Adjuvant effect of a novel water-soluble polysaccharide isolated from the stem of Physalis alkekengi L. var. francheti (Mast.) Makino

Water-soluble polysacchride (WSP) was isolated and purified from the mature stem of Physalis alkekengi L. var. francheti (Mast.) Makino, which is a traditional Chinese medicine herb. Gas chromatography (GC) analysis indicated that WSP was an acid heteropolysaccharide, which was composed of Rha, Ara, Gal, Glc and GalA in molar ratio of 2.6 : 1.0 : 6.5 : 3.5 : 2.4. More importantly, adjuvant activity of WSP was evaluated in ICR mice in present study. Male ICR mice were immunized subcutaneously with ovalbumin (OVA) alone, OVA/WSP, OVA/QuilA, and saline two times at 14-day interval. The mice were sacrificed two weeks after the last immunization to analyze antibody titers in serum. It was observed that WSP significantly enhanced OVA-specific antibody titers (IgG, IgG1, IgG2b) in serum when compared with OVA-injected mice (P<0.05 or P<0.01). Thus, WSP could be considered as a promising adjuvant eliciting both Th1 and Th2 responses to improve the efficacy of vaccine.