Lactobacillus johnsonii-derived extracellular vesicles modulate gut microbiota metabolites and macrophage-related immune responses against Salmonella Typhimurium infection.

Salmonella Typhimurium is a significant pathogen causing diarrhea in weaned piglets, capable of triggering systemic inflammation and severe intestinal damage. As bioactive components of gut microbiota, extracellular vesicles (EVs) derived from Lactobacillus johnsonii (Lj-EVs) are likely to penetrate the intestinal mucus layer and reach host cells, potentially mediating host-microbiome interactions. Here, we found that Lj-EVs improved the intestinal barrier and attenuated intestinal injury in mice infected with S. Typhimurium. Multi-omics analysis showed that Lj-EVs intervention enriched mucin-utilizing Akkermansia. Moreover, Lj-EVs were associated with metabolic alterations, characterized by enhanced oxidative phosphorylation during homeostasis and suppression of HIF-1α-mediated glycolysis during infection. Proteomic profiling showed that Lj-EVs enriched functional proteins related to oxidative phosphorylation, indicating their potential immunomodulatory role. Notably, Lj-EVs modulated macrophage-mediated immune responses, contributing to limiting bacterial dissemination and alleviating intestinal inflammation. In conclusion, our study demonstrates that Lj-EVs alleviate Salmonella infection by reducing bacterial burden and confer metabolic and immunomodulatory benefits. These findings provide new evidence for future investigation of the protective roles of probiotic vesicles.