Tuf of Streptococcus pneumoniae is a surface displayed human complement regulator binding protein

Area of Science:

• Microbiology
• Immunology
• Biochemistry

Background:

• Streptococcus pneumoniae causes severe diseases like pneumonia and meningitis.
• The bacterium employs virulence factors to evade the human immune system.
• Factor H binding proteins are crucial for pneumococcal complement evasion.

Purpose of the Study:

• To identify novel Factor H binding proteins in Streptococcus pneumoniae.
• To investigate the role of elongation factor Tu (Tuf) as a virulence factor.

Main Methods:

• Identification of Tuf as a Factor H binding protein.
• Characterization of Tuf's interaction with human complement inhibitors (Factor H, FHL-1, CFHR1) and plasminogen.
• Assessing the functional impact of these interactions on complement regulation and plasmin activity.

Main Results:

• Elongation factor Tu (Tuf) was identified as a new Factor H binding protein on Streptococcus pneumoniae.
• Tuf binds Factor H, FHL-1, CFHR1, and plasminogen, retaining their regulatory functions.
• Bound plasminogen remains active, cleaving substrates like fibrinogen and complement proteins C3/C3b.

Conclusions:

• Tuf is a multi-functional virulence factor in Streptococcus pneumoniae.
• Tuf contributes to bacterial survival by facilitating complement evasion.
• Tuf may also aid in extracellular matrix degradation, enhancing pathogen invasion.