Innovative strategies to enhance Treg function and promote IS drug-free kidney transplant survival

P01 Project 2 Summary A long-pursued goal in clinical organ transplantation (Tx) is the achievement of immunosuppression (IS)- free graft survival and long-term graft acceptance. Long-term patient and graft survival rates remain suboptimal due to high rates of morbidity and mortality associated with life-long IS. Pathogenic IS-resistant memory T cells (Tmem) are a major hurdle to long-term graft acceptance. Accordingly, novel approaches to restrain donor-reactive Tmem while sparing and augmenting donor antigen (Ag)-specific regulatory T cells (Treg) are critical to achieve prolonged graft survival with IS withdrawal. Post-Tx inflammation promotes Ag-presenting cell function and Tmem persistence which are detrimental to graft survival. A network of interactive pro-inflammatory cytokines, interleukin (IL)-6, IL-7 and IL-15, promotes survival and persistence of systemic and graft-infiltrating pathogenic Tmem. Adoptive transfer of ex vivo-expanded Treg to augment Ag-specific Treg is at the forefront of tolerogenic cell therapy. Our previously published studies indicate that ex vivo-expanded conventional Treg can lose their survival and regulatory signature after infusion. Recently, rodent Tx studies have demonstrated that Treg engineered with chimeric antigen receptors (CARTreg) that recognize specific donor MHC molecules, home and reside in target tissues and are highly suppressive compared to conventional Treg. Our overall approach aims to prolong IS-free graft survival in a stringent preclinical nonhuman primate model using innovative therapeutic strategies and cutting-edge technologies. We propose to 1) prevent early post-Tx IL-6-mediated pro-inflammatory effects, 2) block IL-7- & IL-15- mediated pathogenic Tmem persistence, 3) augment darTreg through administration of donor Ag (MHC)-specific CARTreg, combined with (4) selective targeting of dendritic cells in situ using inhibitory nanoparticles (NPs). We aim to achieve these goals using novel rhesus-specific cytokine modulating reagents, cutting edge rhesus CARTreg therapy, and anti-DEC205-mTORi NPs. Our Specific Aims are: Specific Aim 1: Mitigate post-Tx inflammatory responses and eliminate IS-resistant donor- reactive pathogenic Tmem through cytokine immunomodulation. (n=18 transplants) Specific Aim 2: Augment donor Ag-specific Treg through infusion of ex vivo-expanded genetically engineered Bw6-specific CARTreg. (n=6 transplants) Specific Aim 3: Achieve durable donor-reactive T cell regulation through CARTreg infusion combined with either cytokine modulation or in situ targeting of dendritic cells. (n=12 transplants) The proposed studies, in strong co-ordination/synergy with Project 1 and each Core will provide new mechanistic insights into induction of donor-specific unresponsiveness and generate novel therapeutic strategies with high potential for clinical translation in the near future.