Adjuvant effects of Astragalus saponins Macrophyllosaponin B and Astragaloside VII

Aim of the study: The present study was undertaken to evaluate the hemolytic activities of two immunomodulator Astragalus saponins [Macrophyllosaponin B (MacB) from Astragalus oleifolius DC. and Astragaloside VII (Ast VII) from Astragalus trojanus Stev.], and their adjuvant potentials on the cellular and humoral immune responses of Swiss albino mice against BSA. Materials and methods: The hemolytic activity of Mac B and Ast VII was determined using 0.5% rabbit red blood cell. For adjuvant activity, Swiss albino mice were immunized subcutaneously with BSA 100 mu g alone or with BSA 100 mu g dissolved in saline containing Ast VII (30, 60, 120 and 240 mu g), Mac B (30, 60, 90 and 120 mu g) or Freund's adjuvant on Days 1 and 15. Sera and splenocytes were collected 2 weeks after the last immunization for concanavalin A (Con A)-, lipopolysaccharide (LPS)- and BSA-stimulated splenocyte proliferation assay and measurement of BSA-specific antibodies in serum. Results: Mac B and Ast VII showed a slight hemolytic effect, with 0.42% and 0.54% values, respectively, at the highest concentration of 500 mu g/ml. Mac B and Ast VII significantly enhanced the Con A-, LPS-, and BSA-induced splenocyte proliferation in the BSA-immunized mice especially at 120 and 240 mu g (P < 0.001), and 60, 90 and 120 mu g (P < 0.05, P < 0.01 or P < 0.001) doses, respectively. BSA-specific IgG, IgG1 and IgG2b antibody titers in serum were also significantly enhanced by Ast VII (120 mu g). Mac B (90 mu g) and Freund's as compared to the control group (P < 0.01 or P < 0.001). Moreover, the IFN-gamma and IL-4 levels in the sera were detected using ELISA two weeks after the last immunization. Ast VII and Mac B were also found to stimulate IFN-gamma production such as Freund's, two weeks after the last immunization at doses of 120 mu g and 90 mu g, respectively, as compared to the control. Conclusion: Results show that Ast VII and Mac B generate important specific antibody and cellular response against BSA in mice, proving their potentials as a new class saponin adjuvant. (C) 2011 Elsevier Ireland Ltd. All rights reserved.