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Conversion of M serotype 24 of Streptococcus pyogenes to M serotypes 5 and 18: effect on resistance to phagocytosis

H S Courtney1, S Liu, J B Dale

  • 1Department of Veterans Affairs Medical Center and Department of Medicine, University of Tennessee, Memphis 38104, USA. hcourtney@utmem1.utmem.edu

Infection and Immunity
|June 1, 1997
PubMed

Insights

Group A streptococci M5 and M18 proteins resist phagocytosis and adhere to host cells. Fibrinogen is essential for this M protein-mediated resistance.

Area of Science:

  • Microbiology
  • Immunology
  • Molecular Biology

Background:

  • Group A Streptococcus (GAS) is a significant human pathogen.
  • M proteins are key virulence factors of GAS, mediating antiphagocytic and adhesive properties.
  • Understanding M protein function is crucial for developing targeted therapies.

Purpose of the Study:

  • To compare the abilities of M5 and M18 proteins to confer resistance to phagocytosis.
  • To investigate the role of fibrinogen in M protein-mediated resistance.
  • To determine if M proteins mediate adhesion to host cells.

Main Methods:

  • Utilized recombinant GAS strains expressing M5 and M18 proteins.
  • Constructed M- mutants of GAS.
  • Assessed resistance to phagocytosis.
  • Evaluated adhesion to HEp-2 cells in the presence and absence of fibrinogen.

Main Results:

  • M5 and M18 proteins confer resistance to phagocytosis.
  • Fibrinogen is required for M protein-mediated resistance to phagocytosis.
  • M5 and M18 proteins mediate adhesion to HEp-2 cells.

Conclusions:

  • M5 and M18 proteins are important virulence factors for Group A Streptococcus.
  • Fibrinogen plays a critical role in the antiphagocytic function of these M proteins.
  • M proteins contribute to GAS pathogenesis by promoting host cell adhesion.

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