Ex Vivo Expanded Human Non-Cytotoxic CD8+CD45RClow/− Tregs Efficiently Delay Skin Graft Rejection and GVHD in Humanized Mice

Both CD4+ and CD8+ Tregs play a critical role in the control of immune responses and immune tolerance; however, our understanding of CD8+ Tregs is limited while they are particularly promising for therapeutic application. We report here existence of highly suppressive human CD8+CD45RClow/− Tregs expressing Foxp3 and producing IFNγ, IL-10, IL-34, and TGFβ to mediate their suppressive activity. We demonstrate that total CD8+CD45RClow/− Tregs can be efficiently expanded in the presence of anti-CD3/28 mAbs, high-dose IL-2 and IL-15 and that such expanded Tregs efficiently delay GVHD and human skin transplantation rejection in immune humanized mice. Robustly expanded CD8+ Tregs displayed a specific gene signature, upregulated cytokines and expansion in the presence of rapamycin greatly improved proliferation and suppression. We show that CD8+CD45RClow/− Tregs are equivalent to canonical CD4+CD25highCD127low/− Tregs for suppression of allogeneic immune responses in vitro. Altogether, our results open new perspectives to tolerogenic strategies in human solid organ transplantation and GVHD

Ectopic expression of the immune adaptor protein CD3zeta in neural stem/progenitor cells disrupts cell-fate specification

Immune signaling and neuroinflammatory mediators have recently emerged as influential variables that regulate neural precursor/stem cell (NPC) behavior and function. In this study, we investigated whether the signaling adaptor protein CD3ζ, a transmembrane protein involved in T cell differentiation and function and recently shown to regulate neuronal development in the central nervous system (CNS), may have a role in NPC differentiation. We analyzed the expression profile of CD3ζ in embryonic rat brain during neurogenic periods and in neurosphere-derived neural cells, and we investigated the action of CD3ζ on cell differentiation. We found that CD3ζ expression coincided with neuronal commitment, but its forced expression in NPCs prevented the production of neurons and oligodendrocytes, but not astroglial cells. This blockade of neuronal differentiation was operated through an ITAM-independent mechanism, but required the Asp36 of the CD3ζ transmembrane domain involved in membrane receptor interaction. Together, our findings show that ectopic CD3ζ expression in NPCs impaired their normal cell-fate specification and suggest that variations of CD3ζ expression in the developing CNS might result in neurodevelopmental anomalies

Human CD8+ Tregs expressing a MHC-specific CAR display enhanced suppression of human skin rejection and GVHD in NSG mice

International audiencePolyclonal CD8+CD45RClow/- Tregs are potent regulatory cells able to control solid organ transplantation rejection and even induce tolerance. However, donor major histocompatibility complex (MHC)-specific Tregs are more potent than polyclonal Tregs in suppressing T-cell responses and preventing acute as well as chronic rejection in rodent models. The difficulty of identifying disease-relevant antigens able to stimulate Tregs has reduced the possibility of obtaining antigen-specific Tregs. To bypass this requirement and gain the advantage of antigen specificity, and thus improve the therapeutic potential of CD8+ Tregs, we stably introduced a chimeric antigen receptor (CAR) derived from a HLA-A*02 antigen-specific antibody (A2-CAR) in human CD8+ Tregs and developed a clinically compatible protocol of transduction and expansion. We demonstrated that A2-CAR CD8+ Tregs were not phenotypically altered by the process, were specifically activated, and did not exhibit cytotoxic activity toward HLA-A*02+ kidney endothelial cells (ECs). We showed that A2-CAR CD8+ Tregs were more potent suppressors of immune responses induced by HLA-A*02 mismatch than control-CAR CD8+ Tregs, both in vitro and in vivo, in models of human skin graft rejection and graft-versus-host disease (GVHD) in NOD.Cg-PrkdcscidIl2rgtm1Wjl/SzJ (NSG) mice. We showed that integrity of human skin graft was preserved with A2-CAR CD8+ Tregs at least 100 days in vivo after administration, and that interaction between the A2-CAR CD8+ Tregs and HLA-A*02+ kidney ECs resulted in a fine-tuned and protolerogenic activation of the ECs without cytotoxicity. Together, our results demonstrated the relevance of the CAR engineering approach to develop antigen-specific CAR-CD8+ Tregs for clinical trials in transplantation, and potentially in other diseases

Expression of Heme Oxygenase-1 in Neural Stem/Progenitor Cells as a Potential Mechanism to Evade Host Immune Response

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MHC Class I Masking to Prevent AMR in a Porcine Kidney Transplantation Model in Alloimmunized Recipients

International audiencePresensitized patients awaiting a kidney transplant have a lower graft survival and a longer waiting time because of the limited number of potential donors and the higher risk of antibody-mediated rejection (AMR), particularly in the early posttransplant period, because of preformed donor-specific antibodies binding major histocompatibility complex (MHC) molecules expressed by the graft endothelium followed by the activation of the complement. Advances in kidney preservation techniques allow the development of ex vivo treatment of transplants. We hypothesized that masking MHC ex vivo before transplantation could help to prevent early AMR in presensitized recipients. We evaluated a strategy of MHC I masking by an antibody during ex vivo organ perfusion in a porcine model of kidney transplantation in alloimmunized recipients.Methods: Through the in vitro calcein-release assay and flow cytometry, we evaluated the protective effect of a monoclonal anti-swine leukocyte antigen class I antibody (clone JM1E3) against alloreactive IgG complement-dependent cytotoxicity toward donor endothelial cells. Kidneys perfused ex vivo with JM1E3 during hypothermic machine perfusion were transplanted to alloimmunized recipients.Results: In vitro incubation of endothelial cells with JM1E3 decreased alloreactive IgG cytotoxicity (mean complement-dependent cytotoxicity index [% of control condition] with 1 µg/mL 74.13% ± 35.26 [calcein assay] and 66.88% ± 33.46 [cytometry]), with high interindividual variability. After transplantation, acute AMR occurred in all recipients on day 1, with signs of complement activation (C5b-9 staining) as soon as 1 h after transplantation, despite effective JM1E3 binding on graft endothelium.Conclusions: Despite a partial protective effect of swine leukocyte antigen I masking with JM1E3 in vitro, ex vivo perfusion of the kidney with JM1E3 before transplantation was not sufficient alone at preventing or delaying AMR in highly sensitized recipients

The immune molecule CD3zeta and its downstream effectors ZAP-70/Syk mediate ephrin signaling in neurons to regulate early neuritogenesis

Recent studies have highlighted the key role of the immune protein CD3ζ in the maturation of neuronal circuits in the CNS. Yet, the upstream signals that might recruit and activate CD3ζ in neurons are still unknown. In this study, we show that CD3ζ functions early in neuronal development and we identify ephrinA1-dependent EphA4 receptor activation as an upstream regulator of CD3ζ. When newly born neurons are still spherical, before neurite extension, we found a transient CD3ζ aggregation at the cell periphery matching the initiation site of the future neurite. This accumulation of CD3ζ correlated with a stimulatory effect on filopodia extension via a Rho-GEF Vav2 pathway and a repression of neurite outgrowth. Conversely, cultured neurons lacking CD3ζ isolated from CD3ζ−/− mice showed a decreased number of filopodia and an enhanced neurite number. Stimulation with ephrinA1 induces the translocation of both CD3ζ and its activated effector molecules, ZAP-70/Syk tyrosine kinases, to EphA4 receptor clusters. EphrinA1-induced growth cone collapse was abrogated in CD3ζ−/− neurons and was markedly reduced by ZAP-70/Syk inhibition. Moreover, ephrinA1-induced ZAP-70/Syk activation was inhibited in CD3ζ−/− neurons. Altogether, our data suggest that CD3ζ mediates the ZAP-70/Syk kinase activation triggered by ephrinA-activated pathway to regulate early neuronal morphogenesis

SIRPγ-CD47 Interaction Positively Regulates the Activation of Human T Cells in Situation of Chronic Stimulation

International audienceA numerous number of positive and negative signals via various molecules modulate T-cell activation. Within the various transmembrane proteins, SIRPg is of interest since it is not expressed in rodents. SIRPg interaction with CD47 is reevaluated in this study. Indeed, wshow that the anti-SIRPg mAb clone LSB2.20 previously used by others has not beenappropriately characterized. We reveal that the anti-SIRPa clone KWAR23 is a Pan antiSIRP mAb which efficiently blocks SIRPa and SIRPg interactions with CD47. We show that SIRPg expression on T cells varies with their differentiation and while being expressed on Tregs, is not implicated in their suppressive functions. SIRPg spatial reorganization atthe immune synapse is independent of its interaction with CD47. In vitro SIRPa-g/CD47 blockade with KWAR23 impairs IFN-g secretion by chronically activated T cells. In vivo in a xeno-GvHD model in NSG mice, the SIRPg/CD47 blockade with the KWAR23 significantlydelays the onset of the xeno-GvHD and deeply impairs human chimerism. In conclusion, we have shown that T-cell interaction with CD47 is of importance notably inchronic stimulation

Expansion of natural CD8+Tregs for cell therapy

International audienceTregs play a critical role in the control of immune responses and tolerance induction; however our understanding of CD8+ Tregs is limited while they are particularly promising for therapeutic application. We previously reported that CD8+CD45RC[low] Tregs use IFNγ and IL-34 to suppress donor responses in a rat model of allotransplantation (Guillonneau et al, JCI, 2007; Bezie et al, JCI, 2015). Here, we aim to characterize human CD8+ Tregs to assess their potential for cell therapy in transplantation

Ex Vivo Expanded Human Non-Cytotoxic CD8+CD45RClow/-Tregs Efficiently Delay Skin Graft Rejection and GVHD in Humanized Mice

International audienceBoth CD4+and CD8+Tregs play a critical role in the control of immune responses and immune tolerance; however, our understanding of CD8+Tregs is limited while they are particularly promising for therapeutic application. We report here existence of highly suppressive human CD8+CD45RClow/-Tregs expressing Foxp3 and producing IFNγ, IL-10, IL-34, and TGFβ to mediate their suppressive activity. We demonstrate that total CD8+CD45RClow/-Tregs can be efficiently expanded in the presence of anti-CD3/28 mAbs, high-dose IL-2 and IL-15 and that such expanded Tregs efficiently delay GVHD and human skin transplantation rejection in immune humanized mice. Robustly expanded CD8+Tregs displayed a specific gene signature, upregulated cytokines and expansion in the presence of rapamycin greatly improved proliferation and suppression. We show that CD8+CD45RClow/-Tregs are equivalent to canonical CD4+CD25highCD127low/-Tregs for suppression of allogeneic immune responsesin vitro. Altogether, our results open new perspectives to tolerogenic strategies in human solid organ transplantation and GVHD

Generation of Immunodeficient Rats With Rag1 and Il2rg Gene Deletions and Human Tissue Grafting Models

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