Neisseria meningitidis type C capsular polysaccharide inhibits lipooligosaccharide-induced cell activation by binding to CD14

Cell Microbiol. 2007 May;9(5):1297-310. doi: 10.1111/j.1462-5822.2006.00872.x. Epub 2007 Jan 22.


Encapsulated Neisseria meningitidis can invade mucosal barriers and cause systemic diseases. Activation of the innate immune system by conserved meningococcal molecules such as lipooligosaccharides (LOS) is essential for the generation of an effective host immune response. Here we show that the type C capsular polysaccharide of N. meningitidis (MCPS) inhibited LOS-induced interleukin-6 and TNF-alpha secretion from monocytes, and blocked the maturation of dendritic cells induced by LOS, while the capsular polysaccharide from group B streptococcus type III and t(4-hydroxy-3-nitrophenyl) acetyl (NP)-Ficoll had no such effect. MCPS also inhibited the LOS-induced NF-kappaB activation and phosphorylation of signalling molecules such as ERK1/2, p38 and Jun N-terminal kinase. In a direct binding assay, MCPS manifested a concentration-dependent binding to recombinant lipoprotein binding protein and CD14, the two members of the LOS receptor complex. In addition, the binding of LOS to CD14 and lipopolysaccharide binding protein was inhibited by MCPS. We established that MCPS binding to CD14 is responsible for the inhibition of LOS-mediated cell activation because MCPS inhibition of LOS was reversed when access amounts of CD14 were added to culture media of HEK293 cells expressing TLR4 and MD-2, and the magnitude of recovery in LOS stimulation correlated with the increase in CD14 concentration. These results suggest a new virulence property of meningococcal capsular polysaccharides.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Acute-Phase Proteins / metabolism
  • Animals
  • Bacterial Capsules / chemistry
  • Carrier Proteins / metabolism
  • Cell Line
  • Cells, Cultured
  • Dendritic Cells / drug effects
  • Dendritic Cells / immunology
  • Dendritic Cells / metabolism
  • Humans
  • Interleukin-6 / metabolism
  • Interleukin-8 / metabolism
  • Lipopolysaccharide Receptors / metabolism*
  • Lipopolysaccharides / immunology
  • Lipopolysaccharides / metabolism
  • Lipopolysaccharides / pharmacology*
  • Lymphocyte Antigen 96 / metabolism
  • Membrane Glycoproteins / metabolism
  • Mice
  • Mice, Inbred BALB C
  • Monocytes / cytology
  • Monocytes / drug effects
  • Monocytes / metabolism
  • NF-kappa B / metabolism
  • Neisseria meningitidis / growth & development
  • Neisseria meningitidis / immunology
  • Neisseria meningitidis / metabolism*
  • Polysaccharides, Bacterial / immunology
  • Polysaccharides, Bacterial / metabolism
  • Polysaccharides, Bacterial / pharmacology*
  • Protein Binding
  • Signal Transduction / drug effects
  • Tumor Necrosis Factor-alpha / metabolism


  • Acute-Phase Proteins
  • Carrier Proteins
  • Interleukin-6
  • Interleukin-8
  • LY96 protein, human
  • Lipopolysaccharide Receptors
  • Lipopolysaccharides
  • Lymphocyte Antigen 96
  • Membrane Glycoproteins
  • NF-kappa B
  • Polysaccharides, Bacterial
  • Tumor Necrosis Factor-alpha
  • lipopolysaccharide-binding protein