BACKGROUND: E. coli O83 (Colinfant Newborn) is a Gram-negative (G-) probiotic bacterium used in the clinic. When administered orally, it reduces allergic sensitisation but not allergic asthma. Intranasal administration offers a non-invasive and convenient delivery method. This route bypasses the gastrointestinal tract and provides direct access to the airways, which are the target of asthma prevention. G- bacteria such as E. coli O83 release outer membrane vesicles (OMVs) to communicate with the environment. Here we investigate whether intranasally administered E. coli O83 OMVs (EcO83-OMVs) can reduce allergic airway inflammation in mice. METHODS: EcO83-OMVs were isolated by ultracentrifugation and characterised their number, morphology (shape and size), composition (proteins and lipopolysaccharide; LPS), recognition by innate receptors (using transfected HEK293 cells) and immunomodulatory potential (in naïve splenocytes and bone marrow-derived dendritic cells; BMDCs). Their allergy-preventive effect was investigated in a mouse model of ovalbumin-induced allergic airway inflammation. RESULTS: EcO83-OMVs are spherical nanoparticles with a size of about 110 nm. They contain LPS and protein cargo. We identified a total of 1120 proteins, 136 of which were enriched in OMVs compared to parent bacteria. Proteins from the flagellum dominated. OMVs activated the pattern recognition receptors TLR2/4/5 as well as NOD1 and NOD2. EcO83-OMVs induced the production of pro- and anti-inflammatory cytokines in splenocytes and BMDCs. Intranasal administration of EcO83-OMVs inhibited airway hyperresponsiveness, and decreased airway eosinophilia, Th2 cytokine production and mucus secretion. CONCLUSIONS: We demonstrate for the first time that intranasally administered OMVs from probiotic G- bacteria have an anti-allergic effect. Our study highlights the advantages of OMVs as a safe platform for the prophylactic treatment of allergy. Video Abstract.

BioTechMed Graz Austria

Core Facility for Cell Imaging and Ultrastructural Research Faculty of Life Sciences University of Vienna Vienna Austria

Department of Clinical Medicine Aarhus University Aarhus Denmark

Department of Experimental Biology Faculty of Science Masaryk University Brno Czech Republic

Department of Infectious Diseases Aarhus University Hospital Aarhus Denmark

Field of Excellence Biohealth University of Graz Graz Austria

Hirszfeld Institute of Immunology and Experimental Therapy Polish Academy of Sciences Wroclaw Poland

Institute of Immunology and Microbiology 1st Faculty of Medicine Charles University and General University Hospital Prague Czech Republic

Institute of Molecular Biosciences Karl Franzens University Graz Austria

Institute of Specific Prophylaxis and Tropical Medicine Center for Pathophysiology Infectiology and Immunology Medical University of Vienna 1090 Vienna Austria

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Cell Commun Signal. 2023 Dec 6;21(1):349. doi: 10.1186/s12964-023-01405-9. PubMed

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A comprehensive summary of the ASEV-CzeSEV joint meeting on extracellular vesicles

Bacterial extracellular vesicles as intranasal postbiotics: Detailed characterization and interaction with airway cells

Correction: Extracellular vesicles of the probiotic bacteria E. coli O83 activate innate immunity and prevent allergy in mice