Small Molecule Modification of the IL-2 Receptor: Implications for Therapy in Type 1 Diabetes

Small Molecule Modification of the IL-2 Receptor: Implications for Therapy in Type 1 Diabetes Multiple abnormalities in the Multiple abnormalities in the interleukin 2 (IL-2) signaling pathway have been associated with the pathogenesis of type 1 diabetes (T1D) in both NOD mice and humans. IL-2 has diverse immune functions: it maintains tolerance through regulatory T cell (Treg) populations, yet it also influences effector T cell proliferation and activation induced cell death (AICD). Reduced IL-2 responses in T1D thus fail to support proper immunoregulation. We sought to increase IL-2 signaling by targeting the IL-2 receptor complex with small drug-compatible compounds.[italic] In silico [/italic]affinity binding analysis was used to identify compounds capable of interacting with the receptor. 240 lead compounds with the highest affinity scores were tested at 10 uM versus vehicle (DMSO) treatment on stimulated (soluble anti-CD3/CD28) human peripheral blood mononuclear cells (PBMC) from healthy controls. 16 compounds were identified that repeatedly caused a significant (p[lt]0.05) change in proliferation and soluble CD25 (sCD25) production. These were subsequently tested for their ability to modulate purified human CD4+ T cell responses to stimulation with microbeads coated with anti-CD3/CD28. Proliferation of responding T cells was assessed by CFSE dilution, along with Treg phenotypic markers and measurements of AICD. One compound in particular was identified that potently prevented division of CD4[sup]+[/sup] T cells (n=5, p[lt]0.01). Cultured, treated cells displayed increased levels of active Caspase 3 in cell lysates suggesting AICD. The mechanism for this altered cell division did not appear to be due to nonspecific cytotoxicity, as cells produced similar levels of sCD25. Cells cultured for 96 h in the presence of the compound displayed increased frequencies of cells expressing Treg markers including glucocorticoid-induced tumor necrosis factor receptor (GITR) (n=4, p[lt]0.01), as well as coexpression of the natural Treg markers FOXP3 and Helios (n=5, p[lt]0.01). In sum, a rational drug design approach identified target compounds capable of augmenting the IL-2 signaling axis, forming a potential treatment for T1D either by enhancing the suppressive capacity of Tregs, or driving effector cells toward AICD. MAIGAN A. HULME, CLIVE H. WASSERFALL, TODD M. BRUSKO, MICHAEL J. HALLER, DESMOND A. SCHATZ, DAVID A. OSTROV, MARK A. ATKINSON 1460-P Gainesville, FL Immunology