Leveraging Biomaterial Properties to Reprogram Immune Function in Autoimmunity

Abstract

Autoimmune diseases occur when immune cells incorrectly identify and attack the body’s tissues as foreign. In Multiple Sclerosis (MS), the immune system targets myelin, the protective layer that insulates nerves. Current MS therapies reduce disease severity without treating the cause, requiring frequent treatments to slow disease progression. Further, existing therapies cannot differentiate between dysfunctional myelin-reactive inflammatory cells and normal lymphocytes, leaving patients vulnerable to infection. To overcome these limitations, this dissertation investigated biodegradable polymeric microparticles (MPs) co-loaded with myelin peptides and rapamycin, an immunomodulatory signal. Directly injecting these tolerogenic MPs into key immune tissues (e.g. lymph nodes, LNs), induces myelin-specific regulatory immune cells that selectively control myelin-specific inflammation. This work aimed to advance pre-clinical studies and motivate clinical research in two ways: investigating the systemic impact of intra-LN tolerogenic MPs in two MS models, and enhancing MP stability using Chemistry, Manufacturing, and Controls (CMC) considerations.

This work showed that across both progressive and relapsing-remitting disease, one tolerogenic intra-LN treatment promoted long-lasting improvements in disease-induced paralysis. Tolerogenic MPs delivered prior to symptom onset promoted tolerance and protected against disease. Treatment at peak disease reversed paralysis and prevented relapse, while treatment during relapse limited disease progression. Strikingly, mice vaccinated against a foreign protein on the same day as intra-LN treatment generated protein-specific T cells and antibodies at similar levels to healthy vaccinated mice, while simultaneously exhibiting significantly reduced paralysis – highlighting the myelin-specific nature of this therapy.

While the low dosage requirements of these studies allowed for on-demand preparation, clinical translation requires investigation into manufacturing, preservation, storage, and stability of this immunotherapy. Thus, this dissertation also tested the impact of lyophilization (freeze-drying) and excipients (stabilizing molecules) on MP stability after storage. Lyophilization with low concentrations of excipients significantly improved MP stability and formulation recovery after reconstitution. Storage for 5 months at room temperature did not negatively impact cargo loading, MP size, or biofunctionality. MP formulations with excipients could deactivate inflammatory signaling and restrict myelin-specific immune cell proliferation as well as formulations without excipients.

Together, these studies motivate the development of intra-LN delivery of tolerogenic MPs as a potential MS immunotherapy for clinical translation.