Lactiplantibacillus plantarum extracellular vesicles exert anti-PEDV effects through STING-dependent autophagy

Porcine epidemic diarrhea virus (PEDV) infection causes severe gastrointestinal and lethal disease in piglets, leading to huge economic losses for the swine industry worldwide. Recent studies have emphasized probiotics can regulate innate immunity and cellular functions through interaction with intestinal epithelial cells via extracellular vesicles (EVs) as effective carriers. The cGAS-STING signaling pathway is crucial for inducing type I interferons (IFNs) to establish antiviral innate immunity. It also triggers cellular autophagy, which helps maintain intracellular environmental homeostasis. In our study, we found that Lactiplantibacillus plantarum extracellular vesicles (LpEVs) significantly activated the cGAS-STING signaling pathway in porcine intestinal epithelial cells (IPEC-J2), thereby enhancing antiviral immune responses. Notably, compared to the untreated control group, 10 μg/mL LpEVs retained the capacity to activate the cGAS-STING pathway, but their activation efficacy was significantly lower than that of 2.5 μg/mL, suggesting a potential feedback regulatory mechanism at higher concentrations. Furthermore, 10 μg/mL LpEVs regulated cGAS-STING activation through autophagy induction, and this autophagic response was STING-dependent. Additionally, LpEVs at concentrations of 2.5, 5, and 10 μg/mL all significantly inhibited the proliferation of PEDV. However, 10 μg/mL LpEVs exhibited a stronger inhibitory effect on PEDV replication compared to 2.5 or 5 μg/mL doses, and this enhanced antiviral activity was closely associated with autophagy. Our findings elucidate the underlying mechanism of antiviral effects of probiotics through regulating innate immunity and autophagy, which highlights the critical role of LpEVs in preventing PEDV infection as a potential antiviral agent.