Regulating Interleukin-2 activity with engineered receptor signaling clamps

Interleukin-2 (IL-2) is a pleiotropic cytokine that regulates lymphocyte function by signaling through heterodimerization of the IL-2Rß and ?c receptor subunits. Previously, we engineered an IL-2 “superkine” (H9) with enhanced affinity for IL-2Rß. Here, we describe next-generation IL-2 variants that function as “receptor signaling clamps.” They retain high-affinity for IL-2Rß, thereby inhibiting binding of endogenous IL-2, but their engagement of ?c is weakened, thereby attenuating IL-2Rß-?c heterodimerization. These IL-2 analogues act as partial agonists and can differentially affect lymphocytes poised at distinct activation thresholds. Moreover, one of these variants potently antagonized IL-2 and IL-15 signaling and function better than blocking antibodies against IL-2Ra or IL-2Rß. Furthermore, this mutein prolonged survival in a model of graft versus host disease and blocked spontaneous proliferation of smoldering adult T-cell leukemia (ATL) T cells ex vivo. This receptor-clamping approach may be a general mechanism-based strategy for engineering cytokine partial agonists for therapeutic immunomodulation. Overall design: Genome-wide transcription factors binding of STAT5 and mRNA-Sequencing of gene expression profiles in human pre-activated CD8+ T cells.