title: Neisseria meningitidis capsular polysaccharides induce inflammatory responses via TLR2 and TLR4-MD-2.
abstract: CPS are major virulence factors in infections caused by Neisseria meningitidis and form the basis for meningococcal serogroup designation and protective meningococcal vaccines. CPS polymers are anchored in the meningococcal outer membrane through a 1,2-diacylglycerol moiety, but the innate immunostimulatory activity of CPS is largely unexplored. Well-established human and murine macrophage cell lines and HEK/TLR stably transfected cells were stimulated with CPS, purified from an endotoxin-deficient meningococcal serogroup B NMB-lpxA mutant. CPS induced inflammatory responses via TLR2- and TLR4-MD-2. Meningococcal CPS induced a dose-dependent release of cytokines (TNF-α, IL-6, IL-8, and CXCL10) and NO from human and murine macrophages, respectively. CPS induced IL-8 release from HEK cells stably transfected with TLR2/6, TLR2, TLR2/CD14, and TLR4/MD-2/CD14 but not HEK cells alone. mAb to TLR2 but not an isotype control antibody blocked CPS-induced IL-8 release from HEK-TLR2/6-transfected cells. A significant reduction in TNF-α and IL-8 release was seen when THP-1- and HEK-TLR4/MD-2-CD14- but not HEK-TLR2- or HEK-TLR2/6-transfected cells were stimulated with CPS in the presence of Eritoran (E5564), a lipid A antagonist that binds to MD-2, and a similar reduction in NO and TNF-α release was also seen in RAW 264.7 cells in the presence of Eritoran. CD14 and LBP enhanced CPS bioactivity, and NF-κB was, as anticipated, the major signaling pathway. Thus, these data suggest that innate immune recognition of meningococcal CPS by macrophages can occur via TLR2- and TLR4-MD-2 pathways.
authors.affiliation: Division of Infectious Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia, USA. szughai@emory.edu
authors.forename: Susu M
authors.initials: SM
authors.lastname: Zughaier
mesh_terms: D000209:Acute-Phase Proteins / Q000378:metabolism; D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D000818:Animals; D019138:Antibodies, Blocking / Q000494:pharmacology; D016667:Bacterial Capsules / Q000276:immunology*; D002352:Carrier Proteins / Q000378:metabolism; D002460:Cell Line; D006801:Humans; D007249:Inflammation / Q000276:immunology*; D016209:Interleukin-8 / Q000378:metabolism; D018950:Lipopolysaccharide Receptors / Q000378:metabolism; D051218:Lymphocyte Antigen 96 / Q000276:immunology*; D008262:Macrophage Activation / Q000187:drug effects; D008264:Macrophages / Q000187:drug effects / Q000276:immunology / Q000382:microbiology; D008562:Membrane Glycoproteins / Q000378:metabolism; D051379:Mice; D009345:Neisseria meningitidis / Q000187:drug effects / Q000276:immunology*; D017472:Receptors, Interleukin-1 / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D051195:Toll-Like Receptor 2 / Q000276:immunology*; D051197:Toll-Like Receptor 4 / Q000276:immunology*; D000099231:Lipopolysaccharide-Binding Protein
chemical_list: D000209:Acute-Phase Proteins; D048868:Adaptor Proteins, Signal Transducing; D019138:Antibodies, Blocking; D002352:Carrier Proteins; D016209:Interleukin-8; D018950:Lipopolysaccharide Receptors; D051218:Lymphocyte Antigen 96; D008562:Membrane Glycoproteins; D017472:Receptors, Interleukin-1; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D000099231:Lipopolysaccharide-Binding Protein; C480228:TICAM2 protein, human; C434984:TIRAP protein, human