Isolation and evaluation of immunological adjuvant activities of saponins from the roots of Pulsatilla chinensis with less adverse reactions

In this study, the saponins (PCS) from the roots of Pulsatilla chinensis were evaluated for its haemolytic activity, acute toxicity and tested for potential adjuvant activity in mice immunized with ovalbumin (OVA) compared with that of Quil A saponin. The haemolytic activity of PCS was determined using 0.5% rabbit red blood cell with values of 15.41 and 7.42% at concentrations of 500 and 250 µg/mL, respectively. The saponins were tested for their toxicity by lethality in mice and were found to be less toxic at the same dose than their counterpart Quil A. ICR mice were immunized subcutaneously with OVA 100 µg in phosphate-buffered saline (PBS) alone or with OVA 100 µg in the presence of Quil A (10 µg) or PCS (50, 100 or 200 µg) twice at a 2-week interval. Four weeks later, the ConA-, LPS-, and OVA-induced splenocyte proliferation, OVA-specific antibodies levels (IgG, IgG1, and IgG2a) in serum, IL-2, and TNF-α were significantly enhanced by PCS at a high dose compared to that induced by Quil A. The P values of various testing activities in saponin-treated groups were obviously differential to that in the OVA-immunized mice (p < 0.05 or p < 0.01). This finding suggested that PCS might have an effect on Th1 and Th2 helper T cells. In conclusion, the results indicated that PCS showed slight side effects and at an appropriate dose could be used as a vaccine adjuvant to increase immune responses.