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 μg alone or with BSA 100 μg dissolved in saline containing Ast VII (30, 60, 120 and 240 μg), Mac B (30, 60, 90 and 120 μg) 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 μg/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 μg (P<0.001), and 60, 90 and 120 μg (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 μg), Mac B (90 μg) and Freund's as compared to the control group (P<0.01 or P<0.001). Moreover, the IFN-γ 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-γ production such as Freund's, two weeks after the last immunization at doses of 120 μg and 90 μg, 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.