Engineering Extracellular Vesicles for Tolerogenic Immunotherapy

About This Grant

PROJECT SUMMARY Autoimmune diseases impact ~25 million people in the United States and are increasing in prevalence. Autoimmune diseases are driven by a failure of immunological tolerance that triggers aberrant immune responses against self-antigens that can impart debilitating morbidities and even death. There are no cures for autoimmune disease and current treatments non-specifically blunt immune responses against both self- and non-self-antigen, requiring life-long treatment compliance that leaves patients more susceptible to infection and malignancy. We propose to develop a develop and test a new strategy for targeted treatment of autoimmune diseases that harnesses the intrinsic immunoregulatory properties of extracellular vesicles (EVs). EVs are secreted by all cell types as a mechanism for promoting transfer of molecules between cells and have been implicated in the maintenance or induction of immunological tolerance through their ability to deliver diverse immunoregulatory cargo. We hypothesize that EVs derived from immunosuppressive cell sources and engineered to deliver autoantigens can be employed as a tolerogenic vaccine (i.e., inverse vaccine) that promotes antigen-specific T cell tolerance that abrogates autoimmune disease. Towards this end, we have devised strategies for exogenous loading of peptide antigens onto EV surfaces, thereby enabling coordinated delivery of antigens and immunosuppressive EV cargo to antigen presenting cells (APCs), resulting in the presentation of autoantigen in a potently tolerogenic context. While our EV-based tolerogenic vaccine platform – tolEVax – is amenable to EVs isolated any cell source and can be applied to several autoimmune diseases, we will focus on engineering of EVs derived from mesenchymal stem cells (MSC-EVs) and will test our approach in a model of multiple sclerosis. We propose to establish tolEVax as a promising strategy for promoting immune tolerance and treating autoimmunity through two Specific Aims. In Aim 1, we will load MSC- EVs with peptide antigens, evaluate effects on antigen biodistribution and uptake by APCs, and characterize effects on antigen-specific CD8+ and CD4+ T cell responses to model antigens. In Aim 2, we will evaluate the capacity of tolEVax to inhibit autoreactive T cell responses and self-antigen mediated inflammation and pathology in a model of multiple sclerosis. We expect these studies to identify MSC-EVs as potently tolerogenic antigen nanocarriers, to provide new insight into how EVs modulate adaptive immune responses, and to demonstrate the efficacy of tolEVax as a potential treatment for MS. Overall, this research will result in a platform technology that addresses the unmet need for effective antigen-specific immunotherapies for autoimmune disease by exploiting the inherent and multimodal immunosuppressive functions of EVs.