IL-2: Change Structure Change Function.

In this issue of Immunity, Spangler et al. and Mitra et al. demonstrate how structural changes in the IL-2 molecule alter interactions with the IL-2 receptor, leading to differential cellular targeting and biochemical responses and selective immune consequences.

Engineering a Single-Agent Cytokine/Antibody Fusion That Selectively Expands Regulatory T Cells for Autoimmune Disease Therapy.

IL-2 has been used to treat diseases ranging from cancer to autoimmune disorders, but its concurrent immunostimulatory and immunosuppressive effects hinder efficacy. IL-2 orchestrates immune cell function through activation of a high-affinity heterotrimeric receptor (composed of IL-2Rα, IL-2Rß, and common γ [γc]). IL-2Rα, which is highly expressed on regulatory T (TReg) cells, regulates IL-2 sensitivity. Previous studies have shown that complexation of IL-2 with the JES6-1 Ab preferentially biases cytokine activity toward TReg cells through a unique mechanism whereby IL-2 is exchanged from the Ab to IL-2Rα. However, clinical adoption of a mixed Ab/cytokine complex regimen is limited by stoichiometry and stability concerns. In this study, through structure-guided design, we engineered a single agent fusion of the IL-2 cytokine and JES6-1 Ab that, despite being covalently linked, preserves IL-2 exchange, selectively stimulating TReg expansion and exhibiting superior disease control to the mixed IL-2/JES6-1 complex in a mouse colitis model. These studies provide an engineering blueprint for resolving a major barrier to the implementation of functionally similar IL-2/Ab complexes for treatment of human disease.

Revisiting IL-2: Biology and therapeutic prospects.

Interleukin-2 (IL-2), the first cytokine that was molecularly cloned, was shown to be a T cell growth factor essential for the proliferation of T cells and the generation of effector and memory cells. On the basis of this activity, the earliest therapeutic application of IL-2 was to boost immune responses in cancer patients. Therefore, it was a surprise that genetic deletion of the cytokine or its receptor led not only to the expected immune deficiency but also to systemic autoimmunity and lymphoproliferation. Subsequent studies established that IL-2 is essential for the maintenance of Foxp3+ regulatory T cells (Treg cells), and in its absence, there is a profound deficiency of Treg cells and resulting autoimmunity. We now know that IL-2 promotes the generation, survival, and functional activity of Treg cells and thus has dual and opposing functions: maintaining Treg cells to control immune responses and stimulating conventional T cells to promote immune responses. It is well documented that certain IL-2 conformations result in selective targeting of Treg cells by increasing reliance on CD25 binding while compromising CD122 binding. Recent therapeutic strategies have emerged to use IL-2, monoclonal antibodies to IL-2, or IL-2 variants to boost Treg cell numbers and function to treat autoimmune diseases while dealing with the continuing challenges to minimize the generation of effector and memory cells, natural killer cells, and other innate lymphoid populations.

A human anti-IL-2 antibody that potentiates regulatory T cells by a structure-based mechanism.

Interleukin-2 (IL-2) has been shown to suppress immune pathologies by preferentially expanding regulatory T cells (Tregs). However, this therapy has been limited by off-target complications due to pathogenic cell expansion. Recent efforts have been focused on developing a more selective IL-2. It is well documented that certain anti-mouse IL-2 antibodies induce conformational changes that result in selective targeting of Tregs. We report the generation of a fully human anti-IL-2 antibody, F5111.2, that stabilizes IL-2 in a conformation that results in the preferential STAT5 phosphorylation of Tregs in vitro and selective expansion of Tregs in vivo. When complexed with human IL-2, F5111.2 induced remission of type 1 diabetes in the NOD mouse model, reduced disease severity in a model of experimental autoimmune encephalomyelitis and protected mice against xenogeneic graft-versus-host disease. These results suggest that IL-2-F5111.2 may provide an immunotherapy to treat autoimmune diseases and graft-versus-host disease.

Selective targeting of engineered T cells using orthogonal IL-2 cytokine-receptor complexes.

Interleukin-2 (IL-2) is a cytokine required for effector T cell expansion, survival, and function, especially for engineered T cells in adoptive cell immunotherapy, but its pleiotropy leads to simultaneous stimulation and suppression of immune responses as well as systemic toxicity, limiting its therapeutic use. We engineered IL-2 cytokine-receptor orthogonal (ortho) pairs that interact with one another, transmitting native IL-2 signals, but do not interact with their natural cytokine and receptor counterparts. Introduction of orthoIL-2Rß into T cells enabled the selective cellular targeting of orthoIL-2 to engineered CD4+ and CD8+ T cells in vitro and in vivo, with limited off-target effects and negligible toxicity. OrthoIL-2 pairs were efficacious in a preclinical mouse cancer model of adoptive cell therapy and may therefore represent a synthetic approach to achieving selective potentiation of engineered cells.

The therapeutic potential of regulatory T cells for the treatment of autoimmune disease.

INTRODUCTION: Immune tolerance remains the holy grail of therapeutic immunology in the fields of organ and tissue transplant rejection, autoimmune diseases, and allergy and asthma. We have learned that FoxP3(+)CD4(+) regulatory T cells play a vital role in both the induction and maintenance of self-tolerance. AREAS COVERED: In this opinion piece, we highlight regulatory T cells (Treg) cell biology and novel immune treatments to take advantage of these cells as potent therapeutics. We discuss the potential to utilize Treg and Treg-friendly therapies to replace current general immunosuppressives and induce tolerance as a path towards a drug-free existence without associated toxicities. EXPERT OPINION: Finally, we opine on the fact that biomedicine sits on the cusp of a new revolution: the use of human cells as versatile therapeutic engines. We highlight the challenges and opportunities associated with the development of a foundational cellular engineering science that provides a systematic framework for safely and predictably regulating cellular behaviors. Although Treg therapy has become a legitimate clinical treatment, development of the therapy will require a better understanding of the underlying Treg biology, manufacturing advances to promote cost effectiveness and combinations with other drugs to alter the pathogenicity/regulatory balance.

Chemerin regulates NK cell accumulation and endothelial cell morphogenesis in the decidua during early pregnancy.

CONTEXT: Although decidual natural killer (NK) cell accumulation and vascular remodeling are critical steps to ensure successful pregnancy, the molecular mechanisms controlling these events are poorly defined. OBJECTIVE: Herein we analyzed whether chemerin, a recently identified chemoattractant involved in many pathophysiological processes, could be expressed in the uterine compartment and could regulate events relevant for the good outcome of pregnancy. DESIGN: Chemerin expression in human primary culture of stromal (ST) cells, extravillous trophoblast cells, and decidual endothelial cells (DEC) was analyzed by RT-PCR, ELISA, and Western blot. Migration through ST or DEC of peripheral blood and decidual (d) NK cells from pregnant women was performed using a transwell assay. A DEC capillary-like tube formation assay was used to evaluate endothelial morphogenesis. RESULTS: Chemerin is differentially expressed by decidual cells during early pregnancy being present at high levels in ST and extravillous trophoblast cells but not in DEC. Notably, ST cells from pregnant women exhibit and release higher levels of chemerin as compared with ST cells from menopausal or fertile nonpregnant women. Chemerin can support peripheral blood NK cell migration through both DEC and ST cells. Although dNK cells exhibit lower chemerin receptor (CMKLR1) expression than their blood counterpart, CMKLR1 engagement on dNK cells resulted in both ERK activation and migration through decidual ST cells. Interestingly, DEC also express CMKLR1 and undergo ERK activation and capillary-like tube structure formation upon exposure to chemerin. CONCLUSIONS: Our data indicate that chemerin is up-regulated during decidualization and might contribute to NK cell accumulation and vascular remodeling during early pregnancy.