Novel polysaccharide adjuvant from the roots of Actinidia eriantha with dual Th1 and Th2 potentiating activity

The plant polysaccharides are recognized as an effective biological response modifier with low toxicity. In this study, the water-soluble polysaccharide from the roots of Actinidia eriantha (AEPS) was evaluated for its toxicity and adjuvant potential on the specific cellular and humoral immune responses to ovalbumin (OVA) in mice. AEP did not cause any mortality and side effects when mice were administered subcutaneously twice at the dose up to 5.0 mg at intervals of 7 days. The mice were immunized subcutaneously with OVA 100 μg alone or with OVA 100 μg dissolved in saline containing Quil A (10 μg) or AEPS (25, 50, or 100 μg) on days 1 and 15. Two weeks later, splenocyte proliferation, natural killer (NK) cell activity, production and mRNA expression of cytokines from splenocytes, and serum OVA-specific antibody titers were measured. The Con A-, LPS-, and OVA-induced splenocyte proliferation and the serum OVA-specific IgG, IgG1, IgG2a, and IgG2b antibody titers in the immunized mice were significantly enhanced by AEPS (P < 0.05, P < 0.01 or P < 0.001). AEPS also significantly promoted the production of Th1 (IL-2 and IFN-γ) and Th2 (IL-10) cytokines and up-regulated the mRNA expression of IL-2, IFN-γ, IL-4 and IL-10 cytokines and T-bet and GATA-3 transcription factors in splenocytes from the immunized mice (P < 0.05, P < 0.01 or P < 0.001). Besides, AEPS remarkably increased the killing activities of NK cells from splenocytes in the immunized mice (P < 0.01 or P < 0.001). The results indicated that AEPS had strong potential to increase both cellular and humoral immune responses and elicit a balanced Th1/Th2 response, and that AEPS may be a safe and efficacious adjuvant candidate suitable for a wide spectrum of prophylactic and therapeutic vaccines.