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Background Effective therapeutic agents for the treatment of COVID-19 have been investigated since the onset of the pandemic. Monoclonal antibodies targeting the spike protein of SARS-CoV-2 have been developed for treatment of mild or moderate COVID disease in high-risk populations. Despite widespread use in the adult population, data are limited on the safety and efficacy of monoclonal antibody infusions in the adolescent and young adult population. Methods Patients who received bamlanivimab, bamlanivimab-etesevimab, casirivimab-imdevimab, or sotrovimab for treatment of mild COVID disease at Cincinnati Children’s Hospital Medical Center from 5/1/2020 through 3/1/2022 were identified retrospectively. In accordance with the FDA EUA, patients were eligible for monoclonal antibody administration if they were ≥12 years of age, weighed ≥40kg, and were at high risk of progressing to severe disease or hospitalization. Results Ninety-four patients received monoclonal antibody therapy, of which 14 (13.5%) received either bamlanivimab or bamlanivimab-etesevimab, 54 (51.9%) received casirivimab-imdevimab, and 26 (25%) received sotrovimab. Ten patients (10.6%) experienced one or more adverse events. Of those, 2 (14.3%) received either bamlanivimab or bamlanivimab-etesivimab, 7 (12.9%) received casirivimab-imdevimab, and 1 (3.8%) received sotrovimab. Most common symptoms include rash, nausea, and throat irritation (table R1), the majority (90%) of which were mild, either self-resolving with infusion cessation (60%) or persistent but requiring no medical intervention (30%) (table R2). Of the patients who experienced adverse events, only 1 (10%) received medical intervention - epinephrine. No life-threatening events or deaths occurred. Within 90 days of receiving a monoclonal antibody, 15 patients (15.9%) required additional medical care for ongoing COVID symptoms (table R3). Eight (53.3%) of these were either hospitalized or received escalation of care while already in the hospital. Table R1. Infusion-related adverse events. Of note, several patients had more than one symptom. Table R2. Classification of adverse events by grade and monoclonal antibody. Grade I events are defined as mild and generally not bothersome. Grade II events are defined as moderate: bothersome, but not dangerous. Grade III events are defined as medically significant, but not immediately life-threatening, and often require medical intervention. Table R3. Patients who required additional medical care for ongoing COVID-19 symptoms within 90 days of receiving a monoclonal antibody. Conclusion Overall, monoclonal antibodies are safe, largely well-tolerated COVID-19 therapies in high-risk adolescent and young adult populations. Disclosures Grant Schulert, MD, PhD, Novartis: Advisor/Consultant Paul Spearman, MD, CyanVac: Grant/Research Support|Meissa Vaccines: Grant/Research Support Grant C. Paulsen, MD, AstraZeneca: Grant/Research Support|Moderna: Grant/Research Support|Pfizer: Grant/Research Support Lara A. Danziger-Isakov, MD, Ansun BioPharma: Contracted clinical research|Astellas: Contracted clinical research|GSK: Advisor/Consultant|Merck: Advisor/Consultant|Merck: Contracted clinical research|Pfizer: Contracted clinical research|Takeda: Grant/Research Support|Takeda: Contracted clinical research|Viracor: Grant/Research Support.

Infection with adenoviruses is a common and significant complication in pediatric patients after allogeneic hematopoietic stem cell transplantation. Treatment options with traditional antivirals are limited by poor efficacy and significant toxicities. T-cell reconstitution is critical for the management of adenoviral infections, but it generally takes place months after transplantation. Ex vivo–generated virus-specific T cells (VSTs) are an alternative approach for viral control and can be rapidly generated from either a stem cell donor or a healthy third-party donor. In the context of a single-center phase 1/2 clinical trial, we treated 30 patients with a total of 43 infusions of VSTs for adenoviremia and/or adenoviral disease. Seven patients received donor-derived VSTs, 21 patients received third-party VSTs, and 2 received VSTs from both donor sources. Clinical responses were observed in 81% of patients, with a complete response in 58%. Epitope prediction and potential epitope identification for common HLA molecules helped elucidate HLA restriction in a subset of patients receiving third-party products. Intracellular interferon-γ expression in T cells in response to single peptides and response to cell lines stably transfected with a single HLA molecule demonstrated HLA-restricted CD4+ T-cell response, and these results correlated with clinical outcomes. Taken together, these data suggest that VSTs are a highly safe and effective therapy for the management of adenoviral infection in immunocompromised hosts. The trials were registered at www.clinicaltrials.gov as #NCT02048332 and #NCT02532452.

We report results of a phase II study of maraviroc to prevent acute graft versus host disease (GVHD) in children undergoing allogeneic hematopoietic stem cell transplant (HSCT). Oral maraviroc was added to standard GVHD prophylaxis of a calcineurin inhibitor with either mycophenolate mofetil, methotrexate or steroids from day −3 until day +30 after HSCT. Maraviroc trough levels were analyzed on day 0, +7, 14, and 21. We assessed functional CCR5 blockade by our previously described pharmacodynamic assay. In total, 17 patients were enrolled prospectively. No patient had liver GVHD by day +100. Four patients developed gastrointestinal (GI) GVHD (Grade II upper GI GVHD n = 2, grade III lower GI GVHD n = 2). No adverse effects of maraviroc were observed. Seven patients discontinued maraviroc at a median of day +14 (range day +1–day +29) due to study rules regarding hepatotoxicity (n = 5), renal function decline (n = 1) and withdrawal from study (n = 1). Maraviroc administration led to CCR5 inhibition but was limited by study rules defining hepatotoxicity, leading to frequent drug discontinuation. We cannot comment on the efficacy of maraviroc with our data but speculate that it could have a role in prevention of acute GI GVHD, with adequate compliance.

We have previously reported that a peripheral blood absolute CD38brightCD8+ effector memory T cell (TEM) population expansion of >35 cells/µL predicts the development of acute graft-versus-host disease (GVHD). We hypothesized that these T cells are activated, proliferating, and cytotoxic trafficking cells that are not a response to viral reactivation and may be involved in acute GVHD. We characterized peripheral blood T cell populations at the time of maximum CD38brightCD8+ TEM expansion in patients from our originally reported pediatric allogeneic hematopoietic cell transplantation recipient cohort. Samples were incubated with fluorochrome-conjugated antibodies directed against CD3, CD8, CD38, HLA-DR (T cell activation), Ki-67 (T cell proliferation), granzyme B (marker of cytotoxic T cells), CLA (skin trafficking), CCR5 (visceral trafficking), and CXCR6 (liver trafficking). We also incubated samples with Epstein-Barr virus (EBV) and cytomegalovirus (CMV) peptide pools and measured IFN-γ production by flow cytometry and performed EBV and CMV tetramer staining. Higher median proportions of cell expression of HLA-DR, Ki-67, granzyme B, CLA, CCR5, and CXCR6 were observed for CD38brightCD8+ T cells compared with CD38nonbrightCD8+ T cells in patients with acute GVHD (P

Background: The contribution of the gastrointestinal tract microbiome to outcomes after allogeneic hematopoietic cell transplantation (HCT) is increasingly recognized. Investigations of larger pediatric cohorts aimed at defining the microbiome state and associated metabolic patterns pre-transplant are needed. Methods: We sought to describe the pre-transplant stool microbiome in pediatric allogenic HCT patients at four centers. We performed shotgun metagenomic sequencing and untargeted metabolic profiling on pre-transplant stool samples. Samples were compared with normal age-matched controls and by clinical characteristics. We then explored associations between stool microbiome measurements and metabolite concentrations. Results: We profiled stool samples from 88 pediatric allogeneic HCT patients, a median of 4 days before transplant. Pre-transplant stool samples differed from healthy controls based on indices of alpha diversity and in the proportional abundance of specific taxa and bacterial genes. Relative to stool from healthy patients, samples from HCT patients had decreased proportion of Bacteroides, Ruminococcaeae and genes involved in butyrate production, but were enriched for gammaproteobacterial species. No systematic differences in stool microbiome or metabolomic profiles by age, transplant indication or hospital were noted. Stool metabolites demonstrated strong correlations with microbiome composition. Discussion: Stool samples from pediatric allogeneic HCT patients demonstrate substantial dysbiosis early in the transplant course. As microbiome disruptions associate with adverse transplant outcomes, pediatric-specific analyses examining longitudinal microbiome and metabolome change are imperative to identify causal associations and to inform rational design of interventions.

Background Progressive multifocal leukoencephalopathy (PML) is a progressive and generally fatal demyelinating neurological disease that occurs in profoundly immunocompromised patients due to infection with the human polyomavirus JC virus (JCPyV). Treatment options are limited and are largely focused on restoring T-cell immunity and outcomes are historically poor. Control of JCPyV in the setting of an immunocompromised patient by adoptive transfer of third-party virus specific T-cells (VSTs) has been described in a small number of cases. Objective To investigate treatment response and outcomes in recipients of hematopoietic stem cell transplant (HSCT) with PML treated with third-party VSTs directed against BK virus, a highly homologous polyoma virus that shares immunogenic epitopes with JCPyV. Study Design Retrospective chart review was performed on four patients who received VSTs for the treatment of PML at Cincinnati Children's Hospital Medical Center since 2019 Results VSTs were safely administered with no cases of graft-vs-host disease and no infusion reactions. One patient, who was treated almost immediately after diagnosis, was able to clear JCPyV from blood and CSF with resultant stabilization of neurologic decline. Interferon-gamma ELISpot demonstrated virus specific T-cells in the peripheral blood following infusion. Response was maintained through repeat infusions. Three other patients, all of whom had a longer delay between diagnosis and infusion, had progressive neurologic decline despite varying degree of improvement in viral load. Conclusion PML is a rare but often fatal complication following HSCT for which few treatment options are available. BK directed, JCPyV cross-reactive VSTs are a safe and viable therapeutic option and prompt administration should be considered after a diagnosis of PML is made. Key points • Virus specific T cells targeting JCPyV virus are safe with no infusional toxicity or de-novo graft versus host disease. • Virus specific T-cells have evidence of efficacy in some cases of PML, but further studies are needed to determine factors that will optimize response.

Neutropenic diets were adopted as a way to decrease the infection risks in immunocompromised individuals, but these diets result in significant restrictions in the variety and types of foods an individual may consume. We used a controlled before-and-after study design in consecutive pediatric and young adult patients who underwent hematopoietic stem cell transplant at our center between January 1, 2014, and December 31, 2014. From January through June, all patients were placed on a traditional neutropenic diet; on July 1, we liberalized the bone marrow transplant (BMT) diet to a modified BMT diet. We compared the incidence of bloodstream infections in the first 100 days post-transplant, incidence of norovirus in the first 100 days, total parenteral nutrition days through day 100, incidence of grade 3 to 4 graft-versus-host disease at day 100, gastrointestinal graft-versus-host disease (any stage), and 100-day overall survival. In addition, we administered an investigator-created survey to evaluate food cravings, nausea, diet limitations, and subjective quality of life. In total, 102 patients underwent hematopoietic stem cell transplant during the study period. Forty-nine (48%) received the neutropenic diet and 53 (52%) the BMT diet. Other than more males receiving the neutropenic diet (67% versus 47%, P = 0.05), there were no statistical demographic and outcome differences between the 2 groups. Additionally, 46 subjects (45%) completed the investigator-created questionnaire. There was no difference in the perceived food cravings, nausea, diet limitations, and subjective quality of life between the 2 cohorts. These data demonstrate noninferiority of the modified BMT diet over the traditional neutropenic diet. We believe the food safety-based diet offers a greater variety of food, which may assist in the transition to a normal diet.

Hematopoietic stem cell transplantation (HSCT) is a therapeutic option for many nonmalignant disorders (NMD) and is curative or prevents disease progression. Reduced-intensity conditioning (RIC) in HSCT for NMD may reduce regimen-related acute toxicities and late complications. Myeloablation is often replaced by immune suppression in RIC regimens to support donor engraftment. The pace of immune reconstitution after immune suppression by RIC regimens is influenced by agents used, donor source, and graft-versus-host disease prophylaxis/treatment. In a multicenter trial (NCT 00920972) of HSCT for NMD, a RIC regimen consisting of alemtuzumab, fludarabine, and melphalan was substituted for myeloablation. Alemtuzumab was administered early (days −21 to −19) to mitigate major lymphodepletion of the incoming graft and the risk of graft rejection. Immune reconstitution and infectious complications were prospectively monitored for 1-year post-HSCT. Seventy-one patients met inclusion criteria for this report and received marrow or peripheral blood stem cell transplants. Immune reconstitution and infections are reported for related donor (RD) and unrelated donor (URD) transplants at 3 time-points (100days, 6 months, and 1 year post-HSCT). Natural killer cell recovery was rapid, and numbers normalized in both cohorts by day +100. Mean CD3, CD4, and CD8 T-lymphocyte numbers normalized by 6 months after RD HSCT and by 1 year in the URD group. CD4 and CD8 T-lymphocyte counts were significantly higher in patients who received RD HSCT at 6 months and at 1 year, respectively, post-HSCT compared with patients who received URD HSCT. The pace of CD19 B-cell recovery was markedly different between RD and URD cohorts. Mean B-cell numbers were normal by day 100 after RD HSCT but took 1 year post-HSCT to normalize in the URD cohort. Despite these differences in immune reconstitution, the timing and nature of infections did not differ between the groups, presumably because of comparable T-lymphocyte recovery. Immune reconstitution occurred at a faster pace than in prior reports using RIC with T-cell depletion. The incidence of infections was similar for both cohorts and occurred most frequently in the first 100days post-HSCT. Viral and fungal infections occurred at a lower incidence in this cohort, with "early" alemtuzumab compared with regimens administering serotherapy in the peritransplantation period. Patients were susceptible to bacterial infections primarily in the first 100days irrespective of donor source and had no increase in mortality from the same. The overall mortality rate from infections was 1.4% at 1 year. Close monitoring and prophylaxis against bacterial infections in the first 100days post-HSCT is necessary but is followed by robust immune reconstitution, especially in the T-cell compartment.

BACKGROUND Ruxolitinib, a JAK1/2 inhibitor, is used to treat chronic graft-versus-host-disease (cGVHD) in adult allogeneic hematopoietic stem cell transplant patients, but experience in children is limited, perhaps due to lack of pediatric dosing information. In this report we describe our pediatric and young adult dosing strategy experience in cGVHD. METHODS Ruxolitinib was administered orally at 5mg twice daily for children ≥25kg or 2.5mg twice daily if

We have previously demonstrated a 11% incidence of post-transplant de novo thyroid disease, even with a radiation-free RIC regimen. Following the enactment of a universal late effects screening program at our institution, we compared the outcomes of 108 pediatric hematopoietic stem cell transplant recipients after a RIC regimen (n = 33) to those after a MAC regimen (n = 75) during the same time period. Overall, 10% of subjects developed thyroid dysfunction after HSCT, with a median follow-up of 669 days. Seven subjects had primary hypothyroidism prior to HSCT. Of the thirty-one subjects who received RIC, one (3.2%) developed a new thyroid disorder, compared to the nine of sixty-nine (13.0%) subjects who received MAC (p = .167). No significant associations were seen with donor type, graft-vs.-host disease, or total body irradiation. Nine of the 10 subjects who developed thyroid disease after transplant were asymptomatic. Continued follow-up of this contemporary cohort will further delineate risk factors for post-transplant-associated thyroid dysfunction and better inform discussions of transplant-associated sequelae.

PURPOSE Severe (grade 3-4) acute graft-versus-host disease (AGVHD) is a major cause of death after unrelated-donor (URD) hematopoietic cell transplant (HCT), resulting in particularly high mortality after HLA-mismatched transplantation. There are no approved agents for AGVHD prevention, underscoring the critical unmet need for novel therapeutics. ABA2 was a phase II trial to rigorously assess safety, efficacy, and immunologic effects of adding T-cell costimulation blockade with abatacept to calcineurin inhibitor (CNI)/methotrexate (MTX)-based GVHD prophylaxis, to test whether abatacept could decrease AGVHD. METHODS ABA2 enrolled adults and children with hematologic malignancies under two strata: a randomized, double-blind, placebo-controlled stratum (8/8-HLA-matched URD), comparing CNI/MTX plus abatacept with CNI/MTX plus placebo, and a single-arm stratum (7/8-HLA-mismatched URD) comparing CNI/MTX plus abatacept versus CNI/MTX CIBMTR controls. The primary end point was day +100 grade 3-4 AGVHD, with day +180 severe-AGVHD-free-survival (SGFS) a key secondary end point. Sample sizes were calculated using a higher type-1 error (0.2) as recommended for phase II trials, and were based on predicting that abatacept would reduce grade 3-4 AGVHD from 20% to 10% (8/8s) and 30% to 10% (7/8s). ABA2 enrolled 142 recipients (8/8s, median follow-up = 716 days) and 43 recipients (7/8s, median follow-up = 708 days). RESULTS In 8/8s, grade 3-4 AGVHD was 6.8% (abatacept) versus 14.8% (placebo) ( P = .13, hazard ratio = 0.45). SGFS was 93.2% (CNI/MTX plus abatacept) versus 82% (CNI/MTX plus placebo, P = .05). In the smaller 7/8 cohort, grade 3-4 AGVHD was 2.3% (CNI/MTX plus abatacept, intention-to-treat population), which compared favorably with a nonrandomized matched cohort of CNI/MTX (30.2%, P < .001), and the SGFS was better (97.7% v 58.7%, P < .001). Immunologic analysis revealed control of T-cell activation in abatacept-treated patients. CONCLUSION Adding abatacept to URD HCT was safe, reduced AGVHD, and improved SGFS. These results suggest that abatacept may substantially improve AGVHD-related transplant outcomes, with a particularly beneficial impact on HLA-mismatched HCT.

PURPOSE: A need exists for reduced toxicity conditioning regimens that offer less toxicity while maintaining myeloablation, especially for primary immune deficiencies where myeloablation or high donor myeloid chimerism is required to achieve cure. We adapted a busulfan and fludarabine regimen by Gungor et al. for children and young adults undergoing allogeneic HCT for non-CGD primary immune deficiencies requiring myeloablation or high donor myeloid chimerism, and herein report our experience. METHODS: We retrospectively reviewed records of 41 consecutive patients who underwent allogeneic HCT for Wiskott-Aldrich syndrome (n = 12), primary HLH/XLP (n = 10), CD40L deficiency (n = 7), or other (n = 12) primary immune deficiencies with a conditioning regimen containing pharmacokinetic-guided busulfan dosing which achieved a cumulative AUC between 57 and 74 mg/L × h (65–80% of conventional myeloablative exposure), along with fludarabine and alemtuzumab or anti-thymocyte globulin at 3 transplant centers between 2014 and 2019. RESULTS: Forty-one patients underwent a first (n = 33) or second (n = 8) allogeneic HCT. Median age was 2.3 years (range, 0.3 years–19.8 years). All but one patient (97.5%) achieved neutrophil recovery at a median of 14 days (range, 11–34 days). One patient developed sinusoidal obstruction syndrome and two patients developed diffuse alveolar hemorrhage. Four patients developed grades II–IV acute GVHD. Three patients developed chronic GVHD. One-year overall survival was 90% (95% confidence interval [CI] 81–99%) and event-free survival was 83% (95% CI 71–94%). CONCLUSIONS: Our experience suggests that a reduced toxicity busulfan-fludarabine regimen offers low toxicity, low incidence of grades 2–4 GVHD, durable myeloid engraftment, and excellent survival, and may be considered for a variety of primary immune deficiencies where myeloablative HCT is desired.

BACKGROUND We hypothesized that the addition of 4 doses of abatacept to our standard acute graft-versus-host disease (GVHD) prophylaxis would reduce the incidence of day +100 severe acute GVHD in children with transfusion-dependent beta-thalassemia major undergoing a myeloablative allogeneic hematopoietic stem cell transplant (HSCT), without impacting engraftment. METHODS Twenty-four children with beta-thalassemia major received abatacept at a dose of 10 mg/kg intravenously on days -1, +5, +14, and +28 after HSCT in addition to calcineurin inhibitors and methylprednisolone. Outcomes were compared to 8 beta-thalassemia patients who received standard acute GVHD prophylaxis. RESULTS There was no difference in engraftment between the 2 groups. No patient had grades III-IV acute GVHD by day +100 in the abatacept cohort compared with 50% in the standard acute GVHD prophylaxis group (P = 0.001). Viral reactivation occurred in 5 children in the standard acute GVHD cohort and in 20 children in the abatacept cohort (P = 0.2). Thalassemia-free survival after HSCT was 100% in the abatacept cohort compared to 62.5% in the standard cohort at last follow-up (P = 0.007). CONCLUSIONS Adding abatacept to our routine GVHD prophylaxis reduced the incidence of day +100 severe acute GVHD without impacting engraftment or survival.

Key Points The use of terminal complement blockade is compatible with virus-specific T-cell (VST) expansion and clinical effectiveness. VST and complement-blocking agent concurrent therapy may be safely used in patients with thrombotic microangiopathy and viral infections.

Interferon &gamma, (IFN-&gamma, ) was shown to be a macrophage activating factor already in 1984. Consistently, inborn errors of IFN-&gamma, immunity underlie Mendelian Susceptibility to Mycobacterial Disease (MSMD). MSMD is characterized by genetic predisposition to disease caused by weakly virulent mycobacterial species. Paradoxically, macrophages from patients with MSMD were little tested. Here, we report a disease modeling platform for studying IFN-&gamma, related pathologies using macrophages derived from patient specific induced pluripotent stem cells (iPSCs). We used iPSCs from patients with autosomal recessive complete- and partial IFN-&gamma, R2 deficiency, partial IFN-&gamma, R1 deficiency and complete STAT1 deficiency. Macrophages from all patient iPSCs showed normal morphology and IFN-&gamma, independent functionality like phagocytic uptake of bioparticles and internalization of cytokines. For the IFN-&gamma, dependent functionalities, we observed that the deficiencies played out at various stages of the IFN-&gamma, pathway, with the complete IFN-&gamma, R2 and complete STAT1 deficient cells showing the most severe phenotypes, in terms of upregulation of surface markers and induction of downstream targets. Although iPSC-derived macrophages with partial IFN-&gamma, R1 and IFN-&gamma, R2 deficiency still showed residual induction of downstream targets, they did not reduce the mycobacterial growth when challenged with Bacillus Calmette&ndash, Gu&eacute, rin. Taken together, we report a disease modeling platform to study the role of macrophages in patients with inborn errors of IFN-&gamma, immunity.

Children with ataxia telangiectasia (AT), a primary immunodeficiency caused by mutations in ATM, which is critical for repairing DNA defects, are at risk for the development of hematologic malignancy, frequently driven by infection with Epstein-Barr virus (EBV). Conventional chemotherapy is poorly tolerated by patients with AT, with excessive toxicity even when doses are reduced. Here, we report on two patients with AT and EBV-positive neoplasms who were treated with EBV-targeted viral-specific T cells (VST). One patient had a prolonged complete response to VSTs while the other had a partial response. Therapy was well tolerated without infusion toxicity or graft-versus-host disease.

cGVHD is a significant cause of morbidity and mortality after transplant. Ibrutinib has been studied as treatment for cGVHD in the adult population. Pediatric dosing and safety of ibrutinib are unknown. We conducted a retrospective review on the use of ibrutinib in 22 children with cGVHD at Cincinnati Children's Hospital Medical Center. All patients received a dose of 250 mg/m2 orally, once daily. Responses were measured at 6 months after drug initiation using the 2014 NIH consensus panel response criteria. Twenty-two patients of median age 13.5 years received ibrutinib. cGVHD grades were severe (n = 15), moderate (n = 6), and mild (n = 1). Eight patients stopped ibrutinib prior to 3 months due to adverse events or death and could not be evaluated for 6-month response. Of the 14 evaluable patients, 12 achieved a partial response at 6 months and two patients had progressive disease. Seven evaluable patients with lung involvement had stable lung function at 6 months. One patient had EBV reactivation, and one patient developed pneumococcal sepsis despite appropriate prophylaxis while on ibrutinib therapy. No fungal infections occurred while on ibrutinib. Adverse events leading to discontinuation included recurrent fevers without a source, extensive bruising, oral bleeding, gastrointestinal distress, lower GI bleeding, dizziness, elevated transaminases, and pneumococcal sepsis. Ibrutinib administration of 250 mg/m2 oral daily shows promising responses in pediatric cGVHD. Pediatric-focused pharmacokinetic-directed studies are needed to establish optimal dosing and define efficacy in children.

Veno-occlusive disease (VOD) is a serious complication of hematopoietic stem cell transplant (HSCT), with high mortality in severe cases and until recently very limited therapeutic options consisting largely of supportive care. Defibrotide was recently approved in the United States for the treatment of severe VOD in patients with renal or pulmonary dysfunction after HSCT. Our group previously published on the use of high-dose methylprednisolone (500 mg/m2 per dose every 12 hours for 6 doses) in patients with VOD, showing good success. A small subset of these individuals were also treated with defibrotide, but additional studies using the combination of high-dose methylprednisolone and defibrotide for the treatment of VOD are lacking. We present a single-institution retrospective chart review of 15 HSCT patients with VOD treated with the combination of high-dose methylprednisolone and defibrotide. VOD developed at a median of 17 days post-HSCT, and combination therapy was initiated within 1 day of VOD diagnosis. Twelve of 15 patients (80%) had multiorgan failure. Our single-center experience using both high-dose methylprednisolone and defibrotide showed a day +100 survival rate of 73% and an overall VOD complete resolution rate of 66.7%, higher than the rates reported in the recent literature using defibrotide alone (40% to 50% day +100 overall survival). These data suggest that the combination of high-dose steroids and defibrotide may be superior to defibrotide alone and warrant further investigation.

Introduction: Sickle cell disease (SCD) is a genetic red blood cell (RBC) disorder that causes chronic hemolytic anemia, progressive organ damage, and life-threatening acute complications such as painful vaso-occlusive crises. Allogeneic hematopoietic stem cell transplant (allo-HSCT) with myeloablative conditioning remains the only curative therapy for SCD but has several limitations including low donor availability and conditioning-related toxicity. Genetic modification of autologous hematopoietic system cells (HSCs) with reduced-intensity conditioning (RIC) using a high-potency drug product may address these limitations. ARU-1801 is a gene therapy that uses a modified γ-globin lentiviral vector to produce HbF G16D within autologous CD34+ HSCs. Preclinical studies in SCD mice have shown the G16D mutation enables γ-globin G16D to bind α-globin with higher affinity; lentiviral transfer of γ-globin G16D resulted in 1.5-2x more HbF per vector copy number (VCN) compared to analogous wild-type γ-globin vector. Early studies also suggested HbF G16D may be more potent for anti-sickling than HbF, lowering reticulocyte counts in SCD mice to a greater extent at similar protein levels. We hypothesize ARU-1801 with RIC could lessen toxicities and resource utilization relative to myeloablative approaches, allowing expanded access to gene therapy for a broader group of SCD patients. Updated data from patients in the ongoing Phase 1/2 study (NCT02186418) including laboratory and clinical markers of efficacy are presented here. Methods: Adults (18-45 years old) with severe SCD (defined by recurrent vaso-occlusive events [VOE] and acute chest syndrome) were screened for eligibility. Prior to ARU-1801 drug product (DP) infusion, all patients received a single IV dose of RIC melphalan (140 mg/m 2). Endpoints included measures of safety, engraftment, VCN, hemoglobin sub-fractions, and SCD-related outcomes. Patients were weaned off transfusions 3-6 months after DP infusion. Levels of anti-sickling globins (including HbF G16D) are presented as proportions of non-transfused total hemoglobin. Results: As of 28 July 2021, four patients (mean, 26 [19-35] years old) have been treated with ARU-1801 gene therapy for SCD with three patients followed for ≥12 months post-transplant. Transient neutropenia and thrombocytopenia were the predominant adverse events, lasting a median seven days each. There have been no other serious adverse events related to chemotherapy or ARU-1801 to date. At 36 months post-transplant, Patient 1 has shown stable HbF expression (27%) and 64% F-cells. Patient 2 has maintained 14% HbF and 37% F-cells at 36 months despite lower engraftment of ARU-1801 due to renal hyperfiltration (eGFR = 200 mL/min/1.73 m 2) at time of conditioning, which resulted in lower melphalan exposure. Both patients saw marked improvements in SCD manifestations, including 93% and 85% fewer annualized VOEs, respectively, in the two years after receiving ARU-1801 gene therapy compared to two years prior. Patient 3 received ARU-1801 manufactured with several process modifications (including improvements of HSC collection timing and lentiviral production) and has maintained 36% HbF at month 15 with pancellular distribution (96% F-cells). To date, Patient 3 has had no VOEs since ARU-1801 administration, representing 100% reduction from baseline. Conclusion: Amelioration of SCD phenotype and engraftment of ARU-1801 gene-modified HSCs is possible with a single RIC dose of melphalan, as demonstrated in three patients. The first patient shows 27% HbF expression at three years, and 93% reduction in VOEs. The second patient had lower HSC engraftment due to below-target melphalan exposure (likely caused by renal hyperfiltration), with 14% HbF and 5% HbA2 at three years. Nonetheless, an 85% reduction in VOEs in Patient 2 demonstrates significant clinical benefit. Dose-adjusted melphalan has the potential to improve engraftment in SCD patients with renal hyperfiltration. Following manufacturing process improvements, the third patient has shown the highest HbF (36%) at one year, the highest F-cells (96%), and no VOEs since receiving ARU-1801. ARU-1801, with RIC melphalan conditioning, is a promising alternative to myeloablative transplants for achieving durable responses with a favorable safety profile in patients with severe SCD. Longer follow-up and additional patients will be presented. Figure 1 Figure 1. Disclosures Asnani: Avicanna Ltd.: Research Funding; Aruvant Sciences: Research Funding. Lutzko: Aruvant Sciences: Patents & Royalties: preclinical vector development. Quinn: Forma Therapeutics: Consultancy; Emmaus Medical: Research Funding; Novo Nordisk: Consultancy; Aruvant: Research Funding. Lo: Aruvant Sciences: Current Employment. Little: Aruvant Sciences: Current Employment. Dong: Aruvant Sciences: Current Employment. Malik: Aruvant Sciences: Consultancy; Forma Therapeutics: Consultancy; Aruvant Sciences: Patents & Royalties; CSL Behring: Patents & Royalties. OffLabel Disclosure: Plerixafor was used for stem cell mobilization. Melphalan was used as chemotherapy conditioning prior to autologous transplant with ARU-1801

We describe the successful treatment of a 10-month-old female with respiratory distress secondary to Coronavirus disease 2019 (COVID-19) with the nebulized investigational drug, DAS181. Therapy was well tolerated, and the patient had minimal side effects. The patient's respiratory distress and positive viral polymerase chain reaction rapidly resolved after initiation of therapy.

Background Hemophagocytic lymphohistiocytosis (HLH) is an increasingly recognized life-threatening syndrome characterized by excessive inflammation and immune dysregulation. However, little is known about HLH presenting in neonates. Methods To describe the phenotype, etiology, and efficacy of therapy for infants presenting within 28 days of birth and diagnosed with HLH prior to 90 days of life, a retrospective multi-center study was conducted identifying 13 previously unreported cases from 8 centers. A systematic literature review identified 58 additional cases that were sufficiently similar to allow pooling for meta-analysis (n=71). Results Presenting symptoms and laboratory findings of HLH were non-specific and indistinguishable from other neonatal critical illnesses. More than 85% of patients demonstrated hepatomegaly, splenomegaly, hyperferritinemia, transaminitis, hypoalbuminemia, and severe thrombocytopenia. Notably, liver dysfunction appears more common in neonatal HLH compared to published reviews of HLH cases across the age spectrum. Genetic testing was pursued in 60% of the cohort with pathogenic variants identified in a third of patients (PRF1 in 15, UNC13D in 8). Ten additional cases occurred with a family history of HLH, for a total of 46% (33/71) of cases of presumed familial HLH. Seventeen cases (24%) represented secondary HLH with an identified trigger for immune dysregulation (e.g. infection or non-HLH disease) in the absence of an HLH-associated genetic mutation or family history. Twenty-one (30%) neonatal HLH cases were of unknown etiology. Two-year survival from presentation was low at 27%, with a trend toward superior 2-year overall survival for those with secondary HLH at 65% (unknown etiology 21%, familial HLH 18%, p=0.06; Figure). Ten patients (n=6 familial HLH, n=4 unknown etiology) underwent allogeneic hematopoietic cell transplantation (HCT) at a median of 4.8 months of age. HCT was associated with improved 2-year overall survival (OS) from HLH diagnosis (78% with HCT versus 11% without HCT, p Conclusion Liver dysfunction in a severely ill neonate should prompt consideration of HLH as an etiology. Our study supports consideration of HCT for any neonate with HLH, except those with an identified trigger and absence of an HLH-associated gene mutation prompting classification as secondary HLH. Early lethality combined with superior HCT outcomes when HLH is well-controlled additionally highlight the need for novel HLH therapies to bridge to HCT. Further studies to better elucidate details of pre-HCT therapy, HCT conditioning regimens and how best to navigate multi-organ failure at HLH presentation are needed. Figure Disclosures No relevant conflicts of interest to declare.

Introduction: ARU-1801 is a gene therapy consisting of autologous CD34+ hematopoietic stem cells and progenitors (HSCPs) transduced with a lentiviral vector (LV) encoding a modified γ-globinG16D gene. Preclinical studies in SCD mice have shown that g-globinG16D binds α-globin with higher affinity; hence, the g-globinG16D LV produces 1.5-2x more HbF/vector copy number (VCN) than a g-globin LV. Preliminary studies also show greater reduction in reticulocytes in SCD mice expressing HbFG16D compared to those expressing the same level of HbF, suggesting that HbFG16D may have a more potent anti-sickling effect than HbF. We hypothesized a high potency anti-sickling globin would allow ARU-1801 to be effective with reduced intensity conditioning (RIC). RIC would result in lower toxicities and resource utilization compared to myeloablative approaches, allowing access of gene therapy to a broader group of SCD patients. We previously reported early data from patient 1 (P1) and 2 (P2) in the ongoing Phase 1/2 study (NCT02186418), who were treated with drug product (DP) from the initial ARU-1801 manufacturing process (Process I). We now present the long-term data on these patients and early data from P3, the first patient treated with our new manufacturing process (Process II). Methods: Adults with severe SCD, as defined by recurrent vaso-occlusive events (VOE) and acute chest syndrome deemed eligible were enrolled. Manufacturing process improvements in Process II included optimized timing of HSCP collection after plerixafor mobilization, LV production and improved HSCP transduction. Prior to DP infusion, all patients received a single dose of IV melphalan (140 mg/m2 BSA) and were weaned off transfusions 3-6 months after DP infusion. Patients were monitored for safety, engraftment, VCN, anti-sickling Hb (ASG) expression, and hematological and clinical manifestations of SCD. Levels of ASG (including HbFG16D) are presented as fractions of endogenous Hb. Results: As of 28 July 2020, data from 3 patients treated with ARU-1801 are available. P1 (34yr old) has HbSβ0- and P2 (24yr old) has HbSβ+ thalassemia (2-3% HbA). Both have 30 months (mo) post-transplant (PT) follow up. P3 (19yr old) has HbSS genotype with 6 mo PT follow up. ARU-1801 demonstrated a favorable safety profile with no treatment-related adverse events to date. Time to neutrophil engraftment (ANC ≥500) was 9, 7, and 7 days PT, and time to platelet recovery (Plt >50,000) was 12, 7, and 6 days PT, in P1, P2, and P3, respectively. Figure 1 shows HSPC dose, conditioning exposure and gene transfer; Figure 2 shows ASG over time. Using Process I, P1 has shown stable expression of 20% HbFG16D, 31% ASG and 31%à64% F-cells over 2.5 years, despite a low DP VCN of 0.2 and low HSPC dose of 1.4 x106 cell/kg. P2 received a higher cell dose of 7.1 x106 cell/kg with a DP VCN of 0.47 but had below target melphalan exposure, likely due to rapid clearance from hyperfiltration (GFR= 200 mL/min/1.73m2). Despite lower engraftment and HbFG16D level, P2 maintains stable total ASG of 22% at 30 mo due to a compensatory increase in HbF. Using Process II, P3 received DP of 6.8 x106 cells/kg with a VCN of 1.0, and demonstrated an engrafted VCN of 0.74, 71% F-cells and 91% F-reticulocytes at 6 mo. As P3 is being weaned off transfusions, HbFG16D is progressively rising, showing the selective advantage to HbFG16D-containing RBCs. P1 and P2 have maintained improvements in VOEs, no VOE in P3 so far (data will be presented). Conclusion: We show that engraftment of ARU-1801 and amelioration of disease is possible with RIC using IV melphalan, with persistent stable ASG expression and meaningful improvement in VOEs in P1 and P2. P1 shows stable HbFG16D and high ASG despite low, albeit stable VCN. P2 had lower HSCP engraftment, which we hypothesize was due to below target melphalan exposure. Nevertheless, significant clinical benefit was observed in P2 due to stable ASG of 22% at mo 30. It is likely that the presence of this amount of HbFG16D has provided enough ASG to prevent sickling/ineffective erythropoiesis, resulting in the preferential survival of HbF+HbFG16D-expressing RBC. Process II DP in P3 resulted in 2-4X higher engraftment of transduced HSCPs at 6 mo. Additional process enhancements are under development for future treated patients. ARU-1801, administered with RIC, holds significant promise for achieving durable responses with a favorable safety profile in patients with severe SCD. Disclosures Asnani: Aruvant Sciences: Research Funding; Avicanna Ltd.: Research Funding. Lutzko:Aruvant Sciences: Patents & Royalties: pre-clinical vector development. Lo:Aruvant Sciences: Current Employment. Little:Aruvant Sciences: Current Employment. McIntosh:Aruvant: Current Employment, Current equity holder in private company. Malik:Aruvant Sciences, Forma Therapeutics, Inc.: Consultancy; Aruvant Sciences, CSL Behring: Patents & Royalties. OffLabel Disclosure: Plerixafor - stem cell mobiliziation Melphalan - chemotherapy conditioning pre autologous transplant with ARU-1801

Vitamin A promotes development of mucosal tolerance and enhances differentiation of regulatory T cells. Vitamin A deficiency impairs epithelial integrity, increasing intestinal permeability. We hypothesized that higher vitamin A levels would reduce the risk of graft-versus-host disease (GVHD) through reduced gastrointestinal (GI) permeability, reduced mucosal injury, and reduced lymphocyte homing to the gut. We tested this hypothesis in a cohort study of 114 consecutive patients undergoing allogeneic stem cell transplant. Free vitamin A levels were measured in plasma at day 30 posttransplant. GI GVHD was increased in patients with vitamin A levels below the median (38% vs 12.4% at 100 days, P = .0008), as was treatment-related mortality (17.7% vs 7.4% at 1 year, P = .03). Bloodstream infections were increased in patients with vitamin A levels below the median (24% vs 8% at 1 year, P = .03), supporting our hypothesis of increased intestinal permeability. The GI mucosal intestinal fatty acid-binding protein was decreased after transplant, confirming mucosal injury, but was not correlated with vitamin A levels, indicating that vitamin A did not protect against mucosal injury. Expression of the gut homing receptor CCR9 on T-effector memory cells 30 days after transplant was increased in children with vitamin A levels below the median (r = -0.34, P = .03). Taken together, these data support our hypothesis that low levels of vitamin A actively promote GI GVHD and are not simply a marker of poor nutritional status or a sicker patient. Vitamin A supplementation might improve transplant outcomes.

Introduction Interprofessional Practice Model (IPM) embodies autonomy, accountability, and authority for clinicians to advocate for those they serve. Interprofessional Shared Governance (ISG) is a monthly meeting structure consisting of Point of Care Interprofessional Councils (PoC-IC), Housewide Tenets, and leadership forums. ISG supports interprofessional shared decision-making, facilitation of bi-directional communication, and collaboration between POC-IC and housewide councils. ISG influences each housewide council and PoC-IC to develop patient and family empirical outcomes that align with the strategic plan while developing leaders. Methods The Bone Marrow Transplant (BMT) unit formed an interdisciplinary PoC-IC that includes a Mentor, Operational Excellence Leaders, Chair, 6 core nursing members, and multiple interprofessional team members (Patient Care Assistant, Health Unit Coordinator, PT/OT, Nurse Practitioner, Child Life Specialist, Care Manager, Social Worker, Pharmacist, and Dietician). Members collaborate to form goals that align with the housewide direction. Mentor collaborates with the team to establish a shared decision-making process for elections and member representation. Six PoC-IC core members are responsible for attending assigned housewide tenet council meeting and reporting information back to other PoC-IC members. Results Unit dashboard, which includes defined goals and percentages and harm infection rates, are presented at the monthly BMT PoC-IC meeting. Each goal is reviewed and interventions are discussed in collaboration with the team using a unified approach. PoC-IC members contact stakeholders within each goal to define interventions for improvement. Meeting minutes, updated interventions, and status of goals and infection rates are relayed to the BMT team. Members of the PoC-IC connect with bedside team members for assistance and collaboration. BMT POC-IC has defined the following goals: 1. Sepsis Algorithm compliance (antibiotics ordered and infused within the first hour of documented fever); 2. Patient Family Experience (90% compliance with greeting families as they enter/exit the unit, physician and nursing communication to patients and families, and addressing patient's pain); 3. Safety (documentation of chlorhexidine (CHG) bathing, environmental wipe down compliance, and catheter line associated bloodstream infection (CLABSI) rate reduction). Conclusions Since the Shared Governance restructuring, the BMT PoC-IC has raised and maintained Patient and Family Experience scores greater than 90% and continues to meet the goal of 100% Sepsis Algorithm compliance. PoC-IC members continue to collaborate with bedside team members to incorporate housewide interventions to improve CHG bathing, environmental cleanliness, and CLABSI rate reduction which is currently 1.76 BSI per 1,000 catheter line days.

Introduction PML is a rare infection with JC virus affecting mostly oligodendrocytes and the white matter of the central nervous system. It affects patients with profound cellular immunodeficiency such as uncontrolled HIV or those receiving immunosuppression for neoplastic and autoimmune diseases. Prognosis is poor as there is no effective therapy except for immune recovery which is not feasible in all cases. Herein, we describe using Quadrivalent (CMV,EBV, Adenovirus and BK) VSTs in a recipient of an unrelated donor hematopoietic cell transplant (HCT) with PML. Methods A 64-year-old female with history of acute myeloid leukemia who underwent 10/10 HLA matched unrelated donor peripheral blood HCT complicated by acute mild skin graft vs host disease. She was off all immunosuppression by 7 months post transplant. At 15 months post HCT, she presented with mild confusion, left hemianopia and difficulty performing some routine tasks. Brain MRI showed demyelination involving the right parietal lobe, corpus callosum and bilateral dorsal periventricular areas. Cerebrospinal fluid (CSF) with JC virus DNA load of 389,773 copies/ml. Serum JC virus level was 1112 copies/ml and CD 4 218 (8.7%). Patient was referred to Cincinnati Children's Hospital for third-party VST infusion . A 3/10 HLA matched unit from their existing VST bank was infused 3 days after her PML diagnosis. She received a total of 6 VST infusions, each 28 days apart. Results Patient was monitored with monthly CSF JC virus and weekly serum JC virus levels. JC virus was cleared from serum and CSF after the fourth and fifth VST infusions, respectively (figure 1). T cell expansion analysis against BK was done by ELISpot (figure 2). Patient received a total of 6 VST infusions. Neuro symptoms stabilized after the second infusion. At 7.5 months from diagnosis (3 months since last VST infusion), she remained neurologically stable with no new deficits, GVHD or other toxicities. Conclusions VSTs with BK activity is a promising therapy for PML patients in whom immune reconstitution is unlikely to occur in a short time frame. More studies are warranted to evaluate the efficacy and long term outcomes of this method. Physicians should be aware of this novel therapy in selected PML cases given poor disease outcomes and lack of effective alternative therapies.

Introduction A reduced toxicity busulfan, fludarabine regimen with alemtuzumab or anti-thymocyte globulin (Gungor et al.) was efficacious in patients undergoing allogeneic HCT for CGD. We report our experience with a similar approach for patients with non-CGD primary immune deficiencies needing a reduced toxicity myeloablative approach. Methods We retrospectively reviewed records of consecutive patients who underwent allogeneic HCT for primary immune deficiencies with a preparative regimen containing busulfan, fludarabine and alemtuzumab or anti-thymocyte globulin(ATG) at two transplant centers between 2015-2018. Busulfan was given twice daily over 4 days with target AUC of 1800 to 2000 μMol/min (based on q12 hr. dosing) or once daily over 4 days with a target AUC of 3600-4400 μMol/min (based on q24 hr. dosing). Fludarabine 180 mg/m2 or 160 mg/m2 was given divided over 6 days or 4 days, respectively. Serotherapy included alemtuzumab 0.3 - 0.5 mg/kg or ATG 7.5 mg/kg given divided over 3 days. GVHD prophylaxis consisted of cyclosporine and mycophenolate mofetil. Results Thirty-five patients (WAS=11, HLH=10, CD40L deficiency=6, IPEX/VEOIBD=4, IFNGR1 def./ SCN/CID/LAD=1) received busulfan, fludarabine and alemtuzumab or ATG for allogeneic HCT (first HCT in 26 patients and second HCT in 9 of 10 patients with HLH). Median age was 2.0 years (range, 0.3 years – 19.8 years). Patients received a graft from an HLA-matched related (n=10), unrelated (n=23), or single allele mismatched related or unrelated donor (n=2). All except one patient engrafted at a median of 13 days (range,11-34 days). One patient developed veno-occlusive disease and two patients developed diffuse alveolar hemorrhage. Seven patients (20%) developed grade 2-3 acute GVHD and 2 patients (5.7%) developed chronic GVHD. One patient developed primary graft failure and two patients secondary graft failure. Eighteen patients (51%) maintained >95% donor chimerism following allogeneic HCT. Sixteen patients (46%) developed mixed chimerism, predominantly in the T-cell lineage, but T-cell donor chimerism progressively increased post-HCT. At 1-year post-transplant, 13 of 16 patients (81%) with mixed chimerism had donor myeloid chimerism >90% and T-cell chimerism >75%. Two patients underwent a second transplant for graft failure. Overall survival was 86%(30 of 35) and event free survival was 77%(27 of 35) at 1 year. Conclusion Our experience suggests that a reduced toxicity busulfan, fludarabine regimen with alemtuzumab or ATG as serotherapy offers a promising approach with low toxicity, durable myeloid engraftment, low incidence of grade 2-4 GVHD and excellent overall survival, and can be considered for a variety of primary immune deficiencies where myeloablative HCT is desired.

Introduction Common labs, such as a daily complete blood count (CBC) or a daily basic metabolic panel (BMP), represent possible healthcare waste. The Global Aim of this quality improvement initiative was to reduce lab draws and overall healthcare costs through implementation of routine standardized lab practices for patients undergoing bone marrow transplant (BMT). Our Smart Aim was to decrease the median number of labs per hospitalized BMT patient per week by 10%. Methods Using the Model for Improvement, we identified several opportunities to decrease the frequency of routine labs. This included: 1) daily CBC and BMP were obtained on all patients from the start of the preparative regimen through discharge; 2) daily CBC and BMP were obtained on all patients upon readmission; 3) there was no standardized process to clinically evaluate lab frequency. We addressed these opportunities through Plan-Do-Study-Act (PDSA) testing. Interventions included: 1) implementing a mindful mechanism to determine lab frequency prior to the start of chemotherapy; 2) weekly scheduled assessment and discussion of lab frequency during rounds; 3) implementation of a readmission order set with decreased frequency of lab monitoring. Finally, we used standardized run charts to measure the impact of the interventions. Results From January 2019 to June 2019, the median number of weekly labs for patients admitted to the BMT unit decreased from 54 to 49. These gains have been sustained for an additional four months. Discussion Using standardized processes, we demonstrated a substantial decrease in the number of weekly labs obtained on patients admitted to the BMT unit. We believe these interventions and measurements can be used in all transplant centers and can influence outcomes.

Introduction Subjects who undergo hematopoietic stem cell transplant (HSCT) are at increased risk for thyroid dysfunction. Few studies compare myeloablative (MAC) and reduced intensity (RIC) conditioning regimens. Objectives Describe the prevalence, incidence, and risk factors for thyroid disorder in pediatric and young adult subjects one year after HSCT after implementation of a universal screening program. Methods We performed a retrospective chart review of 167 subjects who were transplanted from June 2016 to August 2018 at CCHMC and underwent prospective universal late effects screening. One hundred forty-one subjects surviving to 1 year after HSCT were included. Results One hundred nine subjects had documented TSH values at least 9 months after HSCT. Median followup for screened subjects was 669 days (range, 271-1166). Subjects with documented TSH were similar to the overall cohort. Eight subjects had thyroid disorders prior to transplant, and ten developed thyroid disorders after transplant. Of these ten, none had chronic graft-versus-host disease (cGvHD), one had acute GvHD, and one had received TBI (Table 1). The median time to detection of a thyroid disorder was 430 days (range, 231-790) after transplant. One subject developed Hashimoto thyroiditis, one developed Graves disease, seven developed primary hypothyroidism without evidence of autoimmunity, and one developed pazopanib-associated hypothyroidism. This subject developed fatigue, prompting thyroid evaluation; however, the remaining nine patients were clinically euthyroid at diagnosis. Of the 31 subjects at risk who received RIC, 1 (3.2%) developed a new thyroid disorder, compared to 9 of 69 (13.0%) subjects who received MAC (p=0.167). Overall, 10.9% of subjects at risk for thyroid dysfunction after HSCT developed new disease. Conclusion Thyroid dysfunction remains a significant risk after HSCT, particularly after myeloablative conditioning. Annual screening beginning at one year from HSCT is recommended to improve early detection rates, especially since the majority of subjects detected in our analysis had no symptoms of new thyroid disease.

Introduction Recipients of solid organ transplant (SOT) are at risk of viral infection and development of viral-driven malignancy (EBV-PTLD) due to immunosuppressive medications to prevent organ rejection. Treatments are limited by poor efficacy and organ toxicity, and reduction in immunosuppression to enable the patient's immune system fight the infection risks organ rejection. Allogeneic viral specific T-cells (VST) have been used to treat viral infections after stem cell transplant, and here we evaluated VST for the treatment of CMV, ADV, EBV-PTLD and BK in six SOT (heart, liver, kidney, lung) recipients. Methods Clinical descriptors of diagnosis, therapy and viral load in patients are presented. Results At the time of VST infusion, patients were a median of 16 years of age (range 2 - 69 years) with an average of 5 years post-SOT. Patients were on one or more immunosuppressive medications, including on Tacrolimus (3), prednisolone (4) and hydrocortisone (2). The majority of patients have received multiple monthly infusions to treat viral disease (range of 1-8). The HLA match between the VST unit and recipient ranged from 4/10 to 6/10. Class I matches were from 0/6 to 3/6, and Class II matches from 1/4 to 4/4. The treatment was safe with no serious adverse events observed. All patients had stable viral disease or a clinical response following VST infusion. The response was sustained over multiple infusions except one patient who showed a response to CMV after the first infusion but not after the second. This patient had a 5/10 match (3 class I and 2 class II match), liver transplant, and Tacrolimus treatment. Other patients with the same degree of match, virus infection, or immunosuppressant had continued responses and were not likely the cause of the loss of response and therefore could be immune mediated rejection of the VST. The presence of cells responding to viral peptides was evaluated in PBMC from five patients using IFNg ELIspot. Compared to pre-infusion, there was a higher number of responding cells circulating at up to 4 weeks post-VST infusion for CMV and ADV with 129 to 852 spots 1 × 105 peripheral blood mononuclear cells in response to viral peptide. Neither of the 2 kidney recipients treated for BK and EBV, or EBV-PTDL had an increase spots over background despite showing a clinical response suggesting that the cells contributing to the clinical response were in the tissues or still active despite being below the level of detection of 10 spots per 1 × 105 peripheral blood mononuclear cells. Conclusion Infusion of allogeneic VST to SOT recipients suffering from viral infections was safe and resulted in clinical responses in recipients and may offer additional treatment options to this group of patients. Further data are needed to correlate clinical response with VST activity and persistence to optimize future infusion schedules and allow for optimal dosing.

Introduction Adenoviral (AdV) infections are common after HSCT and are a major cause of complications. Antiviral medications are frequently ineffective and toxic. At CCHMC, viral specific T cells (VST) from 3rd party donors are generated by pulsing peripheral blood mononuclear cells (PBMCs) with viral peptide pools (pepmix). The choice of VST product for each patient is based on pre-clinical evidence of anti-AdV activity and the degree of HLA match as the viral epitopes and HLA restriction driving this response remain poorly understood. Objective The focus of this study is to characterize the HLA restriction of the AdV response in our VST bank. Methods Epitope prediction for AdV hexon and penton was done with free software (HLA restrictor 1.2 and IEDB) in conjunction with published data. 20 9mer to 15mer peptides were synthesized. VSTs were pulsed with peptides based on the HLA haplotype of the product and activity was evaluated using FACS for intracellular interferon gamma (IFNg). Post-infusion analysis was performed using peptide pulsed PBMC followed by IFNg ELISpot. HLA restriction was confirmed using co-culture of VST with a set of mouse fibroblasts expressing a single HLA allele (SALs) loaded with AdV pepmix. Results We have characterized 93 VST products and identified that 60/93 (65%) products have AdV activity in vitro. 20 patients have received VST for AdV with a 75% response rate in evaluable patients. A response against at least one AdV peptide has been demonstrated in 12/13 assessed products (4 of which have been infused into patients), and a polyclonal response was seen in 6/12 products (Fig 1). PBMC from 4 VST recipients were probed with the same AdV peptides that had stimulated a response in their respective VST products. In 3/4 recipients there was a response to the same peptides post-infusion as observed in the VST product, confirming in vivo activity (Fig 2). To discern HLA restriction, AdV pepmix was loaded onto class II HLA SALs and then co-cultured with 4 VST products expressing those same class II alleles. Anti-ADV activity was identified for specific class II HLA for all products, confirming the antiviral response in each product is restricted differentially for distinct HLA alleles. In retrospective analysis of one case, a patient with poor clinical response was found to have received a product restricted largely through DRB1*03:01, which was not a site of HLA match, rather than at the matched site of DRB1*04:01 (Fig 3). Conclusions Robust methods can be used to characterize the viral epitopes driving anti-AdV activity of VST products and the subsequent HLA restriction of that response. Response is frequently polyclonal and to some degree restricted through HLA class II antigens. While our sample is small, we propose that prospective adoption of these methods, especially the use of SALs as an initial screen, may allow for more precise VST product selection with improved response rates.

Pericardial effusion requiring surgical intervention after stem cell transplantation: a case series

Mixed chimerism and eventual graft loss occurs in a proportion of children with primary immune deficiencies receiving alemtuzumab, fludarabine, and melphalan reduced-intensity conditioning (RIC) regimens before allogeneic hematopoietic stem cell transplantation (HSCT). We investigated the usefulness of a CD34+ selected stem cell "boost" without conditioning to treat mixed chimerism in children and young adults who received predominantly an alemtuzumab, fludarabine, and melphalan RIC regimen for primary immune deficiencies and reported the outcomes. Patients with a primary immune deficiency disorder who were either enrolled on a prospective CD34+ boost study for treatment of mixed chimerism from 2011 to 2014 (n = 9) or treated with a CD34+ boost on a clinical basis from 2014 to 2016 (n = 3) were included in this analysis. Response to a CD34+ boost was defined as a rise in donor chimerism by ≥15% with donor chimerism of at least 20%, stabilization was defined as a rise in chimerism by