ALBERT

Description: Janus kinase 2 (JAK2) signal transduction is a critical mediator of the immune response. JAK2 is implicated in the onset of graft-versus-host disease (GVHD), which is a significant cause of transplant-related mortality after allogeneic hematopoietic cell transplantation (allo-HCT). Transfer of JAK2−/− donor T cells to allogeneic recipients leads to attenuated GVHD yet maintains graft-versus-leukemia. Th1 differentiation among JAK2−/− T cells is significantly decreased compared with wild-type controls. Conversely, iTreg and Th2 polarization is significantly increased among JAK2−/− T cells. Pacritinib is a multikinase inhibitor with potent activity against JAK2. Pacritinib significantly reduces GVHD and xenogeneic skin graft rejection in distinct rodent models and maintains donor antitumor immunity. Moreover, pacritinib spares iTregs and polarizes Th2 responses as observed among JAK2−/− T cells. Collectively, these data clearly identify JAK2 as a therapeutic target to control donor alloreactivity and promote iTreg responses after allo-HCT or solid organ transplantation. As such, a phase I/II acute GVHD prevention trial combining pacritinib with standard immune suppression after allo-HCT is actively being investigated (https://clinicaltrials.gov/ct2/show/NCT02891603).

Description: We outline an approach to a unified equation of state for quark-hadron matter on the basis of a Φ − derivable approach to the generalized Beth-Uhlenbeck equation of state for a cluster decomposition of thermodynamic quantities like the density. To this end we summarize the cluster virial expansion for nuclear matter and demonstrate the equivalence of the Green’s function approach and the Φ − derivable formulation. As an example, the formation and dissociation of deuterons in nuclear matter is discussed. We formulate the cluster Φ − derivable approach to quark-hadron matter which allows to take into account the specifics of chiral symmetry restoration and deconfinement in triggering the Mott-dissociation of hadrons. This approach unifies the description of a strongly coupled quark-gluon plasma with that of a medium-modified hadron resonance gas description which are contained as limiting cases. The developed formalism shall replace the common two-phase approach to the description of the deconfinement and chiral phase transition that requires a phase transition construction between separately developed equations of state for hadronic and quark matter phases. Applications to the phenomenology of heavy-ion collisions and astrophysics are outlined.

Description: Graft-versus-host disease (GVHD) remains one of the major complications after allogeneic bone marrow transplantation (allo-BMT). Sirtuin-1 (Sirt-1) plays a crucial role in various biological processes including cellular senescence, metabolism, and inflammatory responses. Sirt-1 deacetylation regulates different transcription factors that are important for modulating immune responses. In the current study, we addressed the role of Sirt-1 in GVHD induction by employing Sirt-1 conditional knockout mice as well as a pharmacological Sirt-1 inhibitor. Using major histocompatibility complex (MHC)–mismatched and MHC-matched murine BMT models, we found that Sirt-1−/− T cells had a reduced ability to induce acute GVHD (aGVHD) via enhanced p53 acetylation. Sirt-1-deficient T cells also promoted induced regulatory T cell (iTreg) differentiation and inhibited interferon-γ production after allo-BMT. Sirt-1 deletion in iTregs increased Foxp3 stability and restrained iTreg conversion into pathogenic T cells. Furthermore, we found that administration with a Sirt-1 inhibitor, Ex-527, significantly improved recipient survival and clinical scores, with no signs of tumor relapse. These results indicate that Sirt-1 inhibition can attenuate GVHD while preserving the graft-versus-leukemia effect. Consistently, Sirt-1-deficient T cells also displayed a remarkably reduced ability to induce chronic GVHD (cGVHD). Mechanistic studies revealed that Sirt-1 deficiency in T cells enhanced splenic B-cell reconstitution and reduced follicular T helper cell development. Sirt-1 deficiency in T cells modulated donor B-cell responses reducing both B-cell activation and plasma cell differentiation. In addition, therapeutic Sirt-1 inhibition could both prevent cGVHD and reduce established cGVHD. In conclusion, Sirt-1 is a promising therapeutic target for the control of aGVHD and cGVHD pathogenesis and possesses high potential for clinical application.

Description: MicroRNAs (miRs) repress gene expression at the post-transcriptional level via binding target mRNAs subsequently promoting mRNA degradation or impeding translation. Certain miRs influence the survival, differentiation, and function of T cells in cancer, infections, and autoimmunity. Uncontrolled T-cell allogeneic responses contribute to chronic graft-versus-host disease (cGVHD), a major cause of non-relapse mortality following allogeneic hematopoietic stem-cell transplantation (allo-HCT). Dysregulation of miR-31 is implicated in cancer, but how miR-31 impacts allogeneic T-cell response is unclear. Using oligonucleotide array, we found miR-31 was dramatically up-regulated in T cells under alloantigen-driven vs. homeostatic proliferation in recipient mice following bone marrow transplantation (BMT) (Figure 1A-B). To understand how miR-31 regulates T-cell responses to alloantigens, we utilized murine models of allogeneic BMT and donor mice with miR-31 conditional knock-out on their T cells. In a sclerodermatous cGVHD model (B6→BDF1), we observed that the recipients transferred with donor T cells deficient for miR-31 exhibited significantly alleviated disease (Figure 1C), reflected by attenuated fibrosis and pathologic damage in skin. In a bronchiolitis obliterans cGVHD model (B6→B10.BR), we found that the recipients of miR-31-deficient T cells had reduced airway resistance, elastance (Figure 1D) and pathological damage in the lungs as compared with those of WT T cells. The role of miR-31 in promoting T-cell pathogenicity was further confirmed when miR-31 was inhibited by administration of specific antagomir (locked nuclear acid anti-miR-31). We used mass cytometry to analyze donor immune cell reconstitution in recipient spleens after BMT. Consistent with attenuated disease manifestation, the recipients of miR-31-deficient T cells displayed improved reconstitution of donor T- and B- lymphocytes. The follicular T helper cells (TFH) instruct germinal center (GC) B-cell expansion, affinity maturation, and plasma cell differentiation, whereas follicular regulatory T cells (TFR) inhibit TFH -mediated B-cell activation and antibody production. We found that miR-31 deficient T cells differentiated into more TFR, but fewer TFH during alloresponses. As a result, the differentiation and activation of GC B cells and the generation of plasma cells were attenuated in the recipients of miR-31-deficient T cells. Furthermore, miR-31-deficient T cells exhibited defects in proliferation and survival in allogeneic recipients, resulting in fewer donor T cells in recipient thymus, skin and lungs. In the absence of miR-31, T cells differentiated less into Th17 cells but more towards Tregs (Figure 1E) in vivo. Those miR-31-deficient Tregs expressed higher levels of Neuropilin 1 and PD-L1, the markers associated with superior stability and suppressive function of Tregs. While miR-31 played little role on Th1 cell differentiation, it facilitated alloantigen-reactive iTregs losing Foxp3 and producing IFNγ after being transferred into allogeneic recipients. Hypoxia, a hallmark of inflamed and damaged tissue, can drive fibrosis and disease development through immune cell dysregulation. Upon activation, T cells rapidly increase their metabolic rate and switch from oxidative phosphorylation to aerobic glycolysis. We found that miR-31-deficient T cells exhibited reduced hypoxia-inducible factor 1α (HIF1α) signaling (glycolysis promotor), surface GLUT1 expression, and glucose uptake, but increased lipid droplet accumulation in allogeneic recipients, suggesting that miR-31 promotes metabolic switch from fatty acid β-oxidation to aerobic glycolysis in allo-reactive T cells (Figure 1F). Furthermore, under hypoxia (3% oxygen) but not normoxia (21% oxygen) conditions, miR-31 increased Th17 but decreased iTreg differentiation from naïve CD4 T cells in the presence of IL-6 and TGFβ in vitro. Taken together, miR-31 regulates T-cell expansion, differentiation, and metabolism via promoting HIF1α expression and hypoxia adaptation in allo-reactive T cells, which enhances T-cell effector function and pathogenicity after allogeneic BMT. Disclosures No relevant conflicts of interest to declare.

Description: Allogeneic hematopoietic cell transplantation (allo-HCT) is an effective therapy for hematologic malignancies through T cell-mediated graft-versus-leukemia (GVL) effects, but allogeneic T cells often lead to severe graft-versus-host disease (GVHD). Cell metabolism plays pivotal roles in T-cell activation, differentiation, and function. However, understanding of T cell-metabolism is still superficial, and even less is known how metabolism regulates T-cell response to alloantigens and GVHD induction after allo-HCT. In this study, using a high-throughput liquid-and gas-chromatography-based metabolic approach, we compared the metabolic process of allogeneic versus syngeneic T cells at day 4 (early preclinical stage), day 7 (preclinical stage), and day 14 (clinical stage) post bone marrow transplantation (BMT), with naïve T cells as additional controls. Over 180 metabolites were identified and quantified. T cells after being transferred into pre-conditioned recipients were undergoing metabolic reprogramming reflected by attenuated levels of metabolites involving anabolic pathways of lipids, amino acids, nucleotides and carbohydrates in allogeneic and syngeneic T cells compared to those in naïve T cells. In comparison with syngeneic T cells, allogeneic T cells exhibited increased oxidative stress, reflected by higher levels of eicosanoid, cyclooxygenase, and lipoxygenase-oxidized eicosanoids, and decreased levels of antioxidant compounds such as glutathione (GSH) and glutathione disulfide (GSSG). To obtain biomass for robust proliferation followed by alloantigen stimulation, allogeneic T cells further increased pentose phosphate and polyamine synthesis by day 7 post-BMT. We also observed that allogeneic T cells and syngeneic T cells expressed comparable levels of metabolites in fatty acid and glutamine oxidized in tricarboxylic acid (TCA) cycle, which was much lower than those of naïve T cells. Importantly, allogeneic T cells exhibited higher levels of metabolites in glycolysis as compared to syngeneic T cells regardless of time points. Consistently, using Seahorse approach, we also found that allogeneic T cells significantly increased aerobic glycolysis as compared to syngeneic T cells post-BMT, whereas oxidative phosphorylation was similar. Moreover, blocking glycolysis with 2-deoxyglucose remarkably inhibited donor T-cell proliferation, expansion and Th1 differentiation after allo-BMT. Thus, aerobic glycolysis rather than mitochondrial oxidative phosphorylation is the preferential metabolic process required for the optimal expansion and activation of allogeneic T cells. Given mechanistic target of rapamycin (mTOR) plays an essential role in controlling T-cell metabolism particularly in glycolysis, we hypothesized that targeting mTOR would prevent GVHD by inhibiting glycolytic metabolism. Using pharmacological and genetic approaches, we unequivocally demonstrated that mTOR, especially mTORC1, was essential for T-cell glycolytic activity and for GVHD induction. Mechanistically, mTORC1 promoted T-cell activation, expansion, Th1 differentiation, and migration into GVHD target organs, but inhibited the generation of induced T regulatory cells. In conclusion, the current work provides compelling evidence that allogeneic T cells utilize glycolysis as a predominant metabolic process after BMT. Furthermore, we validate glycolysis or its key regulator, such as mTORC1, to be a valid therapeutic target for the control of GVHD. Disclosures: No relevant conflicts of interest to declare.

Description: The diversity and composition of T cell receptor (TCR) repertoire, which is the result of V, D and J gene recombination in TCR gene locus, has been found to impact immune responses in autoimmune and infectious diseases. The correlation of T-cell repertoire with the pathogenesis and outcome of graft-versus-host disease (GVHD) remain undefined. Here, by utilizing high-throughput sequencing of the gene encoding the TCRβ-chain, we comprehensively analyzed the profile of T-cell repertoire in host lymphoid and GVHD target organs after bone marrow transplantation (BMT). To understand whether T-cell repertoire is affected by different strength of alloantigen stimulation, we transferred same donor T cells derived from C57BL/6 (B6) mice into irradiated BALB/c (MHC-fully mismatched), B6D2F1 (MHC-haploidentical), BALB.b (MHC-matched ) and B6 recipients (syngeneic). Fourteen days later, T cells were isolated from recipient peripheral blood, spleen, peripheral lymphoid nodes (pLN), mesenteric lymphoid nodes (mLN), liver, lung, gut and skin for TCR sequencing. Clonality of donor T cells, which is inversely associated with TCR diversity, was significantly increased in either syngeneic or allogeneic recipients when compared with naïve donor T-cells, consistent with the concept that TCR diversity is reduced after T-cell activation and expansion. Increased TCR clonality was observed in lymphoid organs of allogeneic compared with syngeneic recipients, confirming that donor T cells were further activated in allogeneic recipients. However, decreased TCR clonality was observed in GVHD target organs of allogeneic compared with syngeneic recipients, suggesting that only limited donor T-cell clones were able to migrate in target organs in syngeneic compared to allogeneic recipients. The frequency of top clones in total productive rearrangements was increased in GVHD target organs especially liver of allogenic than syngeneic receipts. Interestingly, the frequency of top clones was positively associated with MHC disparity between donor and host, ranging from low to high in syngeneic, MHC-matched, haploidentical, and fully-mismatched recipients, respectively. To understand the extent to which TCR rearrangement is shared among different organs after BMT, we analyzed the overlap of TCR clones across different organs in the same recipients. T-cell clones were highly overlapping across organs, especially among GVHD target organs, in the same recipients after allogeneic BMT, although much lower overlapping in recipients after syngeneic BMT. The results suggest that alloantigen stimulation selectively activate certain T-cell clones and enrich antigen specific clones. On the other hand, much fewer shared clones were found among different recipients within the same group, regardless of MHC-disparity between donor and host. These results suggest that specific T-cell clones activated and expanded by alloantigens stimulation were highly different in individual recipients even with the same MHC-disparity between donor and host. Interestingly, the levels of clone overlapping were different in distinct organs among individual recipients. The level of T-cell clone overlapping was found high in liver of individual recipients regardless of the strength of alloantigen stimulation. The level of T cell clone overlapping was relatively high in pLNs and skin of the recipients after haploidentical BMT; whereas the level of T cell clone overlapping was relatively high in mLNs and gut of the recipients after MHC-matched BMT. These results suggest that skin may be a dominant target in haploidentical BMT and gut as a dominant target in MHC-matched BMT; whereas liver is a common target organ regardless. In conclusion, the current study establishes the association between MHC disparity, T-cell activation, and GVHD development in the level of donor T-cell repertoire. While TCR repertoire of donor T cells in peripheral blood or lymph nodes likely is representative in any individual recipient/patient, it is nearly impossible to identify T-cell clones that are pathogenic and shared among groups of recipients/patients even with the same MHC-disparity between donor and host. Disclosures No relevant conflicts of interest to declare.

Description: The successful treatment of hematologic malignances with allogeneic hematopoietic cell transplantation (allo-HCT) is limited by acute graft-versus-host disease (GvHD). The complement system has been shown to modulate adaptive immunity via interaction between complement activation products and their receptors expressed on both innate and adaptive immune cells. Complement receptors play an important role in pathogen and danger sensing by translating information gathered by complement fluid phase sensors into cellular responses. The anaphylatoxins, C3a and C5a, are key effector molecules of the complement system. C3aR/C5aR signaling plays an important role in the survival, maturation and differentiation of antigen presenting cells (APCs), as well as for effective antigen presentation to T cells and the subsequent modulation of T-cell proliferation, differentiation and function. Given that host APCs play a crucial role in priming alloreactive donor T cells to induce and intensify aGvHD, we evaluated the role of C3aR/C5aR in the induction of aGvHD via the regulation of host APC function. Using the two distinct well-defined, clinically relevant aGVHD models, B6 (H2b)-〉BALB/c (H2d) and FVB (H2q)-〉B6 (H2b), we observed that host C3aR/5aR deficiency led to a significantly reduced aGvHD as indicated by a higher survival rate and milder GvHD clinical scores as compared to WT recipients (Figure 1A). The ameliorated GVHD in C3aR/C5aR-/- recipients was associated with reduced donor T-cell activation, survival, bioenergetic capacity and Th1 differentiation, and with increased iTreg generation. Donor T cells in C3aR/C5aR-/- recipients express lower levels of chemokine receptors, CXCR3 and CCR6, which is likely responsible for the decreased migration of the effector T cells to GvHD target organs. Utilizing BM chimeras to distinguish the role of C3aR/C5aR on host hematopoietic cells vs. parenchymal tissues in the development of GVHD, we found that C3aR/C5aR expressed on recipient hematopoietic APCs was primarily responsible for donor T-cell response and pathogenicity in aGvHD. Among APCs, DCs are considered to be the most efficacious APCs due to their superior ability to take up antigen, express co-stimulatory molecules, and produce pro-inflammatory cytokines to polarize alloreactive T cells. C3aR/C5aR expression was drastically upregulated in DCs after total body irradiation. In comparison with WT DCs, irradiated C3aR/C5aR-/- DCs displayed higher apoptosis which is associated with DC upregulation of Fas expression, higher autophagy, and decreased activation and antigen presenting capacity reflected by lower IFN-γ positive DC cells and reduced MHCII expression. Notably, while C3aR/C5aR on hematopoietic cells was required for GVHD development, it was largely dispensable for the graft-versus-leukemia (GVL) effect. For translational application, we evaluated the effect of systemic administration of a combination of C3aR and C5aR antagonists (C3aRA/C5aRA) to block C3aR/C5aR signaling, on GVHD and GVL activity. We found that prophylactic treatment of recipients with C3aRA/C5aRA prior to transplant effectively prevented GvHD while preserving GVL effect (Figure 1B). Taken together, the current work provides a strong rationale and demonstrates the feasibility to target host C3aR/C5aR for the control of GVHD while preserving GVL activity after allo-HCT. Disclosures No relevant conflicts of interest to declare.

Description: Allogeneic hematopoietic cell transplantation (HCT) can cure a variety of benign and malignant hematopoietic disorders, but graft-versus-host disease (GVHD) remains a significant source of transplant-related mortality and morbidity. Mature T cells in donor stem cell graft are primarily responsible for the development of acute GVHD. PIM kinases are a family of serine/threonine kinases, including PIM1, PIM2 and PIM3, which are expressed following T-cell activation. The PIM kinases have been shown to inhibit apoptosis as well as to stimulate the cell metabolism and protein synthesis. In the current study, we investigated how PIM kinases regulate T-cell responses to alloantigens and GVHD development. Using genetically modified mice on an FVB background that are deficient for either single, double, or triple kinases of the PIM family, we evaluated the role of PIM kinases on T-cell alloresponses. T cells deficient for PIM1/PIM3 kinases had reduced survival and proliferation upon stimulation with alloantigens in vitro, whereas T cells without the PIM2 kinase displayed increased survival and IFNγ production as compared to WT T cells. After being transferred to lethally irradiated allogeneic mice in vivo, PIM1/PIM3 double knockout (KO) T cells had reduced expression of IFNγ in spleen, whereas PIM2 KO T cells showed decreased IL-4/5 expression, although similar IFNγ production when compared with WT T cells. These data suggest PIM2 kinase plays a distinct role by negatively regulating T-cell alloresponses. To test the role of PIM kinases on T-cell ability to induce GVHD, we transferred WT, PIM2 single KO, PIM1/PIM2 double KO, PIM1/PIM3 double KO, PIM2/PIM3 double KO, or PIM1/PIM2/PIM3 triple KO T cells together with WT bone marrow cells into lethally irradiated B6 mice. While PIM1/PIM3 double KO T cells induced milder GVHD, PIM2 KO T cells induced much more severe GVHD when compared to WT T cells. In addition, any types of T cells deficient for PIM2 caused significantly more severe GVHD than their PIM2-replete counterparts. Furthermore, restoration of PIM2 expression by gene transfection reduced the ability of PIM2-deficient T cells in the induction of GVHD. Enhanced pathogenicity of PIM2-deficient T cells was also confirmed in another murine model of allogeneic HCT. These results indicate that PIM2 plays a dominant role among PIM kinases in negatively regulating T-cell alloresponses and GVHD induction. To validate the data obtained from KO mice, we silenced the PIM2 kinase in PIM1/PIM3 KO T cells by administration of a PIM kinase pan-inhibitor (AZD, AstraZeneca R&D, Waltham, MA), and we observed exacerbated GVHD induced by PIM1/PIM3 KO T cells after PIM2 kinase silencing. Our study demonstrates the important result that PIM2 negatively regulates T-cell mediated alloresponse and GVHD development. The finding uncovers a novel biological function of PIM kinases as well as urges caution in inhibiting PIM kinases for the treatment of hematologic malignances in patients after allogeneic HCT. YW and AD contributed equally to this work. Disclosures No relevant conflicts of interest to declare.

Description: Janus kinase 2 (JAK2) signal transduction is a critical mediator of immune response. JAK2 activation promotes T-cell allosensitization, as well as Th1 and Th17 differentiation. JAK2-mediated STAT3 phosphorylation limits the generation of induced regulatory T cells (iTregs) by disrupting interactions between STAT5 and Foxp3. JAK2 is implicated in the onset of graft-versus-host disease (GVHD), which is a significant cause of transplant-related mortality after allogeneic hematopoietic cell transplantation (allo-HCT). Using murine models of allo-HCT we show here that transfer of donor JAK2-/- T cells is associated with significantly less GVHD, compared with wild-type or JAK2 replete donors (Figure 1, P =.003 and 0.01, respectively). Th1 differentiation among JAK2-/- T-cells is dramatically decreased, compared with controls. Conversely, iTreg polarization and stability are significantly increased among the JAK2 deficient T cells. To investigate the effect of pharmacologic JAK2 inhibition on T-cell alloresponses, pacritinib (supplied by CTI BioPharma), was chosen as it does not induce myelosuppression or increase risk for opportunistic infections in myelofibrosis patients - unlike JAK1/JAK2 inhibitors. Pacritinib potently inhibits JAK2, but also has suppressive activity toward JAK3, CSF1R, and IRAK1. Pacritinib was administered at 100mg/kg twice a day by oral gavage for 4 weeks beginning on the day of MHC-disparate allo-HCT, significantly reducing GVHD in recipient mice compared with methylcellulose vehicle control. In allogeneic mixed leukocyte reactions using human cells, pacritinib (2.5μM) significantly reduces T-cell proliferation after 5 days of culture (P

Description: Graft-versus-host disease (GVHD) remains a life threatening complication after allogeneic hematopoietic stem cell transplantation (HCT). Donor T cells are the key pathogenic effectors in the induction of GVHD. MicroRNAs (miRs) have been shown to play an important role in orchestrating immune response, among which miR-17-92 cluster is one of the best characterized miR clusters that encodes 6 miRs including 17, 18a, 19a, 20a, 19b-1 and 92-1. Although regulatory functions of miR-17-92 cluster have been elaborated in a variety of immune responses including anti-infection, anti-tumor, and autoimmunity, the role of this miR cluster in the modulation of T-cell response to alloantigens and the development of GVHD has not been explored previously. Based on the previous report that miR-17-92 promotes Th1 responses and inhibits induced regulatory T-cell (iTreg) differentiation in vitro, we hypothesized that blockade of miR-17-92 would constrain T-cell alloresponse and attenuate GVHD. To evaluate the function of miR-17-92 on T-cell alloresponse, we utilized the mice with miR-17-92 conditional knock-out (KO) on T cells as donors, and compared the alloresponse of WT and KO T cells after allogeneic bone marrow transplantation (allo-BMT). We observed that KO T cells had substantially reduced ability to proliferate and produce IFNγ as compared to WT counterparts 4 days after cell transfer. Interestingly, CD4 but not CD8 KO T cells had increased cell death in the population of fast-dividing T cells. Thus, miR-17-92 cluster promotes activation and expansion of both CD4 and CD8 T cells, and inhibits activation-induced cell death of CD4 but not CD8 T cells at the early stage of alloresponse in vivo. We further evaluated the role of miR-17-92 on T cells in the development of acute GVHD in a fully MHC-mismatched BMT model. In sharp contrast to WT T cells that caused severe GVHD and resulted in 100% mortality of the recipients, KO T cells were impaired in causing severe GVHD reflected by mild clinical manifestations and no mortality. These observations were extended to MHC-matched but minor antigen-mismatched as well as haploidentical BMT models that are more clinically relevant. We next addressed the critical question whether T cells deficient for miR-17-92 are still capable of mediating graft-versus-leukemia (GVL) effect. Using A20 lymphoma and P815 mastocytoma cell lines, we demonstrated that the KO T cells essentially retained the GVL activity in MHC-mismatched and haploidentical BMT model, respectively. Mechanistic studies revealed that miR-17-92 promoted CD4 T-cell proliferation, survival, migration to target organs, and Th1-differentiation, but reduced Th2-differentiation and iTreg generation. However, miR-17-92 had less impact on CD8 T-cell proliferation, survival, IFNγ production, and cytolytic activity reflected by granzyme B and CD107a expression. Moreover, miR-17-92 negatively regulated TNFα production by both CD4 and CD8 T cells. We therefore conclude that miR-17-92 cluster is required for T cells to induce severe GVHD, but it is dispensable for T cells to mediate the GVL effect. To increase translational potential of our findings, we designed the locked nucleic acid (LNA) antagomirs specific for miR-17 or miR-19, which have been reported to be the key members in this cluster. We observed that the treatment with anti-miR-17 significantly inhibited T-cell expansion and IFNγ production in response to alloantigen in vivo, and anti-miR-19 was more effective. Furthermore, our ongoing experiment showed the treatment with anti-miR-17 or anti-miR-19 was able to considerably attenuate the severity of GVHD as compared to scrambled antagomir in a MHC-mismatched BMT model. Taken together, the current work reveals that miR-17-92 cluster is essential for T-cell alloresponse and GVHD development, and validates miR-17-92 cluster as promising therapeutic target for the control of GVHD while preserving GVL activity in allogeneic HCT. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.