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The Group A Streptococcus serotype M2 pilus plays a role in host cell adhesion and immune evasion

Jia-Yun C Tsai1,2, Jacelyn M S Loh1,2, Fiona Clow1

  • 1Department of Molecular Medicine & Pathology, School of Medical Sciences.

Molecular Microbiology
|October 15, 2016
PubMed

Insights

Group A Streptococcus M2 pili, distinct from others, aid bacterial adhesion and immune evasion. This unique FCT-6 pilus enhances survival in host environments and infection models.

Area of Science:

  • Microbiology
  • Immunology
  • Molecular Biology

Background:

  • Group A Streptococcus (GAS) causes diverse infections, with pilus types encoded in the FCT region influencing virulence.
  • Specific GAS strains possess unique pilus structures crucial for their pathogenic mechanisms.

Purpose of the Study:

  • To functionally analyze the serotype M2 pilus encoded by the FCT-6 genomic region in GAS.
  • To investigate the adhesive properties and role in immune evasion of the FCT-6 pilus.

Main Methods:

  • Functional analysis of pilin components, including ancillary pilin 1 and backbone pilin.
  • Utilized recombinant pilus proteins, GAS gene deletion mutants, and Lactococcus lactis gain-of-function mutants.
  • Assessed bacterial interactions with host cells, blood clotting, intracellular survival in macrophages, and survival in human whole blood.

Main Results:

  • The ancillary pilin 1 of the FCT-6 pilus lacks adhesive properties.
  • The backbone pilin mediates host cell adhesion and binds fibronectin and fibrinogen.
  • The FCT-6 pilus contributes to immune evasion, evidenced by delayed blood clotting and enhanced bacterial survival in host immune environments.
  • Fully assembled FCT-6 pili increased virulence in a Galleria mellonella infection model.

Conclusions:

  • The FCT-6 pilus of GAS serotype M2 exhibits unique characteristics, differing from other GAS pili in its functional roles.
  • This pilus is crucial for both host cell adhesion and significant immune evasion mechanisms.
  • The FCT-6 pilus represents a novel target for understanding and potentially combating GAS pathogenesis.

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