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Soluble M1 protein of Streptococcus pyogenes triggers potent T cell activation

Lisa I Påhlman1, Anders I Olin, Jessica Darenberg

  • 1Department of Clinical Sciences, Section for Clinical and Experimental Infection Medicine, Lund University, Lund, Sweden.

Cellular Microbiology
|September 29, 2007
PubMed

Insights

Streptococcus pyogenes M1 protein acts as a superantigen, driving T cell activation and inflammatory responses. This finding helps explain the severity of invasive streptococcal infections and toxic shock syndrome.

Area of Science:

  • Microbiology
  • Immunology
  • Molecular Biology

Background:

  • Streptococcus pyogenes M1 serotype causes invasive infections and toxic shock syndrome (STSS).
  • Bacterial superantigens are implicated in pathogenesis, but M1 serotype's role is unclear.

Purpose of the Study:

  • To investigate the role of soluble M1 protein from S. pyogenes in T cell activation and cytokine release.
  • To determine if M1 protein functions as a superantigen in severe streptococcal infections.

Main Methods:

  • Purification of soluble M1 protein from S. pyogenes.
  • Assessing T cell proliferation and Th1 cytokine release.
  • Mass spectrometry to confirm protein purity.
  • Investigating HLA class II dependence, MHC restriction, processing requirements, and Vbeta restriction.

Main Results:

  • Soluble M1 protein potently induced T cell proliferation and Th1 cytokine release.
  • M1 protein-evoked T cell activation was HLA class II-dependent but not MHC-restricted.
  • Activation did not require intracellular processing and was Vbeta-restricted.
  • Mass spectrometry confirmed the absence of other detectable proteins.

Conclusions:

  • Soluble M1 protein from S. pyogenes is identified as a novel superantigen.
  • M1 protein likely contributes to excessive T cell activation and hyperinflammation in severe invasive streptococcal infections.

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