Allogeneic hematopoietic cell transplantation is effective for p47phox chronic granulomatous disease: A Primary Immune Deficiency Treatment Consortium study.

BACKGROUND: P47phox (neutrophil cytosolic factor-1) deficiency is the most common cause of autosomal recessive chronic granulomatous disease (CGD) and is considered to be associated with a milder clinical phenotype. Allogeneic hematopoietic cell transplantation (HCT) for p47phox CGD is not well-described. OBJECTIVES: We sought to study HCT for p47phox CGD in North America. METHODS: Thirty patients with p47phox CGD who received allogeneic HCT at Primary Immune Deficiency Treatment Consortium centers since 1995 were included. RESULTS: Residual oxidative activity was present in 66.7% of patients. In the year before HCT, there were 0.38 CGD-related infections per person-years. Inflammatory diseases, predominantly of the lungs and bowel, occurred in 36.7% of the patients. The median age at HCT was 9.1 years (range 1.5-23.6 years). Most HCTs (90%) were performed after using reduced intensity/toxicity conditioning. HCT sources were HLA-matched (40%) and -mismatched (10%) related donors or HLA-matched (36.7%) and -mismatched (13.3%) unrelated donors. CGD-related infections after HCT decreased significantly to 0.06 per person-years (P = .038). The frequency of inflammatory bowel disease and the use of steroids also decreased. The cumulative incidence of graft failure and second HCT was 17.9%. The 2-year overall and event-free survival were 92.3% and 82.1%, respectively, while at 5 years they were 85.7% and 77.0%, respectively. In the surviving patients evaluated, ≥95% donor myeloid chimerism at 1 and 2 years after HCT was 93.8% and 87.5%, respectively. CONCLUSIONS: Patients with p47phox CGD suffer from a significant disease burden that can be effectively alleviated by HCT. Similar to other forms of CGD, HCT should be considered for patients with p47phox CGD.

Integrome signatures of lentiviral gene therapy for SCID-X1 patients.

Lentiviral vector (LV)-based gene therapy holds promise for a broad range of diseases. Analyzing more than 280,000 vector integration sites (VISs) in 273 samples from 10 patients with X-linked severe combined immunodeficiency (SCID-X1), we discovered shared LV integrome signatures in 9 of 10 patients in relation to the genomics, epigenomics, and 3D structure of the human genome. VISs were enriched in the nuclear subcompartment A1 and integrated into super-enhancers close to nuclear pore complexes. These signatures were validated in T cells transduced with an LV encoding a CD19-specific chimeric antigen receptor. Intriguingly, the one patient whose VISs deviated from the identified integrome signatures had a distinct clinical course. Comparison of LV and gamma retrovirus integromes regarding their 3D genome signatures identified differences that might explain the lower risk of insertional mutagenesis in LV-based gene therapy. Our findings suggest that LV integrome signatures, shaped by common features such as genome organization, may affect the efficacy of LV-based cellular therapies.

Intestinal microbiome and metabolome signatures in patients with chronic granulomatous disease.

BACKGROUND: Chronic granulomatous disease (CGD) is caused by defects in any 1 of the 6 subunits forming the nicotinamide adenine dinucleotide phosphate oxidase complex 2 (NOX2), leading to severely reduced or absent phagocyte-derived reactive oxygen species production. Almost 50% of patients with CGD have inflammatory bowel disease (CGD-IBD). While conventional IBD therapies can treat CGD-IBD, their benefits must be weighed against the risk of infection. Understanding the impact of NOX2 defects on the intestinal microbiota may lead to the identification of novel CGD-IBD treatments. OBJECTIVE: We sought to identify microbiome and metabolome signatures that can distinguish individuals with CGD and CGD-IBD. METHODS: We conducted a cross-sectional observational study of 79 patients with CGD, 8 pathogenic variant carriers, and 19 healthy controls followed at the National Institutes of Health Clinical Center. We profiled the intestinal microbiome (amplicon sequencing) and stool metabolome, and validated our findings in a second cohort of 36 patients with CGD recruited through the Primary Immune Deficiency Treatment Consortium. RESULTS: We identified distinct intestinal microbiome and metabolome profiles in patients with CGD compared to healthy individuals. We observed enrichment for Erysipelatoclostridium spp, Sellimonas spp, and Lachnoclostridium spp in CGD stool samples. Despite differences in bacterial alpha and beta diversity between the 2 cohorts, several taxa correlated significantly between both cohorts. We further demonstrated that patients with CGD-IBD have a distinct microbiome and metabolome profile compared to patients without CGD-IBD. CONCLUSION: Intestinal microbiome and metabolome signatures distinguished patients with CGD and CGD-IBD, and identified potential biomarkers and therapeutic targets.

Measuring the effect of newborn screening on survival after haematopoietic cell transplantation for severe combined immunodeficiency: a 36-year longitudinal study from the Primary Immune Deficiency Treatment Consortium.

BACKGROUND: Severe combined immunodeficiency (SCID) is fatal unless durable adaptive immunity is established, most commonly through allogeneic haematopoietic cell transplantation (HCT). The Primary Immune Deficiency Treatment Consortium (PIDTC) explored factors affecting the survival of individuals with SCID over almost four decades, focusing on the effects of population-based newborn screening for SCID that was initiated in 2008 and expanded during 2010-18. METHODS: We analysed transplantation-related data from children with SCID treated at 34 PIDTC sites in the USA and Canada, using the calendar time intervals 1982-89, 1990-99, 2000-09, and 2010-18. Categorical variables were compared by χ2 test and continuous outcomes by the Kruskal-Wallis test. Overall survival was estimated by the Kaplan-Meier method. A multivariable analysis using Cox proportional hazards regression models examined risk factors for HCT outcomes, including the variables of time interval of HCT, infection status and age at HCT, trigger for diagnosis, SCID type and genotype, race and ethnicity of the patient, non-HLA-matched sibling donor type, graft type, GVHD prophylaxis, and conditioning intensity. FINDINGS: For 902 children with confirmed SCID, 5-year overall survival remained unchanged at 72%-73% for 28 years until 2010-18, when it increased to 87% (95% CI 82·1-90·6; n=268; p=0·0005). For children identified as having SCID by newborn screening since 2010, 5-year overall survival was 92·5% (95% CI 85·8-96·1), better than that of children identified by clinical illness or family history in the same interval (79·9% [69·5-87·0] and 85·4% [71·8-92·8], respectively [p=0·043]). Multivariable analysis demonstrated that the factors of active infection (hazard ratio [HR] 2·41, 95% CI 1·56-3·72; p<0·0001), age 3·5 months or older at HCT (2·12, 1·38-3·24; p=0·001), Black or African-American race (2·33, 1·56-3·46; p<0·0001), and certain SCID genotypes to be associated with lower overall survival during all time intervals. Moreover, after adjusting for several factors in this multivariable analysis, HCT after 2010 no longer conveyed a survival advantage over earlier time intervals studied (HR 0·73, 95% CI 0·43-1·26; p=0·097). This indicated that younger age and freedom from infections at HCT, both directly driven by newborn screening, were the main drivers for recent improvement in overall survival. INTERPRETATION: Population-based newborn screening has facilitated the identification of infants with SCID early in life, in turn leading to prompt HCT while avoiding infections. Public health programmes worldwide can benefit from this definitive demonstration of the value of newborn screening for SCID. FUNDING: National Institute of Allergy and Infectious Diseases, Office of Rare Diseases Research, and National Center for Advancing Translational Sciences.

Successful TCRαß/CD19-Depleted Hematopoietic Cell Transplantation for a Patient With Artemis Deficiency.

Artemis deficiency is characterized by DNA double-strand breaks repairing dysfunction and increased sensitivity to ionizing radiation and alkylating reagents. We describe the first successful case of T-cell receptor [TCR]αß/CD19-depleted hematopoietic cell transplantation [HCT] for Artemis deficiency in Japan. A 6-month-old Korean boy was diagnosed with Artemis-deficient severe combined immunodeficiency. He had no human leukocyte antigen (HLA)-matched sibling or unrelated donor. Therefore, TCRαß/CD19-depleted HCT from his haploidentical mother was performed. Despite mixed chimerism in whole blood, T cells achieved complete donor chimerism 6 months after HCT. TCRαß/CD19-depleted HCT could be an effective treatment for patients with radiation-sensitive severe combined immunodeficiency.

Clinical and Genetic Characterization of Patients with Artemis Deficiency in Japan.

PURPOSE: Artemis is an exonuclease essential for V(D)J recombination and repair of DNA double-stranded breaks. Pathogenic variants in DCLRE1C encoding Artemis cause T-B-NK+ severe combined immunodeficiency (SCID), and patients with Artemis-deficient SCID (ART-SCID) require definitive therapy with allogeneic hematopoietic cell transplantation (HCT). Here we describe the clinical and genetic characteristics of patients with ART-SCID who were diagnosed in Japan from 2003 to 2022. METHODS: Clinical data of ART-SCID patients who were diagnosed between 2003 and 2022 in Japan were collected from their physicians using a questionnaire. RESULTS: ART-SCID diagnosis was made in eight patients from seven families with severe infections within 6 months of life. Two patients had missense variants, five patients had large genomic deletions, and one patient was compound heterozygous for a missense variant and large genomic deletion. All eight underwent allogeneic HCT within 4 months after the diagnosis, 7 receiving a conditioning regimen containing alkylating agents, and one patient without conditioning due to uncontrolled infection. Two patients with poor performance status (PS) died of complications 410 days and 32 days post-HCT, respectively. Of the six surviving patients with a median follow-up time of 8.3 (0.5-17.9) years, three patients had growth retardation. The patients with PS of 0-2 showed a tendency for better overall survival than those with PS 3-4. CONCLUSION: Large deletions were the most common genetic cause of ART-SCID in Japan. To improve HCT outcome, early diagnosis with newborn screening for SCID is urgently needed.

Impact of Genetic Diagnosis on the Outcome of Hematopoietic Stem Cell Transplant in Primary Immunodeficiency Disorders.

To evaluate the relationship between knowledge of genetic diagnosis before HSCT and outcome, we reviewed all HSCTs for primary immune deficiencies (PID) performed at UCSF from 2007 through 2018. SCID, a distinct entity identified since 2010 in California by newborn screening and treated early, was considered separately. The underlying genetic condition was known at the time of HSCT in 85% of cases. Graft failure was less frequent in patients with a genetic diagnosis (19% with a genetic diagnosis versus 47% without, p = 0.020). Furthermore, event-free survival and overall survival (OS) at 5 years were better for those with a genetic diagnosis (78% with versus 44% without, p = 0.006; and 93% versus 60% without, p = 0.0002, respectively). OS at 5 years was superior for known-genotype patients with both SCID (p = 0.010) and non-SCID PID (p = 0.010). There was no difference in OS between HSCT done in 2007-2010 compared to more recently (p = 0.19). These data suggest that outcomes of HSCT for PID with known genotype may reflect specific experience and literature, or that a substantial proportion of patients with PID of undetermined genotype may have had underlying conditions for which HSCT may carry greater risk. The higher rate of graft failure in PID with unknown genotype may be in part explained by insufficient conditioning, which in turn could be dictated by compromised organ function in patients undergoing HSCT late in the course. Widespread availability of PID gene sequencing as standard care can provide genetic diagnoses for most patients with PID prior to HSCT, permitting optimization of transplant approach.

The diagnosis of severe combined immunodeficiency: Implementation of the PIDTC 2022 Definitions.

BACKGROUND: Shearer et al in 2014 articulated well-defined criteria for the diagnosis and classification of severe combined immunodeficiency (SCID) as part of the Primary Immune Deficiency Treatment Consortium's (PIDTC's) prospective and retrospective studies of SCID. OBJECTIVE: Because of the advent of newborn screening for SCID and expanded availability of genetic sequencing, revision of the PIDTC 2014 Criteria was needed. METHODS: We developed and tested updated PIDTC 2022 SCID Definitions by analyzing 379 patients proposed for prospective enrollment into Protocol 6901, focusing on the ability to distinguish patients with various SCID subtypes. RESULTS: According to PIDTC 2022 Definitions, 18 of 353 patients eligible per 2014 Criteria were considered not to have SCID, whereas 11 of 26 patients ineligible per 2014 Criteria were determined to have SCID. Of note, very low numbers of autologous T cells (<0.05 × 109/L) characterized typical SCID under the 2022 Definitions. Pathogenic variant(s) in SCID-associated genes was identified in 93% of patients, with 7 genes (IL2RG, RAG1, ADA, IL7R, DCLRE1C, JAK3, and RAG2) accounting for 89% of typical SCID. Three genotypes (RAG1, ADA, and RMRP) accounted for 57% of cases of leaky/atypical SCID; there were 13 other rare genotypes. Patients with leaky/atypical SCID were more likely to be diagnosed at more than age 1 year than those with typical SCID lacking maternal T cells: 20% versus 1% (P < .001). Although repeat testing proved important, an initial CD3 T-cell count of less than 0.05 × 109/L differentiated cases of typical SCID lacking maternal cells from leaky/atypical SCID: 97% versus 7% (P < .001). CONCLUSIONS: The PIDTC 2022 Definitions describe SCID and its subtypes more precisely than before, facilitating analyses of SCID characteristics and outcomes.

The diagnosis of severe combined immunodeficiency (SCID): The Primary Immune Deficiency Treatment Consortium (PIDTC) 2022 Definitions.

Severe combined immunodeficiency (SCID) results from defects in the differentiation of hematopoietic stem cells into mature T lymphocytes, with additional lymphoid lineages affected in particular genotypes. In 2014, the Primary Immune Deficiency Treatment Consortium published criteria for diagnosing SCID, which are now revised to incorporate contemporary approaches. Patients with typical SCID must have less than 0.05 × 109 autologous T cells/L on repetitive testing, with either pathogenic variant(s) in a SCID-associated gene, very low/undetectable T-cell receptor excision circles or less than 20% of CD4 T cells expressing naive markers, and/or transplacental maternally engrafted T cells. Patients with less profoundly impaired autologous T-cell differentiation are designated as having leaky/atypical SCID, with 2 or more of these: low T-cell numbers, oligoclonal T cells, low T-cell receptor excision circles, and less than 20% of CD4 T cells expressing naive markers. These patients must also have either pathogenic variant(s) in a SCID-associated gene or reduced T-cell proliferation to certain mitogens. Omenn syndrome requires a generalized erythematous rash, absent transplacentally acquired maternal engraftment, and 2 or more of these: eosinophilia, elevated IgE, lymphadenopathy, hepatosplenomegaly. Thymic stromal defects and other causes of secondary T-cell deficiency are excluded from the definition of SCID. Application of these revised Primary Immune Deficiency Treatment Consortium 2022 Definitions permits precise categorization of patients with T-cell defects but does not imply a preferred treatment strategy.

Aberrant T-cell exhaustion in severe combined immunodeficiency survivors with poor T-cell reconstitution after transplantation.

BACKGROUND: Severe combined immunodeficiency (SCID) comprises rare inherited disorders of immunity that require definitive treatment through hematopoietic cell transplantation (HCT) or gene therapy for survival. Despite successes of allogeneic HCT, many SCID patients experience incomplete immune reconstitution, persistent T-cell lymphopenia, and poor long-term outcomes. OBJECTIVE: We hypothesized that CD4+ T-cell lymphopenia could be associated with a state of T-cell exhaustion in previously transplanted SCID patients. METHODS: We analyzed markers of exhaustion in blood samples from 61 SCID patients at a median of 10.4 years after HCT. RESULTS: Compared to post-HCT SCID patients with normal CD4+ T-cell counts, those with poor T-cell reconstitution showed lower frequency of naive CD45RA+/CCR7+ T cells, recent thymic emigrants, and TCR excision circles. They also had a restricted TCR repertoire, increased expression of inhibitory receptors (PD-1, 2B4, CD160, BTLA, CTLA-4), and increased activation markers (HLA-DR, perforin) on their total and naive CD8+ T cells, suggesting T-cell exhaustion and aberrant activation, respectively. The exhaustion score of CD8+ T cells was inversely correlated with CD4+ T-cell count, recent thymic emigrants, TCR excision circles, and TCR diversity. Exhaustion scores were higher among recipients of unconditioned HCT, especially when further in time from HCT. Patients with fewer CD4+ T cells showed a transcriptional signature of exhaustion. CONCLUSIONS: Recipients of unconditioned HCT for SCID may develop late post-HCT T-cell exhaustion as a result of diminished production of T-lineage cells. Elevated expression of inhibitory receptors on their T cells may be a biomarker of poor long-term T-cell reconstitution.

Lentiviral Gene Therapy for Artemis-Deficient SCID.

BACKGROUND: The DNA-repair enzyme Artemis is essential for rearrangement of T- and B-cell receptors. Mutations in DCLRE1C, which encodes Artemis, cause Artemis-deficient severe combined immunodeficiency (ART-SCID), which is poorly responsive to allogeneic hematopoietic-cell transplantation. METHODS: We carried out a phase 1-2 clinical study of the transfusion of autologous CD34+ cells, transfected with a lentiviral vector containing DCLRE1C, in 10 infants with newly diagnosed ART-SCID. We followed them for a median of 31.2 months. RESULTS: Marrow harvest, busulfan conditioning, and lentiviral-transduced CD34+ cell infusion produced the expected grade 3 or 4 adverse events. All the procedures met prespecified criteria for feasibility at 42 days after infusion. Gene-marked T cells were detected at 6 to 16 weeks after infusion in all the patients. Five of 6 patients who were followed for at least 24 months had T-cell immune reconstitution at a median of 12 months. The diversity of T-cell receptor ß chains normalized by 6 to 12 months. Four patients who were followed for at least 24 months had sufficient B-cell numbers, IgM concentration, or IgM isohemagglutinin titers to permit discontinuation of IgG infusions. Three of these 4 patients had normal immunization responses, and the fourth has started immunizations. Vector insertion sites showed no evidence of clonal expansion. One patient who presented with cytomegalovirus infection received a second infusion of gene-corrected cells to achieve T-cell immunity sufficient for viral clearance. Autoimmune hemolytic anemia developed in 4 patients 4 to 11 months after infusion; this condition resolved after reconstitution of T-cell immunity. All 10 patients were healthy at the time of this report. CONCLUSIONS: Infusion of lentiviral gene-corrected autologous CD34+ cells, preceded by pharmacologically targeted low-exposure busulfan, in infants with newly diagnosed ART-SCID resulted in genetically corrected and functional T and B cells. (Funded by the California Institute for Regenerative Medicine and the National Institute of Allergy and Infectious Diseases; ClinicalTrials.gov number, NCT03538899.).

Lentivector cryptic splicing mediates increase in CD34+ clones expressing truncated HMGA2 in human X-linked severe combined immunodeficiency.

X-linked Severe Combined Immunodeficiency (SCID-X1) due to IL2RG mutations is potentially fatal in infancy where 'emergency' life-saving stem cell transplant may only achieve incomplete immune reconstitution following transplant. Salvage therapy SCID-X1 patients over 2 years old (NCT01306019) is a non-randomized, open-label, phase I/II clinical trial for administration of lentiviral-transduced autologous hematopoietic stem cells following busulfan (6 mg/kg total) conditioning. The primary and secondary objectives assess efficacy in restoring immunity and safety by vector insertion site analysis (VISA). In this ongoing study (19 patients treated), we report VISA in blood lineages from first eight treated patients with longer follow up found a > 60-fold increase in frequency of forward-orientated VIS within intron 3 of the High Mobility Group AT-hook 2 gene. All eight patients demonstrated emergence of dominant HMGA2 VIS clones in progenitor and myeloid lineages, but without disturbance of hematopoiesis. Our molecular analysis demonstrated a cryptic splice site within the chicken ß-globin hypersensitivity 4 insulator element in the vector generating truncated mRNA transcripts from many transcriptionally active gene containing forward-oriented intronic vector insert. A two base-pair change at the splice site within the lentiviral vector eliminated splicing activity while retaining vector functional capability. This highlights the importance of functional analysis of lentivectors for cryptic splicing for preclinical safety assessment and a redesign of clinical vectors to improve safety.

Outcomes following treatment for ADA-deficient severe combined immunodeficiency: a report from the PIDTC.

Adenosine deaminase (ADA) deficiency causes ∼13% of cases of severe combined immune deficiency (SCID). Treatments include enzyme replacement therapy (ERT), hematopoietic cell transplant (HCT), and gene therapy (GT). We evaluated 131 patients with ADA-SCID diagnosed between 1982 and 2017 who were enrolled in the Primary Immune Deficiency Treatment Consortium SCID studies. Baseline clinical, immunologic, genetic characteristics, and treatment outcomes were analyzed. First definitive cellular therapy (FDCT) included 56 receiving HCT without preceding ERT (HCT); 31 HCT preceded by ERT (ERT-HCT); and 33 GT preceded by ERT (ERT-GT). Five-year event-free survival (EFS, alive, no need for further ERT or cellular therapy) was 49.5% (HCT), 73% (ERT-HCT), and 75.3% (ERT-GT; P < .01). Overall survival (OS) at 5 years after FDCT was 72.5% (HCT), 79.6% (ERT-HCT), and 100% (ERT-GT; P = .01). Five-year OS was superior for patients undergoing HCT at <3.5 months of age (91.6% vs 68% if ≥3.5 months, P = .02). Active infection at the time of HCT (regardless of ERT) decreased 5-year EFS (33.1% vs 68.2%, P < .01) and OS (64.7% vs 82.3%, P = .02). Five-year EFS (90.5%) and OS (100%) were best for matched sibling and matched family donors (MSD/MFD). For patients treated after the year 2000 and without active infection at the time of FDCT, no difference in 5-year EFS or OS was found between HCT using a variety of transplant approaches and ERT-GT. This suggests alternative donor HCT may be considered when MSD/MFD HCT and GT are not available, particularly when newborn screening identifies patients with ADA-SCID soon after birth and before the onset of infections. This trial was registered at www.clinicaltrials.gov as #NCT01186913 and #NCT01346150.

Granulocyte Transfusions in Patients with Chronic Granulomatous Disease Undergoing Hematopoietic Cell Transplantation or Gene Therapy.

Granulocyte transfusions are sometimes used as adjunctive therapy for the treatment of infection in patients with chronic granulomatous disease (CGD). However, granulocyte transfusions can be associated with a high rate of alloimmunization, and their role in CGD patients undergoing hematopoietic cell transplantation (HCT) or gene therapy (GT) is unknown. We identified 27 patients with CGD who received granulocyte transfusions pre- (within 6 months) and/or post-HCT or GT in a retrospective survey. Twelve patients received granulocyte transfusions as a bridge to cellular therapy. Six (50%) of these patients had a complete or partial response. However, six of 10 (60%) patients for whom testing was performed developed anti-HLA antibodies, and three of the patients also had severe immune-mediated cytopenia within the first 100 days post-HCT or GT. Fifteen patients received granulocyte transfusions post-HCT only. HLA antibodies were not checked for any of these 15 patients, but there were no cases of early immune-mediated cytopenia. Out of 25 patients who underwent HCT, there were 5 (20%) cases of primary graft failure. Three of the patients with primary graft failure had received granulocyte transfusions pre-HCT and were subsequently found to have anti-HLA antibodies. In this small cohort of patients with CGD, granulocyte transfusions pre-HCT or GT were associated with high rates of alloimmunization, primary graft failure, and early severe immune-mediated cytopenia post-HCT or GT. Granulocyte transfusions post-HCT do not appear to confer an increased risk of graft failure.

Association Between the Magnitude of Intravenous Busulfan Exposure and Development of Hepatic Veno-Occlusive Disease in Children and Young Adults Undergoing Myeloablative Allogeneic Hematopoietic Cell Transplantation.

Intravenous busulfan is widely used as part of myeloablative conditioning regimens in children and young adults undergoing allogeneic hematopoietic cell transplantation (HCT). Hepatic veno-occlusive disease/sinusoidal obstruction syndrome (VOD/SOS) is a serious clinical problem observed with busulfan-based conditioning HCT. The development of VOD/SOS may be associated with busulfan exposure. Getting more insight into the association between busulfan exposure and the development of VOD/SOS enables further optimization of dosing and treatment strategies. The objective of this study was to assess the association between the magnitude of busulfan exposure and the occurrence of VOD/SOS in children and young adults undergoing myeloablative conditioning with a busulfan-containing regimen before allogeneic HCT. In this observational study we included all patients who underwent allogeneic HCT with intravenous busulfan as part of the conditioning regimen at 15 pediatric transplantation centers between 2000 and 2015. The endpoint was the development of VOD/SOS. The magnitude of busulfan exposure was estimated using nonlinear mixed effect modeling and expressed as the maximal concentration (Cmax; day 1 and day 1 to 4 Cmax), cumulative area under the curve (AUC; day 1, highest 1-day AUC in 4 days, and 4-day cumulative AUC), cumulative time above a concentration of 300 µg/L, and clearance on day 1. A total of 88 out of 697 patients (12.6%) developed VOD/SOS. The number of alkylators in the conditioning regimen was a strong effect modifier; therefore we stratified the regression analysis for the number of alkylators. For patients receiving only busulfan as one alkylator (36.3%, n = 253), cumulative busulfan exposure (>78 mg × h/L) was associated with increased VOD/SOS risk (12.6% versus 4.7%; odds ratio [OR] = 2.95, 95% confidence interval [CI] 1.13 to 7.66). For individuals receiving busulfan with one or two additional alkylators (63.7%, n = 444), cumulative busulfan exposure (≤78 and >78 mg × h/L) did not further increase the risk of VOD/SOS (15.4% versus 15.2%; OR = 1.03, 95% CI 0.61 to 1.75). The effect of the magnitude of busulfan exposure on VOD/SOS risk in children and young adults undergoing HCT is dependent on the number of alkylators. In patients receiving busulfan as the only alkylator, higher cumulative busulfan exposure increased the risk of VOD/SOS, whereas in those receiving multiple alkylators, the magnitude of busulfan exposure did not further increase this risk.

Quantitative brain MRI morphology in severe and attenuated forms of mucopolysaccharidosis type I.

OBJECTIVE: To assess our hypothesis that brain macrostructure is different in individuals with mucopolysaccharidosis type I (MPS I) and healthy controls (HC), we conducted a comprehensive multicenter study using a uniform quantitative magnetic resonance imaging (qMRI) protocol, with analyses that account for the effects of disease phenotype, age, and cognition. METHODS: Brain MRIs in 23 individuals with attenuated (MPS IA) and 38 with severe MPS I (MPS IH), aged 4-25 years, enrolled under the study protocol NCT01870375, were compared to 98 healthy controls. RESULTS: Cortical and subcortical gray matter, white matter, corpus callosum, ventricular and choroid plexus volumes in MPS I significantly differed from HC. Thicker cortex, lower white matter and corpus callosum volumes were already present at the youngest MPS I participants aged 4-5 years. Age-related differences were observed in both MPS I groups, but most markedly in MPS IH, particularly in cortical gray matter metrics. IQ scores were inversely associated with ventricular volume in both MPS I groups and were positively associated with cortical thickness only in MPS IA. CONCLUSIONS: Quantitatively-derived MRI measures distinguished MPS I participants from HC as well as severe from attenuated forms. Age-related neurodevelopmental trajectories in both MPS I forms differed from HC. The extent to which brain structure is altered by disease, potentially spared by treatment, and how it relates to neurocognitive dysfunction needs further exploration.

Poor T-cell receptor ß repertoire diversity early posttransplant for severe combined immunodeficiency predicts failure of immune reconstitution.

BACKGROUND: Development of a diverse T-cell receptor ß (TRB) repertoire is associated with immune recovery following hematopoietic cell transplantation (HCT) for severe combined immunodeficiency (SCID). High-throughput sequencing of the TRB repertoire allows evaluation of clonotype dynamics during immune reconstitution. OBJECTIVES: We investigated whether longitudinal analysis of the TRB repertoire would accurately describe T-cell receptor diversity and illustrate the quality of T-cell reconstitution following HCT or gene therapy for SCID. METHODS: We used high-throughput sequencing to study composition and diversity of the TRB repertoire in 27 infants with SCID at 3, 6, and 12 months and yearly posttreatment(s). Total RNA from peripheral blood was used as template to amplify TRB rearrangements. RESULTS: TRB sequence analysis showed poor diversity at 3 months, followed by significant improvement by 6 months after cellular therapies. Kinetics of development of TRB diversity were similar in patients with a range of underlying gene defects. However, in patients with RAG and DCLRE1C defects, HCT with no conditioning or immune suppression only resulted in lower diversity than did HCT with conditioning. HCT from a matched donor correlated with higher diversity than did HCT from a mismatched donor. Naive CD4+ T-cell count at 6 months post-HCT correlated with higher TRB diversity. A Shannon index of diversity of 5.2 or lower 3 months after HCT predicted a need for a second intervention. CONCLUSIONS: TRB repertoire after hematopoietic cell therapies for SCID provides a quantitative and qualitative measure of diversity of T-cell reconstitution and permits early identification of patients who may require a second intervention.

Expectations and experience: Parent and patient perspectives regarding treatment for Severe Combined Immunodeficiency (SCID).

INTRODUCTION: Infants with SCID are treated with hematopoietic cell transplantation (HCT) or gene therapy (GT). Caregiver perceptions of pre-treatment counseling and understanding of durability of HCT/GT are poorly understood. METHODS: A survey was designed and distributed to families of patients with SCID. Topics in the questionnaire included SCID genotype and treatment, family recollections of pre-treatment counseling and present clinical status. RESULTS: 151 surveys were analyzed. 132 were treated with HCT, 19 with GT. From counseling received, 37% expected HCT/GT would lead to "cure"; 43% expected HCT/GT would last a lifetime. Of 136 living patients, 59% reported overall good health but 65% reported some persistent health challenges. CONCLUSIONS: For some, interpretation of the word "cure" varied, leading to misunderstanding regarding need for continued medical evaluations and additional therapies. Clear communication regarding the importance of lifelong follow-up, no matter the treatment outcome, will help to optimize good health and quality of life.

The Relationship Between Busulfan Exposure and Achievement of Sustained Donor Myeloid Chimerism in Patients with Non-Malignant Disorders.

The overall objective of allogeneic hematopoietic cell transplantation (HCT) in patients with non-malignant conditions involves replacing a dysfunctional or absent cell or gene product for disease correction. It is unclear whether lower busulfan exposure may be sufficient in this population to facilitate durable myeloid engraftment and limit toxicity. Given that neither the ideal level of mixed myeloid chimerism for specific non-malignant diseases nor how to condition a patient to achieve stable mixed myeloid chimerism is fully known, we sought to analyze the relationships among busulfan exposure, myeloid chimerism, and outcomes in patients with non-malignant conditions receiving busulfan as a part of combination pretransplant conditioning at our institution. This was a single-center, retrospective study including pediatric patients with a variety of non-malignant disorders who underwent allogeneic HCT at the University of California San Francisco Benioff Children's Hospital from March 2007 to June 2018. The busulfan cumulative area under the curve (cAUC) was estimated using a validated population pharmacokinetic model and nonlinear mixed effects modeling. Median busulfan cAUC for all patients was 70 mg·h/L (range, 53 to 108). All of the 29 patients with a busulfan cAUC of ≥70 mg·h/L achieved long-term disease correction with full or stable mixed (>20%) myeloid chimerism, compared to 78.5% (22/28) of patients with a cAUC of <70 mg·h/L (P = .01). Overall ksurvival was evaluated up to 3 years and was identical in patients with busulfan cAUC < 70 mg·h/L and patients with busulfan cAUC ≥70 mg·h/L (96% versus 93%; P = .92). Only three patients died, at days 65, 164 and 980 days post-HCT. Severe busulfan-related toxicities and graft-versus-host-disease (GVHD) were rare, with veno-occlusive disease occurring in four patients (7%), acute respiratory distress syndrome in three patients (5%), and GVHD in five patients (9%). These results demonstrate excellent outcomes and extremely low rates of toxicity across our entire cohort. Based on the results of this study, we recommend a busulfan exposure target of 75 mg·h/L (range, 70 to 80) in all non-malignant patients receiving allogeneic HCT to ensure optimal exposure for achievement of high-level stable myeloid chimerism.