Lipoteichoic Acid from Staphylococcus aureus Activates the Complement System via C3 Induction and CD55 Inhibition.

Area of Science:

• Immunology
• Microbiology
• Molecular Biology

Background:

• Staphylococcus aureus inhibits complement activity via toxins.
• The mechanism of complement regulation by lipoteichoic acid (LTA) from S. aureus remains unclear.

Purpose of the Study:

• To elucidate the mechanism by which S. aureus LTA regulates complement components.
• To investigate the role of LTA in C3 and CD55 expression and its in vivo effects.

Main Methods:

• Investigated aLTA effects on C3 and CD55 expression in THP-1 and HepG2 cells.
• Utilized Toll-like receptor 2 (TLR2), IRAK2, IRAK-M, and NF-kB signaling pathways.
• Administered aLTA to mice to assess serum C3, MAC, and hepatic CD55 mRNA levels.

Main Results:

• aLTA increased C3 expression via TLR2, IRAK2, and NF-kB activation.
• aLTA induced C3 production in HepG2 cells and increased serum C3 levels in mice.
• aLTA initially increased CD55 in HepG2 cells and liver but decreased it at later time points, mediated by IRAK-M.

Conclusions:

• S. aureus LTA upregulates complement component C3.
• LTA downregulates CD55, a complement regulatory protein.
• These actions may contribute to S. aureus-associated MAC-mediated liver damage.