OmpA Protein-Deficient Acinetobacter baumannii Outer Membrane Vesicles Trigger Reduced Inflammatory Response

Area of Science:

• Microbiology
• Immunology
• Cell Biology

Background:

• Multidrug-resistant *Acinetobacter baumannii* causes increasing nosocomial infections globally.
• Outer membrane vesicles (OMVs) from *A. baumannii* are implicated in pathogenesis, including virulence factor transfer and inflammation.
• The specific role of OMVs in *A. baumannii*-induced inflammation requires further investigation.

Purpose of the Study:

• To investigate the impact of *Acinetobacter baumannii* OMVs on macrophage activation in vitro.
• To determine the contribution of the OmpA protein to the inflammatory response induced by *A. baumannii* OMVs.

Main Methods:

• Treatment of J774 murine macrophages with *A. baumannii* OMVs.
• Analysis of gene expression for key inflammatory molecules (IL-6, NLRP3, IL-1β).
• Comparison of wild-type OMVs with OMVs from an *A. baumannii* Δ*ompA* mutant.

Main Results:

• *Acinetobacter baumannii* OMVs induce a proinflammatory response and cell death in macrophages and lung epithelial cells.
• The OmpA protein in OMVs significantly contributes to this inflammatory response and cell death.
• Loss of OmpA in OMVs from the Δ*ompA* mutant altered the expression of IL-6, NLRP3, and IL-1β in macrophages.

Conclusions:

• OmpA protein within *A. baumannii* OMVs is a critical factor in triggering intense proinflammatory responses.
• Bacterial OMVs, particularly via OmpA, may prime the cellular environment for infection by inducing inflammation.
• Targeting OmpA in OMVs could be a potential therapeutic strategy against *A. baumannii* infections.