Soluble CD163 masks fibronectin-binding protein A-mediated inflammatory activation of Staphylococcus aureus infected...

Area of Science:

• Immunology
• Microbiology
• Cell Biology

Background:

• Staphylococcus aureus uses fibronectin-binding protein A (FnBP-A) and Eap for pathogenesis.
• Soluble CD163 (sCD163) binding to fibronectin enhances bacterial clearance by monocytes.
• The effect of sCD163 on monocyte activation during S. aureus infection was previously unknown.

Purpose of the Study:

• To investigate whether sCD163 influences monocyte activation status during S. aureus infection.
• To identify the specific S. aureus molecule responsible for activating monocyte inflammatory responses.
• To elucidate the mechanisms by which sCD163 modulates the immune response to S. aureus.

Main Methods:

• Utilized genetically modified S. aureus strains lacking FnBP-A or Eap.
• Assessed monocyte activation markers, including cytokine secretion (TNFα, IL-1β, IL-6, IL-8) and DAMP molecule (MRP8/14) release.
• Measured transcription factor NR4A1 expression and chemokine CXCL2 induction.
• Evaluated MAP kinase activation and ROS production in sCD163-treated monocytes.

Main Results:

• Identified FnBP-A, but not Eap, as the activator of monocyte inflammatory response.
• sCD163 binding to S. aureus masked FnBP-A-mediated activation, dampening pro-inflammatory cytokine and DAMP molecule secretion.
• sCD163 limited NR4A1 and CXCL2 induction, thereby inhibiting apoptosis and promoting pathogen clearance.
• sCD163 did not cause general immunosuppression, as MAP kinase activation and ROS production remained unaltered.

Conclusions:

• sCD163 specifically dampens FnBP-A-induced inflammatory activation in monocytes during S. aureus infection.
• This targeted immune modulation by sCD163 facilitates pathogen elimination and supports tissue recovery.
• sCD163 represents a key component in resolving inflammation and promoting host defense against S. aureus.