Poster Presentation 20th Lancefield International Symposium on Streptococci and Streptococcal Diseases 2017

The Group A Streptococcus serotype M2 pilus plays a role in host cell adhesion and immune evasion. (#202)

Catherine Tsai 1 2 , Jacelyn Loh 1 2 , Thomas Proft 1 2
  1. Molecular Medicine and Pathology, University of Auckland, Auckland, New Zealand
  2. Maurice Wilkins Centre, University of Auckland, Auckland, New Zealand

Group A Streptococcus (GAS), or Streptococcus pyogenes, is a human pathogen that causes diseases ranging from skin and soft tissue infections to severe invasive diseases, such as toxic shock syndrome. Each GAS strain carries a particular pilus type encoded in the variable fibronectin-binding, collagen-binding, T antigen (FCT) genomic region, of which 9 types have been identified but only a few have been studied. In this study we describe the functional analysis of the serotype M2 pilus encoded in the FCT-6 region, which shows low sequence homology to other better studied FCT regions. We found that, in contrast to other investigated GAS pili, the ancillary pilin 1 lacks adhesive properties. Instead, the backbone pilin is important for host cell adhesion and binds several host factors, including fibronectin and fibrinogen. Using a panel of recombinant pilus proteins, GAS gene deletion mutants and Lactococcus lactis gain-of-function mutants we show that, unlike other GAS pili, the FCT-6 pilus also contributes to immune evasion. This was demonstrated by a delay in blood clotting, increased intracellular survival of the bacteria in macrophages, higher bacterial survival rates in human whole blood and greater virulence in a Galleria mellonella infection model in the presence of fully assembled FCT-6 pili.