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Quantifying the Cytotoxicity of Staphylococcus aureus Against Human Polymorphonuclear Leukocytes
Published on: January 3, 2020
The Staphylococcus aureus protein Sbi acts as a complement inhibitor and forms a tripartite complex with host
Katrin Haupt1, Michael Reuter, Jean van den Elsen
1Department of Infection Biology, Leibniz Institute for Natural Product Research and Infection Biology, Jena, Germany.
Plos Pathogens
|December 30, 2008
Summary
Staphylococcus aureus protein Sbi binds human complement Factor H and C3, forming a complex that inhibits the complement system. This interaction helps the bacteria evade innate immune defenses.
Area of Science:
- Microbiology
- Immunology
- Biochemistry
Background:
- Staphylococcus aureus, a pathogen, binds human complement regulators like Factor H and Factor H-related protein 1.
- Understanding bacterial evasion mechanisms is crucial for combating infections.
Purpose of the Study:
- To identify the Staphylococcus aureus protein that interacts with Factor H.
- To characterize the interaction between Sbi, Factor H, and complement components.
- To investigate the functional consequences of this interaction on complement regulation.
Main Methods:
- Protein-protein interaction studies using surface plasmon resonance.
- Analysis of tripartite complex formation (Sbi, C3b/C3d, Factor H).
- Complement-mediated lysis assays using rabbit erythrocytes.
Main Results:
- The secreted protein Sbi (Staphylococcus aureus binder of IgG) was identified as a novel ligand for Factor H.
- Sbi forms stable tripartite complexes with Factor H and C3b or C3d, with higher stability observed with C3d.
- The Sbi-recruited Factor H retains complement regulatory activity, inhibiting alternative pathway-mediated lysis.
Conclusions:
- Sbi is a multifunctional bacterial protein that binds host complement components (Factor H and C3) and IgG.
- Sbi acts as a potent complement inhibitor by recruiting Factor H and C3b, thereby interfering with innate immune recognition.
- This interaction represents a novel mechanism for bacterial immune evasion.
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