Publications by authors named "Erwan Mortier"

26 Publications

  • Page 1 of 1

Interleukin-15 and cancer: some solved and many unsolved questions.

J Immunother Cancer 2020 11;8(2)

Immunology Area, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy

Soluble interleukin (IL)-15 exists under two forms: as monomer (sIL-15) or as heterodimeric complex in association with sIL-15Rα (sIL-15/IL-15Rα). Both forms have been successfully tested in experimental tumor murine models and are currently undergoing investigation in phase I/II clinical trials. Despite more than 20 years research on IL-15, some controversial issues remain to be addressed. A first point concerns the detection of the sIL-15/IL-15Rα in plasma of healthy donors or patients with cancer and its biological significance. The second and third unsolved question regards the protumorigenic role of the IL-15/IL-15Rα complex in human cancer and the detrimental immunological consequences associated to prolonged exposure of natural killer (NK) cells to both forms of soluble IL-15, respectively. Data suggest that in vivo prolonged or repeated exposure to monomeric sIL-15 or the soluble complex may lead to NK hypo-responsiveness through the expansion of the CD8/CD44 T cell subset that would suppress NK cell functions. In vitro experiments indicate that soluble complex and monomeric IL-15 may cause NK hyporesponsiveness through a direct effect caused by their prolonged stimulation, suggesting that this mechanism could also be effective in vivo. Therefore, a better knowledge of IL-15 and a more appropriate use of both its soluble forms, in terms of concentrations and time of exposure, are essential in order to improve their therapeutic use. In cancer, the overproduction of sIL-15/IL-15Rα could represent a novel mechanism of immune escape. The soluble complex may act as a decoy cytokine unable to efficiently foster NK cells, or could induce NK hyporesponsiveness through an excessive and prolonged stimulation depending on the type of IL-15Rα isoforms associated. All these unsolved questions are not merely limited to the knowledge of IL-15 pathophysiology, but are crucial also for the therapeutic use of this cytokine. Therefore, in this review, we will discuss key unanswered issues on the heterogeneity and biological significance of IL-15 isoforms, analyzing both their cancer-related biological functions and their therapeutic implications.
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http://dx.doi.org/10.1136/jitc-2020-001428DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7674108PMC
November 2020

Editorial: Modulating Cytokines as Treatment for Autoimmune Diseases and Cancer.

Front Immunol 2020 15;11:608636. Epub 2020 Oct 15.

University Hospital Erlangen, University Erlangen-Nürnberg, Erlangen, Germany.

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http://dx.doi.org/10.3389/fimmu.2020.608636DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7593236PMC
October 2020

IL-15Rα membrane anchorage in either or is required for stabilization of IL-15 and optimal signaling.

J Cell Sci 2019 12 5;133(5). Epub 2019 Dec 5.

CRCINA, CNRS, Inserm, University of Angers, University of Nantes, Nantes, France

Interleukin (IL)-15 plays an important role in the communication between immune cells. It delivers its signal through different modes involving three receptor chains: IL-15Rα, IL-2Rβ and IL-2Rγc. The combination of the different chains result in the formation of IL-15Rα/IL-2Rβ/γc trimeric or IL-2Rβ/γc dimeric receptors. In this study, we have investigated the role of the IL-15Rα chain in stabilizing the cytokine in the IL-2Rβ/γc dimeric receptor. By analyzing the key amino acid residues of IL-15 facing IL-2Rβ, we provide evidence of differential interfaces in the presence or in the absence of membrane-anchored IL-15Rα. Moreover, we found that the anchorage of IL-15Rα to the cell surface regardless its mode of presentation - i.e. or - is crucial for complete signaling. These observations show how the cells can finely modulate the intensity of cytokine signaling through the quality and the level of expression of the receptor chains.
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http://dx.doi.org/10.1242/jcs.236802DOI Listing
December 2019

NK Cell Hyporesponsiveness: More Is Not Always Better.

Int J Mol Sci 2019 Sep 12;20(18). Epub 2019 Sep 12.

CRCINA, CNRS, Inserm, University of Nantes, F-44200 Nantes, France.

Natural Killer (NK) cells are a type of cytotoxic lymphocytes that play an important role in the innate immune system. They are of particular interest for their role in elimination of intracellular pathogens, viral infection and tumor cells. As such, numerous strategies are being investigated in order to potentiate their functions. One of these techniques aims at promoting the function of their activating receptors. However, different observations have revealed that providing activation signals could actually be counterproductive and lead to NK cells' hyporesponsiveness. This phenomenon can occur during the NK cell education process, under pathological conditions, but also after treatment with different agents, including cytokines, that are promising tools to boost NK cell function. In this review, we aim to highlight the different circumstances where NK cells become hyporesponsive and the methods that could be used to restore their functionality.
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http://dx.doi.org/10.3390/ijms20184514DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6770168PMC
September 2019

Mechanistic and Structural Insights on the IL-15 System through Molecular Dynamics Simulations.

Molecules 2019 Sep 6;24(18). Epub 2019 Sep 6.

Université de Nantes, CEISAM UMR 6230, UFR des Sciences et des Techniques, 2 rue de la Houssinière, BP 92208, F-44000 Nantes, France.

Interleukin 15 (IL-15), a four-helix bundle cytokine, is involved in a plethora of different cellular functions and, particularly, plays a key role in the development and activation of immune responses. IL-15 forms receptor complexes by binding with IL-2Rβ- and common γ(γc)-signaling subunits, which are shared with other members of the cytokines family (IL-2 for IL-2Rβ- and all other γc- cytokines for γc). The specificity of IL-15 is brought by the non-signaling α-subunit, IL-15Rα. Here we present the results of molecular dynamics simulations carried out on four relevant forms of IL-15: its monomer, IL-15 interacting individually with IL-15Rα (IL-15/IL-15Rα), with IL-2Rβ/γc subunits (IL-15/IL-2Rβ/γc) or with its three receptors simultaneously (IL-15/IL-15Rα/IL-2Rβ/γc). Through the analyses of the various trajectories, new insights on the structural features of the interfaces are highlighted, according to the considered form. The comparison of the results with the experimental data, available from X-ray crystallography, allows, in particular, the rationalization of the importance of IL-15 key residues (e.g. Asp8, Lys10, Glu64). Furthermore, the pivotal role of water molecules in the stabilization of the various protein-protein interfaces and their H-bonds networks are underlined for each of the considered complexes.
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http://dx.doi.org/10.3390/molecules24183261DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6767322PMC
September 2019

Emergence of NK Cell Hyporesponsiveness after Two IL-15 Stimulation Cycles.

J Immunol 2018 07 30;201(2):493-506. Epub 2018 May 30.

Centre de Recherche en Cancérologie et Immunologie Nantes-Angers, CNRS, INSERM, Université de Nantes, 44007 Nantes, France; and

IL-15 is a cytokine playing a crucial role in the function of immune cells, including NK and CD8 T cells. In this study, we demonstrated that in vivo, in mice, IL-15-prestimulated NK cells were no longer able to respond to a second cycle of IL-15 stimulation. This was illustrated by defects in cell maturation, proliferation, and activation, seemingly linked to the environment surrounding NK cells but not related to the presence of CD4 regulatory T cells, TGF-β, or IL-10. Moreover, NK cells from immunodeficient mice could respond to two cycles of IL-15 stimulation, whereas an adoptive transfer of CD44CD8 cells impaired their responsiveness to the second cycle. Conversely, in immunocompetent mice, NK cell responsiveness to a second IL-15 stimulation was restored by the depletion of CD8 cells. These biological findings refine our understanding of the complex mode of action of NK cells in vivo, and they should be taken into consideration for IL-15-based therapy.
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http://dx.doi.org/10.4049/jimmunol.1800086DOI Listing
July 2018

Discovery of a Small-Molecule Inhibitor of Interleukin 15: Pharmacophore-Based Virtual Screening and Hit Optimization.

J Med Chem 2017 07 18;60(14):6249-6272. Epub 2017 Jul 18.

CEISAM, CNRS, Faculty of Sciences, University of Nantes , Nantes 44322, France.

Interleukin (IL)-15 is a pleiotropic cytokine, which is structurally close to IL-2 and shares with it the IL-2 β and γ receptor (R) subunits. By promoting the activation and proliferation of NK, NK-T, and CD8+ T cells, IL-15 plays important roles in innate and adaptative immunity. Moreover, the association of high levels of IL-15 expression with inflammatory and autoimmune diseases has led to the development of various antagonistic approaches targeting IL-15. This study is an original approach aimed at discovering small-molecule inhibitors impeding IL-15/IL-15R interaction. A pharmacophore and docking-based virtual screening of compound libraries led to the selection of 240 high-scoring compounds, 36 of which were found to bind IL-15, to inhibit the binding of IL-15 to the IL-2Rβ chain or the proliferation of IL-15-dependent cells or both. One of them was selected as a hit and optimized by a structure-activity relationship approach, leading to the first small-molecule IL-15 inhibitor with sub-micromolar activity.
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http://dx.doi.org/10.1021/acs.jmedchem.7b00485DOI Listing
July 2017

Cutting Edge: Differential Fine-Tuning of IL-2- and IL-15-Dependent Functions by Targeting Their Common IL-2/15Rβ/γc Receptor.

J Immunol 2017 06 15;198(12):4563-4568. Epub 2017 May 15.

Centre de Recherche en Cancérologie et Immunologie Nantes-Angers, CNRS, Inserm, Université de Nantes, Nantes 44007, France;

Interleukin 2 and IL-15 are two closely related cytokines, displaying important functions in the immune system. They share the heterodimeric CD122/CD132 receptor to deliver their signals within target cells. Their specificity of action is conferred by their α receptor chains, IL-2Rα and IL-15Rα. By combining an increased affinity for CD122 and an impaired recruitment of CD132, we have generated an original molecule named IL-2Rβ/γ (CD122/CD132) inhibitor (BiG), targeting the CD122/CD132 receptor. BiG efficiently inhibited IL-15- and IL-2-dependent functions of primary cells, including CD8 T and NK cells, in vitro and in vivo. We also report a differential dynamic of action of these cytokines by highlighting a major role played by the IL-2Rα receptor. Interestingly, due to the presence of IL-2Rα, BiG had no impact on IL-2-dependent regulatory T cell proliferation. Thus, by acting as a fine switch in the immune system, BiG emphasizes the differential roles of these two cytokines.
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http://dx.doi.org/10.4049/jimmunol.1700046DOI Listing
June 2017

[Interleukin 2 revival: a revisited model and new therapeutic applications].

Med Sci (Paris) 2016 Jun-Jul;32(6-7):612-8. Epub 2016 Jul 12.

Centre de recherche en cancérologie Nantes-Angers (CRCNA), UMR Inserm 892 - CNRS 6299, Université de Nantes, IRS-UN, 8, quai Moncousu, BP70721, F-44007, Nantes, France.

Interleukin-2, a cytokine identified as T-cell growth factor, has long been regarded as central to the development and effector activities of immune responses. Several gene knockout mouse studies and observations in humans, however, have undermined that vision, and the discovery of regulatory T cells showed that IL-2, in contrast to the accepted dogma, has the essential function of promoting (1) homeostasis and (2) the function of these T regulator cells the which, limit the action of the effector cells, in particular to prevent the autoimmune reaction drifts. This new paradigm has major implications on the use of IL-2 in therapy, and creates new strategies to manipulate the Teffectors/Tregulators balance.
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http://dx.doi.org/10.1051/medsci/20163206025DOI Listing
July 2017

Syndecan-1 regulates the biological activities of interleukin-34.

Biochim Biophys Acta 2015 May 4;1853(5):1010-21. Epub 2015 Feb 4.

INSERM, UMR 957, Equipe Ligue 2012, Nantes F-44035, France; Université de Nantes, Laboratoire de Physiopathologie de la Résorption Osseuse et Thérapie des Tumeurs Osseuses Primitives, France; Centre hospitalier universitaire de Nantes, France. Electronic address:

IL-34 is a challenging cytokine sharing functional similarities with M-CSF through M-CSFR activation. It also plays a singular role that has recently been explained in the brain, through a binding to the receptor protein tyrosine phosphatase RPTPβ/ζ. The aim of this paper was to look for alternative binding of IL-34 on other cell types. Myeloid cells (HL-60, U-937, THP-1) were used as cells intrinsically expressing M-CSFR, and M-CSFR was expressed in TF-1 and HEK293 cells. IL-34 binding was studied by Scatchard and binding inhibition assays, using 125I-radiolabelled cytokines, and surface plasmon resonance. M-CSFR activation was analysed by Western blot after glycosaminoglycans abrasion, syndecan-1 overexpression or repression and addition of a blocking anti-syndecan antibody. M-CSF and IL-34 induced different patterns of M-CSFR phosphorylations, suggesting the existence of alternative binding for IL-34. Binding experiments and chondroitinase treatment confirmed low affinity binding to chondroitin sulphate chains on cells lacking both M-CSFR and RPTPβ/ζ. Amongst the proteoglycans with chondroitin sulphate chains, syndecan-1 was able to modulate the IL-34-induced M-CSFR signalling pathways. Interestingly, IL-34 induced the migration of syndecan-1 expressing cells. Indeed, IL-34 significantly increased the migration of THP-1 and M2a macrophages that was inhibited by addition of a blocking anti-syndecan-1 antibody. This paper provides evidence of alternative binding of IL-34 to chondroitin sulphates and syndecan-1 at the cell surface that modulates M-CSFR activation. In addition, IL-34-induced myeloid cell migration is a syndecan-1 dependent mechanism.
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http://dx.doi.org/10.1016/j.bbamcr.2015.01.023DOI Listing
May 2015

[Cut the cord, you're ready to set off on your own!].

Med Sci (Paris) 2014 Oct 14;30(10):836-8. Epub 2014 Oct 14.

Centre de recherche en cancérologie, Inserm UMR 892, CNRS 6299, université de Nantes, 8, quai Moncousu, BP70721, F-44007, Nantes, France - Centre hospitalier universitaire, F-44093, Nantes, France.

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http://dx.doi.org/10.1051/medsci/20143010006DOI Listing
October 2014

IL-15.IL-15Rα complex shedding following trans-presentation is essential for the survival of IL-15 responding NK and T cells.

Proc Natl Acad Sci U S A 2014 Jun 27;111(23):8565-70. Epub 2014 May 27.

Cancer Research Center Nantes-Angers, Inserm Unité Mixte de Recherche 892, Centre National de la Recherche Scientifique 6299, University of Nantes, 44007 Nantes, France;

Interleukin (IL)-15 and its specific receptor chain, IL-15Rα, support the development of various effector cells, including NK and CD8 T cells via a mechanism called trans-presentation. Whereas the dynamic of trans-presentation has been shown to involve the recycling of IL-15Rα by presenting cells, the way responding cells integrate, or take advantage of this process has not been evaluated yet. To address this question, we set up a trans-presentation model using a membrane-bound IL-15.IL-15Rα fusion protein, and found that IL-15 is detectable within responding cells following IL-15 trans-presentation. The role of the proteolytic cleavage of IL-15Rα in this process was investigated by generating an uncleavable form of IL-15Rα. We showed that IL-15 entry into responding cells necessitates the cleavage of IL-15.IL-15Rα complex from the surface of IL-15 presenting cells, and observed that IL-15Rα cleavage is associated with a decrease of the duration of Stat5 signaling. Once separated from presenting cells, responding cells are able to recycle IL-15.IL-15Rα complexes via intracellular compartments, for residual proliferation in a time-limited manner. These studies define an unprecedented cytokine pathway in which the IL-15.IL-15Rα complex cleaved from presenting cells allows responding cells to internalize, store and use IL-15.IL-15Rα complex for their own proliferation and survival.
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http://dx.doi.org/10.1073/pnas.1405514111DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4060713PMC
June 2014

Regulation of CD4(+)NKG2D(+) Th1 cells in patients with metastatic melanoma treated with sorafenib: role of IL-15Rα and NKG2D triggering.

Cancer Res 2014 Jan 6;74(1):68-80. Epub 2013 Nov 6.

Authors' Affiliations: Cancer Institute Gustave Roussy; Departments of Epidemiology and Statistics and Dermatology; Stabilité génétique et oncogenèse UMR 8200; Clinical Oncology, Melanoma Branch, Cancer Institute Gustave Roussy; Department of BioPathology, Translational Research Laboratory and Biobank, Institute Gustave Roussy; Institut National de la Santé et de la Recherche Medicale (INSERM), U1015; Center of Clinical Investigations CBT507, Biotherapy, Villejuif; INSERM U1102, Institut de Cancérologie de l'Ouest, Saint Herblain; INSERM, U892, Institut de Recherche Thérapeutique, Nantes; INSERM, U1016, Saint Vincent de Paul Hospital; INSERM U1016, CNRS UMR8104, Cochin Institute; Faculté Paris Sud-Université Paris XI, Paris, France; and IRCCS San Matteo University Hospital Foundation, Pavia, Italy.

Beyond cancer-cell intrinsic factors, the immune status of the host has a prognostic impact on patients with cancer and influences the effects of conventional chemotherapies. Metastatic melanoma is intrinsically immunogenic, thereby facilitating the search for immune biomarkers of clinical responses to cytotoxic agents. Here, we show that a multi-tyrosine kinase inhibitor, sorafenib, upregulates interleukin (IL)-15Rα in vitro and in vivo in patients with melanoma, and in conjunction with natural killer (NK) group 2D (NKG2D) ligands, contributes to the Th1 polarization and accumulation of peripheral CD4(+)NKG2D(+) T cells. Hence, the increase of blood CD4(+)NKG2D(+) T cells after two cycles of sorafenib (combined with temozolomide) was associated with prolonged survival in a prospective phase I/II trial enrolling 63 patients with metastatic melanoma who did not receive vemurafenib nor immune checkpoint-blocking antibodies. In contrast, in metastatic melanoma patients treated with classical treatment modalities, this CD4(+)NKG2D(+) subset failed to correlate with prognosis. These findings indicate that sorafenib may be used as an "adjuvant" molecule capable of inducing or restoring IL-15Rα/IL-15 in tumors expressing MHC class I-related chain A/B (MICA/B) and on circulating monocytes of responding patients, hereby contributing to the bioactivity of NKG2D(+) Th1 cells.
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http://dx.doi.org/10.1158/0008-5472.CAN-13-1186DOI Listing
January 2014

Interleukin-15 plays a central role in human kidney physiology and cancer through the γc signaling pathway.

PLoS One 2012 21;7(2):e31624. Epub 2012 Feb 21.

INSERM UMR 1014, Hôpital Paul Brousse, Villejuif, France.

The ability of Interleukin-15 (IL-15) to activate many immune antitumor mechanisms renders the cytokine a good candidate for the therapy of solid tumors, particularly renal cell carcinoma. Although IL-15 is being currently used in clinical trials, the function of the cytokine on kidney's components has not been extensively studied; we thus investigated the role of IL-15 on normal and tumor renal epithelial cells. Herein, we analyzed the expression and the biological functions of IL-15 in normal renal proximal tubuli (RPTEC) and in their neoplastic counterparts, the renal clear cell carcinomas (RCC). This study shows that RPTEC express a functional heterotrimeric IL-15Rαβγc complex whose stimulation with physiologic concentrations of rhIL-15 is sufficient to inhibit epithelial mesenchymal transition (EMT) commitment preserving E-cadherin expression. Indeed, IL-15 is not only a survival factor for epithelial cells, but it can also preserve the renal epithelial phenotype through the γc-signaling pathway, demonstrating that the cytokine possess a wide range of action in epithelial homeostasis. In contrast, in RCC in vitro and in vivo studies reveal a defect in the expression of γc-receptor and JAK3 associated kinase, which strongly impacts IL-15 signaling. Indeed, in the absence of the γc/JAK3 couple we demonstrate the assembly of an unprecedented functional high affinity IL-15Rαβ heterodimer, that in response to physiologic concentrations of IL-15, triggers an unbalanced signal causing the down-regulation of the tumor suppressor gene E-cadherin, favoring RCC EMT process. Remarkably, the rescue of IL-15/γc-dependent signaling (STAT5), by co-transfecting γc and JAK3 in RCC, inhibits EMT reversion. In conclusion, these data highlight the central role of IL-15 and γc-receptor signaling in renal homeostasis through the control of E-cadherin expression and preservation of epithelial phenotype both in RPTEC (up-regulation) and RCC (down-regulation).
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0031624PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3283658PMC
June 2012

Different dynamics of IL-15R activation following IL-15 cis- or trans-presentation.

Eur Cytokine Netw 2010 Dec 16;21(4):297-307. Epub 2010 Nov 16.

INSERM UMR 892, Centre de Recherche en Cancérologie Nantes/Angers, Groupe de Recherche Cytokines et Récepteurs en Immuno-Cancérologie, Nantes, France.

Interleukin (IL)-15 is a cytokine critical for the homeostasis and the function of NK cells, NK-T cells, and memory CD8+ T cells. IL-15 signals are delivered through the IL-15Rβ and the common γ (γ(c)) receptor chains. The third receptor chain, IL-15Rα, confers specificity and high affinity for the cytokine. While IL-15 can activate with high affinity the trimeric receptor expressed by a target cell (cis-presentation), IL-15Rα is also known to trans-present IL-15 with high affinity to target cells expressing the IL-15Rβ/γ(c) complex. In order to compare the IL-15 cis- and trans-presentation processes, and using a T cell line expressing both IL-15Rα/β/γ(c) and IL-15Rβ/γ(c), we analyzed cell surface receptor chain down-modulation, cytokine internalization and signaling responses induced either with IL-15 (cis-presentation) or with RLI, a protein resulting from fusion between IL-15 and an extended IL-15Rα sushi domain, that mimics trans-presentation. Whereas IL-15 bound with high affinity to IL-15Rα/β/γ(c), RLI bound with a similar high affinity to IL-15Rβ/γ(c). The kinetics of cell surface IL-15R down-modulation were slower following RLI treatment than after IL-15 treatment, as were the kinetics of RLI internalization, which was slower than that of IL-15. IL-15 and RLI dose-dependently induced the activation of similar signaling pathways. However, the kinetics and duration of these activations were markedly different, RLI-induced signaling, being slower, but more prolonged than that induced by IL-15, although the final proliferative responses at 48 h were similar. These findings collectively indicate that IL-15 cis- and trans-presentation mechanisms lead to different dynamics of receptor activation and signal transduction, with cis-presentation inducing fast and transient responses, and trans-presentation inducing slower, more persistent ones. They provide clues for a better understanding of how IL-15 action is controlled, and how it plays a key role in the coordination between innate and adaptative immunity.
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http://dx.doi.org/10.1684/ecn.2010.0207DOI Listing
December 2010

Interleukin-15 and its soluble receptor mediate the response to infliximab in patients with Crohn's disease.

Gastroenterology 2010 Jun 23;138(7):2378-87. Epub 2010 Feb 23.

INSERM, U892, Equipe Cytokine/Récepteur, Nantes, France.

Background & Aims: Infliximab is a monoclonal antibody against tumor necrosis factor that is used to treat patients with inflammatory bowel disease. We investigated serum levels and cellular expression of interleukin (IL)-15 and its receptor (sIL-15Ralpha) in patients with Crohn's disease (CD) treated with infliximab; and the effect on sIL-15Ralpha secretion by epithelial cells.

Methods: CD patients were given infliximab (n = 40; 3 infusions); 37 healthy controls were studied. Serum levels of IL-15, sIL-15Ralpha, and complex were determined by radioimmunoassay and cytokine levels by enzyme-linked immunosorbent assay. IL-15Ralpha and A Desintegrin and Metalloproteinase 17 levels were assessed by immunohistochemistry. Epithelial cell lines (HT-29 and Caco-2) were cultured with infliximab, adalimumab, or etanercept. Patients were classified as responders and nonresponders according to their Crohn's Disease Activity Index and clinical observations.

Results: Before infliximab, IL-15 was higher in responders than in controls and nonresponders. After infliximab, IL-15 decreased in responders while remaining stable in nonresponders. sIL-15Ralpha and IL-15/sIL-15Ralpha complex levels were higher in CD than in controls and increased only in responders after infliximab. IL-15Ralpha and A Desintegrin and Metalloproteinase 17 colocalized in epithelial cells and were higher in CD patients. In vitro, infliximab but not adalimumab and etanercept induced sIL-15Ralpha secretion by epithelial cells.

Conclusions: Serum level of sIL-15Ralpha and the IL-15/sIL-15Ralpha complex increased in responder patients and the response was associated with a decrease of IL-15. Infliximab induced the release of the IL-15 receptor alpha, suggesting a specific modulation of IL-15 and its soluble receptor by reverse signaling through transmembrane tumor necrosis factor alpha.
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http://dx.doi.org/10.1053/j.gastro.2010.02.044DOI Listing
June 2010

Macrophage- and dendritic-cell-derived interleukin-15 receptor alpha supports homeostasis of distinct CD8+ T cell subsets.

Immunity 2009 Nov 12;31(5):811-22. Epub 2009 Nov 12.

Department of Medicine, University of California, San Francisco, San Francisco, CA 94143-0451, USA.

Interleukin-15 receptor alpha (IL-15R alpha) is a pleiotropically expressed molecule that chaperones and trans-presents IL-15 to NK and T cells. To investigate whether IL-15R alpha presented by different cells perform distinct physiological functions, we have generated four lines of mice lacking IL-15R alpha in various cell types. We find that IL-15R alpha expression on macrophages but not dendritic cells (DCs) supports the early transition of antigen specific effector CD8(+) T cells to memory cells. After memory CD8(+) T cell differentiation, IL-15R alpha expression on DCs selectively supports central memory CD8(+) T cells, whereas IL-15R alpha expression on macrophages supports both central and effector memory CD8(+) T cells. By contrast, mice lacking IL-15R alpha on macrophages, DCs, or both, exhibit equivalent defects in NK cell homeostasis and activation. These studies define unique roles for macrophage expression of IL-15R alpha and show that NK cells rely upon distinct IL-15R alpha dependent IL-15 signals than memory CD8(+) T cells. Moreover, they demonstrate the diversity, specification, and geographic restriction of cytokine signals.
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http://dx.doi.org/10.1016/j.immuni.2009.09.017DOI Listing
November 2009

IL-15 trans-presentation promotes human NK cell development and differentiation in vivo.

J Exp Med 2009 Jan 22;206(1):25-34. Epub 2008 Dec 22.

Immunology Department, 2 Institut National de la Santé et de la Recherche Médicale U668, 3 INSERM U883, Unité de Régulation Immunitaire et Vaccinologie, Institut Pasteur, Paris 75724, France.

The in vivo requirements for human natural killer (NK) cell development and differentiation into cytotoxic effectors expressing inhibitory receptors for self-major histocompatibility complex class I (MHC-I; killer Ig-like receptors [KIRs]) remain undefined. Here, we dissect the role of interleukin (IL)-15 in human NK cell development using Rag2(-/-)gamma c(-/-) mice transplanted with human hematopoietic stem cells. Human NK cell reconstitution was intrinsically low in this model because of the poor reactivity to mouse IL-15. Although exogenous human IL-15 (hIL-15) alone made little improvement, IL-15 coupled to IL-15 receptor alpha (IL-15R alpha) significantly augmented human NK cells. IL-15-IL-15R alpha complexes induced extensive NK cell proliferation and differentiation, resulting in accumulation of CD16(+)KIR(+) NK cells, which was not uniquely dependent on enhanced survival or preferential responsiveness of this subset to IL-15. Human NK cell differentiation in vivo required hIL-15 and progressed in a linear fashion from CD56(hi)CD16(-)KIR(-) to CD56(lo)CD16(+)KIR(-), and finally to CD56(lo)CD16(+)KIR(+). These data provide the first evidence that IL-15 trans-presentation regulates human NK cell homeostasis. Use of hIL-15 receptor agonists generates a robust humanized immune system model to study human NK cells in vivo. IL-15 receptor agonists may provide therapeutic tools to improve NK cell reconstitution after bone marrow transplants, enhance graft versus leukemia effects, and increase the pool of IL-15-responsive cells during immunotherapy strategies.
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http://dx.doi.org/10.1084/jem.20082013DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2626663PMC
January 2009

The exon-3-encoded domain of IL-15ralpha contributes to IL-15 high-affinity binding and is crucial for the IL-15 antagonistic effect of soluble IL-15Ralpha.

J Mol Biol 2008 Sep 16;382(1):1-12. Epub 2008 Jul 16.

INSERM, U892, Centre de Recherche en Cancérologie Nantes/Angers, Groupe Cytokines et Récepteurs, Nantes, France; Université de Nantes, IFR26, Nantes, France.

We previously showed that a natural soluble form of interleukin-15 (IL-15) Ralpha corresponding to the full-length ectodomain of IL-15Ralpha behaved as a potent antagonist of IL-15 action through IL-15Ralpha/beta/gamma, whereas a recombinant soluble IL-15Ralpha sushi domain did not, but instead acted as an agonist of IL-15 action through IL-15Rbeta/gamma. In order to determine precisely the molecular basis governing these antagonistic versus agonistic actions, we compared the binding properties and biological effects of recombinant soluble IL-15Ralpha (sIL-15Ralpha) species containing the sushi domain and different remaining parts of the ectodomain. We first demonstrate that the exon-3-encoded domain and, more particularly, its N-terminal 13-amino-acid (aa) peptide are important, in addition to the adjacent exon-2-encoded sushi domain, for the stabilization of the high-affinity IL-15.IL-15Ralpha complex by slowing down its dissociation rate and by contributing to about 10-20% of the free energy of interaction. We next show that all sushi-containing sIL-15Ralpha are agonists on IL-15Rbeta/gamma, coordinately increasing IL-15 binding and IL-15-induced proliferation. Their agonistic potencies are proportional to their respective affinities for IL-15. We then show that the antagonistic effect of sIL-15Ralpha in the context of IL-15Ralpha/beta/gamma is due to the 13-aa peptide that creates a sterical constraint impeding the binding of the sIL-15Ralpha.IL-15 complex to the membrane-anchored IL-15Ralpha/beta/gamma. In the frame of the soluble IL-15Ralpha sushi domain-IL-15 fusion protein that contains the 13-aa peptide, this constraint is alleviated as a result of a conformational effect due to the covalent linking of the 13-aa peptide to the N-terminus of IL-15. The soluble IL-15Ralpha sushi domain-IL-15 fusion protein is therefore able to bind and activate both the IL-15Rbeta/gamma and the IL-15Ralpha/beta/gamma receptors.
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http://dx.doi.org/10.1016/j.jmb.2008.07.019DOI Listing
September 2008

The soluble alpha chain of interleukin-15 receptor: a proinflammatory molecule associated with tumor progression in head and neck cancer.

Cancer Res 2008 May;68(10):3907-14

EA 4054 Université Paris Descartes, Faculté de Medecine; Ecole Nationale Vétérinaire d'Alfort, Maisons-Alfort, France.

Interleukin (IL)-15 is a proinflammatory cytokine, as it induces the production of inflammatory cytokines [IL-6, tumor necrosis factor alpha (TNFalpha), IL-17, etc.]. A correlation between high intratumoral IL-15 concentrations and poor clinical outcome in lung and head and neck cancer patients has been recently reported. The purpose of this study was to investigate the role of the soluble alpha chain of IL-15 receptor (sIL-15Ralpha), a natural regulator of IL-15, in head and neck cancer. Fifty-three newly diagnosed untreated head and neck cancer patients were included in this study. Quantification of sIL-15Ralpha was performed with a newly developed RIA. Increased serum sIL-15Ralpha concentrations were found in head and neck cancer patients and were closely correlated with poor clinical outcome both in terms of locoregional control and survival even on multivariate analysis. sIL-15Ralpha was mainly produced by tumor cells via proteolytic cleavage of IL-15Ralpha mediated by ADAM-17. A correlation was observed between ADAM-17 expression in tumor cells and serum sIL-15Ralpha concentrations. Surprisingly, sIL-15Ralpha did not act in vitro as an IL-15 antagonist but rather as an enhancer of IL-15-induced proinflammatory cytokines (IL-6, TNFalpha, and IL-17) that may promote tumor progression. This new tumor evasion mechanism based on amplification of the intratumoral inflammatory reaction is probably not restricted to head and neck cancer, as other tumors have been shown to release sIL-15Ralpha. Overall, these results support for the first time an original protumor role of sIL-15Ralpha in cancer.
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http://dx.doi.org/10.1158/0008-5472.CAN-07-6842DOI Listing
May 2008

IL-15Ralpha chaperones IL-15 to stable dendritic cell membrane complexes that activate NK cells via trans presentation.

J Exp Med 2008 May 5;205(5):1213-25. Epub 2008 May 5.

Colitis and Crohn's Disease Center, Gastroenterology Division, Department of Medicine, Biomedical Sciences Program, Program in Biological Sciences, University of California, San Francisco, San Francisco, CA 94143, USA.

Natural killer (NK) cells are innate immune effectors that mediate rapid responses to viral antigens. Interleukin (IL)-15 and its high affinity IL-15 receptor, IL-15Ralpha, support NK cell homeostasis in resting animals via a novel trans presentation mechanism. To better understand how IL-15 and IL-15Ralpha support NK cell activation during immune responses, we have used sensitive assays for detecting native IL-15 and IL-15Ralpha proteins and developed an assay for detecting complexes of these proteins. We find that IL-15 and IL-15Ralpha are preassembled in complexes within the endoplasmic reticulum/Golgi of stimulated dendritic cells (DCs) before being released from cells. IL-15Ralpha is required for IL-15 production by DCs, and IL-15 that emerges onto the cell surface of matured DCs does not bind to neighboring cells expressing IL-15Ralpha. We also find that soluble IL-15-IL-15Ralpha complexes are induced during inflammation, but membrane-bound IL-15-IL-15Ralpha complexes, rather than soluble complexes, support NK cell activation in vitro and in vivo. Finally, we provide in vivo evidence that expression of IL-15Ralpha specifically on DCs is critical for trans presenting IL-15 and activating NK cells. These studies define an unprecedented cytokine-receptor biosynthetic pathway in which IL-15Ralpha serves as a chaperone for IL-15, after which membrane-bound IL-15Ralpha-IL-15 complexes activate NK cells via direct cell-cell contact.
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http://dx.doi.org/10.1084/jem.20071913DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2373851PMC
May 2008

Homeostatic MyD88-dependent signals cause lethal inflamMation in the absence of A20.

J Exp Med 2008 Feb 11;205(2):451-64. Epub 2008 Feb 11.

Gastrointestinal Division, Department of Medicine, Biomedical Sciences Program, University of California, San Francisco, San Francisco, CA 94143, USA.

Toll-like receptors (TLRs) on host cells are chronically engaged by microbial ligands during homeostatic conditions. These signals do not cause inflammatory immune responses in unperturbed mice, even though they drive innate and adaptive immune responses when combating microbial infections. A20 is a ubiquitin-modifying enzyme that restricts exogenous TLR-induced signals. We show that MyD88-dependent TLR signals drive the spontaneous T cell and myeloid cell activation, cachexia, and premature lethality seen in A20-deficient mice. We have used broad spectrum antibiotics to demonstrate that these constitutive TLR signals are driven by commensal intestinal flora. A20 restricts TLR signals by restricting ubiquitylation of the E3 ligase tumor necrosis factor receptor-associated factor 6. These results reveal both the severe proinflammatory pathophysiology that can arise from homeostatic TLR signals as well as the critical role of A20 in restricting these signals in vivo. In addition, A20 restricts MyD88-independent TLR signals by inhibiting Toll/interleukin 1 receptor domain-containing adaptor inducing interferon (IFN) beta-dependent nuclear factor kappaB signals but not IFN response factor 3 signaling. These findings provide novel insights into how physiological TLR signals are regulated.
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http://dx.doi.org/10.1084/jem.20071108DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2271029PMC
February 2008

Docking of human interleukin-15 to its specific receptor alpha chain: correlation between molecular modeling and mutagenesis experimental data.

Proteins 2006 Nov;65(3):623-36

INSERM, U601, Groupe de Recherche Cytokines et Récepteurs, Institut de Biologie, Nantes, France.

A structural model of the sushi domain of IL-15Ralpha was first obtained by homology modeling to study its interactions with IL-15 by means of molecular modeling, peptide scanning, and site-directed mutagenesis. From these experimental data, a putative interacting surface of IL-15Ralpha with a previously published IL-15 model was inferred: Leu25, Leu44, and Glu46 of IL-15 and Arg35 of IL-15Ralpha were found to be key interfacial residues and were subsequently used as filters for the construction of docking solutions. Human IL-15/IL-15Ralpha complexes were constructed in two stages, with a preliminary docking procedure, treating the two partners as rigid bodies and using these filters. In this first stage, two classes of docking solutions were characterized. From a topological point of view, each solution could be derived from the other by reverse orientation of one partner in relation to the other. In a second stage, several further energy refinements clearly favored one solution. Moreover, this unique docking solution was confirmed by molecular modeling of IL-15 mutants previously built and tested in our laboratory. Finally, this complex model, which is a useful tool to study the IL-15/IL-15Ralpha interface, was topologically compared to IL-2/IL-2Ralpha complexes (previous model in the literature and recent crystal structure).
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http://dx.doi.org/10.1002/prot.21103DOI Listing
November 2006

Soluble interleukin-15 receptor alpha (IL-15R alpha)-sushi as a selective and potent agonist of IL-15 action through IL-15R beta/gamma. Hyperagonist IL-15 x IL-15R alpha fusion proteins.

J Biol Chem 2006 Jan 11;281(3):1612-9. Epub 2005 Nov 11.

INSERM, U601, Groupe de Recherche Cytokines et Récepteurs, Institut de Biologie, Nantes F-44093, France.

Interleukin-15 (IL-15) is crucial for the generation of multiple lymphocyte subsets (natural killer (NK), NK-T cells, and memory CD8 T cells), and transpresentation of IL-15 by monocytes and dendritic cells has been suggested to be the dominant activating process of these lymphocytes. We have previously shown that a natural soluble form of IL-15R alpha chain corresponding to the entire extracellular domain of IL-15R alpha behaves as a high affinity IL-15 antagonist. In sharp contrast with this finding, we demonstrate in this report that a recombinant, soluble sushi domain of IL-15R alpha, which bears most of the binding affinity for IL-15, behaves as a potent IL-15 agonist by enhancing its binding and biological effects (proliferation and protection from apoptosis) through the IL-15R beta/gamma heterodimer, whereas it does not affect IL-15 binding and function of the tripartite IL-15R alpha/beta/gamma membrane receptor. Our results suggest that, if naturally produced, such soluble sushi domains might be involved in the IL-15 transpresentation mechanism. Fusion proteins (RLI and ILR), in which IL-15 and IL-15R alpha-sushi are attached by a flexible linker, are even more potent than the combination of IL-15 plus sIL-15R alpha-sushi. After binding to IL-15R beta/gamma, RLI is internalized and induces a biological response very similar to the IL-15 high affinity response. Such hyper-IL-15 fusion proteins appear to constitute potent adjuvants for the expansion of lymphocyte subsets.
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http://dx.doi.org/10.1074/jbc.M508624200DOI Listing
January 2006

Natural, proteolytic release of a soluble form of human IL-15 receptor alpha-chain that behaves as a specific, high affinity IL-15 antagonist.

J Immunol 2004 Aug;173(3):1681-8

Groupe de Recherche Cytokines et Récepteurs en Immunologie et Cancérologie, Département de Cancérologie, Institut National de la Santé et de la Recherche Médicale Unité 601, Institut de Biologie, Nantes, France.

IL-15 and IL-2 are two structurally and functionally related cytokines whose high affinity receptors share the IL-2R beta-chain and gamma-chain in association with IL-15R alpha-chain (IL-15R alpha) or IL-2R alpha-chain, respectively. Whereas IL-2 action seems restricted to the adaptative T cells, IL-15 appears to be crucial for the function of the innate immune responses, and the pleiotropic expression of IL-15 and IL-15R alpha hints at a much broader role for the IL-15 system in multiple cell types and tissues. In this report, using a highly sensitive radioimmunoassay, we show the existence of a soluble form of human IL-15R alpha (sIL-15R alpha) that arises from proteolytic shedding of the membrane-anchored receptor. This soluble receptor is spontaneously released from IL-15R alpha-expressing human cell lines as well as from IL-15R alpha transfected COS-7 cells. This release is strongly induced by PMA and ionomycin, and to a lesser extent by IL-1 beta and TNF-alpha. The size of sIL-15R alpha (42 kDa), together with the analysis of deletion mutants in the ectodomain of IL-15R alpha, indicates the existence of cleavage sites that are proximal to the plasma membrane. Whereas shedding induced by PMA was abrogated by the synthetic matrix metalloproteinases inhibitor GM6001, the spontaneous shedding was not, indicating the occurrence of at least two distinct proteolytic mechanisms. The sIL-15R alpha displayed high affinity for IL-15 and behaved as a potent and specific inhibitor of IL-15 binding to the membrane receptor, and of IL-15-induced cell proliferation (IC(50) in the range from 3 to 20 pM). These results suggest that IL-15R alpha shedding may play important immunoregulatory functions.
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http://dx.doi.org/10.4049/jimmunol.173.3.1681DOI Listing
August 2004

Identification of an interleukin-15alpha receptor-binding site on human interleukin-15.

J Biol Chem 2004 Jun 23;279(23):24313-22. Epub 2004 Mar 23.

Groupe de Recherche Cytokines et Récepteurs, Unité INSERM 601, Institut de Biologie, 9 Quai Moncousu, 44093 Nantes Cedex 01, France.

To identify the epitopes in human interleukin-15 (IL-15) that are responsible for binding to the interleukin-15 receptor alpha chain, antibody and receptor mapping by peptide scanning and site-directed mutagenesis was used. By using peptide scanning, we identified four regions in IL-15. The first region ((85)CKECEELEEKN(95)) is located in the C-D loop and is recognized by a set of non-inhibitory antibodies. The second region ((102)SFVHIVQMFIN(112)) is located in helix D and is recognized by two antibodies that are inhibitory of IL-15 bio-activity but not of IL-15 binding to IL-15Ralpha. The two remaining regions react with a recombinant soluble form of the IL-15Ralpha; the first ((44)LLELQVISL(52), peptide 1) corresponds to a sequence located in the B-helix and the second ((64)ENLII(68), peptide 2) to a sequence located in helix C. The latter is also contained in the epitope recognized by an antibody (monoclonal antibody B-E29) that prevents IL-15 binding to IL-15Ralpha. By site-directed mutagenesis, we confirmed that residues present in peptide 1 (Leu-45, Glu-46, Val-49, Ser-51, and Leu-52) and peptide 2 (Leu-66 and Ile-67) are involved in the binding of IL-15 to IL-15Ralpha. Furthermore, the results presented indicate that residues in the second peptide (Glu-64, Asn-65, and Ile-68) participate in IL-2Rbeta recruitment. This finding could have implications for the dynamics of receptor assembly. These results also indicate that the modes of interaction of IL-15 and IL-2 with their respective alpha chains are not completely analogous. Finally, some of the IL-15 mutants generated in this study displayed agonist or antagonist properties and may be useful as therapeutic agents.
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http://dx.doi.org/10.1074/jbc.M312458200DOI Listing
June 2004