Pilus adhesin RrgA interacts with complement receptor 3, thereby affecting macrophage function and systemic...

Area of Science:

• Microbiology
• Immunology
• Infectious Diseases

Background:

• Streptococcus pneumoniae causes significant global morbidity and mortality.
• Pneumococcal interactions with host cells drive disease symptoms and inflammation.
• A pilus structure on pneumococci, including the RrgA adhesin, is implicated in spread.

Purpose of the Study:

• Investigate the role of the RrgA adhesin in pneumococcal interactions with macrophages.
• Elucidate the mechanisms by which RrgA influences pneumococcal disease development.
• Identify how pneumococci communicate with immune cells to affect disease progression.

Main Methods:

• Studied pneumococcal-macrophage interactions using murine and human cell lines.
• Utilized recombinant RrgA and RrgC, antibodies to CR3, and CR3-deficient macrophages.
• Employed flow cytometry, in vivo infection models (mice), motility assays, and time-lapse microscopy.

Main Results:

• Pili with RrgA enhanced pneumococcal uptake by macrophages via complement receptor 3 (CR3).
• RrgA, but not RrgC, promoted CR3-mediated phagocytosis and directly bound CR3.
• In vivo, RrgA facilitated pneumococcal spread to the bloodstream, leading to earlier and more severe septicemia.

Conclusions:

• RrgA-mediated engagement with CR3 is crucial for pneumococcal phagocytosis and systemic dissemination.
• This interaction enhances macrophage motility and intracellular survival, promoting disease spread.
• Understanding RrgA-CR3 interactions offers potential targets for novel therapeutic strategies against pneumococcal infections.