Isolation and evaluation of immunological adjuvant activities of saponins from Polygala senega L.

We have identified saponins in the root of Polygala senega L., a plant indi genous to the Canadian prairies, which display immunopotentiation activity to protein and viral antigens, By two-step extraction and hemolytic activit y-guided fractionation by silica flush chromatography six saponin fractions were generated and their HPLC profiles determined. Two dominant fractions, designated as PS-I and PS-2, were tested for adjuvant activity in mice imm unized with ovalbumin, and hens immunized with rotavirus. The resulting adj uvant activity was compared with that of Quil A saponin. The P. senega sapo nins increased specific antibody levels to the antigens, in both mice and h ens. In mice, there was a preferential increase of the IgG(2a) subclass, an d upon in vitro secondary antigen stimulation, high IL-2 and IFN-gamma leve ls were observed in spleen cell cultures from P. senega saponins-immunized. animals. 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 Qui l A. The results of this study indicated the potential of P. senega saponin s as vaccine adjuvants to increase specific immune responses. (C) 1999 Else vier Science Ltd. All rights reserved.