Streptococcus pyogenes Endopeptidase O Contributes to Evasion from Complement-mediated Bacteriolysis via Binding to...

Area of Science:

• Microbiology
• Immunology
• Molecular Biology

Background:

• Streptococcus pyogenes uses virulence factors to evade complement-mediated bacteriolysis.
• Understanding molecules interacting with complement C1q, the classical pathway initiator, is crucial for pathogen defense.
• The interaction of S. pyogenes with C1q is not fully understood.

Purpose of the Study:

• Identify S. pyogenes molecules interacting with C1q.
• Investigate the role of PepO in complement immunity and pathogenesis.
• Determine PepO's effect on bacterial evasion under acidic conditions.

Main Methods:

• Enzyme-linked immunosorbent assay (ELISA) and surface plasmon resonance (SPR) to assess PepO-C1q binding.
• Analysis of PepO's effect on complement immunity under low pH conditions.
• Infection studies using a pepO deletion mutant (ΔpepO) in a mouse skin model.

Main Results:

• S. pyogenes recombinant PepO binds to human C1q.
• PepO shows higher affinity for C1q than IgG under low pH, inhibiting IgG-C1q binding.
• ΔpepO mutant S. pyogenes is more susceptible to human serum and causes less severe infections with higher complement activity.

Conclusions:

• S. pyogenes PepO interacts with C1q, interfering with the complement pathway.
• This interaction facilitates bacterial evasion of complement-mediated bacteriolysis in acidic environments.
• PepO is a novel virulence factor contributing to S. pyogenes pathogenesis.