Naturally Produced Outer Membrane Vesicles fromPseudomonas aeruginosaElicit a Potent Innate Immune Response via Combined Sensing of Both Lipopolysaccharide and Protein Components

Abstract

Pseudomonas aeruginosa is a prevalent opportunistic human pathogen that, like other Gram-negative pathogens, secretes outer membrane vesicles. Vesicles are complex entities composed of a subset of envelope lipid and protein components that have been observed to interact with and be internalized by host cells. This study characterized the inflammatory responses to naturally produced P. aeruginosa vesicles and determined the contribution of vesicle Toll-like receptor (TLR) ligands and vesicle proteins to that response. Analysis of macrophage responses to purified vesicles by real-time PCR and enzyme-linked immunosorbent assay identified proinflammatory cytokines upregulated by vesicles. Intact vesicles were shown to elicit a profoundly greater inflammatory response than the response to purified lipopolysaccharide (LPS). Both TLR ligands LPS and flagellin contributed to specific vesicle cytokine responses, whereas the CpG DNA content of vesicles did not. Neutralization of LPS sensing demonstrated that macrophage responses to the protein composition of vesicles required the adjuvantlike activity of LPS to elicit strain specific responses. Protease treatment to remove proteins from the vesicle surface resulted in decreased interleukin-6 and tumor necrosis factor alpha production, indicating that the production of these specific cytokines may be linked to macrophage recognition of vesicle proteins. Confocal microscopy of vesicle uptake by macrophages revealed that vesicle LPS allows for binding to macrophage surfaces, whereas vesicle protein content is required for internalization. These data demonstrate that macrophage sensing of both LPS and protein components of outer membrane vesicles combine to produce a bacterial strain-specific response that is distinct from those triggered by individual, purified vesicle components.The innate immune response to Gram-negative bacteria is dominated by recognition of lipopolysaccharide (LPS). LPS is sensed by the Toll-like receptor 4 (TLR4) complex, and numerous studies have focused on both how LPS sensitivity drives effective inflammatory responses, leading to the clearance of infection, as well as how uncontrolled TLR4 signaling can lead to LPS toxicity and play a role in septic shock (20,39,48

Vibrio cholerae O395 Outer Membrane Vesicles Modulate Intestinal Epithelial Cells in a NOD1 Protein-dependent Manner and Induce Dendritic Cell-mediated Th2/Th17 Cell Responses

“…OMVs are associated with a mixture of different PAMPs such as LPS and peptidoglycan, and these have been shown to elicit the host immune response to pathogenic bacteria (15,25). The expression of TLR4 and TLR2 is restricted in the intestinal epithelial cells (26), and recent evidence suggests that peptidoglycan is sensed by intracellularly localized nod-like receptor family proteins.…”

Silver-loaded nanotubular structures enhanced bactericidal efficiency of antibiotics with synergistic effect in vitro and in vivo

“…5,6 The treatment of gram-negative bacteria is challenging due to the exterior protective lipopolysaccharide membrane. 7 Drugresistant bacteria is an increasing public health issue that has led to millions of deaths every year because of the shortage of effective therapeutics to combat the resistant bacteria. The rising trend in drug resistance can be partially attributed to the long-term use of antibiotics, promoting the formation of new resistant bacteria through the process of evolutionary pressure.…”

Towards a non-living vaccine against Shigella flexneri: From the inactivation procedure to protection studies

“…Thus, contain significant immunogens and appear to be safe when used as vaccines [24]. Currently, an OMV-vaccine is being successfully used against serogroup B meningococcal disease [25;26] and it also represents a promising vaccine candidate for several other pathogens like Pseudomonas [27], Vibrio [28], Salmonella [29] or Acinetobacter baumannii [30].…”