Rationale: Systemic lupus erythematosus (SLE) is a multiorgan inflammatory disease that results from loss of immunological self-tolerance. Regulatory T cells (Tregs) are the “battlefield” controller of the immune system. Tregs recognize “self” such that when they are not working properly, the immune system attacks and destroys its own tissues. Defects in Tregs have been suggested to play a pathogenetic role in SLE. However, published work about deficient numbers and functions of Tregs in SLE are contradictory and the definitive role of Tregs in SLE remains unclear. Recent studies from my lab have identified a common druggable defect in SLE Treg function, diminished GRAIL expression leading to defective IL-2R signaling. The hypothesis to be tested is that the common defect in SLE patients regulatory T cells can be repaired by our protein drug conjugate that specifically targets small molecule drugs to the defective SLE Tregs to restore the IL-2R signaling defect generated by diminished GRAIL expression.

Focus Areas: Our proposal addresses two of the LRP Focus Areas: understanding the biological mechanisms of lupus disease as well as improving the quality of life for individuals with lupus.

Specific Aims: Proposed studies in Aim 1 are to develop a protein drug conjugate to correct the defect to restore SLE Treg function. Studies in Aim 2 are to develop a biomarker panel of monoclonal antibodies to identify the defect in cell signaling transduction in Tregs downstream of the IL-2 receptor (IL-2R) that results in defective SLE Treg function. Aim 3 is to study the ability of the human form of the protein drug conjugate we will develop in Aim 1 to correct the IL-2R signaling defect in SLE Tregs and see if it will block progression of nephritis in a mouse model of lupus. The final aim is somewhat complicated to understand but is simply inserting a gene (using a viral vector) into the SLE Tregs in tissue culture to see if it will correct GRAIL expression and thus the defect in the IL-2R signaling.

Applicability: The studies proposed in this application could lead to candidate protein drug conjugates to be developed for human use to treat lupus patients to block disease progression. Translation of these studies to human trials requires several steps if the concept we propose is correct. There needs to be drug development steps, including PK (where do the drug go once injected?) and Tox (are the protein drug conjugates toxic?). Good Manufacturing Production of the protein drug conjugates is another step to drug development. If successful, and with adequate support, proof of concept of therapeutic efficacy of a protein drug conjugate to restore function to Tregs in SLE could be obtained within several years.

Summary: The common defect in Treg function in patients with SLE my lab identified is a loss of inhibition of IL-2R desensitization. Simply put, when IL-2 binds its receptor on cells, it “sensitizes” or activates the receptor. Tregs in healthy people have a unique inbuilt system that delays (inhibits) the desensitization of their IL-2R, allowing extended activity through the IL-2Rb chain-associated pJAK1 that activates a transcription factor STAT5. After STAT5 is activated, it translocates into the nucleus where it transcribes genes relevant for Treg function. Prolonged nuclear localization of pSTAT5 for up to 4 hours is required to allow the Treg to express the genes required for Treg function. Premature loss of pSTAT5 expression due to defective inhibition of IL-2R desensitization leads to defective Treg function. We propose to develop a protein drug conjugate of an IL-2 fusion protein and a neddylation activating enzyme inhibitor or transduce “defective” SLE Tregs to express Otubain1-ARF1, to correct the defect in IL-2R signal transduction to restore function in SLE Tregs. These studies should allow us to develop a lead candidate to restore Treg function in patients with SLE that could lead to a paradigm shift in therapy of SLE, restoration of endogenous immune regulation. The development of novel therapeutic approaches to restore the symbiotic relationship between Tregs and autoreactive T-cells to restore normal immune regulation is an important goal for research in SLE.