Airway proteolytic control of pneumococcal competence

Area of Science:

• Microbiology
• Immunology
• Molecular Biology

Background:

• Streptococcus pneumoniae is an opportunistic pathogen causing severe diseases.
• Neutrophil-derived serine proteases combat invasive pneumococcal infections.
• The role of serine proteases in pneumococcal colonization and genetic exchange is unclear.

Purpose of the Study:

• To investigate if serine proteases degrade the competence stimulating peptide (CSP).
• To determine the impact of CSP degradation on pneumococcal competence and genetic exchange.

Main Methods:

• In vitro digestion of CSP with trypsin-like serine proteases.
• Ex vivo experiments using mouse lung homogenate.
• In vivo recombination frequency measurements after host immune stimulation and viral co-infection.

Main Results:

• Serine proteases degraded CSP at specific cleavage sites, reducing pneumococcal competence dose-dependently.
• Mouse lung homogenate and in vivo experiments confirmed reduced recombination frequencies.
• Host-induced protease production and influenza A virus co-infection significantly lowered pneumococcal recombination.

Conclusions:

• Host serine proteases directly degrade CSP, a key regulator of pneumococcal competence.
• This degradation mechanism reduces bacterial genetic exchange and adaptation.
• Provides a novel insight into host-pathogen interactions controlling pneumococcal behavior.