
mesh_terms: D000818:Animals; D000954:Antigens, Surface / Q000096:biosynthesis; D002478:Cells, Cultured; D016360:Clostridioides difficile / Q000276:immunology*; D003713:Dendritic Cells / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D004761:Enterocolitis, Pseudomembranous / Q000276:immunology / Q000378:metabolism* / Q000382:microbiology; D000949:Histocompatibility Antigens Class II / Q000096:biosynthesis; D007378:Interleukins / Q000096:biosynthesis; D008562:Membrane Glycoproteins / Q000276:immunology*; D051379:Mice; D018345:Mice, Knockout; D015398:Signal Transduction / Q000276:immunology; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000276:immunology / Q000378:metabolism*
chemical_list: D000954:Antigens, Surface; D000949:Histocompatibility Antigens Class II; D007378:Interleukins; D008562:Membrane Glycoproteins; C055764:S-layer proteins; C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4