PROJECT SUMMARY Multiple Sclerosis (MS) is a debilitating disease that occurs when the body’s immune system incorrectly recognizes myelin, the matrix that insulates neurons in the central nervous system (CNS) as foreign. Current treatments for MS aim to reduce the severity of disease, but do not treat the cause, and require continual, frequent treatments over the lifetime of the patient to maintain disease remission, though the disease ultimately will progress. Unfortunately, these existing therapy options are also non-specific – they cannot differentiate between myelin-specific inflammatory immune cells and other lymphocytes, leaving patients susceptible to opportunistic infections. Myelin-specific inflammatory cells are activated in lymph nodes (LNs), sites which coordinate immune cell interactions that control immune cell phenotypes. In the LNs, antigen presenting cells, including dendritic cells (DCs), present antigens – such as myelin in MS – to T and B cells. Depending on the signals present during this interaction, T cells can become inflammatory effector cells or regulatory cells (TREGS) that control the activity of inflammatory cells. During MS, these myelin-specific effector cells contribute to inflammation and neurodegeneration in the CNS. To overcome the limitations of current treatments, this proposal focuses on developing therapies that promote selective immune tolerance to myelin by inducing antigen-specific TREGS that can selectively control disease. To meet this goal, a direct LN injection technique will be used to deposit polymer particles co-loaded with myelin self-antigens and rapamycin, an immunomodulator, in LNs of mice induced with a relapsing-remitting model of MS. Studies have shown that the presence of Rapamycin, during the priming of a T cell can promote TREGS. Our lab has shown that a single injection of particles into LNs allows local programming of the LN microenvironment to promote TREGS, which permanently stopped and reversed disease-induced paralysis in a model of progressive MS. However, 85% of patients initially present with the relapsing-remitting form of MS, in which the immune system becomes reactive to different sections of myelin over time. This epitope spreading complicates treatment regimens, and therapies do not consistently work at all stages of disease. Thus, a relapsing-remitting model will allow for the study of epitope spreading, and how disease progresses when protection is conferred to an epitope at an earlier disease stage. Preliminary data shows that treating during the first wave of disease with a single iLN injection of particles co-loaded with rapamycin and the myelin epitope attacked during that wave can reverse disease and prevent relapse. This proposal will investigate how treatments at different stages of disease with different myelin epitopes alters disease progression and prevents relapse.