Circulating nano-particulate TLR9 agonist scouts out tumor microenvironment to release immunogenic dead tumor cells

Abstract

Recent evidence suggest that a β-glucan derived from mushroom Schizophyllan(SPG) complexed with a humanized TLR9 agonistic CpG DNA, K3 (K3-SPG) is a promising vaccine adjuvant that induces robust CD8 T cell responses to co-administered antigen. However, it has not been investigated whether K3-SPG alone can act as an anti-cancer immunotherapeutic agent or not. Here, we demonstrate that intravenous injection of K3-SPG, but not CpG alone, is accumulated in the tumor microenvironment and triggered immunogenic cell death (ICD) of tumor cells by local induction of type-I interferon (IFN) as well as IL-12. Resultant innate immune activation as well as subsequent tumor-specific CD8 T cell responses were contributed the tumor growth suppression. This anti-tumor effect of K3-SPG monotherapy was also confirmed by using various tumor models including pancreatic cancer peritoneal dissemination model. Taken together, nano-particulate TLR9 agonist injected intravenously can scout out tumor microenvironment to provoke local innate immune activation and release dead tumor cells into circulation that may induce broader and protective tumor antigen-specific CD8 T cells.

Carbohydrate Conjugates in Vaccine Developments

“…This complex can induce antigen-presenting cell activation as well as Th1 and CD8 T cell responses (Kobiyama et al, 2014(Kobiyama et al, , 2016Ito et al, 2017). Intravenous injection of CpG-SPG complex suppressed tumor growth more efficiently than SPG, CpG or mixture of SPG and CpG on several tumor models (Kitahata et al, 2016). The CpG-SPG complex could be cross-linked to form nanogels with a larger size (∼150 nm) by mixing CpG-SPG and its complementary sequence (Kobiyama et al, 2014;Miyamoto SCHEME 8 | Structure of SPG, Poly(dA) and SPG complex.…”

CD63-Mediated Antigen Delivery into Extracellular Vesicles via DNA Vaccination Results in Robust CD8+ T Cell Responses

“…Tumor inoculation and tumor volume measurements were performed in the experimental mice as described previously (28). The mice were s.c. injected with 1 3 10 6 E.G-7 cells in 100 ml of PBS.…”

An Antigen-Free, Plasmacytoid Dendritic Cell–Targeting Immunotherapy To Bolster Memory CD8+ T Cells in Nonhuman Primates

“…K3-SPG is a nanoparticulate CpG ODN wrapped in the nonagonistic Dectin-1 ligand, SPG. K3-SPG should be superior to the current K3 CpG DNA, which is under clinical development (38), in terms of its ability to induce type I IFN production, and its adjuvant and monoimmunotherapeutic activities against cancer (19)(20)(21). However, discrepancies in the expression of PRRs, including TLR9, between mice and humans or NHPs limit the translation of any findings into clinical use (39).…”

“…Previously, we reported that K3-SPG can induce potent CTL responses and anticancer effects without Ag in mice (19)(20)(21); however, the effects of K3-SPG on the immune system of NHPs remain unknown. To confirm the potency of K3-SPG in NHPs, we first verified the activation of total memory CD8 + T cells by a single injection of 2 mg of K3, K3-SPG, or poly(I:C) in vivo (Fig.…”

“…K3-SPG induces the robust production of type I and type II IFN and Th1 type cytokines in human PBMCs and acts as a strong adjuvant for influenza split vaccine in mice and nonhuman primates (NHPs) to elicit Ag-specific Abs (19). K3-SPG can also stimulate strong Ag-specific CTL responses and induce the extensive production of anticancer cytokines, such as type I IFN and IL-12, to function as an anticancer monotherapy agent in mice (20,21). However, type I IFN, but not IL-12, is required for IFN-g production by human PBMCs and for the proliferation of CMV-specific CD8 + T cells in vitro (20).…”