title: Piliation of Lactobacillus rhamnosus GG promotes adhesion, phagocytosis, and cytokine modulation in macrophages.
abstract: Recently, spaCBA-encoded pili on the cell surface of Lactobacillus rhamnosus GG were identified to be key molecules for binding to human intestinal mucus and Caco-2 intestinal epithelial cells. Here, we investigated the role of the SpaCBA pilus of L. rhamnosus GG in the interaction with macrophages in vitro by comparing the wild type with surface mutants. Our results show that SpaCBA pili play a significant role in the capacity for adhesion to macrophages and also promote bacterial uptake by these phagocytic cells. Interestingly, our data suggest that SpaCBA pili also mediate anti-inflammatory effects by induction of interleukin-10 (IL-10) mRNA and reduction of interleukin-6 (IL-6) mRNA in a murine RAW 264.7 macrophage cell line. These pili appear to mediate these effects indirectly by promoting close contact with the macrophages, facilitating the exertion of anti-inflammatory effects by other surface molecules via yet unknown mechanisms. Blockage of complement receptor 3 (CR3), previously identified to be a receptor for streptococcal pili, significantly decreased the uptake of pilus-expressing strains in RAW 264.7 cells, while the expression of IL-10 and IL-6 mRNA by these macrophages was not affected by this blocking. On the other hand, blockage of Toll-like receptor 2 (TLR2) significantly reduced the expression of IL-6 mRNA irrespective of the presence of pili.
authors.affiliation: KU Leuven, Centre of Microbial and Plant Genetics, Heverlee, Belgium University of Antwerp, Department of Bioscience Engineering, Research Group Environmental Ecology and Applied Microbiology, Antwerp, Belgium.
authors.forename: Cynthia E
authors.initials: CE
authors.lastname: Vargas García
authors.affiliation: KU Leuven, Centre of Microbial and Plant Genetics, Heverlee, Belgium University of Antwerp, Department of Bioscience Engineering, Research Group Environmental Ecology and Applied Microbiology, Antwerp, Belgium.
authors.forename: Mariya
authors.initials: M
authors.lastname: Petrova
authors.affiliation: KU Leuven, Centre of Microbial and Plant Genetics, Heverlee, Belgium University of Antwerp, Department of Bioscience Engineering, Research Group Environmental Ecology and Applied Microbiology, Antwerp, Belgium.
authors.forename: Ingmar J J
authors.initials: IJ
authors.lastname: Claes
authors.affiliation: KU Leuven, Centre of Microbial and Plant Genetics, Heverlee, Belgium University of Antwerp, Department of Bioscience Engineering, Research Group Environmental Ecology and Applied Microbiology, Antwerp, Belgium.
authors.forename: Ilke
authors.initials: I
authors.lastname: De Boeck
authors.affiliation: KU Leuven, Centre of Microbial and Plant Genetics, Heverlee, Belgium.
authors.forename: Tine L A
authors.initials: TL
authors.lastname: Verhoeven
authors.affiliation: KU Leuven, Laboratory of Pediatric Immunology, Leuven, Belgium.
authors.forename: Ellen
authors.initials: E
authors.lastname: Dilissen
authors.affiliation: University of Helsinki, Department of Veterinary Biosciences, Helsinki, Finland.
authors.forename: Ingemar
authors.initials: I
authors.lastname: von Ossowski
authors.affiliation: University of Helsinki, Department of Veterinary Biosciences, Helsinki, Finland.
authors.forename: Airi
authors.initials: A
authors.lastname: Palva
authors.affiliation: KU Leuven, Laboratory of Pediatric Immunology, Leuven, Belgium.
authors.forename: Dominique M
authors.initials: DM
authors.lastname: Bullens
authors.affiliation: KU Leuven, Centre of Microbial and Plant Genetics, Heverlee, Belgium.
authors.forename: Jos
authors.initials: J
authors.lastname: Vanderleyden
authors.affiliation: KU Leuven, Centre of Microbial and Plant Genetics, Heverlee, Belgium University of Antwerp, Department of Bioscience Engineering, Research Group Environmental Ecology and Applied Microbiology, Antwerp, Belgium sarah.lebeer@uantwerpen.be.
authors.forename: Sarah
authors.identifier: http://orcid.org/0000-0002-9400-6918
authors.initials: S
authors.lastname: Lebeer
mesh_terms: D000818:Animals; D001422:Bacterial Adhesion; D002460:Cell Line; D016207:Cytokines / Q000378:metabolism*; D010861:Fimbriae, Bacterial / Q000276:immunology*; D007108:Immune Tolerance; D052201:Lacticaseibacillus rhamnosus / Q000276:immunology* / Q000502:physiology; D008264:Macrophages / Q000276:immunology* / Q000382:microbiology*; D051379:Mice; D010587:Phagocytosis
chemical_list: D016207:Cytokines