Inhibition of the JAK/STAT Signaling Pathway in Regulatory T Cells Reveals a Very Dynamic Regulation of Foxp3 Expression

The IL-2/JAK3/STAT-5 signaling pathway is involved on the initiation and maintenance of the transcription factor Foxp3 in regulatory T cells (Treg) and has been associated with demethylation of the intronic Conserved Non Coding Sequence-2 (CNS2). However, the role of the JAK/STAT pathway in controlling Foxp3 in the short term has been poorly investigated. Using two different JAK/STAT pharmacological inhibitors, we observed a detectable loss of Foxp3 after 10 min. of treatment that affected 70% of the cells after one hour. Using cycloheximide, a general inhibitor of mRNA translation, we determined that Foxp3, but not CD25, has a high turnover in IL-2 stimulated Treg. This reduction was correlated with a rapid reduction of Foxp3 mRNA. This loss of Foxp3 was associated with a loss in STAT-5 binding to the CNS2, which however remains demethylated. Consequently, Foxp3 expression returns to normal level upon restoration of basal JAK/STAT signaling in vivo. Reduced expression of several genes defining Treg identity was also observed upon treatment. Thus, our results demonstrate that Foxp3 has a rapid turn over in Treg partly controlled at the transcriptional level by the JAK/STAT pathway

Targeting the ICOS costimulatory molecule for breast cancer immunotherapy in a humanized mouse model

Au cours de ces 20 dernières années, les inhibiteurs de "checkpoint blockade" sont une des stratégies les plus prometteuses pour l’immunothérapie du cancer. une partie de l'effet anti-tumoral de ces inhibiteurs reposerait sur la déplétion des lymphocytes T régulateurs (TREG). ici, nous avons examine si la forte expression d'ICOS sur ces cellules pourrait être utilisée comme marqueur pour cibler les TREG et améliorer le rejet tumoral. nous rapportons qu'un nouvel acm anti-ICOS humain deplete préférentiellement les TREG dans un modèle de souris nsg humanisées (cd34+) menant a une augmentation du rapport cd8+/treg. toutefois, cela ne suffisait pas a influer sur la croissance de la lignée de cancer du sein mda-mb-231. nous avons administre du cyclophosphamide (CTX) a faible dose pour induire de la mort cellulaire immunogène et stimuler la réponse anti-tumorale. le traitement des animaux avec une combinaison CTX + anti-ICOS conduit 0 une réduction drastique de la croissance tumorale alors que les traitements individuels ont des effets modérés. Grâce a la cytométrie de masse (cytof), nous avons observe une plus forte expression de cd45ro, hla-dr et ki-67 sur les ltcd8+ du groupe traite par la combinaison. de plus, d'autres analyses suggèrent que les monocytes et PDC humains et les cellules myéloïdes murines pourraient être impliqués dans cet effet. au final, nos résultats sont la première démonstration que les souris humanisées peuvent être utilisées pour développer de nouvelles immunothérapies anti-cancer et indiquent que le ciblage TREG avec une combinaison d'ACM anti-ICOS et la chimiothérapie est une strat2gie pertinente pour renforcer la réponse anti-tumorale.Checkpoint blockade inhibitors are the most promising and effective strategy for t-cell mediated cancer immunotherapy of the past 20 years. Part of the anti-tumoral effect of these checkpoint inhibitors might be due to regulatory T cell (treg) depletion. Here, we investigated whether the reported high expression of icos on treg might be used as a flag to target treg and improve tumor rejection. We report that a novel anti-human icos mab preferentially depleted treg in immunodeficient nsg mice reconstituted with cd34+ progenitors, leading to an increased cd8+/treg ratio. However, this was insufficent to affect growth of the breast cancer cell line mda-mb-231. We thus administered low dose cyclophosphamide (ctx) to induce immunogenic cell death and stimulate anti-tumor response. Treatment of humanized mice with a combination of ctx+ anti-icos mab led to a drastic reduction in tumor growth whereas single treatments had only moderated effect. Using mass cytometry (cytof), we observed higher expression of cd45ro, hla-dr and ki67 on tcd8+ of the combined-treatment group. Accordingly, depletion of cd8+ t cells partly abolished the therapeutic effect of the combination. Moreover, additional analyses suggest that human monocytes and pdc and murine myeloid cells are involved in this effect. Altogether, our results represent the first demonstration that humanized mice can be used to develop novel therapeutic strategies for cancer immunotherapy and indicate that targeting treg with a combination of anti-icos mab and chemotherapy is a relevant strategy to release the immune response to the tumor

Targeting the Human T-Cell Inducible COStimulator Molecule with a Monoclonal Antibody Prevents Graft-vs-Host Disease and Preserves Graft vs Leukemia in a Xenograft Murine Model

International audienceBackground: Graft-vs-host disease (GVHD) is a major complication of allogenic bone marrow transplantation (BMT). Targeting costimulatory molecules with antagonist antibodies could dampen the excessive immune response that occurs, while preserving the beneficial graft vs leukemia (GVL) of the allogeneic response. Previous studies using a mouse model of GVHD have shown that targeting the T-cell Inducible COStimulator (ICOS, CD278) molecule is beneficial, but it is unclear whether the same applies to human cells.Methods: Here, we assessed whether a monoclonal antibody (mAb) to human ICOS was able to antagonize the costimulatory signal delivered in vivo to human T cells. To test this hypothesis, we used a xenogeneic model of GVHD where human peripheral blood mononuclear cells were adoptively transferred in immunocompromised NOD.SCID.gc-null mice (NSG).Results: In this model, control mice invariably lost weight and died by day 50. In contrast, 65% of the mice receiving a single injection of the anti-hICOS mAb survived beyond 100 days. Moreover, a significant improvement in survival was obtained in a curative xeno-GVHD setting. Mechanistically, administration of the anti-hICOS mAb was associated with a strong reduction in perivascular infiltrates in liver and lungs and reduction in frequencies and numbers of human T cells in the spleen. In addition, the mAb prevented T-cell expansion in the blood during xeno-GVHD. Importantly, GVHD-protected mice retained the ability to control the P815 mastocytoma cell line, mimicking GVL in humans.Conclusion: A mAb-targeting human ICOS alleviated GVHD without impairing GVL in a xenograft murine model. Thus, ICOS represents a promising target in the management of BMT, preventing GVHD while preserving GVL

Targeting Both Viral and Host Determinants of Human Immunodeficiency Virus Entry, Using a New Lentiviral Vector Coexpressing the T20 Fusion Inhibitor and a Selective CCL5 Intrakine

This is a copy of an article published in Human Gene Therapy Methods © [2014 [copyright Mary Ann Liebert, Inc.]; [Human Gene Therapy Methods] is available online at: http://online.liebertpub.com.International audienceNumerous strategies targeting early and late steps of the HIV life cycle have been proposed for gene therapy. However, targeting viral and host determinants of HIV entry is the only strategy that would prevent viral DNA-mediated CD4 + cell death while diminishing the possibility for the virus to escape. To this end, we devised a bicistronic lentiviral vector expressing the membrane-bound form of the T20 fusion inhibitor, referred to as the C46 peptide, and a CCR5 superagonist, modified to sequester CCR5 away from the cell surface, referred to as the P2-CCL5 intrakine. We tested the effects of the vector on HIV infection and replication, using the human CEMR5 cell line expressing CD4 and CCR5, and primary human T cells. Transduced cells expressed the C46 peptide, detected with the 2F5 monoclonal antibody by flow cytometry. Expression of the P2-CCL5 intrakine correlates with lower levels of cell surface CCR5. Complete protection against HIV infection could be observed in cells expressing the protective transgenes. Importantly, we show that the combination of the transgenes was more potent than either transgene alone, showing the interest of expressing two entry inhibitors to inhibit HIV infection. Last, genetically modified cells possessed a selective advantage over nonmodified cells on HIV challenge in vitro, showing that modified cells were protected from HIV-induced cell death. Our results demonstrate that lentiviral vectors coexpressing the T20 fusion inhibitor and the P2-CCL5 intrakine represent promising tools for HIV gene therapy

A novel combination of chemotherapy and immunotherapy controls tumor growth in mice with a human immune system

International audienceMice reconstituted with a human immune system and bearing human tumors represent a promising model for developing novel cancer immunotherapies. Here, we used mass cytometry and multi-parametric flow cytometry to characterize human leukocytes infiltrating a human breast cancer tumor model in immunocompromised NOD.SCID.γc-null mice reconstituted with a human immune system and compared it to samples of breast cancer patients. We observed highly activated human CD4+ and CD8+ T cells in the tumor, as well as minor subsets of innate immune cells in both settings. We also report that ICOS+ CD4+ regulatory T cells (Treg) were enriched in the tumor relative to the periphery in humanized mice and patients, providing a target to affect Treg and tumor growth. Indeed, administration of a neutralizing mAb to human ICOS reduced Treg proportions and numbers and improved CD4 + T cell proliferation in humanized mice. Moreover, a combination of the anti-ICOS mAb with cyclophosphamide reduced tumor growth, and that was associated with an improved CD8 to Treg ratio. Depletion of human CD8+ T cells or of murine myeloid cells marginally affected the effect of the combination therapy. Altogether, our results indicate that a combination of anti-ICOS mAb and chemotherapy controls tumor growth in humanized mice, opening new perspectives for the treatment of breast cancer

Inhibition of the JAK/STAT Signaling Pathway in Regulatory T Cells Reveals a Very Dynamic Regulation of Foxp3 Expression

International audienceThe IL-2/JAK3/STAT-5 signaling pathway is involved on the initiation and maintenance of the transcription factor Foxp3 in regulatory T cells (Treg) and has been associated with demethylation of the intronic Conserved Non Coding Sequence-2 (CNS2). However, the role of the JAK/STAT pathway in controlling Foxp3 in the short term has been poorly investigated. Using two different JAK/STAT pharmacological inhibitors, we observed a detectable loss of Foxp3 after 10 min. of treatment that affected 70% of the cells after one hour. Using cycloheximide, a general inhibitor of mRNA translation, we determined that Foxp3, but not CD25, has a high turnover in IL-2 stimulated Treg. This reduction was correlated with a rapid reduction of Foxp3 mRNA. This loss of Foxp3 was associated with a loss in STAT-5 binding to the CNS2, which however remains demethylated. Consequently, Foxp3 expression returns to normal level upon restoration of basal JAK/STAT signaling in vivo. Reduced expression of several genes defining Treg identity was also observed upon treatment. Thus, our results demonstrate that Foxp3 has a rapid turn over in Treg partly controlled at the transcriptional level by the JAK/STAT pathway

Combination of IL-2, rapamycin, DNA methyltransferase and histone deacetylase inhibitors for the expansion of human regulatory T cells

International audienceFOXP3+ regulatory T cell (Treg) based cellular therapies represent promising therapeutic options in autoimmunity, allergy, transplantation and prevention of Graft Versus Host (GVH) Disease. Among human FOXP3-expressing CD4+T cells, only the CD45RA+ naïve Treg (nTreg) subset is suitable for in vitro expansion. However, FoxP3 expression decays in cells using currently described culture protocols. Rapamycin alone was not able to prevent FOXP3 loss in nTregs cells, as only a half of them maintained FOXP3 expression after 14 days of culture. In contrast we report a novel combined drug regimen that can drastically stabilize FOXP3 expression in cultured Tregs. IL-2, rapamycin, histone deacetylase and DNA methyltransferase inhibitors act in synergy to allow expansion of human regulatory T cells with sustained high expression of FOXP3 and CD15s with potent suppressive capacities in vitro and control of murine xeno-GVH reactions. Of note, an additional subsequent infusion of expanded nTreg cells did not improve survival of mice. Combination of IL-2, rapamycin, histone deacetylase and DNA methyltransferase inhibitors is optimal for the expansion in vitro of pure effective nTreg maintaining high levels of FOXP3 for therapeutic purposes

Human Apoptotic Cells, Generated by Extracorporeal Photopheresis, Modulate Allogeneic Immune Response

International audienceThe induction of specific and sustainable tolerance is a challenging issue in organ transplantation. The discovery of the immunosuppressive properties of apoptotic cells in animal models has paved the way for their use in human transplantation. In this work, we aimed to define a stable, reproducible, and clinically compatible production procedure of human apoptotic cells (Apo-cells). Using a clinically approved extracorporeal photopheresis technique, we have produced and characterized phenotypically and functionally human apoptotic cells. These Apo-cells have immunosuppressive properties proved in vitro and in vivo in NOD/SCID/γC mice by their capacity to modulate an allogeneic response following both a direct and an indirect antigen presentation. These results brought the rationale for the use of Apo-cells in tolerance induction protocol for organ transplantation

Blockade of JAK/STAT signaling pathway leads to down modulation of Foxp3 in Treg.

<p>(<b>a</b>) CD25-enriched T cells were cultured for one hour in complete medium alone (Med.), with IL-2 (IL-2), or IL-2 supplemented with ZM-39923 (IL-2+ZM) or AG-490 (IL-2+AG). Profiles shown are gated in CD4⁺ cells and are representative of 4 independent experiments. (<b>b</b>) Frequencies of pSTAT5⁺ cells among CD4⁺ cells cultured for one hour with IL-2 alone (IL-2) or in presence of IL-2 and the indicated JAK inhibitors (ZM, AG). Results are compiled from 4 independent experiments. <b>(c)</b> In vitro expanded CD4⁺GFP⁺ Treg were treated with IL-2 and with either 100ug/mL of AG490 (IL-2+AG) or vehicle control (absolute ethanol; EtOH) for 2 hrs (IL-2). Proteins were extracted in lysis buffer and blotted followed by anti-Foxp3 and anti-actin staining. Intensity values were normalized to the actin band in each blot. The specificity of the Foxp3 staining is attested by the absence of the Foxp3 band in extracts from splenocytes of a scurfy (genetically deficient for Foxp3) mouse. <b>(d)</b> Human CD4⁺CD25⁺ cells were enriched from PBMC of healthy donors by magnetic sorting and treated with IL-2 (600 IU/mL) with or without ZM (50 μM) for 1h. MFI of CD25 and FOXP3 in human CD4⁺CD3⁺ cells after treatment with IL-2 alone (IL-2) or IL-2 in presence of ZM (IL-2+ZM). The MFI of Foxp3 and CD25 shown were normalized by the MFI of control cultures. These data are compiled from 3 independent experiments. Statistical significance was tested using Student t-test (***p<0.001, **p<0.01, *p<0.05).</p

Reduced Foxp3 by JAK/STAT inhibitors is independent of cell death.

<p><b>(a)</b> CD4⁺GFP⁺ T cells sorted from Foxp3-GFP transgenic mice were stimulated with anti-CD3/CD28 beads for 8 days and treated with vehicle and IL-2 (IL-2), or IL-2 supplemented with ZM (IL-2+ZM) or AG (IL-2+AG) JAK inhibitors for two hours. Cells were then stained with a dye allowing exclusion of dead cells by flow cytometry compatible with Foxp3 intracellular staining. Profiles are representative of 6 and 7 independent experiments for AG and ZM inhibitors, respectively. <b>(b)</b> Foxp3 and Bcl-2 expression in gated CD4⁺CD25⁺ cells from expanded CD4⁺GFP⁺ cells after 2 hour treatment with vehicle control and IL-2 (IL-2) or ZM in presence of IL-2 (IL-2+ZM). Similar results were observed in 3 independent experiments. <b>(c)</b> Median fluorescence intensity (MFI) of CD25 and Foxp3 in dead cell–excluded subset, represented as percentages of the MFI relative to Foxp3 staining in vehicle control condition (control) after two hours treatment with the indicated inhibitors. The results are compiled from 6 (AG) and 7 (ZM) independent experiments. <b>(d)</b> Freshly isolated or <b>(e)</b> anti-CD3/CD28 activated CD4⁺GFP⁺ cells from Foxp3-eGFP reporter mice were treated for the indicated times with either ZM or AG inhibitors. MFI of CD25 and Foxp3 are relative to the MFI of vehicle control conditions. These data are compiled from 3 independent experiments. Statistical significance was tested using Student t-test (***p<0.001, **p<0.01, *p<0.05).</p