TCRαβ/CD19-depleted HCT has been used with excellent outcomes in pediatric patients with hematologic malignancies, and several studies have demonstrated rapid immune reconstitution in the nonmalignant setting. However, immune recovery following TCRαβ/CD19-depleted hematopoietic cell transplantation (HCT) for malignancy remains incompletely elucidated. Furthermore, the majority of studies to date have used haploidentical and matched unrelated donors. Here we report results of immune reconstitution following TCRαβ/CD19-depleted HCT for hematologic malignancy in 51 pediatric patients with hematologic malignancies, the majority of whom received grafts from unrelated donors. Grafts were from matched unrelated (n = 20), mismatched unrelated (n = 20), and haploidentical (n = 11) donors. The median CD34 cell dose was 10.2 × 10/kg (range, 4.54 to 20 × 10/kg), and the median TCRαβ cell dose was 2.53 × 10/kg (range, 0 to 44.9 × 10/kg). Conditioning was myeloablative with either busulfan or total body irradiation, cyclophosphamide, and thiotepa. Thirty-three patients also received rabbit antithymocyte globulin. No prophylactic post-transplantation immune suppression was routinely given. Forty-three patients received rituximab on day +1 for recipient positive Epstein-Barr virus serology. Forty-nine patients (96%) engrafted with a median time to neutrophil recovery of 13 days (range, 8 to 30 days). Thirty-seven patients (73%) are alive at a median follow-up of 25 months (range, 6 to 50 months). Nine patients (18%) developed grade II-IV acute graft-versus-host disease (GVHD), and 5 patients (11%) developed extensive chronic GVHD. Twenty-six patients (51%) experienced viral reactivation. T cell reconstitution was rapid with significant numbers of CD3, CD4, and CD8 T cells present on first assessment at 4 months post-HCT, and significant numbers of naïve CD4 T cells were present by 8 months post-HCT. Chronic GVHD was associated with delayed T cell recovery; however, T cell reconstitution was not affected by underlying diagnosis, donor source, TCRαβ T cell dose, conditioning regimen, or use of antithymocyte globulin. B cell recovery mirrored T cell recovery, and i.v. Ig was discontinued at a median of 8 months (range, 4 to 22 months) post-HCT in patients alive and relapse-free at last follow-up. Immune reconstitution is rapid following TCRαβ/CD19-depleted HCT in pediatric patients with hematologic malignancies. Donor graft source, haploidentical or unrelated, did not affect immune reconstitution. Viral reactivation is common in the first 100 days post-HCT, indicating that improved T cell defense is needed in the early post-HCT period.

Unrelated donor (URD) hematopoietic stem cell transplant (HSCT) is associated with an increased risk of severe graft-versus-host disease (GVHD). TCRαβ/CD19 depletion may reduce this risk, whereas maintaining graft-versus-leukemia. Outcome data with TCRαβ/CD19 depletion generally describe haploidentical donors, with relatively few URDs. We hypothesized that TCRαβ/CD19-depletion would attenuate the risks of GVHD and relapse for URD HSCT. Sixty pediatric and young adult (YA) patients with hematologic malignancies who lacked a matched-related donor were enrolled at 2 large pediatric transplantation centers between October 2014 and September 2019. All patients with acute leukemia had minimal residual disease testing, and DP typing was available for 77%. All patients received myeloablative total body irradiation- or busulfan-based conditioning with no posttransplant immune suppression. Engraftment occurred in 98%. Four-year overall survival was 69% (95% confidence interval [CI], 52%-81%), and leukemia-free survival was 64% (95% CI, 48%-76%), with no difference between lymphoid and myeloid malignancies (P = .6297 and P = .5441, respectively). One patient (1.7%) experienced primary graft failure. Relapse occurred in 11 patients (3-year cumulative incidence, 21%; 95% CI, 11-34), and 8 patients (cumulative incidence, 15%; 95% CI, 6.7-26) experienced nonrelapse mortality. Grade III to IV acute GVHD was seen in 8 patients (13%), and 14 patients (26%) developed chronic GVHD, of which 6 (11%) had extensive disease. Nonpermissive DP mismatch was associated with higher likelihood of acute GVHD (odds ratio, 16.50; 95% CI, 1.67-163.42; P = .0166) but not with the development of chronic GVHD. URD TCRαβ/CD19-depleted peripheral HSCT is a safe and effective approach to transplantation for children/YAs with leukemia. This trial was registered at www.clinicaltrials.gov as #NCT02323867.

<p><strong>BACKGROUND AND OBJECTIVES: </strong>Acute kidney injury (AKI) is nearly universally associated with worse outcomes, especially among children after hematopoietic stem cell transplant (HCT). Our objective was to examine urinary immune biomarkers of AKI after HCT to provide insights into novel mechanisms of kidney injury in this population. Studying patients undergoing allogeneic (HCT) provides a unique opportunity to examine immune markers of AKI because the risk of AKI is high and the immune system newly develops after transplant.</p>

<p><strong>DESIGN, SETTING, PARTICIPANTS: </strong>Children (&gt;2 years old) and young adults undergoing their first allogeneic HCT and enrolled in a prospective, observational cohort study at two large children's hospitals had urine collected pre-HCT and monthly for the first 4 months after HCT. Urine samples at each monthly time point were assayed for 8 immune-related biomarkers. AKI was defined as a 1.5-fold increase in the monthly serum creatinine value which was recorded ±1 day from when the research urine sample was obtained, as compared to the pre-HCT baseline. Generalized estimating equation regression analysis evaluated the association between the monthly repeated measures (urinary biomarkers and AKI).</p>

<p><strong>RESULTS: </strong>A total of 176 patients were included from two pediatric centers. Thirty-six subjects from one center were analyzed as a discovery cohort and the remaining 140 subjects from the second center were analyzed as a validation cohort. AKI rates were 18-35% depending on the monthly time point after HCT. Urine CXCL10 and CXCL9 concentrations were significantly higher among children who developed AKI compared with children who did not (p&lt;0.01) in both cohorts. In order to gain a better understanding of the cellular source for these biomarkers in the urine, we also analyzed in vitro expression of CXCL10 and CXCL9 in kidney cell lines after stimulation with interferon-gamma and interferon-alpha. HEK293-epithelial kidney cells demonstrated interferon-induced expression of CXCL10 and CXCL9, suggesting a potential mechanism driving the key finding.</p>

<p><strong>CONCLUSIONS: </strong>CXCL10 and CXCL9 are associated with AKI after HCT and are therefore promising biomarkers to guide improved diagnostic and treatment strategies for AKI in this high-risk population.</p>

<p><strong>BACKGROUND: </strong>BK polyomavirus (BKPyV) is associated with symptomatic hemorrhagic cystitis after hematopoietic cell transplantation (HCT). Little is known about the host immune response, effectiveness of antiviral treatment, or impact of asymptomatic replication on long-term kidney function.</p>

<p><strong>METHODS: </strong>In children and young adults undergoing allogeneic HCT, we quantified BKPyV viruria and viremia (pre-HCT and at months 1-4, 8, 12, and 24 post-HCT) and tested associations of peak viremia ≥10 000 or viruria ≥109 copies/mL with estimated kidney function (eGFR) and overall survival for two years post-transplant. We examined factors associated with viral clearance by month 4 including BKPyV-specific T cells by enzyme-linked immune absorbent spot (ELISPOT) at month 3 and cidofovir use.</p>

<p><strong>RESULTS: </strong>We prospectively enrolled 193 participants (median age 10 years). 18% had viremia ≥10 000 copies/mL, and 45% had viruria ≥109 copies/mL in the first three months post-HCT. Among the 147 participants without cystitis (asymptomatic), 58 (40%) had any viremia. In the entire cohort and asymptomatic subset, viremia ≥10 000 copies/mL was associated with a lower creatinine/cystatin C eGFR two years post-HCT. Viremia ≥10 000 copies/mL was associated with a higher risk of death (adjusted hazard ratio, 2.2; 95% confidence interval, 1.1-4.2). Clearing viremia was associated with detectable BKPyV-specific T cells and viremia &lt;10 000 copies/mL, but not cidofovir exposure.</p>

<p><strong>CONCLUSIONS: </strong>Screening for BKPyV viremia after HCT identifies asymptomatic patients at risk for kidney disease and reduced survival. These data suggest potential changes to clinical practice, including prospective monitoring for BKPyV viremia to test virus-specific T cells to prevent or treat BKPyV replication.</p>

<p>Most children who may benefit from stem cell transplantation lack matched related donors. Alternative donor transplantations with unrelated (URD) or partially matched related donors (PMRD) carry increased risks of graft-versus-host-disease (GVHD) and mortality compared to matched related donor transplants. We hypothesized a strategy of partial CD3/CD19-depletion for URD or PMRD peripheral stem cell transplantation (PSCT) would attenuate risks of GVHD and mortality. We enrolled 84 pediatric patients with hematologic malignancies at the Children's Hospital of Philadelphia and the Children's Hospital of Wisconsin between April 2005 and February 2015 (NCT00579124: https://clinicaltrials.gov/ct2/show/NCT00579124; NCT01071226: https://clinicaltrials.gov/ct2/show/NCT01071226). Two (2.4%) experienced primary graft failure. Relapse occurred in 23 patients (27.4%; cumulative incidence 26.3%), and 17 patients (20.2%) experienced non-relapse mortality (NRM). Grade III-IV acute GVHD was observed in 18 patients (21.4%), and chronic GVHD was observed and graded as limited in 24 (35.3%) and extensive in 8 (11.7%). Three-year OS was 61.8% (95% CI 50.2 -71.4%) and EFS 52.0% (95% CI 40.3 - 62.4%). Age ≥15 years was associated with decreased OS (p=0.05) and EFS (p=0.05). Relapse was more common in children in second complete remission (p=0.03). Partially CD3-depleted alternative donor PSCT NRM, OS, and EFS compare favorably with previously published studies of T cell-replete PSCT. Historically, T cell-replete PSCTs have had a high ratio of extensive compared to limited chronic GVHD, which may explain the comparatively low relapse and NRM rates in our study despite similar overall rates of chronic GVHD. Partial T cell-depletion may expand donor options for children with malignant transplant indications lacking matched related donors by mitigating but not eliminating chronic GVHD.</p>

<p><strong>BACKGROUND: </strong>Relapsed acute lymphoblastic leukemia (ALL) is difficult to treat despite the availability of aggressive therapies. Chimeric antigen receptor-modified T cells targeting CD19 may overcome many limitations of conventional therapies and induce remission in patients with refractory disease.</p>

<p><strong>METHODS: </strong>We infused autologous T cells transduced with a CD19-directed chimeric antigen receptor (CTL019) lentiviral vector in patients with relapsed or refractory ALL at doses of 0.76×10(6) to 20.6×10(6) CTL019 cells per kilogram of body weight. Patients were monitored for a response, toxic effects, and the expansion and persistence of circulating CTL019 T cells.</p>

<p><strong>RESULTS: </strong>A total of 30 children and adults received CTL019. Complete remission was achieved in 27 patients (90%), including 2 patients with blinatumomab-refractory disease and 15 who had undergone stem-cell transplantation. CTL019 cells proliferated in vivo and were detectable in the blood, bone marrow, and cerebrospinal fluid of patients who had a response. Sustained remission was achieved with a 6-month event-free survival rate of 67% (95% confidence interval [CI], 51 to 88) and an overall survival rate of 78% (95% CI, 65 to 95). At 6 months, the probability that a patient would have persistence of CTL019 was 68% (95% CI, 50 to 92) and the probability that a patient would have relapse-free B-cell aplasia was 73% (95% CI, 57 to 94). All the patients had the cytokine-release syndrome. Severe cytokine-release syndrome, which developed in 27% of the patients, was associated with a higher disease burden before infusion and was effectively treated with the anti-interleukin-6 receptor antibody tocilizumab.</p>

<p><strong>CONCLUSIONS: </strong>Chimeric antigen receptor-modified T-cell therapy against CD19 was effective in treating relapsed and refractory ALL. CTL019 was associated with a high remission rate, even among patients for whom stem-cell transplantation had failed, and durable remissions up to 24 months were observed. (Funded by Novartis and others; CART19 ClinicalTrials.gov numbers, NCT01626495 and NCT01029366.).</p>

<p>The rising incidence of pediatric obesity may significantly affect bone marrow transplantation (BMT) outcomes. We analyzed outcomes in 3687 children worldwide who received cyclophosphamide-based BMT regimens for leukemias between 1990 and 2007. Recipients were classified according to age-adjusted body mass index (BMI) percentiles as underweight (UW), at risk of UW (RUW), normal, overweight (OW), or obese (OB). Median age and race were similar in all groups. Sixty-one percent of OB children were from the United States/Canada. Three-year relapse-free and overall survival ranged from 48% to 52% (P = .54) and 55% to 58% (P = .81) across BMI groups. Three-year leukemia relapses were 33%, 33%, 29%, 25%, and 21% in the UW, RUW, normal, OW, and OB groups, respectively (P &lt; .001). Corresponding cumulative incidences for transplant-related mortality (TRM) were 18%, 19%, 21%, 22%, and 28% (P &lt; .01). Multivariate analysis demonstrated a decreased risk of relapse compared with normal BMI (relative risk [RR] = 0.73; P &lt; .01) and a trend toward higher TRM (RR = 1.28; P = .014). BMI in children is not significantly associated with different survival after BMT for hematologic malignancies. Obese children experience less relapse posttransplant compared with children with normal BMI; however, this benefit is offset by excess in TRM.</p>