Identification of a robust DNA methylation signature for Fanconi anemia.

Fanconi anemia (FA) is a clinically variable and genetically heterogeneous cancer-predisposing disorder representing the most common bone marrow failure syndrome. It is caused by inactivating predominantly biallelic mutations involving >20 genes encoding proteins with roles in the FA/BRCA DNA repair pathway. Molecular diagnosis of FA is challenging due to the wide spectrum of the contributing gene mutations and structural rearrangements. The assessment of chromosomal fragility after exposure to DNA cross-linking agents is generally required to definitively confirm diagnosis. We assessed peripheral blood genome-wide DNA methylation (DNAm) profiles in 25 subjects with molecularly confirmed clinical diagnosis of FA (FANCA complementation group) using Illumina's Infinium EPIC array. We identified 82 differentially methylated CpG sites that allow to distinguish subjects with FA from healthy individuals and subjects with other genetic disorders, defining an FA-specific DNAm signature. The episignature was validated using a second cohort of subjects with FA involving different complementation groups, documenting broader genetic sensitivity and demonstrating its specificity using the EpiSign Knowledge Database. The episignature properly classified DNA samples obtained from bone marrow aspirates, demonstrating robustness. Using the selected probes, we trained a machine-learning model able to classify EPIC DNAm profiles in molecularly unsolved cases. Finally, we show that the generated episignature includes CpG sites that do not undergo functional selective pressure, allowing diagnosis of FA in individuals with reverted phenotype due to gene conversion. These findings provide a tool to accelerate diagnostic testing in FA and broaden the clinical utility of DNAm profiling in the diagnostic setting.

GD2-CART01 for Relapsed or Refractory High-Risk Neuroblastoma.

BACKGROUND: Immunotherapy with chimeric antigen receptor (CAR)-expressing T cells that target the disialoganglioside GD2 expressed on tumor cells may be a therapeutic option for patients with high-risk neuroblastoma. METHODS: In an academic, phase 1-2 clinical trial, we enrolled patients (1 to 25 years of age) with relapsed or refractory, high-risk neuroblastoma in order to test autologous, third-generation GD2-CAR T cells expressing the inducible caspase 9 suicide gene (GD2-CART01). RESULTS: A total of 27 children with heavily pretreated neuroblastoma (12 with refractory disease, 14 with relapsed disease, and 1 with a complete response at the end of first-line therapy) were enrolled and received GD2-CART01. No failure to generate GD2-CART01 was observed. Three dose levels were tested (3-, 6-, and 10×106 CAR-positive T cells per kilogram of body weight) in the phase 1 portion of the trial, and no dose-limiting toxic effects were recorded; the recommended dose for the phase 2 portion of the trial was 10×106 CAR-positive T cells per kilogram. Cytokine release syndrome occurred in 20 of 27 patients (74%) and was mild in 19 of 20 (95%). In 1 patient, the suicide gene was activated, with rapid elimination of GD2-CART01. GD2-targeted CAR T cells expanded in vivo and were detectable in peripheral blood in 26 of 27 patients up to 30 months after infusion (median persistence, 3 months; range, 1 to 30). Seventeen children had a response to the treatment (overall response, 63%); 9 patients had a complete response, and 8 had a partial response. Among the patients who received the recommended dose, the 3-year overall survival and event-free survival were 60% and 36%, respectively. CONCLUSIONS: The use of GD2-CART01 was feasible and safe in treating high-risk neuroblastoma. Treatment-related toxic effects developed, and the activation of the suicide gene controlled side effects. GD2-CART01 may have a sustained antitumor effect. (Funded by the Italian Medicines Agency and others; ClinicalTrials.gov number, NCT03373097.).

TCRαß/CD19 cell-depleted HLA-haploidentical transplantation to treat pediatric acute leukemia: updated final analysis.

ABSTRACT: TCRαß/CD19 cell depletion is a promising graft manipulation technique frequently used in the context of human leukocyte antigen (HLA)-haploidentical hematopoietic stem cell transplantation (HSCT). We previously reported the results of a phase I-II clinical trial (NCT01810120) to assess the safety and the efficacy of this type of exvivo T-cell depletion in 80 children with acute leukemia, showing promising survival outcomes. We now report an updated analysis on a cohort of 213 children with a longer follow-up (median, 47.6 months for surviving patients). With a 5-year cumulative incidence of nonrelapse mortality of 5.2% (95% confidence interval [CI], 2.8%-8.8%) and a cumulative incidence of relapse of 22.7% (95% CI, 16.9%-29.2%), projected 10-year overall and disease-free survival (DFS) were 75.4% (95% CI, 68.6%-80.9%) and 71.6% (95% CI, 64.4%-77.6%), respectively. Cumulative incidence of both grade II-IV acute and chronic graft-versus-host disease were low (14.7% and 8.1%, respectively). In a multivariable analysis for DFS including type of disease, use of total body irradiation in the conditioning regimen (hazard ratio [HR], 0.5; 95% CI, 0.26-0.98; P = .04), disease status at HSCT (complete remission [CR] ≥3 vs CR 1/2; HR, 2.23; 95% CI, 1.20-4.16; P = .01), and high levels of pre-HSCT minimal residual disease (HR, 2.09; 95% CI, 1.01-4.33; P = .04) were independently associated with outcome. In summary, besides confirming the good outcome results already reported (which are almost superimposable on those of transplant from HLA-matched donors), this clinical update allows the identification of patients at higher risk of treatment failure for whom personalized approaches, aimed at reducing the risk of relapse, are warranted.

Allogeneic, donor-derived, second-generation, CD19-directed CAR-T cells for the treatment of pediatric relapsed/refractory BCP-ALL.

Autologous CD19-directed chimeric antigen receptor (CAR)-T cells have shown unprecedented efficacy in children with relapsed/refractory B-cell precursor acute lymphoblastic leukemia (BCP-ALL). However, patients either relapsing after allogeneic hematopoietic stem cell transplantation (allo-HSCT) or displaying profound lymphopenia and/or rapidly progressing disease often cannot access autologous products. These hurdles may be overcome by allogeneic, donor-derived CAR-T cells. We tested donor-derived T cells transduced with a second-generation (4.1BB) CD19-directed CAR for treatment of patients with BCP-ALL in a hospital-exemption setting. Two constructs were tested: a retroviral construct incorporating the suicide gene inducible caspase-9 (CD19-CAR-Retro_ALLO) first and then a lentiviral construct and an automated, Prodigy-based manufacturing process (CD19-CAR-Lenti_ALLO). Thirteen children/young adults received ALLO-CAR-T cells between March 2021 and October 2022. Doses ranged between 1.0 × 106 and 3.0 × 106 CAR-T cells per kg. The toxicity profile was comparable with that of autologous CAR-T cells, characterized mainly by cytopenia, cytokine release syndrome (maximum grade 1), and grade 2 immune-effector cell-associated neurotoxicity syndrome. One case of acute graft-versus-host disease (GVHD) occurred and was rapidly controlled with steroids and ruxolitinib. None of the other patients, including 3 given ALLO-CAR-T cells from an HLA-haploidentical donor, experienced GVHD. Two patients received ALLO-CAR-T cells before HSCT and showed a significant expansion of CAR-T cells without any sign of GVHD. All patients obtained complete remission (CR) with absence of minimal residual disease in the bone marrow. With a median follow-up of 12 months (range, 5-21), 8 of 13 patients maintained CR. Allogeneic anti-CD19 CAR-T cells can effectively treat highly refractory BCP-ALL relapsing after allo-HSCT without showing increased toxicity as compared with autologous CAR-T cells.

Mucosal-associated invariant T cells are functionally impaired in pediatric and young adult patients following allogeneic hematopoietic stem cell transplantation and their recovery correlates with clinical outcomes.

Mucosal-associated invariant T (MAIT) cells are innate-like T cells implicated in the response to fungal and bacterial infections. Their contribution to restoring T-cell immunity and influencing hematopoietic stem cell transplant (HSCT) outcomes remains poorly understood. We retrospectively studied MAIT-cell recovery in 145 consecutive children and young adults with hematologic malignancies undergoing allogeneic (allo)-HSCT between April 2019 and May 2022, from unrelated matched donor (MUD, N=52), with standard graft-versus-host-disease (GvHD) prophylaxis, or HLA-haploidentical (Haplo, N=93) donor after in vitro αßT/CD19-cell depletion, without post-HSCT pharmacological prophylaxis. With a median follow-up of 33 months (range, 12-49 months), overall survival (OS), disease-free survival (DFS), and non-relapse mortality (NRM) were 79.5%, 72%, and 7%, respectively; GvHD-free relapse-free survival (GRFS) was 63%, while cumulative incidence of relapse was 23%. While αßT cells were reconstituted 1-2 years post HSCT, MAIT cells showed delayed recovery and prolonged functional impairment, characterized by expression of activation (CD25, CD38), exhaustion (PD1, TIM3) and senescence (CD57) markers, and suboptimal ex vivo response. OS, DFS, and NRM were not affected by MAIT cells. Interestingly, higher MAIT cells at day +30 correlated with higher incidence of grade II-IV acute GvHD (19% vs. 7%, P=0.06). Furthermore, a greater MAIT-cell count tended to be associated with a higher incidence of chronic GvHD (cGvHD) (17% vs. 6%, P=0.07) resulting in lower GRFS (55% vs. 73%, P=0.05). Higher MAIT cells also correlated with greater cytomegalovirus (CMV) reactivation and lower late blood stream infections (BSI) (44% vs. 24%, P=0.02 and 9% vs. 18%, P=0.08, respectively). Future studies are needed to confirm the impact of early MAIT-cell recovery on cGvHD, CMV reactivation, and late BSI.

Outcomes of children and young adults with B-cell acute lymphoblastic leukemia given blinatumomab as last consolidation treatment before allogeneic hematopoietic stem cell transplantation.

Blinatumomab has remarkable efficacy in patients with relapsed/refractory (r/r) or measurable residual disease (MRD)-positive B-cell acute lymphoblastic leukemia (B-ALL). In many patients, blinatumomab treatment is followed by allogeneic hematopoietic stem cell transplantation (HSCT). However, the influence of blinatumomab on HSCT outcomes in children and young adults (YA) remains to be fully elucidated. We conducted a single-center, retrospective analysis on patients given blinatumomab as last treatment before HSCT. Seventy-eight pediatric and YA patients were evaluated. With a median follow-up of 23.23 months, the 2-year disease-free (DFS) and overall survival (OS) probability were 72.2% and 89.2%, respectively, with a 2-year cumulative incidence (CI) of non-relapse mortality (NRM) of 2.6%. A trend toward improved 2-year DFS, but not OS, was noted in patients transplanted in first complete remission (CR1) (92.9%) compared to those in second or greater remission (CR2/3) (68.5%, p=0.18) due to a lower CI of relapse (0% vs. 29.9%, p=0.05). Among CR2/3 patients, those receiving the sequential combination of inotuzumab and blinatumomab had a significantly lower CI of relapse as compared to those who did not receive inotuzumab (9.5% vs. 40.4%, p=0.023). Relapse after HSCT occurred in 16 patients, all exhibiting CD19-positive blasts; 10 of them received anti-CD19 chimeric antigen receptor T-cell (CAR-T) therapy and 2 inotuzumab as salvage therapy, leading to a 2-year post-relapse OS of 52.7%. Our results indicate that HSCT following blinatumomab in children and YA with B-ALL is highly effective, being associated with low NRM and not affecting the efficacy of subsequent salvage immunotherapies, including CAR-T cells.

Human leukocyte antigen evolutionary divergence influences outcomes of paediatric patients and young adults affected by malignant disorders given allogeneic haematopoietic stem cell transplantation from unrelated donors.

High genetic heterogeneity in the human leukocyte antigen (HLA) increases the likelihood of efficient immune response to pathogens and tumours. As measure of HLA diversity, HLA evolutionary divergence (HED) has been shown to predict the response of tumours to immunotherapy and haematopoietic stem cell transplantation (HSCT) in adults. We retrospectively investigated the association of HED with outcomes of 153 paediatric/young adults patients, treated for malignant disorders with HSCT from 9-10/10 HLA-matched unrelated donors. HED was calculated as pairwise genetic distance between alleles in patient HLA-A, -B, -C, -DRB1, -DQB1 and -DPB1, using the locus median to stratify patients with 'high' or 'low' HED. Patients with high HED-B and -DRB1 showed significantly improved disease-free survival (DFS), especially when combined (70.8% vs 53.7% p = 0.008). High HED-B + -DRB1 was also associated with improved overall survival (OS) (82.1 vs 66.4% p = 0.014), and concomitant reduction of non-relapse-mortality (5.1% vs 21.1% p = 0.006). The impact on OS and DFS of combined HED-B + -DRB1 was confirmed in multivariate analysis [hazard ratio (HR) 0.39, p = 0.009; and HR 0.45, p = 0.007 respectively]. Only high HED scores for HLA-DPB1 were associated, in univariate analysis, with reduced incidence of relapse (15.9% vs 31.1%, p = 0.03). These results support HED as prognostic marker in allogeneic HSCT and, if confirmed in larger cohorts, would allow its use to inform clinical risk and potentially influence clinical practice.

Comprehensive phenotyping of human peripheral blood B lymphocytes in pathological conditions.

Several diseases are associated with alterations of the B-cell compartment. Knowing how to correctly identify by flow cytometry the distribution of B-cell populations in the peripheral blood is important to help in the early diagnosis. In the accompanying article we describe how to identify the different B-cell subsets in the peripheral blood of healthy donors. Here we show a few examples of diseases that cause dysregulation of the B-cell compartment.

Brentuximab vedotin in combination with bendamustine in pediatric patients or young adults with relapsed or refractory Hodgkin lymphoma.

Although children and young adults with Hodgkin's lymphoma usually have a favorable prognosis, patients with primary refractory disease and some subsets of relapsed patients still have a dismal outcome. Brentuximab vedotin (BV) in combination with bendamustine may represent a suitable salvage therapy; data on 32 patients aged less than 25 years were retrospectively analyzed. Patients received up to six cycles of treatment of BV 1.8 mg/kg on day 1 and bendamustine 90-120 mg/m2 on days 2 and 3. At the end of treatment, the overall response rate was 81%. The 3-year overall and progression-free survivals are 78.1% and 67%, respectively.

Haplo-identical or mismatched unrelated donor hematopoietic cell transplantation for Fanconi anemia: Results from the Severe Aplastic Anemia Working Party of the EBMT.

Allogeneic hematopoietic cell transplantation (HCT) is the only curative option for bone marrow failure or hematopoietic malignant diseases for Fanconi anemia (FA) patients. Although results have improved over the last decades, reaching more than 90% survival when a human leukocyte antigen (HLA)-identical donor is available, alternative HCT donors are still less reported. We compared HCT outcomes using HLA-mismatched unrelated donors (MMUD; n = 123) or haplo-identical donors (HDs), either using only in vivo T cell depletion (n = 33) or T cells depleted in vivo with some type of graft manipulation ex vivo (n = 59) performed for FA between 2000 and 2018. Overall survival (OS) by 24 months was 62% (53-71%) for MMUD, versus 80% (66-95%) for HDs with only in vivo T cell depletion and 60% (47-73%) for HDs with in vivo and ex vivo T cell depletion (p = .22). Event-free survival (EFS) was better for HD-transplanted FA patients with only in vivo T cell depletion 86% (73-99%) than for those transplanted from a MMUD 58% (48-68%) or those with graft manipulation 56% (42-69%) (p = .046). Grade II-IV acute graft-versus-host disease (GVHD) was 41% (MMUD) versus 40% (HDs with no graft manipulation) versus 17% (HDs with T cell depleted graft), (p = .005). No differences were found for the other transplant related outcomes. These data suggest that HDs might be considered as an alternative option for FA patients with better EFS using unmanipulated grafts.

Unrelated donor vs HLA-haploidentical α/ß T-cell- and B-cell-depleted HSCT in children with acute leukemia.

Traditionally, hematopoietic stem cell transplantation (HSCT) from both HLA-matched related and unrelated donors (UD) has been used for treating children with acute leukemia (AL) in need of an allograft. Recently, HLA-haploidentical HSCT after αß T-cell/B-cell depletion (αßhaplo-HSCT) was shown to be effective in single-center studies. Here, we report the first multicenter retrospective analysis of 127 matched UD (MUD), 118 mismatched UD (MMUD), and 98 αßhaplo-HSCT recipients, transplanted between 2010 and 2015, in 13 Italian centers. All these AL children were transplanted in morphological remission after a myeloablative conditioning regimen. Graft failure occurred in 2% each of UD-HSCT and αßhaplo-HSCT groups. In MUD vs MMUD-HSCT recipients, the cumulative incidence of grade II to IV and grade III to IV acute graft-versus-host disease (GVHD) was 35% vs 44% and 6% vs 18%, respectively, compared with 16% and 0% in αßhaplo-HSCT recipients (P < .001). Children treated with αßhaplo-HSCT also had a significantly lower incidence of overall and extensive chronic GVHD (P < .01). Eight (6%) MUD, 32 (28%) MMUD, and 9 (9%) αßhaplo-HSCT patients died of transplant-related complications. With a median follow-up of 3.3 years, the 5-year probability of leukemia-free survival in the 3 groups was 67%, 55%, and 62%, respectively. In the 3 groups, chronic GVHD-free/relapse-free (GRFS) probability of survival was 61%, 34%, and 58%, respectively (P < .001). When compared with patients given MMUD-HSCT, αßhaplo-HSCT recipients had a lower cumulative incidence of nonrelapse mortality and a better GRFS (P < .001). These data indicate that αßhaplo-HSCT is a suitable therapeutic option for children with AL in need of transplantation, especially when an allele-matched UD is not available.

Outcome of children with acute leukemia given HLA-haploidentical HSCT after αß T-cell and B-cell depletion.

Allogeneic hematopoietic stem cell transplantation (HSCT) from an HLA-haploidentical relative (haplo-HSCT) is a suitable option for children with acute leukemia (AL) either relapsed or at high-risk of treatment failure. We developed a novel method of graft manipulation based on negative depletion of αß T and B cells and conducted a prospective trial evaluating the outcome of children with AL transplanted with this approach. Eighty AL children, transplanted between September 2011 and September 2014, were enrolled in the trial. All children were given a fully myeloablative preparative regimen. Anti-T-lymphocyte globulin from day -5 to -3 was used for preventing graft rejection and graft-versus-host disease (GVHD); no patient received any posttransplantation GVHD prophylaxis. Two children experienced primary graft failure. The cumulative incidence of skin-only, grade 1-2 acute GVHD was 30%; no patient developed extensive chronic GVHD. Four patients died, the cumulative incidence of nonrelapse mortality being 5%, whereas 19 relapsed, resulting in a 24% cumulative incidence of relapse. With a median follow-up of 46 months for surviving patients, the 5-year probability of chronic GVHD-free, relapse-free survival (GRFS) is 71%. Total body irradiation-containing preparative regimen was the only variable favorably influencing relapse incidence and GRFS. The outcomes of these 80 patients are comparable to those of 41 and 51 children given transplantation from an HLA-identical sibling or a 10/10 allelic-matched unrelated donor in the same period. These data indicate that haplo-HSCT after αß T- and B-cell depletion represents a competitive alternative for children with AL in need of urgent allograft. This trial was registered at www.clinicaltrials.gov as #NCT01810120.

Role of interferon-γ in immune-mediated graft failure after allogeneic hematopoietic stem cell transplantation.

Pathophysiology of graft failure (GF) occurring after allogeneic hematopoietic stem cell transplantation (HSCT) still remains elusive. We measured serum levels of several different cytokines/chemokines in 15 children experiencing GF, comparing their values with those of 15 controls who had sustained donor cell engraftment. Already at day +3 after transplantation, patients developing GF had serum levels of interferon (IFN)-γ and CXCL9 (a chemokine specifically induced by IFNγ) significantly higher than those of controls (8859±7502 vs. 0 pg/mL, P=0.03, and 1514.0±773 vs. 233.6±50.1 pg/mlL, P=0.0006, respectively). The role played by IFNγ in HSCT-related GF was further supported by the observation that a rat anti-mouse IFNγ-neutralizing monoclonal antibody promotes donor cell engraftment in Ifngr1-/-mice receiving an allograft. In comparison to controls, analysis of bone marrow-infiltrating T lymphocytes in patients experiencing GF documented a predominance of effector memory CD8+ cells, which showed markers of activation (overexpression of CD95 and downregulation of CD127) and exhaustion (CD57, CD279, CD223 and CD366). Finally, we obtained successful donor engraftment in 2 out of 3 children with primary hemophagocytic lymphohistiocytosis who, after experiencing GF, were re-transplanted from the same HLA-haploidentical donor under the compassionate use coverage of emapalumab, an anti-IFNγ monoclonal antibody recently approved by the US Food and Drug Administration for treatment of patients with primary hemophagocytic lymphohistiocytosis. Altogether, these results suggest that the IFNγ pathway plays a major role in GF occurring after HSCT. Increased serum levels of IFNγ and CXCL9 represent potential biomarkers useful for early diagnosis of GF and provide the rationale for exploring the therapeutic/preventive role of targeted neutralization of IFNγ.

Efficacy of two different doses of rabbit anti-T-lymphocyte globulin to prevent graft-versus-host disease in children with haematological malignancies transplanted from an unrelated donor: a multicentre, randomised, open-label, phase 3 trial.

BACKGROUND: Although rabbit anti-T-lymphocyte globulin (ATLG) is largely used for the prevention of immune-mediated complications in patients given allogeneic haemopoietic stem-cell transplantation (HSCT) from an unrelated donor, the optimum dose of this drug in children is still undefined. We aimed to test whether a higher dose of ATLG was superior to a lower dose for prevention of grade II-IV acute graft-versus-host disease (GVHD). METHODS: We conducted a multicentre, randomised, open-label, phase 3 trial in seven Italian centres comparing two different doses of ATLG (30 mg/kg vs 15 mg/kg, given intravenously over 3 days, from day -4 to -2) in children (aged 0-18 years) with haematological malignancies transplanted from an unrelated donor, selected using high-resolution typing for HLA-class I/II loci. All patients received a myeloablative regimen and cyclosporine-A plus short-term methotrexate as post-transplantation GVHD prophylaxis. Patients were randomly assigned (1:1) to either of the two groups and were stratified by the degree of HLA-compatibility with their donor, the source of haemopoietic stem cells used (bone marrow vs peripheral blood stem cells), and the disease risk category. The randomisation was open label; all investigators were aware of the treatment allocation. The primary endpoint of the study was 100-day cumulative incidence of grade II-IV acute GVHD. Statistical analyses were done according to the per-protocol principle. Other outcomes included cumulative incidence of chronic GVHD, non-relapse mortality, disease recurrence, and probability of overall survival and event-free survival. This study was registered with ClinicalTrials.gov, number NCT00934557. FINDINGS: Between Jan 15, 2008, and Sept 25, 2012, 89 patients were randomly assigned to the 30 mg/kg ATLG group and 91 to the 15 mg/kg ATLG group; 84 patients in the 30 mg/kg ATLG group and 88 in the 15 mg/kg ATLG group were included in the analysis. The median follow-up for the whole study population was 3·4 years (IQR 1·7-5·1). The 100-day cumulative incidence of grade II-IV acute GVHD was 36% (95% CI 28-48) in the 15 mg/kg ATLG group and 29% (20-40) in the 30 mg/kg ATLG group (hazard ratio [HR] 0·74, 95% CI 0·44-1·25; p=0·26). The cumulative incidence of non-relapse mortality was 9% (5-18) in the 15 mg/kg ATLG group and 19% (12-30) in the 30 mg/kg ATLG group (HR 2·08, 0·89-4·96; p=0·092). Cumulative incidence of disease recurrence was 15% (12-24): 14% (8-23) in the 15 mg/kg ATLG group versus 20% (13-31) in the 30 mg/kg ATLG group (HR 1·54, 0·74-3·21; p=0·25). The 5-year overall survival probability was 70% (62-77) for the whole study population: 78% (69-87) in the 15 mg/kg ATLG group versus 62% (50-73) in the 30 mg/kg ATLG group (HR 1·80, 1·01-3·20; p=0·045). The 5-year event-free survival was 77% for children in the 15 mg/kg ATLG group versus 61% in the 30 mg/kg ATLG group (HR 1·87, 1·07-3·28; p=0·028). INTERPRETATION: Children with haematological malignancies transplanted from unrelated donors selected through high-resolution HLA-typing benefit from the use of a 15 mg/kg ATLG dose in comparison with a 30 mg/kg ATLG dose. ATLG at 15 mg/kg should thus be regarded as the standard serotherapy regimen for unrelated donor allogeneic HSCT in this patient population. Future randomised studies will continue to aim to optimise patient outcome and strategies to prevent acute GVHD occurrence. FUNDING: Fresenius/Neovii Biotech.

γδ T-cell reconstitution after HLA-haploidentical hematopoietic transplantation depleted of TCR-αß+/CD19+ lymphocytes.

We prospectively assessed functional and phenotypic characteristics of γδ T lymphocytes up to 7 months after HLA-haploidentical hematopoietic stem cell transplantation (haplo-HSCT) depleted of αß(+) T cells and CD19(+) B cells in 27 children with either malignant or nonmalignant disorders. We demonstrate that (1) γδ T cells are the predominant T-cell population in patients during the first weeks after transplantation, being mainly, albeit not only, derived from cells infused with the graft and expanding in vivo; (2) central-memory cells predominated very early posttransplantation for both Vδ1 and Vδ2 subsets; (3) Vδ1 cells are specifically expanded in patients experiencing cytomegalovirus reactivation and are more cytotoxic compared with those of children who did not experience reactivation; (4) these subsets display a cytotoxic phenotype and degranulate when challenged with primary acute myeloid and lymphoid leukemia blasts; and (5) Vδ2 cells are expanded in vitro after exposure to zoledronic acid (ZOL) and efficiently lyse primary lymphoid and myeloid blasts. This is the first detailed characterization of γδ T cells emerging in peripheral blood of children after CD19(+) B-cell and αß(+) T-cell-depleted haplo-HSCT. Our results can be instrumental to the development of clinical trials using ZOL for improving γδ T-cell killing capacity against leukemia cells. This trial was registered at www.clinicaltrials.gov as #NCT01810120.

Selective Depletion of αß T Cells and B Cells for Human Leukocyte Antigen-Haploidentical Hematopoietic Stem Cell Transplantation. A Three-Year Follow-Up of Procedure Efficiency.

HLA-haploidentical family donors represent a valuable option for children requiring allogeneic hematopoietic stem cell transplantation (HSCT). Because graft-versus-host diseases (GVHD) is a major complication of HLA-haploidentical HSCT because of alloreactive T cells in the graft, different methods have been used for ex vivo T cell depletion. Removal of donor αß T cells, the subset responsible for GVHD, and of B cells, responsible for post-transplantation lymphoproliferative disorders, have been recently developed for HLA-haploidentical HSCT. This manipulation preserves, in addition to CD34+ progenitors, natural killer, γδ T, and monocytes/dendritic cells, contributing to anti-leukemia activity and protection against infections. We analyzed depletion efficiency and cell yield in 200 procedures performed in the last 3 years at our center. Donors underwent CD34+ hematopoietic stem cell (HSC) peripheral blood mobilization with granulocyte colony-stimulating factor (G-CSF). Poor CD34+ cell mobilizers (48 of 189, 25%) received plerixafor in addition to G-CSF. Aphereses containing a median of 52.5 × 109 nucleated cells and 494 × 106 CD34+ HSC were manipulated using the CliniMACS device. In comparison to the initial product, αß T cell depletion produced a median 4.1-log reduction (range, 3.1 to 5.5) and B cell depletion led to a median 3.4-log reduction (range, 2.0 to 4.7). Graft products contained a median of 18.5 × 106 CD34+ HSC/kg recipient body weight, with median values of residual αß T cells and B cells of 29 × 103/kg and 33 × 103/kg, respectively. Depletion efficiency monitored at 6-month intervals demonstrated steady performance, while improved recovery of CD34+ cells was observed after the first year (P = .0005). These data indicate that αß T cell and B cell depletion of HSC grafts from HLA-haploidentical donors was efficient and reproducible.

HLA-haploidentical stem cell transplantation after removal of αß+ T and B cells in children with nonmalignant disorders.

Twenty-three children with nonmalignant disorders received HLA-haploidentical hematopoietic stem cell transplantation (haplo-HSCT) after ex vivo elimination of αß(+) T cells and CD19(+) B cells. The median number of CD34(+), αß(+)CD3(+), and B cells infused was 16.8 × 10(6), 40 × 10(3), and 40 × 10(3) cells/kg, respectively. No patient received any posttransplantation pharmacologic prophylaxis for graft-versus-host disease (GVHD). All but 4 patients engrafted, these latter being rescued by a second allograft. Three patients experienced skin-only grade 1 to 2 acute GVHD. No patient developed visceral acute or chronic GVHD. Cumulative incidence of transplantation-related mortality was 9.3%. With a median follow-up of 18 months, 21 of 23 children are alive and disease-free, the 2-year probability of disease-free survival being 91.1%. Recovery of γδ(+) T cells was prompt, but αß(+) T cells progressively ensued over time. Our data suggest that this novel graft manipulation strategy is safe and effective for haplo-HSCT. This trial was registered at www.clinicaltrials.gov as #NCT01810120.

A novel flow cytometry-based platelet aggregation assay.

The main function of platelets is to maintain normal hemostasis. Inefficient platelet production and/or defective platelet function results in bleeding disorders resulting from a wide range of genetic traits and acquired pathologies. Several platelet function tests have been developed for use in the clinic and in experimental animal models. In particular, platelet aggregation is routinely measured in an aggregometer, which requires normal platelet counts and significant blood sample volumes. For this reason, the analysis of thrombocytopenic patients, infants, and animal models is problematic. We have developed a novel flow cytometry test of platelet aggregation, in which 10- to 25-fold lower platelet counts or sample volumes can be used, either of platelet-rich plasma or whole blood from human subjects or mice. This setup can be applied to test in small assay volumes the influence of a variety of stimuli, drugs, and plasma factors, such as antibodies, on platelet aggregation. The presented principle stands as a novel promising tool, which allows analysis of platelet aggregation in thrombocytopenic patients or infants, and facilitates studies in platelets obtained from experimental animal models without the need of special devices but a flow cytometer.