Immunization with dendritic cell (DC)-based vaccines is a promising vaccination strategy to provide an effective personalized immunotherapy against cancer and other diseases. However, the results of clinical cancer immunotherapy trials carried out using DC-based vaccines to date have shown only modest clinical outcomes. We have previously demonstrated that a polyphenylpropenoid-polysaccharide complex (PPC), a lignin-carbohydrate complex derived from the cones of Pinus sylvestris, induces in vitro the differentiation and maturation of human mononuclear cell-derived DCs (Bradley et al., Int Immunopharmacol 2003;3) and murine bone marrow-derived DCs (BMDCs) (An et al., Anticancer Res 2010;30). Furthermore, oral administration of PPC enhanced a DC vaccine-induced melanoma antigen-specific CD8+ T-cell response (Burrows et al., BMC Complement Altern Med 2009;9) and the proliferative phase of a primary T cell response (Bradley et al., BMC Complement Altern Med 2014;14). In the present study, using a human papillomavirus (HPV)-induced mouse tumor model, we investigated whether ex vivo treatment of BMDCs with the synthetic lignin-like polyphenol polymers poly-caffeic acid (pCA) and poly-coumaric acid (pCoA), as well as PPC, improves the efficacy of DC-based vaccines. Polymerization of the phenylpropenoic acids caffeic acid (CA) and poly-coumaric acid (CoA) was performed by horseradish peroxidase/hydrogen peroxide-mediated enzymatic reactions. BMDCs were prepared by culturing murine bone marrow cells in the presence of GM-CSF for 8-10 days. These BMDCs were pulsed with synthetic tumor antigen peptides HPV16 E743-62 or HPV16 E743-77 that contain both a cytotoxic T lymphocyte (CTL) and a helper T cell epitope. Peptide-pulsed DCs were treated further ex vivo with synthetic polyphenol polymers or PPC and then injected twice into C57BL/6 mice. In addition, splenocytes obtained from immunized mice were restimulated with HPV16 E749-57 peptide (E7 CTL epitope) for 5 days. Tumor antigen-specific CD8+ T cell responses were assessed by HPV16 E749-57/H-2Db pentamer staining. We observed that immunization with PPC-treated HPV16 E743-77 peptide-loaded BMDCs significantly enhanced the induction of pentamer-positive CD8 positive cells in splenocytes (2- to 3-fold increase). Moreover, ex vivo restimulation with E7 CTL epitope peptide dramatically increased the number of pentamer-positive CD8 positive cells in splenocytes obtained from mice immunized with PPC-treated, peptide-loaded DCs (6- to 7-fold increase) when compared to splenocytes from mice immunized with PPC-nontreated, peptide-loaded DCs. Experiments using pCA and pCoA are in progress. We conclude that 1) ex vivo treatment with the natural PPC complex significantly potentiates the in vivo efficacy of DC-based HPV vaccines and 2) tumor antigen-specific CD8+ T cells are significantly expanded ex vivo by restimulating splenocytes from mice primed in vivo with PPC-treated, peptide-loaded BMDCs. In addition, our preliminary studies show that PPC, pCA and pCoA significantly increase the expression levels of CD8α, XCR1 and/or CLEC9A on murine BMDCs that have been demonstrated to be essential for the induction of CTL responses. Our approaches will provide innovative strategies for the design of more effective DC-based vaccines and adaptive T-cell therapies for the treatment of patients with cancer and other immune disorders.
Citation Format: Soichi Haraguchi, Tina Pastoor, William Guy Bradley, Akiko Tanaka. Improving the efficacy of dendritic cell-based human papillomavirus vaccines in mice using a natural lignin-carbohydrate complex and/or synthetic lignin-like polyphenol polymers. [abstract]. In: Proceedings of the AACR Special Conference: Tumor Immunology and Immunotherapy: A New Chapter; December 1-4, 2014; Orlando, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2015;3(10 Suppl):Abstract nr B29.
- ©2015 American Association for Cancer Research.