Hematopoietic stem cell transplantation for CTLA-4 insufficiency across Europe: A European Society for Blood and Marrow Transplantation Inborn Errors Working Party study.

BACKGROUND: Cytotoxic T-lymphocyte antigen 4 (CTLA-4) insufficiency causes a primary immune regulatory disorder characterized by lymphoproliferation, dysgammaglobulinemia, and multiorgan autoimmunity including cytopenias and colitis. OBJECTIVE: We examined the outcome of hematopoietic stem cell transplantation (HSCT) for CTLA-4 insufficiency and study the impact of pre-HSCT CTLA-4 fusion protein (CTLA-4-Ig) therapy and pre-HSCT immune dysregulation on survival and immunologic outcome. METHODS: This was a retrospective study of HSCT for CTLA-4 insufficiency and 2q33.2-3 deletion from the European Society for Blood and Marrow Transplantation Inborn Errors Working Party. Primary end points were overall survival (OS) and disease- and chronic graft-versus-host disease-free survival (DFS). Secondary end point was immunologic outcome assessed by immune dysregulation disease activity (IDDA) score. RESULTS: Forty patients were included over a 25-year period. Before HSCT, 60% received CTLA-4-Ig, and median (range) IDDA score was 23.3 (3.9-84.0). Median (range) age at HSCT was 14.2 (1.3-56.0) years. Patients received peripheral blood stem cell (58%) or marrow (43%) from a matched unrelated donor (75%), mismatched unrelated donor (12.5%), or matched family donor (12.5%). Median (range) follow-up was 3 (0.6-15) years, and 3-year OS was 76.7% (58-87%) and DFS was 74.4% (54.9-86.0%). At latest follow-up, disease of 28 of 30 surviving patients was in disease-free remission with median IDDA reduction of 16. Probability of OS and DFS was greater in patients with lower disease activity before HSCT (IDDA < 23, P = .002 and P = .006, respectively). CTLA-4-Ig receipt did not influence OS or DFS. Cause of death was transplant related in 7 of 8 patients. CONCLUSION: HSCT is an effective therapy to prevent ongoing disease progression and morbidity, with improving survival rates over time and in patients with lower pre-HSCT disease activity.

Safety and Efficacy of High-Dose Memory CD45RO+ Donor Lymphocyte Infusion in Pediatric Recipients after Hematopoietic Stem Cell Transplantation.

Memory T selected cells (CD45RA-/RO+) as donor lymphocyte infusion are less capable of producing alloreactivity and graft versus host disease (GvHD) compared with naïve T cells. The objective of this study was to evaluate the safety and efficacy of high-dose memory (CD45RA-/RO+) donor lymphocyte infusion (mDLI) after allogeneic hematopoietic cell transplantation (HCT). Indications for mDLI were "as needed" and "as prophylactic regimen." Sixty-one children diagnosed with malignant (82%) and non-malignant diseases (18%) received 241 mDLIs. Patients received a median of three infusions (range 1‒13) of mDLI with a median infused dose of 1.35 × 107/kg CD45RO+ containing 8.96 × 106/kg CD3+CD45RO+ and 3.81 × 103/kg CD3+CD45RA+. De novo GvHD developed in 7 patients following 4% of the mDLI infusions. Among patients with GvHD before mDLI, this condition worsened following 6 infusions (11%) in the 3 patients with grade II-IV acute GvHD. A decrease in cytomegalovirus viral load followed 65% of mDLI infusions. Two-year overall survival (OS) for the total cohort was 64% (95% CI 57%‒72%). For patients receiving prophylactic mDLI, the two-year non-relapse mortality was 10% (95% CI 9%‒11%). In summary, high-dose mDLI is feasible and safe, with a relatively low risk of severe GvHD even in patients with active GvHD. Importantly, mDLI was associated with positive effects, including enhanced control of CMV viremia.

A retrospective study of treosulfan versus busulfan-based conditioning in pediatric patients.

OBJECTIVES: To compare the outcomes of treosulfan-based vs busulfan-based conditioning regimens in allogeneic hematopoietic stem cell transplantation (HSCT) in pediatric patients. METHODS: Retrospective study of all consecutive patients (2012-2019) treated with allogenic HSCT and treosulfan- or busulfan-based conditioning regimens at a single center. RESULTS: A total of 101 HSCT were included: 66 HSCT with busulfan and 35 with treosulfan. In malignant diseases (n = 62), busulfan-based conditioning was more commonly employed than treosulfan: 82.3% vs 17.7%. However, the use of treosulfan for malignant diseases increased over time: 6.5% of HSCT in 2012-2015 vs 29% of HSCT in 2015-2019 (p = .02). The cohort of treosulfan had more children under 1-year of age than the busulfan cohort (31 vs 13%; p = .033). The percentage of patients who received serotherapy was 73 and 89% in the nonmalignant and malignant groups, respectively. The engraftment, time to neutrophil, and platelet engraftment were not significantly different between the busulfan and the treosulfan cohorts. Rate of grade II-IV acute GvHD was significantly higher in the busulfan cohort than the treosulfan cohort (39% vs 15%; p = .016). No differences were observed in endothelial damage complications, chronic GvHD, relapse, overall survival, and transplant-related mortality. CONCLUSIONS: Busulfan-based conditioning regimens are used more frequently for children undergoing allogenic HSCT, but treosulfan-based conditioning is gaining acceptance. Treosulfan-based conditioning is associated with lower rates of acute GvHD, and no significant differences on overall survival were observed compared with busulfan.

Failure of Viral-Specific T Cells Administered in Pre-transplant Settings in Children with Inborn Errors of Immunity.

PURPOSE: Use of adoptive immunotherapy with virus-specific T cells (VST) in patients with inborn errors of immunity prior to hematopoietic stem cell transplantation (HSCT) has been reported in few patients. We report our experience, reviewing all the cases previously reported. METHODS: We report four children with inborn errors of immunity who received VST infusion in a pre-HSCT setting in two reference centers in Spain and review all inborn errors of immunity cases previously reported. RESULTS: Taking into account our four cases, nine children have been reported to receive VST prior to HSCT to date: 3 severe combined immunodeficiency, 2 CTPS1 deficiency, 1 dyskeratosis congenital, 1 ORAI1 deficiency, 1 Rothmund-Thomson syndrome, and 1 combined immunodeficiency without confirmed genetic defect. In four patients, immunotherapy resulted in clinical improvement, allowing to proceed to HSCT. In these cases, the infusion was started closely to viral diagnosis [mean time 28 days (IQR; 17-52 days)], and the VST was followed shortly thereafter by HSCT [mean time 28 days (IQR; 10-99 days)]. Viremia was controlled after HSCT in two cases (performed 7 and 36 days after the infusion). Multiple infusions were required in many cases. Five out of nine patients died before receiving HSCT. These patients presented with a prolonged and uncontrolled infection before VST administration [mean time from viral diagnosis to VST infusion was 176 days (IQR; 54-1687)]. CONCLUSIONS: In patients with inborn errors of immunity, the efficacy of VST for treating disseminated viral infections in pre-transplant settings seems to have a limited efficacy. However, this therapy could be used in a pre-emptive setting before severe viral disease occurs or closely to HSCT.

The role of early natural killer cell adoptive infusion before engraftment in protecting against human herpesvirus-6B encephalitis after naïve T-cell-depleted allogeneic stem cell transplantation.

BACKGROUND: Naïve T-cell-depleted grafts have been employed as an ex vivo T-cell depletion (TCD) platform to prevent graft-versus-host disease (GvHD) and improve immune reconstitution by providing rapid donor memory T-cell reconstitution after allogenic hematopoietic stem cell transplantation (allo-HSCT). CD45RA- memory T cells confer protection against viruses such as cytomegalovirus, Epstein-Barr virus, and adenovirus; however, reports have shown an unexpectedly high incidence of human herpesvirus (HHV)-6B encephalitis among pediatric allo-HSCT patients. METHODS: We report the first 18 consecutive allo-HSCT, 16 haplo-HSCT, and two human leukocyte antigen-matched related donors implanted with naïve TCD grafts. All donors were administered three cell products: first, a CD34+ stem cell product; second, a CD45RA+ TCD graft, followed by an adoptive natural killer (NK) cell infusion within 10 days after HSCT. The study's primary endpoint was the incidence of HHV-6B encephalitis. RESULTS: Engraftment was achieved in 94.5% of cases; 2-year overall survival, event-free survival, and GvHD/relapse-free survival were 87.2% (95% CI 78.6-95.8), 67.3% (95% CI 53.1-81.5), and 64% (95% CI 50.5-78.1), respectively. HHV-6B reactivation occurred in 7 of the haplo-HSCT patients, six of who received a cell infusion with an NK/CD4 ratio <2. None of the patients developed encephalitis. CONCLUSIONS: In this clinical study, we show that early adoptive NK cell infusion after a 45RA+ TCD allo-HSCT graft is safe and can prevent HHV-6B encephalitis. We recommend infusing adoptive NK cells after allo-HSCT using CD45RA+ TCD grafts.

Haploidentical transplantation in pediatric non-malignant diseases: A retrospective analysis on behalf of the Spanish Group for Hematopoietic Transplantation (GETH).

OBJECTIVE: Describe the GETH haploidentical stem cell transplantation (haplo-HSCT) activity in non-malignant disease (NMDs). METHODS: We retrospectively analyzed data from children with NMDs who underwent haplo-HSCT. RESULTS: From January 2001 to December 2016, 26 pediatric patients underwent 31 haplo-HSCT through ex vivo T cell-depleted (TCD) graft platforms or post-transplantation cyclophosphamide (PT-Cy) at 7 Spanish centers. Five cases employed unmanipulated PT-Cy haplo-HSCT, 16 employed highly purified CD34+ cells, and 10 employed ex vivo TCD grafts manipulated either with CD3+ CD19+ depletion, TCRαß+ CD19+ selection or naive CD45RA+ T-cell depletion. Peripheral blood stem cells were the sole source for patients following TCD haplo-HSCT, and bone marrow was the source for one PT-Cy haplo-HSCT. The most common indications for transplantation were primary immunodeficiency disorders (PIDs), severe aplastic anemia, osteopetrosis, and thalassemia. The 1-year cumulative incidence of graft failure was 27.4%. The 1-year III-IV acute graft-versus-host disease (GvHD) and 1-year chronic GvHD rates were 34.6% and 16.7%, respectively. The 2-year overall survival was 44.9% for PIDs, and the 2-year graft-versus-host disease-free and relapse-free survival rate was 37.6% for the other NMDs. The transplantation-related mortality at day 100 was 30.8%. CONCLUSION: Although these results are discouraging, improvements will come if procedures are centralized in centers of expertise.

Ruxolitinib for steroid-refractory graft versus host disease in pediatric HSCT: high response rate and manageable toxicity.

Ruxolitinib, a selective Janus Kinase (JAK) 1/2 inhibitor, is a promising treatment for the steroid-refractory graft-vs-host disease (GvHD) after hematopoietic stem cell transplantation (HSCT). Most studies have been performed in the adult population showing efficacy against GvHD. In this retrospective study, we evaluated the outcomes of 19 children who received ruxolitinib for refractory acute or chronic GvHD (cGvHD) after HSCT from two Pediatric Hemato-Oncology Departments in Spain between March 2017 and December 2018. Patients received a median number of 4 (IQR 2) previous lines of treatment before starting ruxolitinib. The overall response rate in acute GvHD (aGvHD) and cGvHD was 87% and 91%, respectively. Complete response (CR) was observed in 37% of aGvHD and 8.3% of cGvHD. Remarkably, 43% and 40% of patients with steroid-refractory gastrointestinal aGvHD and lung cGvHD achieved CR. During ruxolitinib treatment, there were 36%, 31%, and 10% infections caused by viruses, bacteria, and fungi, respectively. Overall, four patients interrupted ruxolitinib due to infectious complications, hematological, and liver toxicity. The 2-year overall survival was 71.9% (CI 95% 58.6-85.2). Our experience supports the use of ruxolitinib as an effective treatment for steroid-refractory acute and cGvHD in children with a moderate toxicity profile.

Epigenetic footprint enables molecular risk stratification of hepatoblastoma with clinical implications.

BACKGROUND & AIMS: Hepatoblastoma (HB) is a rare disease. Nevertheless, it is the predominant pediatric liver cancer, with limited therapeutic options for patients with aggressive tumors. Herein, we aimed to uncover the mechanisms of HB pathobiology and to identify new biomarkers and therapeutic targets in a move towards precision medicine for patients with advanced HB. METHODS: We performed a comprehensive genomic, transcriptomic and epigenomic characterization of 159 clinically annotated samples from 113 patients with HB, using high-throughput technologies. RESULTS: We discovered a widespread epigenetic footprint of HB that includes hyperediting of the tumor suppressor BLCAP concomitant with a genome-wide dysregulation of RNA editing and the overexpression of mainly non-coding genes of the oncogenic 14q32 DLK1-DIO3 locus. By unsupervised analysis, we identified 2 epigenomic clusters (Epi-CA, Epi-CB) with distinct degrees of DNA hypomethylation and CpG island hypermethylation that are associated with the C1/C2/C2B transcriptomic subtypes. Based on these findings, we defined the first molecular risk stratification of HB (MRS-HB), which encompasses 3 main prognostic categories and improves the current clinical risk stratification approach. The MRS-3 category (28%), defined by strong 14q32 locus expression and Epi-CB methylation features, was characterized by CTNNB1 and NFE2L2 mutations, a progenitor-like phenotype and clinical aggressiveness. Finally, we identified choline kinase alpha as a promising therapeutic target for intermediate and high-risk HBs, as its inhibition in HB cell lines and patient-derived xenografts strongly abrogated tumor growth. CONCLUSIONS: These findings provide a detailed insight into the molecular features of HB and could be used to improve current clinical stratification approaches and to develop treatments for patients with HB. LAY SUMMARY: Hepatoblastoma is a rare childhood liver cancer that has been understudied. We have used cutting-edge technologies to expand our molecular knowledge of this cancer. Our biological findings can be used to improve clinical management and pave the way for the development of novel therapies for this cancer.

Haploidentical transplantation in high-risk pediatric leukemia: A retrospective comparative analysis on behalf of the Spanish working Group for bone marrow transplantation in children (GETMON) and the Spanish Grupo for hematopoietic transplantation (GETH).

A total of 192 pediatric patients, median age 8.6 years, with high-risk hematological malignancies, underwent haploidentical stem cell transplantation (haplo-HSCT) using post-transplantation cyclophosphamide (PT-Cy), or ex vivo T cell-depleted (TCD) graft platforms, from January 1999 to December 2016 in 10 centers in Spain. Some 41 patients received an unmanipulated graft followed by PT-Cy for graft-vs-host disease (GvHD) prophylaxis. A total of 151 patients were transplanted with CD3-depleted peripheral blood stem cells (PBSCs) by either CD34+ selection, CD3+ CD19+ depletion, TCRαß+ CD19+ depletion or CD45RA+ depletion, added to CD34+ selection for GvHD prophylaxis. The PBSCs were the only source in patients following ex vivo TCD haplo-HSCT; bone marrow was the source in 9 of 41 patients following PT-CY haplo-HSCT. Engraftment was achieved in 91.3% of cases. A donor younger than 30 years, and the development of chronic GvHD were positive factors influencing survival, whereas positive minimal residual disease (MRD) before transplant and lymphoid disease were negative factors. The probability of relapse increased with lymphoid malignancies, a donor killer-cell immunoglobulin-like receptor (KIR) haplotype A and positive MRD pretransplant. No difference was found in overall survival, disease-free survival or relapse incidence between the two platforms. Relapse is still of concern in both platforms, and it should be the focus of future efforts. In conclusion, both platforms for haplo-HSCT were effective and could be utilized depending on the comfort level of the center.

Severe Impairment of T-cell Immunity and Pulmonary GvHD Are Major Risk Factors for Nontuberculous Mycobacterial Infection After Pediatric Allogeneic Hematopoietic Stem Cell Transplantation.

Hematopoietic stem cell transplant recipients are prone to infectious complications. Infections caused by nontuberculous mycobacteria have increased in adults but literature in children is scarce. We report 6 episodes of disseminated or pulmonary nontuberculous mycobacteria infection among 5 pediatric hematopoietic stem cell transplant recipients. All but one were caused by Mycobacterium avium complex. Four patients died, 2 related to nontuberculous mycobacteria infection.

Haploidentical versus Cord Blood Transplantation in Pediatric AML. A Retrospective Outcome Analysis on Behalf of the Pediatric Subcommittee of GETH (Grupo Español de Trasplante Hematopoyético).

Haploidentical stem cell transplantation (Haplo-SCT) and cord blood transplantation (CBT) are both effective alternative treatments in patients suffering from acute myeloid leukemia (AML) and lacking a matched HLA donor. In the last years, many centers have abandoned CBT procedures mostly due to concern about poorer immune recovery compared with Haplo-SCT. We conducted a retrospective multicenter study comparing the outcomes using both alternative approaches in AML. A total of 122 transplants (86 Haplo-SCTs and 36 CBTs) from 12 Spanish centers were collected from 2007 to 2021. Median age at hematopoietic stem cell transplantation (HSCT) was 7 years (0.4-20). Thirty-nine patients (31.9%) showed positive minimal residual disease (MRD) at HSCT and a previous HSCT was performed in 37 patients (30.3%). The median infused cellularity was 14.4 × 106/kg CD34+ cells (6.0-22.07) for Haplo-SCT and 4.74 × 105/kg CD34+ cells (0.8-9.4) for CBT. Median time to neutrophil engraftment was 14 days (7-44) for Haplo-SCT and 17 days (8-29) for CBT (P = .03). The median time to platelet engraftment was 14 days (6-70) for Haplo-SCT and 43 days (10-151) for CBT (P < .001). Graft rejection was observed in 13 Haplo-SCTs (15%) and in 6 CBTs (16%). The cumulative incidence of acute graft versus host disease (GvHD) grades II-IV was 54% and 51% for Haplo-SCT and CBT, respectively (P = .50). The cumulative incidence of severe acute GvHD (grades III-IV) was 22% for Haplo-SCT and 25% for CBT (P = .90). There was a tendency to a higher risk of chronic GvHD in the Haplo-SCT group being the cumulative incidence of 30% for Haplo-SCT and 12% for CBT (P = .09). The cumulative incidence of relapse was 28% and 20% for Haplo-SCT and CBT, respectively (P = .60). We did not observe statistically significant differences in outcome measures between Haplo-SCT and CBT procedures: 5-year overall survival (OS) was 64% versus 57% (P = .50), 5-year disease-free survival (DFS) 58% versus 57% (P = .80), GvHD-free and relapse-free survival (GFRFS) 41% versus 54% (P = .30), and cumulative incidence of transplant-related mortality (TRM) 14% versus 15% (P = .80), respectively. In the multivariate analysis, MRD positivity and a disease status >CR1 at the time of HSCT were significantly associated with poorer outcomes (P < .05). In conclusion, our study supports that both haploidentical and cord blood transplantation show comparable outcomes in pediatric AML patients. We obtained comparable survival rates, although CBT showed a trend to lower rates of chronic GvHD and higher GFRFS, demonstrating that it should still be considered a valuable option, particularly for pediatric patients.

Younger age and induction failure predict outcomes in infant leukemia: 30 years of experience in a tertiary center.

Objectives: This study aimed to evaluate the characteristics and outcomes of infant patients with leukemia. Methods: A retrospective analysis was conducted in a cohort of 39 patients diagnosed with infant leukemia from 1990 to 2020 who underwent treatment at the pediatric hemato-oncology department of a tertiary hospital in Madrid, Spain. Results: Of the 588 diagnosed cases of childhood leukemia, 39 (6.6%) cases were infant leukemia. The 5-year event-free survival and the 5-year overall survival were 43.6% (SE 4.1) and 46.5% (SD 24.08), respectively. In a univariate analysis, a younger age at diagnosis was associated with poorer outcomes (p = 0.027), as was induction failure (p = 0.0024). Patients treated with hematopoietic stem cell transplantation had better outcomes than non-transplanted patients (p = 0.001); however, the group comparisons that exclude patients who were unable to undergo transplantation due to refractoriness/relapse or death during treatment showed no significant differences. Conclusions: The main risk factors that affected survival in our study were an age younger than 6 months and a poor response to induction therapy. It is important to identify poor prognostic factors in this population in order to seek different approaches that could improve outcomes.

Haploidentical hematopoietic stem cell transplantation in pediatric and adolescent patients: A study of the Spanish hematopoietic stem cell transplantation group (GETH).

INTRODUCTION: The main advantages of haploidentical hematopoietic stem cell transplantation (haplo-HSCT) are the immediate availability of donors, the possibility of developing cell therapy approaches with different novel transplant platforms, and the procedure's cost savings. METHODOLOGY: We retrospectively analyzed the pediatric haplo-HSCT activity of the Spanish hematopoietic stem-cell transplantation group (GETH) between 1999 and 2016, aiming to study clinical characteristics and outcomes by describing patient groups with non-malignant disease (NMD) or malignant disease (MD) and the impact of 2 different periods (1999-2009 and 2010-2016) on long-term outcomes. RESULTS: Twelve centers performed 232 haplo-HSCTs in 227 children, representing 10% of all pediatric allogeneic HSCT activity in Spain from 1999 to 2016, with a notable increase since 2013. Most haplo-HSCTs (86.7%) were performed in patients with MD; 95% received peripheral blood stem cells from donors, and 78.9% received ex vivo T-cell depleted grafts. Non-manipulated grafts using post-transplantation cyclophosphamide have been incorporated since 2012. We observed a higher percentage of graft failure in NMD versus MD (32% vs. 15.6%; p=0.029). Relapse and transplant-related mortality were the procedure's main limitations in MD and NMD, respectively. Five-year overall survival was 48.5% (SE 3.9), with no statistically significant difference when comparing the MD and NMD cohorts. Patients who received previously a HSCT the overall survival was significantly decreased. We observed no survival improvement over time. CONCLUSIONS: Although haplo-HSCT is an increasingly employed treatment option, our patients' results need improvement. We need to develop reference centers, especially for NMD whose rarity makes it difficult to gain experience.

Selective T-cell depletion targeting CD45RA as a novel approach for HLA-mismatched hematopoietic stem cell transplantation in pediatric nonmalignant hematological diseases.

Severe aplastic anemia and congenital amegakaryocytic thrombocytopenia are rare bone marrow failure syndromes. Treatment for aplastic anemia consists of hematopoietic stem cell transplantation (HSCT) from a matched sibling donor or immunosuppressant drugs if there is no donor available. Congenital amegakaryocytic thrombocytopenia is a rare autosomal recessive disease that causes bone marrow failure and has limited treatment options, except for transfusion support and HSCT. In the absence of a suitable matched sibling donor, matched-unrelated, haploidentical, or mismatched donors may be considered. A 2-step partial T-cell-depletion strategy can remove CD45RA+ naïve T cells responsible for graft-versus-host disease (GvHD) while preserving memory T cells. Five patients underwent transplantation using this strategy with rapid neutrophil and platelet recovery. Acute and chronic GvHD ≥ grade 2 appeared in two and one patient, respectively. No severe infections were observed before day + 100. A high (60%) incidence of transplant-associated microangiopathy was observed. Three patients (60%) remain alive, with a median follow-up of 881 (range 323-1248) days. CD45RA-depleted HSCT is a novel approach for patients lacking a suitable matched donor; however, further improvements are needed.

Stem Cell Transplantation for Diamond-Blackfan Anemia. A Retrospective Study on Behalf of the Severe Aplastic Anemia Working Party of the European Blood and Marrow Transplantation Group (EBMT).

Data on stem cell transplantation (SCT) for Diamond-Blackfan Anemia (DBA) is limited. We studied patients transplanted for DBA and registered in the EBMT database. Between 1985 and 2016, 106 DBA patients (median age, 6.8 years) underwent hematopoietic stem cell transplantation from matched-sibling donors (57%), unrelated donors (36%), or other related donors (7%), using marrow (68%), peripheral blood stem cells (20%), both marrow and peripheral blood stem cells (1%), or cord blood (11%). The cumulative incidence of engraftment was 86% (80% to 93%), and neutrophil recovery and platelet recovery were achieved on day +18 (range, 16 to 20) and +36 (range, 32 to 43), respectively. Three-year overall survival and event-free survival were 84% (77% to 91%) and 81% (74% to 89%), respectively. Older patients were significantly more likely to die (hazard ratio, 1.4; 95% confidence interval, 1.06 to 1.23; P < .001). Outcomes were similar between sibling compared to unrelated-donor transplants. The incidence of acute grades II to IV of graft-versus-host disease (GVHD) was 30% (21% to 39%), and the incidence of extensive chronic GVHD was 15% (7% to 22%). This study shows that SCT may represent an alternative therapeutic option for transfusion-dependent younger patients.

Current Practices on Diagnosis, Prevention and Treatment of Post-Transplant Lymphoproliferative Disorder in Pediatric Patients after Solid Organ Transplantation: Results of ERN TransplantChild Healthcare Working Group Survey.

(1) Background: Post-transplant lymphoproliferative disease (PTLD) is a significant complication of solid organ transplantation (SOT). However, there is lack of consensus in PTLD management. Our aim was to establish a present benchmark for comparison between international centers and between various organ transplant systems and modalities; (2) Methods: A cross-sectional questionnaire of relevant PTLD practices in pediatric transplantation was sent to multidisciplinary teams from 17 European center members of ERN TransplantChild to evaluate the centers' approach strategies for diagnosis and treatment and how current practices impact a cross-sectional series of PTLD cases; (3) Results: A total of 34 SOT programs from 13 European centers participated. The decision to start preemptive treatment and its guidance was based on both EBV viremia monitoring plus additional laboratory methods and clinical assessment (61%). Among treatment modalities the most common initial practice at diagnosis was to reduce the immunosuppression (61%). A total of 126 PTLD cases were reported during the period 2012-2016. According to their histopathological classification, monomorphic lesions were the most frequent (46%). Graft rejection after PTLD remission was 33%. Of the total cases diagnosed with PTLD, 88% survived; (4) Conclusions: There is still no consensus on prevention and treatment of PTLD, which implies the need to generate evidence. This might successively allow the development of clinical guidelines.

Possible role of highly activated mucosal NK cells against viral respiratory infections in children undergoing haematopoietic stem cell transplantation.

Infection is the leading cause of non-relapse-related mortality after allogeneic haematopoietic stem cell transplantation (HSCT). Altered functions of immune cells in nasal secretions may influence post HSCT susceptibility to viral respiratory infections. In this prospective study, we determined T and NK cell numbers together with NK activation status in nasopharyngeal aspirates (NPA) in HSCT recipients and healthy controls using multiparametric flow cytometry. We also determined by polymerase chain reaction (PCR) the presence of 16 respiratory viruses. Samples were collected pre-HSCT, at day 0, +10, +20 and +30 after HSCT. Peripheral blood (PB) was also analyzed to determine T and NK cell numbers. A total of 27 pediatric HSCT recipients were enrolled and 16 of them had at least one viral detection (60%). Rhinovirus was the most frequent pathogen (84% of positive NPAs). NPAs of patients contained fewer T and NK cells compared to healthy controls (p = 0.0132 and p = 0.120, respectively). Viral PCR + patients showed higher NK cell number in their NPAs. The activating receptors repertoire expressed by NK cells was also higher in NPA samples, especially NKp44 and NKp46. Our study supports NK cells relevance for the immune defense against respiratory viruses in HSCT recipients.