Haemolytic activities and adjuvant effect of Astragalus membranaceus saponins (AMS) on the immune responses to ovalbumin in mice

In this study, the haemolytic activities of Astragalus membranaceus saponins (AMS) and its adjuvant potentials on the cellular and humoral immune responses of ICR mice against OVA were evaluated. We determined the haemolytic activity of AMS using 0.5% rabbit red blood cell. AMS showed a slight haemolytic effect, with its haemolytic percents being 0.66% at the concentration of 500 μg/ml. Furthermore, the adjuvant potentials of AMS at three dose levels on the cellular and humoral immune responses of ICR mice against ovalbumin (OVA) were investigated. ICR mice were immunized subcutaneously with OVA 100 μg alone or with OVA 100 μg dissolved in saline containing Alum (200 μg), QuilA (10 and 20 μg) or AMS (50, 100 or 200 μg) on Day 1 and 15. Two weeks later (Day 28), concanavalin A (Con A)-, lipopolysaccharide (LPS)- and OVA-stimulated splenocyte proliferation and OVA-specific antibodies in serum were measured. AMS significantly enhanced the Con A-, LPS-, and OVA-induced splenocyte proliferation in the OVA-immunized mice especially at a dose of 100 μg (P < 0.05 or P < 0.001). OVA-specific IgG, IgG1 and IgG2b antibody titers in serum were also significantly enhanced by AMS compared with OVA control group (P < 0.01 or P < 0.001). Moreover, no significant differences (P > 0.05) were observed between enhancing effect of AMS and QuilA on the OVA-specific IgG, IgG1 and IgG2b antibody responses to OVA in mice. In conclusion, the results suggest that AMS could be safely used as adjuvant with low or non-haemolytic effect.