Combining gp96-Ig vaccination and mTL1A-Ig fusion protein boosts anti-tumor immunity. (165.10)

Abstract

Abstract Tumor necrosis factor 25 (TNFR25) and its natural ligand, TL1A, inhibit the suppressive activity of regulatory T cells (Tregs) and block de novo biogenesis of antigen specific induced Treg (iTreg). TL1A/TNFR25 co-stimulates CD4+ and CD8+ T cells and promotes proliferation and cytokine production in the presence of antigen. Due to the role of TNFR25 as a co-stimulator of T cells, we hypothesize that combination therapy with g96-Ig vaccination will enhance the robust expansion of CD8 CTL observed with vaccine alone. As expected, gp96 vaccine with TNFR25 agonistic antibody, 4C12, enhanced CD8 CTL expansion and tumor rejection as compared to vaccine only. Here we genetically engineered murine TL1A-Ig fusion proteins that differ in retention of the cleavage site in the extracellular domain fused to the C-terminus of mIgG1 Fc. The in vitro potencies of the TNFR25 agonist fusion proteins were confirmed by caspase activation and binding assays. Apparent molecular weights were measured as 447 and 152 kDa by gel filtration, and biological half life was determined as 7 hours in mice. In vitro, mTL1A-Ig with anti-CD3 caused rapid proliferation of all CD4+ T lymphocytes, including CD4+FoxP3+Tregs. Enhanced antigen specific CTL expansion was observed in the spleen and peritoneal cavity when naïve mice were treated with vaccine and mTL1A-Ig. We will optimize dose and scheduling of mTL1A-Ig injection, which can be utilized in combination with the vaccine to enhance therapeutic benefit.