Tunable Assembly of Regulatory Immune Signals to Promote Myelin-specific Tolerance

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During autoimmunity, the body identifies and attacks “self” molecules as foreign. Current therapies employ broad immunosuppression, which is beneficial to patients, but can leave them immunocompromised. This limitation, along with the lack of cures, has sparked intense interest in strategies that could control autoimmunity with vaccine-like specificity, leaving the rest of the immune system intact. Several pre-clinical reports and clinical trials have investigated this theory to combat multiple sclerosis (MS), a neurodegenerative disease that impacts many Veterans and occurs when myelin in the central nervous system (CNS) is attacked by the immune system. An important finding from these studies is that co-administration of myelin peptide and tolerizing immune signals can promote the development of regulatory T cells (TREGS) that ameliorate disease. Interestingly, one set of pathways hindering control of myelin-driven inflammation are toll like receptors (TLRs). In healthy individuals, these pathways detect pathogen-associated patterns to support innate immunity. However, recent studies reveal that toll like receptor signaling – TLR9, for example – is elevated in human MS and in experimental autoimmune encephalomyelitis (EAE), a mouse model of MS. Suppressing TLR9 function not only reduces inflammation, but also promotes TREGS and improves disease. Polarization of naïve, myelin-reactive T cells into inflammatory T cells (e.g., TH17) or TREGS is localized to spleen and lymph nodes (LNs), tissues that coordinate immunity. Thus, strategies that help program how T cells differentiate when myelin is presented in LNs – for example, delivering regulatory cues – could generate large populations of myelin-specific TREGS that stop pathogenic immune cells without broad suppression. Nanotechnology holds great promise in this area through increased control over targeting, release kinetics, and delivery of multiple signals. However, many polymer particles and other materials exhibit intrinsic features that activate inflammatory pathways, which could exacerbate autoimmune disease. Strategies that mimic attractive features of biomaterials, while eliminating inflammatory “carrier” effects could be transformative for new therapies for MS or other autoimmune diseases. Toward this goal, the proposed research will use polyionic immune signals to create novel nanostructured capsules built entirely from regulatory immune signals and myelin antigens. These immune polyelectrolyte multilayers (“iPEMs”) are assembled through electrostatic interactions on a template, which is then removed to leave vaccines capsules that juxtapose myelin and TLR9-suppressive nucleic acids (GpG). Since there is no carrier, the density of signals in iPEMs is very high relative to lipid or polymer formulations with cargo embedded in a matrix. Further, the particles condense the signals at high densities, a characteristic that could promote differentiation toward TREG through co-localization of myelin with GpG in LNs. Biodistribution studies in mice reveal that even upon trafficking to LNs, iPEMs maintain juxtaposition of myelin and the regulatory signal. Pilot studies in a mouse model of MS demonstrate striking efficacy, with iPEM treatment stopping disease in 100% of mice – clinical score of 0, compared to development of several paralysis in 91% of untreated mice. The proposed work will build on these findings to test the hypotheses that assembly of self-antigen and regulatory immune signals generates tolerance in mouse models of MS and samples from human MS patients, test if this tolerance is myelin-specific, and investigate the mechanism and durability of efficacy. The specific aims are 1) characterize iPEM properties and screen in mouse cells and samples from the Baltimore VA’s MS patient cohort, 2) assess potency in a progressive mouse model of MS (EAE) and test if tolerance is myelin-specific, 3) elucidate the structural and functional changes in LNs, spleen, and the CNS that lead to tolerance, 4) test if tolerance is generalizable to other self-antigens using a relapsing-remitting model of MS (RR-EAE). VA support for this project could enable technology that creates more specific and effective treatments for MS or other autoimmune diseases that impact many Veterans.