Evaluation of immunologic enhancement mediated by a polysaccharide isolated from the fruit of Physalis alkekengi L. var. francheti (Mast.) Makino

The study was to investigate the immunologic enhancement mediated by a polysaccharide (designated PPSB) purified from the mature fruits of Physalis alkekengi L. var. francheti (Mast.) Makino. Male ICR mice were immunized subcutaneously with ovalbumin (OVA) alone, OVA/PPSB, OVA/QuilA, and saline two times at 14-day interval. The mice were sacrificed two weeks after the last immunization to analyze humoral and cellular immunity. Delayed-type hypersensitivity (DTH) response was further detected. Moreover, toxicity of PPSB was evaluated by haemolytic activity and acute toxicity assay. The results showed that PPSB significantly enhanced OVA-specific antibody titers (IgG, IgG1, IgG2b) in serum, the concanavalin (ConA), lipopolysaccharide (LPS), OVA-induced splenocyte proliferation, proportions of CD4 + and CD8 + T lymphocytes in spleen, DTH response when compared with OVA-injected mice (P < 0.05 or P < 0.01). Toxicity assay indicated PPSB was non-toxic. Therefore, PPSB mediated both humoral immunity and cellular immunity, and it was non-toxic. Thus, PPSB should be considered as a promising adjuvant eliciting both Th1 and Th2 responses to improve the efficacy of vaccine.