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Regulation of Streptococcus pneumoniae distribution by Toll-like receptor 2 in vivo

Hakim Echchannaoui1, Philipp Bachmann, Maryse Letiembre

  • 1Division of Infectious Diseases, Department of Research, University Hospital, Hebelstrasse 20, CH-4031 Basel, Switzerland.

Immunobiology
|September 17, 2005
PubMed

Insights

Toll-like receptor 2 (TLR2) helps reduce bacterial load in Gram-positive infections. While not affecting distribution, TLR2 may enhance bacterial clearance by influencing adherence and uptake in brain plexus epithelial cells.

Area of Science:

  • Immunology
  • Microbiology
  • Neuroscience

Background:

  • Toll-like receptor 2 (TLR2) and MyD88 are crucial for reducing Gram-positive bacterial infections.
  • Their precise antibacterial mechanisms remain largely unknown.
  • Previous studies showed increased pathogen burden in TLR2-/- and MyD88-/- mice.

Purpose of the Study:

  • To investigate the role of TLR2 in the interaction between Streptococcus pneumoniae and phagocytes in the brain.
  • To compare bacterial distribution and localization in wild-type (wt) and TLR2-/- mice during meningitis.

Main Methods:

  • Confocal microscopy was used to visualize green fluorescent protein-transformed encapsulated S. pneumoniae (C5017) in the brains of wt and TLR2-/- mice.
  • Bacterial colony-forming units (CFUs) were quantified.
  • Immunohistochemistry identified specific cell types, including GLT1v+ plexus choroideus epithelial cells, Gr-1+ granulocytes, F4/80+ macrophages, Iba1+ microglia, GFAP+ astrocytes, Meca-31+ endothelial cells, and Neun+ neurons.

Main Results:

  • Bacterial distribution (meninges and ventricles) was similar in both wt and TLR2-/- mice.
  • Bacteria were more abundant in ventricles and associated with TLR2-/- plexus choroideus epithelial cells compared to wt.
  • S. pneumoniae were found in granulocytes but not in macrophages, microglia, astrocytes, endothelial cells, or neurons.

Conclusions:

  • TLR2 does not alter the overall distribution of S. pneumoniae in the brain.
  • TLR2 may play a role in antibacterial defense by modulating bacterial adherence and uptake in plexus epithelia.

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