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

Abstract

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 250microg/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 100microg in phosphate-buffered saline (PBS) alone or with OVA 100microg in the presence of Quil A (10microg) or PCS (50, 100 or 200microg) 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-alpha 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.