title: Neisseria meningitidis can induce pro-inflammatory cytokine production via pathways independent from CD14 and toll-like receptor 4.
abstract: Fulminant meningococcal sepsis (FMS) is considered the prototypical Gram-negative sepsis. Lipopolysaccharide (LPS) is thought to be the main toxic element that induces pro-inflammatory cytokine production after interaction with CD14 and toll-like receptor 4 (TLR4). However, there is increasing evidence that LPS is not the sole toxic element of meningococci. The aim of the present study was to determine the role of CD14 and TLR4 in pro-inflammatory cytokine induction by meningococci. To this end, cytokine induction by isolated meningoccal LPS, wild-type N. meningitidis H44/76 (LPS+-meningococci) matched for concentrations of LPS and LPS-deficient N. meningitidis H44/76lpxA (LPS - -meningococci) was studied in human PBMCs and murine peritoneal macrophages (PMs). Pre-incubation of PBMCs with WT14, a monoclonal antibody against CD14, abolished TNF-alpha and IL-1beta induction by E. coli LPS, while cytokine induction by meningococcal LPS was only partially inhibited. When LPS+- and LPS - -meningococci at higher concentrations were used as stimuli, anti-CD14 had a minimal effect. In C3H/HeJ murine PMs, devoid of a functional TLR4, minimal IL-1alpha, IL-6 and TNF-alpha production was seen after stimulation with 10 ng/mL E. coli or meningococcal LPS. However, at higher concentrations (1000 ng LPS/mL) the production of TNF-alpha, but not IL-1alpha or IL-6, occurred also independently of TLR4. The expression of a functional TLR4 in murine PMs had no effect on the cytokine induction by LPS+- or LPS - -meningococci. It is concluded that pro-inflammatory cytokine induction by N. meningitidis can occur independently of CD14 and TLR4.
authors.affiliation: Department of Internal Medicine, University Medical Centre Nijmegen, the Netherlands.
authors.forename: Tom
authors.initials: T
authors.lastname: Sprong
authors.forename: Peter
authors.initials: P
authors.lastname: van der Ley
authors.forename: Liana
authors.initials: L
authors.lastname: Steeghs
authors.forename: Will J
authors.initials: WJ
authors.lastname: Taw
authors.forename: Trees J W
authors.initials: TJ
authors.lastname: Verver-Janssen
authors.forename: Mihai G
authors.initials: MG
authors.lastname: Netea
authors.forename: Jos W M
authors.initials: JW
authors.lastname: van der Meer
authors.forename: Marcel
authors.initials: M
authors.lastname: van Deuren
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D016207:Cytokines / Q000096:biosynthesis*; D004926:Escherichia coli / Q000472:pathogenicity; D006801:Humans; D066298:In Vitro Techniques; D018836:Inflammation Mediators / Q000378:metabolism*; D007375:Interleukin-1 / Q000096:biosynthesis; D007963:Leukocytes, Mononuclear / Q000187:drug effects / Q000276:immunology; D018950:Lipopolysaccharide Receptors / Q000378:metabolism; D008070:Lipopolysaccharides / Q000633:toxicity; D017737:Macrophages, Peritoneal / Q000187:drug effects / Q000276:immunology; D008562:Membrane Glycoproteins / Q000378:metabolism; D051379:Mice; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D009345:Neisseria meningitidis / Q000472:pathogenicity*; D011956:Receptors, Cell Surface / Q000378:metabolism; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis
chemical_list: D000911:Antibodies, Monoclonal; D016207:Cytokines; D018836:Inflammation Mediators; D007375:Interleukin-1; D018950:Lipopolysaccharide Receptors; D008070:Lipopolysaccharides; D008562:Membrane Glycoproteins; D011956:Receptors, Cell Surface; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; D014409:Tumor Necrosis Factor-alpha