High Number of Memory T Cells Is Associated with Higher Risk of Acute Graft-versus-Host Disease after Allogeneic Stem Cell Transplantation

Therapeutic Potential of a Senolytic Approach in a Murine Model of Chronic GVHD

Graft-versus-host disease (GVHD) is a life-threatening systemic complication of allogeneic hematopoietic stem cell transplantation (HSCT) characterized by dysregulation of T and B cell activation and function, scleroderma-like features, and multi-organ pathology. The treatment of cGVHD is limited to the management of symptoms and long-term use of immunosuppressive therapy, which underscores the need for developing novel treatment approaches. Notably, there is a striking similarity between cytokines/chemokines responsible for multi-organ damage in cGVHD and pro-inflammatory factors, immune modulators, and growth factors secreted by senescent cells upon the acquisition of senescence-associated secretory phenotype (SASP). In this pilot study, we questioned the involvement of senescent cell-derived factors in the pathogenesis of cGVHD triggered upon allogeneic transplantation in an irradiated host. Using a murine model that recapitulates sclerodermatous cGVHD, we investigated the therapeutic efficacy of a senolytic combination of dasatinib and quercetin (DQ) administered after 10 days of allogeneic transplantation and given every 7 days for 35 days. Treatment with DQ resulted in a significant improvement in several physical and tissue-specific features, such as alopecia and earlobe thickness, associated with cGVHD pathogenesis in allograft recipients. DQ also mitigated cGVHD-associated changes in the peripheral T cell pool and serum levels of SASP-like cytokines, such as IL-4, IL-6 and IL-8Rα. Our results support the involvement of senescent cells in the pathogenesis of cGVHD and provide a rationale for the use of DQ, a clinically approved senolytic approach, as a potential therapeutic strategy.

Naive T Cells in Graft Versus Host Disease and Graft Versus Leukemia: Innocent or Guilty?

The outcome of allogeneic hematopoietic cell transplantation (allo-HCT) largely depends on the development and management of graft-versus-host disease (GvHD), infections, and the occurrence of relapse of malignancies. Recent studies showed a lower incidence of chronic GvHD and severe acute GvHD in patients receiving naive T cell depleted grafts compared to patients receiving complete T cell depleted grafts. On the other hand, the incidence of acute GvHD in patients receiving cord blood grafts containing only naive T cells is rather low, while potent graft-versus-leukemia (GvL) responses have been observed. These data suggest the significance of naive T cells as both drivers and regulators of allogeneic reactions. The naive T cell pool was previously thought to be a quiescent, homogenous pool of antigen-inexperienced cells. However, recent studies showed important differences in phenotype, differentiation status, location, and function within the naive T cell population. Therefore, the adequate recovery of these seemingly innocent T cells might be relevant in the imminent allogeneic reactions after allo-HCT. Here, an extensive review on naive T cells and their contribution to the development of GvHD and GvL responses after allo-HCT is provided. In addition, strategies specifically directed to stimulate adequate reconstitution of naive T cells while reducing the risk of GvHD are discussed. A better understanding of the relation between naive T cells and alloreactivity after allo-HCT could provide opportunities to improve GvHD prevention, while maintaining GvL effects to lower relapse risk.

LPSlow-Macrophages Alleviate the Outcome of Graft-Versus-Host Disease Without Aggravating Lymphoma Growth in Mice

Despite significant therapeutic advances, graft-versus-host disease (GvHD) remains the main life-threatening complication following allogeneic hematopoietic stem cell transplantation. The pathogenesis of GvHD is dominated by a dysregulated allogeneic immune response that drives fibrosis and autoimmunity in chronic forms. A multitude of cell therapy approaches, including infusion of myeloid cells, has been proposed to prevent GvHD through tolerance induction but yielded variable results. Myeloid cells like macrophages can be reprogrammed to develop adaptive-like features following antigenic challenge to reinforce or inhibit a subsequent immune response; a phenomenon termed ‘trained immunity’. Here we report that, whereas LPS^low-trained macrophages elicit a suppressor effect on allogeneic T cell proliferation and function in vitro in an IL-10-dependent manner, Bacille Calmette et Guérin (BCG)-trained macrophages exert an opposite effect. In a murine model of sclerodermatous chronic GvHD, LPS^low-trained macrophages attenuate clinical signs of GvHD with significant effects on T cell phenotype and function, autoantibodies production, and tissue fibrosis. Furthermore, infusion of LPS^low-macrophages significantly improves survival in mice with acute GvHD. Importantly, we also provide evidence that LPS^low-macrophages do not accelerate A20-lymphoma tumor growth, which is significantly reduced upon transfer of BCG-macrophages. Collectively, these data indicate that macrophages can be trained to significantly inhibit in vitro and in vivo allo-reactive T cell proliferation without exhibiting pro-tumoral effect, thereby opening the way to promising clinical applications.

Comprehensive analysis of the immunomodulatory effects of rapamycin on human T cells in graft-versus-host disease prophylaxis

Graft-versus-host disease (GVHD) is a major cause of toxicity after allogeneic hematopoietic cell transplantation (allo-HCT). While rapamycin (RAPA) is commonly used in GVHD prophylaxis in combination with a calcineurin inhibitor (CNI), the understanding of its mechanism of action on human T cells is still incomplete. Here, we performed an extensive analysis of RAPA effects on human T cells in a humanized mouse model of GVHD, in ex-vivo T cell cultures and in patients given RAPA plus tacrolimus as GVHD prophylaxis after nonmyeloablative allo-HCT. We demonstrate that RAPA mitigates GVHD by decreasing T cell engraftment and differentiation, inhibiting CD8⁺ T cell activation and increasing the long-term IL-2 secretion, thereby supporting regulatory T cell (Treg) proliferation. In contrast, graft-versus-leukemia effects were not abrogated, as RAPA-treated T cells had increased resistance to apoptosis and retained their effector function and proliferative capacity upon re-stimulation. Importantly, we found that RAPA impact on Treg and CD8⁺ T cells was closely dependent upon IL-2 signaling and that therapeutic options interfering with IL-2, such as calcineurin inhibitors, antagonize the IL-2-dependent promotion of Treg mediated by RAPA. Our results suggest that RAPA immunological efficacy could be improved in combination with drugs having possible synergistic effects such as the hypomethylating agent 5-azacytidine.

Post-transplant cyclophosphamide limits reactive donor T cells and delays the development of graft-versus-host disease in a humanized mouse model

Graft-versus-host disease (GVHD) is a major complication of allogeneic haematopoietic stem cell transplantation (allo-HSCT) that develops when donor T cells in the graft become reactive against the host. Post-transplant cyclophosphamide (PTCy) is increasingly used in mismatched allo-HSCT, but how PTCy impacts donor T cells and reduces GVHD is unclear. This study aimed to determine the effect of PTCy on reactive human donor T cells and GVHD development in a preclinical humanized mouse model. Immunodeficient NOD-scid-IL2Rγ^null mice were injected intraperitoneally (i.p.) with 20 × 10⁶ human peripheral blood mononuclear cells stained with carboxyfluorescein succinimidyl ester (CFSE) (day 0). Mice were subsequently injected (i.p.) with PTCy (33 mg kg^-1 ) (PTCy-mice) or saline (saline-mice) (days 3 and 4). Mice were assessed for T-cell depletion on day 6 and monitored for GVHD for up to 10 weeks. Flow cytometric analysis of livers at day 6 revealed lower proportions of reactive (CFSE^low ) human (h) CD3⁺ T cells in PTCy-mice compared with saline-mice. Over 10 weeks, PTCy-mice showed reduced weight loss and clinical GVHD, with prolonged survival and reduced histological liver GVHD compared with saline-mice. PTCy-mice also demonstrated increased splenic hCD4⁺ :hCD8⁺ T-cell ratios and reduced splenic Tregs (hCD4⁺  hCD25⁺  hCD127^lo ) compared with saline-mice. This study demonstrates that PTCy reduces GVHD in a preclinical humanized mouse model. This corresponded to depletion of reactive human donor T cells, but fewer human Tregs.

CD69+ resident memory T cells are associated with graft-versus-host disease in intestinal transplantation

Graft-versus-host disease (GvHD) is a common, morbid complication after intestinal transplantation (ITx) with poorly understood pathophysiology. Resident memory T cells (T_RM ) are a recently described CD69+ memory T cell subset localizing to peripheral tissue. We observed that T effector memory cells (T_EM ) in the blood increase during GvHD and hypothesized that they derive from donor graft CD69+T_RM migrating into host blood and tissue. To probe this hypothesis, graft and blood lymphocytes from 10 ITx patients with overt GvHD and 34 without were longitudinally analyzed using flow cytometry. As hypothesized, CD4+ and CD8+CD69+T_RM were significantly increased in blood and grafts of GvHD patients, alongside higher cytokine and activation marker expression. The majority of CD69+T_RM were donor derived as determined by multiplex immunostaining. Notably, CD8/PD-1 was significantly elevated in blood prior to transplantation in patients who later had GvHD, and percentages of HLA-DR, CD57, PD-1, and naïve T cells differed significantly between GvHD patients who died vs. those who survived. Overall, we demonstrate that (1) there were significant increases in T_EM at the time of GvHD, possibly of donor derivation; (2) donor T_RM in the graft are a possible source; and (3) potential biomarkers for the development and prognosis of GvHD exist.

Targeting SLP76:ITK interaction separates GVHD from GVL in allo-HSCT

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a curative therapy for hematological malignancies, due to graft-versus-leukemia (GVL) activity mediated by alloreactive donor T cells. However, graft-versus-host disease (GVHD) is also mediated by these cells. Here, we assessed the effect of attenuating TCR-mediated SLP76:ITK interaction in GVL vs. GVHD effects after allo-HSCT. CD8+ and CD4+ donor T cells from mice expressing a Y145F mutation in SLP-76 did not cause GVHD but preserved GVL effects against B-ALL cells. SLP76Y145FKI CD8+ and CD4+ donor T cells also showed less inflammatory cytokine production and migration to GVHD target organs. We developed a novel peptide to specifically inhibit SLP76:ITK interactions, resulting in decreased phosphorylation of PLCγ1 and ERK, decreased cytokine production in human T cells, and separation of GVHD from GVL effects. Altogether, our data suggest that inhibiting SLP76:ITK interaction could be a therapeutic strategy to separate GVHD from GVL effects after allo-HSCT treatment.

Intestinal CD8+ T cell responses are abundantly induced early in human development but show impaired cytotoxic effector capacities

Gastrointestinal viral infections are a major global cause of disease and mortality in infants. Cytotoxic CD8⁺ T cells are critical to achieve viral control. However, studies investigating the development of CD8⁺ T cell immunity in human tissues early in life are lacking. Here, we investigated the maturation of the CD8⁺ T cell compartment in human fetal, infant and adult intestinal tissues. CD8⁺ T cells exhibiting a memory phenotype were already detected in fetal intestines and increased after birth. Infant intestines preferentially harbored effector CCR7^-CD45RA^-CD127^-KLRG1^+/- CD8⁺ T cells compared to tissue-resident memory CD69⁺CD103⁺CD8⁺ T cells detected in adults. Functional cytotoxic capacity, including cytokine and granzyme B production of infant intestinal effector CD8⁺ T cells was, however, markedly reduced compared to adult intestinal CD8⁺ T cells. This was in line with the high expression of the inhibitory molecule PD-1 by infant intestinal effector CD8⁺ T cells. Taken together, we demonstrate that intestinal CD8⁺ T cell responses are induced early in human development, however exhibit a reduced functionality. The impaired CD8⁺ T cell functionality early in life contributes to tolerance during foreign antigen exposure after birth, however functions as an immune correlate for the increased susceptibility to gastrointestinal viral infections in infancy.

CD4+CD8+ T-Lymphocytes in Xenogeneic and Human Graft-versus-Host Disease

Mechanisms driving acute graft-versus-host disease (aGVHD) onset in patients undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT) are still poorly understood. To provide a detailed characterization of tissue-infiltrating T lymphocytes (TL) and search for eventual site-specific specificities, we developed a xenogeneic model of aGVHD in immunodeficient mice. Phenotypic characterization of xenoreactive T lymphocytes (TL) in diseased mice disclosed a massive infiltration of GVHD target organs by an original CD4⁺CD8⁺ TL subset. Immunophenotypic and transcriptional profiling shows that CD4⁺CD8⁺ TL comprise a major PD1⁺CD62L^−/+ transitional memory subset (>60%) characterized by low level expression of cytotoxicity-related transcripts. CD4⁺CD8⁺ TL produce high IL-10 and IL-13 levels, and low IL-2 and IFN-γ, suggestive of regulatory function. In vivo tracking of genetically labeled CD4⁺ or CD8⁺ TL subsequently found that CD4⁺CD8⁺ TL mainly originate from chronically activated cytotoxic TL (CTL). On the other hand, phenotypic profiling of CD3⁺ TL from blood, duodenum or rectal mucosa in a cohort of allo-HSCT patients failed to disclose abnormal expansion of CD4⁺CD8⁺ TL independent of aGVHD development. Collectively, our results show that acquisition of surface CD4 by xenoreactive CD8⁺ CTL is associated with functional diversion toward a regulatory phenotype, but rule out a central role of this subset in the pathogenesis of aGVHD in allo-HSCT patients.

Expanding Therapeutic Opportunities for Hematopoietic Stem Cell Transplantation: T Cell Depletion as a Model for the Targeted Allograft

Allogeneic hematopoietic cell transplantation is a fundamental part of the treatment of hematologic malignancies and marrow failure syndromes, but complications including graft-versus-host disease, prolonged immune deficiency and infection, and organ toxicities, as well as relapse, remain obstacles to improved overall survival. As the cellular characteristics of the allograft can exert significant impact on outcomes, the development of more strategically designed grafts represents a rich area for therapeutic intervention. We describe the use of ex vivo T cell–depleted grafts as a model for the targeted graft and review evolving knowledge and approaches for further refinement of allografts to improve patient outcomes.

Pre-transplant donor CD4- invariant NKT cell expansion capacity predicts the occurrence of acute graft-versus-host disease

Clinically useful pre-transplant predictive factors of acute graft-versus-host-disease (aGVHD) after allogeneic hematopoietic stem cell transplantation (allo-SCT) are lacking. We prospectively analyzed HSC graft content in CD34⁺, NK, conventional T, regulatory T and invariant natural killer T (iNKT) cells in 117 adult patients before allo-SCT. Results were correlated with occurrence of aGVHD and relapse. In univariate analysis, iNKT cells were the only graft cell populations associated with occurrence of aGVHD. In multivariate analysis, CD4^- iNKT/T cell frequency could predict grade II-IV aGVHD in bone marrow and peripheral blood stem cell (PBSC) grafts, while CD4^- iNKT expansion capacity was predictive in PBSC grafts. Receiver operating characteristic analyses determined the CD4^- iNKT expansion factor as the best predictive factor of aGVHD. Incidence of grade II-IV aGVHD was reduced in patients receiving a graft with an expansion factor above versus below 6.83 (9.7 vs 80%, P<0.0001), while relapse incidence at two years was similar (P=0.5).The test reached 94% sensitivity and 100% specificity in the subgroup of patients transplanted with human leukocyte antigen 10/10 PBSCs without active disease. Analysis of this CD4^- iNKT expansion capacity test may represent the first diagnostic tool allowing selection of the best donor to avoid severe aGVHD with preserved graft-versus-leukemia effect after peripheral blood allo-SCT.

Allogeneic unrelated bone marrow transplantation from older donors results in worse prognosis in recipients with aplastic anemia

Allogeneic bone marrow transplantation is an essential therapy for acquired aplastic anemia and prognosis has recently improved. However, engraftment failure and graft-versus-host disease are potential fatal complications. Various risk factors for poor prognosis have been identified, such as patient age and human-leukocyte antigen disparity, but the relationship between donor age and prognosis is still unknown. Therefore, we performed a cohort study to compare the prognosis of unrelated bone marrow transplantation from younger and older donors using the registry database in Japan. We evaluated 427 patients (age 16-72 years) with aplastic anemia who underwent bone marrow transplantation from younger (≤39 years, n=281) or older (≥40 years, n=146) unrelated donors. Overall survival of the older donor group was significantly inferior to that of the younger donor group (adjusted hazard ratio 1.64; 95% confidence interval 1.15-2.35; P<0.01). The incidence of fatal infection was significantly higher in the older donor group (13.7% vs. 7.5%; P=0.03). Primary engraftment failure and acute graft-versus-host disease were significantly more frequent in the older donor group (9.7% vs. 5.0%; adjusted hazard ratio 1.30; P=0.01, and 27.1% vs. 19.7%; adjusted hazard ratio 1.56; P=0.03, respectively). Acute graft-versus-host disease was related to a worse prognosis in the whole cohort. This study showed the inferiority of older donors in aplastic anemia; thus, donor age should be considered when multiple donors are available. A large-scale prospective study is warranted to establish a better donor selection algorithm for bone marrow transplantation in aplastic anemia.

Unrelated cord blood transplantation for adult patients with acute myeloid leukemia: higher incidence of acute graft-versus-host disease and lower survival in male patients transplanted with female unrelated cord blood--a report from Eurocord, the Acute Leukemia Working Party, and the Cord Blood Committee of the Cellular Therapy and Immunobiology Working Party of the European Group for Blood and Marrow Transplantation

Background

In the setting of allogeneic human leukocyte antigen (HLA)-matched bone marrow transplantation, transplanting male patients with grafts from female donors has been associated with a higher incidence of graft-versus-host disease (GVHD) and of nonrelapse mortality (NRM). The aim of the current analysis was to compare transplantation outcomes in male patients given female unrelated cord blood (UCB) versus other gender combinations.

Patients and methods

Data from 552 consecutive patients with acute myeloid leukemia (AML) given a single UCB transplantation between 2000 and 2014 were included.

Results

In comparison with other gender combination, male patients given female UCB (n = 131) had a trend for a higher incidence of grades II–IV acute GVHD (33 versus 25 %, P = 0.08), a trend for a higher incidence of NRM (41 versus 33 %, P = 0.06), and a lower leukemia-free (LFS, 30 versus 41 %, P = 0.01) and overall survival (OS, 33 versus 45 %, P = 0.008). In multivariate analyses, taking into consideration all patients for which data on HLA-matching and cell dose transplanted were fully available (n = 363), male patients transplanted with a female UCB had a trend for a higher incidence of grade III–IV acute GVHD (hazard ratio (HR) = 2.0, P = 0.06), a trend for a higher NRM (HR = 1.5, P = 0.06), and a worse LFS (HR = 1.4, P = 0.04) and OS (HR = 1.3, P = 0.06).

Conclusions

Our data suggest that male patients transplanted with female UCB might have higher risk of acute GVHD and of NRM leading to worse LFS and OS. These results should be confirmed in other large cohorts of patients before used for determining the choice of an UCB unit.

Electronic supplementary material

The online version of this article (doi:10.1186/s13045-015-0207-4) contains supplementary material, which is available to authorized users.