Search

γδ T cells are potent anticancer effectors with the potential to target tumours broadly, independent of patient-specific neoantigens or human leukocyte antigen background 1-5 . γδ T cells can sense conserved cell stress signals prevalent in transformed cells 2,3 , although the mechanisms behind the targeting of stressed target cells remain poorly characterized. Vγ9Vδ2 T cells-the most abundant subset of human γδ T cells 4 -recognize a protein complex containing butyrophilin 2A1 (BTN2A1) and BTN3A1 (refs. 6-8 ), a widely expressed cell surface protein that is activated by phosphoantigens abundantly produced by tumour cells. Here we combined genome-wide CRISPR screens in target cancer cells to identify pathways that regulate γδ T cell killing and BTN3A cell surface expression. The screens showed previously unappreciated multilayered regulation of BTN3A abundance on the cell surface and triggering of γδ T cells through transcription, post-translational modifications and membrane trafficking. In addition, diverse genetic perturbations and inhibitors disrupting metabolic pathways in the cancer cells, particularly ATP-producing processes, were found to alter BTN3A levels. This induction of both BTN3A and BTN2A1 during metabolic crises is dependent on AMP-activated protein kinase (AMPK). Finally, small-molecule activation of AMPK in a cell line model and in patient-derived tumour organoids led to increased expression of the BTN2A1-BTN3A complex and increased Vγ9Vδ2 T cell receptor-mediated killing. This AMPK-dependent mechanism of metabolic stress-induced ligand upregulation deepens our understanding of γδ T cell stress surveillance and suggests new avenues available to enhance γδ T cell anticancer activity., (© 2023. The Author(s), under exclusive licence to Springer Nature Limited.)

Introduction: We have recently developed a novel T cell engager concept by utilizing γ9δ2TCR as tumor targeting domain, named gamma delta TCR anti-CD3 bispecific molecule (GAB), targeting the phosphoantigen-dependent orchestration of BTN2A1 and BTN3A1 at the surface of cancer cells. GABs are made by the fusion of the ectodomains of a γδTCR to an anti-CD3 single chain variable fragment (scFv) (γδECTO-αCD3), here we explore alternative designs with the aim to enhance GAB effectivity., Methods: The first alternative design was made by linking the variable domains of the γ and δ chain to an anti-CD3 scFv (γδVAR-αCD3). The second alternative design was multimerizing γδVAR-αCD3 proteins to increase the tumor binding valency. Both designs were expressed and purified and the potency to target tumor cells by T cells of the alternative designs was compared to γδECTO-αCD3, in T cell activation and cytotoxicity assays., Results and Discussion: The γδVAR-αCD3 proteins were poorly expressed, and while the addition of stabilizing mutations based on finding for αβ single chain formats increased expression, generation of meaningful amounts of γδVAR-αCD3 protein was not possible. As an alternative strategy, we explored the natural properties of the original GAB design (γδECTO-αCD3), and observed the spontaneous formation of γδECTO-αCD3-monomers and -dimers during expression. We successfully enhanced the fraction of γδECTO-αCD3-dimers by shortening the linker length between the heavy and light chain in the anti-CD3 scFv, though this also decreased protein yield by 50%. Finally, we formally demonstrated with purified γδECTO-αCD3-dimers and -monomers, that γδECTO-αCD3-dimers are superior in function when compared to similar concentrations of monomers, and do not induce T cell activation without simultaneous tumor engagement. In conclusion, a γδECTO-αCD3-dimer based GAB design has great potential, though protein production needs to be further optimized before preclinical and clinical testing., Competing Interests: JK reports grants from Gadeta, Novartis, and Miltenyi Biotech and is the inventor on patents dealing with γδT cell-related aspects, as well as the co-founder and shareholder of Gadeta. EvD and DB are inventor on patents dealing with γδT cell-related aspects. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 van Diest, Nicolasen, Kramer, Zheng, Hernández-López, Beringer and Kuball.)

Extending the success of cellular immunotherapies against blood cancers to the realm of solid tumors will require improved in vitro models that reveal therapeutic modes of action at the molecular level. Here we describe a system, called BEHAV3D, developed to study the dynamic interactions of immune cells and patient cancer organoids by means of imaging and transcriptomics. We apply BEHAV3D to live-track >150,000 engineered T cells cultured with patient-derived, solid-tumor organoids, identifying a 'super engager' behavioral cluster comprising T cells with potent serial killing capacity. Among other T cell concepts we also study cancer metabolome-sensing engineered T cells (TEGs) and detect behavior-specific gene signatures that include a group of 27 genes with no previously described T cell function that are expressed by super engager killer TEGs. We further show that type I interferon can prime resistant organoids for TEG-mediated killing. BEHAV3D is a promising tool for the characterization of behavioral-phenotypic heterogeneity of cellular immunotherapies and may support the optimization of personalized solid-tumor-targeting cell therapies., (© 2022. The Author(s).)

Unmanipulated haploidentical hematopoietic stem cell transplantation (HCT) with post-transplantation cyclophosphamide as graft-versus-host disease (GVHD) prophylaxis (haplo-PTCY) and unrelated double-unit umbilical cord blood transplantation (dUCBT) are feasible options for treating patients with high-risk acute myelogenous leukemia (AML). This study compared outcomes after dUCBT and haplo-HCT using peripheral blood stem cells (PBSCs) in adult patients with AML in complete remission (CR) who underwent transplantation in European Society for Blood and Marrow Transplantation (EBMT)-affiliated centers. In a population of adults with de novo AML in first or second CR, we compared outcomes after dUCBT (n = 165) and after haplo-PTCY PBSC (n = 544) performed between January 2013 and December 2018. Patients receiving in vivo antithymocyte globulin, Campath, or ex vivo T cell depletion were excluded. The median follow-up was 33 months for the haplo-PTCY arm and 52 months for the dUCBT arm. No statistically significant differences were observed between the 2 arms in the rates of grade II-IV acute graft-versus-host disease (GVHD) (hazard ratio [HR], 1.31; P = .18), grade III-IV acute GVHD (HR, 1.17; P = .56), chronic GVHD (HR, .86; P = .48), relapse (HR, 1.07; P = .77), nonrelapse mortality (NRM) (HR, .94; P = .77), leukemia-free survival (LFS) (HR, .99; P = .95), or overall survival (OS) (HR, .99; P = .97). Favorable cytogenetic risk was the sole factor predictive of lower relapse incidence (RI). Younger age at transplantation was associated with lower NRM and higher LFS and OS. Both dUCBT and haplo-PTCY with PBSCs can be considered valid approaches for adult AML patients in CR. New strategies should be investigated in both settings to define the most appropriate conditioning regimen and potentially decrease RI and NRM through better immune reconstitution and optimal supportive care., (Copyright © 2022 The American Society for Transplantation and Cellular Therapy. Published by Elsevier Inc. All rights reserved.)

Allo-HSCT with CCR5Δ32/Δ32 donor cells is the only curative HIV-1 intervention. We investigated the impact of allo-HSCT on the viral reservoir in PBMCs and post-mortem tissue in two patients. IciS-05 and IciS-11 both received a CCR5Δ32/Δ32 allo-HSCT. Before allo-HSCT, ultrasensitive HIV-1 RNA quantification; HIV-1-DNA quantification; co-receptor tropism analysis; deep-sequencing and viral characterization in PBMCs and bone marrow; and post-allo-HSCT, ultrasensitive RNA and HIV-1-DNA quantification were performed. Proviral quantification, deep sequencing, and viral characterization were done in post-mortem tissue samples. Both patients harbored subtype B CCR5-tropic HIV-1 as determined genotypically and functionally by virus culture. Pre-allo-HSCT, HIV-1-DNA could be detected in both patients in bone marrow, PBMCs, and T-cell subsets. Chimerism correlated with detectable HIV-1-DNA LTR copies in cells and tissues. Post-mortem analysis of IciS-05 revealed proviral DNA in all tissue biopsies, but not in PBMCs. In patient IciS-11, who was transplanted twice, no HIV-1-DNA could be detected in PBMCs at the time of death, whereas HIV-1-DNA was detectable in the lymph node. In conclusion, shortly after CCR5Δ32/Δ32, allo-HSCT HIV-1-DNA became undetectable in PBMCs. However, HIV-1-DNA variants identical to those present before transplantation persisted in post-mortem-obtained tissues, indicating that these tissues play an important role as viral reservoirs.

γ9δ2T cells fill a distinct niche in human immunity due to the unique physiology of the phosphoantigen-reactive γ9δ2TCR. Here, we highlight reproducible TCRδ complementarity-determining region 3 (CDR3δ) repertoire patterns associated with γ9δ2T cell proliferation and phenotype, thus providing evidence for the role of the CDR3δ in modulating in vivo T-cell responses. Features that determine γ9δ2TCR binding affinity and reactivity to the phosphoantigen-induced ligand in vitro appear to similarly underpin in vivo clonotypic expansion and differentiation. Likewise, we identify a CDR3δ bias in the γ9δ2T cell natural killer receptor (NKR) landscape. While expression of the inhibitory receptor CD94/NKG2A is skewed toward cells bearing putative high-affinity TCRs, the activating receptor NKG2D is expressed independently of the phosphoantigen-sensing determinants, suggesting a higher net NKR activating signal in T cells with TCRs of low affinity. This study establishes consistent repertoire-phenotype associations and justifies stratification for the T-cell phenotype in future research on γ9δ2TCR repertoire dynamics., Competing Interests: JK reports grants from Gadeta, Novartis, and Miltenyi Biotech and is the inventor of patents dealing with γδT cell-related aspects, as well as the co-founder and shareholder of Gadeta. AV, AJ, DB, and ZS are inventors of patents dealing with γδT cell-related aspects. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Vyborova, Janssen, Gatti, Karaiskaki, Yonika, van Dooremalen, Sanders, Beringer, Straetemans, Sebestyen and Kuball.)

Graft-versus-host disease (GVHD) is the most important complication of allogeneic hematopoietic stem cell transplantation (alloHSCT). We performed a prospective randomized, multicenter, phase 3 trial to study whether posttransplant cyclophosphamide (PT-Cy) combined with a short course of cyclosporine A (CsA) would result in a reduction of severe GVHD and improvement of GVHD-free, relapse-free survival (GRFS) as compared with the combination of CsA and mycophenolic acid (MPA) after nonmyeloablative (NMA) matched related and unrelated peripheral blood alloHSCT. Between October 2013 and June 2018, 160 patients diagnosed with a high-risk hematological malignancy and having a matched related or at least 8 out of 8 HLA-matched unrelated donor were randomized and allocated in a 1:2 ratio to CsA/MPA or PT-Cy/CsA; a total of 151 patients were transplanted (52 vs 99 patients, respectively). The cumulative incidence of grade 2 to 4 acute GVHD at 6 months was 48% in recipients of CsA/MPA vs 30% following PT-Cy/CsA (hazard ratio [HR], 0.48; 95% confidence interval [CI], 0.29-0.82; P = .007). The 2-year cumulative incidence of extensive chronic GVHD was 48% vs 16% (HR, 0.36; 95% CI, 0.21-0.64; P < .001). The 1-year estimate of GRFS was 21% (11% to 32%) vs 45% (35% to 55%), P < .001. With a median follow-up of 56.4 months, relapse incidence, progression-free survival, and overall survival were not significantly different between the 2 treatment arms. PT-Cy combined with a short course of CsA after NMA matched alloHSCT significantly improves GRFS due to a significant reduction in severe acute and chronic GVHD., (© 2022 by The American Society of Hematology. Licensed under Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0), permitting only noncommercial, nonderivative use with attribution. All other rights reserved.)

Chimeric antigen receptor (CAR) T cell therapies have resulted in profound clinical responses in the treatment of CD19-positive hematological malignancies, but a significant proportion of patients do not respond or relapse eventually. As an alternative to CAR T cells, T cells can be engineered to express a tumor-targeting T cell receptor (TCR). Due to HLA restriction of TCRs, CARs have emerged as a preferred treatment moiety when targeting surface antigens, despite the fact that functional differences between engineered TCR (eTCR) T and CAR T cells remain ill-defined. Here, we compared the activity of CAR T cells versus engineered TCR T cells in targeting the B cell malignancy-associated antigen CD20 as a function of antigen exposure. We found CAR T cells to be more potent effector cells, producing higher levels of cytokines and killing more efficiently than eTCR T cells in a short time frame. However, we revealed that the increase of antigen exposure significantly impaired CAR T cell expansion, a phenotype defined by high expression of coinhibitory molecules and effector differentiation. In contrast, eTCR T cells expanded better than CAR T cells under high antigenic pressure, with lower expression of coinhibitory molecules and maintenance of an early differentiation phenotype, and comparable clearance of tumor cells., Competing Interests: The authors report no conflict of interest., (© 2022 The Author(s). Published with license by Taylor & Francis Group, LLC.)

The optimal CD34 + cell dose in the setting of RIC allo-HCT for myelofibrosis (MF) remains unknown. We retrospectively analyzed 657 patients with primary or secondary MF transplanted with use of peripheral blood (PB) stem cells after fludarabine/melphalan or fludarabine/busulfan RIC regimen. Median patient age was 58 (range, 22-76) years. Donors were HLA-identical sibling (MSD) or unrelated (UD). Median follow-up was 46 (2-194) months. Patients transplanted with higher doses of CD34 + cells (>7.0 × 10 6 /kg), had an increased chance of achievement of both neutrophil (hazard ratio (HR), 1.46; P < 0.001) and platelet engraftment (HR, 1.43; P < 0.001). In a model with interaction, for patients transplanted from a MSD, higher CD34 + dose was associated with improved overall survival (HR, 0.63; P = 0.04) and relapse-free survival (HR, 0.61; P = 0.02), lower risk of non-relapse mortality (HR, 0.57; P = 0.04) and higher rate of platelet engraftment. The combined effect of higher cell dose and UD was apparent only for higher neutrophil and platelet recovery rate. We did not document any detrimental effect of high CD34 + dose on transplant outcomes. More bulky splenomegaly was an adverse factor for survival, engraftment and NRM. Our analysis suggests a potential benefit for MF patients undergoing RIC PB-allo-HCT receiving more than 7.0 × 10 6 /kg CD34 + cells., (© 2021. The Author(s), under exclusive licence to Springer Nature Limited.)

Consensus on timing of post-hematopoietic stem cell transplantation (HSCT) vaccination is currently lacking and is therefore assessed in this review. PubMed was searched systematically for articles concerning vaccination post-HSCT and included a basis in predefined criteria. To enable comparison, data were extracted and tables were constructed per vaccine, displaying vaccine response as either seroprotection or seroconversion for allogeneic HSCT (alloHSCT) and autologous HSCT (autoHSCT) separately. A total of 33 studies were included with 1914 patients in total: 1654 alloHSCT recipients and 260 autoHSCT recipients. In alloHSCT recipients, influenza vaccine at 7-48 months post-transplant resulted in responses of 10-97%. After 12 months post-transplant, responses were >45%. Pneumococcal vaccination 3-25 months post-transplant resulted in responses of 43-99%, with the response increasing with time. Diphtheria, tetanus, pertussis, poliomyelitis and Haemophilus influenzae type b at 6-17 months post-transplant: 26-100%. Meningococcal vaccination at 12 months post-transplant: 65%. Hepatitis B vaccine at 6-23 months post-transplant: 40-94%. Measles, mumps and rubella at 41-69 months post-transplant: 19-72%. In general, autoHSCT recipients obtained slightly higher responses compared with alloHSCT recipients. Conclusively, responses to childhood immunization vaccines post-HSCT are poor in comparison with healthy individuals. Therefore, evaluation of response might be indicated. Timing of revaccination is essential for optimal response. An individualized approach might be necessary for optimizing vaccine responses.

Vaccination after hematopoietic stem cell transplantation (HSCT) is essential to protect high-risk patients against potentially lethal infections. Though multiple studies have evaluated vaccine specific responses, no comprehensive analysis of a complete vaccination schedule post-HSCT has been performed and little is known about predictors for vaccine failure. In this context, allogeneic HSCT (alloHSCT) patients were included and vaccinated starting one year post-transplantation. Antibody responses were measured by Multiplex Immuno Assay for pneumococcal (PCV13), meningococcal C, diphtheria, pertussis, tetanus and Haemophilus influenza type b one month after the last vaccination and correlated to clinical and immunological parameters. Vaccine failure was defined as antibody response above vaccine-specific cut-off values for less than four out of six vaccines. Ninety-six patients were included of which 27.1% was found to have vaccine failure. Only 40.6% of all patients responded adequately to all six vaccines. In multivariate analysis, viral reactivation post-HSCT (OR 6.53; P = 0.03), B-cells <135 per mm 3 (OR 7.24; P = 0.00) and NK-cells <170 per mm 3 (OR 11.06; P = 0.00) were identified as predictors for vaccine failure for vaccination at one year post-alloHSCT. Measurement of antibody responses and an individualized approach for revaccination guided by clinical status and immune reconstitution of B-cells and NK-cells may improve vaccine responses., (© 2021. The Author(s), under exclusive licence to Springer Nature Limited.)

Nonmyeloablative regimens are used for allogeneic hematopoietic cell transplantation (HCT) of older or medically unfit patients, but successful outcome is still hindered by graft-versus-host disease (GVHD), especially in the setting of HLA-mismatched HCT. New GVHD prophylaxis strategies are emerging, including the triple drug strategy, that improve the GVHD-free and relapse-free survival (GRFS). Because the impact of ATG in HLA-mismatched Flu-TBI-based nonmyeloablative HCT has not been investigated, we did a retrospective analysis in three Dutch centers. 67 patients were evaluable, with a median age of 56 years. Overall survival, relapse-free survival and GRFS at 4 years were 52%, 43%, and 38%, respectively. NRM findings and cumulative incidence of relapse at 4 years were 26% and 31%, respectively. At 1-year grade II-IV had occurred in 40% of the patients, and the incidence of moderate-severe chronic GVHD incidence was 16%. Acknowledging the limitations of retrospective analyses, we conclude that the use of ATG for HLA-mismatched truly nonmyeloablative Flu-TBI HCT is feasible and results in acceptable long term outcomes, especially with regards to GRFS. We consider ATG in combination with cyclosporin and mycophenolate mofetil as an alternative for the triple drug strategy that uses sirolimus for GVHD prophylaxis in this particular setting., (© 2021. The Author(s), under exclusive licence to Springer Nature Limited.)

γδT cell receptors (γδTCRs) recognize a broad range of malignantly transformed cells in mainly a major histocompatibility complex (MHC)-independent manner, making them valuable additions to the engineered immune effector cell therapy that currently focuses primarily on αβTCRs and chimeric antigen receptors (CARs). As an exception to the rule, we have previously identified a γδTCR, which exerts antitumor reactivity against HLA-A*24:02-expressing malignant cells, however without the need for defined HLA-restricted peptides, and without exhibiting any sign of off-target toxicity in humanized HLA-A*24:02 transgenic NSG (NSG-A24:02) mouse models. This particular tumor-HLA-A*24:02-specific Vγ5Vδ1TCR required CD8αα co-receptor for its tumor reactive capacity when introduced into αβT cells engineered to express a defined γδTCR (TEG), referred to as TEG011; thus, it was only active in CD8 + TEG011. We subsequently explored the concept of additional redirection of CD4 + T cells through co-expression of the human CD8α gene into CD4 + and CD8 + TEG011 cells, later referred as TEG011&#95;CD8α. Adoptive transfer of TEG011&#95;CD8α cells in humanized HLA-A*24:02 transgenic NSG (NSG-A24:02) mice injected with tumor HLA-A*24:02 + cells showed superior tumor control in comparison to TEG011, and to mock control groups. The total percentage of mice with persisting TEG011&#95;CD8α cells, as well as the total number of TEG011&#95;CD8α cells per mice, was significantly improved over time, mainly due to a dominance of CD4 + CD8 + double-positive TEG011&#95;CD8α, which resulted in higher total counts of functional T cells in spleen and bone marrow. We observed that tumor clearance in the bone marrow of TEG011&#95;CD8α-treated mice associated with better human T cell infiltration, which was not observed in the TEG011-treated group. Overall, introduction of transgenic human CD8α receptor on TEG011 improves antitumor reactivity against HLA-A*24:02 + tumor cells and further enhances in vivo tumor control., Competing Interests: DB, ZS, and JK are inventors on different patents with γδTCR sequences, recognition mechanisms, and isolation strategies. JK is cofounder and shareholder of Gadeta (www.gadeta.nl). The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Johanna, Hernández-López, Heijhuurs, Scheper, Bongiovanni, de Bruin, Beringer, Oostvogels, Straetemans, Sebestyen and Kuball.)

Optimal donor choice for a second allogeneic hematopoietic cell transplant (allo-HCT) in relapsed acute lymphoblastic leukemia (ALL) remains undefined. We compared outcomes using HLA-matched unrelated donors (MUD) versus haploidentical donors in this population. Primary endpoint was overall survival (OS). The MUD allo-HCT group comprised 104 patients (male = 56, 54%), median age 36 years, mostly (76%) with B-cell phenotype in complete remission (CR) (CR2/CR3 + = 76, 73%). The 61 patients (male = 38, 62%) in the haploidentical group were younger, median age 30 years (p = 0.002), had mostly (79%) a B-cell phenotype and the majority were also in CR at time of the second allo-HCT (CR2/CR3 + = 40, 66%). Peripheral blood stem cells was the most common cell source in both, but a significantly higher number in the haploidentical group received bone marrow cells (26% vs. 4%, p < 0.0001). A haploidentical donor second allo-HCT had a 1.5-fold higher 2-year OS (49% vs. 31%), albeit not statistically significant (p = 0.13). A longer time from first allo-HCT to relapse was associated with improved OS, leukemia-free survival, graft-versus-host disease-free-relapse-free survival, and lower cumulative incidences of relapse and non-relapse mortality. Results suggest no major OS difference when choosing either a MUD or haploidentical donor for ALL patients needing a second allo-HCT., (© 2021. The Author(s), under exclusive licence to Springer Nature Limited.)

Background: Allogeneic hematopoietic cell transplantation (allo-HCT) using a mismatched unrelated donor (MMUD) and cord blood transplantation (CBT) are valid alternatives for patients without a fully human leukocyte antigen (HLA)-matched donor. Here, we compared the allo-HCT outcomes of CBT versus single-allele-mismatched MMUD allo-HCT with post-transplant cyclophosphamide (PTCy) in acute myeloid leukemia., Methods: Patients who underwent a first CBT without PTCy (N = 902) or allo-HCT from a (HLA 9/10) MMUD with PTCy (N = 280) were included in the study. A multivariate regression analysis was performed for the whole population. A matched-pair analysis was carried out by propensity score-based 1:1 matching of patients (177 pairs) with known cytogenetic risk., Results: The incidence of grade II-IV and grade III-IV acute graft-versus-host disease (GVHD) at 6 months was 36% versus 32% (p = 0.07) and 15% versus 11% (p = 0.16) for CBT and MMUD cohorts, respectively. CBT was associated with a higher incidence of graft failure (11% vs. 4%, p < 0.01) and higher 2-year non-relapse mortality (NRM) (30% vs. 16%, p < 0.01) compared to MMUD. In the multivariate analysis, CBT was associated with a higher risk of, NRM (HR = 2.09, 95% CI 1.46-2.99, p < 0.0001), and relapse (HR = 1.35, 95% CI 1-1.83, p = 0.05), which resulted in worse leukemia-free survival (LFS) (HR = 1.68, 95% CI 1.34-2.12, p < 0.0001), overall survival (OS) (HR = 1.7, 95% CI 1.33-2.17, p < 0.0001), and GVHD-free, relapse-free survival (GRFS) (HR = 1.49, 95% CI 1.21-1.83, p < 0.0001) compared to MMUD. The risk of grade II-IV acute GVHD (p = 0.052) and chronic GVHD (p = 0.69) did not differ significantly between the cohorts. These results were confirmed in a matched-pair analysis., Conclusions: CBT was associated with lower LFS, OS, and GRFS due to higher NRM, compared to MMUD allo-HCT with PTCy. In the absence of a fully matched donor, 9/10 MMUD with PTCy may be preferred over CBT.

We conducted a multicenter prospective single-arm phase 1/2 study that assesses the outcome of αβ T-cell depleted allogeneic hematopoietic stem cell transplantation (allo-HSCT) of peripheral blood derived stem cells from matched related, or unrelated donors (10/10 and 9/10) in adults, with the incidence of acute graft-versus-host disease (aGVHD) as the primary end point at day 100. Thirty-five adults (median age, 59; range, 19-69 years) were enrolled. Conditioning consisted of antithymocyte globulin, busulfan, and fludarabine, followed by 28 days of mycophenolic acid after allo-HSCT. The minimal follow-up time was 24 months. The median number of infused CD34+ cells and αβ T cells were 6.1 × 106 and 16.3 × 103 cells per kg, respectively. The cumulative incidence (CI) of aGVHD grades 2-4 and 3-4 at day 100 was 26% and 14%. One secondary graft failure was observed. A prophylactic donor lymphocyte infusion (DLI) (1 × 105 CD3+ T cells per kg) was administered to 54% of the subjects, resulting in a CI of aGVHD grades 2-4 and 3-4 to 37% and 17% at 2 years. Immune monitoring revealed an early reconstitution of natural killer (NK) and γδ T cells. Cytomegalovirus reactivation associated with expansion of memory-like NK cells. The CI of relapse was 29%, and the nonrelapse mortality 32% at 2 years. The 2-year CI of chronic GVHD (cGVHD) was 23%, of which 17% was moderate. We conclude that only 26% of patients developed aGVHD 2-4 after αβ T-cell-depleted allo-HSCT within 100 days and was associated with a low incidence of cGVHD after 2 years. This trial was registered at www.trialregister.nl as #NL4767., (© 2021 by The American Society of Hematology.)

We designed a study to describe the incidence of intracranial hemorrhage according to severity and duration of thrombocytopenia and to quantify the associations of platelet transfusions with intracranial hemorrhage in patients with acute leukemia. In this case-control study nested in a cohort of 859 leukemia patients, cases (n = 17) were patients diagnosed with intracranial hemorrhage who were matched with control patients (n = 55). We documented platelet counts and transfusions for seven days before the intracranial hemorrhage in cases and in a "matched" week for control patients. Three measures of platelet count exposure were assessed in four potentially important time periods before hemorrhage. Among these leukemia patients, we observed the cumulative incidence of intracranial hemorrhage of 3.5%. Low platelet counts were, especially in the three to seven days preceding intracranial hemorrhage, associated with the incidence of intracranial hemorrhage, although with wide confidence intervals. Platelet transfusions during the week preceding the hemorrhage were associated with higher incidences of intracranial hemorrhage; rate ratios (95% confidence interval) for one or two platelet transfusions and for more than two transfusions compared with none were 4.04 (0.73 to 22.27) and 8.91 (1.53 to 51.73) respectively. Thus, among acute leukemia patients, the risk of intracranial hemorrhage was higher among patients with low platelet counts and after receiving more platelet transfusions. Especially, the latter is likely due to clinical factors leading to increased transfusion needs.

Graft-versus-host disease (GVHD) and cytomegalovirus (CMV)-related complications are leading causes of mortality after unrelated-donor hematopoietic cell transplantation (UD-HCT). The non-conventional MHC class I gene MICB, alike MICA, encodes a stress-induced polymorphic NKG2D ligand. However, unlike MICA, MICB interacts with the CMV-encoded UL16, which sequestrates MICB intracellularly, leading to immune evasion. Here, we retrospectively analyzed the impact of mismatches in MICB amino acid position 98 (MICB98), a key polymorphic residue involved in UL16 binding, in 943 UD-HCT pairs who were allele-matched at HLA-A, -B, -C, -DRB1, -DQB1 and MICA loci. HLA-DP typing was further available. MICB98 mismatches were significantly associated with an increased incidence of acute (grade II-IV: HR, 1.20; 95% CI, 1.15 to 1.24; P < 0.001; grade III-IV: HR, 2.28; 95% CI, 1.56 to 3.34; P < 0.001) and chronic GVHD (HR, 1.21; 95% CI, 1.10 to 1.33; P < 0.001). MICB98 matching significantly reduced the effect of CMV status on overall mortality from a hazard ratio of 1.77 to 1.16. MICB98 mismatches showed a GVHD-independent association with a higher incidence of CMV infection/reactivation (HR, 1.84; 95% CI, 1.34 to 2.51; P < 0.001). Hence selecting a MICB98-matched donor significantly reduces the GVHD incidence and lowers the impact of CMV status on overall survival.

Nonmyeloablative (NMA) conditioning regimens facilitate allogeneic stem cell transplantation (alloSCT) in elderly patients and/or in those with comorbidities. The acute leukemia working party (ALWP) of the European Society for Blood and Marrow Transplantation (EBMT) compared the outcomes of patients ≥60 years with AML in first complete remission (CR1), that had received an alloSCT following NMA conditioning, i.e. either fludarabine/busulfan (FB2) or fludarabine/total-body-irradiation-2Gy (FluTBI2Gy). A total of 1088 patients were included (median age 65 years). Donors were matched siblings (MSD) and matched unrelated donors (MUD) in 47% and 53%, respectively. In vivo T-cell depletion (TCD) was applied to 79% and none (0%) of patients in the FB2 and FluTBI2Gy groups, respectively. In the MSD group we found a trend for less extensive cGVHD in patients receiving FB2 with in vivo TCD, HR: 0.49, p = 0.08, and in those without worse NRM, HR: 2.14, p = 0.04, and a trend for more total cGVHD, HR: 1.61, p = 0.09. Patients transplanted from MUDs had a significantly higher incidence of total cGVHD, extensive cGVHD and a worse GRFS with FluTBI2Gy in comparison to FB2, HR: 2.44; p < 0.0001; HR 4.59; p < 0.00001 and HR: 1.35; p = 0.03, respectively. No differences were observed with respect to LFS, OS, RI, NRM, and aGVHD.

In many healthcare settings, benchmarking for complex procedures has become a mandatory requirement by competent authorities, regulators, payers and patients to assure clinical performance, cost-effectiveness and safe care of patients. In several countries inside and outside Europe, benchmarking systems have been established for haematopoietic stem cell transplantation (HSCT), but access is not universal. As benchmarking is now integrated into the FACT-JACIE standards, the EBMT and JACIE established a Clinical Outcomes Group (COG) to develop and introduce a universal system accessible across EBMT members. Established systems from seven European countries (United Kingdom, Italy, Belgium, France, Germany, Spain, Switzerland), USA and Australia were appraised, revealing similarities in process, but wide variations in selection criteria and statistical methods. In tandem, the COG developed the first phase of a bespoke risk-adapted international benchmarking model for one-year survival following allogeneic and autologous HSCT based on current capabilities within the EBMT registry core dataset. Data completeness, which has a critical impact on validity of centre comparisons, is also assessed. Ongoing development will include further scientific validation of the model, incorporation of further variables (when appropriate) alongside implementation of systems for clinically meaningful interpretation and governance aiming to maximise acceptance to centres, clinicians, payers and patients across EBMT.

Chimeric antigen receptor (CAR) T cells are a novel class of anti-cancer therapy in which autologous or allogeneic T cells are engineered to express a CAR targeting a membrane antigen. In Europe, tisagenlecleucel (Kymriah™) is approved for the treatment of refractory/relapsed acute lymphoblastic leukemia in children and young adults as well as relapsed/refractory diffuse large B-cell lymphoma, while axicabtagene ciloleucel (Yescarta™) is approved for the treatment of relapsed/refractory high-grade B-cell lymphoma and primary mediastinal B-cell lymphoma. Both agents are genetically engineered autologous T cells targeting CD19. These practical recommendations, prepared under the auspices of the European Society of Blood and Marrow Transplantation, relate to patient care and supply chain management under the following headings: patient eligibility, screening laboratory tests and imaging and work-up prior to leukapheresis, how to perform leukapheresis, bridging therapy, lymphodepleting conditioning, product receipt and thawing, infusion of CAR T cells, short-term complications including cytokine release syndrome and immune effector cell-associated neurotoxicity syndrome, antibiotic prophylaxis, medium-term complications including cytopenias and B-cell aplasia, nursing and psychological support for patients, long-term follow-up, post-authorization safety surveillance, and regulatory issues. These recommendations are not prescriptive and are intended as guidance in the use of this novel therapeutic class., (Copyright© 2020 Ferrata Storti Foundation.)

Sclerotic chronic graft vs. host disease (cGVHD) still has a large impact on morbidity and mortality after allogeneic hematopoietic stem cell transplantation (HSCT). We performed the first prospective study to test whether sequential therapy of the anti-CD20 antibody rituximab followed by 6 months treatment with tyrosine kinase inhibitor nilotinib is a favorable treatment strategy for patients with sclerotic cGVHD. Twenty-nine patients were included, 24 were available for analysis. We observed objective responses in 71% of patients (two patients CR, 15 patients PR). Moreover, two out of five patients suffering from severe ulcerations showed complete resolution of ulcers. Observed responses lasted until the end of study follow-up. The majority of responding patients could reduce daily corticosteroid dose with more than 50%. Furthermore, CD5+ B-cells are significantly lower (p = 0.007) in responding patients at baseline, proposing a new biomarker predictive for response. In conclusion, sequential treatment of rituximab followed by nilotinib associates with a very high response rate in this difficult to treat patient population. CD5+ B-cells could assist in guiding treatment choices and might be a first step toward more personalized cGVHD treatment. This trial was registered at the Dutch clinical trial registry as NTR1222.

Hematopoietic cell transplantation (HCT) is an established procedure for acquired and congenital disorders of the hematopoietic system. In 2016, there was a tendency for continued activity in this field with 43,636 HCT in 39,313 patients [16,507 allogeneic (42%), 22,806 autologous (58%)] reported by 679 centers in 49 countries in 2016. The main indications were myeloid malignancies 9547 (24%; 96% allogeneic), lymphoid malignancies 25,618 (65%; 20% allogeneic), solid tumors 1516 (4%; 2% allogeneic), and non-malignant disorders 2459 (6%; 85% allogeneic). There was a remarkable leveling off in the use of unrelated donor HCT being replaced by haploidentical HCT. Continued growth in allogeneic HCT for marrow failure, AML, and MPN was seen, whereas MDS appears stable. Allogeneic HCT for lymphoid malignancies vary in trend with increases for NHL and decreases for Hodgkin lymphoma and myeloma. Trends in CLL are not clear, with recent increases after a decrease in activity. In autologous HCT, the use in myeloma continues to expand but is stable in Hodgkin lymphoma. There is a notable increase in autologous HCT for autoimmune disease. These data reflect the most recent advances in the field, in which some trends and changes are likely to be related to development of non-transplant technologies.

Individuals with acute myeloid leukemia (AML) harboring an internal tandem duplication (ITD) in the gene encoding Fms-related tyrosine kinase 3 (FLT3) who relapse after allogeneic hematopoietic cell transplantation (allo-HCT) have a 1-year survival rate below 20%. We observed that sorafenib, a multitargeted tyrosine kinase inhibitor, increased IL-15 production by FLT3-ITD + leukemia cells. This synergized with the allogeneic CD8 + T cell response, leading to long-term survival in six mouse models of FLT3-ITD + AML. Sorafenib-related IL-15 production caused an increase in CD8 + CD107a + IFN-γ + T cells with features of longevity (high levels of Bcl-2 and reduced PD-1 levels), which eradicated leukemia in secondary recipients. Mechanistically, sorafenib reduced expression of the transcription factor ATF4, thereby blocking negative regulation of interferon regulatory factor 7 (IRF7) activation, which enhanced IL-15 transcription. Both IRF7 knockdown and ATF4 overexpression in leukemia cells antagonized sorafenib-induced IL-15 production in vitro. Human FLT3-ITD + AML cells obtained from sorafenib responders following sorafenib therapy showed increased levels of IL-15, phosphorylated IRF7, and a transcriptionally active IRF7 chromatin state. The mitochondrial spare respiratory capacity and glycolytic capacity of CD8 + T cells increased upon sorafenib treatment in sorafenib responders but not in nonresponders. Our findings indicate that the synergism of T cells and sorafenib is mediated via reduced ATF4 expression, causing activation of the IRF7-IL-15 axis in leukemia cells and thereby leading to metabolic reprogramming of leukemia-reactive T cells in humans. Therefore, sorafenib treatment has the potential to contribute to an immune-mediated cure of FLT3-ITD-mutant AML relapse, an otherwise fatal complication after allo-HCT.

Purpose of Review: The outcome of allogeneic stem cell transplantation (allo-HCT) is still compromised by relapse and complications. NK cells and γδT cells, effectors which both function through MHC-unrestricted mechanisms, can target transformed and infected cells without inducing Graft-versus-Host Disease (GVHD). Allo-HCT platforms based on CD34+ selection or αβ-TCR depletion result in low grades of GVHD, early immune reconstitution (IR) of NK and γδT cells and minimal usage of GVHD prophylaxis. In this review we will discuss strategies to retain and expand the quantity, diversity and functionality of these reconstituting innate cell types., Recent Findings: Bisphosphonates, IL-15 cytokine administration, specific antibodies, checkpoint inhibitors and (CMV based) vaccination are currently being evaluated to enhance IR. All these approaches have shown to potentially enhance both NK and γδT cell immuno-repertoires., Summary: Rapidly accumulating data linking innate biology to proposed clinical immune interventions, will give unique opportunities to unravel shared pathways which determine the Graft-versus-Tumor effects of NK and γδT cells., Competing Interests: Conflict of Interest Moniek A. de Witte has no conflict of interest.

Graft-versus-host disease (GVHD) is among the most challenging complications in unrelated donor hematopoietic cell transplantation (HCT). The highly polymorphic MHC class I chain-related gene A, MICA, encodes a stress-induced glycoprotein expressed primarily on epithelia. MICA interacts with the invariant activating receptor NKG2D, expressed by cytotoxic lymphocytes, and is located in the MHC, next to HLA-B Hence, MICA has the requisite attributes of a bona fide transplantation antigen. Using high-resolution sequence-based genotyping of MICA, we retrospectively analyzed the clinical effect of MICA mismatches in a multicenter cohort of 922 unrelated donor HLA-A, HLA-B, HLA-C, HLA-DRB1, and HLA-DQB1 10/10 allele-matched HCT pairs. Among the 922 pairs, 113 (12.3%) were mismatched in MICA MICA mismatches were significantly associated with an increased incidence of grade III-IV acute GVHD (hazard ratio [HR], 1.83; 95% confidence interval [CI], 1.50-2.23; P < .001), chronic GVHD (HR, 1.50; 95% CI, 1.45-1.55; P < .001), and nonelapse mortality (HR, 1.35; 95% CI, 1.24-1.46; P < .001). The increased risk for GVHD was mirrored by a lower risk for relapse (HR, 0.50; 95% CI, 0.43-0.59; P < .001), indicating a possible graft-versus-leukemia effect. In conclusion, when possible, selecting a MICA-matched donor significantly influences key clinical outcomes of HCT in which a marked reduction of GVHD is paramount. The tight linkage disequilibrium between MICA and HLA-B renders identifying a MICA-matched donor readily feasible in clinical practice., (© 2016 by The American Society of Hematology.)

Adoptive transfer of chimeric antigen receptor-transduced T cells is a promising strategy for cancer immunotherapy. The CD38 molecule, with its high expression on multiple myeloma cells, appears a suitable target for antibody therapy. Prompted by this, we used three different CD38 antibody sequences to generate second-generation retroviral CD38-chimeric antigen receptor constructs with which we transduced T cells from healthy donors and multiple myeloma patients. We then evaluated the preclinical efficacy and safety of the transduced T cells. Irrespective of the donor and antibody sequence, CD38-chimeric antigen receptor-transduced T cells proliferated, produced inflammatory cytokines and effectively lysed malignant cell lines and primary malignant cells from patients with acute myeloid leukemia and multi-drug resistant multiple myeloma in a cell-dose, and CD38-dependent manner, despite becoming CD38-negative during culture. CD38-chimeric antigen receptor-transduced T cells also displayed significant anti-tumor effects in a xenotransplant model, in which multiple myeloma tumors were grown in a human bone marrow-like microenvironment. CD38-chimeric antigen receptor-transduced T cells also appeared to lyse the CD38(+) fractions of CD34(+) hematopoietic progenitor cells, monocytes, natural killer cells, and to a lesser extent T and B cells but did not inhibit the outgrowth of progenitor cells into various myeloid lineages and, furthermore, were effectively controllable with a caspase-9-based suicide gene. These results signify the potential importance of CD38-chimeric antigen receptor-transduced T cells as therapeutic tools for CD38(+) malignancies and warrant further efforts to diminish the undesired effects of this immunotherapy using appropriate strategies., (Copyright© Ferrata Storti Foundation.)

Over half a century ago, the first allogeneic stem cell transplantation (allo-SCT) initiated cellular immunotherapy. For several decades, little progress was made, and toxicity of allo-SCT remained a major challenge. However, recent breakthroughs have opened new avenues to further develop this modality and to provide less toxic and equally efficient interventions for patients suffering from hematological or solid malignancies. Current novel cellular immune interventions include ex vivo expansion and adoptive transfer of tumor-infiltrating immune cells or administration of drugs which antagonize tolerizing mechanisms. Alternatively, transfer of immune cells engineered to express defined T cell receptors (TCRs) and chimeric antigen receptors (CARs) has shown its potential. A valuable addition to 'engineered' adaptive immunity has emerged recently through the improved understanding of how innate immune cells can attack cancer cells without substantial side effects. This has enabled the development of transplantation platforms with limited side effects allowing early immune interventions as well as the design of engineered immune cells expressing innate immune receptors. Here, we focus on innate immune interventions and their orchestration with TCR- and CAR-engineered immune cells. In addition, we discuss how the exploitation of the full potential of cellular immune interventions is influenced by regulatory frameworks. Finally, we highlight and discuss substantial differences in the current landscape of clinical trials in Europe as compared to the USA. The aim is to stimulate international efforts to support regulatory authorities and funding agencies, especially in Europe, to create an environment that will endorse the development of engineered immune cells for the benefit of patients.

Acquired chromosomal abnormalities are important prognostic factors in patients with myelodysplastic syndromes treated with supportive care and with disease-modifying therapeutic interventions, including allogeneic hematopoietic stem cell transplantation. To assess the prognostic impact of cytogenetic characteristics after hematopoietic stem cell transplantation accurately, we investigated a homogeneous group of 523 patients with primary myelodysplastic syndromes who have received stem cells from human leukocyte antigen-identical siblings. Overall survival at five years from transplantation in good, intermediate, and poor cytogenetic risk groups according to the International Prognostic Scoring System was 48%, 45% and 30%, respectively (P<0.01). Both the disease status (complete remission vs. not in complete remission) and the morphological classification at transplant in the untreated patients were significantly associated with probability of overall survival and relapse-free survival (P<0.01). The cytogenetic risk groups have no prognostic impact in untreated patients with refractory anemia ± ringed sideroblasts (P=0.90). However, combining the good and intermediate cytogenetic risk groups and comparing them to the poor-risk group showed within the other three disease-status-at-transplant groups a hazard ratio of 1.86 (95%CI: 1.41-2.45). In conclusion, this study shows that, in a large series of patients with primary myelodysplastic syndromes, poor-risk cytogenetics as defined by the standard International Prognostic Scoring System is associated with a relatively poor survival after allogeneic stem cell transplantation from human leukocyte antigen-identical siblings except in patients who are transplanted in refractory anemia/refractory anemia with ringed sideroblasts stage before progression to higher myelodysplastic syndrome stages., (Copyright© Ferrata Storti Foundation.)

Because information on management and outcome of AML relapse after allogeneic hematopoietic stem cell transplantation (HSCT) with reduced intensity conditioning (RIC) is scarce, a retrospective registry study was performed by the Acute Leukemia Working Party of EBMT. Among 2815 RIC transplants performed for AML in complete remission (CR) between 1999 and 2008, cumulative incidence of relapse was 32% ± 1%. Relapsed patients (263) were included into a detailed analysis of risk factors for overall survival (OS) and building of a prognostic score. CR was reinduced in 32%; remission duration after transplantation was the only prognostic factor for response (P = .003). Estimated 2-year OS from relapse was 14%, thereby resembling results of AML relapse after standard conditioning. Among variables available at the time of relapse, remission after HSCT > 5 months (hazard ratio [HR] = 0.50, 95% confidence interval [CI], 0.37-0.67, P < .001), bone marrow blasts less than 27% (HR = 0.53, 95% CI, 0.40-0.72, P < .001), and absence of acute GVHD after HSCT (HR = 0.67, 95% CI, 0.49-0.93, P = .017) were associated with better OS. Based on these factors, 3 prognostic groups could be discriminated, showing OS of 32% ± 7%, 19% ± 4%, and 4% ± 2% at 2 years (P < .0001). Long-term survival was achieved almost exclusively after successful induction of CR by cytoreductive therapy, followed either by donor lymphocyte infusion or second HSCT for consolidation.

Chronic graft-versus-host disease is the major long-term complication after allogeneic stem cell transplantation with a suboptimal response rate to current treatments. Therefore, clinical efficacy and changes in lymphocyte subsets before and after rituximab treatment were evaluated in a prospective phase II study in patients with steroid-refractory chronic graft-versus-host disease. Overall response rate was 61%. Only responding patients were found to have increased B-cell numbers prior to treatment. B cells had a naïve-antigen-presenting phenotype and were mainly CD5 negative or had a low CD5 expression. Normal B-cell homeostasis was reestablished in responding patients one year after ritxumab treatment and associated with a significant decline in skin-infiltrating CD8(+) T cells, suggesting that host B cells play a role in maintaining pathological CD8(+) T-cell responses. Imbalances in B-cell homeostasis could be used to identify patients a priori with a higher chance of response to rituximab treatment (Eudra-CT 2008-004125-42).

Major limitations of currently investigated αβT cells redirected against cancer by transfer of tumor-specific αβTCR arise from their low affinity, MHC restriction, and risk to mediate self-reactivity after pairing with endogenous α or βTCR chains. Therefore, the ability of a defined γ9δ2TCR to redirect αβT cells selectively against tumor cells was tested and its molecular interaction with a variety of targets investigated. Functional analysis revealed that a γ9δ2TCR efficiently reprograms both CD4(+) and CD8(+) αβT cells against a broad panel of cancer cells while ignoring normal cells, and substantially reduces but does not completely abrogate alloreactivity. γ9δ2TCR-transduced αβT cells reduced colony formation of progenitor cells of primary acute myeloid leukemia blasts and inhibited leukemia growth in a humanized mouse model. Thereby, metabolites of a dysregulated mevalonate pathway are targeted and the additional application of widely used biphosphonates is crucial for in vivo efficacy most likely because of its modulating effect on cytokine secretion of γ9δ2TCR-transduced αβT cells. Expression of NKG2D ligands and F1-ATPase contributed to the activity of γ9δ2TCR-transduced αβT cells but were not mandatory. In summary, γ9δ2 TCRs are an attractive alternative to broadly redirect αβT cells against cancer cells with both an improved efficacy and safety profile compared with currently used αβTCRs.

Reprogramming T-cell populations by T-cell receptor (TCR) gene transfer is a new therapeutic tool for adoptive tumor immunotherapy. Gene transfer of human leukocyte antigen (HLA)-transgenic mice-derived TCR into human T-cells allows the circumvention of tolerance to tumor-associated (self) antigens (TAA). This chapter reports on the identification of the alpha and beta chains of the heterodimeric TCR derived from a mouse T-cell clone. The related DNA fragments are inserted into a retroviral vector for heterologous expression of the TAA-specific TCR in human T-cells. Polymerase chain reaction (PCR)-based cloning protocols are provided for the tailor-made customization of murine TCR. We describe the humanization and chimerization of such TCR as well as their expression in human T-cells.