Robust antitumor effects of SNA-based T cell therapy

Abstract

Abstract The use of toll like receptor (TLR) agonists for immunotherapy remains under intense investigation. Activation of TLRs unleash the power of dendritic cells (DCs) to induce a robust antitumor CD8+ T cell response. However, the role of TLRs in CD8+ T cells has been largely overlooked. T cells do express endosomal TLR9, but it is not readily targetable in these non-phagocytic cells. Using the novel delivery platform of spherical nucleic acids (SNAs), we have devised a way to efficiently activate endosomal TLR9 by CpG, while simultaneously delivering tumor antigens to intracellular compartments in T cells. Activation of TLR9 in CD8+ T cells endows them with special properties. First, T cells themselves express appreciable levels of co-stimulatory molecules after activation of CpG derived from SNAs, thereby functioning as antigen presenting cells to cross-prime antigen-specific CD8+ T cells. Second, SNA activated T cells act as chaperones (T chaperones) of SNA material. Through exosomal transfer, T chaperones shuttle CpG and antigen, mouse or human, to bystander DCs for further cross-presentation of antigen. Third, antigen specific T chaperones are highly cytotoxic and resist tumor induced immune suppression. These combined effects of adoptive therapy using tumor antigen specific T chaperones achieve tumor regression in aggressive melanoma models without irradiation or cytokine supplementation, which complicate T cell-based therapies. T chaperones represent a novel cell-based therapy that co-delivers adjuvant and antigen to efficiently boost antitumor CD8+ T cell activity, eliminating the need for viral manipulation and shortens the long, and costly, production time associated with other T cell therapies.