Engineered tolerogenic exosomes for treating type 1 diabetes autoimmunity

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Project Summary / Abstract The objective of this project is to engineer an exosome-based therapeutic platform to counteract pancreatic beta-cell autoimmunity as a strategy to treat or prevent type 1 diabetes (T1D). We hypothesize that exosomes can provide a virtually unlimited source of nanoparticulate, cell-free MHC-complexed antigen that, alongside appropriate negative regulators of immunity, can induce antigen-specific tolerance to beta cell autoreactive T cells without compromising system-wide immunity. Exosomes are small (30-150nm) biologically active membrane vesicles secreted by most cell types. Exosomal membranes are composed of a lipid bilayer with many lipid rafts that are enriched in cholesterol, sphingomyelin, and ceramide, giving them a long circulatory half-life in vivo and an extended shelf life. Exosomes can display immunostimulatory or immunoregulatory functions. Antigen presenting cells secrete large numbers of exosomes enriched in MHC peptide complexes and the adhesion molecule ICAM-1, enabling them to interface directly with T cells to control immune outcomes. In general, particulate antigen, such as that associated with exosomes, is far more immunologically potent than soluble, monomeric antigen. Our hypothesis and objective will be tested through performance of the following aims: • Aim 1 will establish that exosomes can be engineered to overexpress the immunoregulatory molecule programmed death-ligand 1 (PD-L1) and can act through this molecule and native MHC loaded with peptide antigen to suppress activated T cells in an antigen specific manner in vitro. • Aim 2 will evaluate the in vivo performance and mechanisms of tolerogenic exosomes in a mouse model of autoimmune diabetes. The prevalence of T1D in the U.S. continues to increase, despite growing knowledge of the pathogenesis and natural history of the disease, as well as better treatment options. Therefore, there is a significant need for a curative therapy that addresses the underlying autoimmune aspects of the disease by interfacing with autoreactive T cells. The key element of this proposal is directing multimeric, exosome-bound PD-L1 in an antigen specific manner to suppress diabetogenic T cells, thus addressing autoreactivity without compromising systemic immunity. The training environment shared between the UF Biomedical Engineering department and the UF Diabetes Institute allows for unique opportunities to collaborate and receive expert advice from leaders in both biomaterials and T1D autoimmunity. Training goals will be met by attending weekly seminars with leading researchers in biomaterials and T1D from around the country, professional development seminars offered through the College of Medicine, College of Medicine Endocrinology Grand Rounds, and weekly journal clubs.