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To the Editor: To provide samples for neonatal mass screening, a few drops of blood are routinely collected from the heel of the newborn infant and allowed to dry on a thick filter paper called the Guthrie card.[1][1] Guthrie cards represent a valuable and comprehensive genetic repository because

Introduction: Sickle cell disease (SCD) is a common inherited blood disorder caused by sickle hemoglobin (HbS) which, unlike normal adult hemoglobin (HbA), becomes insoluble and polymerizes under hypoxic conditions. Patients with SCD experience chronic hemolytic anemia, episodic pain crises and abnormal blood flow to critical organs that cumulatively result in significant illness and shortened lifespans for many. The severity of SCD varies significantly between patients, but for individuals the rate of adverse events is strongly correlated with intraerythrocytic concentration of HbS (%HbS). High per test costs and long turnaround times make conventional laboratory methods (e.g. Hb electrophoresis, HPLC, IEF) impractical for quantifying %HbS in real-time (e.g. during transfusion therapy). The objective of this study was to demonstrate that %HbS in blood could be quantified using our recently developed rapid, low-cost paper-based SCD assay [1]. Methods: Blood samples were obtained from SCD and sickle cell trait (SCT) patients at the Texas Children’s Hematology Center (Houston, TX). To perform the SCD assay a 20μL droplet of blood mixed with Hb solubility buffer (1:10 by volume) was dropped on chromatography paper. The resulting blood stain was digitized with a flatbed scanner (Canon USA Inc, Melville, NY) and analyzed using a custom image analysis code (The MathWorks Inc, Natick, MA). Conventional Hb electrophoresis was performed with the semi-automated Sebia Hydrasys 2 Scan system (Sebia Inc, Norcross, GA). Results: The difference in transport of Hb through the paper produced a blood stain with two parts: the area of the initial drop where polymerized HbS is retained (center spot) and the area where soluble Hb is wicked laterally (peripheral ring). The relative color intensity of the center spot and peripheral ring is related to the blood sample %HbS (Fig. 1). The image analysis code automatically isolates and calculates the ratio of the average color intensities of each area (S-index). A series of reconstituted blood samples with artificially adjusted %HbS from 0 to 60% was used to calibrate the assay so that %HbS could be estimated based on blood stain color intensities (Fig. 2a). The values of %HbS estimated for patient samples using our paper-based SCD assay and actual values measured using conventional Hb electrophoresis were highly correlated with R2 = 0.898 (Fig. 2b). The estimated and actual %HbS values also showed strong agreement with the standard deviation of the difference between the two measurements = 5.5 %HbS (Fig. 2c). The majority of the differences between actual and estimated %HbS (96.67%) are within 2 standard deviations of the mean of the differences. The assay could be performed in under 35 minutes and multiple assays could be performed and analyzed in parallel. The cost of consumable materials and reagents for the paper-based SCD assay is less than $0.03. Conclusions: This study demonstrates the feasibility of using our recently developed paper-based assay to quantify %HbS in blood samples in real-time. The ability to rapidly, inexpensively measure %HbS will be particularly useful for monitoring the effectiveness of chronic transfusion or hydroxyurea therapy for long-term control of HbS content in blood of SCD patients. The ability to measure %HbS in real-time could also potentially facilitate more aggressive prophylactic therapy to intervene rapidly and significantly reduce the rate of life-threatening complications in SCD patients, including stroke. Figure 1: Figure 1:. Figure 2: Figure 2:. Acknowledgments: This work was supported in part by a 2012 NIH Director's Transformative Research Award (NHLBI R01HL117329, PI: SSS). References: [1] Yang X, et al. Lab Chip, 2013, 13, 1464-1467. Disclosures Piety: Tulane University: PCT/US2012/064856 Patents & Royalties. Yang:Tulane University: PCT/US2012/064856 Patents & Royalties. Shevkoplyas:Tulane University: PCT/US2012/064856 Patents & Royalties; Halcyon Biomedical Incorporated: Equity Ownership.

Introduction: Global health research is hampered by the lack of inexpensive and reliable assays to annotate clinical study cohorts for geographically localized endemic genetic disorders. The most prevalent modifier in Africa is sickle cell disease (SCD, HbSS). In SCD, sickling of erythrocytes by polymerization of hemoglobin S (HbS) causes vaso-occlusion and hemolysis, leading to significant morbidity/mortality and constituting a major healthcare and economic burden. The inhomogeneity bias introduced into the clinical data of patient cohorts by the changes associated to undiagnosed SCD is a significant challenge. Thus, our aims were to: a) optimize a paper-based screening test for SCD for its application in suboptimal and resource-limited conditions, b) demonstrate the feasibility of retrospective SCD annotation of a large cohort of children enrolled in a global health research study, and c) extract novel evidence on potential differences in clinical presentation between febrile children with and without SCD enrolled in this cohort. Materials & Methods: First, we adapted and simplified a paper-based SCD assay (Piety et al. 2017) for suboptimal sample conditions (frozen EDTA-whole blood) and limited-resource settings. Five microlitres of thawed EDTA-whole blood was solubilized (high phosphate buffer with saponin/sodium hydrosulfite), and blotted on standard blotting paper. Dots formed by capillarity, and their aspect depended on HbS%. A high-resolution scanner and two smartphone brands were compared for image capture. An algorithm for visual calling of the presence an HbS allele was developed, and the freeware ImageJ determined peripheral/central pixel intensities. An HbS dosimetric curve was determined after identification of optimal parameter correlations by scatter plot matrix. Second, blood samples from 1103 children aged 9 to 35 months enrolled in a randomized open prospective non-inferiority pediatric cohort study on algorithm-based management of febrile illnesses in Tanzania (ePOCT Trial, 2014-6, NCT02225769, Swiss/Tanzanian IRB approval, Keitel et al.2017) were assayed with the optimized paper test. In parallel, confirmation by gold-standard alkaline Hb electrophoresis (Helena Biosciences, UK) was performed. Third, clinical data from the newly SCD-annotated ePOCT database was analyzed (STATA software suite) to identify clinical features associated with febrile illnesses in the HbAA/AS/SS groups. Results: All EDTA-blood samples frozen onsite in Tanzania (shipped and then stored for >1 year) could be assayed. The test was rapid (5'), inexpensive (0.05 USD/test) and accessible (widely available reagents, no requirement for costly equipment, open-source freeware). Determination of HbS status (homozygous HbSS/AA or heterozygous HbSA) was effective both visually and by informatic means. Smartphone cameras yielded identical results (R2=0.96 & 0.97) when compared to a high-definition scanner. Local prevalence was at 1.6% and 13.6% for HbSS and HbAS respectively, in line with previously published data. By visual sorting of blood dots, the assay was 100% sensitive and 75.8% specific for the determination of HbSS-SCD and 97.6% sensitive and 87.5% specific for the identification of an HbS allele (in an hetero- or homozygous state). After analysis of the annotated ePOCT multiparametric clinical dataset, we observed that cough as the main complaint was more prevalent in children with HbSS (OR 3.1, 95% CI: 1.1-8.3). HbSS children were more severely malnourished (MUAC/age average z-scores -0.7 vs 0.0, p=0.01) and slightly more anemic (Hb 9.1 vs 9.8 g/dL, p=0.06) when compared to HbAA counterparts. Interestingly, children with HbAS had a better nutrition status than those with HbAA (MUAC/age average z-score 0.14, p Conclusions: We demonstrated that the retrospective annotation of clinical cohorts for SCD with an optimized paper-based assay is feasible, straightforward and inexpensive. Our approach has the potential to eliminate the interpretation bias associated with SCD, and thus facilitate the downstream analysis of valuable datasets in other studies. As a proof of principle, we examined a properly annotated dataset highlighting novel features of febrile illness in children with SCD and HbAS carriers in Africa. Disclosures No relevant conflicts of interest to declare.

Abstract 3479 Poster Board III-416 Introduction ELISA assays have been proposed as a complement to the Bethesda assay for detection and follow-up of factor VIII (FVIII) antibodies in subjects with hemophilia. The Bethesda assay has several drawbacks. Most importantly, the Bethesda assay would not detect non-inhibitory antibodies, even though these could be responsible for low in vivo recovery of FVIII and /or a pharmacokinetic pattern suggestive of rapid clearance of FVIII. ELISA assays for detecting antibodies to FVIII are not routinely performed in most hospital laboratories and as such, specimens need to be transported to specialized laboratories for processing. Transportation of plasma specimens frozen on dry ice, however, is both costly and cumbersome. Room temperature storage of whole blood and serum specimens adsorbed and dried onto filter paper has been shown to be a convenient and reliable alternative to frozen whole blood and serum samples for various analyses. This study was undertaken to assess whether FVIII antibodies from haemophilic plasma would display similar stability when stored adsorbed onto filter paper at room temperature for 1 month or on plasma specimens stored frozen. Stability was assessed by comparing results of ELISA assays. Methods two hundred and thirteen frozen (at -80°C) plasma samples from patients with or without known FVIII inhibitors were tested. Samples came from 97 congenital haemophilic subjects and 5 subjects with acquired haemophilia. The samples were tested with a previously reported ELISA assay (Haemophilia 2009; 15: 374-6) with minor modifications. The coating antigens were two therapeutic preparations of recombinant FVIII: the full length FVIII preparation Helixate® FS, and the B-domain deleted FVIII Xyntha®. Five dilutions of plasma from a subject with congenital severe hemophilia A known to have a high Bethesda titer was put on all plates as positive control. Six normal plasmas were used on all plates as negative controls. Mean and standard deviation of optical densities were calculated for negative controls. Mean was subtracted from optical density of each test plasma. The resulting value was divided by the value of one standard deviation of negative controls to generate the number of standard deviations for test plasmas. All plasmas were assayed in duplicate. The numbers of standard deviations were compared between frozen samples and samples dried on filter papers. Results The correlation between the numbers of standard deviations obtained with frozen specimens and with specimens dried on filter paper was excellent for both therapeutic preparations of recombinant FVIII, going from R= 0.91 to R= 0.99. Conclusion FVIII antibodies tested by ELISA using plasma dried on filter paper for one month at room temperature or plasma stored at -80°C give comparable results. Disclosures: No relevant conflicts of interest to declare.

[Graphic][1] In many parts of the world, diagnosis and monitoring of CML patients is limited by the availability and cost of molecular testing. In countries without molecular diagnostic capabilities, blood samples can be shipped to central labs, but this is both hampered by sample degradation, and the high costs of shipping. This study explores the method of directly spotting peripheral blood onto a paper template (dried blood spots), with subsequent shipping, RNA extraction, and BCR-ABL testing. Methods: Blood Spots and Shipment. We received dried blood spots from Australia and African countries by mail or courier, and blood from CML patients from our institution were also used for these experiments. 200μL of blood (PB) was pipetted onto Whatman 503 Protein Saver Cards (PSC; Sigma-Aldrich), where each card contains four 50μL spots. Cards were allowed to dry for at least 24 hours at room temperature. For mailing, PSCs were sealed into glassine envelopes with a packet of desiccant, and then placed inside a mailing envelope following DOT and IATA regulation for shipping non-regulated, exempt human specimens. RNA Extraction from Cards and %BCR-ABL determination. Blood spots were incubated with proteinase K followed by RNA isolation using RNeasy Mini Kits (Qiagen). Extracted RNA was quantified using a NanoDrop spectrometer (Thermo Scientific). %BCR-ABL was determined using the automated Cepheid GeneXpert platform or manual two-step quantitative RT-PCR on the 7900HT Fast Real-Time PCR System (Applied Biosystems). Results: Bench top time course: To test for effects of long transit times on RNA quality, we performed a time course study of cards at room temperature (RT) with 5 samples. For each sample, multiple cards were spotted with PB. The cards were then allowed to sit at RT for predetermined amounts of time, up to 42 days, before extracting RNA. We measured RNA integrity for one of the specimens (CML # 5) and found rapid degradation with the RIN number going from 8.7 for the fresh blood to 2.8 after 28 days on the card. However the amplification for both BCR-ABL and ABL differed less than one cycle between the fresh blood and the last time point by manual qRT-PCR (BCR-ABL Ct = 23.63 for fresh blood and 24.06 for day 28 PSC; ABL Ct = 26.69 for fresh blood and 27.64 for day 28 PSC). [Figure 1][2] shows the results of the time course experiment for the 5 samples as a plot of ΔCt versus time in days. BCR-ABL qRT-PCR concordance studies: We compared the %BCR-ABL results obtained in fresh specimen at the institution sending the sample with the %BCR-ABL results we obtained from RNA extracted from PSC using the Cepheid GeneXpert. Paired evaluable results were available for 9 samples with a median WBC = 9.8 x 109/L (range: 3.37x109/L – 85.5x109/L). Samples were 8 to 49 days old at the time of extraction. The amount of RNA input into the GeneXpert reaction ranged from 38.75ng to 1μg. The %BCR-ABL detected ranged from 0.37% to 27% (see Table). The mean absolute difference between fresh blood and PSC BCR-ABL% is 2%; the relative mean percent change for BCR-ABL, using fresh blood as the reference is 13.1% (S.D., 31.2), P = 0.24. Conclusions and future directions: Dried blood spots are relatively inexpensive method to transport blood that preserves enough RNA stability to allow highly accurate BCR-ABL detection, when compared to results performed on an identical platform using fresh peripheral blood samples. Further studies are undergoing to accurately determine the sensitivity of this method and the feasibility of using regular mail for inexpensive transport of specimens. | ID | WBC (1000/μL) | Sample Age at Spotting (Days) | Sample Age at RNA extraction (Days) | RNA ng/μl | Volume GeneXPert (μL) | Paper %BCR-ABL (IS) GeneXpert | Fresh Blood % BCR-ABL (IS) GeneXpert | | --- | ------------- | ----------------------------- | ----------------------------------- | --------- | --------------------- | ------------------------------------ | ------------------------------------ | | I1 | na | | 10 | 426 | 3 | 49 | na | | I2 | 24.1 | | 13 | 110 | 9 | 27 | 45 | | I3 | 80 | | 9 | 18 | 15 | 44 | na | | I4 | 7.4 | 2 | 8 | 5 | 10 | 2.4* | 3.1 | | I5 | 5.5 | | 49 | 5 | 24 | 1.9 | 2 | | I6 | 3.6 | 1 | 30 | 7.42 | 25 | 9 | 12 | | I7 | 85.5 | 1 | 30 | 102 | 10 | 24 | 39 | | I8 | 12.2 | 1 | 29 | 12.4 | 15 | 12 | 8.8 | | I9 | na | 1 | 28 | 1.5 | 25 | 0.37* | 0.71 | | I10 | 3.37 | | 27 | 3 | 25 | 7.8 | 5.7 | | I11 | 15.9 | 1 | 27 | 31 | 10 | 23 | 25 | | I12 | 6.6 | 1 | 27 | 14.4 | 15 | na | 2.3 | Table 1 *%BCR-ABL was manually calculated due to late ABL Cts because of low starting material. ![Figure 1][3] Figure 1 Disclosures No relevant conflicts of interest to declare. [1]: /embed/inline-graphic-2.gif [2]: #F1 [3]: pending:yes

Newborn screening for sickle cell disease (SCD) in developing countries is limited by the cost and technical complexity of current screening methodologies and the delayed availability of screening results. We have recently developed a rapid diagnostic test for SCD that can quickly and inexpensively identify blood samples containing hemoglobin S. We hypothesized that our rapid test would be practical for use in a resource-limited setting in Cabinda, Angola, and that screening mothers or neonates for the presence of hemoglobin S in blood samples would be an effective means of identifying neonates at high risk of having sickle cell disease prior to more definitive testing. After informed consent, we collected blood samples heel-stick from neonates and by finger-stick from mothers at the primary obstetric hospital in Cabinda. We then tested these samples by the rapid SCD test and scored them by visual assessment of staining patterns. Neonates were scored as positive (HbS detected) or negative (no HbS detected) and mothers as AA, AS (sickle trait), or SS (sickle cell disease). Neonatal samples were subsequently tested by isoelectric focusing (IEF) electrophoresis to determine exact sickle cell status. In a cohort of 133 mother-neonate pairs, we used rapid testing on maternal samples to categorize neonates as high-risk (mother positive for HbS) or low-risk (mother negative for HbS). The rapid test was highly accurate in identifying neonates who could be excluded from IEF testing, with a negative predictive value of 93% (Figure 1). In a cohort of 95 neonates similarly triaged by rapid testing on neonatal samples, the negative predictive value of the test was 96% (Figure 2). In both cohorts, the one neonate with HbSS disease was successfully triaged into the high-risk group. Maternal screening with the rapid test would have reduced the proportion of neonates requiring confirmatory IEF testing to 19%, while neonatal screening would have reduced this proportion to 26%. These results indicate the potential utility of the rapid diagnostic test as a screening tool prior to more definitive testing. Used in combination with confirmatory IEF, our rapid test could significantly decrease the cost of newborn screening for SCD and increase its clinical utility by permitting more rapid identification of affected infants. Disclosures Piety: Halcyon Biomedical: Patents & Royalties: Mr. Piety is a co-inventor on a utility PCT application, "Paper-based diagnostic test" (PCT/US2012/064856, 11/13/2012), claiming priority benefit of U.S. 61/692,994 (8/24/2012) and U.S. 61/558,009 (11/10/2011). . Shevkoplyas:Halcyon Biomedical: Equity Ownership, Patents & Royalties: Co-inventor on a utility PCT application, "Paper-based diagnostic test" (PCT/US2012/064856, 11/13/2012), claiming priority benefit of U.S. 61/692,994 (8/24/2012) and U.S. 61/558,009 (11/10/2011). Part-owner of Halcyon Biomedical Inc.,.

Abstract 245 Introduction: Sickle cell disease (SCD) is the most common inherited blood disorder caused by a mutation in the beta-globin chain of the hemoglobin (Hb) molecule. The result of this mutation, Hb S, polymerizes when deoxygenated, giving the red blood cells a characteristic, sickled shape. This polymerization causes in vivo vaso-occlusion and disrupts the vascular endothelium causing multi-organ complications in affected individuals. Nearly 70% of all affected births occur in Africa, where conservative estimates of SCD prevalence suggest a 10.68/1000 rate at birth (compared to 0.49/1000 in the U.S.). Although SCD causes significant morbidity and premature mortality, most affected persons born in the U.S. are able to survive into adulthood (primarily due to the implementation of universal newborn screening). In contrast, most affected individuals born in low-income countries die before the age of 5 years due to lack of early intervention. Current technology for diagnosing SCD relies on hemoglobin electrophoresis, isoelectric focusing or high performance liquid chromatography. This type of testing remains prohibitively expensive to low-income countries, where SCD is most prevalent and newborn screening is unavailable. Thus, many affected individuals are not diagnosed before severe complications or death can occur. The urgent need to develop a low-cost diagnostic test for SCD has been recently recognized as a priority by the World Health Organization. In this study, we describe the implementation of a paper-based hemoglobin solubility assay as a simple, low-cost and rapid test for definitive diagnosis of SCD. Materials and Methods: Normal human venous blood (Hb AA) was collected and compared to blood from patients with SCD (Hb SS) and SCT (Hb AS). To perform the test, a 20uL droplet of whole blood mixed with the components of the Hb solubility assay (SickleDex™, Streck) was deposited onto a paper-fluidic device fabricated using a previously published method. Polymerized deoxy-Hb S remained in the center of the blood stain entrapped by the paper substrate, while other forms of Hb remained soluble and were transported laterally to the periphery of the stain by capillary action. The resulting blood stain was digitized with a portable scanner and analyzed automatically. The red color intensity profiles were normalized by the total area under the curve to account for the differences in hematocrit among subjects. The SCD index was defined as the normalized color intensity 5 mm from the center of the blood stain. Data were presented as results of individual experiments and as mean ± SD. The values of the SCD index for samples from each Hb genotype were compared using a paired two-tailed t-test. Results: The entanglement of polymerized deoxy-Hb S by the fibers of the paper substrate resulted in the formation of a dark red spot in the center of the blood stain, while the wicking of the soluble forms of Hb from the center produced a pink ring on the periphery of the stain. The patterns of the blood stains produced on paper by normal (Hb AA), SCT (Hb AS) and SCD (Hb SS) samples were significantly different (Fig. A). The tight clustering of the normalized color intensity profiles for different subjects with the same Hb genotype enabled the use of the SCD index as a quantitative metric for distinguishing between the three types of samples (Fig. B). The difference between the SCD index measured for Hb AA, Hb AS and Hb SS samples was highly significant, with p Conclusions: This proof-of-concept study demonstrated the feasibility of using the paper-based Hb solubility assay as a simple, low-cost, point-of-care diagnostic test for SCD. The ability to diagnose SCD quickly and inexpensively will be particularly useful for universal SCD screening in resource-limited settings, such as Africa. This test will also be very useful in the emergency room setting in high-income countries to enable healthcare professionals to objectively confirm suspected SCD at the bedside. Disclosures: No relevant conflicts of interest to declare.

Two-dimensional paper chromatography was used to partition the acid-soluble phosphates in the erythrocytes of normal newborn infants, infants with erythroblastosis fetalis and adults. The inorganic phosphate concentration was higher in the fresh red cells of normal and erythroblastotic infants and rose more during incubation for four hours than in the cells of adults. The amount of erythrocyte adenosine-5’-triphosphate in the adults exceeded the quantities found in the cells of the two groups of babies. The 2,3-diphosphoglycerate level was greater in the erythrocytes of adults and infants with erythroblastosis than it was in the normal infants and incubation for four hours resulted in a sharper decrease of this compound in cells of the normal and erythroblastotic infants than in the adults.

1. Paper electrophoresis of abnormal hemoglobins is a simple and convenient technic for the study of the hereditary hemoglobinopathies. 2. A semiquantitative paper electrophoretic technic is described, which allows rather accurate quantitation of the various hemoglobin components by inspection alone. 3. For exact results, the more elaborate technics of elution or photoelectric scanning may be employed. The accuracy of these quantitative technics is illustrated by artificial mixture experiments. 4. The clinical applications of the method in the study of sickle cell disease and hemoglobin C abnormalities are discussed. Apart from the more common hemoglobin abnormalities (such as sickle cell trait, sickle cell anemia, C trait, sickle cell-hemoglobin C disease), a patient with 100 per cent hemoglobin C (homozygous hemoglobin C disease) and a Negro patient with sickle cell-thalassemia disease were discovered. Normal adult hemoglobin (hemoglobin A) was found in all other hereditary and acquired anemias studied. Slightly increased amounts of fetal hemoglobin were detected in cases of hereditary nonspherocytic hemolytic disease and aregenerative anemia. 5. This technic may be used for red cell life span determinations by serially following the disappearance of a certain hemoglobin type transfused into a patient with a different hemoglobin variety. Further applications of the technic are suggested. 6. The combination of the technics of paper electrophoresis and alkali denaturation offer an adequate, simple, and practical tool for diagnosis and investigation of hereditary hemoglobinopathies. 7. Identical apparatus and buffer may be used for serum protein electrophoresis.

We performed a phase 1 clinical trial to evaluate outcomes in patients receiving donor-derived CD19-specific chimeric antigen receptor (CAR) T cells for B-cell malignancy that relapsed or persisted after matched related allogeneic hemopoietic stem cell transplant. To overcome the cost and transgene-capacity limitations of traditional viral vectors, CAR T cells were produced using the piggyBac transposon system of genetic modification. Following CAR T-cell infusion, 1 patient developed a gradually enlarging retroperitoneal tumor due to a CAR-expressing CD4(+) T-cell lymphoma. Screening of other patients led to the detection, in an asymptomatic patient, of a second CAR T-cell tumor in thoracic para-aortic lymph nodes. Analysis of the first lymphoma showed a high transgene copy number, but no insertion into typical oncogenes. There were also structural changes such as altered genomic copy number and point mutations unrelated to the insertion sites. Transcriptome analysis showed transgene promoter–driven upregulation of transcription of surrounding regions despite insulator sequences surrounding the transgene. However, marked global changes in transcription predominantly correlated with gene copy number rather than insertion sites. In both patients, the CAR T-cell–derived lymphoma progressed and 1 patient died. We describe the first 2 cases of malignant lymphoma derived from CAR gene–modified T cells. Although CAR T cells have an enviable record of safety to date, our results emphasize the need for caution and regular follow-up of CAR T recipients, especially when novel methods of gene transfer are used to create genetically modified immune therapies. This trial was registered at www.anzctr.org.au as ACTRN12617001579381.

The leukocyte NADPH oxidase 2 (NOX2) plays a key role in pathogen killing and immunoregulation. Genetic defects in NOX2 result in chronic granulomatous disease (CGD), associated with microbial infections and inflammatory disorders, often involving the lung. Alveolar macrophages (AMs) are the predominant immune cell in the airways at steady state, and limiting their activation is important, given the constant exposure to inhaled materials, yet the importance of NOX2 in this process is not well understood. In this study, we showed a previously undescribed role for NOX2 in maintaining lung homeostasis by suppressing AM activation, in CGD mice or mice with selective loss of NOX2 preferentially in macrophages. AMs lacking NOX2 had increased cytokine responses to Toll-like receptor-2 (TLR2) and TLR4 stimulation ex vivo. Moreover, between 4 and 12 week of age, mice with global NOX2 deletion developed an activated CD11bhigh subset of AMs with epigenetic and transcriptional profiles reflecting immune activation compared with WT AMs. The presence of CD11bhigh AMs in CGD mice correlated with an increased number of alveolar neutrophils and proinflammatory cytokines at steady state and increased lung inflammation after insults. Moreover, deletion of NOX2 preferentially in macrophages was sufficient for mice to develop an activated CD11bhigh AM subset and accompanying proinflammatory sequelae. In addition, we showed that the altered resident macrophage transcriptional profile in the absence of NOX2 is tissue specific, as those changes were not seen in resident peritoneal macrophages. Thus, these data demonstrate that the absence of NOX2 in alveolar macrophages leads to their proinflammatory remodeling and dysregulates alveolar homeostasis.

Hematopoietic cell transplantation from HLA-haploidentical related donors is increasingly used to treat hematologic cancers; however, characteristics of the optimal haploidentical donor have not been established. We studied the role of donor HLA mismatching in graft-versus-host disease (GVHD), disease recurrence, and survival after haploidentical donor transplantation with posttransplantation cyclophosphamide (PTCy) for 1434 acute leukemia or myelodysplastic syndrome patients reported to the Center for International Blood and Marrow Transplant Research. The impact of mismatching in the graft-versus-host vector for HLA-A, -B, -C, -DRB1, and -DQB1 alleles, the HLA-B leader, and HLA-DPB1 T-cell epitope (TCE) were studied using multivariable regression methods. Outcome was associated with HLA (mis)matches at individual loci rather than the total number of HLA mismatches. HLA-DRB1 mismatches were associated with lower risk of disease recurrence. HLA-DRB1 mismatching with HLA-DQB1 matching correlated with improved disease-free survival. HLA-B leader matching and HLA-DPB1 TCE-nonpermissive mismatching were each associated with improved overall survival. HLA-C matching lowered chronic GVHD risk, and the level of HLA-C expression correlated with transplant-related mortality. Matching status at the HLA-B leader and HLA-DRB1, -DQB1, and -DPB1 predicted disease-free survival, as did patient and donor cytomegalovirus serostatus, patient age, and comorbidity index. A web-based tool was developed to facilitate selection of the best haploidentical-related donor by calculating disease-free survival based on these characteristics. In conclusion, HLA factors influence the success of haploidentical transplantation with PTCy. HLA-DRB1 and -DPB1 mismatching and HLA-C, -B leader, and -DQB1 matching are favorable. Consideration of HLA factors may help to optimize the selection of haploidentical related donors.

Adult T-cell leukemia/lymphoma (ATL) is an aggressive neoplasm immunophenotypically resembling regulatory T cells, associated with human T-cell leukemia virus type-1. Here, we performed whole-genome sequencing (WGS) of 150 ATL cases to reveal the overarching landscape of genetic alterations in ATL. We discovered frequent (33%) loss-of-function alterations preferentially targeting the CIC long isoform, which were overlooked by previous exome-centric studies of various cancer types. Long but not short isoform–specific inactivation of Cic selectively increased CD4(+)CD25(+)Foxp3(+) T cells in vivo. We also found recurrent (13%) 3′-truncations of REL, which induce transcriptional upregulation and generate gain-of-function proteins. More importantly, REL truncations are also common in diffuse large B-cell lymphoma, especially in germinal center B-cell–like subtype (12%). In the non-coding genome, we identified recurrent mutations in regulatory elements, particularly splice sites, of several driver genes. In addition, we characterized the different mutational processes operative in clustered hypermutation sites within and outside immunoglobulin/T-cell receptor genes and identified the mutational enrichment at the binding sites of host and viral transcription factors, suggesting their activities in ATL. By combining the analyses for coding and noncoding mutations, structural variations, and copy number alterations, we discovered 56 recurrently altered driver genes, including 11 novel ones. Finally, ATL cases were classified into 2 molecular groups with distinct clinical and genetic characteristics based on the driver alteration profile. Our findings not only help to improve diagnostic and therapeutic strategies in ATL, but also provide insights into T-cell biology and have implications for genome-wide cancer driver discovery.

There is increasing recognition that platelets have a functional role in the pathophysiology of sepsis, though this role has not been precisely defined. Whether sepsis alters the human platelet transcriptome and translational landscape has never been established. We used parallel techniques of RNA sequencing and ribosome footprint profiling to interrogate the platelet transcriptome and translatome in septic patients and healthy donors. We identified 1806 significantly differentially expressed (false discovery rate

We studied a subset of hematopoietic stem cells (HSCs) that are defined by elevated expression of CD41 (CD41hi) and showed bias for differentiation toward megakaryocytes (Mks). Mouse models of myeloproliferative neoplasms (MPNs) expressing JAK2-V617F (VF) displayed increased frequencies and percentages of the CD41hi vs CD41lo HSCs compared with wild-type controls. An increase in CD41hi HSCs that correlated with JAK2-V617F mutant allele burden was also found in bone marrow from patients with MPN. CD41hi HSCs produced a higher number of Mk-colonies of HSCs in single-cell cultures in vitro, but showed reduced long-term reconstitution potential compared with CD41lo HSCs in competitive transplantations in vivo. RNA expression profiling showed an upregulated cell cycle, Myc, and oxidative phosphorylation gene signatures in CD41hi HSCs, whereas CD41lo HSCs showed higher gene expression of interferon and the JAK/STAT and TNFα/NFκB signaling pathways. Higher cell cycle activity and elevated levels of reactive oxygen species were confirmed in CD41hi HSCs by flow cytometry. Expression of Epcr, a marker for quiescent HSCs inversely correlated with expression of CD41 in mice, but did not show such reciprocal expression pattern in patients with MPN. Treatment with interferon-α further increased the frequency and percentage of CD41hi HSCs and reduced the number of JAK2-V617F+ HSCs in mice and patients with MPN. The shift toward the CD41hi subset of HSCs by interferon-α provides a possible mechanism of how interferon-α preferentially targets the JAK2 mutant clone. © 2021 American Society of Hematology ISSN:0006-4971 ISSN:1528-0020

The anti–von Willebrand factor nanobody caplacizumab was licensed for adults with immune-mediated thrombotic thrombocytopenic purpura (iTTP) based on prospective controlled trials. However, few data are available on postmarketing surveillance. We treated 90 iTTP patients with a compassionate frontline triplet regimen associating therapeutic plasma exchange (TPE), immunosuppression with corticosteroids and rituximab, and caplacizumab. Outcomes were compared with 180 historical patients treated with the standard frontline treatment (TPE and corticosteroids, with rituximab as salvage therapy). The primary outcome was a composite of refractoriness and death within 30 days since diagnosis. Key secondary outcomes were exacerbations, time to platelet count recovery, the number of TPE, and the volume of plasma required to achieve durable remission. The percentage of patients in the triplet regimen with the composite primary outcome was 2.2% vs 12.2% in historical patients (P = .01). One elderly patient in the triplet regimen died of pulmonary embolism. Patients from this cohort experienced less exacerbations (3.4% vs 44%, P < .01); they recovered durable platelet count 1.8 times faster than historical patients (95% confidence interval, 1.41-2.36; P < .01), with fewer TPE sessions and lower plasma volumes (P < .01 both). The number of days in hospital was 41% lower in the triplet regimen than in the historical cohort (13 vs 22 days; P < .01). Caplacizumab-related adverse events occurred in 46 patients (51%), including 13 major or clinically relevant nonmajor hemorrhagic events. Associating caplacizumab to TPE and immunosuppression, by addressing the 3 processes of iTTP pathophysiology, prevents unfavorable outcomes and alleviates the burden of care.

© 2020 by The American Society of Hematology, The majority of childhood leukemias are precursor B-cell acute lymphoblastic leukemias (pB-ALLs) caused by a combination of prenatal genetic predispositions and oncogenic events occurring after birth. Although genetic predispositions are frequent in children (>1% to 5%), fewer than 1% of genetically predisposed carriers will develop pB-ALL. Although infectious stimuli are believed to play a major role in leukemogenesis, the critical determinants are not well defined. Here, by using murine models of pB-ALL, we show that microbiome disturbances incurred by antibiotic treatment early in life were sufficient to induce leukemia in genetically predisposed mice, even in the absence of infectious stimuli and independent of T cells. By using V4 and full-length 16S ribosomal RNA sequencing of a series of fecal samples, we found that genetic predisposition to pB-ALL (Pax5 heterozygosity or ETV6-RUNX1 fusion) shaped a distinct gut microbiome. Machine learning accurately (96.8%) predicted genetic predisposition using 40 of 3983 amplicon sequence variants as proxies for bacterial species. Transplantation of either wild-type (WT) or Pax5+/– hematopoietic bone marrow cells into WT recipient mice revealed that the microbiome is shaped and determined in a donor genotype–specific manner. Gas chromatography-mass spectrometry (GC-MS) analyses of sera from WT and Pax5+/– mice demonstrated the presence of a genotype-specific distinct metabolomic profile. Taken together, our data indicate that it is a lack of commensal microbiota rather than the presence of specific bacteria that promotes leukemia in genetically predisposed mice. Future large-scale longitudinal studies are required to determine whether targeted microbiome modification in children predisposed to pB-ALL could become a successful prevention strategy., This study and research in the C.V.-D. group were supported by FEDER, “Miguel Servet” Grant (CP14/00082-AES 2013-2016) from the Instituto de Salud Carlos III (Ministerio de Economía y Competitividad), “Fondo de Investigaciones Sanitarias/Instituto de Salud Carlos III” (PI17/00167). J.H. was supported by ERAPer Med “GEPARD”, the German Cancer AID (Translational Oncology Program 70112951), the ERCStg 85222 “PreventALL”, The German Jose Carreras Foundation (DJCLS 02R/2016 and 07R/2019), and the Kinderkrebsstiftung (2016/17). A.B. was supported by the Katharina-Hardt-Stiftung, the German Children’s Cancer Foundation, and the Federal Ministry of Education and Research, Bonn, Germany. The I.S.-G. group was partially supported by SAF2015-64420-R MINECO/FEDER, UE, RTI2018-093314-B-I00 MCIU/AEI/FEDER, UE, and by Junta de Castilla y León (UIC-017, CSI001U16, and CSI234P18). The I.S.-G. laboratory is a member of the EuroSyStem and the DECIDE Network funded by the European Union under the FP7 program. A.B. and I.S.-G. were supported by the German Carreras Foundation (DJCLS R13/26). A.B., U.F., D.H. (FKZ: 3618S32275 and 3618S32274), I.S.-G., and C.V.-D. (FKZ: 3618S32274) were supported by the German Federal Office for Radiation Protection (BfS). Computational support and infrastructure was provided by the “Centre for Information and Media Technology” (ZIM) at the Heinrich-Heine-University of Düsseldorf. U.F. was supported by the German Carreras Foundation (DJCLS 21R/2019) and by the Research Commission of the Medical Faculty of the Heinrich-Heine-University of Düsseldorf (2016/70). D.H. was supported by the Research Commission of the Medical Faculty of the Heinrich-Heine-University of Düsseldorf (2019/03).

The fate of hematopoietic stem and progenitor cells (HSPC) is tightly regulated by their bone marrow (BM) microenvironment (ME). BM transplantation (BMT) frequently requires irradiation preconditioning to ablate endogenous hematopoietic cells. Whether the stromal ME is damaged and how it recovers after irradiation is unknown. We report that BM mesenchymal stromal cells (MSC) undergo massive damage to their mitochondrial function after irradiation. Donor healthy HSPC transfer functional mitochondria to the stromal ME, thus improving mitochondria activity in recipient MSC. Mitochondrial transfer to MSC is cell-contact dependent and mediated by HSPC connexin-43 (Cx43). Hematopoietic Cx43-deficient chimeric mice show reduced mitochondria transfer, which was rescued upon re-expression of Cx43 in HSPC or culture with isolated mitochondria from Cx43 deficient HSPCs. Increased intracellular adenosine triphosphate levels activate the purinergic receptor P2RX7 and lead to reduced activity of adenosine 5′-monophosphate–activated protein kinase (AMPK) in HSPC, dramatically increasing mitochondria transfer to BM MSC. Host stromal ME recovery and donor HSPC engraftment were augmented after mitochondria transfer. Deficiency of Cx43 delayed mesenchymal and osteogenic regeneration while in vivo AMPK inhibition increased stromal recovery. As a consequence, the hematopoietic compartment reconstitution was improved because of the recovery of the supportive stromal ME. Our findings demonstrate that healthy donor HSPC not only reconstitute the hematopoietic system after transplantation, but also support and induce the metabolic recovery of their irradiated, damaged ME via mitochondria transfer. Understanding the mechanisms regulating stromal recovery after myeloablative stress are of high clinical interest to optimize BMT procedures and underscore the importance of accessory, non-HSC to accelerate hematopoietic engraftment.

Reactivation of fetal hemoglobin remains a critical goal in the treatment of patients with sickle cell disease and β-thalassemia. Previously, we discovered that silencing of the fetal γ-globin gene requires the erythroid-specific eIF2α kinase heme-regulated inhibitor (HRI), suggesting that HRI might present a pharmacologic target for raising fetal hemoglobin levels. Here, via a CRISPR-Cas9–guided loss-of-function screen in human erythroblasts, we identify transcription factor ATF4, a known HRI-regulated protein, as a novel γ-globin regulator. ATF4 directly stimulates transcription of BCL11A, a repressor of γ-globin transcription, by binding to its enhancer and fostering enhancer-promoter contacts. Notably, HRI-deficient mice display normal Bcl11a levels, suggesting species-selective regulation, which we explain here by demonstrating that the analogous ATF4 motif at the murine Bcl11a enhancer is largely dispensable. Our studies uncover a linear signaling pathway from HRI to ATF4 to BCL11A to γ-globin and illustrate potential limits of murine models of globin gene regulation.

Adult T-cell leukemia/lymphoma (ATL) is an aggressive hematological malignancy caused by human T-cell leukemia virus type-1 (HTLV-1). ATL is preceded by decades of chronic HTLV-1 infection, and the tumors carry both somatic mutations and proviral DNA integrated into the tumor genome. In order to gain insight into the oncogenic process, we used targeted sequencing to track the evolution of the malignant clone in 6 individuals, 2 to 10 years before the diagnosis of ATL. Clones of premalignant HTLV-1–infected cells bearing known driver mutations were detected in the blood up to 10 years before individuals developed acute and lymphoma subtype ATL. Six months before diagnosis, the total number and variant allele fraction of mutations increased in the blood. Peripheral blood mononuclear cells from premalignant cases (1 year prediagnosis) had significantly higher mutational burden in genes frequently mutated in ATL than did high-risk, age-matched HTLV-1 carriers who remained ATL-free after a median of 10 years of follow-up. These data show that HTLV-1–infected T-cell clones carrying key oncogenic driver mutations can be detected in cases of ATL years before the onset of symptoms. Early detection of such mutations may enable earlier and more effective intervention to prevent the development of ATL.

The 2016 revision of the World Health Organization classification of tumors of hematopoietic and lymphoid tissues is characterized by a closer integration of morphology and molecular genetics. Notwithstanding, the myelodysplastic syndrome (MDS) with isolated del(5q) remains so far the only MDS subtype defined by a genetic abnormality. Approximately half of MDS patients carry somatic mutations in spliceosome genes, with SF3B1 being the most commonly mutated one. SF3B1 mutation identifies a condition characterized by ring sideroblasts (RS), ineffective erythropoiesis, and indolent clinical course. A large body of evidence supports recognition of SF3B1-mutant MDS as a distinct nosologic entity. To further validate this notion, we interrogated the data set of the International Working Group for the Prognosis of MDS (IWG-PM). Based on the findings of our analyses, we propose the following diagnostic criteria for SF3B1-mutant MDS: (1) cytopenia as defined by standard hematologic values, (2) somatic SF3B1 mutation, (3) morphologic dysplasia (with or without RS), and (4) bone marrow blasts

Older patients with acute myeloid leukemia (AML) respond poorly to standard induction therapy. B-cell lymphoma 2 (BCL-2) overexpression is implicated in survival of AML cells and treatment resistance. We report safety and efficacy of venetoclax with decitabine or azacitidine from a large, multicenter, phase 1b dose-escalation and expansion study. Patients (N = 145) were at least 65 years old with treatment-naive AML and were ineligible for intensive chemotherapy. During dose escalation, oral venetoclax was administered at 400, 800, or 1200 mg daily in combination with either decitabine (20 mg/m2, days 1-5, intravenously [IV]) or azacitidine (75 mg/m2, days 1-7, IV or subcutaneously). In the expansion, 400 or 800 mg venetoclax with either hypomethylating agent (HMA) was given. Median age was 74 years, with poor-risk cytogenetics in 49% of patients. Common adverse events (>30%) included nausea, diarrhea, constipation, febrile neutropenia, fatigue, hypokalemia, decreased appetite, and decreased white blood cell count. No tumor lysis syndrome was observed. With a median time on study of 8.9 months, 67% of patients (all doses) achieved complete remission (CR) + CR with incomplete count recovery (CRi), with a CR + CRi rate of 73% in the venetoclax 400 mg + HMA cohort. Patients with poor-risk cytogenetics and those at least 75 years old had CR + CRi rates of 60% and 65%, respectively. The median duration of CR + CRi (all patients) was 11.3 months, and median overall survival (mOS) was 17.5 months; mOS has not been reached for the 400-mg venetoclax cohort. The novel combination of venetoclax with decitabine or azacitidine was effective and well tolerated in elderly patients with AML (This trial was registered at www.clinicaltrials.gov as #NCT02203773).

Bacterial infection not only stimulates innate immune responses but also activates coagulation cascades. Overactivation of the coagulation system in bacterial sepsis leads to disseminated intravascular coagulation (DIC), a life-threatening condition. However, the mechanisms by which bacterial infection activates the coagulation cascade are not fully understood. Here we show that type 1 interferons (IFNs), a widely expressed family of cytokines that orchestrate innate antiviral and antibacterial immunity, mediate bacterial infection-induced DIC by amplifying the release of high-mobility group box 1 (HMGB1) into the bloodstream. Inhibition of the expression of type 1 IFNs and disruption of their receptor IFN-α/βR or downstream effector (eg, HMGB1) uniformly decreased gram-negative bacteria-induced DIC. Mechanistically, extracellular HMGB1 markedly increased the procoagulant activity of tissue factor by promoting the externalization of phosphatidylserine to the outer cell surface, where phosphatidylserine assembles a complex of cofactor-proteases of the coagulation cascades. These findings not only provide novel insights into the link between innate immune responses and coagulation, but they also open a new avenue for developing novel therapeutic strategies to prevent DIC in sepsis.

Leukocyte reduced NADP (NADPH) oxidase plays a key role in host defense and immune regulation. Genetic defects in NADPH oxidase result in chronic granulomatous disease (CGD), characterized by recurrent bacterial and fungal infections and aberrant inflammation. Key drivers of hyperinflammation induced by fungal cell walls in CGD are still incompletely defined. In this study, we found that CGD (CYBB−) neutrophils produced higher amounts of leukotriene B4 (LTB4) in vitro after activation with zymosan or immune complexes, compared with wild-type (WT) neutrophils. This finding correlated with increased calcium influx in CGD neutrophils, which was restrained in WT neutrophils by the electrogenic activity of NADPH oxidase. Increased LTB4 generation by CGD neutrophils was also augmented by paracrine cross talk with the LTB4 receptor BLT1. CGD neutrophils formed more numerous and larger clusters in the presence of zymosan in vitro compared with WT cells, and the effect was also LTB4- and BLT1-dependent. In zymosan-induced lung inflammation, focal neutrophil infiltrates were increased in CGD compared with WT mice and associated with higher LTB4 levels. Inhibiting LTB4 synthesis or antagonizing the BLT1 receptor after zymosan challenge reduced lung neutrophil recruitment in CGD to WT levels. Thus, LTB4 was the major driver of excessive neutrophilic lung inflammation in CGD mice in the early response to fungal cell walls, likely by a dysregulated feed-forward loop involving amplified neutrophil production of LTB4. This study identifies neutrophil LTB4 generation as a target of NADPH oxidase regulation, which could potentially be exploited therapeutically to reduce excessive inflammation in CGD.

The Primary Immune Deficiency Treatment Consortium (PIDTC) performed a retrospective analysis of 662 patients with severe combined immunodeficiency (SCID) who received a hematopoietic cell transplantation (HCT) as first-line treatment between 1982 and 2012 in 33 North American institutions. Overall survival was higher after HCT from matched-sibling donors (MSDs). Among recipients of non-MSD HCT, multivariate analysis showed that the SCID genotype strongly influenced survival and immune reconstitution. Overall survival was similar for patients with RAG, IL2RG, or JAK3 defects and was significantly better compared with patients with ADA or DCLRE1C mutations. Patients with RAG or DCLRE1C mutations had poorer immune reconstitution than other genotypes. Although survival did not correlate with the type of conditioning regimen, recipients of reduced-intensity or myeloablative conditioning had a lower incidence of treatment failure and better T- and B-cell reconstitution, but a higher risk for graft-versus-host disease, compared with those receiving no conditioning or immunosuppression only. Infection-free status and younger age at HCT were associated with improved survival. Typical SCID, leaky SCID, and Omenn syndrome had similar outcomes. Landmark analysis identified CD4(+) and CD4(+)CD45RA(+) cell counts at 6 and 12 months post-HCT as biomarkers predictive of overall survival and long-term T-cell reconstitution. Our data emphasize the need for patient-tailored treatment strategies depending upon the underlying SCID genotype. The prognostic significance of CD4(+) cell counts as early as 6 months after HCT emphasizes the importance of close follow-up of immune reconstitution to identify patients who may need additional intervention to prevent poor long-term outcome.

Decreased hepcidin mobilizes iron, which facilitates erythropoiesis, but excess iron is pathogenic in beta-thalassemia and other iron-loading anaemias. Erythropoietin (EPO) enhances erythroferrone (ERFE) synthesis by erythroblasts, and ERFE suppresses hepatic hepcidin production, through an unknown mechanism. The BMP/SMAD pathway in the liver is critical for control of hepcidin, and we show that EPO suppressed hepcidin and other BMP target genes in vivo in a partially ERFE-dependent manner. Furthermore, recombinant ERFE suppressed the hepatic BMP/SMAD pathway independently of changes in serum and liver iron, and in vitro, ERFE decreased SMAD 1/5/8 phosphorylation and inhibited expression of BMP target genes in hepatoma cells. ERFE specifically abrogated the induction of hepcidin by BMP5, BMP6 and BMP7, but had no or very little effect on hepcidin induction by BMP2, 4, 9 or Activin B. A neutralising anti-ERFE antibody prevented the ability of ERFE to inhibit hepcidin induction by BMP5, 6 and 7. Cell-free Homogeneous Time Resolved Fluorescence assays showed that BMP5, BMP6 and BMP7 competed with anti-ERFE for binding to ERFE. Biacore analysis showed that ERFE binds to BMP6 with a higher affinity compared to its binding to BMP2, BMP4 or Activin B, and does not bind to GDF15. We propose that ERFE suppresses hepcidin by inhibiting hepatic BMP/SMAD signaling via preferentially binding and impairing the function of an evolutionarily closely related BMP sub-group consisting of BMP5, BMP6 and BMP7. These findings indicate that ERFE can act as a natural ligand trap generated by stimulated erythropoiesis in order to regulate availability of iron. Disclosures Arezes: Pfizer: Research Funding. Foy:Pfizer: Employment. McHugh:Pfizer: Research Funding. Sawant:Pfizer: Employment. Benard:Pfizer: Employment. Quinkert:Pfizer: Research Funding. Terraube:Pfizer: Employment. Brinth:Pfizer: Employment. Tam:Pfizer: Employment. LaVallie:Pfizer: Employment. Cunningham:Pfizer: Employment. Lambert:Pfizer: Employment. Draper:Pfizer: Research Funding. Jasuja:Pfizer: Employment. Drakesmith:La Jolla Pharmaceutical Company: Research Funding; Pfizer: Research Funding; Alnylam: Consultancy; Kymab: Membership on an entity's Board of Directors or advisory committees.

Chronic myelomonocytic leukemia (CMML) and juvenile myelomonocytic leukemia (JMML) are myelodysplastic syndrome (MDS)/myeloproliferative neoplasm (MPN) overlap disorders characterized by monocytosis, myelodysplasia, and a characteristic hypersensitivity to granulocyte-macrophage colony-stimulating factor (GM-CSF). Currently, there are no available disease-modifying therapies for CMML, nor are there preclinical models that fully recapitulate the unique features of CMML. Through use of immunocompromised mice with transgenic expression of human GM-CSF, interleukin-3, and stem cell factor in a NOD/SCID-IL2Rγnull background (NSGS mice), we demonstrate remarkable engraftment of CMML and JMML providing the first examples of serially transplantable and genetically accurate models of CMML. Xenotransplantation of CD34+ cells (n = 8 patients) or unfractionated bone marrow (BM) or peripheral blood mononuclear cells (n = 10) resulted in robust engraftment of CMML in BM, spleen, liver, and lung of recipients (n = 82 total mice). Engrafted cells were myeloid-restricted and matched the immunophenotype, morphology, and genetic mutations of the corresponding patient. Similar levels of engraftment were seen upon serial transplantation of human CD34+ cells in secondary NSGS recipients (2/5 patients, 6/11 mice), demonstrating the durability of CMML grafts and functionally validating CD34+ cells as harboring the disease-initiating compartment in vivo. Successful engraftments of JMML primary samples were also achieved in all NSGS recipients (n = 4 patients, n = 12 mice). Engraftment of CMML and JMML resulted in overt phenotypic abnormalities and lethality in recipients, which facilitated evaluation of the JAK2/FLT3 inhibitor pacritinib in vivo. These data reveal that NSGS mice support the development of CMML and JMML disease-initiating and mature leukemic cells in vivo, allowing creation of genetically accurate preclinical models of these disorders.

Hematopoietic stem cells (HSC) self-renew to sustain stem cell pools and differentiate to generate all types of blood cells. HSCs remain in quiescence to sustain their long-term self-renewal potential. It remains unclear whether protein quality control is required for stem cells in quiescence when RNA content, protein synthesis, and metabolic activities are profoundly reduced. Here, we report that protein quality control via endoplasmic reticulum-associated degradation (ERAD) governs the function of quiescent HSCs. The Sel1L/Hrd1 ERAD genes are enriched in the quiescent and inactive HSCs, and conditional knockout of Sel1L in hematopoietic tissues drives HSCs to hyperproliferation, which leads to complete loss of HSC self-renewal and HSC depletion. Mechanistically, ERAD deficiency via Sel1L knockout leads to activation of mammalian target of rapamycin (mTOR) signaling. Furthermore, we identify Ras homolog enriched in brain (Rheb), an activator of mTOR, as a novel protein substrate of Sel1L/Hrd1 ERAD, which accumulates upon Sel1L deletion and HSC activation. Importantly, inhibition of mTOR, or Rheb, rescues HSC defects in Sel1L knockout mice. Protein quality control via ERAD is, therefore, a critical checkpoint that governs HSC quiescence and self-renewal by Rheb-mediated restriction of mTOR activity.

Inversion of chromosome 16 is a consistent finding in patients with acute myeloid leukemia subtype M4 with eosinophilia, which generates a CBFB-MYH11 fusion gene. It is generally considered that CBFβ-SMMHC, the fusion protein encoded by CBFB-MYH11, is a dominant negative repressor of RUNX1. However, recent findings challenge the RUNX1-repression model for CBFβ-SMMHC–mediated leukemogenesis. To definitively address the role of Runx1 in CBFB-MYH11–induced leukemia, we crossed conditional Runx1 knockout mice (Runx1(f/f)) with conditional Cbfb-MYH11 knockin mice (Cbfb(+/56M)). On Mx1-Cre activation in hematopoietic cells induced by poly (I:C) injection, all Mx1-CreCbfb(+/56M) mice developed leukemia in 5 months, whereas no leukemia developed in Runx1(f/f)Mx1-CreCbfb(+/56M) mice, and this effect was cell autonomous. Importantly, the abnormal myeloid progenitors (AMPs), a leukemia-initiating cell population induced by Cbfb-MYH11 in the bone marrow, decreased and disappeared in Runx1(f/f)Mx1-CreCbfb(+/56M) mice. RNA-seq analysis of AMP cells showed that genes associated with proliferation, differentiation blockage, and leukemia initiation were differentially expressed between Mx1-CreCbfb(+/56M) and Runx1(f/f)Mx1-CreCbfb(+/56M) mice. In addition, with the chromatin immunocleavage sequencing assay, we observed a significant enrichment of RUNX1/CBFβ-SMMHC target genes in Runx1(f/f)Mx1-CreCbfb(+/56M) cells, especially among downregulated genes, suggesting that RUNX1 and CBFβ-SMMHC mainly function together as activators of gene expression through direct target gene binding. These data indicate that Runx1 is indispensable for Cbfb-MYH11–induced leukemogenesis by working together with CBFβ-SMMHC to regulate critical genes associated with the generation of a functional AMP population.

Large-scale sequencing studies of hematologic malignancies have revealed notable epistasis among high-frequency mutations. One of the most striking examples of epistasis occurs for mutations in RNA splicing factors. These lesions are among the most common alterations in myeloid neoplasms and generally occur in a mutually exclusive manner, a finding attributed to their synthetic lethal interactions and/or convergent effects. Curiously, however, patients with multiple-concomitant splicing factor mutations have been observed, challenging our understanding of one of the most common examples of epistasis in hematologic malignancies. In this study, we performed bulk and single-cell analyses of patients with myeloid malignancy who were harboring ≥2 splicing factor mutations, to understand the frequency and basis for the coexistence of these mutations. Although mutations in splicing factors were strongly mutually exclusive across 4231 patients (q < .001), 0.85% harbored 2 concomitant bona fide splicing factor mutations, ∼50% of which were present in the same individual cells. However, the distribution of mutations in patients with double mutations deviated from that in those with single mutations, with selection against the most common alleles, SF3B1(K700E) and SRSF2(P95H/L/R), and selection for less common alleles, such as SF3B1 non-K700E mutations, rare amino acid substitutions at SRSF2(P95), and combined U2AF1(S34/Q157) mutations. SF3B1 and SRSF2 alleles enriched in those with double-mutations had reduced effects on RNA splicing and/or binding compared with the most common alleles. Moreover, dual U2AF1 mutations occurred in cis with preservation of the wild-type allele. These data highlight allele-specific differences as critical in regulating the molecular effects of splicing factor mutations as well as their cooccurrences/exclusivities with one another.

E2A, a basic helix-loop-helix transcription factor, plays a crucial role in determining tissue-specific cell fate, including differentiation of B-cell lineages. In 5% of childhood acute lymphoblastic leukemia (ALL), the t(1,19) chromosomal translocation specifically targets the E2A gene and produces an oncogenic E2A-PBX1 fusion protein. Although previous studies have shown the oncogenic functions of E2A-PBX1 in cell and animal models, the E2A-PBX1–enforced cistrome, the E2A-PBX1 interactome, and related mechanisms underlying leukemogenesis remain unclear. Here, by unbiased genomic profiling approaches, we identify the direct target sites of E2A-PBX1 in t(1,19)–positive pre-B ALL cells and show that, compared with normal E2A, E2A-PBX1 preferentially binds to a subset of gene loci cobound by RUNX1 and gene-activating machineries (p300, MED1, and H3K27 acetylation). Using biochemical analyses, we further document a direct interaction of E2A-PBX1, through a region spanning the PBX1 homeodomain, with RUNX1. Our results also show that E2A-PBX1 binding to gene enhancers is dependent on the RUNX1 interaction but not the DNA-binding activity harbored within the PBX1 homeodomain of E2A-PBX1. Transcriptome analyses and cell transformation assays further establish a significant RUNX1 requirement for E2A-PBX1–mediated target gene activation and leukemogenesis. Notably, the RUNX1 locus itself is also directly activated by E2A-PBX1, indicating a multilayered interplay between E2A-PBX1 and RUNX1. Collectively, our study provides the first unbiased profiling of the E2A-PBX1 cistrome in pre-B ALL cells and reveals a previously unappreciated pathway in which E2A-PBX1 acts in concert with RUNX1 to enforce transcriptome alterations for the development of pre-B ALL.

Chimeric antigen receptor (CAR) T-cell therapy has proven effective in relapsed and refractory B-cell malignancies, but resistance and relapses still occur. Better understanding of mechanisms influencing CAR T-cell cytotoxicity and the potential for modulation using small-molecule drugs could improve current immunotherapies. Here, we systematically investigated druggable mechanisms of CAR T-cell cytotoxicity using >500 small-molecule drugs and genome-scale CRISPR-Cas9 loss-of-function screens. We identified several tyrosine kinase inhibitors that inhibit CAR T-cell cytotoxicity by impairing T-cell signaling transcriptional activity. In contrast, the apoptotic modulator drugs SMAC mimetics sensitized B-cell acute lymphoblastic leukemia and diffuse large B-cell lymphoma cells to anti-CD19 CAR T cells. CRISPR screens identified death receptor signaling through FADD and TNFRSF10B (TRAIL-R2) as a key mediator of CAR T-cell cytotoxicity and elucidated the RIPK1-dependent mechanism of sensitization by SMAC mimetics. Death receptor expression varied across genetic subtypes of B-cell malignancies, suggesting a link between mechanisms of CAR T-cell cytotoxicity and cancer genetics. These results implicate death receptor signaling as an important mediator of cancer cell sensitivity to CAR T-cell cytotoxicity, with potential for pharmacological targeting to enhance cancer immunotherapy. The screening data provide a resource of immunomodulatory properties of cancer drugs and genetic mechanisms influencing CAR T-cell cytotoxicity.

Emicizumab, a bispecific humanized monoclonal antibody, bridges activated factor IX (FIX) and FX to restore the function of missing activated FVIII in hemophilia A. Emicizumab prophylaxis in children with hemophilia A and FVIII inhibitors was investigated in a phase 3 trial (HAVEN 2). Participants, previously receiving episodic/prophylactic bypassing agents (BPAs), were treated with subcutaneous emicizumab: 1.5 mg/kg weekly (group A), 3 mg/kg every 2 weeks (group B), or 6 mg/kg every 4 weeks (group C). Pharmacokinetics, safety, and efficacy (including an intraindividual comparison of participants from a noninterventional study) were evaluated. Eighty-five participants aged