Genetic Inactivation of the Extracellular Cysteine Protease Enhances in Vitro Internalization of Group A Streptococci by Human Epithelial and Endothelial Cells

Microb Pathog. 1998 Jun;24(6):333-9. doi: 10.1006/mpat.1998.0204.


Group A Streptococcus (GAS) produces an extracellular cysteine protease (streptococcal pyrogenic exotoxin B) that participates in virulence. We examined two pairs of isogenic GAS strains (serotype M2 and M3) for ability to be internalized by human umbilical vein endothelial cells and A549 human lung fibroblasts. For both host cell types, the level of internalization by the cysteine protease-negative mutant strains was significantly greater than the wild type parent organisms. The data suggest that expression of the cysteine protease contributes to extracellular survival, an observation consistent with recent results from mouse infection studies (Lukomski et al., Infect immun 1998; 66: 771-6).

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Bacterial Proteins / genetics*
  • Cell Line
  • Endothelium, Vascular / cytology
  • Epithelial Cells / physiology
  • Exotoxins / genetics*
  • Fibroblasts / microbiology
  • Fibroblasts / physiology
  • Genes, Bacterial
  • Humans
  • Lung / cytology
  • Membrane Proteins*
  • Mutation*
  • Phagocytosis*
  • Streptococcus pyogenes / enzymology*
  • Streptococcus pyogenes / pathogenicity


  • Bacterial Proteins
  • Exotoxins
  • Membrane Proteins
  • SpeA protein, Streptococcus pyogenes
  • erythrogenic toxin