Insights from integrating clinical and preclinical studies advance understanding of graft-versus-host disease

Ruxolitinib plus steroids for acute graft versus host disease: a multicenter, randomized, phase 3 trial

Newly diagnosed patients with high-risk acute graft-versus-host disease (aGVHD) often experience poor clinical outcomes and low complete remission rates. Ruxolitinib with corticosteroids showed promising efficacy in improving response and failure free survival in our phase I study. This study (ClinicalTrials.gov: NCT04061876) sought to evaluate the safety and effectiveness of combining ruxolitinib (RUX, 5 mg/day) with corticosteroids (1 mg/kg/day methylprednisolone, RUX/steroids combined group) versus using methylprednisolone alone (2 mg/kg/day, steroids-only group). Newly diagnosed patients with intermediate- or high-risk aGVHD were included, with risk levels classified by either the Minnesota aGVHD Risk Score or biomarker assessment. Patients were randomized in a ratio of 1:1 into 2 groups: 99 patients received RUX combined with methylprednisolone, while the other 99 received methylprednisolone alone as the initial treatment. The RUX/steroids group showed a significantly higher overall response rate (ORR) on day 28 (92.9%) compared to the steroids-only group (70.7%, Odds Ratio [OR] = 5.8; 95% Confidence Interval [CI], 2.4-14.0; P < 0.001). Similarly, the ORR on day 56 was higher in the RUX/steroids group (85.9% vs. 46.5%; OR = 7.07; 95% CI, 3.36-15.75; P < 0.001). Additionally, the 18-month failure-free survival was significantly better in the RUX/steroids group (57.2%) compared to the steroids-only group (33.3%; Hazard Ratio = 0.46; 95% CI, 0.31-0.68; P < 0.001). Adverse events (AEs) frequencies were comparable between both groups, with the exception of fewer grade 4 AEs in the RUX/steroids group (26.3% vs. 50.5% P = 0.005). To our knowledge, this study is the first prospective, randomized controlled trial to demonstrate that adding ruxolitinib to the standard methylprednisolone regimen provides an effective and safe first-line treatment for newly diagnosed high-risk acute GVHD.

Current Approaches for the Prevention and Treatment of Acute and Chronic GVHD

Whereas aGVHD has strong inflammatory components, cGVHD displays autoimmune and fibrotic features; incidence and risk factors are similar but not identical; indeed, the aGVHD is the main risk factor for cGVHD. Calcineurin Inhibitors (CNI) with either Methotrexate (MTX) or Mycophenolate (MMF) still represent the standard prophylaxis in HLA-matched allogeneic stem cell transplantation (HSCT); other strategies focused on ATG, Post-Transplant Cyclophosphamide (PTCy), Abatacept and graft manipulation. Despite the high rate, first-line treatment for aGVHD is represented by corticosteroids, and Ruxolitinib is the standard second-line therapy; investigational approaches include Microbiota transplant and the infusion of Mesenchymal stem cells. GVHD is a pleiotropic disease involving any anatomical district; also, Ruxolitinib represents the standard for steroid-refractory cGVHD in this setting. It is a pleiotropic disease involving any anatomical district; also, Ruxolitinib represents the standard for steroid-refractory cGVHD in this setting. Extracorporeal Photopheresis (ECP) is still an option used for steroid refractoriness or to achieve a steroid-sparing. For Ruxolitinib-refractory cGVHD, Belumosudil and Axatilimab represent the most promising agents. Bronchiolitis obliterans syndrome (BOS) still represents a challenge; among the compounds targeting non-immune effectors, Alvelestat, a Neutrophil elastase inhibitor, seems promising in BOS. Finally, in both aGVHD and cGVHD, the association of biological markers with specific disease manifestations could help refine risk stratification and the availability of reliable biomarkers for specific treatments.

The graft versus leukemia effect: donor lymphocyte infusions and cellular therapy

Allogeneic hematopoietic stem cell transplantation (HSCT) is a potentially curative therapy for many hematologic malignancies as well as non-malignant conditions. Part of the curative basis underlying HSCT for hematologic malignancies relies upon induction of the graft versus leukemia (GVL) effect in which donor immune cells recognize and eliminate residual malignant cells within the recipient, thereby maintaining remission. GVL is a clinically evident phenomenon; however, specific cell types responsible for inducing this effect and molecular mechanisms involved remain largely undefined. One of the best examples of GVL is observed after donor lymphocyte infusions (DLI), an established therapy for relapsed disease or incipient/anticipated relapse. DLI involves infusion of peripheral blood lymphocytes from the original HSCT donor into the recipient. Sustained remission can be observed in 20-80% of patients treated with DLI depending upon the underlying disease and the intrinsic burden of targeted cells. In this review, we will discuss current knowledge about mechanisms of GVL after DLI, experimental strategies for augmenting GVL by manipulation of DLI (e.g. neoantigen vaccination, specific cell type selection/depletion) and research outlook for improving DLI and cellular immunotherapies for hematologic malignancies through better molecular definition of the GVL effect.

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

ABSTRACT

Acute 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.

Human MAIT cells inhibit alloreactive T cell responses and protect against acute graft-versus-host disease

Adoptive transfer of immunoregulatory cells can prevent or ameliorate graft-versus-host disease (GVHD), which remains the main cause of nonrelapse mortality after allogeneic hematopoietic stem cell transplantation. Mucosal-associated invariant T (MAIT) cells were recently associated with tissue repair capacities and with lower rates of GVHD in humans. Here, we analyzed the immunosuppressive effect of MAIT cells in an in vitro model of alloreactivity and explored their adoptive transfer in a preclinical xenogeneic GVHD model. We found that MAIT cells, whether freshly purified or short-term expanded, dose-dependently inhibited proliferation and activation of alloreactive T cells. In immunodeficient mice injected with human PBMCs, MAIT cells greatly delayed GVHD onset and decreased severity when transferred early after PBMC injection but could also control ongoing GVHD when transferred at delayed time points. This effect was associated with decreased proliferation and effector function of human T cells infiltrating tissues of diseased mice and was correlated with lower circulating IFN-γ and TNF-α levels and increased IL-10 levels. MAIT cells acted partly in a contact-dependent manner, which likely required direct interaction of their T cell receptor with MHC class I-related molecule (MR1) induced on host-reactive T cells. These results support the setup of clinical trials using MAIT cells as universal therapeutic tools to control severe GVHD or mucosal inflammatory disorders.

Chronic GvHD NIH Consensus Project Biology Task Force: evolving path to personalized treatment of chronic GvHD

Chronic graft-versus-host disease (cGvHD) remains a prominent barrier to allogeneic hematopoietic stem cell transplantion as the leading cause of nonrelapse mortality and significant morbidity. Tremendous progress has been achieved in both the understanding of pathophysiology and the development of new therapies for cGvHD. Although our field has historically approached treatment from an empiric position, research performed at the bedside and bench has elucidated some of the complex pathophysiology of cGvHD. From the clinical perspective, there is significant variability of disease manifestations between individual patients, pointing to diverse biological underpinnings. Capitalizing on progress made to date, the field is now focused on establishing personalized approaches to treatment. The intent of this article is to concisely review recent knowledge gained and formulate a path toward patient-specific cGvHD therapy.

Generalized Vitiligo After Stem Cell Transplantation: A Case Report

Graft versus host disease (GVHD) is a complex immune-mediated pathophysiological process, which is caused by allogenic immune reactions between donors and recipients. No matter ac-ute or chronic GVHD, skin involvement is the most common, severe skin damage can lead to permanent disfigurement, which seriously affects the long-term quality of life of patients. We herein report a patient with generalized vitiligo after allogeneic peripheral hematopoietic stem cell transplantation (allo-HSCT) for aplastic anemia.

Effect of mTOR Inhibition with Sirolimus on Natural Killer Cell Reconstitution in Allogeneic Stem Cell Transplantation

Sirolimus is an inhibitor of the mammalian target of rapamycin (mTOR) and is emerging as a promising component of graft-versus-host disease (GVHD) prophylaxis regimens in the context of allogeneic hematopoietic stem cell transplantation (HSCT). Multiple studies have explored the clinical benefits of adding sirolimus to GVHD prophylaxis; however, detailed immunologic studies have not yet been carried out in this context. Mechanistically, mTOR is at the center of metabolic regulation in T cells and natural killer (NK) cells and is critical for their differentiation to mature effector cells. Therefore, close evaluation of the inhibition of mTOR in the context of immune reconstitution post-HSCT is warranted. In this work, we studied the effect of sirolimus on immune reconstitution using a biobank of longitudinal samples from patients receiving either tacrolimus/sirolimus (TAC/SIR) or cyclosporin A/methotrexate (CSA/MTX) as conventional GVHD prophylaxis. Healthy donor controls, donor graft material, and samples from 28 patients (14 with TAC/SIR, 14 with CSA/MTX) at 3 to 4 weeks and 34 to 39 weeks post- HSCT were collected. Multicolor flow cytometry was used to perform broad immune cell mapping, with a focus on NK cells. NK cell proliferation was evaluated over a 6-day in vitro homeostatic proliferation protocol. Furthermore, in vitro NK cell responses to cytokine stimulation or tumor cells were evaluated. Systems-level assessment of the immune repertoire revealed a deep and prolonged suppression (weeks 34 to 39 post-HSCT) of the naïve CD4 T cell compartment with relative sparing of regulatory T cells and enrichment of CD69⁺Ki-67⁺HLA-DR⁺ CD8 T cells, independent of the type of GVHD prophylaxis. Early after transplantation (weeks 3 to 4), while patients were still on TAC/SIR or CSA/MTX, we found a relative increase in less-differentiated CD56^bright NK cells and NKG2A⁺CD57^-KIR^- CD56^dim NK cells and a distinct loss of CD16 and DNAM-1 expression. Both regimens led to suppressed proliferative responses ex vivo and functional impairment with preferential loss of cytokine responsiveness and IFN-γ production. Patients who received TAC/SIR as GVHD prophylaxis showed delayed NK cell reconstitution with lower overall NK cell counts and fewer CD56^bright and NKG2A⁺ CD56^dim NK cells. Treatment with sirolimus- containing regimens generated similar immune cell profiles as conventional prophylaxis; however, the NK cell compartment seemed to be composed of slightly more mature NK cells. These effects were also present after the completion of GVHD prophylaxis, suggesting that mTOR inhibition with sirolimus leaves a lasting imprint on homeostatic proliferation and NK cell reconstitution following HSCT.

Trafficking between clonally related peripheral T-helper cells and tissue-resident T-helper cells in chronic GVHD

Chronic graft-versus-host disease (cGVHD) is an autoimmune-like syndrome. CXCR5-PD-1hi peripheral T-helper (Tph) cells have an important pathogenic role in autoimmune diseases, but the role of Tph cells in cGVHD remains unknown. We show that in patients with cGVHD, expansion of Tph cells among blood CD4+ T cells was associated with cGVHD severity. These cells augmented memory B-cell differentiation and production of immunoglobulin G via interleukin 21 (IL-21). Tph cell expansion was also observed in a murine model of cGVHD. This Tph cell expansion in the blood is associated with the expansion of pathogenic tissue-resident T-helper (Trh) cells that form lymphoid aggregates surrounded by collagen in graft-versus-host disease (GVHD) target tissues. Adoptive transfer experiments showed that Trh cells from GVHD target tissues give rise to Tph cells in the blood, and conversely, Tph cells from the blood give rise to Trh cells in GVHD target tissues. Tph cells in the blood and Trh cells in GVHD target tissues had highly overlapping T-cell receptor α and β repertoires. Deficiency of IL-21R, B-cell lymphoma 6 (BCL6), or T-bet in donor T cells markedly reduced the proportions of Tph cells in the blood and Trh cells in GVHD target tissues and reduced T-B interaction in the lymphoid aggregates. These results indicate that clonally related pathogenic Tph cells and Trh cells traffic between the blood and cGVHD target tissues, and that IL-21R-BCL6 signaling and T-bet are required for the development and expansion of Tph and Trh cells in the pathogenesis of cGVHD.

Milestones in acute GVHD pathophysiology

In the past 65 years, over 25 000 referenced articles have been published on graft-versus-host disease (GVHD). Although this included clinically orientated papers or publications on chronic GVHD, the conservative estimate of scientific publications still contains several thousands of documents on the pathophysiology of acute GVHD. Thus, summarizing what we believe are prominent publications that can be considered milestones in our knowledge of this disease is a challenging and inherently biased task. Here we review from a historical perspective what can be regarded as publications that have made the field move forward. We also included several references of reviews on aspects we could not cover in detail.

Blockade of PD-1/PD-L1 increases effector T cells and aggravates murine chronic graft-versus-host disease

T-cells mediated immunopathology is crucial for pathogenesis of chronic graft-versus-host disease (cGVHD), a common complication following allogeneic hematopoietic cell transplantation. Programmed death-1 (PD-1) regulates long-term survival and functional exhaustion of T-cell which might play a role in regulating cGVHD. We examined PD-1 expression on T cells of cGVHD mice and tested the impact of a PD-1 antibody on severity of cGVHD in murine allotransplant models. We also used a murine graft-versus-tumor (GVT) model to explore how tumor cell-derived PD-L1 affect the GVT effect and occurrence of cGVHD. PD-1 fluorescence intensity on CD4⁺ T-cells increased in mice developing cGVHD. PD-1^High T cells expressed higher levels of IFNγ and IL-17, comparing with PD-1^Low T cells. Giving the PD-1 antibody increased proportions of Th1, Th17 and Tc1 cells, but decreased proportion of Treg cells in allotransplant mice. The PD-1 antibody decreased survival of recipients and induced severe lung cGVHD. In the GVT model, knockdown of PD-L1 in A20 tumor cells enhanced GVT effect but increased cGVHD. In vitro study showed knockdown of PD-L1 in tumor cells increased cytotoxicity of T cells and reduced apoptosis of T cells. Knockdown of PD-L1 in tumor cells increased protein levels of phosphorylated AKT, Bcl-2 and Mcl-1, but decreased protein levels of Bak and Bax in co-cultured allogeneic T cells. In conclusion, expression of PD-1 on T cells increased in mice undergoing cGVHD. Intervention of the PD-1/PD-L1 pathway showed a significant impact on occurrence of cGVHD and GVT effect.

Organ-specific response after low-dose interleukin-2 therapy for steroid refractory chronic Graft-versus-Host Disease

Despite new therapeutic options, treatment of steroid-refractory chronic graft-versus-host disease (SR-cGVHD) remains challenging as organ involvement and clinical manifestations are highly variable. In previous trials of low-dose interleukin-2 (LD IL-2), we established the safety and efficacy of LD IL-2 for treatment of SR-cGVHD. In the present report, we combined 5 phase I or II clinical trials conducted at our center to investigate organ-specific response rate, co-involvement of organs, predictors of organ-specific response and its possible association with immune response. For 105 adult patients included in this report, the overall response rate after 8 or 12 weeks LD IL-2 was 48.6% and 53.3% including late responses in patients who continued treatment for extended periods. Skin was the most frequent organ involved (84%) and the organ-specific response rate was highest in liver (66.7%) followed by GI (62.5%), skin (36.4%), joint/muscle/fascia (34.2%) and lung (19.2%). In multivariable analysis, shorter time from diagnosis of cGVHD to IL-2 initiation, shorter time from transplant to IL-2 initiation, and fewer prior therapies were associated with overall response as well as skin response. For immunologic correlates, CD4Treg:CD4Tcon ratio at one week was significantly higher in patients with overall and skin response; skin response was significantly associated with lower number of total CD3 T cells, CD4Tcon and CD8 T cells and higher number of B cells. For lung responders, terminal effector memory cell counts were lower within all T cell populations compared to non-responders. Organ-specific mechanisms of injury should be investigated and organ-specific targeted therapies need to be developed.

Relationship between Iron deposition and T lymphocytes in children with β-thalassemia with haematopoietic stem cell transplantation

BACKGROUND

β-Thalassemia cellular immunity is associated with iron overload. However, the relationship between varying degrees of iron deposition and T cell immune recovery after allogeneic haematopoietic stem cell transplantation(allo-HSCT) in children remain unclear.

METHODS

A retrospective analysis was performed on 84 children with β-Thalassemia undergoing sibling allo-HSCT. According to the degrees of hepatic iron deposition, patients were divided into four classes. T lymphocyte counts were measured. Hepatic iron deposition was assessed by T2* MRI. Epstein-Barr virus and cytomegalovirus infection rates and graft-vs.-host disease incidence were recorded.

RESULTS

Immune recovery after allo-HSCT was compared between the two groups. Normal vs. mild group: CD4 cells were higher at 1, 3, and 6 months (P < 0.05), CD3 and CD8 cells were higher at 3 and 6 months, and 1 year in normal group (P < 0.05). Normal vs. moderate group: CD3 and CD4 cells were higher at 1, 3 and 6 months, and 1 year (P < 0.05), CD8 cells were higher at 1 and 3 months, and 1 year in normal group (P < 0.05). Normal vs. severe group: CD3, CD4 and CD8 cell at 1, 3 and 6 months, and 1 year in normal group (P < 0.05). Mild vs. moderate group: CD3, CD4 and CD8 cells were higher at 1 month in mild group (P < 0.05). Mild vs. severe group: CD4 cells were higher at 1, 3 and 6 month, and 1 year (P < 0.05), CD3 and CD8 cells were higher at 1 month in mild group (P < 0.05). Moderate vs. severe group: CD4 cells were higher at 3 months (P < 0.05), CD8 cells were higher at 6 months in moderate group (P < 0.05). The hepatic T2* values were positively correlated with CD3, CD4 and CD8 cells. The infection rates of Epstein-Barr virus and cytomegalovirus were significantly different among the groups (P < 0.05).

CONCLUSION

Iron deposition affects immune recovery of T lymphocytes after allo-HSCT in children with β-thalassemia. The lower the levels of iron deposition, the greater the CD4 cell count.