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Blockade of the T-cell exhaustion marker PD-1 to re-energize the immune response is emerging as a promising cancer treatment. Relapse of hematologic malignancy after allogeneic stem cell transplantation limits the success of this approach, and PD-1 blockade may hold therapeutic promise. However, PD-1 expression and its relationship with post-transplant relapse is poorly described. Because the donor immunity is activated by alloresponses, PD-1 expression may differ from nontransplanted individuals, and PD-1 blockade could risk graft-versus-host disease. Here we analyzed T-cell exhaustion marker kinetics and their relationship with leukemia relapse in 85 patients undergoing myeloablative T-cell-depleted HLA-matched stem cell transplantation. At a median follow-up of 3.5 years, 35 (44%) patients relapsed. PD-1 expression in CD4 and CD8 T cells was comparably elevated in relapsed and nonrelapsed cohorts. Helios + regulatory T cells and CD8 effector memory cells at day 30 emerged as independent predictors of relapse. Although leukemia antigen-specific T cells did not overexpress PD-1, single-cell analysis revealed LAG3 and TIM3 overexpression at relapse. These findings indicate that PD-1 is an unreliable marker for leukemia-specific T-cell exhaustion in relapsing patients but implies other exhaustion markers and suppressor cells as relapse biomarkers., (Copyright © 2018. Published by Elsevier Inc.)

Single-center studies have reported an association between early (before day 100) cytomegalovirus (CMV) reactivation and decreased incidence of relapse for acute myeloid leukemia (AML) following allogeneic hematopoietic cell transplantation. To substantiate these preliminary findings, the Center for International Blood and Marrow Transplant Research (CIBMTR) Database was interrogated to analyze the impact of CMV reactivation on hematologic disease relapse in the current era. Data from 9469 patients transplanted with bone marrow or peripheral blood between 2003 and 2010 were analyzed according to 4 disease categories: AML (n = 5310); acute lymphoblastic leukemia (ALL, n = 1883); chronic myeloid leukemia (CML, n = 1079); and myelodysplastic syndrome (MDS, n = 1197). Median time to initial CMV reactivation was 41 days (range, 1-362 days). CMV reactivation had no preventive effect on hematologic disease relapse irrespective of diagnosis. Moreover, CMV reactivation was associated with higher nonrelapse mortality [relative risk [RR] among disease categories ranged from 1.61 to 1.95 and P values from .0002 to <.0001; 95% confidence interval [CI], 1.14-2.61). As a result, CMV reactivation was associated with lower overall survival for AML (RR = 1.27; 95% CI, 1.17-1.38; P <.0001), ALL (RR = 1.46; 95% CI, 1.25-1.71; P <.0001), CML (RR = 1.49; 95% CI, 1.19-1.88; P = .0005), and MDS (RR = 1.31; 95% CI, 1.09-1.57; P = .003). In conclusion, CMV reactivation continues to remain a risk factor for poor posttransplant outcomes and does not seem to confer protection against hematologic disease relapse.

This chapter focuses on the recent advances in adoptive T-cell immunotherapies, not only for patients after hematopoietic stem cell transplantation, but also in the autologous setting using T cells early in the disease process for the treatment of the highest-risk patients with leukemias and lymphomas. The particular emphasis is to highlight the role of T-cell therapies for hematologic malignancies using a non-gene-transfer approach to direct specificity, including the clinical use of T-cell therapies for EBV-associated lymphomas and strategies for targeting nonviral lymphoma- and leukemia-associated antigens., (© 2014 by The American Society of Hematology. All rights reserved.)

Although natural killer (NK) cells can be readily generated for adoptive therapy with current techniques, their optimal application to treat malignant diseases requires an appreciation of the dynamic balance between signals that either synergize with or antagonize each other. Individuals display wide differences in NK function that determine their therapeutic efficacy. The ability of NK cells to kill target cells or produce cytokines depends on the balance between signals from activating and inhibitory cell-surface receptors. The selection of NK cells with a predominant activating profile is critical for delivering successful anti-tumor activity. This can be achieved through selection of killer immunoglobulin-like receptor-mismatched NK donors and by use of blocking molecules against inhibitory pathways. Optimum NK cytotoxicity may require licensing or priming with tumor cells. Recent discoveries in the molecular and cellular biology of NK cells inform in the design of new strategies, including adjuvant therapies, to maximize the cytotoxic potential of NK cells for adoptive transfer to treat human malignancies., (Copyright © 2014 International Society for Cellular Therapy. All rights reserved.)

Purpose: GVHD after allogeneic hematopoietic stem cell transplantation (alloSCT) has been associated with low numbers of circulating CD4(+)CD25(+)FoxP3(+) regulatory T cells (Tregs). Because Tregs express high levels of the interleukin (IL)-2 receptor, they may selectively expand in vivo in response to doses of IL-2 insufficient to stimulate T effector T-cell populations, thereby preventing GVHD., Experimental Design: We prospectively evaluated the effects of ultra low-dose (ULD) IL-2 injections on Treg recovery in pediatric patients after alloSCT and compared this recovery with Treg reconstitution post alloSCT in patients without IL-2. Sixteen recipients of related (n = 12) or unrelated (n = 4) donor grafts received ULD IL-2 post hematopoietic stem cell transplantation (HSCT; 100,000-200,000 IU/m(2) ×3 per week), starting

Patients with leukemia relapsing after allogeneic hematopoietic SCT have a dismal prognosis. A second SCT offers a further opportunity for cure, but has a high rate of treatment failure. To determine the utility of this option, we analyzed 59 consecutive patients relapsing after a myeloablative HLA-matched sibling T cell-depleted (TCD) SCT. Twenty-five patients (13 relapsing within 6 months and 12 relapsing between 6 and 170 months after the first SCT) received a T-replete second SCT. Thirty-eight patients relapsing early had a shorter survival than the 21 patients relapsing later (median 96 vs 298 days, P=0.0002). In patients relapsing early, the second SCT did not improve OS compared with patients receiving non-SCT treatments (median survival 109 vs 80 days, P=0.41). In patients relapsing late, despite an early trend in favor of second SCT, survival was comparable for patients receiving a second SCT compared with non retransplanted patients (median survival 363.5 vs 162 days, P=0.49). Disappointingly, our results do not demonstrate an important survival benefit for a second T-replete allogeneic SCT to treat relapse following a TCD SCT.

Background: We previously showed that vaccination with one dose of PR1 and WT1 peptides induces transient anti-leukemia immunity. We hypothesized that maintenance of a sustained anti-leukemia response may require frequent boost injections., Design and Methods: Eight patients with myeloid malignancies were enrolled in this phase II study, and 6 completed 6 injections of PR1 and WT1 peptides in Montanide-adjuvant with GM-CSF, every two weeks., Results: Both high- and low-avidity PR1 or WT1-specific CD8(+) T cells were detected in all evaluable patients after the first vaccine dose. Repeated vaccination led to selective deletion of high avidity PR1- and WT1-specific CD8(+) T cells and was not associated with significant reduction in WT1-expression. Additional boosting failed to increase vaccine-induced CD8(+) T-cell frequencies further and in all patients the response was lost before the 6(th) dose. PR1- or WT1-specific CD8(+) T cells were not detected in bone marrow samples, excluding their preferential localization to this site. Following a booster injection three months after the 6(th) vaccine dose, no high-avidity PR1 or WT1-specific CD8(+) T cells could be detected, whereas low-avidity T cells were readily expanded., Conclusions: These data support the immunogenicity of PR1 and WT1 peptide vaccines. However, repeated delivery of peptides with Montanide-adjuvant and GM-CSF leads to rapid loss of high-avidity peptide-specific CD8(+) T cells. These results may offer an explanation for the lack of correlation between immune and clinical responses observed in a number of clinical trials of peptide vaccination. New approaches are needed to induce long-term high-avidity memory responses against leukemia antigens.

Allogeneic stem cell transplantation remains a curative treatment for haematological malignancies resistant to other treatment approaches through the unique graft-versus-leukaemia effect (GvL). However, the lack of specificity of this response results in the targeting of normal tissue, and the morbidity and mortality associated with graft-versus-host disease (GvHD). Further improvements in exploiting the GvL effect to prevent relapse in high-risk leukaemias while minimizing toxicity have focused on the use of targeted anti-leukaemic immunotherapy. These strategies include the use of vaccines against minor histocompatibility antigens (HA-1, HA-2 and H-Y) and leukaemia-specific antigens (proteinase 3, Wilms' tumour 1 and BCR-ABL), and the adoptive transfer of leukaemia-specific T cells. The unique post-transplant milieu, which is characterized by lymphopenia, regulatory T-cell depletion and the release of growth factors, offers the opportunity to promote the expansion of engrafted T cells and enhance the specific GvL response. Techniques to reduce regulatory T-cell control over T-cell responses to leukaemia antigens could further enhance GvL reactivity. Finally, these approaches to increase GvL effects would be facilitated by transplant approaches to deplete GvHD alloresponses selectively while preserving GvL reactivity.

The graft-versus-leukaemia (GVL) effect is a central component of the stem cell allograft's ability to cure haematological malignancies. The GVL effect is mediated by donor-derived natural killer cells and T lymphocytes, which have distinct mechanisms of recognizing and targeting the recipient's malignant cells. After transplantation the cytokine milieu is favourable to the early establishment of a GVL effect, but the need to prevent graft-versus-host disease limits the full potential of this process. Clinical studies have identified some critical components of the transplant preparation, donor selection, stem cell source (peripheral blood versus bone marrow) and post-transplant management that can be manipulated to optimize the GVL effect. However, further developments focusing on the selective depletion of unwanted alloreactivity with preservation of GVL effects, and the use of vaccines or the adoptive transfer of leukaemia-specific lymphocytes, will be required to enhance the GVL effect to reliably eradicate more resistant leukaemias.

Regulatory T cells (T(reg)s) that constitutively express FOXP3 are instrumental to the maintenance of tolerance and may suppress graft-versus-host disease (GVHD) in humans. To determine whether regulatory T cells in allogeneic stem cell transplants (SCTs) ameliorate GVHD after transplantation, we quantitated the coexpression of FOXP3 on CD4(+) T cells in 32 donor SCTs infused into HLA-matched siblings and examined GVHD incidence in respective recipients. High CD4(+)FOXP3(+) T-cell count in the donor was associated with a reduced risk of GVHD. We monitored T(reg)s during immune reconstitution in 21 patients with leukemia undergoing a T-cell-depleted allogeneic SCT. Early after SCT, there was a significant expansion in the CD4(+)FOXP3(+) T-cell compartment. A low CD4(+)FOXP3(+) T-cell count early after SCT (day 30) was associated with an increased risk of GVHD, and the ratio of CD4(+)FOXP3(+) T cells to CD4(+)CD25(+)FOXP3(-) T cells was significantly reduced in patients with GVHD, suggesting diminished control of effector T cells. Our findings suggest that graft T(reg) content may predict for risk of GVHD after SCT. Determining the T(reg) levels in the donor and manipulating T(reg)s early after transplantation may provide a new approach to controlling GVHD.

Purpose: Antigens derived from the Wilms' tumor (WT1) protein, which is overexpressed in leukemias, are attractive targets for immunotherapy. Four HLA-A*0201-restricted WT1-derived epitopes have been identified: WT37, WT126, WT187, and WT235. We determined the natural immunogenecity of these antigens in patients with hematologic malignancies and healthy donor., Experimental Design: To detect very low frequencies of WT1-specific CD8+ T cells, we used quantitative reverse transcription-PCR to measure IFN-gamma mRNA production by WT1 peptide-pulsed CD8+ T cells from 12 healthy donors, 8 patients with chronic myelogenous leukemia, 6 patients with acute myelogenous leukemia, and 8 patients with acute lymphoblastic leukemia., Results: Responses were detected in 5 of 8 chronic myelogenous leukemia patients, 4 of 6 patients with acute myelogenous leukemia, and 7 of 12 healthy donors. No responses were detected in patients with acute lymphoblastic leukemia. The magnitude and extent of these CD8+ T-cell responses was greater in patients with myeloid leukemias than in healthy donors. Clonotypic analysis of WT1-specific CD8+ T cells directly ex vivo in one case showed that this naturally occurring population was oligoclonal. Using fluorescent peptide-MHC class I tetramers incorporating mutations in the alpha3 domain (D227K/T228A) that abrogate binding to the CD8 coreceptor, we were able to confirm the presence of high-avidity T-cell clones within the antigen-specific repertoire., Conclusion: The natural occurrence of high-avidity WT1-specific CD8+ T cells in the periphery could facilitate vaccination strategies to expand immune responses against myeloid leukemias.

We studied the association between CD34 cell dose and transplant outcomes in 359 bone marrow (BM) and 511 peripheral blood stem cell (PBSC) transplant recipients from human leucocyte antigen (HLA)-identical siblings, reported to the International Bone Marrow Transplant Registry (IBMTR). Transplants for leukaemia were performed between 1995 and 1998. Patients were divided into those receiving below or above the median CD34+ dose, for BM (3 x 106/kg) and PBSC (6 x 106/kg) grafts respectively. Cox proportional hazards regression was used to adjust for baseline patient-, disease- and transplant-related characteristics. Analysis of the BM recipients showed that high CD34 cell dose was associated with lower transplant-related mortality [relative risk (RR) = 0.60, P = 0.033] and treatment failure (inverse of leukaemia-free survival, RR = 0.69, P = 0.032). Among PBSC recipients, high CD34 dose was associated with faster recovery of neutrophils to > 0.5 x 109/l (RR = 1.38, P < 0.001) and platelets to > 20 x 109/l (RR = 1.34, P = 0.003), lower risk of relapse (RR = 0.62, P = 0.029) and treatment failure (RR = 0.74, P = 0.03). We conclude that higher CD34 cell doses decrease treatment failure in recipients of HLA-identical sibling BM and PBSC transplants.

Summary: The recognition of the curative potential of the graft‐versus‐leukaemia effect for patients with acute myeloid leukaemia (AML) undergoing stem cell transplantation, and the emergence of immunotherapy as a powerful weapon to treat cancer, has spurred the exploration of the immune landscape of AML to apply immunotherapeutic approaches to curing the disease. While current concepts of cancer immunology and immunotherapy have relevance, there are also unique aspects of immune dysregulation in AML to be considered when designing rational immunotherapy for this leukaemia. This is timely because rapid advances in cancer immunobiology, together with technological developments have opened up the field of immunotherapy for malignant disease. Here the current knowledge of AML immunobiology is summarized together with a description of new immunotherapies to counter immunosuppression and immune evasion by AML. Recent advances in treatment with recombinant antibodies, adoptive cell therapy and vaccines and their future promise in AML treatment are reviewed. [ABSTRACT FROM AUTHOR]

The article discusses the decline of relapse in acute myeloid leukemia through allogeneic stem cell transplantation (SCT) which can reactivate a cytomegalovirus (CMV). It notes that the persistence of the pp65 antigenemia can be triggered by SCT. It mentions that the breakdown of immunosurveillance against residual leukemia can be prevented by CMV reactivation.

Allogeneic hematopoietic stem cell transplantation (HSCT) is a curative treatment for some hematologic malignancies. As the overall number of survivors continues to increase, studies systematically examining outcomes in long-term survivors are needed. We studied the clinical and quality-of-life outcomes in HSCT recipients surviving 5 or more years from HSCT. Since 1993, 262 patients with hematologic malignancies received a T cell-depleted myeloablative HSCT from an HLA-identical sibling at a single center. Ninety-two survived beyond 5 years from HSCT (median follow-up 9.4 years, range: 5.1-15.3). Median age at transplantation was 35 years (range: 10-56). Twenty-two (24%) received a bone marrow transplant, and 70 (76%) received a peripheral blood HSCT. Of the 92 survivors, 60 completed quality-of-life measures. The main outcomes examined were chronic graft-versus-host-disease, disease relapse, survival, health-related quality-of-life (HRQL) (Functional Assessment of Cancer Therapy-General), physical and mental health (SF-36), and symptom experience (Rotterdam Symptom Checklist). Seventy-five (82%) of 92 survivors no longer required systemic immunosuppressive treatment. Four (4.3%) relapsed with leukemia at a median of 8.5 years (range: 6.2-14.0) after HSCT. Four (4.3%) died between 7.4 and 13.4 years post-HSCT (1 relapse, 1 lung cancer, 1 pneumonia, 1 brain hemorrhage). Most survivors beyond 5 years had an excellent performance status with no difference in physical and mental health and higher HRQL scores (P = .02) compared with population norms. Although physical and psychologic symptom distress was low, those with higher symptom distress experienced inferior HRQL. These results show that 5 or more years after T cell-depleted HSCT for hematologic malignancy most individuals survive disease free with an excellent performance status, preserved physical and psychological health, and excellent HRQL. [Copyright &y& Elsevier]

Abstract: Reports have shown a worse outcome for donor-recipient pairs mismatched for ABO blood groups in bone marrow transplantation (BMT). These studies, however, included small and heterogenous study populations, and not all considered bidirectional ABO incompatibility separately. Because the issue remains controversial, we analyzed the effect of ABO mismatch on the overall survival, transplant-related mortality, and occurrence of acute and chronic graft-versus-host disease (GVHD) in a large homogenous group of patients undergoing allogeneic BMT. A total of 3103 patients with early-stage leukemia who underwent transplantation between 1990 and 1998 with bone marrow from an HLA-identical sibling and who were reported to the Center for International Blood and Marrow Transplant Research were studied. The median follow-up was 54 months. A total of 2108 (67.9%) donor-recipient pairs were ABO identical, 451 (14.5%) had a minor mismatch, 430 (13.9%) had a major mismatch, and 114 (3.7%) had a bidirectional ABO mismatch. The groups did not differ significantly in patient or donor characteristics except for more female-to-male sex mismatch in the bidirectional ABO mismatch group (P = .017). In multivariate models of overall survival, transplant-related mortality, and grade II to IV acute GVHD, there were no significant differences among the 4 groups. Bidirectional ABO mismatch was associated with a significantly higher risk of grade III or IV acute GVHD (hazard ratio, 1.869; 95% confidence interval, 1.192-2.93; P = .006). Patients with major ABO mismatch received red blood cell transfusions (P = .001) for a longer timer after transplantation and had a slightly slower neutrophil recovery (P < .001). There was no evidence of a substantial effect of ABO blood group incompatibility on the outcome of conventional BMT among patients with leukemia. [Copyright &y& Elsevier]

Numerous clinical studies link cytomegalovirus (CMV) infection with incomplete posttransplantation T-cell recovery. We hypothesized that the inability of transplant recipients to handle CMV reactivation might correlate with a defective graft-versus-leukemia response and increased posttransplantation morbidity. Between May 1995 and August 2001, 82 patients who were CMV seropositive and survived the first 100 days after transplantation were identified for a day 100 landmark analysis of the effect of CMV reactivation patterns on eventual transplantation outcome. All patients underwent a myeloablative HLA-identical sibling donor T cell-depleted stem cell transplantation with scheduled donor T-cell add-back on day 45. Median follow-up was 1032 days. Forty-two patients who had either no reactivation or only 1 positive test with quick clearance were designated as a CMV immune competent group. Forty patients designated as CMV immune deficient (ID) had at least 2 positive tests. Apart from younger age (33 versus 38 years; P = .05) in the ID group, the 2 groups were balanced for clinical characteristics. In multivariate analysis, ID patients had a significantly higher incidence of leukemia relapse (58% versus 21%; P = .03) and worse disease-free survival (31% versus 66%; P = .04). There was no significant difference in week 1 to 14 posttransplantation lymphocyte counts between the 2 groups. In 67 patients tested 3 to 6 months after transplantation, a proliferative response to CMV antigen (stimulation index ≥2) occurred in 27 of 36 immune competent patients compared with 15 of 31 ID patients (P = .006). These results show that recurrent CMV reactivation in the first 100 days after transplantation predicts for reduced disease-free survival and increased leukemic relapse beyond 100 days and correlates with inferior proliferative responses to CMV. The higher relapse rate may reflect poor immune reconstitution in ID patients or an adverse effect of prolonged antiviral treatment. [Copyright &y& Elsevier]