Chitosan (Cs) nanoparticles can be potentially employed as promising carriers for oral DNA vaccines. In this study, stearic acid-modified chitosan (StCs) nanocarriers were developed to improve the oral delivery of an IHNV DNA vaccine in rainbow trout. Physicochemical characteristics of Cs and StCs nanoparticles were analyzed by DLS, zeta potential, FE-SEM, and FT-IR spectroscopy. The fatty acid modification resulted in a slight decrease in DNA loading capacity but a notable enhancement in the loading efficiency of Cs nanoparticles. StCs nanoparticles exhibited robust stability in simulated esophageal (pH 7) and gastric (pH 2) environments, with threefold increased DNA release in simulated intestinal fluid (pH 9). Both nanocarriers showed minimal cytotoxicity toward Vero and EPC cells. In vitro transfection efficacy of StCs surpassed that of Cs nanoparticles across examined cell types, confirmed by GFP expression and RT-PCR. Under in vivo conditions, StCs-pDNA induced significantly higher antigen expression along the intestinal tract compared to unmodified Cs-pDNA, confirming enhanced mucosal delivery. Oral vaccination with StCs nanoparticles increased expression of immune-related genes ( mx-1, ifn-1, igt, igm ) compared to Cs nanoparticles. Following the IHNV challenge, St modification reduced cumulative mortality from 64% to 44%, increasing relative percent survival (RPS) from 36% to 54.1%. These findings demonstrate that StCs nanoparticles serve as effective pH-sensitive nanocarriers for cost-effective oral DNA vaccine delivery in fish by feeding.. • Stearic acid-modified chitosan (StCs) nanoparticles were developed for a oral DNA vaccine. • StCs exhibited improved pH-responsive targeted release compared to unmodified Cs. • Enhanced pDNA loading efficiency and in vitro transfection were achieved with StCs. • StCs-pDNA induced significantly higher antigen expression in the intestinal tract. • Orally vaccinated fish with StCs showed improved protection against IHNV challenge.
Mohammadinezhad et al. (2026) studied this question.