Effects of astragalus polysaccharide on the immune response to foot-and-mouth disease vaccine in mice

This study was conducted to evaluate the effects of astragalus polysaccharide (APS) on the immune responses of mice immunized with foot-and-mouth disease virus (FMDV) vaccine. BALB/c mice were randomly divided into five groups and 1 day before being immunized with FMDV vaccine, each group was orally administered APS at doses of 0, 0.125, 0.25, 0.5 and 1 mg, respectively. The cellular and humoral responses, including phagocytic capacity of peritoneal macrophage, the maturation of dendritic cells (DCs), splenic lymphocyte proliferation, cytokine production and antibody variation, were evaluated by a series of experiments after vaccination. The data showed that oral administration of APS significantly enhanced the phagocytic capacity of peritoneal macrophage, splenic lymphocyte proliferation, serum antibody titer, and the production of IL-4 and IL-10 in groups administered with 0.125–0.5 mg APS. The expression of CD40, CD86 and MHC-II on DCs was only slightly inhibited in mice given a low dose of APS, but was significantly enhanced in mice given higher doses. Furthermore, mice given the highest doses of APS showed markedly increased CD40 and MHC-II expression levels. These results suggest that orally administered APS could significantly enhance the efficacy of FMDV vaccination and has important implications for the further use of APS as a novel adjuvant.