Transfused Sickle Cell Disease Patients Research Articles

Myocardial Fibrosis in Sickle Cell Anemia

Introduction Cardiovascular disease is a leading cause of morbidity and mortality in patients with sickle cell disease (SCD) as they age.Contrast-enhanced cardiac MRI has been utilized to evaluate myocardial fibrosis by calculating the extracellular matrix volume fraction (ECV) from pre and post-contrast T1 mapping. Recent research in both animal and human models reveal that SCD patients have elevated ECV suggestive of myocardial fibrosis and is associated with diastolic dysfunction. The effects of current first-line therapies, chronic transfusions (CTT) or hydroxyurea (HU), on myocardial fibrosis are unknown and at present, there is conflicting data regarding their benefits. At our institution, SCD patients are treated early with either hydroxyurea, chronic transfusions, or both. We aimed to determine whether current disease-modifying therapies differentially affect myocardial fibrosis. Methods This was a single-center, retrospective cohort study of chronically transfused SCD patients and SCD patients on HU and/or CTT at Children's Hospital of Los Angeles between 2017 and 2022 aiming to assess clinical biomarkers associated with elevated ECV in sickle cell disease. This study was reviewed and approved by the Children's Hospital Los Angeles Institutional Review Board. All patients underwent cardiac MRI for clinical assessment of myocardial iron, cardiac enlargement, and myocardial fibrosis. Continuous variables are expressed as mean±standard deviation for normally distributed data and median [interquartile range] for non-normally distributed data. Parametric and non-parametric testing were used where appropriate and c-square testing was used for categorical variables. Results A total of 63 SCD patients, mean age 17.3±5.9 years (range 5-36yo), who underwent contrast-enhanced cardiac MRI imaging between 2017 and 2022 were included in this study: 27 CTT; 43 HU; and 7 healthy participants, mean age 15.4±2.4 years. There was no difference in age between treatment groups, nor healthy and SCD participants. There were 6 SCD patients not on any therapy and 13 patients on both. The ECV was elevated in SCD versus healthy (31.3% [27.9, 35] vs 26% [23.7,27.2], P=0.0003). There was no significant difference between the ECV values of patients on CTT, HU, both or no therapy, P=0.56 (Fig.1A). There was no difference in average length of therapy between CTT or HU, mean 10.4±4.9 vs 10.2±5.2 years and no association between length of therapy and ECV. We found positive correlation of E/A ratio with ECV in patients with SCD regardless of therapy (Spearmans rho 0.34, P=0.008), suggesting an association with left ventricular (LV) restrictive physiology. ECV was associated with increased WBC count (rho +0.28, P=0.03), AST (rho +0.3, P=0.02), decreased GFR (P=0.02), and decreased hemoglobin (rho -0.41, P=0.0013) (Fig.1B), while there was a trend toward increased urine microalbumin (rho +0.41, P=0.09). Discussion Fibrosis is likely due to prolonged, continuous exposure to inadequate myocardial oxygen supply and cardiac microvascular disease. Amelioration of myocardial fibrosis likely requires consistent, effective CTT or HU therapy as suggested by the Cincinnati/CHLA study. The HU patients in that study had documented high MCV or HbF over many years before ECV was measured. St Jude's study was prospective but follow-up was only 2 years and not compared to an untreated or poorly treated cohort. The sum of these studies suggests that protection from fibrosis may only be seen with continual protection from anemia/microvascular disease. This hypothesis remains to be proven. While we did not see a differential effect of hydroxyurea vs. chronic transfusion therapy, it is important to put this data into the context of SCD therapies and their indications. CTT is generally reserved for the most severe vascular disease phenotypes, such as stroke. Hydroxyurea is often prescribed but not always adhered to. The ECV range in our cohort was lower than that found in the original Cincinnati cohort, mean 44%±8, but similar to that found in the St. Jude cohort, median 30% [IQR 28,34] (Fig.1A). Lastly, elevated ECV correlates with anemia, a modifiable risk factor; restrictive LV physiology; and decreased estimated GFR, which may hint at similar etiologies. In summary, ECV is a clinically relevant cardiovascular biomarker and current preventative therapies may ameliorate but not abrogate myocardial fibrosis.

Optimizing Use of Automated Isovolemic Hemodilution Red-Cell Exchange in a Patient Cohort with Sickle Cell Disease: A Quality Improvement Intervention

Background: Red-cell exchange (RCE) is a mainstay of treatment for both acute and chronic complications of sickle cell disease (SCD). It is a resource-intensive intervention requiring transfusion of large volumes of antigen-matched red blood cells (RBC). Identifying suitable RBC units can be challenging due to variability in blood group phenotypes between patients with SCD and the donor population. This often results in use of O-negative units, which are a scarce resource. Efforts to reduce the volume of units transfused, while maintaining therapeutic efficacy is an important clinical need. Isovolemic hemodilution (IHD) prior to RCE reduces the required volume of RBCs. The aim of this project is to evaluate the effect of a change to IHD-RCE on RBC utilization in patients with SCD receiving standard RCE. Methods: All adult SCD patients receiving standard RCE at the Ottawa Hospital were identified. To safely attain a meaningful reduction in transfused RBCs, RCE treatment parameters were individualized for each patient (Table 1). Patient hematocrit was not allowed to decrease below 20% during the depletion phase, and IHD-RCE would be performed only if an estimated reduction in RBC volume of at least 200 mL was expected. Pregnant patients were excluded. Change in RCE protocol to IHD-RCE took place in January 2022. Transfusion and clinical data were obtained from databases at the Ottawa Hospital in the six months preceding and succeeding the change in RCE protocols to allow for a pre- and post-intervention comparison. Results: Thirty-four adults receiving regular RCE for SCD were identified. Twenty-two patients met criteria for a protocol change to IHD-RCE. The mean age of the IHD-RCE cohort was 31 years (SD 9.5). Males comprised 72.7% of this cohort, with the most frequent genotype of hemoglobin SS (68.2%). Over the one-year study period, 1963 RBC units were transfused: 1035 RBC units in the pre-intervention period, and 928 units in the post-intervention period, representing a reduction of 107 RBC units. 1958 (99.7%) of the RBC units transfused were transfused in the setting of RCE, with few (5 units; 0.03%) administered as simple RBC transfusions. Table 2 outlines patient outcomes during the study period. The mean number of RBC units transfused per patient in the pre- and post-intervention periods were 47 and 42.4 units, respectively. The mean number of RBC units per RCE session per patient was significantly reduced from 8.7 units in the pre-intervention period to 7.8 units in the IHD-RCE post-intervention period (mean difference: -0.9, 95% CI: -1.2 to -0.5). A total of 236 RCE sessions occurred during the study period. No difference in RCE session frequency was observed with a change to IHD-RCE during the six-month study period, nor time between RCE sessions. Therapeutic efficacy in attaining target hemoglobin S levels was not affected by the change to IHD-RCE. No adverse patient safety signals were observed during the IHD-RCE sessions to date. Conclusions: This study demonstrates that IHD-RCE, compared to standard RCE, substantially reduces RBC utilization. A total of 107 RBC units were conserved in our patient cohort of 22 chronic RCE patients directly from the transition to IHD-RCE from standard RCE. Based on local RBC per unit costs, this corresponds to an annualized saving of $95,444 CAD. With pressure on blood banks to provide appropriately matched units, and risks of alloimmunization and delayed hemolytic transfusion reactions amongst chronically transfused SCD patients, increased uptake of IHD-RCE should be considered for SCD patients on chronic RCE. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Myeloid Specific HO-1-SIRT1-p53 Nexus Protects Against Iron Induced Chronic Liver Injury in Sickle Cell Disease

Sickle cell disease (SCD) is an autosomal-recessive-genetic disorder that affects ~100,000 Americans and millions of people worldwide. People with SCD experience multiple complications, including acute pain episodes, stroke, and organ damage, with a median life expectancy of 42-47 years in the United States. Red blood cell transfusions are an important therapeutic intervention in SCD, however, chronically transfused SCD patients develop severe iron overload in the liver, heart, spleen, and endocrine organs with increased expression of inflammatory markers. In addition, there is evidence of abnormal iron metabolism in SCD with prior studies showing a low urinary hepcidin level in children with SCD and highly variable levels in adults. Thus, hepatic iron homeostasis in SCD both at baseline and upon repeated blood transfusion remains incompletely understood. In this study we evaluated iron homeostasis in Townes sickle cell mice at baseline and upon iron overload by iron dextran administration. We also evaluated the potential contribution of hepatic macrophages in hepatic iron homeostasis. Townes mice exhibited significant iron accumulation in the liver at baseline. We found significant reduction of hepcidin and increase in ferroportin and ferritin levels in the liver of sickle mice at baseline. However, upon hepatic iron overload (which was generated by intraperitoneal injections of iron dextran (1 g/kg) once a week for upto 10 weeks) the hepcidin ferroportin homeostasis was impaired and we found reduction of ferroportin and ferritin and increase in hepcidin in the sickle mouse liver. Immunohistochemically we could see a significant enrichment of iron loaded macrophages in the liver of SCD mice at baseline. Clodronate liposome mediated depletion of hepatic kupffer cells caused significant liver injury, hepatocyte death, systemic and hepatic iron accumulation and mortality in the mouse liver at baseline suggesting a protective role of hepatic kupffer cells in iron homeostasis. Mechanistic analysis further revealed protective mechanism through myeloid specific heme oxygenase 1 (HO-1)-sirtuin -1 (SIRT1)-p53 signaling that can potentially alleviate iron induced chronic liver injury in the SCD mice. At baseline, HO1 generated by kupffer cells stimulated SIRT1 activation in SCD mouse hepatocytes. Furthermore, HO-1 and SIRT1 prevented iron-induced senescence and hepatocyte cell death via regulating P53 signaling. Clodronate liposome-mediated kupffer cell loss drastically lowered HO-1 expression, which in turn reduced SIRT1 in SCD liver and accelerated senescence and cell death. In line with this finding, we also detected elevated levels of SIRT-1 in SCD patients’ blood serum. Work is currently underway to understand how modulation of HO-1-SIRT1-p53 signaling pathway can be used as a therapeutic option to combat iron induced chronic liver injury.

HLA Class II regulation of immune response in sickle cell disease patients: Susceptibility to red blood cell alloimmunization (systematic review and meta-analysis).

Sickle cell disease (SCD) patients are commonly treated with red blood cell (RBC) transfusion. Pretransfusion tests commonly involve limited serological antibody testing. RBC alloimmunization to RBC antigens is a frequently encountered complication seen in chronically transfused patients. Genetic factors such as the human leukocyte antigen (HLA) are known to influence and regulate immune responses. HLAs are highly polymorphic and play an essential role in regulating immune responses, including RBC alloimmunization. The aim of this study was to conduct a systematic review and meta-analysis to evaluate the association between HLA Class II allelic polymorphisms with the possible risk of developing RBC alloantibodies. Four databases were systematically searched for relevant studies between the years 2000 and 2021 following the PRISMA guidelines. Four articles met the eligibility and quality criterion, and three alleles, HLA-DRB1*04, HLA-DRB1*15 and HLA-DQB1*03, that were found to be potentially associated with an increased risk in alloantibody formation were included. The primary outcome measure was alloimmunization by RBC antigen exposure in multiply transfused SCD patients. The total estimate of alloimmunization of the SCD patients was 2.33 (95% CI, 1.58-3.44), demonstrating susceptibility to RBC alloantibody formation. Heterogeneity between the studies was insignificant, suggesting the differences associated with random sampling errors. The results showed that SCD patients carry an increased risk of producing RBC alloantibodies. A strategy to prevent RBC alloimmunization is genotyping for genetically susceptible SCD patients receiving multiple transfusions. Early identification of genetic variants that can potentially increase the risk of RBC alloimmunization could aid in the screening process and selection of phenotypically matched RBC units.

Altered type 1 interferon responses in alloimmunized and nonalloimmunized patients with sickle cell disease.

Patients with sickle cell disease (SCD) have a high prevalence of RBC alloimmunization. However, underlying mechanisms are poorly understood. Given that proinflammatory type 1 interferons (IFNα/β) and interferon stimulated genes (ISGs) promote alloimmunization in mice, we hypothesized that IFNα/β may contribute to the increased frequency of alloimmunization in patients with SCD. To investigate this, expression of ISGs in blood leukocytes and peripheral blood mononuclear cells (PBMCs) of previously transfused SCD patients with or without alloimmunization and race‐matched healthy controls were quantified, and IFNα/β gene scores were calculated. IFNα/β gene scores of SCD leukocytes and plasma cytokines were elevated, compared to controls (gene score, p < 0.01). Upon stimulation with IFNβ, isolated PBMCs from patients with SCD had elevated ISGs and IFNα/β gene scores (p < 0.05), compared to stimulated PBMCs from controls. However, IFNβ‐stimulated and unstimulated ISG expression did not significantly differ between alloimmunized and non‐alloimmunized patients. These findings indicate that patients with SCD express an IFNα/β gene signature, and larger studies are needed to fully determine its role in alloimmunization. Further, illustration of altered IFNα/β responses in SCD has potential implications for IFNα/β‐mediated viral immunity, responses to IFNα/β‐based therapies, and other sequelae of SCD.

Rejuvenated RBCs Increase Oxygen Consumption in a Simulated Exchange Transfusion Model of Sickle Cell Disease Patients

Introduction: Exchange transfusion of red blood cells (RBCs) in patients with Sickle Cell Disease (SCD) may require 6 to 8 units to reduce sickle hemoglobin (Hb-S) to less than 30 percent of total hemoglobin (NIH No. 02-2117). Low oxygen affinity (high p50) in patients with SCD is manifested by impaired blood viscosities and reduced hemoglobin concentration. Well characterized RBC metabolic changes during liquid storage of donor RBC include an increase in the affinity of hemoglobin for oxygen (low p50) by depletion of 2,3-diphosphoglycerate (2,3-DPG). Transfusion of stored RBCs (Standard RBC) suggests inefficient and impaired O2 delivery to tissues compared to fresh circulating RBCs (Hasan 1994, Scott 2016) or after exchange transfusion in SCD (Uchida 1998). Extracorporeal manipulation of p50 through RBC rejuvenation increases the level of 2,3-DPG and increases the p50 of stored RBCs by right-shifting the Oxyhemoglobin Dissociation Curve (ODC) (Dennis 1979). Rejuvenation occurs by incubating RBCs at 37 °C for 60 minutes with a rejuvenation solution (Citra Labs). An exchange transfusion simulation model was developed to evaluate the changes in oxygen release capacity of rejuvenated RBCs and the potential impact on estimated oxygen consumption (VO2) compared to Standard RBCs.Methods: Oxyhemoglobin dissociation curves were generated from (5) RBC units (leukocyte-reduced), CPD/AS-1, on Day 0, after 21 days of storage (Standard RBC), and after rejuvenation on day 21 (REJ RBC) which were used to estimate p50 values of the donor/recipient mixtures after each exchange transfusion and to determine VO2 as previously described (Li 2016, Srinivasan 2017). An elevated p50 of 30.4 mm Hg, typical for SCD patients (Uchida 1998), was used to estimate the baseline VO2 (200 mL O2/min). VO2 was determined after each simulated RBC exchange with Standard or REJ RBCs assuming a constant blood volume of 5L, cardiac output of 5 L/min, total hemoglobin concentration of 10 g/dL. The model assumed an exchange rate of one apheresis unit of circulating RBCs to transfusion of one unit of Standard or REJ RBCs.Results: Donor RBC p50 was 26.9 ± 2.0 mm Hg on Day 0 and declined with storage to 17.6 ± 1.5 mm Hg at 21 days (p < 0.001, t-test). Rejuvenation restored p50 to 34.8 ± 2.7 mm Hg which was significantly higher than Day 0 (p < 0.001, t-test). The model predicted a reduction in Hb-S from 70 % to 22%, a decrease in p50 after the 8 unit exchange transfusion to 21.6 mm Hg with Standard RBC, but an increase in p50 to 33.3 mm Hg with REJ RBC (Figures 1a & 1b). Similarly, VO2 increased in the REJ RBC group but decreased sequentially with Standard RBC upon each additional exchange transfusion (Figure 1c). The model predicted a decrease in VO2 to 118 mL O2/min for the Standard RBC group and an increase to 233 mL O2/min with REJ RBC group after the exchange transfusion.Conclusions: The model predicted a baseline VO2 of 200 mL O2/min; however, in fresh whole blood from healthy volunteers with Hb-A, normal VO2 was estimated at 244 mL O2/min (Srinivasan 2017). This simulation suggested that performing an exchange transfusion with REJ RBCs could achieve 95% of normal oxygen consumption assuming a constant cardiac output even though the hemoglobin was maintained at 10 g/dL. While exchange transfusion has been a successful therapy to reduce the Hb-S percentage in chronically transfused SCD patients, improving tissue oxygen exchange may not yet be optimized as evidenced by post transfusion declines in p50 (Miller 1980, Uchida 1998). The model is limited because it does not account for improved rheological properties and blood viscosity following exchange transfusion, which was previously reported to improve exercise capacity even though p50 declined (Miller 1980). The model also did not account for any influence from irreversibly sickled cells. Transfusion practices to correct anemia and improve tissue oxygenation may be less effective than intended due to the diminished oxygen release capacity of standard stored RBC units. Transfusion strategies should consider whether the use of RBCs with increased p50 may be physiologically advantageous.Figure 1: Predicted ODC (a) before and after the simulated exchange transfusion with Standard or REJ RBCs and predicted Hb-A vs Hb-S ratios (b) and VO2 (c) after each unit of the exchange transfusion with Standard or rejuvenated RBCs. [Display omitted] DisclosuresKausch:Zimmer Biomet: Employment, Research Funding. Gray:Zimmer Biomet: Employment, Research Funding. Landrigan:Zimmer Biomet: Employment, Research Funding.

Alkaline Phosphatase Is Associated with Red Cell Alloimmunization in the Pulmonary Hypertension and Hypoxic Response (PUSH) Sickle Cell Disease Cohort

Background: Blood transfusion is a common therapy for sickle cell disease (SCD). Although, highly effective, a major limitation is development of alloantibodies to minor blood group antigens on donor red cells. Alloimmunization has a prevalence of 2-5% for transfusions in the general population, but it is significantly higher in SCD. Risk factors for alloimmunization have been poorly characterized, although number of lifetime transfusions is an important risk factor. Alloimmunization has been clinically observed in children with a prevalence of about 7%. With development of each antibody, blood donor matching becomes increasingly difficult and expensive with an increased risk for transfusion reactions and diminished availability of compatible red cell units for treatment of SCD. The ability to identify risk factors for developing alloantibodies would be beneficial for clinicians. To identify markers for alloimmunization in SCD, we have analyzed children and adults who developed this complication. Methods: We analyzed The Pulmonary Hypertension and Hypoxic Response in Sickle Cell Disease (PUSH) study, which enrolled n=468 pediatric and n=59 adult SCD subjects. In both children and adults, alloimmunization cases were defined as a history of at least 1 alloantibody. Controls in both cohorts were defined as subjects with no history of alloantibodies and receipt of more than 10 lifetime red cell transfusions. All others within the study who did not meet these criteria were assigned to a third comparison group. To identify differences between cases, controls and all others, we performed univariate analyses (using ANOVA or Kruskal Wallace where appropriate) for clinical parameters and laboratories. Case control comparisons were also performed for selected variables and plasma levels for 11 cytokines. Results were further analyzed using regression modeling. Results: The overall prevalence of alloimmunization was 7.3% among children (34/468 subjects; median age 12, range 3-20 years) compared to 28.8% in adults (17/59 subjects; median age 37, range 18-73 years). When only considering those with &amp;gt;10 lifetime transfusions, the prevalence was considerably higher at 29.3% and 54.8% in children and adults, respectively. At the same time, 8 pediatric (23.5%) and 5 adult (29.4%) alloimmunization cases had received fewer than 10 transfusions. In a 3-way pediatric cohort comparison (cases, controls and all others), risk factors associated with alloimmunization included SS genotype, older age and markers of more severe disease (higher ferritin, WBCs, platelets and total bilirubin). Comparison of cases to controls showed alkaline phosphatase (P=0.05) was significantly lower in cases, whereas AST (P=0.02) was significantly higher even with adjustment for age. Levels of plasma cytokines MCP-1 (P=0.01) and IFNgamma (P=0.08) were lower in cases from a subset of the pediatric cohort. In adults, only 4/59 (6.8%) subjects had never received a lifetime transfusion (all non-SS). In the adult 3-way comparisons, only SS genotype and higher ferritin were associated with alloimmunization. The adult case control analysis showed higher absolute monocyte count (P=0.02), absolute eosinophil count (P=0.04) and absolute basophil count (P=0.008) in association with alloimmunization cases. In addition, alkaline phosphatase was again significantly lower among cases (P=0.02) as seen in the pediatric cohort. There were no significant differences in cytokine levels among adults. Conclusions: When considering only transfused SCD patients, the prevalence of alloimmunization is higher than 30%. As seen in prior studies, higher lifetime red cell transfusions are an important risk factor especially among adults where most patients have received transfusions. Children who develop alloantibodies appear to have laboratory markers of more severe disease, but this is not observed in adults. A novel association observed across both pediatric and adult subjects is a significantly lower serum alkaline phosphatase in those with alloantibodies. The results of this study suggest a need for improved tracking of red cell transfusion therapy in the US for SCD patients due to a high prevalence of alloimmunization. Further study is also needed to elucidate the significance of the alkaline phosphatase association. Disclosures Gordeuk: CSL Behring: Consultancy, Research Funding; Global Blood Therapeutics: Consultancy, Research Funding; Novartis: Consultancy; Ironwood: Research Funding; Imara: Research Funding.

Prevalence and risk factors for red blood cell alloimmunisation among sickle cell patients in Mwanza City, Tanzania.

BackgroundErythrocyte alloimmunisation can lead to complications such as delayed haemolytic transfusion reaction.ObjectiveThis study investigated the prevalence of and risk factors for red blood cell alloimmunisation among multiply transfused sickle cell disease (SCD) patients in Mwanza City, Tanzania.MethodsFrom May 2017 to July 2017, this descriptive, cross-sectional, hospital-based study enrolled 200 participants with SCD who had received at least two units of blood in the previous year. Blood count was performed using a Sysmex haematology analyser. Antibody screening was done by the tube method using a panel of three screening cells with known antigenicity.ResultsOf the 200 patients enrolled, 108 (54%) were female. The median age was 4.5 years (interquartile range [IQR] = 6), the median number of transfusions was 3 (IQR = 1), and the median pre-transfusion haemoglobin level was 6.6 g/dl (IQR = 2.7). Prevalence of alloimmunisation was 8.5% (17/200) with immunoglobulin G, and one patient developed cold immunoglobulin M antibodies. Blood groups reported were Rhesus C and E, Kell, Kidd and Duffy. There was no statistically significant association between the number of transfusions and the risk of alloimmunisation.ConclusionThe rate of alloimmunisation in multiply transfused SCD patients was 8.5% and higher than other studies in East Africa. Thus, there is a need for extensive red blood cell screening and matching to minimize alloimmunisation and risk of delayed haemolytic transfusion reaction, particularly in SCD and chronically transfused patients.

Effects of repleting organic phosphates in banked erythrocytes on plasma metabolites and vasoactive mediators after red cell exchange transfusion in sickle cell disease.

Red blood cell (RBC) exchange (RCE) transfusion therapy is indicated for certain patients with sickle cell disease (SCD). Although beneficial, this therapy is costly and inconvenient to patients, who may require it monthly or more often. Identification of blood and plasma biomarkers that could improve or help individualise RCE therapy is of interest. Here we examined relevant blood and plasma metabolites and biomarkers of vasoactivity and RBC fragility in a pilot study of SCD patients undergoing RCE using either standard RBC units or RBC units treated with a US Food and Drug Administration (FDA)-approved additive solution containing phosphate, inosine, pyruvate, and adenine ("PIPA"). In this prospective, single-blind, cross-over pilot clinical trial, patients were randomised to receive either standard RBC exchange or PIPA-treated RBC exchange transfusion with each RCE session over a 6-month treatment period. Pre- and post-transfusion blood samples were obtained and analysed for RBC O2 affinity, ATP, purine metabolites, RBC microparticles, and cell free haemoglobin. Red blood cell O2 affinity was maintained after PIPA-RCE in contrast to standard RCE, after which P50 fell (net O2 affinity rose). Plasma ATP did not change significantly after RCE using either of the RBC unit types. Exchange transfusion with PIPA-treated RBC units led to modest increases in plasma inosine and hypoxanthine. Plasma cell free haemoglobin fell after either standard or PIPA-treated RBC exchange transfusion (novel findings), and to a similar extent. RBC-derived microparticles in the plasma fell significantly and similarly after both standard and PIPA-treated RCE transfusion. In summary, treatment of RBCs with PIPA prior to RCE elicited favourable or neutral changes in key metabolic and vascular biomarkers. Further study of its efficacy and safety is recommended and could ultimately serve to improve outcomes in chronically transfused SCD patients.

PB2309 INCIDENCE OF ALLOIMMUNIZATION IN SICKLE CELL DISEASE: EXPERIENCE OF A CENTER IN LISBON

Background:Nowadays, red blood cell (RBC) transfusion is an indispensable option for the treatment and prevention of chronic complications of sickle cell disease (SCD). In SCD patients it has been reported at a rate of 18–76% of alloimmunization after transfusion. It has also been suggested, that transfusion is related to the formation of RBC autoantibodies, especially in patients with hemoglobinopathies. Interestingly, some authors correlate higher susceptibility to allo and autoimmunization in patients without the spleen. That could be one of the explanations why SCD patients have a higher incidence of RBC immunization.Aims:To determinate the rate of alloimmunization among the transfused SCD patients residing in Lisbon. The other objectives were to clarify among the same study population the incidence of positive direct antiglobulin (DAT) test and spleen absence and correlate both with alloimmunization.Methods:The subjects for the study were selected from the adult patients (≥18 years of age) of a tertiary hospital in Lisbon, between 01‐01‐2017 and 20‐02‐2018, that were transfused at least one time and monitored for the presence of irregular antibodies. A total of 61 patients met the inclusion criteria. Most of the routine immunohematological tests, i.e. blood group typing, indirect antiglobulin test (IAT) and DAT, were done using a microtube gel technique. Moreover, clinical assessment of the spleen status (absence or presence) were obtained from imagiological data.Results:In our study, we obtained a rate of alloimmunization of 21,3% (N = 13). 40% of the transfused SCD (N = 22) have in DAT positive and 50% of those/these have alloantibodies. We found in our population a significant association between positive DAT with alloimmunization (p &lt; 0.001). In 58 patients we succeed in obtaining their spleen status and among those without a spleen (N = 36) 25% became alloimmunized.Summary/Conclusion:In our study, the risk of alloimmunization was higher in patients who received more than 20 red blood cell units. Our alloimmunization rate is in agreement with the literature as well as the significant association of DAT with alloimmunization. Interestingly, 50% of those patients with DAT positive also have alloantibodies, supporting the idea that those patients develop autoantibodies due to transfusion therapy. This fact advocates some plausibility in screening for autoantibodies at regular intervals prior to each transfusion. There was no significant correlation between the presence or absence of a spleen and alloimmunization (p = 0.7475). In conclusion, this study is one of the few to approach the rate of alloimmunization in SCD patients. Therefore, it is necessary to have further studies in Portugal in order to study and to understand our heterogeneous SCD population.

Comparative study of alloimmunization against red cell antigens in sickle cell disease &amp; thalassaemia major patients on regular red cell transfusion

Background & objectives:Sickle cell disease (SCD) patients require red cell transfusion during different clinical complications of the disease. Such patients are at a high risk for developing alloantibody against red cell antigens. From India, there are limited data available on alloantibody formation in multiply transfused SCD patients. The present study was thus undertaken to fill up this lacunae by looking at the development of red cell alloantibodies in SCD and β-thalassaemia patients on regular transfusion.Methods:All sickle cell disease patients undergoing red cell transfusion between 2008 and 2016, were included. During this period, a large number of β-thalassaemia major patients also underwent regular red cell transfusion. These thalassaemia patients were also included to compare the tendency of antibody formation between SCD and β-thalassaemia major patients. All patients before regular transfusion were regularly assessed for the development of red cell antibody. Red cell antigen, antibody screen crossmatch and antibody identification were done using the standard technique.Results:A total of 138 patients with SCD aged between 4 and 53 yr (mean 17.6 yr) consisting of 83 males and 55 females (male:female, 1.5:1) along with 333 transfusion-dependent β-thalassaemia patients were studied. Over the last eight years, 15 patients with SCD and four patients with thalassaemia developed alloantibody (P<0.001). Antibody specificity of their alloantibodies was against Rhc, RhE, Kell, Fya and Fyb only. Sickle cell disease patients with and without alloantibody required on the average 11.8 and 8.6 units of red cell concentrate, respectively (P<0.05).Interpretation & conclusions:About 11 per cent of the transfused sickle cells patients developed alloantibodies. The antibody specificity was restricted to Rh, Kell and Duffy blood group systems. Extended antigen matching involving Rh, Kell and Duffy antigens may prevent alloantibody in such patients.

FCGR2B B2.4 Haplotype Predicts Increased Risk of Red Blood Cell Alloimmunization in Sickle Cell Disease Patients

Introduction: Red blood cell (RBC) alloimmunization is an important transfusion complication which is very prevalent among patients with sickle cell disease (SCD). Only part of patients is able to develop alloantibodies following antigen-mismatched transfusions, named the ‘immune responders’, who should be prospectively transfused with antigen-matched RBC units, comprising the most immunogenic erythrocyte antigens. Auto-immune diseases are a known risk factor for RBC alloimmunization, suggesting that auto-immunity and post-transfusion alloantibody development happen through similar physiopathological pathways. In this context, polymorphisms in FCGR2B gene have already been associated with several auto-immune disorders and, hypothetically, could be associated with RBC alloimmunization and help to identify the ‘immune responders’ in transfusion practice.Methods: In this case-control study, we enrolled 277 transfused SCD patients with retrospective data on alloimmunization status and transfusion exposure from two Brazilian centers. DNA samples (collected from March, 2017 to June, 2018) were extracted from whole blood samples using commercial kits (PureLink™ Genomic DNA®, Invitrogen, CA), and used for PCR amplification of promoter region of FCGR2B gene containing both -386G/C and -120T/A single nucleotide polymorphisms (SNPs) using gene-specific primer. SNPs of the FCGR2B were genotyped by direct Sanger sequencing (ABI3730XL, Applied Biosystems, CA). Cases had a positive history of alloimmunization with a clinically significant alloantibody and a minimum transfusion exposure of 1 RBC unit. Controls had a negative history of alloimmunization and having received ≥ 2 RBC units. Patients with autoimmune diseases or poor quality of DNA were excluded. Unadjusted and adjusted analyses were conducted by using Logistic Regression models to determine the association of covariates with binary outcome. Since the assumption of linearity in the logit was not supported, continuous covariates were categorized based on optimum cut-off point derived from ROC analysis. All statistical analyses were performed using SAS University Edition. A p-value of <0.05 was considered to be statistically significant.Results: A total of 237 patients met the eligibility criteria, 121 cases (alloimmunized) and 117 controls (non-alloimmunized). Majority of patients were female in cases (61%) and male in controls (86%), with mean age of 27.9 years (SD 15.3). Table 1 list the characteristics between the groups. RBC alloimmunization was associated with female sex (p<0.001), lifetime number of RBC units transfused (p=0.002) and FCGR2B 120T/A SNP (p=0.031). No statistically differences in the allele frequency of c.386C were observed between groups (p=0.602). FCGR2B -386G/C and -120T/A SNPs were in intense linkage disequilibrium. Three haplotypes of promoter region were identified as 2B.1 (-386G-120T), 2B.2 (-386C-120T) and 2B.4 (-386C-120A) with statistical significance (p=0.045). Logistic regression model was performed to assess the effects of age, gender, lifetime number of RBC units transfused and FCGR2B 2B.4 haplotype on the likelihood of RBC alloimmunization in patients with SCD. The analysis identified that female sex (OR 10.03, CI95% 5.16-19.49; p<0.001) and FCGR2B 2B.4 haplotype (OR 4.55, CI95% 1.11-18.65; p=0.035) predict increased risk of RBC alloimmunization in SCD patients as show in Table 2.Conclusions: SCD patients with the FCGR2B 2B.4 haplotype had over a 4-fold higher risk for RBC alloimmunization in comparison with patients without this haplotype and probably may be helpful to identify the ‘immune responders’. The presence of FCGR2B 2B.4 haplotype have been associated with increased expression of this inhibitory Fc gamma receptor in immune system cells, that was strongly associated with capacity of immune tolerance, regulating the development of antibodies. Future studies are needed to understand more about the functional and immune mechanism behind alloimmunization in SCD patients and ultimately improve our current preventive strategies. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Frequency of Red Blood Cell Alloimmunization in Patients with Sickle Cell Disease in Palestine.

Background Transfusion of red blood cells (RBC) is an essential therapeutic tool in sickle cell disease (SCD). Repeated RBC transfusions can cause alloimmunization which causes difficulty in cross-matching and finding compatible blood for transfusions. This study aimed to investigate the frequency of RBC alloimmunization and related risk factors among Palestinian SCD patients. Materials and Methods A multicenter cross-sectional study on 116 previously transfused SCD patients from three centers in West Bank, Palestine. Demographic, medical data and history of transfusion were recorded. Blood samples were collected from transfused consenting SCD patients. Gel card method was used for antibody screening and identification. In all patients, autocontrol and direct antiglobulin (DAT) test were performed using polyspecific (anti-IgG + C3d) anti-human globulin (AHG) gel cards for the detection of autoantibodies. Results Of the SCD patients, 62 (53.4%) patients were HbSS and 54 (46.6%) patients were sickle β-thalassemia (S/β-thal). There were 53 (45.7%) females and 63 (54.3%) males. Mean age was 18.8 years (range 3-53 years). The frequency of RBC alloimmunization among SCD patients was 7.76%, with anti-K showing the highest frequency (33.3%) followed by anti-E (22.2%), anti-D (11.1%), anti-C (11.1%), and anti-c (11.1%). All reported IgG alloantibodies were directed against antigens in the Rh (66.7%) and Kell (33.3%) systems. Older ages of patients, increased number of blood units transfused, and splenectomy were the commonest risk factors for alloimmunization in our study. Conclusions RBC alloimmunization rate among Palestinian SCD patients is low compared to neighboring countries and countries all over the world but still warrants more attention. Phenotyping of donors/recipients' RBC for Rh antigens and K1 (partial phenotype matching) before their first transfusion may reduce the incidence of alloimmunization.

High immunogenicity of red blood cell antigens restricted to the population of African descent in a cohort of sickle cell disease patients.

Sickle cell disease (SCD) patients undergo multiple red blood cell (RBC) transfusions and are regularly exposed to low-prevalence (LP) antigens specific to individuals of African descent. This study evaluated the prevalence of antibodies against LP antigens in SCD patients and the need to identify these antibodies in everyday practice. Plasma from 211 SCD patients was tested with RBCs expressing the following LP antigens: RH10 (V), RH20 (VS), RH23 (DW ), RH30 (Goa ), KEL6 (Jsa ), and MNS6 (He). Nine LP antibodies were found in eight patients (3.8%): five anti-RH23, two anti-RH30, and two anti-MNS6. The exposure risk, calculated for each LP antigen, was below 3% per RBC unit, for all antigens tested. Thus, in this cohort of transfused SCD patients, the prevalence of LP antibodies was similar to that of antibodies against antigens of the FY, JK, and MNS blood group systems. These findings also reveal the occurrence of anti-RH23 in SCD patients. No anti-RH20 or anti-KEL6 were found, despite the high frequency of mismatch situations. These results highlight the immunogenicity of these LP antigens, and the evanescence of antibodies against LP antigens. They also highlight the importance of appropriate pretransfusion testing for patients frequently transfused, who are likely to be exposed to multiple types of blood group antigens.

Nonclassical FCGR2C haplotype is associated with protection from red blood cell alloimmunization in sickle cell disease

AbstractRed blood cell (RBC) transfusions are of vital importance in patients with sickle cell disease (SCD). However, a major complication of transfusion therapy is alloimmunization. The low-affinity Fcγ receptors, expressed on immune cells, are important regulators of antibody responses. Genetic variation in FCGR genes has been associated with various auto- and alloimmune diseases. The aim of this study was to evaluate the association between genetic variation of FCGR and RBC alloimmunization in SCD. In this case-control study, DNA samples from 2 cohorts of transfused SCD patients were combined (France and The Netherlands). Cases had a positive history of alloimmunization, having received ≥1 RBC unit. Controls had a negative history of alloimmunization, having received ≥20 RBC units. Single nucleotide polymorphisms and copy number variation of the FCGR2/3 gene cluster were studied in a FCGR-specific multiplex ligation-dependent probe amplification assay. Frequencies were compared using logistic regression. Two hundred seventy-two patients were included (130 controls, 142 cases). The nonclassical open reading frame in the FCGR2C gene (FCGR2C.nc-ORF) was strongly associated with a decreased alloimmunization risk (odds ratio [OR] 0.26, 95% confidence [CI] 0.11-0.64). This association persisted when only including controls with exposure to ≥100 units (OR 0.30, CI 0.11-0.85) and appeared even stronger when excluding cases with Rh or K antibodies only (OR 0.19, CI 0.06-0.59). In conclusion, SCD patients with the FCGR2C.nc-ORF polymorphism have over a 3-fold lower risk for RBC alloimmunization in comparison with patients without this mutation. This protective effect was strongest for exposure to antigens other than the immunogenic Rh or K antigens.

Separation of autologous red blood cells from specimen of the transfused sickle cell disease patients using hypotonic saline

Background: Red blood cell (RBC) antigen typing in transfused sickle cell disease (SCD) patients is a difficult task due to contamination of the transfused red cells. Aim: This pilot study was aimed to standardize an easy approach to separate the autologous RBCs from the transfused patient for RBC antigen typing in SCD. Materials and Methods: The RBCs from transfused patients with SCD were separated by hypotonic saline and tested with various antisera by standard serological methods. Results: Ten antisera showing negative reaction with donors' RBCs reacted positively with the patients' autologous RBCs separated by treatment with hypotonic saline. Seven antisera reacted with the donors' RBCs were nonreactive with the patients' autologous RBCs after elimination of the donor's RBCs by treatment with hypotonic saline. Conclusion: The hypotonic saline can be used as method to separate the autologous RBCs from the mixture with the transfused RBC in patients with SCD.

Changes in Brain Oxygenation in Response to Inhaled 100% Oxygen Are Different in Sickle Cell Disease Patients

Introduction: The prevalence of silent stroke increases monotonically with age in SCD patients, with more than 50% developing detectable white matter hyperintensities on MRI by adulthood. We are exploring the use of inhaled oxygen as a contrast agent to try to identify individuals at risk for silent stroke and to better understand how the brain regulates its own oxygen delivery. In this study, we report changes of brain Blood Oxygen Level Dependent (BOLD) signal and frontal Near Infrared Spectroscopy (NIRs) to 5 minutes of inhaled 100% oxygen in patients with sickle cell disease (SCD), non sickle anemia (ACTL), and control subjects.Method: The study was approved by the institutional review board and performed at Children’s Hospital Los Angeles (CHLA); all patients provided informed consent. Patients with previous stroke, pregnancy, and acute chest pain and crisis hospitalization within one month were excluded. 19 SCD patients (age = 20.7 ± 8.8), 12 patients with non sickle anemia syndromes (age = 25.1 ± 6.9) and 20 ethnicity matched control (CTL) subjects (age = 30.5 ± 12.7) were studied. Peripheral oxygen saturation (SpO2%) was measured by MRI compatible pulse oximeter. A five minute BOLD sequence was acquired with the patient breathing room air for 50 seconds, followed by 100% oxygen for 250 seconds. NIRS recordings of oxygenated hemoglobin change (DOHB), deoxygenated hemoglobin change (DDHB) and tissue oxygenation index (TOI) were recorded from the patient’s forehead. Average BOLD signal was from a 6 cm slab in the middle of the brain. CBC, hemoglobin electrophoresis, and markers of hemolysis were also measured.Results: A representative frontal DOHB signal, and the parameters used to characterize its time-course, are shown in Figure 1. DOHB remained stable until oxygen was administered and then increased over several minutes to a maximum. In many patients, the DOHB signal subsequently declined back toward baseline, representing the effects of compensatory cerebral vasoconstriction. The delay time was shorter in anemic subjects because of increased cerebral blood flow, but the rise times were not different. Peak DOHB increase was greater in SCD patients than in ACTL or non anemic control subjects (1.4 mM ± 0.2mM, 0.8 mM ± 0.2 mM and 0.6 mM ± 0.4 mM, respectively, p <0.0001 by ANOVA). There was no difference in the DOHB vasoconstriction response among the three patient groups.DOHB was highly correlated with DDHB and DTOI in all three patient groups. Consequently, both DDHB and DTOI changes were also larger in SCD patients. All three NIRs signal changes were larger in non-transfused SCD patients than in patients on chronic transfusions. Non-transfused SCD patients had more significant increases in SpO2% than chronically transfused subjects and the effect was proportional to hemoglobin F%, suggesting a p50 effect. After controlling for SpO2%, SCD patients still exhibited larger NIRs changes than ACTL or CTL patients, but the differences between transfused and non transfused SCD patients disappeared.Whole brain %BOLD was also correlated with changes in DOHB, DDHB, TOI, and SpO2%. The relationship between DOHB versus %BOLD is illustrated in Figure 2. %BOLD changes were also significantly higher in SCD patients. However, unlike the NIRS changes, whole brain %BOLD differences could entirely be explained by differences in SpO2% with hyperoxia.Conclusion:100% oxygen administration increases brain oxygenation in SCD patients to a greater degree than in control subjects or patients with anemia of other etiologies. Some of the differences can be explained by differences in resting oxygen saturations but disparities between BOLD and NIRs response suggest regional variation of brain oxygenation in response to this challenge. [Display omitted] [Display omitted] DisclosuresWood:Apopharma: Consultancy; AMAG: Consultancy; World Care Clinical: Consultancy; AMAG: Consultancy; Celgene: Consultancy; Apopharma: Consultancy; Biomed Informatics: Consultancy; Celgene: Consultancy; Ionis Pharmaceuticals: Consultancy; Vifor: Consultancy; Vifor: Consultancy; Ionis Pharmaceuticals: Consultancy; Biomed Informatics: Consultancy; World Care Clinical: Consultancy.

Shear-Mediated Erythrocyte Nitric Oxide Production Is Differentially Regulated in Patients with Sickle Cell Disease

Introduction: Sickle cell disease (SCD) is an inherited hemoglobinopathy in which hemoglobin polymerizes when deoxygenated, causing increased red blood cell (RBC) stiffness and RBC sickling. This leads to microcirculatory slowing and occlusion, in turn causing vaso-occlusive crises acutely and microcirculatory damage chronically. RBC are known to signal blood vessels in the microcirculation, regulating vessel tone. Nitric oxide (NO) is a potent vasodilator and key regulator of vascular smooth muscle tone throughout the vasculature. However, the possibility that RBC make NO and that this might contribute to vascular tone, particularly in arterioles is controversial. Modulation of RBC NO production due to deformation of RBC by shear stress could have important physiological consequences in SCD where RBC deformability is decreased and dependent on the polymerization state of hemoglobin S.Objective: To determine if shear stress induced deformation induces change in NO production in individual RBC and if the magnitude and time course of this NO differs between RBC from patients with sickle cell disease and normal controls.Methods: NO production was measured using imaging microscopy of fluorescently labeled RBC exposed to shear after being allowed to adhere to a flow chamber attached to the microscope stage. Four SCD patients on simple chronic transfusion therapy, 4 SCD patients not on chronic transfusion therapy and 4 healthy control subjects were recruited from the hematology clinics at Children's Hospital Los Angeles under an IRB approved protocol. RBC underwent histopaque separation then washed 3x and resuspended in KRP buffer. The RBC were then incubated with 4 micromolar DAF-FM Diacetate (4-Amino-5-Methylamino-2',7'-Difluorofluorescein Diacetate, ThermoFisher Scientific), a fluorescent indicator related to NO production. RBC were then exposed to three experimental conditions: 1. buffer alone; 2. 1 milimolar arginine (substrate for NOS NO production); 3. 1 milimolar arginine and 1 milimolar L-NAME (a non-specific NOS inhibitor). The RBC were placed in poly L-lysine coated microfluidic chambers and placed under no shear conditions for 30 minutesk, then sheared at 0.5Pa for 30minutes. Individual cell analysis was performed using Image J analysis software (FIJI).Results: There is a slow baseline rise of NO fluorescent signal without exposure to shear and there is a large, acute increase in NO fluorescent signal with exposure to shear stress. (figure 1) The baseline fluorescent rate of rise is increased in non-transfused sickle cell subjects (p<0.0001) compared to transfused SCD patients and healthy control subjects, suggesting higher basal rate of NO production. (figure 2) We found a significant increase in fluorescence in response to shear in all three groups, with the transfused SCD patients showing a higher rate of change and higher magnitude fluorescence response. (figure 1) Addition of arginine increased the shear induced NO production in all three groups (P<0.05). The baseline NO related fluorescence was blunted with the addition of L-NAME in healthy subjects, whereas it was unchanged in both the transfused and non-transfused SCD groups. There was no significant change in shear-mediated NO related DAF fluorescence after L-NAME was added.Discussion: The results here indicate that RBC produce NO upon shear and the basal rate of NO production is higher in non-transfused patients with sickle cell disease. Addition of arginine increases both the magnitude and rate of NO production in all three groups. SCD patients on chronic transfusion therapy demonstrate a larger increase in NO response to shear. The increased response of NO related fluorescence with the addition of arginine suggests NOS has a role in shear mediated RBC NO production; however, L-NAME blockade does not significantly blunt the response in the presence of arginine. Shear induced RBC NO production may play an important role in regulation of microvascular profusion and would likely be modulated by the RBC deformability differences due to HbS polymerization.Conclusion: There is basal and shear dependent NO production in both AA and SCD RBC, and RBC NOS is differentially regulated in SCD and AA RBC. [Display omitted] [Display omitted] DisclosuresWood:Ionis Pharmaceuticals: Consultancy; Ionis Pharmaceuticals: Consultancy; Vifor: Consultancy; Vifor: Consultancy; World Care Clinical: Consultancy; World Care Clinical: Consultancy; Celgene: Consultancy; Celgene: Consultancy; AMAG: Consultancy; AMAG: Consultancy; Apopharma: Consultancy; Apopharma: Consultancy; Biomed Informatics: Consultancy; Biomed Informatics: Consultancy.

Assessing cardiac and liver iron overload in chronically transfused patients with sickle cell disease.

Transfusional iron overload represents a substantial challenge in the management of patients with sickle cell disease (SCD) who receive chronic or episodic red blood cell transfusions. Iron-induced cardiomyopathy is a leading cause of death in other chronically transfused populations but rarely seen in SCD. Study objectives were to: (i) examine the extent of myocardial and hepatic siderosis using magnetic resonance imaging (MRI) in chronically transfused SCD patients, and (ii) evaluate the relationship between long-term (over the 5years prior to enrolment) mean serum ferritin (MSF), spot-ferritin values and liver iron content (LIC) measured using MRI and liver biopsy. Thirty-two SCD patients (median age 15years) with transfusional iron overload were recruited from two U.S. institutions. Long-term MSF and spot-ferritin values significantly correlated with LIC by MRI-R2* (r=0·77, P<0·001; r=0·82, P<0·001, respectively). LIC by MRI-R2* had strong positive correlation with LIC by liver biopsy (r=0·98, P<0·001) but modest inverse correlation with cardiac MRI-T2* (r=-0·41, P=0·02). Moderate to severe transfusional iron overload in SCD was not associated with aberrations in other measures of cardiac function based on echocardiogram or serum biomarkers. Our results suggest that SCD patients receiving chronic transfusions may not demonstrate significant cardiac iron loading irrespective of ferritin trends, LIC and erythropoiesis suppression.

Enhanced MRI Evaluation of Children with Sickle Cell Following Hematopoietic Stem Cell Transplantation

Introduction: Sickle cell disease (SCD) CNS vasculopathy (SCNSV) is a frequent indication for hematopoietic stem cell transplantation (HSCT). Untreated, SCNSV can be progressive and impair quality of life (QoL) and cognitive functioning. By clinical MRI/MRA assessment, HSCT is thought to halt progression of SCNSV. Quantitative analysis of T2-weighted FLAIR MRI for white matter hyperintensity (WMH) can provide a meaningful estimate of small vessel cerebrovascular burden. Adding WMH assessment, we asked whether HSCT for SCD halted long-term progression of SCNSV, including small vessel involvement, despite transplant-associated CNS risks. QoL assessment can track school functioning and physical, emotional and social functioning.Methods: This retrospective single site study compared MRI analyses pre-transplant to 1-7-years post-HSCT. Subject eligibility required availability of clinical MRI scans from within 2 months pre-HSCT and at 1-year intervals for at least one year post-HSCT. Interim scans performed for acute clinical indications were not included in the analysis. MRI scans were evaluated independent to the initial clinical read by one neuroradiologist, and via in-house developed software to quantitate WMH burden. QoL was completed by parent- and child-report pre-HSCT and annually thereafter using the Peds QL 4.0TM with scores 0-100; higher numbers reflected higher QoL.Results: 25 patients who received HSCT for SCD between 2003-2014 were evaluated. Median age at HSCT was 9.9 years (1.4-21.9); male:female 18:7; HbSS (17), HbSC (3), HbS-Bthalassemia (5). Donors were related (14) or unrelated (11). Stem cell sources were: related bone marrow (BM) (10), unrelated BM (5), related cord blood (CB) (3), unrelated CB (6), or related peripheral blood stem cells (1). Eight patients had CNS pathology as the indication for HSCT. Transplant complications were: PRES (2), stroke (1), graft failure (2), death (1). Duration of follow-up was: 1 yr (9), 2 yrs (10), >2 yrs (6). Only a minority of patients had normal pre-HSCT MRI (5) and normal MRA (11; 6 had 1-2 stenoses <2mm and were rated as ambiguous). At 1 to 7 yrs post-HSCT, 5 originally normal MRIs were unchanged, 15 MRIs were stable and 4 were improved at 1 year post-HSCT, without subsequent changes by clinical assessment. One MRI worsened due to peri-HSCT hemorrhagic stroke. MRAs were unchanged following HSCT. Preliminary analysis of 18 patients at pre-HSCT revealed that 5 did not have elevated WMH, while elevated WMH was detected in 13 patients. WMH remained stable in 16 of 18 patients over subsequent annual assessments. In the 2 patients with markedly elevated WMH pre-HSCT, values decreased at follow-up, corresponding to the resolution of acute or recent infarction. Overall pre-HSCT QoL by parent-report (N=19) was 65.3 (SD16.3); while child self-report (N=14) was 67.6, (SD13.1). After mean follow-up of 3 years, parent-report QoL improved to 78.8 (SD15.8), and self-report to 78.7 (SD15.2).Conclusions: Most children in this retrospective cohort had MRI abnormalities pre-HSCT, and all but 1 were stable or improved post-HSCT, despite PRES and other potential CNS complications. Pre-HSCT WMH appeared to be unchanged for most of these patients, while stroke-induced WMH appears to decrease over time, suggesting stable small vessel SCNSV following transplantation. Overall, by MRI/MRA and by preliminary WMH, HSCT appears to have stabilized large and small vessel SCNSV in all but 1 of 25 children. While only a modest number of patients were assessed, WMH was reproducible at multiple annual time points. Long-term parent and self-reported QoL indicated improvement from HSCT. Chronically transfused SCD patients could not be compared due to lack of annualized assessment. Future transplant protocols will include enhanced MRI-based tracking, in conjunction with QoL and neuropsychological assessments. These data could be useful for decision-making about SCD transplantation. DisclosuresNo relevant conflicts of interest to declare.