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Functional basis for complement evasion by staphylococcal superantigen-like 7.

Jovanka Bestebroer1, Piet C Aerts, Suzan H M Rooijakkers

  • 1Department of Medical Microbiology, University Medical Center Utrecht, 3584 CX Utrecht, The Netherlands. j.bestebroer@vumc.nl

Cellular Microbiology
|June 16, 2010
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Summary

Staphylococcal superantigen-like protein 7 (SSL7) inhibits complement C5a generation, protecting against Staphylococcus aureus infection. This immune evasion mechanism impacts bacterial clearance and host defense.

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Area of Science:

  • Immunology
  • Microbiology
  • Biochemistry

Background:

  • Staphylococcus aureus utilizes virulence factors for host colonization.
  • Staphylococcal superantigen-like (SSL) proteins modulate the host innate immune system.
  • SSL7 binds immunoglobulin A (IgA) and complement C5, potentially interfering with immune responses.

Purpose of the Study:

  • To investigate the impact of SSL7 on Staphylococcus aureus-induced complement C5a-mediated effects.
  • To determine SSL7's role in bacterial clearance and immune defense against S. aureus.

Main Methods:

  • Investigated SSL7's effect on C5a generation in staphylococcal opsonization.
  • Utilized an in vitro whole-blood inflammation model to assess SSL7's impact on phagocytosis and oxidative burst.
  • Examined SSL7's effect on complement activation pathways and C5 cleavage.
  • Evaluated SSL7's efficacy in a murine model of immune complex peritonitis.

Main Results:

  • SSL7 inhibits staphylococcal-induced C5a generation, enhanced by its IgA-binding capacity.
  • SSL7 demonstrates protective activity against S. aureus clearance in human whole blood.
  • SSL7 significantly inhibited C5a-induced phagocytosis and oxidative burst.
  • SSL7 affects all three complement activation pathways and inhibits C5 cleavage by C5 convertases.
  • In vivo, SSL7 abrogated C5a-driven neutrophil influx in a murine peritonitis model.

Conclusions:

  • SSL7 is a potent immune modulator that inhibits complement C5a generation and protects against Staphylococcus aureus.
  • SSL7 interferes with complement activation, impacting bacterial clearance and host defense mechanisms.
  • SSL7 represents a potential therapeutic target for managing Staphylococcus aureus infections.