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

Escherichia coli A0 34/86 (EcO83) is a probiotic strain used in newborns to prevent nosocomial infections and diarrhoea. This bacterium stimulates both pro‐ and anti‐inflammatory cytokine production and its intranasal administration reduces allergic airway inflammation in mice. Despite its benefits, there are concerns about the use of live probiotic bacteria due to potential systemic infections and gene transfer. Extracellular vesicles (EVs) derived from EcO83 (EcO83‐EVs) might offer a safer alternative to live bacteria. This study characterizes EcO83‐EVs and investigates their interaction with host cells, highlighting their potential as postbiotic therapeutics. EcO83‐EVs were isolated, purified, and characterised following the Minimal Information of Studies of Extracellular Vesicles (MISEV) guidelines. Ex vivo studies conducted in human nasal epithelial cells showed that EcO83‐EVs increased the expression of proteins linked to oxidative stress and inflammation, indicating an effective interaction between EVs and the host cells. Further in vivo studies in mice demonstrated that EcO83‐EVs interact with nasal‐associated lymphoid tissue, are internalised by airway macrophages, and stimulate neutrophil recruitment in the lung. Mechanistically, EcO83‐EVs activate the NF‐κΒ signalling pathway, resulting in the nitric oxide production. EcO83‐EVs demonstrate significant potential as a postbiotic alternative to live bacteria, offering a safer option for therapeutic applications. Further research is required to explore their clinical use, particularly in mucosal vaccination and targeted immunotherapy strategies. This study investigates Escherichia coli A0 34/86 (EcO83), a probiotic strain known for its ability to prevent infections and diarrhoea in newborns and reduce allergic airway inflammation in mice. Although live probiotic bacteria are effective, they also harbour certain risks, such as possible infection and gene transfer. Therefore, this research investigates the use of extracellular vesicles (EVs) from EcO83 (EcO83‐EVs) as a safer alternative. The EVs were isolated and characterised in accordance with the MISEV guidelines. Experiments using human nasal epithelial cells, a mouse bone marrow‐derived macrophage cell line and mice showed that EcO83‐EVs promote the expression of immunomodulatory proteins and oxidative stress, and involve activation of the NF‐κB signalling pathway and nitric oxide production. These results suggest that EcO83‐EVs may represent a p