Streptococcus pyogenes endopeptidase O contributes to evasion from complement-mediated bacteriolysis via human complement factor C1q

2016 Fiscal Year Final Research Report

• Project/Area Number: 15H06380
• Research Category: Grant-in-Aid for Research Activity Start-up
• Allocation Type: Single-year Grants
• Research Field: Pathobiological dentistry/Dental radiology
• Research Institution: Osaka University
• Principal Investigator: Ogawa Mariko 大阪大学, 歯学研究科, 特任研究員 (20754732)
• Project Period (FY): 2015-08-28 – 2017-03-31
• Keywords: 化膿レンサ球菌 / 補体 / エンドペプチダーゼ / 古典経路 / C1q

Outline of Final Research Achievements

In this study, we identified an endopeptidase of Streptococcus pyogenes, PepO, as an interacting molecule with complement C1q, and investigated its effects on complement immunity and pathogenesis.
ELISA results revealed that PepO bound to C1q in a concentration-dependent manner under physiological conditions. Then, the effects of PepO on bacterial evasion from complement immunity was analyzed in various pH condition. Under low pH conditions, PepO inhibited the binding of IgG to C1q. In addition, pepO deletion rendered S. pyogenes more susceptible to the bacteriocidal activity of human serum. The wild-type strain (WT)-infected tissues exhibited greater severity and lower complement activity as compared to those infected by ΔpepO in a mouse skin infection model.
Our results suggest that interaction of S. pyogenes PepO with C1q interferes with the complement pathway, which enables S. pyogenes to evade complement-mediated bacteriolysis under acidic conditions.

Free Research Field

口腔細菌学