Guiding innate signaling in skin with microneedle arrays to promote durable antigen-specific tolerance during autoimmunity - During autoimmunity, the body incorrectly identifies “self” molecules as foreign. For example, during multiple sclerosis (MS) attack of myelin in the central nervous system (CNS) leads to neurodegeneration, while during type 1 diabetes (T1D) attack of the pancreas leads to dysregulation of blood glucose. Existing therapies for autoimmunity span immunosuppressants and newer monoclonal antibodies, but even the latter do not distinguish between healthy and self- reactive cells. Thus, while beneficial, existing therapies are not curative, cause immunocompromising side effects, and require life-long compliance. These limitations have motivated efforts to control autoimmunity with vaccine-like specificity, without hindering the normal functions of the immune system. One such antigen-specific tolerance strategy being studied pre-clinically and in human trials is co-delivery of self-peptides and tolerizing immune signals to promote populations, such as regulatory T cells (TREGs), that selectively combat disease. Interestingly, a set of molecules newly-associated with autoimmune disease are toll-like receptors (TLRs). In healthy individuals, TLRs detect pathogen-associated patterns to mobilize innate immunity. However, TLRs - such as TLR9 - are elevated in patients with MS, T1D, and other autoimmune diseases, as well as in pre-clinical models. In the latter case, suppressing TLR9 signaling reduces inflammation, while promoting TREGs and improving disease. Strategies that regulate excess innate signaling could guide T cell differentiating as self-antigens are presented in lymph nodes (LNs) – for example, co-delivery of regulatory cues – to generate large populations of antigen-specific TREGs that selectively stop pathogenic cells without broad suppression. New studies also reveal TREGs can adopt memory functions to maintain tolerance, and in appropriate tissue niches, cause transdifferentiation of inflammatory TH17 cells into TREG. Lymph nodes (LNs) are key tissues that control these processes; polarization toward either inflammatory T cells (e.g., TH17) or TREGs is directed in part by directing dynamic stromal organization to promote and regulate cell interactions. Upstream in the skin, a specialized immune niche exists through concentration of antigen presenting cells (APCs) that also exhibit high levels of TLRs and other innate signaling receptors. Thus, skin is of great interest as a site to target for induction of tolerance. We propose using 3D printed microneedle arrays (MNA) to load self- antigens and regulatory TLR ligands at high densities for efficient delivery to the skin niche. MNAs have been studied for vaccines against pathogens, and recently for tolerance against allergens (foreign antigens), but remain untapped in autoimmune disease as technologies to drive antigen-specific tolerance against self-antigens. We have shown these MNAs arrays durably stop or reverse disease in pre-clinical models of MS: EAE/RR-EAE. We will use this interdisciplinary approach to understand how locally modulating innate signaling in the skin conditions APCs downstream as they migrate and present antigen in LNs, and ultimately, how these changes induce and maintain self-antigen specific TREG for selective, but systemic, long-lasting tolerance. The aims are 1) Show MNAs bias innate (TLR) signaling in skin and skin-resident APCs toward regulation, 2) Define MNA-driven structural & functional changes associated with tolerance in LNs and the CNS, 3) Ascertain the durability of efficacy and maintenance of functional tolerance during EAE/RR-EAE.
