Cancer patients having anti-programmed cell death-1 (PD-1)/PD ligand 1 (L1)-unresponsive tumors may benefit from advanced immunotherapy. Double-stranded RNA triggers dendritic cell (DC) maturation to cross-prime antigen-specific cytotoxic T lymphocytes (CTLs) via Toll-like receptor 3 (TLR3). The TLR3-specific RNA agonist, ARNAX, can induce anti-tumor CTLs without systemic cytokine/interferon (IFN) production. Here, we have developed a safe vaccine adjuvant for cancer that effectively implements anti-PD-L1 therapy. Co-administration of ARNAX with a tumor-associated antigen facilitated tumor regression in mouse models, and in combination with anti-PD-L1 antibody, activated tumor-specific CTLs in lymphoid tissues, enhanced CTL infiltration, and overcame anti-PD-1 resistance without cytokinemia. The TLR3-TICAM-1-interferon regulatory factor (IRF)3-IFN-beta axis in DCs exclusively participated in CD8+ T cell cross-priming. ARNAX therapy established Th1 immunity in the tumor microenvironment, upregulating genes involved in DC/T cell/natural killer (NK) cell recruitment and functionality. Human ex vivo studies disclosed that ARNAX+antigen induced antigen-specific CTL priming and proliferation in peripheral blood mononuclear cells (PBMCs), supporting the feasibility of ARNAX for potentiating anti-PD-1/PD-L1 therapy in human vaccine immunotherapy.

Author Info: (1) Department of Vaccine Immunology, Hokkaido University Graduate School of Medicine, Kita 15, Nishi 7, Kita-ku, Sapporo 060-8638, Japan. (2) Department of Pathology and Tumor Bio

Author Info: (1) Department of Vaccine Immunology, Hokkaido University Graduate School of Medicine, Kita 15, Nishi 7, Kita-ku, Sapporo 060-8638, Japan. (2) Department of Pathology and Tumor Biology, Graduate School of Medicine, Kyoto University, Kyoto 606-8501, Japan. (3) Research Center and Global Station for Zoonosis Control, GI-CoRE, Hokkaido University, Sapporo 001-0020, Japan. (4) Department of Pathology and Tumor Biology, Graduate School of Medicine, Kyoto University, Kyoto 606-8501, Japan. (5) Department of Vaccine Immunology, Hokkaido University Graduate School of Medicine, Kita 15, Nishi 7, Kita-ku, Sapporo 060-8638, Japan. Electronic address: seya-tu@pop.med.hokudai.ac.jp. (6) Department of Vaccine Immunology, Hokkaido University Graduate School of Medicine, Kita 15, Nishi 7, Kita-ku, Sapporo 060-8638, Japan. Electronic address: matumoto@pop.med.hokudai.ac.jp.