Optimization of chicory root polysaccharide liposomes and their adjuvant efficacy in Newcastle disease vaccination

This study isolated chicory root polysaccharides (CP), optimized the preparation conditions of chicory root polysaccharides liposomes (CPL) and evaluated its effect on immune activity. The polysaccharide content and molecular weight of CP were 89.45 ± 1.25% and 2.72 kDa, respectively. The optimal preparation conditions of CPL were a phospholipid to cholesterol ratio of 5:1, a phospholipid-to-chicory polysaccharide ratio of 9:1, and a rotary evaporation temperature of 31 °C. The average encapsulation efficiency (EE) was 61.53 ± 0.19%, the average particle size, polymer dispersity index (PDI), and zeta potential were 86.96 ± 0.98 nm, 0.187 ± 0.008, and - 15.40 ± 1.23 mV, respectively. CP and CPL significantly promoted the proliferation of chicken splenic lymphocytes, splenic T and B lymphocytes at concentrations of 31.25-250 μg/mL and 7.813-31.25 μg/mL, 125-250 μg/mL and 1.953-31.25 μg/mL, 31.25-250 μg/mL and 15.625-31.25 μg/mL in vitro. CPL enhanced lymphocyte proliferation at substantially lower concentrations than CP, demonstrating superior immunostimulatory efficiency. In vivo, On days 7-49, HI(Hemagglutination Inhibition Antibody) antibody titers in the CPLH, CPLM and CPLL groups were significantly higher than those in the VC group. The serum antibody titers in the CPLM groups were significantly or numerically higher than both the CP and VC groups at days 35-49. The IL-2 and IL-4 concentrations in the CPLM group were significantly higher than those in the VC group on days 14-49. These findings suggest that CPL could serve as a novel vaccine diluent or immune adjuvant.