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Interaction between complement regulators and Streptococcus pyogenes: binding of C4b-binding protein and factor
David Pérez-Caballero1, Isabel García-Laorden, Guadalupe Cortés
1Departamento de Inmunología, Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas, Madrid, Spain.
Journal of Immunology (Baltimore, Md. : 1950)
|November 24, 2004
Summary
Streptococcus pyogenes M18 strains uniquely bind complement regulators using two distinct proteins: Emm18 for Factor H/FHL-1 and Enn18 for C4BP. This adaptation enhances bacterial survival against human immune defenses.
Area of Science:
- Microbiology
- Immunology
- Molecular Biology
Background:
- Streptococcus pyogenes causes pharyngitis and skin infections.
- Virulence involves bacterial evasion of the host immune system.
- Complement regulatory proteins (Factor H, FHL-1, C4BP) are key targets for bacterial immune evasion.
Purpose of the Study:
- To investigate the mechanism of complement regulator binding by M-type 18 Streptococcus pyogenes.
- To identify the specific bacterial surface proteins responsible for binding Factor H, FHL-1, and C4BP in M18 strains.
Main Methods:
- Utilized isogenic Streptococcus pyogenes strains lacking Emm18 or Enn18 expression.
- Analyzed the binding of complement regulatory proteins to these modified bacterial strains.
Main Results:
- M18 strains bind complement regulators via two distinct surface proteins, unlike other S. pyogenes strains.
- Emm18 protein binds Factor H and FHL-1.
- Enn18 protein binds C4b-binding protein (C4BP).
Conclusions:
- M18 Streptococcus pyogenes employs a unique dual-protein strategy for binding complement regulators.
- This mechanism enhances resistance to opsonization and promotes bacterial survival in the human host.
- S. pyogenes exhibits diverse adaptations to evade immune clearance through complement regulatory protein recruitment.