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Quantifying the Cytotoxicity of Staphylococcus aureus Against Human Polymorphonuclear Leukocytes
Published on: January 3, 2020
Staphylococcus aureus metalloprotease aureolysin cleaves complement C3 to mediate immune evasion
Alexander J Laarman1, Maartje Ruyken, Cheryl L Malone
1University Medical Center Utrecht, 3584 CX Utrecht, The Netherlands. a.laarman@umcutrecht.nl
Journal of Immunology (Baltimore, Md. : 1950)
|April 20, 2011
Summary
Staphylococcus aureus metalloprotease aureolysin inhibits the host complement system by cleaving C3, a key immune protein. This evasion mechanism dampens neutrophil responses, aiding bacterial survival.
Area of Science:
- Immunology
- Microbiology
- Biochemistry
Background:
- The complement system is a critical host defense against bacterial infections.
- Staphylococcus aureus employs strategies to evade complement, but the role of its proteases is unclear.
Purpose of the Study:
- To investigate the influence of Staphylococcus aureus proteases on the host complement system.
- To identify and characterize complement inhibitory mechanisms employed by S. aureus.
Main Methods:
- Biochemical assays to analyze complement protein C3 cleavage by aureolysin.
- In vitro experiments using purified C3 and human serum.
- Analysis of bacterial supernatant from S. aureus strains, including an aureolysin mutant.
Main Results:
- Aureolysin identified as a potent inhibitor of complement-mediated phagocytosis and neutrophil killing.
- Aureolysin cleaves complement protein C3, generating C3a and C3b.
- Aureolysin-generated C3b is further degraded by host factors, Factor H and Factor I, in serum.
- Aureolysin is essential for C3 cleavage by S. aureus supernatant.
Conclusions:
- Aureolysin effectively inhibits the complement system by cleaving C3.
- Aureolysin acts synergistically with host complement regulators (Factor H and I) to inactivate C3.
- This mechanism dampens the host immune response, facilitating S. aureus survival.
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