Nuclear Matrix-associated Protein SMAR1 Attenuated Acute Graft-versus-host Disease by Targeting JAK-STAT Signaling in CD4 + T Cells

BACKGROUND

Acute graft-versus-host disease (aGVHD) mediated by alloreactive T cells remains a serious and life-threatening complication of allogeneic hematopoietic cell transplantation (allo-HCT). The contribution of the different CD4 + T helper cell subtypes to the pathogenesis and regulation of aGVHD is a central point in current research. The specialized effector subsets of T cells that differentiate from naive T cells into mature cells are closely related to scaffold/matrix-associated region-1-binding protein (SMAR1). However, the role of SMAR1 in aGVHD is unclear.

METHODS

Peripheral blood was collected from the patients with or without aGVHD after allo-HCT. The differences in CD4 + T cells transduced with the SMAR1 lentivirus vector and empty vector were analyzed. A humanized aGVHD mouse model was constructed to evaluate the function of SMAR1 in aGVHD.

RESULTS

The expression of SMAR1 was significantly reduced in the CD4 + T cells from aGVHD patients and related to the occurrence of aGVHD. SMAR1 overexpression in human CD4 + T cells regulated CD4 + T-cell subsets differentiation and inflammatory cytokines secretion and inhibited the Janus kinase/signal transducer and activator of transcription pathway. Moreover, SMAR1 changed chromatin accessibility landscapes and affected the binding motifs of key transcription factors regulating T cells. Additionally, upregulation of SMAR1 expression in CD4 + T cells improved the survival and pathology in a humanized aGVHD mouse model.

CONCLUSIONS

Our results showed that upregulation of SMAR1 regulated the CD4 + T-cell subpopulation and cytokines secretion and improved survival in a humanized aGVHD mouse model by alleviating inflammation. This study provides a promising therapeutic target for aGVHD.

Corticosteroids impair epithelial regeneration in immune-mediated intestinal damage

Corticosteroid treatment (CST) failure is associated with poor outcomes for patients with gastrointestinal (GI) graft-versus-host disease (GVHD). CST is intended to target the immune system, but the glucocorticoid receptor (GR) is widely expressed, including within the intestines, where its effects are poorly understood. Here, we report that corticosteroids (CS) directly targeted intestinal epithelium, potentially worsening immune-mediated GI damage. CS administered to mice in vivo and intestinal organoid cultures ex vivo reduced epithelial proliferation. Following irradiation, immediate CST mitigated GI damage but delayed treatment attenuated regeneration and exacerbated damage. In a murine steroid-refractory (SR) GVHD model, CST impaired epithelial regeneration, worsened crypt loss, and reduced intestinal stem cell (ISC) frequencies. CST also exacerbated immune-mediated damage in organoid cultures with SR, GR-deficient T cells or IFN-γ. These findings correlated with CS-dependent changes in apoptosis-related gene expression and STAT3-related epithelial proliferation. Conversely, IL-22 administration enhanced STAT3 activity and overcame CS-mediated attenuation of regeneration, reducing crypt loss and promoting ISC expansion in steroid-treated mice with GVHD. Therefore, CST has the potential to exacerbate GI damage if it fails to control the damage-inducing immune response, but this risk may be countered by strategies augmenting epithelial regeneration, thus providing a rationale for clinical approaches combining such tissue-targeted therapies with immunosuppression.

Interferon regulatory factor 4 plays a pivotal role in the development of aGVHD-associated colitis

Interferon regulatory factor 4 (IRF4) is a master transcription factor that regulates T helper cell (Th) differentiation. It interacts with the Basic leucine zipper transcription factor, ATF-like (BATF), depletion of which in CD4+ T cells abrogates acute graft-versus-host disease (aGVHD)-induced colitis. Here, we investigated the immune-regulatory role of Irf4 in a mouse model of MHC-mismatched bone marrow transplantation. We found that recipients of allogenic Irf4-/- CD4+ T cells developed less GVHD-related symptoms. Transcriptome analysis of re-isolated donor Irf4-/- CD4+ T helper (Th) cells, revealed gene expression profiles consistent with loss of effector T helper cell signatures and enrichment of a regulatory T cell (Treg) gene expression signature. In line with these findings, we observed a high expression of the transcription factor BTB and CNC homolog 2; (BACH2) in Irf4-/- T cells, which is associated with the formation of Treg cells and suppression of Th subset differentiation. We also found an association between BACH2 expression and Treg differentiation in patients with intestinal GVHD. Finally, our results indicate that IRF4 and BACH2 act as counterparts in Th cell polarization and immune homeostasis during GVHD. In conclusion, targeting the BACH2/IRF4-axis could help to develop novel therapeutic approaches against GVHD.

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.

Notch signaling drives intestinal graft-versus-host disease in mice and nonhuman primates

Notch signaling promotes T cell pathogenicity and graft-versus-host disease (GVHD) after allogeneic hematopoietic cell transplantation (allo-HCT) in mice, with a dominant role for the Delta-like Notch ligand DLL4. To assess whether Notch's effects are evolutionarily conserved and to identify the mechanisms of Notch signaling inhibition, we studied antibody-mediated DLL4 blockade in a nonhuman primate (NHP) model similar to human allo-HCT. Short-term DLL4 blockade improved posttransplant survival with durable protection from gastrointestinal GVHD in particular. Unlike prior immunosuppressive strategies tested in the NHP GVHD model, anti-DLL4 interfered with a T cell transcriptional program associated with intestinal infiltration. In cross-species investigations, Notch inhibition decreased surface abundance of the gut-homing integrin α4β7 in conventional T cells while preserving α4β7 in regulatory T cells, with findings suggesting increased β1 competition for α4 binding in conventional T cells. Secondary lymphoid organ fibroblastic reticular cells emerged as the critical cellular source of Delta-like Notch ligands for Notch-mediated up-regulation of α4β7 integrin in T cells after allo-HCT. Together, DLL4-Notch blockade decreased effector T cell infiltration into the gut, with increased regulatory to conventional T cell ratios early after allo-HCT. Our results identify a conserved, biologically unique, and targetable role of DLL4-Notch signaling in intestinal GVHD.

Co-expression of Foxp3 and Helios facilitates the identification of human T regulatory cells in health and disease

Foxp3 is regarded as the major transcription factor for T regulatory (Treg) cells and expression of Foxp3 is used to identify and quantitate Treg cells in mouse models. However, several studies have demonstrated that human CD4+ T conventional (Tconv) cells activated in vitro by T cell receptor (TCR) stimulation can express Foxp3. This observation has raised doubt as to the suitability of Foxp3 as a Treg marker in man. Helios, a member of the Ikaros gene family, has been shown to be expressed by 80-90% of human Foxp3+ Treg cells and can potentially serve as a marker of human Treg. Here, we confirm that Foxp3 expression is readily upregulated by Tconv upon TCR stimulation in vitro, while Helios expression is not altered. More importantly, we show that Foxp3 expression is not elevated by stimulation of hTconv in a humanized mouse model of graft versus host disease (GVHD) and in patients with a wide variety of acute and chronic inflammatory diseases including sickle cell disease, acute and chronic GVHD, systemic lupus erythematosus, as well as critical COVID-19. In all patients studied, an excellent correlation was observed between the percentage of CD4+ T cells expressing Foxp3 and the percentage expressing Helios. Taken together, these studies demonstrate that Foxp3 is not induced upon Tconv cell activation in vivo and that Foxp3 expression alone can be used to quantitate Treg cells in humans. Nevertheless, the combined use of Foxp3 and Helios expression provides a more reliable approach for the characterization of Treg in humans.

Galectin-3 expression in donor T cells reduces GvHD severity and lethality after allogeneic hematopoietic cell transplantation

Abundant donor cytotoxic T cells that attack normal host organs remain a major problem for patients receiving allogeneic hematopoietic cell transplantation (allo-HCT). Despite an increase in our knowledge of the pathobiology of acute graft versus host disease (aGvHD), the mechanisms regulating the proliferation and function of donor T cells remain unclear. Here, we show that activated donor T cells express galectin-3 (Gal-3) after allo-HCT. In both major and minor histocompatibility-mismatched models of murine aGvHD, expression of Gal-3 is associated with decreased T cell activation and suppression of the secretion of effector cytokines, including IFN-γ and GM-CSF. Mechanistically, Gal-3 results in activation of NFAT signaling, which can induce T cell exhaustion. Gal-3 overexpression in human T cells prevents severe disease by suppressing cytotoxic T cells in xenogeneic aGvHD models. Together, these data identify the Gal-3-dependent regulatory pathway in donor T cells as a critical component of inflammation in aGvHD.

A novel RIPK1 inhibitor reduces GVHD in mice via a nonimmunosuppressive mechanism that restores intestinal homeostasis

Intestinal epithelial cells (IECs) are implicated in the propagation of T-cell-mediated inflammatory diseases, including graft-versus-host disease (GVHD), but the underlying mechanism remains poorly defined. Here, we report that IECs require receptor-interacting protein kinase-3 (RIPK3) to drive both gastrointestinal (GI) tract and systemic GVHD after allogeneic hematopoietic stem cell transplantation. Selectively inhibiting RIPK3 in IECs markedly reduces GVHD in murine intestine and liver. IEC RIPK3 cooperates with RIPK1 to trigger mixed lineage kinase domain-like protein-independent production of T-cell-recruiting chemokines and major histocompatibility complex (MHC) class II molecules, which amplify and sustain alloreactive T-cell responses. Alloreactive T-cell-produced interferon gamma enhances this RIPK1/RIPK3 action in IECs through a JAK/STAT1-dependent mechanism, creating a feed-forward inflammatory cascade. RIPK1/RIPK3 forms a complex with JAK1 to promote STAT1 activation in IECs. The RIPK1/RIPK3-mediated inflammatory cascade of alloreactive T-cell responses results in intestinal tissue damage, converting the local inflammation into a systemic syndrome. Human patients with severe GVHD showed highly activated RIPK1 in the colon epithelium. Finally, we discover a selective and potent RIPK1 inhibitor (Zharp1-211) that significantly reduces JAK/STAT1-mediated expression of chemokines and MHC class II molecules in IECs, restores intestinal homeostasis, and arrests GVHD without compromising the graft-versus-leukemia (GVL) effect. Thus, targeting RIPK1/RIPK3 in IECs represents an effective nonimmunosuppressive strategy for GVHD treatment and potentially for other diseases involving GI tract inflammation.

Purinergic signalling in graft-versus-host disease

Allogeneic hematopoietic stem cell transplantation is used to treat blood cancers, but often results in lethal graft-versus-host disease (GVHD). GVHD is an inflammatory disorder mediated by donor leukocytes that damage host tissues. Purinergic signalling plays important roles in GVHD development in mice but studies of these pathways in human GVHD remain limited. P2X7 receptor activation by ATP on host antigen presenting cells contributes to the induction of GVHD, while activation of this receptor on regulatory T cells, myeloid-derived suppressor cells and possibly type 3 innate lymphoid cells results in their loss to promote GVHD progression. In contrast, A_2A receptor activation by adenosine on donor T cells serves to restrict GVHD development. These and other purinergic signalling molecules remain potential biomarkers and therapeutic targets in GVHD.

Tear Cytokines as Biomarkers for Acute Ocular Graft-Versus-Host Disease

PURPOSE

The purpose of this study was to analyze tear cytokine and complement levels in patients diagnosed with acute ocular graft-versus-host disease (oGVHD) and examine the consistency of these levels with the severity of clinical manifestations.

METHODS

Ten patients with acute oGVHD (20 eyes) were enrolled for the assessment of tear cytokine levels and ocular surface parameters, and 18 healthy people (36 eyes) were selected as the control group. The tear cytokine and complement levels were measured using microsphere-based immunoassay analysis.

RESULTS

The main clinical manifestations of acute oGVHD include eye redness, a large amount of purulent exudate, eye pain, and even false membranes. The levels of intercellular cell adhesion molecule-1, interleukin 6 (IL-6), interleukin 1 beta (IL-1β), interleukin 8, epidermal growth factor (EGF), interleukin 7 (IL-7), B-cell activating factor, granulocyte-macrophage colony-stimulating factor (GM-CSF), and complement in patients with acute oGVHD showed significant differences compared with those in normal people. Furthermore, the levels of IL-6, IL-1β, EGF, GM-CSF, IL-7, and C3a showed a stronger correlation with ocular surface parameters.

CONCLUSIONS

Our study was the first to enroll patients with acute oGVHD to assess tear cytokine levels as a method contributing to the diagnosis of acute oGVHD. In addition, it has been demonstrated that certain tear cytokines, including intercellular cell adhesion molecule-1, IL-6, IL-1β, interleukin 8, B-cell activating factor, GM-CSF, IL-7, EGF, and complement, may be new diagnostic biomarkers for acute oGVHD.

Therapeutic Potential of Mesenchymal Stem Cells in the Treatment of Ocular Graft-Versus-Host Disease

Ocular GVHD (oGVHD), manifested by severe injury of corneal epithelial cells, meibomian and lacrimal glands' dysfunction, is a serious complication of systemic GVHD which develops as a consequence of donor T and natural killer cell-driven inflammation in the eyes of patients who received allogeneic hematopoietic stem cell transplantation. Mesenchymal stem cells (MSC) are, due to their enormous differentiation potential and immunosuppressive characteristics, considered as a potentially new remedy in ophthalmology. MSC differentiate in corneal epithelial cells, suppress eye inflammation, and restore meibomian and lacrimal glands' function in oGVHD patients. MSC-sourced exosomes (MSC-Exos) are extracellular vesicles that contain MSC-derived growth factors and immunoregulatory proteins. Due to the lipid membrane and nano-sized dimension, MSC-Exos easily by-pass all biological barriers in the eyes and deliver their cargo directly in injured corneal epithelial cells and eye-infiltrated leukocytes, modulating their viability and function. As cell-free agents, MSC-Exos address all safety issues related to the transplantation of their parental cells, including the risk of unwanted differentiation and aggravation of intraocular inflammation. In this review article, we summarized current knowledge about molecular mechanisms which are responsible for beneficial effects of MSC and MSC-Exos in the therapy of inflammatory eye diseases, emphasizing their therapeutic potential in the treatment of oGVHD.

Phase 1 clinical trial of CRISPR-engineered CAR19 universal T cells for treatment of children with refractory B cell leukemia

Genome editing of allogeneic T cells can provide "off-the-shelf" alternatives to autologous chimeric antigen receptor (CAR) T cell therapies. Disruption of T cell receptor α chain (TRAC) to prevent graft-versus-host disease (GVHD) and removal of CD52 (cluster of differentiation 52) for a survival advantage in the presence of alemtuzumab have previously been investigated using transcription activator-like effector nuclease (TALEN)-mediated knockout. Here, we deployed next-generation CRISPR-Cas9 editing and linked CAR expression to multiplexed DNA editing of TRAC and CD52 through incorporation of self-duplicating CRISPR guide RNA expression cassettes within the 3' long terminal repeat of a CAR19 lentiviral vector. Three cell banks of TT52CAR19 T cells were generated and cryopreserved. A phase 1, open-label, non-randomized clinical trial was conducted and treated six children with relapsed/refractory CD19-positive B cell acute lymphoblastic leukemia (B-ALL) (NCT04557436). Lymphodepletion included fludarabine, cyclophosphamide, and alemtuzumab and was followed by a single infusion of 0.8 × 106 to 2.0 × 106 CAR19 T cells per kilogram with no immediate toxicities. Four of six patients infused with TT52CAR19 T cells exhibited cell expansion, achieved flow cytometric remission, and then proceeded to receive allogeneic stem cell transplantation. Two patients required biological intervention for grade II cytokine release syndrome, one patient developed transient grade IV neurotoxicity, and one patient developed skin GVHD, which resolved after transplant conditioning. Other complications were within expectations, and primary safety objectives were met. This study provides a demonstration of the feasibility, safety, and therapeutic potential of CRISPR-engineered immunotherapy.

Universal allogeneic CAR T cells engineered with Sleeping Beauty transposons and CRISPR-CAS9 for cancer immunotherapy

Allogeneic CD19-specific chimeric antigen receptor (CAR) T cells with inactivated donor T cell receptor (TCR) expression can be used as an "off-the-shelf" therapeutic modality for lymphoid malignancies, thus offering an attractive alternative to autologous, patient-derived T cells. Current approaches for T cell engineering mainly rely on the use of viral vectors. Here, we optimized and validated a non-viral genetic modification platform based on Sleeping Beauty (SB) transposons delivered with minicircles to express CD19-28z.CAR and CRISPR-Cas9 ribonucleoparticles to inactivate allogeneic TCRs. Efficient TCR gene disruption was achieved with minimal cytotoxicity and with attainment of robust and stable CD19-28z.CAR expression. The CAR T cells were responsive to CD19+ tumor cells with antitumor activities that induced complete tumor remission in NALM6 tumor-bearing mice while significantly reducing TCR alloreactivity and GvHD development. Single CAR signaling induced the similar T cell signaling signatures in TCR-disrupted CAR T cells and control CAR T cells. In contrast, TCR disruption inhibited T cell signaling/protein phosphorylation compared with the control CAR T cells during dual CAR/TCR signaling. This non-viral SB transposon-CRISPR-Cas9 combination strategy serves as an alternative for generating next-generation CD19-specific CAR T while reducing GvHD risk and easing potential manufacturing constraints intrinsic to viral vectors.

Structure-Activity relationship of 1-(Furan-2ylmethyl)Pyrrolidine-Based Stimulation-2 (ST2) inhibitors for treating graft versus host disease

An elevated plasma level of soluble ST2 (sST2) is a risk biomarker for graft-versus-host disease (GVHD) and death in patients receiving hematopoietic cell transplantation (HCT). sST2 functions as a trap for IL-33 and amplifies the pro-inflammatory type 1 and 17 response while suppressing the tolerogenic type 2 and regulatory T cells activation during GVHD development. We previously identified small-molecule ST2 inhibitors particularly iST2-1 that reduces plasma sST2 levels and improved survival in two animal models. Here, we reported the structure-activity relationship of the furanylmethylpyrrolidine-based ST2 inhibitors based on iST2-1. Based on the biochemical AlphaLISA assay, we improved the activity of iST2-1 by 6-fold (∼6 μM in IC50 values) in the inhibition of ST2/IL-33 and confirmed the activities of the compounds in a cellular reporter assay. To determine the inhibition of the alloreactivity in vitro, we used the mixed lymphocyte reaction assay to demonstrate that our ST2 inhibitors decreased CD4+ and CD8+ T cells proliferation and increased Treg population. The data presented in this work are critical to the development of ST2 inhibitors in future.

[Research Progress on Immunomodulatory Activity and Clinical Application of Mesenchymal Stem Cells-Derived Extracellular Vesicles--Review]

Mesenchymal stem cells (MSC) have been widely used in tissue regeneration and treatment graft versus host disease (GVHD) and immune diseases due to their self-renewal, multi-differentiation and immunoregulatory potential. However, more and more scholars begin to put weight on the MSC -derived extracellular vesicles (MSC-EV) for its regulation of inflammation and immunity. MSC-EV can activate the relevant signal pathways and regulate the function and biological behaviors of cells via acting on target cells and mediating communication between cells. MSC-EV has important potential clinical applications for its powerful immunomodulatory and hematopoietic regulatory functions. It is considered as a potential therapeutic tool to treat autoimmune diseases and GVHD. This paper reviewed the immunomodulatory activity of MSC-EV as well as the research progress of MSC-EV in hematopoietic stem cell transplantation, and discussed its potential clinical applications in the future.

Low Intestinal IL22 Associates With Increased Transplant-Related Mortality After Allogeneic Stem Cell Transplantation

The role of IL-22 in adult patients undergoing allogeneic stem cell transplantation (SCT) is of major interest since animal studies showed a protective and regenerative effect of IL-22 in graft versus host disease (GvHD). However, no clinical data exist on the tissue expression. Here we demonstrate that patients not suffering from transplant-related mortality (TRM) show significantly upregulated IL22 expression during histological and clinical GI-GvHD (p = 0.048 and p = 0.022, respectively). In contrast, in GvHD patients suffering from TRM, IL22 was significantly lower (p = 0.007). Accordingly, lower IL22 was associated with a higher probability of TRM in survival analysis (p = 0.005). In a multivariable competing risk Cox regression analysis, low IL22 was identified as an independent risk factor for TRM (p = 0.007, hazard ratio 2.72, 95% CI 1.32 to 5.61). The expression of IL22 seemed to be microbiota dependent as broad-spectrum antibiotics significantly diminished IL22 expression (p = 0.019). Furthermore, IL22 expression significantly correlated with G-protein coupled receptor (GPR)43 (r = 0.263, p = 0.015) and GPR41 expression (r = 0.284, p = 0.009). In conclusion, our findings reveal an essential role of IL-22 for the prognosis of patients undergoing allogeneic SCT.

The Interaction of HLA-C1/KIR2DL2/L3 Promoted KIR2DL2/L3 Single-Positive/NKG2C-Positive Natural Killer Cell Reconstitution, Raising the Incidence of aGVHD after Hematopoietic Stem Cell Transplantation

NKG2C+ natural killer (NK) cell plays a vital role in CMV infection control after hematopoietic stem cell transplantation (HSCT). However, the modulation on NKG2C+ NK cell reconstitution is still unclear. NK cell education is affected by the interactions of HLA-I/killer immunoglobulin receptor (KIR). Our aim is to figure out which HLA-I/KIR interaction plays a dominant role in NKG2C+ NK education. Based on allogeneic haploidentical HSCT, we investigated the expansion and function of single KIR positive NKG2C+ NK cells via the interaction of KIR with both donor HLA and recipient HLA at days 30, 90, and 180 after HSCT. KIR2DL2/L3 single-positive/NKG2C⁺ cells were significantly expanded compared with KIR2DL1 or KIR3DL1 single-positive/NKG2C⁺ cells when donors and recipients were both HLA-C1/C1 or HLA-C1C1BW4 (p < 0.05), with higher NKp30 expression (p < 0.05). Moreover, the proportion of single KIR positive NK cells increased in both NKG2C⁺/NKG2A^- NK cells and conventional NKG2C^-/NKG2A^- NK cells over time. We also observed that increased proportion of KIR2DL2/L3 single-positive/NKG2C⁺ NK cells correlated with higher incidence of acute graft-versus-host disease (aGVHD). Our study allows a better understanding of HLA-I/KIR interaction in the NKG2C+ NK cell education after HSCT.

The Role of Metabolic Dysfunction in T-Cell Exhaustion During Chronic Viral Infection

T cells are important components of adaptive immunity that protect the host against invading pathogens during infection. Upon recognizing the activation signals, naïve and/or memory T cells will initiate clonal expansion, trigger differentiation into effector populations and traffic to the inflamed sites to eliminate pathogens. However, in chronic viral infections, such as those caused by human immunodeficiency virus (HIV), hepatitis B and C (HBV and HCV), T cells exhibit impaired function and become difficult to clear pathogens in a state known as T-cell exhaustion. The activation and function persistence of T cells demand for dynamic changes in cellular metabolism to meet their bioenergetic and biosynthetic demands, especially the augmentation of aerobic glycolysis, which not only provide efficient energy generation, but also fuel multiple biochemical intermediates that are essential for nucleotide, amino acid, fatty acid synthesis and mitochondria function. Changes in cellular metabolism also affect the function of effectors T cells through modifying epigenetic signatures. It is widely accepted that the dysfunction of T cell metabolism contributes greatly to T-cell exhaustion. Here, we reviewed recent findings on T cells metabolism under chronic viral infection, seeking to reveal the role of metabolic dysfunction played in T-cell exhaustion.

Extracellular Vesicles as Biomarkers of Acute Graft-vs.-Host Disease After Haploidentical Stem Cell Transplantation and Post-Transplant Cyclophosphamide

Even with high-dose post-transplant cyclophosphamide (PT-Cy) which was initially introduced for graft-versus-host disease (GvHD) prevention in the setting of HLA-haploidentical transplantation, both acute and chronic GvHDs remain a major clinical challenge. Despite improvements in the understanding of the pathogenesis of both acute and chronic GvHDs, reliable biomarkers that predict their onset have yet to be identified. We recently studied the potential correlation between extracellular vesicles (EVs) and the onset of acute (a)GvHD in transplant recipients from related and unrelated donors. In the present study, we further investigated the role of the expression profile of membrane proteins and their microRNA (miRNA) cargo (miRNA100, miRNA155, and miRNA194) in predicting the onset of aGvHD in haploidentical transplant recipients with PT-Cy. Thirty-two consecutive patients were included. We evaluated the expression profile of EVs, by flow cytometry, and their miRNA cargo, by real-time PCR, at baseline, prior, and at different time points following transplant. Using logistic regression and Cox proportional hazard models, a significant association between expression profiles of antigens such as CD146, CD31, CD140a, CD120a, CD26, CD144, and CD30 on EVs, and their miRNA cargo with the onset of aGvHD was observed. Moreover, we also investigated a potential correlation between EV expression profile and cargo with plasma biomarkers (e.g., ST2, sTNFR1, and REG3a) that had been associated with aGVHD previously. This analysis showed that the combination of CD146, sTNFR1, and miR100 or miR194 strongly correlated with the onset of aGvHD (AUROC >0.975). A large prospective multicenter study is currently in progress to validate our findings.

Transcriptional and Epigenetic Regulation of Monocyte and Macrophage Dysfunction by Chronic Alcohol Consumption

Drinking alcohol, even in moderation, can affect the immune system. Studies have shown disproportionate effects of alcohol on circulating and tissue-resident myeloid cells (granulocytes, monocytes, macrophages, dendritic cells). These cells orchestrate the body's first line of defense against microbial challenges as well as maintain tissue homeostasis and repair. Alcohol's effects on these cells are dependent on exposure pattern, with acute drinking dampening but chronic drinking enhancing production of inflammatory mediators. Although chronic drinking is associated with heightened systemic inflammation, studies on tissue resident macrophage populations in several organs including the spleen, liver, brain, and lung have also shown compromised functional and metabolic capacities of these cells. Many of these effects are thought to be mediated by oxidative stress caused by alcohol and its metabolites which can directly impact the cellular epigenetic landscapes. In addition, since myeloid cells are relatively short-lived in circulation and are under constant repopulation from the bone marrow compartment, alcohol's effects on bone marrow progenitors and hematopoiesis are important for understanding the impact of alcohol systemically on these myeloid populations. Alcohol-induced disruption of progenitor, circulating, and tissue resident myeloid populations contribute to the increased susceptibility of patients with alcohol use disorders to viral and bacterial infections. In this review, we provide an overview of the impact of chronic alcohol consumption on the function of monocytes and macrophages in host defense, tissue repair and inflammation. We then summarize our current understanding of the mechanisms underlying alcohol-induced disruption and examine changes in transcriptome and epigenome of monocytes and mcrophages. Overall, chronic alcohol consumption leads to hyper-inflammation concomitant with decreased microbial and wound healing responses by monocytes/macrophages due to a rewiring of the epigentic and transcriptional landscape. However, in advanced alcoholic liver disease, myeloid cells become immunosuppressed as a response to the surrounding hyper-inflammatory milieu. Therefore, the effect of chronic alcohol on the inflammatory response depends on disease state and the immune cell population.

Donor T-Cell Repertoire Profiling in Recipient Lymphoid and Parenchyma Organs Reveals GVHD Pathogenesis at Clonal Levels After Bone Marrow Transplantation in Mice

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 be implicated in T-cell responses in autoimmunity, cancer, and organ transplantation. The correlation of T-cell repertoire with the pathogenesis of graft-versus-host disease (GVHD) after allogeneic hematopoietic cell transplantation remains largely undefined. Here, by utilizing high-throughput sequencing of the genes encoding TCRβ-chain, we comprehensively analyzed the profile of T-cell repertoire in recipient lymphoid and GVHD target organs after bone marrow transplantation (BMT) in mice. In lymphoid organs, TCR diversity was narrowed, accompanied with reduced numbers of unique clones while increased accumulation of dominant clones in allogeneic T cells compared to syngeneic T cells. In an individual allogeneic recipient, donor-derived TCR clones were highly overlapped among tissue sites, and the degree of overlapping was increasing from day 7 to 14 after allogeneic BMT. The top clones in peripheral blood, gut, liver, and lungs were highly mutually shared in an allogenic recipient, indicating that blood has the potential to predict dominant clones in these GVHD target organs. T cells in GVHD target organs from allogeneic recipients had fewer overlapped clones with pre-transplant donor T cells compared to those from syngeneic recipients. Importantly, the top 10 clones in allogeneic recipients were not detectable in pre-transplant donor T cells, indicating clonal expansion of rare rearrangements. Interestingly, even starting from the same pool of donor repertoires, T cells had very few overlapped clones between each allogeneic recipient who developed completely different dominant clones. We were only able to trace a single clone shared by three replicate allogeneic recipients within the top 500 clones. Although dominant clones were different among allogeneic recipients, V26 genes were consistently used more frequently by TCR clones in allogeneic than syngeneic recipients. This is the first study to extensively examine the feature of T-cell repertoire in multiple lymphoid and parenchyma organs, which establishes the association between T-cell activation and GVHD pathogenesis at the level of TCR clones. Immune repertoire sequencing-based methods may represent a novel personalized strategy to guide diagnosis and therapy in GVHD.

Mesenchymal stem cells (MSC) delays the occurrence of graft-versus-host disease(GVHD) in the inhibition of hematopoietic stem cells in major histocompatibility complex semi-consistent mice by regulating the expression of IFN-γ/IL-6

In recent years, because of its low immunogenicity and immunosuppression, mesenchymal stem cells (MSCs) have become a potential cell therapy for Graft-versus-host disease (GVHD). However, many experiments now focus on the interference of MSCs on T-cell proliferation in vitro and the prevention of GVHD in vivo. However, whether MSCs can effectively treat GVHD, the timing and conditions of treatment are not systematically studied. In order to clarify the therapeutic effect of MSC on GVHD, In this paper, mice were selected to build a model for study, and group control method was used. Experimental research proved that four mice died after transplantation with allogeneic hematopoietic stem cells treated by IFN- γ, and their white blood cell number remained basically unchanged, and their weight changed slightly. In addition, three groups of mice after allogeneic hematopoietic stem cell transplantation were used the incidence of GVHD was X2 = 20.6, indicating that the incidence of GVHD was significantly reduced and the survival rate of mice was significantly increased.

T-Cell Metabolism in Graft Versus Host Disease

Allogeneic-hematopoietic stem cell transplantation (allo-HSCT) represents the only curative treatment option for numerous hematological malignancies. Elimination of malignant cells depends on the T-cells' Graft-versus-Tumor (GvT) effect. However, Graft-versus-Host-Disease (GvHD), often co-occurring with GvT, remains an obstacle for therapeutic efficacy. Hence, approaches, which selectively alleviate GvHD without compromising GvT activity, are needed. As already explored for autoimmune and inflammatory disorders, immuno-metabolic interventions pose a promising option to address this unmet challenge. Being embedded in a complex regulatory framework, immunological and metabolic pathways are closely intertwined, which is demonstrated by metabolic reprograming of T-cells upon activation or differentiation. In this review, current knowledge on the immuno-metabolic signature of GvHD-driving T-cells is summarized and approaches to metabolically interfere are outlined. Furthermore, we address the metabolic impact of standard medications for GvHD treatment and prophylaxis, which, in conjunction with the immuno-metabolic profile of alloreactive T-cells, could allow more targeted interventions in the future.

Recent Metabolic Advances for Preventing and Treating Acute and Chronic Graft Versus Host Disease

The therapeutic efficacy of allogeneic hematopoietic stem cell transplantation (allo-HSCT) is limited by the development of graft-versus-host disease (GVHD). In GVHD, rigorous pre-conditioning regimen resets the immune landscape and inflammatory milieu causing immune dysregulation, characterized by an expansion of alloreactive cells and a reduction in immune regulatory cells. In acute GVHD (aGVHD), the release of damage- and pathogen- associated molecular patterns from damaged tissue caused by the conditioning regimen sets the stage for T cell priming, activation and expansion further exacerbating tissue injury and organ damage, particularly in the gastrointestinal tract. Studies have shown that donor T cells utilize multiple energetic and biosynthetic pathways to mediate GVHD that can be distinct from the pathways used by regulatory T cells for their suppressive function. In chronic GVHD (cGVHD), donor T cells may differentiate into IL-21 producing T follicular helper cells or tissue resident T helper cells that cooperate with germinal center B cells or memory B cells, respectively, to produce allo- and auto-reactive antibodies with subsequent tissue fibrosis. Alternatively, donor T cells can become IFN- γ/IL-17 cytokine expressing T cells that mediate sclerodermatous skin injury. Patients refractory to the first line standard regimens for GVHD treatment have a poor prognosis indicating an urgent need for new therapies to restore the balance between effector and regulatory immune cells while preserving the beneficial graft-versus-tumor effect. Emerging data points toward a role for metabolism in regulating these allo- and auto-immune responses. Here, we will discuss the preclinical and clinical data available on the distinct metabolic demands of acute and chronic GVHD and recent efforts in identifying therapeutic targets using metabolomics. Another dimension of this review will examine the changing microbiome after allo-HSCT and the role of microbial metabolites such as short chain fatty acids and long chain fatty acids on regulating immune responses. Lastly, we will examine the metabolic implications of coinhibitory pathway blockade and cellular therapies in allo-HSCT. In conclusion, greater understanding of metabolic pathways involved in immune cell dysregulation during allo-HSCT may pave the way to provide novel therapies to prevent and treat GVHD.

Purinergic Signalling in Allogeneic Haematopoietic Stem Cell Transplantation and Graft-versus-Host Disease

Allogeneic haematopoietic stem cell transplantation (allo-HSCT) is a curative therapy for blood cancers and other haematological disorders. However, allo-HSCT leads to graft-versus-host disease (GVHD), a severe and often lethal immunological response, in the majority of transplant recipients. Current therapies for GVHD are limited and often reduce the effectiveness of allo-HSCT. Therefore, pro- and anti-inflammatory factors contributing to disease need to be explored in order to identify new treatment targets. Purinergic signalling plays important roles in haematopoiesis, inflammation and immunity, and recent evidence suggests that it can also affect haematopoietic stem cell transplantation and GVHD development. This review provides a detailed assessment of the emerging roles of purinergic receptors, most notably P2X7, P2Y2 and A2A receptors, and ectoenzymes, CD39 and CD73, in GVHD.

Mesenteric Lymph Node Transplantation in Mice to Study Immune Responses of the Gastrointestinal Tract

Mesenteric lymph nodes (mLNs) are sentinel sites of enteral immunosurveillance and immune homeostasis. Immune cells from the gastrointestinal tract (GIT) are constantly recruited to the mLNs in steady-state and under inflammatory conditions resulting in the induction of tolerance and immune cells activation, respectively. Surgical dissection and transplantation of lymph nodes (LN) is a technique that has supported seminal work to study LN function and is useful to investigate resident stromal and endothelial cell biology and their cellular interactions in experimental disease models. Here, we provide a detailed protocol of syngeneic mLN transplantation and report assays to analyze effective mLN engraftment in congenic recipients. Transplanted mLNs allow to study T cell activation and proliferation in preclinical mouse models. Donor mLNs proved viable and functional after surgical transplantation and regenerated blood and lymphatic vessels. Immune cells from the host completely colonized the transplanted mLNs within 7-8 weeks after the surgical intervention. After allogeneic hematopoietic cell transplantation (allo-HCT), adoptively transferred allogeneic CD4+ T cells from FVB/N (H-2q) mice homed to the transplanted mLNs in C57BL/6 (H-2b) recipients during the initiation phase of acute graft-versus-host disease (aGvHD). These CD4+ T cells retained full proliferative capacity and upregulated effector and gut homing molecules comparable to those in mLNs from unmanipulated wild-type recipients. Wild type mLNs transplanted into MHCII deficient syngeneic hosts sufficed to activate alloreactive T cells upon allogeneic hematopoietic cell transplantation, even in the absence of MHCII+ CD11c+ myeloid cells. These data support that orthotopically transplanted mLNs maintain physiological functions after transplantation. The technique of LN transplantation can be applied to study migratory and resident cell compartment interactions in mLNs as well as immune reactions from and to the gut under inflammatory and non-inflammatory conditions.

γδ T Cells May Aggravate Acute Graft-Versus-Host Disease Through CXCR4 Signaling After Allogeneic Hematopoietic Transplantation

Graft-versus-host disease (GVHD) is a pathology in which chemokines and their receptors play essential roles in directing the migration of alloreactive donor T cells into GVHD organs, thereby leading to further target tissue damage. Currently, acute GVHD (aGVHD) remains a major cause of high morbidity and mortality in patients who underwent allogeneic hematopoietic cell transplantation (alloHCT). The identification of immune cells that correlate with aGVHD is important and intriguing. To date, the involvement of innate-like γδ T cells in the pathogenesis of aGVHD is unclear. Herein, we found that primary human γδ T cells did not directly trigger allogeneic reactions. Instead, we revealed that γδ T cells facilitated the migration of CD4 T cells via the SDF-1-CXCR4 axis. These results indicate indirect regulation of γδ T cells in the development of aGVHD rather than a direct mechanism. Furthermore, we showed that the expression of CXCR4 was significantly elevated in γδ T cells and CD4 and CD8 T cells in recipients who experienced grades II-IV aGVHD after alloHCT. Consistently, CXCR4-expressing γδ T cells and CD4 T cells were induced in the target organs of mice suffering aGVHD. The depletion of γδ T cells in transplant grafts and treatment with AMD3100, an inhibitor of CXCR4 signaling, delayed the onset of aGVHD and prolonged survival in mice. Taken together, these findings suggest a role for γδ T cells in recruiting alloreactive CD4 T cells to target tissues through the expression of CXCR4. Our findings may help in understanding the mechanism of aGVHD and provide novel therapeutic targets.

Compound A Increases Cell Infiltration in Target Organs of Acute Graft-versus-Host Disease (aGVHD) in a Mouse Model

Systemic steroids are used to treat acute graft-versus-host disease (aGVHD) caused by allogenic bone marrow transplantation (allo-BMT); however, their prolonged use results in complications. Hence, new agents for treating aGVHD are required. Recently, a new compound A (CpdA), with anti-inflammatory activity and reduced side effects compared to steroids, has been identified. Here, we aimed to determine whether CpdA can improve the outcome of aGVHD when administered after transplantation in a mouse model (C57BL/6 in B6D2F1). After conditioning with 9Gy total body irradiation, mice were infused with bone marrow (BM) cells and splenocytes from either syngeneic (B6D2F1) or allogeneic (C57BL/6) donors. The animals were subsequently treated (3 days/week) with 7.5 mg/kg CpdA from day +15 to day +28; the controls received 0.9% NaCl. Thereafter, the incidence and severity of aGVHD in aGVHD target organs were analyzed. Survival and clinical scores did not differ significantly; however, CpdA-treated animals showed high cell infiltration in the target organs. In bulk mixed lymphocyte reactions, CpdA treatment reduced the cell proliferation and expression of inflammatory cytokines and chemokines compared to controls, whereas levels of TNF, IL-23, chemokines, and chemokine receptors increased. CpdA significantly reduced proliferation in vitro but increased T cell infiltration in target organs.

Survival and Functional Immune Reconstitution After Haploidentical Stem Cell Transplantation in Atm-Deficient Mice

Hematopoietic stem cell transplantation (HSCT) has been proposed as a promising therapeutic opportunity to improve immunity and prevent hematologic malignancies in Ataxia-telangiectasia (A-T). However, experience in the transplantation strategy for A-T patients is still scarce. The aim of this study was to investigate whether different approaches of HSCT are feasible in regard to graft versus host response and sufficient concerning functional immune reconstitution. Atm-deficient mice were treated with a clinically relevant non-myeloablative host-conditioning regimen and transplanted with CD90.2-depleted, green fluorescent protein (GFP)-expressing, and ataxia telangiectasia mutated (ATM)-competent bone marrow donor cells in a syngeneic, haploidentical or allogeneic setting. Like syngeneic HSCT, haploidentical HSCT, but not allogeneic HSCT extended the lifespan of Atm-deficient mice through the reduction of thymic tumors and normalized T-cell numbers. Donor-derived splenocytes isolated from transplanted Atm-deficient mice filled the gap of cell loss in the naïve T-cell population and raised CD4 cell functionality up to wild-type level. Interestingly, HSCT using heterozygous donor cells let to a significantly improved survival of Atm-deficient mice and increased CD4 cell numbers as well as CD4 cell functionality equivalent to HSCT using with wild-type donor cells. Our data provided evidence that haploidentical HSCT could be a feasible strategy for A-T, possibly even if the donor is heterozygous for ATM. However, this basic research cannot substitute any research in humans.

Single-cell transcriptomic analysis reveals disparate effector differentiation pathways in human Treg compartment

Human FOXP3+ regulatory T (Treg) cells are central to immune tolerance. However, their heterogeneity and differentiation remain incompletely understood. Here we use single-cell RNA and T cell receptor sequencing to resolve Treg cells from healthy individuals and patients with or without acute graft-versus-host disease (aGVHD) who undergo stem cell transplantation. These analyses, combined with functional assays, separate Treg cells into naïve, activated, and effector stages, and resolve the HLA-DRhi, LIMS1hi, highly suppressive FOXP3hi, and highly proliferative MKI67hi effector subsets. Trajectory analysis assembles Treg subsets into two differentiation paths (I/II) with distinctive phenotypic and functional programs, ending with the FOXP3hi and MKI67hi subsets, respectively. Transcription factors FOXP3 and SUB1 contribute to some Path I and Path II phenotypes, respectively. These FOXP3hi and MKI67hi subsets and two differentiation pathways are conserved in transplanted patients, despite having functional and migratory impairments under aGVHD. These findings expand the understanding of Treg cell heterogeneity and differentiation and provide a single-cell atlas for the dissection of Treg complexity in health and disease.

Posttransplant cyclophosphamide is associated with increased cytomegalovirus infection: a CIBMTR analysis

Prior studies suggest increased cytomegalovirus (CMV) infection after haploidentical donor transplantation with posttransplant cyclophosphamide (HaploCy). The role of allograft source and posttransplant cyclophosphamide (PTCy) in CMV infection is unclear. We analyzed the effect of graft source and PTCy on incidence of CMV infection, and effects of serostatus and CMV infection on transplant outcomes. We examined patients reported to the Center for International Blood and Marrow Transplantation Research between 2012 and 2017 who had received HaploCy (n = 757), matched related (Sib) with PTCy (SibCy, n = 403), or Sib with calcineurin inhibitor-based prophylaxis (SibCNI, n = 1605). Cumulative incidences of CMV infection by day 180 were 42%, 37%, and 23%, respectively (P < .001). CMV disease was statistically comparable. CMV infection risk was highest for CMV-seropositive recipients (R+), but significantly higher in PTCy recipients regardless of donor (HaploCy [n = 545]: hazard ratio [HR], 50.3; SibCy [n = 279]: HR, 47.7; SibCNI [n = 1065]: HR, 24.4; P < .001). D+/R- patients also had increased risk for CMV infection. Among R+ or those developing CMV infection, HaploCy had worse overall survival and nonrelapse mortality. Relapse was unaffected by CMV infection or serostatus. PTCy was associated with lower chronic graft-versus-host disease (GVHD) overall, but CMV infection in PTCy recipients was associated with higher chronic GVHD (P = .006). PTCy, regardless of donor, is associated with higher incidence of CMV infection, augmenting the risk of seropositivity. Additionally, CMV infection may negate the chronic GVHD protection of PTCy. This study supports aggressive prevention strategies in all receiving PTCy.

Nanoparticles Engineered as Artificial Antigen-Presenting Cells Induce Human CD4+ and CD8+ Tregs That Are Functional in Humanized Mice

Artificial antigen-presenting cells (aAPCs) are synthetic versions of naturally occurring antigen-presenting cells (APCs) that, similar to natural APCs, promote efficient T effector cell responses in vitro. This report describes a method to produce acellular tolerogenic aAPCs made of biodegradable poly lactic-co-glycolic acid (PLGA) nanoparticles (NPs) and encapsulating IL-2 and TGF-β for a paracrine release to T cells. We document that these aAPCs can induce both human CD4+ and CD8+ T cells to become FoxP3+ T regulatory cells (Tregs). The aAPC NP-expanded human Tregs are functional in vitro and can modulate systemic autoimmunity in vivo in humanized NSG mice. These findings establish a proof-of-concept to use PLGA NPs as aAPCs for the induction of human Tregs in vitro and in vivo, highlighting the immunotherapeutic potential of this targeted approach to repair IL-2 and/or TGF-β defects documented in certain autoimmune diseases such as systemic lupus erythematosus.

Anti-ICOS mAb Targets Pathogenic IL-17A-expressing Cells in Canine Model of Chronic GVHD

BACKGROUND

Chronic graft-versus-host disease (GVHD) is a significant cause of morbidity and mortality in transplant patients. We have previously shown that 3 doses of an anti-inducible costimulator (ICOS) mAb transiently ameliorated symptoms and extended survival of dogs affected by chronic GVHD over that of control dogs. The purpose of this study was to specifically correlate changes in T-cell populations in the peripheral blood with anti-ICOS treatment and chronic GVHD progression and regression to reach a better understanding of the mechanism of the disease and prioritize future studies.

METHODS

Peripheral blood cells from canines transplanted with DLA-mismatched bone marrow and peripheral blood mononuclear cells to generate chronic GVHD were analyzed by flow cytometry using a panel of antibodies specific to helper and cytolytic T cells.

RESULTS

Chronic GVHD was specifically associated with an increase in CD4+ICOS+ cells, ICOS+ cells expressing IL-17A, and CD8+ cells generating granzyme B. Treatment with anti-ICOS mAb at onset of chronic GVHD symptoms specifically targeted IL-17A+-expressing cells, transiently relieved symptoms, and lengthened survival but was unable to reduce the percentage of CD8+ T-cells expressing granzyme B.

CONCLUSIONS

These studies suggested a role for both CD4+ and CD8+ T cells in pathogenesis of chronic GVHD in the canine model. We propose that future studies should focus on further extending survival by developing a treatment that would control both CD4+ and CD8+ T cells.

Indole derivatives, microbiome and graft versus host disease

Graft versus host disease is a life-threatening complication following allogeneic hematopoietic stem cell transplantation driven by donor T cells reacting against disparate host antigens. Immune homeostasis within the gut plays a major role in the graft versus host response. Gut microbiota and its metabolites impact gut integrity, inflammation and immune activation within the gut. This review will focus on the role of indoles, a product of microbiota metabolism, on gut homeostasis and our current understanding on how that modulates graft versus host disease.

Mobilized Multipotent Hematopoietic Progenitors Promote Expansion and Survival of Allogeneic Tregs and Protect Against Graft Versus Host Disease

Allogeneic Hematopoietic Stem Cell Transplantation (Allo-HSCT) is routinely performed with peripheral blood stem cells (PBSCs) mobilized by injection of G-CSF, a growth factor which not only modulates normal hematopoiesis but also induces diverse immature regulatory cells. Based on our previous evidence that G-CSF-mobilized multipotent hematopoietic progenitors (MPP) can increase survival and proliferation of natural regulatory T cells (Tregs) in autoimmune disorders, we addressed the question how these cells come into play in mice and humans in an alloimmune setting. Using a C57BL/6 mouse model, we demonstrate that mobilized MPP enhance the immunosuppressant effect exerted by Tregs, against alloreactive T lymphocytes, both in vitro and in vivo. They do so by migrating to sites of allopriming, interacting with donor Tregs and increasing their numbers, thus reducing the lethality of graft-versus-host disease (GVHD). Protection correlates likewise with increased allospecific Treg counts. Furthermore, we provide evidence for a phenotypically similar MPP population in humans, where it shares the capacity to promote selective Treg expansion in vitro. We postulate that G-CSF-mobilized MPPs might become a valuable cellular therapy to expand donor Tregs in vivo and prevent GVHD, thereby making allo-HSCT safer for the treatment of leukemia patients.

Glycolytic metabolism of pathogenic T cells enables early detection of GVHD by 13C-MRI

Graft-versus-host disease (GVHD) is a prominent barrier to allogeneic hematopoietic stem cell transplantation (AHSCT). Definitive diagnosis of GVHD is invasive, and biopsies of involved tissues pose a high risk of bleeding and infection. T cells are central to GVHD pathogenesis, and our previous studies in a chronic GVHD mouse model showed that alloreactive CD4+ T cells traffic to the target organs ahead of overt symptoms. Because increased glycolysis is an early feature of T-cell activation, we hypothesized that in vivo metabolic imaging of glycolysis would allow noninvasive detection of liver GVHD as activated CD4+ T cells traffic into the organ. Indeed, hyperpolarized 13C-pyruvate magnetic resonance imaging detected high rates of conversion of pyruvate to lactate in the liver ahead of animals becoming symptomatic, but not during subsequent overt chronic GVHD. Concomitantly, CD4+ T effector memory cells, the predominant pathogenic CD4+ T-cell subset, were confirmed to be highly glycolytic by transcriptomic, protein, metabolite, and ex vivo metabolic activity analyses. Preliminary data from single-cell sequencing of circulating T cells in patients undergoing AHSCT also suggested that increased glycolysis may be a feature of incipient acute GVHD. Metabolic imaging is being increasingly used in the clinic and may be useful in the post-AHSCT setting for noninvasive early detection of GVHD.

Potential Novel Biomarkers in Chronic Graft-Versus-Host Disease

Prognostic, diagnostic or predictive biomarkers are urgently needed for assessment of chronic graft-versus-host disease (cGvHD), a major risk for patients undergoing allogeneic hematopoietic stem cell transplantation. The main goal of this review generated within the COST Action EUROGRAFT "Integrated European Network on Chronic Graft Versus Host Disease" was to identify potential novel biomarkers for cGvHD besides the widely accepted molecular and cellular biomarkers. Thus, the focus was on cellular biomarkers, alloantibodies, glycomics, endothelial derived particles, extracellular vesicles, microbiome, epigenetic and neurologic changes in cGvHD patients. Both host-reactive antibodies in general, and particularly alloantibodies have been associated with cGvHD and require further consideration. Glycans attached to IgG modulate its activity and represent a promising predictive and/or stratification biomarker for cGVHD. Furthermore, epigenetic changes such as microRNAs and DNA methylation represent potential biomarkers for monitoring cGvHD patients and novel targets for developing new treatment approaches. Finally, the microbiome likely affects the pathophysiology of cGvHD; bacterial strains as well as microbial metabolites could display potential biomarkers for dysbiosis and risk for the development of cGvHD. In summary, although there are no validated biomarkers currently available for clinical use to better inform on the diagnosis, prognosis or prediction of outcome for cGvHD, many novel sources of potential markers have shown promise and warrant further investigation using well characterized, multi-center patient cohorts.

Tyrosine supplement ameliorates murine aGVHD by modulation of gut microbiome and metabolome

BACKGROUND

Microbial communities and their metabolic components in the gut are of vital importance for immune homeostasis and have an influence on the susceptibility of the host to a number of immune-mediated diseases like acute graft-versus-host disease (aGVHD) after allogeneic hematopoietic stem cell transplantation (allo-HSCT). However, little is known about the functional connections between microbiome and metabolome in aGVHD due to the complexity of the gastrointestinal environment.

METHOD

Initially, gut microbiota and fecal metabolic phenotype in aGVHD murine models were unleashed by performing 16S ribosomal DNA gene sequencing and ultra-high-performance liquid chromatography-mass spectrometry (UHPLC-MS)-based metabolomics.

FINDINGS

The group with aGVHD experienced a significant drop in Lachnospiraceae_unclassified but an increase in the relative abundance of Clostridium XI, Clostridium XIVa and Enterococcus. Meanwhile, a lower content of tyrosine was observed in the gut of aGVHD mice. The correlation analysis revealed that tyrosine-related metabolites were inversely correlated with Clostridium XIVa, besides, Blautia and Enterococcus also displayed the negative tendency in aGVHD condition. Apart from exploring the importance and function of tyrosine, different tyrosine diets were offered to mice during transplantation. Additional tyrosine supplements can improve overall survival, ameliorate symptoms at the early stage of aGVHD and change the structure and composition of gut microbiota and fecal metabolic phenotype. In addition, aGVHD mice deprived from tyrosine displayed worse manifestations than the vehicle diet group.

INTERPRETATION

The results demonstrated the roles and mechanisms of gut microbiota, indispensable metabolites and tyrosine in the progression of aGVHD, which can be an underlying biomarker for aGVHD diagnosis and treatment.

FUNDING

This research was funded by the International Cooperation and Exchange Program (81520108002), the National Key R&D Program of China, Stem Cell and Translation Research (2018YFA0109300), National Natural Science Foundation of China (81670169, 81670148, 81870080 and 91949115) and Natural Science Foundation of Zhejiang Province (LQ19H080006).

Aberrant HLA-DR expression in the conjunctival epithelium after autologous serum treatment in patients with graft-versus-host disease or Sjögren's syndrome

The aim of this study was to determine the effect of autologous serum (AS) eye drops on the density of human leucocyte antigen (HLA)-DR-positive epithelial cells and Langerhans cells on the ocular surface of patients with bilateral severe dry eye disease (DED) due to graft-versus-host disease (GvHD) or Sjögren’s syndrome (SS). The study was conducted on 24 patients (48 eyes). AS was applied 6–10 times daily for 3 months together with regular artificial tear therapy. HLA-DR-positive cells were detected by direct immunocytochemistry on upper bulbar conjunctiva imprints obtained before and after treatment. The application of AS drops led to a statistically significant increase in the mean density of aberrant HLA-DR-positive conjunctival epithelial cells (p < 0.05) and HLA-DR-positive Langerhans cells (p < 0.05) in the GvHD group. Aberrant HLA-DR-positive epithelial cells in the SS group were decreased non-significantly. All patients reported a significant decrease in the Ocular Surface Disease Index (p < 0.01), which indicates improvement of the patient’s subjective feelings after therapy. There was an expected but non-significant decrease of aberrant HLA-DR-positive conjunctival epithelial cells in the SS group only. However, the increased density of HLA-DR-positive cells, indicating slight subclinical inflammation, does not outweigh the positive effect of AS in patients with DED from GvHD.

The role of IL-22 in intestinal health and disease

The cytokine interleukin-22 (IL-22) is a critical regulator of epithelial homeostasis. It has been implicated in multiple aspects of epithelial barrier function, including regulation of epithelial cell growth and permeability, production of mucus and antimicrobial proteins (AMPs), and complement production. In this review, we focus specifically on the role of IL-22 in the intestinal epithelium. We summarize recent advances in our understanding of how IL-22 regulates homeostasis and host defense, and we discuss the IL-22 pathway as a therapeutic target in diseases of the intestine, including inflammatory bowel disease (IBD), graft-versus-host disease (GVHD), and cancer.

Vitamin C stabilizes CD8+ iTregs and enhances their therapeutic potential in controlling murine GVHD and leukemia relapse

Adoptive transfer of induced regulatory T cells (iTregs) can ameliorate graft-versus-host disease (GVHD) after allogeneic hematopoietic cell transplantation (allo-HCT). CD4+ iTregs can effectively prevent GVHD but impair the graft-versus-leukemia (GVL) effect, whereas CD8+ iTregs preserve the GVL effect but have limited efficacy in GVHD control because of their instability under inflammatory conditions. Thus, we aimed to stabilize CD8+ iTregs via treatment with vitamin C (Vit C) to improve their efficacy in controlling GVHD. We found that addition of Vit C significantly improved the stability of forkhead box P3 (Foxp3) expression in CD8+ iTregs. Moreover, Vit C-treated CD8+ iTregs exhibited high efficacy in attenuating acute and chronic GVHD. The mechanistic study revealed that addition of Vit C to CD8+ iTreg culture markedly increased DNA demethylation in the conserved noncoding sequence 2 region and, hence, maintained higher Foxp3 expression levels compared with untreated controls. In acute GVHD, Vit C-treated CD8+ iTregs were able to inhibit pathogenic T-cell expansion and differentiation while reducing thymus damage and B-cell activation in cGVHD. Importantly, in contrast to CD4+ iTregs, Vit C-treated CD8+ iTregs retained the ability to control tumor relapse. These results provide a strong rationale to use Vit C in the clinic to stabilize CD8+ iTregs for the control of GVHD and preservation of GVL after allo-HCT.

Joint model robustness compared with the time-varying covariate Cox model to evaluate the association between a longitudinal marker and a time-to-event endpoint

BACKGROUND

The recent progress in medical research generates an increasing interest in the use of longitudinal biomarkers for characterizing the occurrence of an outcome. The present work is motivated by a study, where the objective was to explore the potential of the long pentraxin 3 (PTX3) as a prognostic marker of Acute Graft-versus-Host Disease (GvHD) after haematopoietic stem cell transplantation. Time-varying covariate Cox model was commonly used, despite its limiting assumptions that marker values are constant in time and measured without error. A joint model has been developed as a viable alternative; however, the approach is computationally intensive and requires additional strong assumptions, in which the impacts of their misspecification were not sufficiently studied.

METHODS

We conduct an extensive simulation to clarify relevant assumptions for the understanding of joint models and assessment of its robustness under key model misspecifications. Further, we characterize the extent of bias introduced by the limiting assumptions of the time-varying covariate Cox model and compare its performance with a joint model in various contexts. We then present results of the two approaches to evaluate the potential of PTX3 as a prognostic marker of GvHD after haematopoietic stem cell transplantation.

RESULTS

Overall, we illustrate that a joint model provides an unbiased estimate of the association between a longitudinal marker and the hazard of an event in the presence of measurement error, showing improvement over the time-varying Cox model. However, a joint model is severely biased when the baseline hazard or the shape of the longitudinal trajectories are misspecified. Both the Cox model and the joint model correctly specified indicated PTX3 as a potential prognostic marker of GvHD, with the joint model providing a higher hazard ratio estimate.

CONCLUSIONS

Joint models are beneficial to investigate the capability of the longitudinal marker to characterize time-to-event endpoint. However, the benefits are strictly linked to the correct specification of the longitudinal marker trajectory and the baseline hazard function, indicating a careful consideration of assumptions to avoid biased estimates.

Role of interferon-γ in immune-mediated graft failure after allogeneic hematopoietic stem cell transplantation

Pathophysiology of graft failure (GF) occurring after allogeneic hematopoietic stem cell transplantation (HSCT) still remains elusive. We measured serum levels of several different cytokines/chemokines in 15 children experiencing GF, comparing their values with those of 15 controls who had sustained donor cell engraftment. Already at day +3 after transplantation, patients developing GF had serum levels of interferon (IFN)-γ and CXCL9 (a chemokine specifically induced by IFNγ) significantly higher than those of controls (8859±7502 vs. 0 pg/mL, P=0.03, and 1514.0±773 vs. 233.6±50.1 pg/mlL, P=0.0006, respectively). The role played by IFNγ in HSCT-related GF was further supported by the observation that a rat anti-mouse IFNγ-neutralizing monoclonal antibody promotes donor cell engraftment in Ifngr1-/-mice receiving an allograft. In comparison to controls, analysis of bone marrow-infiltrating T lymphocytes in patients experiencing GF documented a predominance of effector memory CD8+ cells, which showed markers of activation (overexpression of CD95 and downregulation of CD127) and exhaustion (CD57, CD279, CD223 and CD366). Finally, we obtained successful donor engraftment in 2 out of 3 children with primary hemophagocytic lymphohistiocytosis who, after experiencing GF, were re-transplanted from the same HLA-haploidentical donor under the compassionate use coverage of emapalumab, an anti-IFNγ monoclonal antibody recently approved by the US Food and Drug Administration for treatment of patients with primary hemophagocytic lymphohistiocytosis. Altogether, these results suggest that the IFNγ pathway plays a major role in GF occurring after HSCT. Increased serum levels of IFNγ and CXCL9 represent potential biomarkers useful for early diagnosis of GF and provide the rationale for exploring the therapeutic/preventive role of targeted neutralization of IFNγ.

TGFβ Programs Central Memory Differentiation in Ex Vivo-Stimulated Human T Cells

The adoptive transfer of ex vivo-expanded T cells is a promising approach to treat several malignancies. Several lines of evidence support that the infusion of T cells with early memory features, capable of expanding and persisting after transfer, are associated with better outcomes. We report herein that exposure to exogenous TGFβ during human T-cell stimulation ex vivo leads to the accumulation of early/central memory (Tcm) cells. Exposure to TGFβ suppressed the expression of BLIMP-1, a key orchestrator of effector T-cell differentiation, and led to the upregulation of the memory-associated transcription factor ID3. Accordingly, this was associated with an early memory transcriptional signature in both CD4⁺ and CD8⁺ T-cell subsets. The T cells stimulated in the presence of TGFβ expanded normally, and displayed polyfunctional features and no suppressive activity. The adoptive transfer of ex vivo-stimulated T cells into immunodeficient mice confirmed that TGFβ-conditioned cells had an enhanced capacity to persist and mediate xenogeneic graft-versus-host disease, as predicted by their early T-cell memory phenotype. Chimeric antigen receptor-expressing T cells generated in the presence of exogenous TGFβ were cytotoxic and more effective at controlling tumor growth in immunodeficient animals. This work unveils a new role for TGFβ in memory T-cell differentiation and indicates that TGFβ signaling may be harnessed to program Tcm differentiation in the context of ex vivo T-cell stimulation for adoptive immunotherapy in humans.

Neutrophil extracellular traps (NETs) contribute to pathological changes of ocular graft-vs.-host disease (oGVHD) dry eye: Implications for novel biomarkers and therapeutic strategies

PURPOSE

To investigate the role of neutrophil extracellular traps (NETs) and NET-associated proteins in the pathogenesis of oGVHD and whether dismantling of NETs with heparin reduces those changes.

METHODS

Ocular surface washings from oGVHD patients and healthy subjects were analyzed. Isolated peripheral blood human neutrophils were stimulated to generate NETs and heparinized NETs. We performed in vitro experiments using cell lines (corneal epithelial, conjunctival fibroblast, meibomian gland (MG) epithelial and T cells), and in vivo experiments using murine models, and compared the effects of NETs, heparinized NETs, NET-associated proteins and neutralizing antibodies to NET-associated proteins.

RESULTS

Neutrophils, exfoliated epithelial cells, NETs and NET-associated proteins (extracellular DNA, Neutrophil Elastase, Myeloperoxidase, Oncostatin M (OSM), Neutrophil gelatinase-associated lipocalin (NGAL) and LIGHT/TNFSF14) are present in ocular surface washings (OSW) and mucocellular aggregates (MCA). Eyes with high number of neutrophils in OSW have more severe signs and symptoms of oGVHD. NETs (and OSM) cause epitheliopathy in murine corneas. NETs (and LIGHT/TNFSF14) increase proliferation of T cells. NETs (and NGAL) inhibit proliferation and differentiation of MG epithelial cells. NETs enhance proliferation and myofibroblast transformation of conjunctival fibroblasts. Sub-anticoagulant dose Heparin (100 IU/mL) dismantles NETs and reduces epithelial, fibroblast, T cell and MG cell changes induced by NETs.

CONCLUSION

NETs and NET-associated proteins contribute to the pathological changes of oGVHD (corneal epitheliopathy, conjunctival cicatrization, ocular surface inflammation and meibomian gland disease). Our data points to the potential of NET-associated proteins (OSM or LIGHT/TNFSF14) to serve as biomarkers and NET-dismantling biologics (heparin eye drops) as treatment for oGVHD.

Robust Identification of Suitable T-Cell Subsets for Personalized CMV-Specific T-Cell Immunotherapy Using CD45RA and CD62L Microbeads

Viral infections and reactivations remain a serious obstacle to successful hematopoietic stem cell transplantation (HSCT). When antiviral drug treatment fails, adoptive virus-specific T-cell transfer provides an effective alternative. Assuming that naive T cells (T_N) are mainly responsible for GvHD, methods were developed to generate naive T-cell-depleted products while preserving immune memory against viral infections. We compared two major strategies to deplete potentially alloreactive T cells: CD45RA and CD62L depletion and analyzed phenotype and functionality of the resulting CD45RA^-/CD62L^- naive T-cell-depleted as well as CD45RA⁺/CD62L⁺ naive T-cell-enriched fractions in the CMV pp65 and IE1 antigen model. CD45RA depletion resulted in loss of terminally differentiated effector memory T cells re-expressing CD45RA (T_EMRA), and CD62L depletion in loss of central memory T cells (T_CM). Based on these differences in target cell-dependent and target cell-independent assays, antigen-specific T-cell responses in CD62L-depleted fraction were consistently 3⁻5 fold higher than those in CD45RA-depleted fraction. Interestingly, we also observed high donor variability in the CD45RA-depleted fraction, resulting in a substantial loss of immune memory. Accordingly, we identified donors with expected response (DER) and unexpected response (DUR). Taken together, our results showed that a naive T-cell depletion method should be chosen individually, based on the immunophenotypic composition of the T-cell populations present.

Clinical Proteomics for Post-Hematopoeitic Stem Cell Transplantation Outcomes

Allogeneic hematopoietic stem cell transplantation (HSCT) is the most effective form of tumor immunotherapy available to date. However, while HSCT can induce beneficial graft-versus-leukemia (GVL) effect, the adverse effect of graft-versus-host disease (GVHD), which is closely linked to GVL, is the major source of morbidity and mortality following HSCT. Until recently, available diagnostic and staging tools frequently fail to identify those at higher risk of disease progression or death. Furthermore, there are shortcomings in the prediction of the need for therapeutic interventions or the response rates to different forms of therapy. The past decade has been characterized by an explosive evolution of proteomics technologies, largely due to important advances in high-throughput MS instruments and bioinformatics. Building on these opportunities, blood biomarkers have been identified and validated both as promising diagnostic tools, prognostic tools that risk-stratify patients before future occurrence of GVHD and as predictive tools for responsiveness to GVHD therapy and non-relapse mortality. These biomarkers might facilitate timely and selective therapeutic intervention. This review summarizes current information on clinical proteomics for GVHD as well as other complications following HSCT. Finally, it proposes future directions for the translation of clinical proteomics to discovery of new potential therapeutic targets to the development of drugs.

Indoles derived from intestinal microbiota act via type I interferon signaling to limit graft-versus-host disease

The intestinal microbiota in allogeneic bone marrow transplant (allo-BMT) recipients modulates graft-versus-host disease (GVHD), a systemic inflammatory state initiated by donor T cells that leads to colitis, a key determinant of GVHD severity. Indole or indole derivatives produced by tryptophan metabolism in the intestinal microbiota limit intestinal inflammation caused by diverse stressors, so we tested their capacity to protect against GVHD in murine major histocompatibility complex-mismatched models of allo-BMT. Indole effects were assessed by colonization of allo-BMT recipient mice with tryptophanase positive or negative strains of Escherichia coli, or, alternatively, by exogenous administration of indole-3-carboxaldehyde (ICA), an indole derivative. Treatment with ICA limited gut epithelial damage, reduced transepithelial bacterial translocation, and decreased inflammatory cytokine production, reducing GVHD pathology and GVHD mortality, but did not compromise donor T-cell-mediated graft-versus-leukemia responses. ICA treatment also led to recipient-strain-specific tolerance of engrafted T cells. Transcriptional profiling and gene ontology analysis indicated that ICA administration upregulated genes associated with the type I interferon (IFN1) response, which has been shown to protect against radiation-induced intestinal damage and reduce subsequent GVHD pathology. Accordingly, protective effects of ICA following radiation exposure were abrogated in mice lacking IFN1 signaling. Taken together, these data indicate that indole metabolites produced by the intestinal microbiota act via type I IFNs to limit intestinal inflammation and damage associated with myeloablative chemotherapy or radiation exposure and acute GVHD, but preserve antitumor responses, and may provide a therapeutic option for BMT patients at risk for GVHD.

GVHD: biology matters

Acute graft-versus-host disease (GVHD) targets the crypts in the gastrointestinal (GI) tract that are responsible for the self-renewal of the intestinal mucosa. Recent advances in the identification and culture of intestinal stem cells have improved our understanding of the interactions between the microbiome and the immune system (both innate and adaptive) that are key to the pathophysiology of GVHD. The identification of serum biomarkers that best predict long-term GVHD outcomes derive from the GI tract and have focused attention on cellular elements that act as shields against GVHD as well as its targets. These biomarkers have illuminated new mechanisms of crypt biology and provided insights that should prove useful both in the design of clinical trials and as guides to GVHD prevention and treatment.