K-Channels in Lymphocyte Function and Autoimmunity

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Functional blockade or elimination of antigen-specific immune responses without impacting general immune function must be considered a holy grail in the quest to treat autoimmune disease. One approach to achieving this lofty goal is to suppress and/or eliminate effector memory (TEM) cells that have been implicated in the pathogenesis of many autoimmune diseases without affecting other immune cells. This proposal focuses on the voltage-gated Kv1.3 potassium channel in TEM cells as a therapeutic target for autoimmune diseases. Disease-associated autoreactive T cells in patients with multiple sclerosis (MS), type-1 diabetes mellitus (T1DM) and rheumatoid arthritis (RA) are TEM cells with elevated expression of Kv1.3 channels. We have developed highly specific inhibitors of Kv1.3 and these selectively suppress calcium signaling, cytokine production, proliferation, and in vivo migration of TEM cells without affecting other T cell subsets. In proof-of-concept studies, Kv1.3 blockers prevent and/or treat disease in rat models of MS, T1DM, RA, contact dermatitis, delayed type hypersensitivity (DTH) and bone resorption associated with periodontitis. These blockers have excellent safety profiles in animal models. They do not compromise the acute protective immune response to viral and bacterial pathogens. Specific Kv1.3 blockers, provide an exciting new therapeutic approach to mute autoreactive responses without compromising the protective immune response. The studies outlined in this proposal will lay the groundwork for clinical trials in patients with MS with ShK-186, our lead candidate. Aim 1 will define the mechanisms underlying ShK-186¿s therapeutic effect in chronic relapsing-remitting experimental autoimmune encephalomyelitis (CR-EAE) in DA rats, a model for human MS. We will test the hypothesis that ShK-186 eliminates disease-causing CNS autoantigen-specific TEM cells by a mechanism we term ¿death by neglect¿ while other immune cells, particularly disease-suppressing regulatory T cells, proliferate unabated because they are protected by the ShK-186-resistant KCa3.1 channel. Aim 2 will characterize the therapeutic dose, frequency and duration of ShK-186 treatment in CR-EAE to better predict human studies. In Aim 3 we will use patch-clamp recording and flow cytometry to determine whether Kv1.3high expression is a reliable biomarker for MS, and whether it will be useful for tracking Kv1.3 blocker therapy. A second goal of aim 3 is to study channel expression in T cells from Cynomolgus monkeys because this species is widely used for toxicological evaluation of human immune modulating therapies and is our non-human primate choice for IND-enabling toxicological studies. We will define the K-channel phenotype of cynomolgus monkey T cell subsets, and we will evaluate ShK-186¿s effectiveness in suppressing monkey TEM cell-proliferation.