Lipoproteins Are Responsible for the Pro-Inflammatory Property of Staphylococcus aureus Extracellular Vesicles

Area of Science:

• Microbiology
• Immunology
• Cell Biology

Background:

• Staphylococcus aureus (S. aureus) causes infections; its extracellular vesicles (EVs) role in host interaction is unclear.
• Bacterial EVs are implicated in bacteria-host interactions during infections.
• Understanding S. aureus EV-induced inflammation is critical for infection control.

Purpose of the Study:

• Investigate the role of S. aureus EVs in host inflammatory responses.
• Determine the specific components of S. aureus EVs responsible for immune stimulation.
• Elucidate the mechanisms underlying S. aureus EV-mediated inflammation.

Main Methods:

• Isolated EVs from S. aureus wild-type and mutant strains (Δlgt, ΔsrtAB).
• Assessed immunostimulatory capacities of EVs in vitro and in vivo.
• Utilized monocyte/macrophage cell lines and TLR2-dependent assays.

Main Results:

• S. aureus EVs induced significant pro-inflammatory responses both in vitro and in vivo.
• Immune stimulation was dependent on lipidated lipoproteins (Lpp); Δlgt EVs lacked activity.
• ΔsrtAB EVs showed full immune stimulation, indicating cell wall anchoring is not essential.
• TLR2-dependent pathways and monocytes/macrophages mediated the immune response.
• EV-imbedded Lpp demonstrated potent pro-inflammatory activity.

Conclusions:

• Lipidated lipoproteins (Lpp) within S. aureus EVs are the primary drivers of pro-inflammatory responses.
• The lipidation of lipoproteins, not cell wall anchoring, is essential for S. aureus EV immunostimulatory function.
• S. aureus EVs activate immune cells, particularly monocytes/macrophages, via TLR2-dependent mechanisms.