Enhancement of Astragalus polysaccharide on the immune responses in pigs inoculated with foot-and-mouth disease virus vaccine

The effects of Astragalus polysaccharides (APS) on the immune response in pigs immunized with foot-and-mouth disease virus (FMDV) vaccine were investigated. Fifteen pigs were randomly divided into five groups. Four groups were vaccinated with a FMDV inactivated vaccine. Pigs in three experimental groups were administered varying doses of APS (APS1, 5 mg/kg; APS2, 10 mg/kg; APS3, 20 mg/kg). The influence of APS on the number of CD3+CD4−CD8+ cytotoxic T cells, CD3+CD4+CD8+ T helper memory cells, and CD3−CD4−CD8+ natural killer cells among peripheral blood lymphocytes (PBL) in the three APS groups were significant compared to the vaccine group. In vitro stimulation of PBL by Con A and LPS in APS groups induced a stronger proliferative response at 2 and 6 weeks post-inoculation (PI). APS markedly increased the titer of FMDV-specific antibody in a dose-dependent manner, and up-regulated mRNA expression of IFN-γ and IL-6. APS could potentially be used as an immunomodulator for a FMDV vaccine and provide better protection against FMDV.

► The appropriate dose of APS elevates the proportions of some PBL subpopulations in FMDV vaccinated pigs at various periods.
► APS up-regulates specific antibody titers.
► APS enhances the proliferative capacity of PBLs stimulated by Con A or LPS.
► APS enhances the mRNA expression of IFN-γ and IL-6.
► APS can be used as an immunomodulator for the FMDV vaccine by stimulating both humoral and cellular immune responses.