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Protein H, an antiphagocytic surface protein in Streptococcus pyogenes
B M Kihlberg1, M Collin, A Olsén
1Section for Molecular Pathogenesis, Department of Cell and Molecular Biology, Lund University, Lund, Sweden. Britt-Marie.Kihlberg@cmb.umu.se
Infection and Immunity
|March 20, 1999
Summary
Streptococcus pyogenes M protein and M-like protein H are crucial for resisting phagocytosis. Either protein alone is sufficient for survival in blood, but lacking both leads to rapid bacterial killing.
Area of Science:
- Microbiology
- Immunology
- Molecular Biology
Background:
- Surface-associated M protein is a key virulence factor in Streptococcus pyogenes, mediating resistance to phagocytosis.
- Many S. pyogenes strains express M-like proteins structurally similar to M protein, potentially contributing to virulence.
Purpose of the Study:
- To investigate the roles of the M1 protein and protein H in Streptococcus pyogenes virulence.
- To determine the contribution of these proteins to bacterial survival in human blood and resistance to phagocytosis.
Main Methods:
- Generation of Streptococcus pyogenes M1 serotype mutants lacking M1 protein, protein H, or both surface proteins.
- Assessment of bacterial survival in human blood.
- Analysis of protein-binding properties, including immunoglobulin G and complement regulatory proteins.
Main Results:
- Mutants lacking both M1 protein and protein H were rapidly killed in human blood.
- Expression of either M1 protein or protein H alone was sufficient for bacterial survival.
- Bacterial binding of immunoglobulin G and complement regulatory proteins (factor H or factor H-like protein 1) correlated with antiphagocytic properties.
Conclusions:
- Both M1 protein and protein H contribute to the antiphagocytic properties of Streptococcus pyogenes.
- The binding of host immune factors, such as immunoglobulin G and factor H, by these surface proteins is critical for bacterial survival against phagocytosis.