Streptococcal pyrogenic exotoxin B cleaves properdin and inhibits complement-mediated opsonophagocytosis

Nina Tsao, Wan Hua Tsai, Yee Shin Lin, Woei Jer Chuang, Chiou Huey Wang, Chih Feng Kuo

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39 Citations (Scopus)


Streptococcal pyrogenic exotoxin B (SPE B), a cysteine protease, is an important virulence factor in group A streptococcal (GAS) infection. The reduction of phagocytic activity by SPE B may help prevent bacteria from being ingested. In this study, we investigated the mechanism SPE B uses to enable bacteria to resist opsonophagocytosis. Using Western blotting and an affinity column immobilized with SPE B, we found that both SPE B and C192S, an SPE B mutant lacking protease activity, bound to serum properdin, and that SPE B, but not C192S, degraded serum properdin. Further study showed that SPE B-treated, but not C192S-treated, serum blocked the alternative complement pathway. Reconstitution of properdin into SPE B-treated serum unblocked the alternative pathway. GAS opsonized with SPE B-treated serum was more resistant to neutrophil killing than GAS opsonized with C192S-treated or normal serum. These results suggest that a novel SPE B mechanism, one which degrades serum properdin, enables GAS to resist opsonophagocytosis.

Original languageEnglish
Pages (from-to)779-784
Number of pages6
JournalBiochemical and Biophysical Research Communications
Issue number3
Publication statusPublished - 2006 Jan 20

All Science Journal Classification (ASJC) codes

  • Biophysics
  • Biochemistry
  • Molecular Biology
  • Cell Biology


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