title: Endosomal recognition of Lactococcus lactis G121 and its RNA by dendritic cells is key to its allergy-protective effects.
abstract: Bacterial cowshed isolates are allergy protective in mice; however, the underlying mechanisms are largely unknown. We examined the ability of Lactococcus lactis G121 to prevent allergic inflammatory reactions.
  
  
  
  We sought to identify the ligands and pattern recognition receptors through which L lactis G121 confers allergy protection.
  
  
  
  L lactis G121-induced cytokine release and surface expression of costimulatory molecules by untreated or inhibitor-treated (bafilomycin and cytochalasin D) human monocyte-derived dendritic cells (moDCs), bone marrow-derived mouse dendritic cells (BMDCs), and moDC/naive CD4+T-cell cocultures were analyzed by using ELISA and flow cytometry. The pathology of ovalbumin-induced acute allergic airway inflammation after adoptive transfer of BMDCs was examined by means of microscopy.
  
  
  
  L lactis G121-treated murine BMDCs and human moDCs released TH1-polarizing cytokines and induced TH1 T cells. Inhibiting phagocytosis and endosomal acidification in BMDCs or moDCs impaired the release of TH1-polarizing cytokines, costimulatory molecule expression, and T-cell activation on L lactis G121 challenge. In vivo allergy protection mediated by L lactis G121 was dependent on endosomal acidification in dendritic cells (DCs). Toll-like receptor (Tlr) 13-/-BMDCs showed a weak response to L lactis G121 and were unresponsive to its RNA. The TH1-polarizing activity of L lactis G121-treated human DCs was blocked by TLR8-specific inhibitors, mediated by L lactis G121 RNA, and synergistically enhanced by activation of nucleotide-binding oligomerization domain-containing protein (NOD) 2.
  
  
  
  Bacterial RNA is the main driver of L lactis G121-mediated protection against experimentally induced allergy and requires both bacterial uptake by DCs and endosomal acidification. In mice L lactis G121 RNA signals through TLR13; however, the most likely intracellular receptor in human subjects is TLR8.
authors.affiliation: Division of Innate Immunity, Research Center Borstel, Airway Research Center North, German Center for Lung Research (DZL), Germany.
authors.forename: Karina
authors.initials: K
authors.lastname: Stein
authors.affiliation: Protectimmun GmbH, Gelsenkirchen, Germany.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Brand
authors.affiliation: Division of Innate Immunity, Research Center Borstel, Airway Research Center North, German Center for Lung Research (DZL), Germany.
authors.forename: André
authors.initials: A
authors.lastname: Jenckel
authors.affiliation: Institute of Medical Microbiology, University of Duisburg-Essen, Essen, Germany.
authors.forename: Anna
authors.initials: A
authors.lastname: Sigmund
authors.affiliation: Department of Molecular Biology, Howard Hughes Medical Institute, UT Southwestern Medical School, Dallas, Tex.
authors.forename: Zhijian James
authors.initials: ZJ
authors.lastname: Chen
authors.affiliation: Institute of Medical Microbiology, University of Duisburg-Essen, Essen, Germany.
authors.forename: Carsten J
authors.initials: CJ
authors.lastname: Kirschning
authors.affiliation: Protectimmun GmbH, Gelsenkirchen, Germany.
authors.forename: Marion
authors.initials: M
authors.lastname: Kauth
authors.affiliation: Division of Innate Immunity, Research Center Borstel, Airway Research Center North, German Center for Lung Research (DZL), Germany. Electronic address: hheine@fz-borstel.de.
authors.forename: Holger
authors.initials: H
authors.lastname: Heine
mesh_terms: D000818:Animals; D000942:Antigens, Bacterial / Q000276:immunology*; D002417:Cattle; D002478:Cells, Cultured; D016207:Cytokines / Q000378:metabolism; D003713:Dendritic Cells / Q000276:immunology*; D004195:Disease Models, Animal; D011992:Endosomes / Q000378:metabolism*; D005260:Female; D006801:Humans; D013294:Lactococcus lactis / Q000276:immunology*; D008168:Lung / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D016269:Milk Hypersensitivity / Q000276:immunology* / Q000517:prevention & control; D053473:Nod2 Signaling Adaptor Protein / Q000378:metabolism; D012329:RNA, Bacterial / Q000276:immunology*; D018417:Th1 Cells / Q000276:immunology; D051200:Toll-Like Receptor 8 / Q000037:antagonists & inhibitors; D051193:Toll-Like Receptors / Q000235:genetics
chemical_list: D000942:Antigens, Bacterial; D016207:Cytokines; C429018:NOD2 protein, human; D053473:Nod2 Signaling Adaptor Protein; D012329:RNA, Bacterial; C495349:TLR8 protein, human; C539093:Tlr13 protein, mouse; D051200:Toll-Like Receptor 8; D051193:Toll-Like Receptors
keywords: Allergy protection; Lactococcus lactis G121; Toll-like receptor 13; Toll-like receptor 8; bacterial RNA; dendritic cells; endosomal acidification; pattern recognition receptor