Procyanidin, a kind of biological flavonoid, induces protective anti-tumor immunity and protects mice from lethal B16F10 challenge

•Procyanidin enhances APC activation both in vitro and in vivo•Inhibition of tumor growth by B16F10 tumor vaccine in B16F10 melanoma subcutaneous model•Procyanidin enhances protective response against lethal B16F10 challenge•Functional analyses of T cells induced by B16F10 tumor vaccine•Splenocytes from tumor-bearing mice treated with B16F10 tumor vaccine retain cytotoxic activity in vitro

Recently, increasing evidences show that procyanidin (PC) modulate immune responses in human. To evaluate adjuvant effects of PC on vaccine immune modulation and anti-tumor activity, we formulated PC with B16F10 tumor antigen as tumor vaccine to immune C57BL/6 mice and used intramuscular injection before challenge with tumor B16F10 cells. Our results revealed that PC enhanced T cell-mediated immune responses both in vitro and in vivo. Moreover, the B16F10 tumor vaccine induced some degree of anti-tumor effects as evaluated by the inhibition of tumor growth and the prolongation of survival. The tumor-bearing mice showed a high level of specific cytotoxic activity and had activated CD8 T cells that secreted perforin, IFN-γ and TNF-α in response to the stimulation with antigen in vitro. Taken together, current study presents evidence that PC may be used as a promising vaccine adjuvant.