Immune-Enhancing Effect of Acanthopanax gracilistylus W. W. Smith Polysaccharides and Liposomes as Dilutions of Chicken Newcastle Disease Vaccine

W. W. Smith is a traditional Chinese herbal medicine that contains a variety of bioactive components, including polysaccharides. In this study, a polysaccharide was extracted from A. gracilistylus (AGSP) using an aqueous alcohol precipitation method. The sugar and glucuronic acid contents of AGSP are 43% and 8.06%, respectively. It was consisted of seven monosaccharides, mannose (Man), rhamnose (Rha), glucuronic acid (GlcA), galacturonic acid (GalA), glucose (Glc), galactose (Gal), and arabinose (Ara), with molar ratios of 0.32:0.15:0.04:0.12:5.12:2.50:0.85. AGSP liposomes (AGSPL) was prepared via the reverse-phase evaporation method. The encapsulation rate of AGSPL was 45.17% and its average particle size, polymer dispersity index (PDI), and zeta potential were 98.79 nm, 0.191, and -8.38 mV, respectively. The proliferation of chicken splenic T and B lymphocytes was significantly promoted in vitro at AGSP concentrations of 125-250 μg/mL and AGSPL concentrations of 15.63-31.25 μg/mL and 1.95-15.63 μg/mL, respectively. In vivo, the HI antibody titers and the concentrations of IFN-γ, IL-2, IL-4, and IL-6 in the AGSP and AGSPL groups were higher than those in the vaccine control (VC) and blank control (BC) groups. The efficacy of AGSPL was superior to that of AGSP. These findings indicate that AGSP and AGSPL markedly enhance the immunogenicity of ND vaccines, especially AGSPL, which is a promising candidate for polysaccharide-based vaccine diluents or adjuvants.