Antibacterial activity of the contact and complement systems is blocked by SIC, a protein secreted by Streptococcus pyogenes.

Research output: Contribution to journalArticle


Recent studies have shown that activation of the complement and contact systems results in the generation of antibacterial peptides. Streptococcus pyogenes, a major bacterial pathogen in humans, exists in more than one hundred different serotypes due to sequence variation in the surface-associated M protein. Cases of invasive and life-threatening S. pyogenes infections are commonly associated with isolates of the M1 serotype, and in contrast to the large majority of M serotypes, M1 isolates all secrete the SIC protein. Here we show that SIC interferes with the activation of the contact system, and blocks the activity of antibacterial peptides generated through complement and contact activation. This effect promotes the growth of S. pyogenes in human plasma, and in a mouse model of S. pyogenes sepsis, SIC enhances bacterial dissemination, results which help to explain the high frequency of severe S. pyogenes infections caused by isolates of the M1 serotype.


Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Dermatology and Venereal Diseases
  • Infectious Medicine
Original languageEnglish
Pages (from-to)1331-1340
JournalJournal of Biological Chemistry
Publication statusPublished - 2011
Publication categoryResearch

Total downloads

No data available