IL-2/CD25: A Long-Acting Fusion Protein That Promotes Immune Tolerance by Selectively Targeting the IL-2 Receptor on Regulatory T Cells

Low-dose IL-2 represents an immunotherapy to selectively expand regulatory T cells (Tregs) to promote tolerance in patients with autoimmunity. In this article, we show that a fusion protein (FP) of mouse IL-2 and mouse IL-2Ra (CD25), joined by a noncleavable linker, has greater in vivo efficacy than rIL-2 at Treg expansion and control of autoimmunity. Biochemical and functional studies support a model in which IL-2 interacts with CD25 in the context of this FP in trans to form inactive head-to-tail dimers that slowly dissociate into an active monomer. In vitro, IL-2/CD25 has low sp. act. However, in vivo IL-2/CD25 is long lived to persistently and selectively stimulate Tregs. In female NOD mice, IL-2/CD25 administration increased Tregs within the pancreas and reduced the instance of spontaneous diabetes. Thus, IL-2/CD25 represents a distinct class of IL-2 FPs with the potential for clinical development for use in autoimmunity or other disorders of an overactive immune response. Overall design: Splenic murine Tregs mRNA profiles of IL-2/CD25 (FP) or control PBS injected mice were generated 72 hrs post injection by deep sequencing, in quadruplicate (FP) or triplicate (PBS), using NextSeq 500 with a High Output Kit 150-cycle flow cell (Illumina). Reads from RNA-seq were mapped to the Mus musculus genome GRCm38 using STAR (ver.2.5.0) aligner 44. Raw counts were generated on Ensembl gene (GENCODE M13) with featureCounts (ver.1.5.0) 45. Differential expressed genes in Tregs between the IL2/CD25 and PBS injected mice were identified using DESeq2 46, and determined according to threshold of false discovery rate (FDR) <0.05

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Ward NC, Yu A, Moro A, Ban Y, Chen X, Hsiung S, Keegan J, Arbanas JM, Loubeau M, Thankappan A, Yamniuk AP, Davis JH, Struthers M, Malek TR