Preparation and immunoactivity of sulfated glucan from Saccharomyces cerevisiae liposomes

This study optimized the preparation conditions of sulfated glucan from Saccharomyces cerevisiae liposomes (SGSCL) and evaluated its effect on immune activity. SGSCL was prepared using the reverse evaporation method, and its immune activity was assessed by measuring the proliferation of chicken spleen lymphocytes, hemagglutination inhibition (HI) antibody titers, and serum cytokine concentrations in chickens vaccinated with the Newcastle disease (ND) vaccine. The optimal preparation conditions were a phospholipid-to-cholesterol mass ratio of 5.4:1, a phospholipid-to-SGSC mass ratio of 10:1, and a rotary evaporation temperature of 40 °C. The average encapsulation efficiency (EE) was 63.92%, whereas the mean particle size, polymer dispersity index (PDI), and zeta potential were 90.39 ± 1.71 nm, 0.203 ± 0.004, and -41.13 ± 1.05 mV, respectively. SGSCL significantly promoted the proliferation of chicken spleen lymphocytes, splenic T and B lymphocytes at concentrations of 100-800 µg/mL, 800 µg/mL and 200-800 µg/mL in vitro. The best proliferative effect on splenic lymphocytes were at 400 µg/mL, 800 µg/mL, and 800 µg/mL. In vivo, on days 7 and 14, HI antibody titers in the SGSCL-H, SGSCL-M, and SGSCL-L groups were significantly greater than those in the VC group. The serum antibody titers in the SGSCL-H and SGSCL-M groups were significantly or numerically elevated compared to the VC group at all time points post-vaccination. The IL-2, IL-6, IL-4, and IFN-γ concentrations in the SGSCL-H group were significantly higher than that in the VC group on D28 and D35. These findings suggest that SGSCL could serve as a novel vaccine diluent or immune adjuvant.