Structural Characterization of LDP-1, a Polysaccharide from Lyophyllum decastes , and Its Protective Effects against PEDV-Induced Intestinal Inflammation In Vitro and In Vivo

Porcine epidemic diarrhea virus (PEDV) infection causes severe intestinal inflammation and barrier injury in piglets. In this study, a purified polysaccharide fraction, Lyophyllum decastes polysaccharide-1 (LDP-1), was isolated and structurally characterized, and its protective effects against PEDV-induced intestinal injury were evaluated in IPEC-J2 cells and piglets. LDP-1 predominantly comprised glucose and exhibited a peak molecular weight of 30.56 kDa, with an α-(1→4)-glucan backbone. In vitro, LDP-1, particularly under pretreatment and whole-process treatment, attenuated PEDV-induced inflammatory cytokine expression. In vivo, LDP-1 pretreatment reduced diarrhea, alleviated intestinal pathological injury, and partially restored villus–crypt morphology. LDP-1 also decreased intestinal interleukin-6 (IL-6), interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α) expression and restored zonula occludens-1 (ZO-1), Claudin-1, and Occludin expression. These findings indicate that LDP-1 protects against PEDV-induced intestinal inflammation and barrier injury and may serve as a potential natural protective agent.