Protective effects of selenium-modified Viola philippica polysaccharide-loaded yeast microcapsules against Salmonella Typhimurium infection in chicks.

This study aimed to investigate the protective effects of selenium-modified Viola philippica polysaccharide-loaded yeast microcapsules (SVPP@YM) against Salmonella Typhimurium (ST) infection in chicks. Encapsulation of SVPP by yeast microcapsules was confirmed via SEM, TEM, particle size analysis, zeta potential measurement, and FT-IR, with an encapsulation efficiency and loading capacity of 46.50 ± 2.80 % and 30.07 ± 1.71 %, respectively. In vitro, SVPP@YM showed no significant cytotoxicity toward HD11 cells at concentrations ranging from 3.125 to 12.5 μg/mL and exhibited higher cellular uptake efficiency than free SVPP. SVPP@YM effectively reduced NO, ROS, and MDA levels in LPS-stimulated HD11 cells, downregulated the expression of inflammatory mediators, and enhanced GSH-Px activity and SOD expression. In vivo, SVPP@YM alleviated ST-induced clinical symptoms, improved body weight and immune organ indices, preserved jejunal morphology, enhanced ZO-1 expression and tight junction-related gene expression, increased sIgA content, and reduced intestinal inflammatory and oxidative stress responses. In addition, SVPP@YM reshaped the gut microbiota composition by increasing microbial diversity, enriching beneficial bacteria, and reducing pathogenic taxa. Spearman correlation analysis further revealed that Escherichia-Shigella abundance was negatively correlated with parameters related to intestinal barrier function, mucosal immunity, and antioxidant capacity, but positively correlated with MDA, IL-1β, and TNF-α. Collectively, these findings indicate that SVPP@YM effectively protected chicks against ST-induced injury and may serve as a natural intervention strategy for ST infection in poultry.