Separating graft-versus-leukemia from graft-versus-host disease in allogeneic hematopoietic stem cell transplantation

The impact of MICB mismatches in unrelated haematopoietic stem cell transplantation

MICA polymorphisms have been associated with increased incidence of acute GvHD and adverse outcome in allogeneic haematopoietic stem cell transplantation (HSCT). MICB is another expressed member of MHC class I-related chain genes and its impact on HSCT outcome is yet to be fully defined. We typed a large cohort of patients and donors for MICB polymorphisms and investigated the impact of MICB matching on outcome after unrelated HSCT. 69.2% of the patients were 10/10 human leukocyte antigen (HLA) matched and 30.8% were 9/10 HLA matched. MICB typing was performed using a short amplicon-based NGS typing assay on the Illumina MiSeq platform. Differences in proteins were considered as mismatches. MICA polymorphisms were identified as possible confounder and were therefore included as parameter in the multivariate analyses. Due to the strong linkage disequilibrium with the classical HLA-genes, sub-stratification for HLA matching status was necessary, and no effect of MICB mismatches was seen in the 10/10 HLA matched group when compared to the MICB matched cases. However, in the 9/10 HLA matched group, MICB mismatched cases showed significantly worse disease free survival (DFS), GvHD and relapse free survival (GRFS) compared to the MICB matched cases (DFS: HR 1.24, p = 0.011; GRFS: HR 1.26, p = 0.002). MICA mismatches had no impact on any outcome parameter. According to our findings, effects previously attributed to MICA differences may have been confounded by MICB polymorphisms. We show that MICB differences contribute a small but relevant effect in 9/10 HLA-matched transplantations, which in turn highlights the possible usefulness of MICB typing in donor selection among similarly suitable 9/10 matched donors, especially when HLA-B mismatches have to be accepted.

AMPK Drives Both Glycolytic and Oxidative Metabolism in T Cells During Graft-versus-host Disease

Allogeneic T cells reprogram their metabolism during acute graft-versus-host disease (GVHD) in a process reliant on the cellular energy sensor AMP-activated protein kinase (AMPK). Deletion of AMPK in donor T cells limits GVHD but still preserves homeostatic reconstitution and graft-versus-leukemia (GVL) effects. In the current studies, murine T cells lacking AMPK decreased oxidative metabolism at early timepoints post-transplant and were also unable to mediate a compensatory increase in glycolysis following inhibition of the electron transport chain. Human T cells lacking AMPK gave similar results, with glycolytic compensation impaired both in vitro and following expansion in vivo in a modified model of GVHD. Immunoprecipitation of proteins from day 7 allogeneic T cells, using an antibody specific to phosphorylated AMPK targets, recovered lower levels of multiple glycolysis-related proteins including the glycolytic enzymes aldolase, enolase, pyruvate kinase M (PKM), and glyceraldehyde 3-phosphate dehydrogenase (GAPDH). Functionally, murine T cells lacking AMPK exhibited impaired aldolase activity following anti-CD3/CD28 stimulation and a decrease in GAPDH activity on day 7 post-transplant. Importantly, these changes in glycolysis correlated with an impaired ability of AMPK KO T cells to produce significant amounts of interferon gamma (IFNγ) upon antigenic re-stimulation. Together these data highlight a significant role for AMPK in controlling oxidative and glycolytic metabolism in both murine and human T cells during GVHD and endorse further study of AMPK inhibition as a potential target for future clinical therapies.

KEY POINTS

AMPK plays a key role in driving both and oxidative and glycolytic metabolism in T cells during graft-versus-host disease (GVHD)Absence of AMPK simultaneously impairs both glycolytic enzyme activity, most notably by aldolase, and interferon gamma (IFNγ) production.

Allogeneic stem cell transplantation in the treatment of acute myeloid leukemia: An overview of obstacles and opportunities

As an important treatment for acute myeloid leukemia, allogeneic hematopoietic stem cell transplantation (allo-HSCT) plays an important role in reducing relapse and improving long-term survival. With rapid advancements in basic research in molecular biology and immunology and with deepening understanding of the biological characteristics of hematopoietic stem cells, allo-HSCT has been widely applied in clinical practice. During allo-HSCT, preconditioning, the donor, and the source of stem cells can be tailored to the patient’s conditions, greatly broadening the indications for HSCT, with clear survival benefits. However, the risks associated with allo-HSCT remain high, i.e. hematopoietic reconstitution failure, delayed immune reconstitution, graft-versus-host disease, and post-transplant relapse, which are bottlenecks for further improvements in allo-HSCT efficacy and have become hot topics in the field of HSCT. Other bottlenecks recognized in the current treatment of individuals diagnosed with acute myeloid leukemia and subjected to allo-HSCT include the selection of the most appropriate conditioning regimen and post-transplantation management. In this paper, we reviewed the progress of relevant research regarding these aspects.

The role of AMP-activated protein kinase in GVHD-causing T cells

Allogeneic stem cell transplantation is a curative therapy for multiple hematologic disorders. However, this life-saving procedure is often complicated by acute graft-versus-host disease (GVHD), where donor T cells attack tissues in the recipient's skin, liver, and gastrointestinal tract. Previous research has demonstrated that GVHD-causing T cells undergo significant metabolic reprogramming during disease pathogenesis, with an increased reliance on oxidative metabolism. This dependence makes metabolic modulation a potential approach to treat and/or prevent GVHD. Here, we provide an overview on the metabolic changes adopted by allogeneic T cells during disease initiation, highlighting the role played by AMP-activated protein kinase (AMPK) and identifying ways in which these insights might be leveraged to therapeutic advantage clinically.

Predicting the risk of acute kidney injury after hematopoietic stem cell transplantation: development of a new predictive nomogram

The purpose was to predict the risk of acute kidney injury (AKI) within 100 days after hematopoietic stem cell transplantation (HSCT) in patients with hematologic disease by using a new predictive nomogram. Collect clinical data of patients with hematologic disease undergoing HSCT in our hospital from August 2012 to March 2018. Parameters with non-zero coefficients were selected by the Least Absolute Selection Operator (LASSO). Then these parameters were selected to build a new predictive nomogram model. Receiver operating characteristic (ROC) curve, calibration curve, C-index, and decision curve analysis (DCA) were used for the validation of the evaluation model. Finally, the nomogram was further evaluated by internal verification. According to 2012 Kidney Disease Improving Global Guidelines (KDIGO) diagnostic criteria, among 144 patients, the occurrence of AKI within 100 days after HSCT The rate was 29.2% (42/144). The C-index of the nomogram was 0.842. The C-value calculated by the internal verification was 0.809. The AUC was 0.842, and The DCA range of the predicted nomogram was from 0.01 to 0.71. This article established a high-precision nomogram for the first time for predicting the risk of AKI within 100 days after HSCT in patients with hematologic diseases. The nomogram had good clinical validity and reliability. For clinicians, it was very important to prevent AKI after HSCT.

Effective Immunosurveillance After Allogeneic Hematopoietic Stem Cell Transplantation in Acute Myeloid Leukemia

The number of patients receiving allogeneic hematopoietic stem cell transplantation (alloHCT) has increased constantly over the last years due to advances in transplant technology development, supportive care, transplant safety, and donor availability. Currently, acute myeloid leukemia (AML) is the most frequent indication for alloHCT. However, disease relapse remains the main cause of therapy failure. Therefore, concepts of maintaining and, if necessary, reinforcing a strong graft-versus-leukemia (GvL) effect is crucial for the prognosis and long-term survival of the patients. Over the last decades, it has become evident that effective immunosurveillance after alloHCT is an entangled complex of donor-specific characteristics, leukemia-associated geno- and phenotypes, and acquired resistance mechanisms. Furthermore, adoption of effector cells such as natural killer (NK) cells, alloreactive and regulatory T-cells with their accompanying receptor repertoire, and cell–cell interactions driven by messenger molecules within the stem cell and the bone marrow niche have important impact. In this review of pre- and posttransplant elements and mechanisms of immunosurveillance, we highlight the most important mechanisms after alloHCT.

Predictors of hematologic malignancy relapse in patients with advanced chronic graft-versus-host disease

Malignancy relapse remains a major barrier to treatment success in patients after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Chronic graft-versus-host disease (cGVHD) markedly reduces hematologic malignancy relapse risk, but relapses still occur in these patients. Patients (n = 275) with moderate or severe cGVHD were enrolled on the National Cancer Institute (NCI) prospective cross-sectional natural history study (NCT00092235). Subjects were median 36 months after allo-HSCT and were followed subsequently for malignancy relapse and survival. Seventeen patients experienced relapse. In a multivariable model including time-dependent influences on relapse, risk factors associated with increased risk of relapse included shorter time from transplant to cGVHD evaluation (HR 0.279, 95% CI 0.078-0.995) and lower number of prior lines of systemic immunosuppressive therapy for cGVHD (HR 0.260, 95% CI 0.094-0.719). In a model excluding time-dependent influences on relapse risk, lower number of prior lines of systemic immunosuppressive therapy for cGVHD (HR 0.288, 95% CI 0.103-0.804), lower C4 complement level (HR 0.346, 95% CI 0.129-0.923), and higher body mass index (HR 3.222, 95% CI 1.156-8.974), were all associated with increased relapse risk. Parameters indicating cGVHD severity and activity are associated with risk of malignancy relapse. Classical predictors of relapse after allo-HSCT do not seem to be prognostic.

Glucose oxidase induces mobilization of long-term repopulating hematopoietic cells in mice

Hematopoietic stem progenitor cells (HSPCs) mobilized to peripheral blood, rather than those remaining in the bone marrow (BM), are commonly used as stem cell source in the clinic. As reactive oxygen species (ROS) are suggested as mediator of HSPC mobilization, we examined the impacts of glucose oxidase (GO) on peripheral mobilization of BM HSPCs and the associated mechanisms. Intravenous injection of GO induced HSPC mobilization even by single treatment, and the GO‐mobilized cells maintained their long‐term reconstituting and differentiating potentials in conditioned recipients. GO‐injected mice lived a normal life without adverse effects such as stem cell senescence, hematopoietic disorders, and blood parameter alteration. The mobilization effect of GO was even evident in animal models showing poor mobilization, such as old, 5‐fluorouracil‐treated, or alendronate‐treated mice. Importantly, combined injection of GO with granulocyte colony‐stimulating factor (G‐CSF) and/or AMD3100 enhanced more greatly HSPC mobilization than did G‐CSF, AMD3100, or both. The GO‐stimulated HSPC mobilization was almost completely attenuated by n‐acetyl‐L‐cysteine treatment. Collectively, our results not only highlight the potential role of GO in HSPC mobilization via ROS signaling, but also provide a GO‐based new strategy to improve HSPC mobilization in poorly mobilizing allogeneic or autologous donors via combination with G‐CSF and/or AMD3100.

Tolerogenic anti-IL-2 mAb prevents graft-versus-host disease while preserving strong graft-versus-leukemia activity

Donor T cells mediate both graft-versus-leukemia (GVL) activity and graft-versus-host disease (GVHD) after allogeneic hematopoietic cell transplantation (allo-HCT). Development of methods that preserve GVL activity while preventing GVHD remains a long-sought goal. Tolerogenic anti-interleukin-2 (IL-2) monoclonal antibody (JES6-1) forms anti-IL-2/IL-2 complexes that block IL-2 binding to IL-2Rβ and IL-2Rγ on conventional T cells that have low expression of IL-2Rα. Here, we show that administration of JES6 early after allo-HCT in mice markedly attenuates acute GVHD while preserving GVL activity that is dramatically stronger than observed with tacrolimus (TAC) treatment. The anti-IL-2 treatment downregulated activation of the IL-2-Stat5 pathway and reduced production of granulocyte-macrophage colony-stimulating factor (GM-CSF). In GVHD target tissues, enhanced T-cell programmed cell death protein 1 (PD-1) interaction with tissue-programmed cell death-ligand 1 (PD-L1) led to reduced activation of protein kinase-mammalian target of rapamycin pathway and increased expression of eomesodermin and B-lymphocyte-induced maturation protein-1, increased T-cell anergy/exhaustion, expansion of Foxp3-IL-10-producing type 1 regulatory (Tr1) cells, and depletion of GM-CSF-producing T helper type 1 (Th1)/cytotoxic T cell type 1 (Tc1) cells. In recipient lymphoid tissues, lack of donor T-cell PD-1 interaction with tissue PD-L1 preserved donor PD-1+TCF-1+Ly108+CD8+ T memory progenitors and functional effectors that have strong GVL activity. Anti-IL-2 and TAC treatments have qualitatively distinct effects on donor T cells in the lymphoid tissues, and CD8+ T memory progenitor cells are enriched with anti-IL-2 treatment compared with TAC treatment. We conclude that administration of tolerogenic anti-IL-2 monoclonal antibody early after allo-HCT represents a novel approach for preventing acute GVHD while preserving GVL activity.

Independent risk factors and long-term outcomes for acute kidney injury in pediatric patients undergoing hematopoietic stem cell transplantation: a retrospective cohort study

BACKGROUND

Acute kidney injury (AKI) remains a frequent complication in children undergoing hematopoietic stem cell transplantation (HSCT) and an independent risk factor of the patient's survival and a prognostic factor of progression to chronic kidney disease (CKD). However, the causes of these complications are diverse, usually overlapping, and less well understood.

METHODS

This retrospective analysis was performed in 43 patients (28 boys, 15 girls; median age, 5.5 years) undergoing HSCT between April 2006 and March 2019. The main outcome was the development of AKI defined according to the Pediatric Risk, Injury, Failure, Loss, End-stage Renal Disease (pRIFLE) criteria as ≥ 25% decrease in estimated creatinine clearance. The secondary outcome was the development of CKD after a 2-year follow-up.

RESULTS

AKI developed in 21 patients (49%) within 100 days after HSCT. After adjusting for possible confounders, posttransplant AKI was associated with matched unrelated donor (MUD) (HR, 6.26; P = 0.042), but not total body irradiation (TBI). Of 37 patients who were able to follow-up for 2 years, 7 patients died, but none had reached CKD during the 2 years after transplantation.

CONCLUSIONS

Posttransplant AKI was strongly associated with HSCT from MUD. Although the incidence of AKI was high in our cohort, that of posttransplant CKD was lower than reported previously in adults. TBI dose reduced, GVHD minimized, and infection prevented are required to avoid late renal dysfunction after HSCT in children since their combinations may contribute to the occurrence of AKI.

Targeting Histone Deacetylases to Modulate Graft-Versus-Host Disease and Graft-Versus-Leukemia

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is the main therapeutic strategy for patients with both malignant and nonmalignant disorders. The therapeutic benefits of allo-HSCT in malignant disorders are primarily derived from the graft-versus-leukemia (GvL) effect, in which T cells in the donor graft recognize and eradicate residual malignant cells. However, the same donor T cells can also recognize normal host tissues as foreign, leading to the development of graft-versus-host disease (GvHD), which is difficult to separate from GvL and is the most frequent and serious complication following allo-HSCT. Inhibition of donor T cell toxicity helps in reducing GvHD but also restricts GvL activity. Therefore, developing a novel therapeutic strategy that selectively suppresses GvHD without affecting GvL is essential. Recent studies have shown that inhibition of histone deacetylases (HDACs) not only inhibits the growth of tumor cells but also regulates the cytotoxic activity of T cells. Here, we compile the known therapeutic potential of HDAC inhibitors in preventing several stages of GvHD pathogenesis. Furthermore, we will also review the current clinical features of HDAC inhibitors in preventing and treating GvHD as well as maintaining GvL.

Regulation of the Immune Balance During Allogeneic Hematopoietic Stem Cell Transplantation by Vitamin D

One of the most promising therapeutic approaches for numerous hematological malignancies represents the allogeneic hematopoietic stem cell transplantation (allo-HSCT). One major complication is the development of the life-threatening graft-vs.-host disease (GvHD) which limits beneficial effects of graft-vs.-leukemia (GvL) responses during allo-HSCT. Strengthening GvL effects without induction of severe GvHD is essential to decrease the relapse rate after allo-HSCT. An interesting player in this context is vitamin D₃ since it has modulatory capacity in both preventing GvHD and boosting GvL responses. Current studies claim that vitamin D₃ induces an immunosuppressive environment by dendritic cell (DC)-dependent generation of regulatory T cells (Tregs). Since vitamin D₃ is known to support the antimicrobial defense by re-establishing the physical barrier as well as releasing defensins and antimicrobial peptides, it might also improve graft-vs.-infection (GvI) effects in patients. Beyond that, alloreactive T cells might be attenuated by vitamin D₃-mediated inhibition of proliferation and activation. Despite the inhibitory effects of vitamin D₃ on T cells, anti-tumor responses of GvL might be reinforced by vitamin D₃-triggered phagocytic activity and antibody-based immunotherapy. Therefore, vitamin D₃ treatment does not only lead to a shift from a pro-inflammatory toward a tolerogenic state but also promotes tumoricidal activity of immune cells. In this review we focus on vitamin D₃ and its immunomodulatory effects by enhancing anti-tumor activity while alleviating harmful allogeneic responses in order to restore the immune balance.

iNKT cells and hematopoietic stem cell transplantation: Two-phase activation of iNKT cells may improve outcome

Invariant natural killer T cells (iNKT) produce large amounts of different cytokines which can influence differentiation, polarization and activation of immune cells, particularly NK and T cells. iNKT have been shown to suppress GvHD and promote anti-tumor and anti-pathogen immunity. There are highly specific and safe synthetic ligands such as alpha-galactosylceramide (α-GalCer) and C20:2 which activate iNKT cells toward relatively Th1 and Th2 pathways, respectively. Bone marrow transplantation (BMT) or 'hematopoietic stem cell transplantation' (HSCT) is effective for leukemia and lymphoma through 'graft-versus-leukemia' (GVL) immunity. However, frequent serious complications include graft-versus-host-disease (GVHD), opportunistic infections and relapse. Both GVHD and GVL are mediated by T cells. Manipulating iNKT by different lipid analogues in early and late phases after transplantation may suppress GVHD and graft rejection and enhance GVL effect, as well as resistance to opportunistic infections and so, could be a novel and effective strategy for improving HSCT outcome.

Mixed vs full donor engraftment early after hematopoietic cell transplant: Impact on incidence and control of cytomegalovirus infection

Recovery of cytomegalovirus (CMV)-specific immunity after hematopoietic cell transplantation (HCT) is essential in controlling CMV infection. We hypothesize that mixed donor engraftment as measured by chimerism at day 30 in CMV D(+) HCTs and full chimerism in CMV D(-) HCTs will be predictive of CMV reactivation. Prospectively collected data for 407 CMV R+ HCT recipients transplanted from 2006 to 2014 at the University of Minnesota were retrospectively analyzed. Full and mixed donor engraftment were defined as ≥95% or <95% donor cells at day 30, respectively. Source of engraftment determination included preferentially peripheral blood CD3 fraction, then myeloid cell fraction (CD15+), then bone marrow. In 407 CMV R+ subjects, 77% (n = 313) were CMV D(-) cells from umbilical cord blood (n = 209), peripheral blood (n = 58) or marrow (n = 46). Fifty three per cent received reduced intensity conditioning (RIC). At day +30, full donor engraftment was seen in 82% of myeloablative and 55% of RIC transplants. The cumulative incidence of CMV infection 1-year after transplant was not different in patients with full (54%, n = 276) or mixed (53%, n = 131) donor engraftment. Control of CMV did not significantly differ among the two groups. In multiple regression analysis, there was no significant association between donor engraftment (mixed or full) and incidence or control of CMV.

Chimeric switch receptor: switching for improved adoptive T-cell therapy against cancers

Adoptive T-lymphocyte transfer-based immunotherapy for cancers has seen huge leaps with both CARs and engineered TCRs. Despite this, issues relating to safety and efficacy persist. To address this, chimeric switch receptors have been created to reverse the outcomes of their original signaling pathways in order to confer immune cells with the ability to overcome the immunosuppressive tumor microenvironment and to allow them to have greater in vivo persistence. Activating switch receptors exploit the inhibitory molecules expressed by cancer cells to further stimulate the tumor antigen-specific T lymphocytes. On the other hand, inhibitory switch receptors inhibit the effects of tumor-reactive T lymphocytes on unintended targets. This paper reviews the switch receptors reported thus far, and lists out potential improvements and future works.

Peripheral Blood Stem Cell Mobilization in Healthy Donors by Granulocyte Colony-Stimulating Factor Causes Preferential Mobilization of Lymphocyte Subsets

Background

Allogeneic hematopoietic stem cell transplantation is associated with a high risk of immune-mediated post-transplant complications. Graft depletion of immunocompetent cell subsets is regarded as a possible strategy to reduce this risk without reducing antileukemic immune reactivity.

Study design and methods

We investigated the effect of hematopoietic stem cell mobilization with granulocyte colony-stimulating factor (G-CSF) on peripheral blood and stem cell graft levels of various T, B, and NK cell subsets in healthy donors. The results from flow cytometric cell quantification were examined by bioinformatics analyses.

Results

The G-CSF-induced mobilization of lymphocytes was a non-random process with preferential mobilization of naïve CD4⁺ and CD8⁺ T cells together with T cell receptor αβ⁺ T cells, naïve T regulatory cells, type 1 T regulatory cells, mature and memory B cells, and cytokine-producing NK cells. Analysis of circulating lymphoid cell capacity to release various cytokines (IFNγ, IL10, TGFβ, IL4, IL9, IL17, and IL22) showed preferential mobilization of IL10 releasing CD4⁺ T cells and CD3^-19^- cells. During G-CSF treatment, the healthy donors formed two subsets with generally strong and weaker mobilization of immunocompetent cells, respectively; hence the donors differed in their G-CSF responsiveness with regard to mobilization of immunocompetent cells. The different responsiveness was not reflected in the graft levels of various immunocompetent cell subsets. Furthermore, differences in donor G-CSF responsiveness were associated with time until platelet engraftment. Finally, strong G-CSF-induced mobilization of various T cell subsets seemed to increase the risk of recipient acute graft versus host disease, and this was independent of the graft T cell levels.

Conclusion

Healthy donors differ in their G-CSF responsiveness and preferential mobilization of immunocompetent cells. This difference seems to influence post-transplant recipient outcomes.

HLA-DPB1 mismatch induces a graft-versus-leukemia effect without severe acute GVHD after single-unit umbilical cord blood transplantation

Although it is known that human leukocyte antigen (HLA)-DPB1 disparity has a strong impact on outcomes in unrelated hematopoietic transplantation with induction of acute graft-versus-host disease (GVHD) and a graft-versus-leukemia (GVL) effect, its role in unrelated umbilical cord blood transplantation (UR-CBT) has yet to be fully clarified. Our current study is being conducted to elucidate the impact of HLA-DPB1 mismatch, along with the effect of other HLA loci mismatches at the allele level. HLA six loci alleles were retrospectively typed in 1157 Japanese donors and patients with leukemia or myelodysplastic syndrome who underwent transplantation with a single unit of cord blood. HLA-DPB1 mismatch was associated with a significant reduction in leukemia relapse (hazard ratio 0.61, P<0.001), whereas the other HLA loci allele-level mismatches did not. No significant effect of HLA-DPB1 mismatch was observed in the risk of acute GVHD, engraftment or mortality. This HLA-DPB1 GVL effect without induction of severe acute GVHD or deterioration of survival rate has not been reported in unrelated bone marrow or peripheral blood stem cell transplantations, suggesting apparent advantages of UR-CBT. Accordingly, selection of an HLA-DPB1 mismatch cord blood might be the preferable choice for single-unit UR-CBT.

Hematopoietic Stem Cell Transplantation for Childhood Acute Lymphoblastic Leukemia and the Role of MRD: A Single Centre Experience from India

Hematopoietic stem cell transplantation (HSCT) is an effective curative option for children with relapsed and high risk acute lymphoblastic leukemia (ALL). The effect of minimal residual disease (MRD) prior to transplantation has a significant impact on the overall outcome. We performed a retrospective analysis of children with ALL who underwent HSCT at our centre from 2002 to 2016. From 2002 to 2008 disease status was determined by morphology and karyotyping and from 2008 onwards by flow cytometry. A total of 46 children were transplanted for ALL at our centre. Of the 19 children who were MRD positive prior to HSCT 5 had a relapse after the transplant. Among the remaining 26 MRD negative children, only one child relapsed post HSCT. The EFS was 66.6% in the MRD negative group and 63.1% in positive group with no significant survival advantage of the first group over the second, (p 0.37). GVHD was the major cause of mortality overall at 56.7% as well as in the MRD negative group at 77.7%(7/9). On the other hand, relapse was the major mortality factor at 71.4%(5/7) in the MRD positive group. Molecular remission prior to HSCT shows a trend towards lesser chance of relapse. We should strive to achieve MRD negative status prior to transplant to improve EFS. However, GVHD is also emerging as a crucial factor and its impact on survival outcome in children undergoing HSCT for ALL needs to be followed up.

Effects of magnesium isoglycyrrhizinate on AST, ALT, and serum levels of Th1 cytokines in patients with allo-HSCT

This study aimed to investigate the protective effects of magnesium isoglycyrrhizinate (MGL) on aspartate aminotransferase (AST), alanine aminotransferase (ALT), and serum levels of T helper 1 (Th1) cytokines in patients with allogeneic hematopoietic stem cell transplantation (allo-HSCT). The study included 42 patients prepared for allo-HSCT, who were divided equally into MGL and reduced glutathione groups. The ALT and AST levels were detected 1day before pretreatment and transplantation, and 7, 14, and 21days after transplantation. The total days and times of fever, treatment time of patients in the laminar flow room, white blood cell (WBC) count, platelet (PTL) implantation time, and success rate of transplantation were recorded. The serum levels of Th1/Th2 cytokines were detected. MGL had a significant protective effect on AST 1day before transplantation and 7, 14, and 21days after transplantation, while ALT had a statistical difference only 7days after transplantation. MGL could shorten the duration of fever during transplantation and advance the WBC and PTL implantation time. Significant differences in Th1-like cytokines (P<0.05) and higher levels of Th2-like cytokines but with no statistical significance (P>0.05) were found in the MGL group compared with the control group. MGL had significant protective effects on AST after transplantation. MGL could reduce the duration of fever during transplantation, help the reconstruction and recovery of WBCs and PTLs, and regulate Th1 cytokines, revealing its protective effects on hepatic transaminases and graft versus host disease in allo-HSCT patients.

Modulation of Immune Checkpoints and Graft-versus-Leukemia in Allogeneic Transplants by Antagonizing Vasoactive Intestinal Peptide Signaling

The goal of allogeneic bone marrow transplantation (allo-BMT) is elimination of leukemia cells through the graft-versus-leukemia (GvL) activity of donor cells, while limiting graft-versus-host disease (GvHD). Immune checkpoint pathways regulate GvL and GvHD activities, but blocking antibodies or genetic inactivation of these pathways can cause lethal GVHD. Vasoactive intestinal peptide (VIP) is an immunosuppressive neuropeptide that regulates coinhibitory pathways; its role in allo-BMT has not been studied. We found VIP transiently expressed in donor NK, NK-T, dendritic cells, and T cells after allo transplant, as well as host leukocytes. A peptide antagonist of VIP signaling (VIPhyb) increased T-cell proliferation in vitro and reduced IL10 expression in donor T cells. Treatment of allo-BMT recipients with VIPhyb, or transplanting donor grafts lacking VIP (VIP-KO), activated donor T-cells in lymphoid organs, reduced T-cell homing to GvHD target organs, and enhanced GvL without increasing GvHD in multiple allo-BMT models. Genetic or ex vivo depletion of donor NK cells or CD8⁺ T cells from allografts abrogated the VIPhyb-enhanced GvL activity. VIPhyb treatment led to downregulation of PD-1 and PD-L1 expression on donor immune cells, increased effector molecule expression, and expanded oligoclonal CD8⁺ T cells that protected secondary allo transplant recipients from leukemia. Blocking VIP signaling thus represents a novel pharmacologic approach to separate GvL from GvHD and enhance adaptive T-cell responses to leukemia-associated antigens in allo-BMT. Cancer Res; 76(23); 6802-15. ©2016 AACR.

Cellular Reprogramming Allows Generation of Autologous Hematopoietic Progenitors From AML Patients That Are Devoid of Patient-Specific Genomic Aberrations

Current treatments that use hematopoietic progenitor cell (HPC) transplantation in acute myeloid leukemia (AML) patients substantially reduce the risk of relapse, but are limited by the availability of immune compatible healthy HPCs. Although cellular reprogramming has the potential to provide a novel autologous source of HPCs for transplantation, the applicability of this technology toward the derivation of healthy autologous hematopoietic cells devoid of patient-specific leukemic aberrations from AML patients must first be evaluated. Here, we report the generation of human AML patient-specific hematopoietic progenitors that are capable of normal in vitro differentiation to myeloid lineages and are devoid of leukemia-associated aberration found in matched patient bone marrow. Skin fibroblasts were obtained from AML patients whose leukemic cells possessed a distinct, leukemia-associated aberration, and used to create AML patient-specific induced pluripotent stem cells (iPSCs). Through hematopoietic differentiation of AML patient iPSCs, coupled with cytogenetic interrogation, we reveal that AML patient-specific HPCs possess normal progenitor capacity and are devoid of leukemia-associated mutations. Importantly, in rare patient skin samples that give rise to mosaic fibroblast cultures that continue to carry leukemia-associated mutations; healthy hematopoietic progenitors can also be generated via reprogramming selection. Our findings provide the proof of principle that cellular reprogramming can be applied on a personalized basis to generate healthy HPCs from AML patients, and should further motivate advances toward creating transplantable hematopoietic stem cells for autologous AML therapy. Stem Cells2013;33:1839–1849

Deep-sequencing of the T-cell receptor repertoire in patients with haplo-cord and matched-donor transplants

Haplo-cord transplant has emerged as a feasible and reliable approach for haematopoietic stem cell transplant in patients who are unable to find matched-donor. This approach provides fast myeloid recovery, low incidence of graft vs host disease (GVHD) and favorable graft versus leukemia (GVL) effects. T cell recovery plays an important role in preventing infectious complications; it also mediates the GVHD and the GVL effects. Here, we utilized a novel RNA-based sequencing approach to quantitatively characterize the T cell receptor (TCRs) repertoire in patients underwent haplo-cord transplant in comparison with those underwent matched-donor transplant. Our study shows that higher percentage of cord cells early post transplant were associated with significantly higher TCR diversity. TCR diversity was significantly lower in patients with GVHD and in relapsed patients. A larger cohort study is needed to validate these data and to provide useful information on the specific TCR clones correlated with clinical outcome.

Inhibitory effects of merocyanine 540-mediated photodynamic therapy on cellular immune functions: A role in the prophylaxis of graft-versus-host disease?

Merocyanine 540-mediated photodynamic therapy (MC540-PDT) has been used in clinical trials for the purging of autologous hematopoietic stem cell grafts. When the same combinations of dye and light were applied to human peripheral blood lymphocytes, a broad range of T- and B-cell functions were impaired, prompting speculations about a potential role of MC540-PDT in the prophylaxis of graft-versus-host disease (GVHD). We here report on the effects of MC540-PDT on in vitro functions of murine lymphocytes as well as a preliminary evaluation of MC540-PDT for the prevention of GVHD in murine models of allogeneic bone marrow transplantation. Mixed lymphocyte reactions, proliferative responses to lectins, interleukin-2 and lipopolysaccharide, T-cell-mediated lysis, and NK activity were all inhibited by moderate doses of MC540-PDT. Whether MC540-PDT reduced the incidence and/or the severity of GVHD in murine models of allogeneic hematopoietic stem cell transplantation depended on the composition of the mismatched grafts and the intensity of the preparative regimen. MC540-PDT was only beneficial (i.e. reduced the incidence and/or severity of GVHD) when the spleen cell content of grafts was low and/or the radiation dose of the preparative regimen was not myeloablative, and, therefore, may have encouraged mixed chimerism.

Single-Agent Post-Transplantation Cyclophosphamide as Graft-versus-Host Disease Prophylaxis after Human Leukocyte Antigen-Matched Related Bone Marrow Transplantation for Pediatric and Young Adult Patients with Hematologic Malignancies

High-dose cyclophosphamide given after HLA-matched related and unrelated allogeneic bone marrow transplantation (BMT) for patients with hematologic malignancies is effective single-agent graft-versus-host disease (GVHD) prophylaxis in adults. Data describing outcomes for pediatric and young adult patients have not been reported. Between the years 2007 and 2013, 29 pediatric and young adult patients ages ≤21 years of age treated at our institution for high-risk hematologic malignancies underwent myeloablative HLA-matched related T cell-replete BMT. Eleven patients received post-transplantation cyclophosphamide (PTCy) as single-agent GVHD prophylaxis and were followed prospectively. Eighteen patients received calcineurin inhibitor (CNI)-based standard GVHD prophylaxis and were studied retrospectively as a control group. No acute GVHD (aGVHD) developed in patients receiving PTCy, whereas patients receiving CNI-based GVHD prophylaxis had cumulative incidences of grades II to IV and grades III and IV aGVHD of 27% and 5%, respectively. No patients receiving PTCy developed chronic GHVD, compared to 1 in the control group. Two-year overall survival was similar between the 2 groups (54% PTCy versus 58% CNI-based prophylaxis), as was event-free survival (42% PTCy versus 47% CNI-based). The 5-year cumulative incidence of relapse was 58% for PTCy and 42% for CNI-based GVHD prophylaxis (P = .45). These results suggest that PTCy is a safe and efficacious method of GVHD prophylaxis after an HLA-matched related BMT in the pediatric and young adult population that affords patients to be off all post-transplantation immunosuppression on day +5.

T-cell subsets in autologous and allogeneic peripheral blood stem cell concentrates

BACKGROUND AND OBJECTIVES

Regulatory T cells (Tregs) and other T-cell subsets are of importance in the setting of autologous and allogeneic stem cell transplantations. We conducted a study to assess the content of peripheral blood stem cell concentrates and related apheresis parameters in the autologous and allogeneic setting.

MATERIAL AND METHODS

We characterized 53 donors, patients and peripheral blood stem cell concentrates (PBSC) regarding the content of CD45(+) cells, lymphocytes, CD3(+) cells, CD3(+) CD4(+) T cells, CD3(+) CD4(+) CD25(+) T cells, CD3(+) CD4(+) CD25(+) CD127(low/negative) Tregs and CD34(+) cells and calculated cell yields, recruitment factors and collection efficiency for all cell types. We compared allogeneic data with autologous data.

RESULTS

Autologous PBSC show significantly lower concentrations of T-cell subsets compared to allogeneic PBSC (17,112/μl CD4(+), 14,858/μl CD4(+) CD25(+) and 1579/μl CD3(+) CD4(+) CD25(+) CD127(low/negative) Tregs in autologous compared to 65,539/μl CD4(+), 44,208(+) /μl CD4(+) CD25(+) and 5040/μl CD3(+) CD4(+) CD25(+) CD127(low/negative) Tregs in allogeneic PBSC, respectively), in contrast to CD34(+) concentrations (5342/μl CD34(+) in autologous compared to 2367/μl CD34(+) in allogeneic PBSC, respectively). Accordantly, all T-cell yields are lower in the autologous setting compared to allogeneic PBSC. However, recruitment factor and collection efficiency of all cell types are higher in autologous compared to allogeneic PBSC, but not all parameters differ significantly when groups are compared.

CONCLUSION

T-cell subsets and especially Tregs are a substantial part of PBSC transplantation, as considerable recruitment during apheresis occurs. In large volume apheresis, the collection efficiency of Treg is comparable to that of CD34(+) cells, while recruitment factors are even higher.

Myxoma virus suppresses proliferation of activated T lymphocytes yet permits oncolytic virus transfer to cancer cells

Allogeneic hematopoietic cell transplant (allo-HCT) can be curative for certain hematologic malignancies, but the risk of graft-versus-host disease (GVHD) is a major limitation for wider application. Ideally, strategies to improve allo-HCT would involve suppression of T lymphocytes that drive GVHD while sparing those that mediate graft-versus-malignancy (GVM). Recently, using a xenograft model, we serendipitously discovered that myxoma virus (MYXV) prevented GVHD while permitting GVM. In this study, we show that MYXV binds to resting, primary human T lymphocytes but will only proceed into active virus infection after the T cells receive activation signals. MYXV-infected T lymphocytes exhibited impaired proliferation after activation with reduced expression of interferon-γ, interleukin-2 (IL-2), and soluble IL-2Rα, but did not affect expression of IL-4 and IL-10. MYXV suppressed T-cell proliferation in 2 patterns (full vs partial) depending on the donor. In terms of GVM, we show that MYXV-infected activated human T lymphocytes effectively deliver live oncolytic virus to human multiple myeloma cells, thus augmenting GVM by transfer of active oncolytic virus to residual cancer cells. Given this dual capacity of reducing GVHD plus increasing the antineoplastic effectiveness of GVM, ex vivo virotherapy with MYXV may be a promising clinical adjunct to allo-HCT regimens.

CCR7 guides migration of mesenchymal stem cell to secondary lymphoid organs: a novel approach to separate GvHD from GvL effect

Inefficient homing of systemically infused mesenchymal stem cells (MSCs) limits the efficacy of existing MSC-based clinical graft-versus-host disease (GvHD) therapies. Secondary lymphoid organs (SLOs) are the major niches for generating immune responses or tolerance. MSCs home to a wide range of organs, but rarely to SLOs after intravenous infusion. Thus, we hypothesized that targeted migration of MSCs into SLOs may significantly improve their immunomodulatory effect. Here, chemokine receptor 7 (CCR7) gene, encoding a receptor that specifically guides migration of immune cells into SLOs, was engineered into a murine MSC line C3H10T1/2 by retrovirus transfection system (MSCs/CCR7). We found that infusion of MSCs/CCR7 potently prolonged the survival of GvHD mouse model. The infused MSCs/CCR7 migrate to SLOs, relocate in proximity with T lymphocytes, therefore, potently inhibited their proliferation, activation, and cytotoxicity. Natural killer (NK) cells contribute to the early control of leukemia relapse. Although MSCs/CCR7 inhibited NK cell activity in vitro coculture, they did not impact on the proportion and cytotoxic capacities of NK cells in the peripheral blood of GvHD mice. In an EL4 leukemia cell loaded GvHD model, MSCs/CCR7 infusion preserved the graft-versus-leukemia (GvL) effect. In conclusion, this study demonstrates that CCR7 guides migration of MSCs to SLOs and thus highly intensify their in vivo immunomodulatory effect while preserving the GvL activity. This exciting therapeutic strategy may improve the clinical efficacy of MSC based therapy for immune diseases.

Suppression of graft-versus-host disease and retention of graft-versus-tumour reaction by murine genetically engineered dendritic cells following bone marrow transplantation

The effect of infusion of lentiviral vector‑mediated, genetically engineered dendritic cells (DCs) following allogeneic bone marrow transplantation (allo‑BMT) on graft‑versus‑host disease (GVHD) and graft‑versus‑leukemia (GVL) was investigated in a mouse model. Lentivirus‑mediated expression of soluble tumor necrosis factor receptor 1 (sTNFR1) converted immature DCs (imDCs) from BABL/c mice into engineered DCs in vitro. An EL4 leukemia allo‑BMT model of BABL/c to C57BL/6 mice was established. Engineered DCs with donor bone marrow cells and splenocytes were subsequently transplanted into myeloablatively irradiated recipients. The average survival duration in the sTNFR1‑ and pXZ9‑imDC groups was significantly prolonged compared with that of the allo‑BMT group (P<0.05). Mild histological changes in GVHD or leukemia were observed in the recipients in the sTNFR1‑imDC group and clinical GVHD scores in this group were significantly decreased compared with those of the transplantation and pXZ9‑imDC groups. Serum interferon‑γ levels were decreased in the pXZ9‑imDC and sTNFR1‑imDC groups compared with those in the allo‑BMT group (P<0.05), with the reduction being more significant in the sTNFR1‑imDC group (P<0.05). Serum interleukin‑4 expression levels were decreased in the allo‑BMT group, but gradually increased in the pXZ9‑imDC and sTNFR1‑imDC groups (P<0.05). Co‑injection of donor genetically‑engineered imDCs was able to efficiently protect recipient mice from lethal GVHD while preserving GVL effects during allo‑BMT.

Urinary elafin and kidney injury in hematopoietic cell transplant recipients

BACKGROUND AND OBJECTIVES

Graft-versus-host disease (GVHD) is associated with kidney injury after hematopoietic cell transplantation (HCT). Because plasma elafin levels correlate with skin GVHD, this study examined urinary elafin as a potential marker of renal inflammation and injury.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Urine was collected prospectively on 205 patients undergoing their first HCT from 2003 to 2010. Collections were done at baseline, weekly through day 100, and monthly through year 1 to measure elafin and urine albumin-to-creatinine ratio (ACR). Associations between urinary elafin levels and microalbuminuria, macroalbuminuria, AKI and CKD, and mortality were examined using Cox proportional hazards or linear regression models. Available kidney biopsy specimens were processed for immunohistochemistry.

RESULTS

Mean urinary elafin levels to day 100 were higher in patients with micro- or macroalbuminuria (adjusted mean difference, 529 pg/ml; P=0.03) at day 100 than in those with a normal ACR (adjusted mean difference, 1295 pg/ml; P<0.001). Mean urinary elafin levels were higher in patients with AKI compared with patients without AKI (adjusted mean difference, 558 pg/ml; P<0.01). The average urinary elafin levels within the first 100 days after HCT were higher in patients who developed CKD at 1 year than in patients without CKD (adjusted mean difference, 894 pg/ml; P=0.002). Among allogeneic recipients, a higher proportion of patients with micro- or macroalbuminuria at day 100 also had grade II-IV acute GVHD (80% and 86%, respectively) compared with patients with a normal ACR (58%; global P<0.01). Each increase in elafin of 500 pg/ml resulted in a 10% increase in risk of persistent macroalbuminuria (hazard ratio, 1.10; 95% confidence interval [95% CI], 1.06 to 1.13; P<0.001) and a 7% increase in the risk of overall mortality (95% CI, 1.02 to 1.13, P<0.01). Renal biopsy specimens from a separate cohort of HCT survivors demonstrated elafin staining in distal and collecting duct tubules.

CONCLUSION

Higher urinary elafin levels are associated with an increased risk of micro- and macroalbuminuria, AKI and CKD, and death after HCT.

A multicentre UK study of GVHD following DLI: rates of GVHD are high but mortality from GVHD is infrequent

DLIs are frequently used following haematopoietic SCT (HSCT) in patients with risk of relapse but data on GVHD following DLI are scarce. We report on 68 patients who received DLI following HSCT. Most patients developed GVHD following DLI (71%), which was acute in 22 patients (32%) almost half of whom had grade III-IV acute GVHD (aGVHD). Thirty patients (44%) developed cGVHD which followed aGVHD in four patients and was graded severe in nine patients. Corticosteroids were the most common first-line therapy for both acute and chronic GVHD. A wide range of second/third-line agents included cyclosporin, mycophenolate, tacrolimus, imatinib, infliximab and ECP. Relapse of initial malignancy occurred in 37%. Relapse was significantly less frequent in those receiving pre-emptive DLI. Relapse rates were also lower in those with GVHD (31%) than those without GVHD (50%), but this did not reach statistical significance. At 55 months post DLI, 34% of patients had died most commonly from relapse and 22% had on-going GVHD. Although GVHD was an important cause of morbidity post DLI (71%), only 6% died from GVHD. Although most patients develop GVHD post DLI and may require consecutive therapies, mortality from GVHD is infrequent. DLI remains an important option for relapse post transplant and manipulation of the GVT effect needs to be optimised to induce remission without morbidity from GVHD.

Selective expansion of human natural killer cells leads to enhanced alloreactivity

In allogeneic stem cell transplantation (SCT), natural killer (NK) cells lacking their cognate inhibitory ligand can induce graft-versus-leukemia responses, without the induction of severe graft-versus-host disease (GVHD). This feature can be exploited for cellular immunotherapy. In this study, we examined selective expansion of NK cell subsets expressing distinct killer immunoglobulin-like receptors (KIRs) within the whole human peripheral blood NK cell population, in the presence of HLA-Cw3 (C1) or Cw4 (C2) transfected K562 stimulator cells. Coculture of KIR(+) NK cells with C1 or C2 positive K562 cells, in the presence of IL-2+IL-15, triggered the outgrowth of NK cells that missed their cognate ligand. This resulted in an increased frequency of alloreactive KIR(+) NK cells within the whole NK cell population. Also, after preculture with K562 cells lacking their cognate ligand, we observed that this alloreactive NK population revealed higher numbers of CD107(+) cells when cocultured with the relevant K562 HLA-C transfected target cells, as compared to coculture with untransfected K562 cells. This enhanced reactivity was confirmed using primary leukemic cells as target. This study demonstrates that HLA class I expression can mediate the skewing of the NK cell repertoire and enrich the population for cells with enhanced alloreactivity towards leukemic target cells. This feature may support future clinical applications of NK cell-based immunotherapy.

Recipient leukocyte infusion enhances the local and systemic graft-versus-neuroblastoma effect of allogeneic bone marrow transplantation in mice

Allogeneic hematopoietic stem cell transplantation and donor leukocyte infusion (DLI) may hold potential as a novel form of immunotherapy for high-risk neuroblastoma. DLI, however, carries the risk of graft-versus-host disease (GvHD). Recipient leukocyte infusion (RLI) induces graft-versus-leukemia responses without GvHD in mice and is currently being explored clinically. Here, we demonstrate that both DLI and RLI, when given to mixed C57BL/6→A/J radiation chimeras carrying subcutaneous Neuro2A neuroblastoma implants, can slow the local growth of such tumors. DLI provoked full donor chimerism and GvHD; RLI produced graft rejection but left mice healthy. Flow cytometric studies showed that the chimerism of intratumoral leukocytes paralleled the systemic chimerism. This was associated with increased CD8/CD4 ratios, CD8+ T-cell IFN-γ expression and NK-cell Granzyme B expression within the tumor, following both DLI and RLI. The clinically safe anti-tumor effect of RLI was further enhanced by adoptively transferred naïve recipient-type NK cells. In models of intravenous Neuro2A tumor challenge, allogeneic chimeras showed superior overall survival over syngeneic chimeras. Bioluminescence imaging in allogeneic chimeras challenged with luciferase-transduced Neuro2A cells showed both DLI and RLI to prolong metastasis-free survival. This is the first experimental evidence that RLI can safely produce a local and systemic anti-tumor effect against a solid tumor. Our data indicate that RLI may provide combined T-cell and NK-cell reactivity effectively targeting Neuro2A neuroblastoma.

The nucleotide sugar UDP-glucose mobilizes long-term repopulating primitive hematopoietic cells

Hematopoietic stem progenitor cells (HSPCs) are present in very small numbers in the circulating blood in steady-state conditions. In response to stress or injury, HSPCs are primed to migrate out of their niche to peripheral blood. Mobilized HSPCs are now commonly used as stem cell sources due to faster engraftment and reduced risk of posttransplant infection. In this study, we demonstrated that a nucleotide sugar, UDP-glucose, which is released into extracellular fluids in response to stress, mediates HSPC mobilization. UDP-glucose-mobilized cells possessed the capacity to achieve long-term repopulation in lethally irradiated animals and the ability to differentiate into multi-lineage blood cells. Compared with G-CSF-mobilized cells, UDP-glucose-mobilized cells preferentially supported long-term repopulation and exhibited lymphoid-biased differentiation, suggesting that UDP-glucose triggers the mobilization of functionally distinct subsets of HSPCs. Furthermore, co-administration of UDP-glucose and G-CSF led to greater HSPC mobilization than G-CSF alone. Administration of the antioxidant agent NAC significantly reduced UDP-glucose-induced mobilization, coinciding with a reduction in RANKL and osteoclastogenesis. These findings provide direct evidence demonstrating a potential role for UDP-glucose in HSPC mobilization and may provide an attractive strategy to improve the yield of stem cells in poor-mobilizing allogeneic or autologous donors.

Lithothamnion muelleri controls inflammatory responses, target organ injury and lethality associated with graft-versus-host disease in mice

Lithothamnion muelleri (Hapalidiaceae) is a marine red alga, which is a member of a group of algae with anti-inflammatory, antitumor, and immunomodulatory properties. The present study evaluated the effects of treatment with Lithothamnion muelleri extract (LM) in a model of acute graft-versus-host disease (GVHD), using a model of adoptive splenocyte transfer from C57BL/6 donors into B6D2F1 recipient mice. Mice treated with LM showed reduced clinical signs of disease and mortality when compared with untreated mice. LM-treated mice had reduced tissue injury, less bacterial translocation, and decreased levels of proinflammatory cytokines and chemokines (interferon-γ (IFN-γ), tumor necrosis factor-α (TNF-α), chemokine (C-C motif) ligand 2 (CCL2), chemokine (C-C motif) ligand 3 (CCL3) and chemokine (C-C motif) ligand 5 (CCL5)). The polysaccharide-rich fraction derived from LM could inhibit leukocyte rolling and adhesion in intestinal venules, as assessed by intravital microscopy. LM treatment did not impair the beneficial effects of graft-versus-leukaemia (GVL). Altogether, our studies suggest that treatment with Lithothamnion muelleri has a potential therapeutic application in GVHD treatment.

Association between IL1B (+3954) polymorphisms and IL-1β levels in blood and saliva, together with acute graft-versus-host disease

Graft-versus-host disease (GVHD) is associated with morbidity and mortality in the recipients of allogeneic hematopoietic stem cell transplants (allo-HSCTs). Interleukin-1β (IL-1β) is a potent inflammatory mediator involved in different inflammatory conditions. Therefore, we aimed to investigate the association of IL1B gene polymorphism in recipients and donors in cases in which acute GVHD (aGVHD) has been reported and the impact of this gene polymorphism on the level of cytokines in the blood and saliva. Fifty-eight consecutive allo-HSCT recipients and their donors were prospectively studied. Saliva and/or blood samples were obtained from the recipients and donors to identify the IL1B gene polymorphism, and cytokine levels were assessed by ELISA. Samples were collected weekly from 7 days before transplantation (day -7) to 100 days after allo-HSCT (day+100), for a total of 16 weeks or until death. aGVHD occurred in 27 individuals evaluated. A significant association was identified between the IL1B polymorphism in the donor and aGVHD development in the corresponding recipients. However, no significant association was detected between the IL1B polymorphism in recipients and the development of aGVHD. In the recipients who were diagnosed with aGVHD, the level of IL-1β in the saliva and blood were increased. In the saliva, IL-1β levels increased progressively from the time before the diagnosis of aGVHD until weeks after the diagnosis, whereas in the blood, IL-1β peak levels could be observed within the time allotted for diagnosis, followed by a decrease in the levels. In addition, we observed a significant association between the IL1B genotype of the recipient (CC) and high IL-1β levels in the saliva at week 13. In conclusion, IL-1β could be considered a useful predictor of aGVHD development.

Pharmacological inhibition of VIP signaling enhances antiviral immunity and improves survival in murine cytomegalovirus-infected allogeneic bone marrow transplant recipients

Cytomegalovirus (CMV) infection following allogeneic bone marrow transplant (allo-BMT) is controlled by donor-derived cellular immunity. Vasoactive intestinal peptide (VIP) suppresses Th1 immunity. We hypothesized that blocking VIP-signaling would enhance anti-CMV immunity in murine recipients of allo-BMT. Recipients were transplanted with bone marrow (BM) and T-cells from major histocompatibility complex (MHC)-mismatched VIP-knockout (KO) or wild-type donors, and treated with 7 daily subcutaneous injections of VIPhyb (peptidic VIP-antagonist) or phosphate-buffered saline (PBS). Genetic and pharmacological blockade of VIP-signaling protected allo-BMT recipients from lethal murine CMV (mCMV) infection, improving survival without increasing graft-versus-host disease. Mice treated with VIPhyb or transplanted with VIP-KO allografts had significantly lower viral loads, increased numbers of mCMV-M45-peptide-MHC-tetramer(+) CD8(+) T-cells, with lower PD-1 expression, and enhanced primary and secondary cellular immune responses after mCMV infection than did PBS-treated mice. These results demonstrate that administration of a VIP antagonist after allo-BMT is a promising safely therapeutic approach to enhance antiviral cellular immunity.

Stem cell transplant as an immunomodulatory tool for children with hematologic malignancies

Allogeneic stem cell transplantation (alloHSCT) is the most common and effective form of immunotherapy used for treatment of pediatric leukemias. A combination of graft manipulation, donor selection, fine-tuning of conditioning regimens, and use of lower and novel forms of immunosuppression following transplant has maximized the tolerability of alloHSCT in children. This outcome has facilitated new advances in disease-specific transplant regimens that seek to amplify the antitumor effects of the allograft, while reducing transplant-related mortality. However, disease relapse remains the preeminent challenge to the success of transplantation as a modality for successful treatment of high-risk disease. Separating graft versus host disease (GVHD) from graft versus leukemia (GVL) remains the most significant obstacle to enhancing disease-free survival. However, with increased clarity and discrimination in the effector mechanisms responsible for GVHD and/or GVL in patients of all ages, a new wave of clinical trials has become feasible that harnesses GVL effects to treat patients with high-risk myeloid and lymphoid malignancies. Exciting progress is being made in the use of alloHSCT with donor lymphocyte infusions (DLIs) in almost all forms of pediatric hematologic malignancies. This advance sets the stage for the use of HSCT and/or DLI in conjunction with novel disease-specific post-transplant therapies using small molecule therapeutics, tumor vaccines, and novel antibody therapies.

Mesenchymal stem cells as cellular immunotherapeutics in allogeneic hematopoietic stem cell transplantation

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a curative treatment option in hematopoietic disorders, immunodeficiencies and leukemia. To date graft-versus-host disease (GvHD) represents a life-threatening complication even if associated with beneficial antileukemic reactivity. GvHD is the clinical manifestation of donor cells reacting against host tissue. Because of their ability to facilitate endogenous repair and to attenuate inflammation, MSC have evolved as a highly attractive cellular therapeutic in allo-HSCT. Here we report on the clinical experience in the use of MSC to enhance engraftment and prevent and treat acute and chronic GvHD. In early clinical trials, MSC have shown considerable benefit in the setting of manifest GvHD. These encouraging results warrant further exploration.

Virotherapy using myxoma virus prevents lethal graft-versus-host disease following xeno-transplantation with primary human hematopoietic stem cells

Graft-versus-host disease (GVHD) is a potentially lethal clinical complication arising from the transfer of alloreactive T lymphocytes into immunocompromised recipients. Despite conventional methods of T cell depletion, GVHD remains a major challenge in allogeneic hematopoietic cell transplant. Here, we demonstrate a novel method of preventing GVHD by ex vivo treatment of primary human hematopoietic cell sources with myxoma virus, a rabbit specific poxvirus currently under development for oncolytic virotherapy. This pretreatment dramatically increases post-transplant survival of immunocompromised mice injected with primary human bone marrow or peripheral blood cells and prevents the expansion of human CD3(+) lymphocytes in major recipient organs. Similar viral treatment also prevents human-human mixed alloreactive T lymphocyte reactions in vitro. Our data suggest that ex vivo virotherapy with myxoma virus can be a simple and effective method for preventing GVHD following infusion of hematopoietic products containing alloreactive T lymphocytes such as: allogeneic hematopoietic stem and progenitor cells, donor leukocyte infusions and blood transfusions.

Eosinophilia, regardless of degree, is related to better outcomes after allogeneic hematopoietic stem cell transplantation

OBJECTIVE

Several recent studies report that, after allogeneic hematopoietic cell transplantation (allo-HCT), eosinophilia is a favorable factor for transplant outcomes. However, whether the degree of eosinophilia influences transplant outcomes is yet to be established.

METHODS

We studied 144 patients with hematological malignancy who received allo-HCT at our institution. The stem cell sources were bone marrow in 84 patients, peripheral blood stem cells in 32 patients, and cord blood in 28 patients. One hundred and twelve patients underwent myeloablative conditioning and 49 patients had high-risk disease. We performed semi-landmark analysis to examine the influence of eosinophilia.

RESULTS

Eosinophilia developed at a median of 47 days after transplantation in 63 patients (44%). The patients with eosinophilia showed significantly better overall survival (OS) and a lower relapse rate at three years, compared to those without eosinophilia (66% vs 55%, p=0.04 and 30% vs 50%, p=0.002). On analysis following division into groups with mild (500-1,500×10(6)/L) and hyper- (>1,500×10(6)/L) eosinophilia, three-year OS and relapse rates were 68% and 65% (p=0.92), and 31% and 28% (p=0.90), respectively. On multivariate analysis, eosinophilia was significantly associated with lower relapse rates [HR: 0.5 (95% CI: 0.3-0.9), p=0.01] and the same trend was preserved in the analysis of the mild and hyper-eosinophilic groups.

CONCLUSION

The results suggest that eosinophilia after allo-HCT was associated with better OS and a lower relapse rate, regardless of the levels. The mechanism of this effect is still unclear, and requires study of the pathophysiological process to clarify the relationship between the higher levels of eosinophilia after allo-HCT and organ infiltration.

Future perspectives: should Th17 cells be considered as a possible therapeutic target in acute myeloid leukemia patients receiving allogeneic stem cell transplantation?

Th17 cells seem to promote proinflammatory effects, and their development seems to depend on intracellular signaling initiated by IL1β, supported by IL6 and IL23 and mediated by STAT3 and RORC2. Even though primary human AML cells may affect Th17 development through their constitutive cytokine release, the levels of circulating Th17 cells in older patients with untreated AML do not differ from healthy controls and show only minor variations during and following conventional intensive chemotherapy. IL17-A is the signature cytokine of Th17 cells, but in vitro studies have failed to demonstrate a direct antileukemic effect of IL17 on primary human AML cells for most patient samples. However, several observations suggest that Th17 cells mediate antileukemic effects through other mechanisms and are important in allogeneic stem cell transplantation. Firstly, genetic variants in IL23/Th17 pathway have a prognostic impact with regard to both development of GVHD and posttransplant infections. Secondly, circulating IL17-secreting cells are detected during early posttransplant pancytopenia, and their ability to release IL17 is associated with later GVHD. Thirdly, a high number of Th17 cells in allogeneic stem cell grafts are associated with later acute GVHD, levels of circulating Th17 cells are increased at the onset of acute GVHD, and these levels normalize during treatment. In the present article, we review previous studies of Th17 cells in AML and in the development of GVHD, possible therapeutic strategies and available therapeutic tools for targeting of Th17 cells.

Flagellin, a TLR5 agonist, reduces graft-versus-host disease in allogeneic hematopoietic stem cell transplantation recipients while enhancing antiviral immunity

Graft-versus-host disease (GVHD) is a major cause of morbidity and mortality in patients treated with allogeneic hematopoietic stem cell transplantation (HSCT). Posttransplant immunosuppressive drugs incompletely control GVHD and increase susceptibility to opportunistic infections. In this study, we used flagellin, a TLR5 agonist protein (∼50 kDa) extracted from bacterial flagella, as a novel experimental treatment strategy to reduce both acute and chronic GVHD in allogeneic HSCT recipients. On the basis of the radioprotective effects of flagellin, we hypothesized that flagellin could ameliorate GVHD in lethally irradiated murine models of allogeneic HSCT. Two doses of highly purified flagellin (administered 3 h before irradiation and 24 h after HSCT) reduced GVHD and led to better survival in both H-2(b) → CB6F1 and H-2(K) → B6 allogeneic HSCT models while preserving >99% donor T cell chimerism. Flagellin treatment preserved long-term posttransplant immune reconstitution characterized by more donor thymic-derived CD4(+)CD25(+)Foxp3(+) regulatory T cells and significantly enhanced antiviral immunity after murine CMV infection. The proliferation index and activation status of donor spleen-derived T cells and serum concentration of proinflammatory cytokines in flagellin-treated recipients were reduced significantly within 4 d posttransplant compared with those of the PBS-treated control recipients. Allogeneic transplantation of radiation chimeras previously engrafted with TLR5 knockout hematopoietic cells showed that interactions between flagellin and TLR5 expressed on both donor hematopoietic and host nonhematopoietic cells were required to reduce GVHD. Thus, the peritransplant administration of flagellin is a novel therapeutic approach to control GVHD while preserving posttransplant donor immunity.

Absence of vasoactive intestinal peptide expression in hematopoietic cells enhances Th1 polarization and antiviral immunity in mice

Vasoactive intestinal peptide (VIP) induces regulatory dendritic cells (DC) in vitro that inhibit cellular immune responses. We tested the role of physiological levels of VIP on immune responses to murine CMV (mCMV) using VIP-knockout (VIP-KO) mice and radiation chimeras engrafted with syngenic VIP-KO hematopoietic cells. VIP-KO mice had less weight loss and better survival following mCMV infection compared with wild-type (WT) littermates. mCMV-infected VIP-KO mice had lower viral loads, faster clearance of virus, with increased numbers of IFN-γ(+) NK and NKT cells, and enhanced cytolytic activity of NK cells. Adaptive antiviral cellular immunity was increased in mCMV-infected VIP-KO mice compared with WT mice, with more Th1/Tc1-polarized T cells, fewer IL-10(+) T cells, and more mCMV-M45 epitope peptide MHC class I tetramer(+) CD8(+) T cells (tetramer(+) CD8 T cells). mCMV-immune VIP-KO mice had enhanced ability to clear mCMV peptide-pulsed target cells in vivo. Enhanced antiviral immunity was also seen in WT transplant recipients engrafted with VIP-KO hematopoietic cells, indicating that VIP synthesized by neuronal cells did not suppress immune responses. Following mCMV infection there was a marked upregulation of MHC-II and CD80 costimulatory molecule expression on DC from VIP-KO mice compared with DC from WT mice, whereas programmed death-1 and programmed death ligand-1 expression were upregulated in activated CD8(+) T cells and DC, respectively, in WT mice, but not in VIP-KO mice. Because the absence of VIP in immune cells increased innate and adaptive antiviral immunity by altering costimulatory and coinhibitory pathways, selective targeting of VIP signaling represents an attractive therapeutic target to enhance antiviral immunity.

Allogeneic immunotherapy to optimize the graft-versus-tumor effect: concepts and controversies

Allogeneic stem cell transplantation (SCT) can be considered the most successful method of adoptive immunotherapy of cancer. It is successful in part because of the potent graft-versus-tumor (GVT) effects of the donor graft, which are independent of the conditioning regimen. This potent GVT reaction can be harnessed in some cases to treat patients who relapse after allogeneic SCT with the use of donor leukocyte infusions (DLIs). This has led to the rapid development of reduced-intensity conditioning (RIC) regimens for allogeneic SCT, an approach that relies primarily on GVT activity. However, the effects of GVT have clear disease specificity and remain associated with significant GVHD. Optimization of GVT induction will require a better understanding of the important target antigens and effector cells, as well as the development of methods that enhance GVT reactivity without excessive GVHD. The appropriate clinical setting and timing for GVT induction need to be defined more clearly, but ultimately, the immunologic control of cancer through allogeneic adoptive immunotherapy represents one of the most potent and promising therapeutic strategies for patients with hematologic malignancies.