Graft-versus-host Disease Model Research Articles

The effect of ADAMTS13 on graft-versus-host disease.

Allogeneic haematopoietic stem cell transplantation (allo-HSCT) can potentially cure malignant blood disorders and benign conditions such as haemoglobinopathies and immunologic diseases. However, allo-HSCT is associated with significant complications. The most common and debilitating among them is graft-versus-host disease (GVHD). In GVHD, donor-derived T cells mount an alloimmune response against the recipient. The alloimmune response involves several steps, including recognition of recipient antigens, activation and proliferation of T cells in secondary lymphoid organs, and homing into GVHD-targeted organs. Adhesion molecules on T cells and endothelial cells mediate homing of T cells into lymphoid and non-lymphoid tissues. In this study, we showed that Von Willebrand factor (VWF), an adhesion molecule secreted by activated endothelial cells, plays an important role in mouse models of GVHD. We investigated the effect of the VWF-cleaving protease ADAMTS13 on GVHD. We found that ADAMTS13 reduced the severity of GVHD after bone marrow transplantation from C57BL6 donor to BALB/C recipient mice. A recombinant VWF-A2 domain peptide also reduced GVHD in mice. We showed that ADAMTS13 and recombinant VWF-A2 reduced the binding of T cells to endothelial cells and VWF invitro, and reduced the number of T cells in lymph nodes, Peyer's patches and GVHD-targeted organs invivo. We identified LFA-1 (αLβ2) as the binding site of VWF on T cells. Our results showed that blocking T-cell homing by ADAMTS13 or VWF-A2 peptide reduced the severity of the GVHD after allo-HSCT, a potentially novel method for treating and preventing GVHD.

Human amniotic epithelial stem cell is a cell therapy candidate for preventing acute graft-versus-host disease.

Graft-versus-host disease (GVHD), an immunological disorder that arises from donor T cell activation through recognition of host alloantigens, is the major limitation in the application of allogeneic hematopoietic stem cell transplantation (allo-HSCT). Traditional immunosuppressive agents can relieve GVHD, but they induce serious side effects. It is highly required to explore alternative therapeutic strategy. Human amniotic epithelial stem cells (hAESCs) were recently considered as an ideal source for cell therapy with special immune regulatory property. In this study, we evaluated the therapeutic role of hAESCs in the treatment of GVHD, based on our previous developed cGMP-grade hAESCs product. Humanized mouse model of acute GVHD (aGVHD) was established by injection of huPBMCs via the tail vein. For prevention or treatment of aGVHD, hAESCs were injected to the mice on day -1 or on day 7 post-PBMC infusion, respectively. We showed that hAESCs infusion significantly alleviated the disease phenotype, increased the survival rate of aGVHD mice, and ameliorated pathological injuries in aGVHD target organs. We demonstrated that hAESCs directly induced CD4+ T cell polarization, in which Th1 and Th17 subsets were downregulated, and Treg subset was elevated. Correspondingly, the levels of a series of pro-inflammatory cytokines were reduced while the levels of the anti-inflammatory cytokines were upregulated in the presence of hAESCs. We found that hAESCs regulated CD4+ subset polarization in a paracrine mode, in which TGFβ and PGE2 were selectively secreted to mediate Treg elevation and Th1/Th17 inhibition, respectively. In addition, transplanted hAESCs preserved the graft-versus-leukemia (GVL) effect by inhibiting leukemia cell growth. More intriguingly, hAESCs infusion in HSCT patients displayed potential anti-GVHD effect with no safety concerns and confirmed the immunoregulatory mechanisms in the preclinical study. We conclude that hAESCs infusion is a promising therapeutic strategy for post-HSCT GVHD without compromising the GVL effect. The clinical trial was registered at www.clinicaltrials.gov as #NCT03764228.

Interleukin-27 Promotes the Generation of Myeloid-derived Suppressor Cells to Alleviate Graft-versus-host Disease.

Stimulation of myeloid-derived suppressor cell (MDSC) formation represents a potential curative therapeutic approach for graft-versus-host disease (GVHD), which significantly impacts the prognosis of allogeneic hematopoietic stem cell transplantation. However, the lack of an effective strategy for inducing MDSC production in vivo has hindered their clinical application. In our previous study, MDSC expansion was observed in interleukin (IL)-27-treated mice. In this study, we overexpressed exogenous IL-27 in mice using a recombinant adeno-associated virus vector to investigate its therapeutic and exacerbating effects in murine GVHD models. In our study, we demonstrated that exogenous administration of IL-27 significantly suppressed GVHD development in a mouse model. We found that IL-27 treatment indirectly inhibited the proliferation and activation of donor T cells by rapidly expanding recipient and donor myeloid cells, which act as MDSCs after irradiation or under inflammatory conditions, rather than through regulatory T-cell expansion. Additionally, IL-27 stimulated MDSC expansion by enhancing granulocyte-monocyte progenitor generation. Notably, we verified that IL-27 signaling in donor T cells exerted an antagonistic effect on GVHD prevention and treatment. Further investigation revealed that combination therapy involving IL-27 and T-cell depletion exhibited remarkable preventive effects on GVHD in both mouse and xenogeneic GVHD models. Collectively, these findings suggest that IL-27 promotes MDSC generation to reduce the incidence of GVHD, whereas targeted activation of IL-27 signaling in myeloid progenitors or its combination with T-cell depletion represents a potential strategy for GVHD therapy.

Extracellular release of damaged mitochondria induced by prehematopoietic stem cell transplant conditioning exacerbates GVHD

AbstractDespite therapeutic advancements, graft-versus-host disease (GVHD) is a major complication of hematopoietic stem cell transplantation (HSCT). In current models of GVHD, tissue injury induced by cytotoxic conditioning regimens, along with translocation of microbes expressing pathogen-associated molecular patterns, result in activation of host antigen-presenting cells (APCs) to stimulate alloreactive donor T lymphocytes. Recent studies have demonstrated that in many pathologic states, tissue injury results in the release of mitochondria from the cytoplasm to the extracellular space. We hypothesized that extracellular mitochondria, which are related to archaebacteria, could also trigger GVHD by stimulation of host APCs. We found that clinically relevant doses of radiation or busulfan induced extracellular release of mitochondria by various cell types, including cultured intestinal epithelial cells. Conditioning-mediated mitochondrial release was associated with mitochondrial damage and impaired quality control but did not affect the viability of the cells. Extracellular mitochondria directly stimulated host APCs to express higher levels of major histocompatibility complex II (MHC-II), costimulatory CD86, and proinflammatory cytokines, resulting in increased donor T-cell activation, and proliferation in mixed lymphocyte reactions. Analyses of plasma from both experimental mice and a cohort of children undergoing HSCT demonstrated that conditioning induced extracellular mitochondrial release in vivo. In mice undergoing MHC-mismatched HSCT, administration of purified syngeneic extracellular mitochondria increased host APC activation and exacerbated GVHD. Our data suggest that pre-HSCT conditioning results in extracellular release of damaged mitochondria, which increase alloreactivity and exacerbate GVHD. Therefore, decreasing the extracellular release of damaged mitochondria after conditioning could serve as a novel strategy for GVHD prevention.

Type 2 cannabinoid receptor expression on microglial cells regulates neuroinflammation during graft-versus-host disease.

Neuroinflammation is a recognized complication of immunotherapeutic approaches such as immune checkpoint inhibitor treatment, chimeric antigen receptor therapy, and graft versus host disease (GVHD) occurring after allogeneic hematopoietic stem cell transplantation. While T cells and inflammatory cytokines play a role in this process, the precise interplay between the adaptive and innate arms of the immune system that propagates inflammation in the central nervous system remains incompletely understood. Using a murine model of GVHD, we demonstrate that type 2 cannabinoid receptor (CB2R) signaling plays a critical role in the pathophysiology of neuroinflammation. In these studies, we identify that CB2R expression on microglial cells induces an activated inflammatory phenotype that potentiates the accumulation of donor-derived proinflammatory T cells, regulates chemokine gene regulatory networks, and promotes neuronal cell death. Pharmacological targeting of this receptor with a brain penetrant CB2R inverse agonist/antagonist selectively reduces neuroinflammation without deleteriously affecting systemic GVHD severity. Thus, these findings delineate a therapeutically targetable neuroinflammatory pathway and have implications for the attenuation of neurotoxicity after GVHD and potentially other T cell-based immunotherapeutic approaches.

The IL-6 signaling pathway contributes critically to the immunomodulatory mechanism of human decidua-derived mesenchymal stromal cells

Human bone marrow-derived mesenchymal stromal cells (BM-MSCs) have been proposed as a treatment for graft-versus-host disease (GVHD), which is a major complication following allogeneic hematopoietic cell transplantation. However, clinical trials have not yielded good results, and human decidua-derived mesenchymal stromal cells (DSCs) have been proposed as an alternative. In addition, the mechanism by which DSCs exert their immunomodulatory effects is still unknown. We found that knockdown of IL-6 in DSCs reduced the expression of PD-L1 and PD-L2, which are known as classical immune checkpoint inhibitors. Expression of PD-L1 and PD-L2 was restored by adding recombinant IL-6 to the DSCs. When DSCs and IL-6-knockdown DSCs were administered as treatment in a murine GVHD model, the group receiving IL-6-knockdown DSCs had significantly higher mortality and clinical scores compared to the group receiving DSCs. Taken together, these data suggest that the IL-6 signaling pathway is a crucial contributor to the immunosuppressive capacity of DSCs.

The road to refractory graft-versus-host disease is paved with good intentions.

Refractory acute graft-versus-host disease (GVHD) occurs when the immune injury exceeds the capacity of injured tissues to regenerate and repair. While glucocorticoids have been used for decades to treat GVHD, Arnhold, Chang, and colleagues in this issue of the JCI question whether this approach can in fact be counterproductive. Using in vivo experimental models of GVHD and in vitro intestinal organoids, the study authors show that glucocorticoid exposure directly impeded small intestinal epithelial proliferation and survival, thus preventing the resolution of injury. These findings suggest that future treatment approaches for acute GVHD should include measures to reduce immune reactivity as well as interventions to actively promote tissue resilience.

Sigle Agent of Posttransplant Cyclophosphamide Without Calcineurin Inhibitor Controls Severity of Experimental Chronic GVHD.

Chronic graft-versus-host disease (GVHD) is a major cause of late death and morbidity following allogeneic hematopoietic cell transplantation (HCT), but its pathogenesis remains unclear. Recently, haplo-identical HCT with post-transplant cyclophosphamide (Haplo-HCT with PTCY) was found to achieve a low incidence rate of acute GVHD and chronic GVHD. However, while the pathogenesis of acute GVHD following Haplo-HCT with PTCY has been well investigated, that of chronic GVHD remains to be elucidated, especially in HLA-matched HCT with PTCY. Based on its safety profile, PTCY is currently applied for the human leucocyte antigen (HLA)-matched HCT setting. Here, we investigated the mechanisms of chronic GVHD following HLA-matched HCT with PTCY using a well-defined mouse chronic GVHD model. PTCY attenuated clinical and pathological chronic GVHD by suppressing effector T-cells and preserving regulatory T-cells compared with a control group. Additionally, we demonstrated that cyclosporine A (CsA) did not show any additional positive effects on attenuation of GVHD in PTCY-treated recipients. These results suggest that monotherapy with PTCY without CsA could be a promising strategy for the prevention of chronic GVHD following HLA-matched HCT.

Post-Transplant Cyclophosphamide Combined with Brilliant Blue G Reduces Graft-versus-Host Disease without Compromising Graft-versus-Leukaemia Immunity in Humanised Mice.

Allogeneic haematopoietic stem cell transplantation (HSCT) leads to the establishment of graft-versus-leukaemia (GVL) immunity, but in many cases also results in the development of graft-versus-host disease (GVHD). This study aimed to determine if P2X7 antagonism using Brilliant Blue G (BBG) could improve the beneficial effects of post-transplant cyclophosphamide (PTCy) in a humanised mouse model of GVHD, without comprising GVL immunity. NOD.Cg-Prkdcscid Il2rgtm1Wjl (NSG) mice were injected with human peripheral blood mononuclear cells (PBMCs) (Day 0), then with cyclophosphamide (33 mg/kg) on Days 3 and 4, and with BBG (50 mg/kg) (or saline) on Days 0-10. PTCy with BBG reduced clinical GVHD development like that of PTCy alone. However, histological analysis revealed that the combined treatment reduced liver GVHD to a greater extent than PTCy alone. Flow cytometric analyses revealed that this reduction in liver GVHD by PTCy with BBG corresponded to an increase in human splenic CD39+ Tregs and a decrease in human serum interferon-γ concentrations. In additional experiments, humanised NSG mice, following combined treatment, were injected with human THP-1 acute myeloid leukaemia cells on Day 14. Flow cytometric analyses of liver CD33+ THP-1 cells showed that PTCy with BBG did not mitigate GVL immunity. In summary, PTCy combined with BBG can reduce GVHD without compromising GVL immunity. Future studies investigating P2X7 antagonism in combination with PTCy may lead to the development of novel treatments that more effectively reduce GVHD in allogeneic HSCT patients without promoting leukaemia relapse.

CRISPR/Cas9 deletion of MIR155HG in human T cells reduces incidence and severity of acute GVHD in a xenogeneic model

AbstractAcute graft-versus-host disease (GVHD) is a major complication of allogeneic hematopoietic cell transplantation (allo-HCT). Using preclinical mouse models of disease, previous work in our laboratory has linked microRNA-155 (miR-155) to the development of acute GVHD. Transplantation of donor T cells from miR-155 host gene (MIR155HG) knockout mice prevented acute GVHD in multiple murine models of disease while maintaining critical graft-versus-leukemia (GVL) response, necessary for relapse prevention. In this study, we used clustered, regularly interspaced, short palindromic repeats (CRISPR)/Cas9 genome editing to delete miR-155 in primary T cells (MIR155HGΔexon3) from human donors, resulting in stable and sustained reduction in expression of miR-155. Using the xenogeneic model of acute GVHD, we show that NOD/SCID/IL2rγnull (NSG) mice receiving MIR155HGΔexon3 human T cells provide protection from lethal acute GVHD compared with mice that received human T cells with intact miR-155. MIR155HGΔexon3 human T cells persist in the recipients displaying decreased proliferation potential, reduced pathogenic T helper–1 cell population, and infiltration into GVHD target organs, such as the liver and skin. Importantly, MIR155HGΔexon3 human T cells retain GVL response significantly improving survival in an in vivo model of xeno-GVL. Altogether, we show that CRISPR/Cas9–mediated deletion of MIR155HG in primary human donor T cells is an innovative approach to generate allogeneic donor T cells that provide protection from lethal GVHD while maintaining robust antileukemic response.

Dual Functions of Mitochondrial Calcium Uniporter in T Cell Alloimmunity

Despite pharmacological prophylaxis using calcineurin inhibitors, graft-versus-host disease (GVHD) still occurs in patients undergoing allogeneic hematopoietic stem cell transplantation. However, the mechanism that underlies the breakthrough of alloreactive T cell responses following calcium signaling inhibition remains poorly defined. The mitochondrial calcium uniporter (MCU), which is located in the inner mitochondrial membrane, controls Ca2+ uptake into the mitochondria matrix. Past dogma suggested that lack of mitochondria calcium uptake would compromise T cell immune response due to suboptimal NFAT activation upon TCR ligation. However, the exact role of MCU in the regulation of alloreactive T cell responses has not been previously determined. Here, we demonstrate dual functions of MCU in alloreactive T cell response and GVHD maintenance, highlighting MCU as a potential novel target to manipulate T cell alloreactivity. Using T cell-specific Mcu conditional knockout C57/BL6 (B6) mice (Mcu-cKO), we found that compared to WT T cells, B6 Mcu-cKO T cells induced less severe GVHD in Balb/c mice, with prolonged survival and significantly lower number of donor effector cells in the spleen and liver early after transplantation. Surprisingly, these Mcu-cKO T cell recipients developed severe liver GVHD by 60 days after transplantation, as evidenced by extensive lymphocytic infiltration in the liver, while to a lesser extent in the skin and intestine in these GVHD mice. Flow cytometric analysis of donor T cells, which were harvested between 5 and 8 weeks after transplantation, showed that Mcu-cKO T cells retained the IFN-g- and GM-CSF-producing capacity, but acquired stronger capacity of producing the cytotoxic molecule granzyme B. To comprehensively delineate the role of MCU in allogeneic T cell response, we used MHC-identical but minor histocompatibility antigen (miHA)-mismatched B6-to-Balb/b GVHD model, in which alloreactive CD8+ T cells can be identified with H60 peptide/MHC class-I dimer staining. Similarly, loss of Mcu in T cells caused less severe GVHD, attributed to the decreased number of H60+CD8+ effector T cells that showed impaired proliferation capacity. RNA-seq analysis of liver-infiltrating H60+CD8+ T cells revealed that Mcu ablation resulted in decreased expression of cell proliferation genes (Pclaf, Cdc45, Top2a, Cdca8, etc), increased expression of genes (Cd7, Bcl2, CD96, Eomes, Ezh1, etc) associated with memory T cells. These results demonstrated that Mcu is required for the expansion of alloreactive T cells, but restricts their memory-associated transcriptional programs during GVHD maintenance. Further characterization showed these alloreactive Mcu-cKO T cells produced higher levels of tissue migration molecules (CCR9, CCR5, etc) and lower death molecule (Lpin1) than their WT counterparts. Using gain-of-function strategy of retroviral Mcu overexpression in T cells (McuOE), we found McuOE CD8+ T cells displayed enhanced effector differentiation represented by higher expression of effector molecules (Ifng), decreased expression of stemness and memory associated molecules (Tcf7, Id3), and reduced expression of migration molecules (CCR9, CXCR3, etc). The cultured McuOE CD8+ T cells contracted earlier than WT. These results were further validated in vivo using the B6-to-Balb/c GVHD model. These data demonstrate a negative regulatory role of MCU in the tissue migration and persistence of alloreactive T cells. Notably, human T cells from patients with severe GVHD produced lower levels of MCU protein compared to that of non-GVHD patients. Our findings identified for the first time the dual functions of MCU in the regulation of T cell alloimmunity. MCU-mediated mitochondria calcium uptake promotes early expansion of alloreactive T cells but restricts the expression of memory-associated gene programs and tissue migration molecules. Strategies of enhancing MCU functionality in alloreactive T cells could potentially reduce their memory potential and tissue infiltration capacity, thereby reducing GVHD.

Hspa5 Deficiency Blocks Intestinal Enterocyte Differentiation in Graft-Versus-Host Disease

Background: Allogeneic hematopoietic stem cell transplantation (allo-HSCT) has been established as an effective therapy for hematological malignancies. Graft-versus-host disease (GVHD) is a life-threatening complication, and the intestine is one of the major sites affected. Currently, immunosuppressive agents remain the preferred choice for GVHD treatment. However, treatment resistance still occurs in a large population, indicating that some tissue damage may be irreversible. Methods: The murine transplant and GVHD model were established as previously described. To characterize the intestinal damage mediated by radiation and GVHD, murine small intestine tissues were collected at day 14 after transplantation. Primary small intestinal crypts were isolated from each group and cultured for five consecutive days to evaluate their ability to proliferate and differentiate. Single-Cell analysis was performed to characterize the impaired intestinal repair after injury. Results: At day 14, the villus-to-crypt ratio was partially recovered in the BM group, but remained imbalanced in the GVHD group. We observed a significant decrease in the expression of Reg1, a gene expressed by enterocytes (EC), in the GVHD groups compared to the BM group. we further utilized a 3D organoid model to investigate intestinal growth and differentiation. The organoid size from the GVHD group was comparable to the BM and control groups. However, the number of buds per organoid was significantly reduced in the GVHD group compared to the BM and control groups. Immunofluorescence staining confirmed that cells in GVHD-derived organoids exhibited high proliferation (stained by Mki67) but impaired differentiation of enterocyte (stained by Aldob). To gain insights into the cellular mechanisms influencing enterocyte differentiation, we dissociated murine small intestinal tissues from each group into single cells and sequenced them using the 10X Genomics platform. Through pseudochronological analysis, each cell was ordered along the predicted lineages and assigned a pseudotime. We found that enterocytes in GVHD exhibited a long and discontinuous trajectory, suggesting explicit blockage of EC differentiation. Functional enrichment analysis showed that pathways related to cell growth and differentiation, such as MAPK, ERBB, and inositol phosphate metabolism, were highly enriched in M2 of the control and BM groups. In contrast, MAPK was dramatically downregulated at the early stage of ISC differentiation in the GVHD group. Next, we analyzed the differentially expressed genes in EP between the GVHD and BM groups. Endoplasmic reticulum (ER) chaperone-related genes from the heat shock protein (Hsp) 70 family (Hspa1a/1b/5), Hsp90 family (Hsp90aa1/ab1), and Hsp40 family (Dnajb1) were significantly decreased in GVHD compared to BM. Notably, Hspa5 (also known as GRP78 or Bip), which serves as a sensor of glucose levels and misfolded proteins, exhibited reduced protein levels, along with decreased IRE1ɑ phosphorylation (p-IRE1ɑ) and Xbp1s, as well as decreased PERK phosphorylation (p-PERK) and ATF6 expression. To validate our conjecture, we utilized small intestinal organoids cultured for 3 days for further experimentation. RT-qPCR demonstrated that energy restriction downregulated the mRNA expression of Hspa5 and other chaperones. Furthermore, we treated intestinal organoids with HA15, a BIP inhibitor, which resulted in significantly enlarged area but fewer buds. Consistent with our previous findings, Hspa5 was downregulated in the HA15-treated group, along with decreased expression of Hsp family and enterocyte markers. Since Hsp family plays key roles in restoring cellular homeostasis, we wondered if upregulating Hspa5 could protect intestinal cells from outside stimuli such as pro-inflammatory cytokines. When intestinal organoids were cocultured with IFN-g, we found that Bix, the selective Bip inducer, protected organoids from apoptosis by increasing Hsp70 expression. Conclusion: Given that immunosuppression partly resolves GVHD, strategies aimed at restoring intestinal homeostasis should be given sufficient attention. Our study reveals that intestinal enterocyte differentiation is blocked in GVHD, possibly due to starvation and energy restriction. Deficiency in Hspa5 results in impaired intestinal repair, and increasing Hsp levels may enhance cell resistance to cytokine storms.

Janus Kinase (JAK) 1 Inhibition Results in Significant Changes in Serum Proteins and Peripheral T-Cell Populations That Correlated with Clinical Scores in Chronic Graft Versus Host Disease (GVHD) Patients (an Analysis from GRAVITAS-309)

Background: Chronic GVHD (cGVHD) occurs in 30-70% of allogeneic hematopoietic cell transplantation patients, and the rate has increased over the past 2 decades. Based on the degree of organ involvement, cGVHD is classified as mild, moderate, or severe. Standard treatment includes systemic corticosteroids (CS), together with immunosuppressive agents. GRAVITAS-309 (NCT03584516) was designed as a 2-part, multicenter, randomized trial to assess efficacy and safety of itacitinib, an orally bioavailable, selective JAK1 inhibitor, in combination with CS as first-line treatment for moderate to severe cGVHD. The dose-finding, open-label, randomized portion of the study initially investigated itacitinib at 200 mg once daily (qd) and 300 mg qd in combination with CS (methylprednisolone or prednisone); both doses were well tolerated. The trial was expanded to test itacitinib 400 mg qd and 300 mg twice daily (bid); the initial 300 mg qd cohort was expanded and a CS monotherapy cohort was added. Results from the expanded portion of the study (n=139 patients) showed improved overall response rate (ORR) at 6 months in patients treated with itacitinib + CS vs CS alone (Im, et al. Blood 2022;140[Suppl 1]:1870). Here, we analyzed samples collected from patients in 4 cohorts (cohort A [300 mg qd], cohort B [400 mg qd], cohort C [300 mg bid], and cohort D [CS alone]) for systemic proteins and immune cell populations, to support investigation into the itacitinib mechanism of action and to correlate with clinical outcomes. Methods: Peripheral blood mononuclear cells (PBMCs) and serum were collected before treatment (baseline, day 1), and day 7, day 14 (PBMCs only), and day 28 following treatment initiation. Serum proteins were analyzed using the OLINK Target 96 platform, and circulating T-cell subsets were measured using flow cytometry of PBMCs and presented as a percentage of parent population. Samples were assessed irrespective of patients' response. Most of the patients (70-100% per cohort) with samples available for analysis were responders (achieved complete or partial responses). Results: Serum levels of proteins, including several proposed as potential prognostic cGVHD biomarkers, changed significantly at day 28 relative to baseline following treatment with itacitinib (Table 1). Levels of elafin, a marker of acute GVHD of the skin, were significantly reduced and levels of dickkopf-3 (DKK3), a marker of sclerotic and nonsclerotic cGVHD, were significantly increased in itacitinib cohorts only. Based on a repeated measures correlation analysis, both markers significantly correlated with overall clinical skin scores (elafin: r=+0.43; DKK3: r=-0.53; both P<0.001). Serum levels of other reported markers of cGVHD, including osteopontin, C-X-C motif chemokine ligand (CXCL) 9 and CXCL10, were significantly decreased exclusively in itacitinib-treated cohorts, and not in the CS only cohort. Some proteins, including matrix metalloproteinase (MMP) 3, increased in all cohorts, suggesting that changes in these proteins cannot be attributed to itacitinib alone, but may reflect response to CS; other proteins, such as suppression of tumorigenicity (ST2), remained unchanged in response to treatment in all cohorts. CS treatment alone resulted in an increase in naive CD4 T cells (CD4 +CD8 ->CD45RA +CCR7 -) and a corresponding reduction of CD4 effector memory T cells (CD4 +CD8 ->CD45RA -CCR7 +) within 28 days (Figure 1, cohort D). Changes in naive CD4 T cells following CS monotherapy were significantly attenuated by itacitinib ( P<0.05 vs CS at day 28), particularly at the 400 mg qd dose (Figure 1, cohort B), which demonstrated the best ORR at 6 months (53% with 400 mg qd vs 36% with CS). Conclusions: Analysis of patient samples from GRAVITAS-309 revealed that serum elafin and DKK3 levels significantly correlated with skin GVHD scores, possibly reflecting the systemic origin of observed skin manifestations. Serum levels of osteopontin, CXCL9, and CXCL10 were specifically reduced by itacitinib in patients with cGVHD and may represent potential pharmacodynamic markers. Observed changes in different peripheral T-cell populations in patients' samples following itacitinib treatment were consistent with those reported in murine GVHD models, suggesting a potential role of naive CD4 + T cells in driving this disease. Planned future analyses will include identification of novel biomarkers that correlate with organ involvement.

Inflammatory Memory Restrains Intestinal Stem Cell (ISC) Regeneration after Allogeneic Stem Cell Transplantation (SCT)

Introduction: Intestinal stem cells (ISCs) are responsible for the remarkable ability to maintain intestinal epithelium homeostasis and regeneration throughout life. Inflammatory damage of ISCs underpins injury caused by graft-versus-host disease (GVHD), inflammatory bowel diseases (IBD) and immune check-point blocker mediated colitis. However, it remains unknown whether the ISCs that survive or tolerate inflammation are fully functional and can return to their full functionality after the resolution of ongoing inflammatory insults. Herein we investigated the consequences of inflammation from GVHD on Lgr5+ISCs in multiple well-defined clinically relevant models of gastro-intestinal acute graft-versus-host disease (GI GVHD). Methods: We utilized single cell RNA (scRNA) sequencing to assess transcriptomics, Assay of transposase-accessible chromatin sequencing (ATAC-seq) to assess epigenomics, and functional metabolomics of ISCs in clinically relevant in vivo models of GVHD after major histocompatibility complex (MHC)-disparate BALB/c→C57BL/6 (B6) and MHC matched minor mismatched C3H.sw→B6 models of allogeneic SCT. Ex vivo intestinal organoids cultures, mitochondrial, and functional biochemical assays were utilized to determine the biological relevance of the changes observed from the ‘omic’ analyses and further validated them in vivo by developing novel Lgr5 +ISC specific succinate dehydrogenase A (SDHA) knock-out mice. Results: We examined the transcriptomes of Lgr5+ISCs with scRNA-seq of the intestinal crypts harvested from MHC-disparate BALB/c→B6 recipients on day +7 after allogeneic SCT. Bioinformatic analyses demonstrated upregulation of interferon and inflammation response genes but significant downregulation of genes involved in mitochondrial function, its complexes including complex II (SDH), ATP metabolic process, OXPHOS, and cytoplasmic translation. To assess the impact of metabolic functional gene changes, we harvested and assessed ISCs in ex vivo organoid cultures from transplanted recipients in the absence of ongoing inflammation. The ISCs harvested from GVHD animals demonstrated significantly reduced regeneration, differentiation and oxygen consumption rates (OCRs) with no change in extracellular acidification rates (ECAR) by Seahorse. FACs analysis confirmed reduction in SDHA component of mitochondrial complex II in Lgr5 +ISCs, demonstrating mechanistic cause for reduction in OXPHOS in ISCs. We next generated and utilized Lgr5 + ISC-specific SDHA KO mice as GVHD recipients and found that demonstrated significantly greater mortality when compared to the WT littermate recipients (P<0.01). Biochemical analyses demonstrated increased levels of succinate, a metabolic intermediary with known epigenetic and inflammatory functions, in ISCs harvested from GVHD animals. We therefore hypothesized that the reduction in ability to form functional organoids ex vivo, in the absence of ongoing inflammation, by the ISCs harvested from GVHD hosts is because of the inflammation epigenetic reprogramming induced by succinate mediated changes in DNA methylation (5-mC) of the ISCs in GVHD recipients. Consistent with the hypothesis greater DNA methylation, with alteration of epigenome by ATAC-seq was observed in ISCs sorted from GVHD recipients. Integrative analyses demonstrated correlation between epigenomic changes and transcriptomic changes. Finally, we analyzed whether the inflammation epigenomic induced changes in the GVHD ISCs with serial ex vivo organoid cultures and in vivo by transfer into secondary hosts. Both ex vivo and in vivo studies demonstrated poor regeneration from GVHD ISCs demonstrating retention of maladaptive memory in ISCs following their exposure to inflammation during GVHD. Conclusions: GI GVHD induced inflammation causes not only quantitative loss of ISCs but also induced qualitative changes in the surviving ISCs. Inflammation induced OXPHOS deficiency in Lgr5 + ISCs leads to accumulation of succinate that reprograms the epigenome and restrains their subsequent regeneration potential.

Real-Time Two-Photon Microscopy Reveals Spatially Heterogeneous T Lymphocyte Trafficking in the GI Microenvironment Influenced By GI Tissue Damage Level

Introduction: The trafficking of immune cells in the GI is crucial for tissue immunity and can be targeted for the treatment of immune-related GI damage. Flow cytometry, as the primary technique to identify immune cells in organs such as the GI, has made substantial progress, offering valuable insights into a variety of immune cell subtypes and their microenvironments. However, one major limitation is the destruction of tissue samples during processing, lacking spatial information on immune cells in their microenvironment. Furthermore, there is a lack of information about how stress-induced tissue damage affects T-cell trafficking. In particular, the pre-HCT conditioning regime is essential for identifying the extent of organ damage and donor immune cell trafficking to the GI microenvironment and the subsequent occurrence of Graft vs Host Disease (GVHD). To address this need, it is necessary to develop a real-time imaging method for characterizing immune cells in the GI in an allogeneic bone marrow transplant (BMT) system. Here, we report developing a temperature-controlled Two-photon microscopy (TPM) setup investigating the pattern of T cell trafficking in the GI in real time and how modulating radiation dose affects immune cell trafficking in the preclinical mouse GVHD model of allogeneic BMT. Method: BALB/c Host mice were treated with 8 Gy TBI in 2 fractions, 6 h apart. For the GI dose reduction study (GI-4 Gy), Total Marrow Irradiation (TMI 8:4; 8 Gy to Bone marrow, 4 Gy to rest of the body including GI) was used as described (Darren et al. 2021). Donor B6 T cell Depleted bone marrow cells along with 1 million enriched tdtomato+ T cells were transplanted, and 7 days later, live T cell trafficking in GI was monitored by TPM (Prairie Ultima microscope). Vessels were labeled with QTracker 655, and TPM parameters were set as described (J Brooks et al. 2021). For imaging, a temperature-controlled externalized intestine's intravital imaging (EIII) window was developed (Fig 1.A) and was first evaluated to visualize the three-dimensional basis of Jejunum. It allows continuous blood flow while effectively controlling peristalsis, cardiac and respiratory motion artifacts with minimal tissue damage, delay in tissue degradation. A section of the intestine (Jejunum) was externalized from anesthetized mice and fixed on the EIII window's surface using n-butyl cyanoacrylate veterinary adhesive. The luminal surface was exposed by making an incision along the intestine, carefully avoiding the vascular plexus. The spatial distribution of vessels and tdtomato+ T-cells (green) at different z-stacks was evaluated by imaging through both serosa and luminal sides. GI samples were fixed in 10% NBF, OCT embedded, cryosection (5-10 m), and Anti-MAdCAM1 immunofluorescence (IF) performed using a standard protocol. Results: EIII window usage significantly reduced peristaltic movement, enabling T cells imaging at different depths from serosa to villi crypt (Fig 1.A-B). T cells reside preferentially in the lower crypt region and are affected by the radiation dose given to GI (Fig 1.D-G). T-cell localization at the crypt base region (~ 100µ from serosa) was significantly higher in TBI (8 Gy GI dose) mice than in TMI (4 Gy GI dose). Fig. 1 (F-G) shows T cell distribution at the top, middle, and base of the villi, and in the crypt, during luminal side imaging. Further, microvascular structures were affected at higher radiation dose, as seen by reduced vessel density in 8 Gy over 4 Gy treatments or control (Fig 1.C). Thus, ~50% dose reduction improved vasculature and reduced T cell trafficking. Histological analysis of intestinal tissue with lysozyme and anti-MAdCAM1 staining for confocal imaging further shows reduced crypt damage and T cell trafficking in lower radiation (Fig 1.H). Summary: TPM enabled us to visualize T cells in real-time within the GVHD mouse intestine. Radiation-induced tissue damage-dependent T-cell trafficking was evident in the mouse GI with GVHD and validated through the target receptor of MAdCAM1 endothelial cell expression. The spatial heterogeneity of T cells emphasizes the preferential niche of immune trafficking and associated GI environment and thus, the need for cautious interpretation of GVHD biopsies and warrants further studies on their spatial localization in immune cell-mediated GI diseases.

Exopolysaccharide-Treated Dendritic Cells Effectively Ameliorate Acute Graft-versus-Host Disease

Graft-versus-host disease (GVHD) is a primary and often lethal complication of allogenic hematopoietic stem cell transplantation (HSCT). Prophylactic regimens for GVHD are given as standard pretransplantation therapy; however, up to 50% of these patients develop acute GVHD (aGVHD) and require additional immunosuppressive intervention. Using a mouse GVHD model, we previously showed that injecting mice with exopolysaccharide (EPS) from Bacillus subtilis prior to GVHD induction significantly increased 80-day survival after transplantation of complete allogeneic major histocompatibility complex-mismatched cells. To ask whether EPS might also inhibit GVHD in humans, we used humanized NSG-HLA-A2 mice and induced GVHD by i.v. injection of A2neg human peripheral blood mononuclear cells (PBMCs). Because we could not inject human donors with EPS, we transferred EPS-pretreated dendritic cells (DCs) to inhibit aGVHD. We derived these DCs from CD34+ human cord blood cells, treated them with EPS, and then injected them together with PBMCs into the NSG-HLA-A2 mice. We found that all mice that received untreated DCs were dead by day 35, whereas 25% of mice receiving EPS-treated DCs (EPS-DCs) survived. This DC cell therapy could be readily translatable to humans, because we can generate large numbers of human EPS-DCs and use them as an "off the shelf" treatment for patients undergoing HSCT.

Effects of Dietary Supplementation with a Ferulic Acid-Rich Bioactive Component of Wheat Bran in a Murine Model of Graft-Versus-Host Disease.

Graft-versus-host disease (GvHD) is a common and severe complication following allogeneic hematopoietic stem cell transplantation (HSCT). Its prevention and treatment is a major challenge. Ferulic acid (FA) has anti-inflammatory and antioxidant properties that could be attractive in this setting. Our aim was to evaluate a bioactive ingredient derived from wheat bran (WB), selected for its high concentration of FA, in a murine model of GvHD. The ingredient was obtained via a bioprocess involving hydrolysis and spray-drying. GvHD was induced via HSCT between MHC-mismatched mouse strains. FA treatment was administered orally. Survival and disease scores (weight loss, hunching, activity, fur texture, and skin integrity, each scored between 0 and 2 depending on disease severity) were recorded daily, histological evaluation was performed at the end of the experiment, and serum inflammatory cytokines were analyzed on days 9 and 28. Treatment with FA did not protect GvHD mice from death, nor did it diminish GvHD scores. However, histological analysis showed that ulcers with large areas of inflammatory cells, vessels, and keratin were less common in skin samples from FA-treated mice. Areas of intense inflammatory response were also seen in fewer small intestine samples from treated mice. In addition, a slight decrease in INF-γ and TNF-α expression was observed in the serum of treated mice on day 28. The results showed some local effect of the ingredient intervention, but that the dose used may not be sufficient to control or reduce the inflammatory response at the systemic level in mice with GvHD. Higher dosages of FA may have an impact when evaluating the immunomodulatory capabilities of the hydrolyzed WB ingredient. Thus, further experiments and the use of technological strategies that enrich the ingredients in soluble ferulic acid to improve its efficacy in this setting are warranted.

Assessing cell chimerism in an acute graft-versus-host disease model established in TLR4 knockout mice.

Graft-versus-host disease (GVHD) is a major complication after allogeneic hematopoietic stem cell transplantation. To elucidate the role of Toll-like receptor 4 (TLR4), the major receptor for bacterial lipopolysaccharide, in the development of GVHD, we constructed a GVHD model in TLR4 knockout (TLR4-/-) mice and monitored the cell chimerism. In this study, we used polymerase chain reaction to identify whether TLR4 knockout (TLR4-/-) mice were established. Before transplantation, we pretreated mice with irradiation so as to obtain an appropriate irradiation dose. Flow cytometry was applied to measure the chimerism status, the distributions of antigen-presenting cells (APCs), and T-cells in TLR4+/+ and TLR4-/- recipient mice. The general condition of TLR4-/- recipients was better than that of TLR4+/+ recipients, and the TLR4-/- recipient mice showed less severe GVHD manifestations than the TLR4+/+ recipient mice. Most of the APCs and T-cells in the host mouse spleen were derived from donor cells, and CD4+ T-cells, including memory T-cells, were in the majority in host mice. In general, our data show that TLR4 deletion attenuated GVHD development, which suggests that TLR4 could be used as a novel target and therapeutic paradigm in GVHD therapies.

Murine models of graft versus host disease (GVHD): Focus on ocular GVHD

Graft versus host disease (GVHD) remains a major and serious complication of allogeneic hematopoietic stem cell transplantation. Based on the time of onset, clinical phenotypes, progression kinetics, and pathophysiology, GVHD is stratified into acute, chronic, and overlapping types. The eyes are among the most commonly affected organs in GVHD. Mouse models have played an important role in understanding the several key elements of GVHD pathobiology. The current review discusses the immunology, pathology, and key phenotypic features of mouse models of systemic GVHD. Furthermore, a critical appraisal of mouse models of ocular GVHD (oGVHD) is provided. The disease mechanisms underlying the ocular surface, meibomian gland, and lacrimal gland injury in these models are reviewed, and the relevance of oGVHD murine models to clinical oGVHD is also included.

Defining a TCF1-expressing progenitor allogeneic CD8+ T cell subset in acute graft-versus-host disease

Graft-versus-host disease (GvHD) is a severe complication of hematopoietic stem cell transplantation driven by activated allogeneic T cells. Here, we identify a distinct subset of T cell factor-1 (TCF1)+ CD8+ T cells in mouse allogeneic and xenogeneic transplant models of acute GvHD. These TCF1+ cells exhibit distinct characteristics compared to TCF1- cells, including lower expression of inhibitory receptors and higher expression of costimulatory molecules. Notably, the TCF1+ subset displays exclusive proliferative potential and could differentiate into TCF1- effector cells upon antigenic stimulation. Pathway analyses support the role of TCF1+ and TCF1- subsets as resource cells and effector cells, respectively. Furthermore, the TCF1+ CD8+ T cell subset is primarily present in the spleen and exhibits a resident phenotype. These findings provide insight into the differentiation of allogeneic and xenogeneic CD8+ T cells and have implications for the development of immunotherapeutic strategies targeting acute GvHD.