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Regulation of protein H expression in M1 serotype isolates of Streptococcus pyogenes
Tara C Smith1, Darren D Sledjeski, Michael D P Boyle
1Department of Microbiology and Immunology Medical College of Ohio, 3055 Arlington Avenue, 43614-5806, Toledo, OH, USA.
Abstract:
Protein H is an immunoglobulin-binding protein expressed by certain M1 serotypes of Streptococcus pyogenes. In a recent study of invasive group A isolates, it was found that none of the 16 M1 serotype isolates analyzed expressed protein H on their surface despite the presence of the protein H gene (sph) in approximately one-third of the isolates. Selection of stable protein H-expressing variants could be achieved by infection of prtH(+) non-expressing strains into a mouse skin and recovering bacteria from the spleen. This effect was independent of the transcription regulator Mga, since a similar effect was noted in an mga(-) mutant. Thus, host passage of S. pyogenes can lead to stable high level expression of Protein H.
Insights
Host passage in mice can induce stable, high-level expression of Protein H in Streptococcus pyogenes. This immunoglobulin-binding protein
Area of Science:
- Microbiology
- Immunology
- Bacterial Pathogenesis
Background:
- Protein H is an immunoglobulin-binding protein expressed by Streptococcus pyogenes M1 serotypes.
- Previous studies indicated that many invasive M1 isolates lack surface Protein H expression despite possessing the protein H gene (sph).
Purpose of the Study:
- To investigate mechanisms that regulate stable Protein H expression in Streptococcus pyogenes.
- To determine if host passage influences Protein H expression.
Main Methods:
- Analyzing invasive Streptococcus pyogenes group A isolates for Protein H expression and the presence of the sph gene.
- Infecting mice with Streptococcus pyogenes strains lacking surface Protein H and recovering bacteria from spleen.
- Evaluating the role of the transcription regulator Mga in Protein H expression.
Main Results:
- None of the 16 analyzed M1 serotype isolates expressed surface Protein H, although approximately one-third carried the sph gene.
- Infection of mice with non-expressing strains led to the selection of stable, high-level Protein H-expressing variants.
- This phenomenon was observed even in mga-negative mutants, indicating Mga independence.
Conclusions:
- Host passage, specifically through mouse infection, can induce stable, high-level surface expression of Protein H in Streptococcus pyogenes.
- This suggests a mechanism for adaptation and enhanced virulence in the host environment.
- The Mga transcription regulator is not essential for this host-induced Protein H expression.