Outcome Analysis of Pediatric Patients with Acute Lymphoblastic Leukemia Treated with Total Body Irradiation–Free Allogeneic Hematopoietic Stem Cell Transplantation: Comparison of Patients with and Without Central Nervous System Involvement

Global research trends in Total Body Irradiation: a bibliometric analysis

Objectives

This manuscript presents a bibliometric and visualization analysis of Total Body Irradiation (TBI) research, aiming to elucidate trends, gaps, and future directions in the field. This study aims to provide a comprehensive overview of the global research landscape of TBI, highlighting its key contributions, evolving trends, and potential areas for future exploration.

Methods

The data for this study were extracted from the Web of Science Core Collection (WoSCC), encompassing articles published up to May 2023. The analysis included original studies, abstracts, and review articles focusing on TBI-related research. Bibliometric indicators such as total publications (TP), total citations (TC), and citations per publication (C/P) were utilized to assess the research output and impact. Visualization tools such as VOS Viewer were employed for thematic mapping and to illustrate international collaboration networks.

Results

The analysis revealed a substantial body of literature, with 7,315 articles published by 2,650 institutions involving, 13,979 authors. Full-length articles were predominant, highlighting their central role in the dissemination of TBI research. The authorship pattern indicated a diverse range of scholarly influences, with both established and emerging researchers contributing significantly. The USA led in global contributions, with significant international collaborations observed. Recent research trends have focused on refining TBI treatment techniques, investigating long-term patient effects, and advancing dosimetry and biomarker studies for radiation exposure assessments.

Conclusions

TBI research exhibits a dynamic and multifaceted landscape, driven by global collaboration and innovation. It highlights the clinical challenges of TBI, such as its adverse effects and the need for tailored treatments in pediatric cases. Crucially, the study also acknowledges the fundamental science underpinning TBI, including its effects on inflammatory and apoptotic pathways, DNA damage, and the varied sensitivity of cells and tissues. This dual focus enhances our understanding of TBI, guiding future research toward innovative solutions and comprehensive care.

Total body irradiation-free haploidentical peripheral blood stem cell transplantation compared to related and unrelated donor transplantation in pediatrics with acute lymphoblastic leukemia

BACKGROUND

Acute lymphoblastic leukemia (ALL) is the most prevalent childhood cancer under the age of 15 years. Despite the recent advances in therapeutic regimens, relapse occurs in 15%-20% of pediatric patients after chemotherapy, and hematopoietic stem cell transplantation (HSCT) is the best treatment option. However, donor availability is one of the major challenges. Over the last decade, haploidentical donor (HID) transplantation has evolved as an alternative option. Herein, we aimed to compare the transplant outcomes in pediatric patients receiving total body irradiation (TBI)-free myeloablative regimens, between non-HID and HID transplant.

PATIENTS AND METHODS

The study included 60 pediatric ALL patients who had undergone HSCT from October 2016 until September 2020. Forty-three patients received non-HID HSCT, while 17 patients received HID. The sources of stem cells (SC) were peripheral blood stem cells (PBSC) for all the patients. The conditioning regimen was based on busulfan and cyclophosphamide. For graft-versus-host disease (GvHD) prophylaxis, patients received cyclosporine and methotrexate in the setting of non-HID transplantation, where HIDs received post-transplant cyclosporine and cyclophosphamide.

RESULTS

The cumulative incidences of 3-year overall survival (OS) were 73.1%, 66.6%, and 69.5%, for matched sibling donor-matched related donor (MSD-MRD), matched unrelated donor-mismatched unrelated donor (MUD-MMUD), and HID groups, respectively (p = .85). The cumulative incidences of grade II-IV acute GvHD for the MRD, MUD-MMUD, and HID groups were 29%, 41%, and 49%, respectively (p = .47). Furthermore, the 3-year cumulative incidence of chronic GvHD was MSD-MRD: 70% versus MUD-MMUD: 42% versus HID: 45% (p = .64). The 3-year cumulative incidence of relapse post transplantation was 45%, 18%, and 45%, respectively, for the MSD-MRD, MUD-MMUD, and HID groups, and the differences were not statistically significant (p = .55). There was a higher risk for cytomegalovirus (CMV) infection in patients receiving HID transplants compared to those of non-HIDs (p < .01).

CONCLUSION

Our results indicate that PBSC-HID transplant outcomes in the setting of non-TBI conditioning are comparable to those of non-HIDs in pediatric ALL patients.

HSCT with mismatched unrelated donors: Bone marrow versus peripheral blood stem cells sources in pediatric patients

BACKGROUND

Allogeneic hematopoietic stem cell transplantation (HSCT) from an unrelated HLA-mismatched donor (MMUD) is one of the alternatives where an HLA-matched donor is not found. The aim of this study was to compare bone marrow (BM) versus peripheral blood stem cells (PBSC) as hematopoietic rescue following allogeneic unrelated mismatched stem cell transplantation (MMUD).

METHODS

The patients were divided into two groups: 43 pediatric patients were treated with BM and 17 pediatric patients with PBSC. The study was registered at ClinicalTrials.gov NCT04598789.

RESULTS

The 3-year Overall Survival (OS) was 74% versus 31% (p = .0011). Transplant related mortality (TRM) was 16% versus 33% (p = .025), and relapse incidence (RI) was 16% versus 35% (p = .005). The day-100 acute Graft-versus-host disease (GvHD) incidence grade II-IV and III-IV was 30% versus 28% (p = NS) and 17% versus 17% (p = NS). The 3-year chronic GvHD incidence was 22% versus 33% (p = NS).

CONCLUSION

Despite all the limits of this retrospective study we were able to show how the combination of BM and ATG is able to prevent GvHDs and guarantee a high OS. Future studies addressing the issue of a post-transplant cellular therapy approach may potentially reduce relapses when GvHD is absent.

Haploidentical hematopoietic stem cell transplantation may improve long-term survival for children with high-risk T-cell acute lymphoblastic leukemia in first complete remission

Background:

The role of allogeneic hematopoietic stem cell transplantation (allo-HSCT) in children with high-risk (HR) T-cell acute lymphoblastic leukemia (T-ALL) in first complete remission (CR1) is still under evaluation. Moreover, relapse is the main factor affecting survival. This study aimed to explore the effect of allo-HSCT (especially haploidentical HSCT [haplo-HSCT]) on improving survival and reducing relapse for HR childhood T-ALL in CR1 and the prognostic factors of childhood T-ALL in order to identify who could benefit from HSCT.

Methods:

A total of 74 newly diagnosed pediatric T-ALL patients between January 1, 2012 and June 30, 2018 were enrolled in this retrospective study. Patients were stratified into the low-risk chemotherapy cohort (n = 16), HR chemotherapy cohort (n = 31), and HR transplant cohort (n = 27). Characteristics, survival outcomes, and prognostic factors of all patients were then analyzed.

Results:

Patient prognosis in the HR chemotherapy cohort was significantly worse than that in the low-risk chemotherapy cohort (5year overall survival [OS]: 58.5% vs. 100%, P = 0.003; 5-year event-free survival [EFS]: 54.1% vs. 83.4%, P = 0.010; 5-year cumulative incidence of relapse [CIR]: 45.2% vs. 6.3%, P = 0.011). In HR patients, allo-HSCT improved the 5-year EFS and CIR compared to that of chemotherapy (5-year EFS: 80.1% vs. 54.1%, P = 0.041; 5-year CIR: 11.6% vs. 45.2%, P = 0.006). The 5-year OS was higher in the HR transplant cohort than that in the HR chemotherapy cohort (81.0% vs. 58.5%, P = 0.084). Minimal residual disease re-emergence was an independent risk factor for 5-year OS, EFS, and CIR; age ≥10 years was an independent risk factor for OS and EFS; and high white blood cell count was an independent risk factor for EFS and CIR.

Conclusion:

Allo-HSCT, especially haplo-HSCT, could effectively reduce relapse of children with HR T-ALL in CR1.

Acute Lymphoblastic Leukaemia in the Youngest: Haematopoietic Stem Cell Transplantation and Beyond

The ALL SCTped 2012 FORUM (For Omitting Radiation Under Majority age) trial compared outcomes for children ≥4 years of age transplanted for acute lymphoblastic leukaemia (ALL) who were randomised to myeloablation with a total body irradiation (TBI)-based or chemotherapy-based conditioning regimen. The TBI-based preparation was associated with a lower rate of relapse compared with chemoconditioning. Nevertheless, the age considered suitable for TBI was progressively raised over time to spare the most fragile youngest patients from irradiation-related complications. The best approach to use for children <4 years of age remains unclear. Children diagnosed with ALL in their first year of life, defined as infants, have a remarkably poorer prognosis compared with older children. This is largely explained by the biology of their ALL, with infants often carrying a KMT2A gene rearrangement, as well as by their fragility. In contrast, the clinical presentations and biological features of ALL in children >1 year but <4 years often resemble those presented by older children. In this review, we explore the state of the art regarding haematopoietic stem cell transplantation (HSCT) in children <4 years, the preparative regimens available, and new developments in the field that may influence treatment decisions.

Radiation-Free myeloablative allogeneic hematopoietic stem cell transplantation for adult acute lymphoblastic leukemia: A comparison of outcomes between patients with and without central nervous system involvement

For patients with acute lymphoblastic leukemia (ALL) undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT), total body irradiation (TBI) has been particularly advocated as a part of the conditioning regimen in case of extramedullary involvement in sanctuary sites such as the central nervous system (CNS), to ensure greater tissue penetration. In resource-limited countries lacking TBI facilities; however, ALL patients undergo radiation-free myeloablative conditioning, though its impacts on post-HSCT outcomes of the patients with pre-HSCT CNS involvement have not been analyzed. In this 14-year series of 278 adult (> 18 y) ALL patients undergoing TBI-free busulfan/cyclophosphamide conditioning allo-HSCT, we found that the long-term probabilities of overall survival, disease free survival, relapse and non-relapse mortality were not significantly different between CNS-involved and CNS-spared patients. Moreover, there was no statistically significant difference in the incidence of post-HSCT CNS relapse between CNS-involved and CNS-spared patients. Pre-HSCT cranial radiation therapy (CRT) showed no significant preventive effect on the likelihood of post-HSCT CNS relapse. Through multivariable regression analysis, grade III-IV acute graft-versus-host disease (GvHD), extensive chronic GvHD and post-HSCT relapse were ascertained as independent determinants of mortality (Adj.R² = 53.9 %, F_(12,265) = 28.1, P < 0.001), while other parameters including Philadelphia translocation, pre-HSCT CNS involvement and CRT were found to have no independent effect. Although this study was not an attempt to compare TBI-based vs. non-TBI conditioning, the TBI-free myeloablative allo-HSCT was shown to be feasible and an option for adult ALL patients with CNS involvement, considering the comparable outcomes between patients with and without CNS involvement.

Prognosis and risk factors for central nervous system relapse after allogeneic hematopoietic stem cell transplantation in acute myeloid leukemia

We performed a nested case-control study to investigate the incidence, treatment, and prognosis of central nervous system (CNS) relapse after allogenic hematopoietic stem cell transplantation (allo-HSCT) for acute myeloid leukemia (AML) and compared the outcomes of patients with CNS relapse following haploidentical donor (HID) HSCT versus identical sibling donor (ISD) HSCT. A total of 37 patients (HID-HSCT, 24; ISD-HSCT, 13) developed CNS relapse after transplantation between January 2009 and January 2019, with an incidence of 1.81%. The median time from transplantation to CNS relapse was 239 days. Pre-HSCT CNS involvement (HR 6.940, 95% CI 3.146-15.306, p < .001) was an independent risk factor for CNS relapse after allo-HSCT for AML. The 3-year overall survival (OS) for patients with CNS relapse was 60.3 ± 8.8%, which was significantly lower than that in the controls (81.5 ± 4.5%, p = .003). The incidence of CNS relapse was 1.64% for patients who received HID-HSCT and 2.55% for those who received ISD-HSCT (p = .193). There was no significant difference in OS between the HID-HSCT and ISD-HSCT subgroups among the patients with CNS relapse. In conclusion, CNS relapse is a rare but serious complication after allo-HSCT for AML, and the incidence and outcomes of patients with CNS relapse are comparable following HID-HSCT and ISD-HSCT.

A narrative review of central nervous system involvement in acute leukemias

Acute leukemias (both myeloid and lymphoblastic) are a group of diseases for which each year more successful therapies are implemented. However, in a subset of cases the overall survival (OS) is still exceptionally low due to the infiltration of leukemic cells in the central nervous system (CNS) and the subsequent formation of brain tumors. The CNS involvement is more common in acute lymphocytic leukemia (ALL), than in adult acute myeloid leukemia (AML), although the rates for the second case might be underestimated. The main reasons for CNS invasion are related to the expression of specific adhesion molecules (VLA-4, ICAM-1, VCAM, L-selectin, PECAM-1, CD18, LFA-1, CD58, CD44, CXCL12) by a subpopulation of leukemic cells, called “sticky cells” which have the ability to interact and adhere to endothelial cells. Moreover, the microenvironment becomes hypoxic and together with secretion of VEGF-A by ALL or AML cells the permeability of vasculature in the bone marrow increases, coupled with the disruption of blood brain barrier. There is a single subpopulation of leukemia cells, called leukemia stem cells (LSCs) that is able to resist in the new microenvironment due to its high adaptability. The LCSs enter into the arachnoid, migrate, and intensively proliferate in cerebrospinal fluid (CSF) and consequently infiltrate perivascular spaces and brain parenchyma. Moreover, the CNS is an immune privileged site that also protects leukemic cells from chemotherapy. CD56/NCAM is the most important surface molecule often overexpressed by leukemic stem cells that offers them the ability to infiltrate in the CNS. Although asymptomatic or with unspecific symptoms, CNS leukemia should be assessed in both AML/ALL patients, through a combination of flow cytometry and cytological analysis of CSF. Intrathecal therapy (ITT) is a preventive measure for CNS involvement in AML and ALL, still much research is needed in finding the appropriate target that would dramatically lower CNS involvement in acute leukemia.

Total Body Irradiation or Chemotherapy Conditioning in Childhood ALL: A Multinational, Randomized, Noninferiority Phase III Study

Total body irradiation (TBI) before allogeneic hematopoietic stem cell transplantation (HSCT) in pediatric patients with acute lymphoblastic leukemia (ALL) is efficacious, but long-term side effects are concerning. We investigated whether preparative combination chemotherapy could replace TBI in such patients.

Review of the Pharmacokinetics and Pharmacodynamics of Intravenous Busulfan in Paediatric Patients

We aimed to review the pharmacokinetics (PK) of intravenous busulfan in paediatric patients, identify covariate factors influencing exposure, investigate evidence of changes in PK behaviour over time, and correlate exposure with efficacy and toxicity outcomes. A literature review was undertaken of original research published between 2007 and 2019, investigating the PK and pharmacodynamics (PD) of intravenous busulfan in patients ≤ 18 years of age. The review identified 41 publications characterising the PK, and 45 publications describing the PD, of busulfan. Median typical clearance (CL) was 0.22 L/h/kg and median typical volume of distribution was 0.69 L/kg. Patient weight, age, glutathione-S-transferase A1 (GSTA1) genotype and busulfan dosing day/time were the most commonly identified factors affecting CL. Of nine studies investigating changes in CL, seven reported reduced CL over the 4-day course of treatment. Exposure monitoring methods and therapeutic targets were heterogeneous across studies. Relationships between busulfan exposure and patient outcomes were observed in five studies. One study observed a cumulative area under the concentration-time curve over all days of treatment of between 78 and 101 mg/L·h, and two studies observed an average concentration at first dose of < 600 ng/mL improved overall survival, transplant-related mortality, or relapse. One study observed increased sinusoidal obstructive syndrome with maximum busulfan concentration > 1.88 ng/mL. Patient weight, age and GSTA1 genotype are important covariates to consider when individualising busulfan therapy. Reduced busulfan CL over time may need to be accounted for, particularly in patients not receiving phenytoin co-therapy. Standardised monitoring of busulfan exposure over the entire course of treatment and further investigation of the role of busulfan metabolites and pharmacogenomics is warranted.

Long-term brain status and cognitive impairment in children treated for high-risk acute lymphoblastic leukemia with and without allogeneic hematopoietic stem cell transplantation: A single-center study

AIM

The aim of the study was to assess long-term consequences of central nervous system (CNS) prophylaxis in patients with high-risk ALL (HR-ALL) treated according to ALL IC-BFM 2002 and to compare observed abnormalities in patients who underwent allogeneic hematopoietic stem cell transplantation (allo-HSCT) with those who received only prophylactic CNS irradiation (12 Gy) and with control group.

PATIENTS AND METHODS

We studied 29 patients with HR-ALL in CR1 after treatment according to protocol ALL IC-BFM 2002 (14 with allo-HSCT conditioned with fractionated total body irradiation [FTBI] and 15 without HSCT) and 16 children with newly diagnosed ALL (control group). The median time from therapy completion to evaluation was 5 years. To assess brain status, volumetric T1-weighted sequences of magnetic resonance imaging were used. Neuropsychological assessment based on battery neuropsychological tests.

RESULTS

Transplanted patients had significantly lower volumes of white and gray matter (P = .048 and P < .001) and also of subcortical structures, including the thalamus (P < .001), the hippocampus (P = .007), the putamen (P = .011), the globus pallidus (P = .001), and the accumbens (P < .001). In addition, these patients had generally lower cognitive performance, especially in vocabulary (P = .011), visuospatial ability (P = .047), executive functions and attention (P = .034; P = .002; P = .048), and processing speed (P = .049 and P = .037). The thalamus volume is correlated with neuropsychological performance in verbal functions (P < .001), executive functions (P < .001 and P = .024), and processing speed (P < .001).

CONCLUSIONS

In pediatric patients treated for ALL, FTBI-based preparative regimen preceding allo-HSCT causes reduction of subcortical structure volumes and decline in cognitive performance. The observed long-term structural and functional CNS sequelae are significantly more pronounced in transplanted HR-ALL patients than in those treated with prophylactic CNS- radiotherapy only.

Direct Delivery of piggyBac CD19 CAR T Cells Has Potent Anti-tumor Activity against ALL Cells in CNS in a Xenograft Mouse Model

The anti-CD19 chimeric antigen receptor (CAR) T cells showed excellent effect against acute lymphoblastic leukemia (ALL) in bone marrow (BM) in clinical trials. However, it remains to be elucidated whether the CD19 CAR T cell therapy is effective for ALL cells in central nervous system (CNS) because the patients with isolated or advanced CNS disease were excluded from clinical trials of systemic intravenous (i.v.) delivery of CAR T cells. Therefore, the preclinical evaluation for the efficacy of CAR T cell therapy against ALL cells in CNS is essential for clinical application. We evaluated the effect and adverse reaction of CD19 CAR T cells against ALL in CNS using a xenograft mouse model by i.v. or intra-cerebroventricular (i.c.v.) delivery of CAR T cells. Injection of piggyBac CD19 CAR T cells by i.v. had partial effects, whereas all CAR T i.c.v.-delivered mice had eliminated ALL in CNS. Although some CAR T i.c.v.-delivered mice showed transient changes of clinical symptoms during the first few days after treatment, none of CAR T i.c.v.-delivered mice displayed fatal adverse events. In this study, we demonstrated that direct delivery into CNS of CAR T cells is a possible therapeutic approach with the xenograft mouse model.

Myeloablative conditioning for allo-HSCT in pediatric ALL: FTBI or chemotherapy?-A multicenter EBMT-PDWP study

Although most children with acute lymphoblastic leukemia (ALL) receive fractionated total body irradiation (FTBI) as myeloablative conditioning (MAC) for allogeneic hematopoietic stem cell transplantation (allo-HSCT), it is an important matter of debate if chemotherapy can effectively replace FTBI. To compare outcomes after FTBI versus chemotherapy-based conditioning (CC), we performed a retrospective EBMT registry study. Children aged 2–18 years after MAC for first allo-HSCT of bone marrow (BM) or peripheral blood stem cells (PBSC) from matched-related (MRD) or unrelated donors (UD) in first (CR1) or second remission (CR2) between 2000 and 2012 were included. Propensity score weighting was used to control pretreatment imbalances of the observed variables. 3.054 patients were analyzed. CR1 (1.498): median follow-up (FU) after FTBI (1.285) and CC (213) was 6.8 and 6.1 years. Survivals were not significantly different. CR2 (1.556): median FU after FTBI (1.345) and CC (211) was 6.2 years. Outcomes after FTBI were superior as compared with CC with regard to overall survival (OS), leukemia-free survival (LFS), relapse incidence (RI), and nonrelapse mortality (NRM). However, we must emphasize the preliminary character of the results of this retrospective “real-world-practice” study. These findings will be prospectively assessed in the ALL SCTped 2012 FORUM trial.

[The efficacy analysis of allogeneic hematopoietic stem cell transplantation in 48 leukemia patients with central nervous system leukemia]

Objective: To investigate the efficacy of allogeneic hematopoietic stem cell transplantation (allo-HSCT) in the treatment of leukemia patients also suffering from central nervous system leukemia (CNSL) . Methods: A total of 48 leukemia patients with central nervous system leukemia admitted to our hospital from May 2012 to December 2017 were retrospectively analyzed. Results: ① Including 22 cases of acute lymphocytic leukemia (ALL) , 21 cases of acute myeloid leukemia (AML) , and 5 cases of chronic myelogenous leukemia (CML) . Before transplantation, 19 patients achieved complete remission (CR) , and the rest 29 ones without remission. ②The conditioning regimen used TBI as the main protocol, and 6 patients were combined with whole brain and total spinal cord radiotherapy, 2 with Cyber knife treatment, and children with modified IDA combined with BUCY. ③All 48 patients were successfully transplanted, the median time for leukocyte engraftment was 14 (10-23) days, the median time for platelet transplant 16 (6-78) days. ④Bone marrow was evaluated 28 days after transplantation, all 48 patients reached CR, and DNA testing confirmed that they were all full donor chimerism. ⑤The median follow-up was 14 (2-69) months. Of them, 28 cases survived, 10 relapsed and the rest 3 had recurrence of CNSL after transplantation. One year after allo-HSCT, the overall survival (OS) of CR and non-CR groups were (77.3±10.0) % and (57.6±9.3) % (P=0.409) , respectively, the disease-free survival rates (DFS) were (71.2±11.0) % and (53.9±9.5) % (P=0.386) , respectively. The 1-year OS rates of ALL and AML groups after transplantation were (54.2±10.7) %, (80.1±8.9) %, respectively (P=0.200) , and DFS rates were (49.2±10.8) %, (75.0±9.7) % (P=0.190) , respectively. Conclusion: Allo-HSCT was safe and effective for leukemia patients with CNSL.

Allogeneic stem cell transplantation in the era of novel therapies for acute lymphoblastic leukaemia

Immunotherapy is changing the treatment of acute lymphoblastic leukaemia (ALL) in adults and children. However, regardless of these new therapies, allogeneic hematopoietic cell transplantation (allo-HCT) still play a key role in the treatment of ALL, although it is uncertain how these new therapies will impact on the transplant procedure and indications. This article reviews the indications of allo-HCT for children and adults diagnosed with ALL, the different sources and conditioning regimens for transplantation as well as the role of measurable residual diseases pre- and post-HCT in the era of the new therapies for ALL.

CircRNA_014511 affects the radiosensitivity of bone marrow mesenchymal stem cells by binding to miR-29b-2-5p

Hematopoietic stem cell transplantation is commonly used in patients with certain hematological or bone marrow tumors. Total body irradiation combined with chemotherapy is part of the preconditioning protocol that was the most commonly used before hematopoietic stem cell transplantation. However, total body irradiation preconditioning damages other normal cells in bone marrow. Therefore, exploring the mechanism of radiation resistance in bone marrow mesenchymal stem cells is of great significance for recovering the hematopoietic function after cell transplantation. This study aimed to demonstrate the miR-29b adsorption of circRNA_014511 and explore the effect of circRNA_014511 on radiosensitivity of bone marrow mesenchymal stem cells. In this study, circRNA_014511 overexpression vector was constructed and transfected into bone marrow mesenchymal stem cells, miR-29b-2-5p and P53 were found to be decreased, which could be reversed by miR29b-mimics. Dual luciferase reporter assay confirmed the binding of circRNA_014511 and mmu-miR-29b-2-5p. Flow cytometry analysis showed the apoptosis rate of bone marrow mesenchymal stem cells overexpressing circRNA_014511 was significantly decreased. In the circRNA_014511 transfection group, after cells were subjected to 6Gy irradiation, G2 phase arrest appeared, the expression of P21 and GADD45A was significantly decreased, and cyclin B1 was significantly increased. Colony formation assay showed the survival fraction of circRNA_014511 overexpression cells after irradiation was significantly higher than control group, and the radiosensitivity was decreased. In conclusion，our findings demonstrated that circRNA_014511 could inhibit the expression of P53 by binding miR-29b-2-5p, and decrease the radiosensitivity of bone marrow mesenchymal stem cells by affecting cell cycle and cell apoptosis.

Unexpected High Incidence of Human Herpesvirus-6 Encephalitis after Naive T Cell-Depleted Graft of Haploidentical Stem Cell Transplantation in Pediatric Patients

The CD45RA T cell depletion (TCD) method has been used to deplete naive T cells, preventing graft-versus-host disease (GVHD) but preserving memory cells, providing immediate functional T cells with anti-infection, antileukemia, and antirejection effects. We describe a series of 25 consecutive high-risk patients with leukemia who received haploidentical hematopoietic stem cell transplantation (haplo-HSCT) with CD45RA TCD. Each patient received 2 cell products: 1 created by CD34 positive selection and the other through CD45RA depletion from the CD34 negative fraction by a CliniMACS device. CD45RA-depleted haplo-HSCT was well tolerated, with rapid engraftment and low risk of severe acute GVHD and chronic GVHD. Although this treatment achieved a good control of viral reactivations, such as cytomegalovirus and adenovirus, we observed an unexpectedly high rate of limbic encephalitis due to human herpesvirus-6 (HHV-6; 8 cases). Characteristically, the infection appeared early in almost all patients, just after the engraftment. Although no patient died from encephalitis, 1 patient showed neuropsychological sequelae, and another experienced secondary graft failure just after the HHV-6 reactivation.