Abstract
Newcastle disease (ND) remains one of the most devastating avian viral diseases worldwide, inflicting severe economic losses on commercial poultry production. Although conventional live and inactivated vaccines confer systemic protection, they often fail to induce robust mucosal immunity and typically require labor-intensive or stress-inducing administration routes. In this study, we developed and evaluated a novel chitosan-tripolyphosphate nanoparticle (CS-NP) system for the oral delivery of inactivated Newcastle disease virus (NDV) in broiler chickens. Chitosan nanoparticles encapsulating NDV antigen (CS-NDV-NPs) were synthesized via ionic gelation, exhibiting a mean hydrodynamic diameter of 228.4 ± 14.2 nm, a positive surface charge of +29.6 ± 2.1 mV, and an encapsulation efficiency of 86.3 ± 1.8%. Broiler chicks were orally immunized at 7 and 21 days of age with CS-NDV-NPs and compared against cohorts receiving conventional ocular/nasal live LaSota vaccination, naked oral antigen, or mock treatment. Birds immunized with CS-NDV-NPs exhibited robust hemagglutination inhibition (HI) serum antibody titers (peaking at 7.8 log2) and significantly elevated levels of secretory immunoglobulin A (sIgA) in intestinal and tracheal washes compared to all oral control groups (P < 0.001). Following a lethal challenge with a velogenic genotype VII NDV strain at day 35, the CS-NDV-NP cohort achieved a 95% survival rate, accompanied by a marked reduction in cloacal and oropharyngeal viral shedding. These findings demonstrate that our chitosan-based oral delivery platform effectively stimulates both systemic and mucosal protective immunity, presenting a viable and stress-free alternative for mass vaccination in modern poultry systems.
