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Evasion of macrophage scavenger receptor A-mediated recognition by pathogenic streptococci

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Author

  • Thomas Areschoug
  • Johan Waldemarsson
  • Siamon Gordon

Summary, in English

PRR recognize conserved structures on pathogenic microbes and are important for the defense against invading microorganisms. However, accumulating evidence indicates that many pathogens have evolved mechanisms to avoid recognition by PRR. One type of PRR is the macrophage scavenger receptor A (SR-A), which has been shown to play an important role in recognition and non-opsonic phagocytosis of pathogenic bacteria. The bacterial ligands for SR-A have been suggested to be LPS or lipoteichoic acid. Here, we use murine bone marrow-derived macrophages to analyze the role of SR-A in non-opsonic phagocytosis of two major Gram-positive pathogens, streptococcus agalactiae (group B streptococcus; GBS) and Streptococcus pyogenes. We show that the polysaccharide capsule of GBS and the surface M protein of S. pyogenes, two important virulence factors, prevent SR-A-mediated non-opsonic phagocytosis of streptococci. The sialic acid moiety of the GBS capsule was crucial for its ability to prevent recognition by SR-A. Moreover, we show that a ligand on GBS recognized by SR-A in the absence of capsule is the surface lipoprotein BIr. These findings represent the first example of a microbial strategy to prevent recognition by SR-A and suggest that bacterial surface proteins may be of importance as ligands for SR-A.

Publishing year

2008

Language

English

Pages

3068-3079

Publication/Series

European Journal of Immunology

Volume

38

Issue

11

Document type

Journal article

Publisher

John Wiley & Sons Inc.

Topic

  • Immunology in the medical area

Keywords

  • Scavenger receptor A
  • Polysaccharide capsule
  • M protein
  • Macrophage
  • streptococcus

Status

Published

ISBN/ISSN/Other

  • ISSN: 1521-4141