Hematopoietic cell transplantation for thalassemia and sickle cell disease: past, present and future

A Review of Gene Therapies for Hemoglobinopathies

Due to the significant morbidity and mortality of hemoglobinopathies, curative options have long been pursued. The overall goal of gene therapy is to modify a patient's own hematopoietic stem cells to overcome the deleterious effects of the underlying genetic defect by gene addition, gene editing, or gene silencing. Gene addition incorporates genes with superior function than the abnormal gene; gene editing takes advantage of molecular tools such as zinc finger proteins, Transcription Activator-Like Effector Nucleases and Clustered Regularly Interspaced Short Palindromic Repeats coupled with Cas9 proteins (CRISPR-Cas9) which allow for sequence-specific breaks in DNA that disrupt gene function; and gene silencing suppresses gene expression by interference with mRNA transcription/protein translation or epigenetic modification. The majority of gene therapy strategies for hemoglobinopathies have targeted erythroid-specific BCL11A, a major regulator of fetal hemoglobin repression at the gamma-globin locus, in the normal fetal-to-adult hemoglobin switch that occurs shortly after birth. Other goals have involved the incorporation of anti-sickling globins, such as βT87Q or βAS3. Landmark clinical trials of gene therapy in transfusion-dependent thalassemia and sickle cell disease have shown remarkable efficacy and acceptable safety and culminated in recent regulatory approvals of gene therapy for both diseases in Europe and the United States.

Experiences and strategies of people with sickle cell disease in the Federal District: the biographical rupture

This is a study on sickle cell disease, a chronic illness that affects many Brazilians, that aims to understand and analyze how people address the adversities arising from the diagnosis and the biographical rupture. The description of people's experiences and strategies conjures a picture that expresses the respondents' habitus, built in a dialectical relationship with the vulnerability determined by the disease. We adopted a qualitative approach and focused interviews as proposed by Merton, combined with the snowball technique, applied to groups related to sickle cell disease on social networks. Seven participants were selected because they were privileged informants with the disease, were over eighteen, lived in the Federal District, and were non-exclusive users of the Unified Health System. The interview material was categorized from the focal groups employed. The results indicated the following categories: biographical rupture, experience and coping strategies, and healthcare. It is necessary to sensitize professionals and the population about the challenging living conditions of people with sickle cell disease and the consolidation of public policies and care networks to accommodate this population.

Applications and Research Advances in the Delivery of CRISPR/Cas9 Systems for the Treatment of Inherited Diseases

The rapid advancements in gene therapy have opened up new possibilities for treating genetic disorders, including Duchenne muscular dystrophy, thalassemia, cystic fibrosis, hemophilia, and familial hypercholesterolemia. The utilization of the clustered, regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated protein (Cas) system has revolutionized the field of gene therapy by enabling precise targeting of genes. In recent years, CRISPR/Cas9 has demonstrated remarkable efficacy in treating cancer and genetic diseases. However, the susceptibility of nucleic acid drugs to degradation by nucleic acid endonucleases necessitates the development of functional vectors capable of protecting the nucleic acids from enzymatic degradation while ensuring safety and effectiveness. This review explores the biomedical potential of non-viral vector-based CRISPR/Cas9 systems for treating genetic diseases. Furthermore, it provides a comprehensive overview of recent advances in viral and non-viral vector-based gene therapy for genetic disorders, including preclinical and clinical study insights. Additionally, the review analyzes the current limitations of these delivery systems and proposes avenues for developing novel nano-delivery platforms.

Genotypic and Phenotypic Composition of Sickle Cell Disease in the Arab Population - A Systematic Review

Sickle cell disease (SCD) is a genetic disease influenced by ethnicity and regional differences in its clinical course. Recent advances in the management of SCD with newer therapies are being introduced to the Western population. However, many of these treatments are yet to be used in the Arabic SCD population. Understanding the genetic variations of SCD regionally is essential to anticipate the utilization of new treatments. This systematic review's main objective is to pool the available data on the genetic composition of SCD in the Arabic population. Data for 44,034 patients was extracted from 184 studies (11 case reports, 8 case series, 56 retrospectives, 107 prospective observational studies, and 2 clinical trials) using PubMed, Scopus, and Google Scholar. Male (49%) and female (51%) patients were equally reported wherever gender was available (N=13105). Various SCD genotypes were reported in a total of 14,257 patients, including Hb SS (77%) Hb Sβ0 (9.9%), and Hb Sβ+ (7.2%), while the rest of the genotypes, including HbSC, HbSD, HbSE, HbSO Arab, Hb S/α-Thal, Hb Sβ0 + α-Thal, and HBS Oman were individually reported in <4% of the cases. Major SCD complications in the Arab population included pain crises (48.25%) followed by neurological complications (33.46%), hepatobiliary complications (25.53%), musculoskeletal complications (24.73%), and hemolytic anemia (23.57%). The treatments reported for SCD included hydroxyurea (20%), blood transfusion (14.32%), and Deferasirox (3.03%). We did not find the use of stem cell transplantation or newer treatments such as L-Glutamine, Voxelotor, Crizanlizumab, or gene therapy reported in any of the studies included in our review. This review highlights the genetic makeup of SCD in Arab countries and its common phenotypic manifestations and will help direct further research on SCD in this region, especially concerning genetic therapy.

Systematic Review Registration

The protocol has been registered in the International Prospective Register of Systematic Reviews(PROSPERO):CRD42020218,666. https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=218666.

Kruppel-like factor 1-GATA1 fusion protein improves the sickle cell disease phenotype in mice both in vitro and in vivo

Sickle cell disease (SCD) and β-thalassemia are among the most common genetic disorders worldwide, affecting global health and mortality. Hemoglobin A2 (HbA2, α2δ2) is expressed at a low level in adult blood due to the lack of the Kruppel-like factor 1 (KLF1) binding motif in the δ-globin promoter region. However, HbA2 is fully functional as an oxygen transporter, and could be a valid antisickling agent in SCD, as well as a substitute for hemoglobin A in β-thalassemia. We have previously demonstrated that KLF1-GATA1 fusion protein could interact with the δ-globin promoter and increase δ-globin expression in human primary CD34+ cells. We report the effects of 2 KLF1-GATA1 fusion proteins on hemoglobin expression, as well as SCD phenotypic correction in vitro and in vivo. Forced expression of KLF1-GATA1 fusion protein enhanced δ-globin gene and HbA2 expression, as well as reduced hypoxia-related sickling, in erythroid cells cultured from both human sickle CD34+ cells and SCD mouse hematopoietic stem cells (HSCs). The fusion proteins had no impact on erythroid cell differentiation, proliferation, and enucleation. Transplantation of highly purified SCD mouse HSCs expressing KLF1-GATA1 fusion protein into SCD mice lessened the severity of the anemia, reduced the sickling of red blood cells, improved SCD-related pathological alterations in spleen, kidney, and liver, and restored urine-concentrating ability in recipient mice. Taken together, these results indicate that the use of KLF1-GATA1 fusion constructs may represent a new gene therapy approach for hemoglobinopathies.

Ex vivo expansion and functional activity preservation of adult hematopoietic stem cells by a diarylheptanoid from Curcuma comosa

Hematopoietic stem cells (HSCs, CD34+ cells) have shown therapeutic efficacy for transplantation in various hematological disorders. However, a large quantity of HSCs is required for transplantation. Therefore, strategies to increase HSC numbers and preserve HSC functions through ex vivo culture are critically required. Here, we report that expansion medium supplemented with ASPP 049, a diarylheptanoid isolated from Curcuma comosa, and a cocktail of cytokines markedly increased numbers of adult CD34+ cells. Interestingly, phenotypically defined primitive HSCs (CD34+CD38-CD90+) were significantly increased under ASPP 049 treatment relative to control. ASPP 049 treatment also improved two functional properties of HSCs, as evidenced by an increased number of CD34+CD38- cells in secondary culture (self-renewal) and the growth of colony-forming units as assessed by colony formation assay (multilineage differentiation). Transplantation of cultured CD34+ cells into immunodeficient mice demonstrated the long-term reconstitution and differentiation ability of ASPP 049-expanded cells. RNA sequencing and KEGG analysis revealed that Hippo signaling was the most likely pathway involved in the effects of ASPP 049. These results suggest that ASPP 049 improved ex vivo expansion and functional preservation of expanded HSCs. Our findings provide a rationale for the use of ASPP 049 to grow HSCs prior to hematological disease treatment.

Hematopoietic-Stem-Cell-Targeted Gene-Addition and Gene-Editing Strategies for β-hemoglobinopathies

Sickle cell disease (SCD) is caused by a well-defined point mutation in the β-globin gene and therefore is an optimal target for hematopoietic stem cell (HSC) gene-addition/editing therapy. In HSC gene-addition therapy, a therapeutic β-globin gene is integrated into patient HSCs via lentiviral transduction, resulting in long-term phenotypic correction. State-of-the-art gene-editing technology has made it possible to repair the β-globin mutation in patient HSCs or target genetic loci associated with reactivation of endogenous γ-globin expression. With both approaches showing signs of therapeutic efficacy in patients, we discuss current genetic treatments, challenges, and technical advances in this field.

Limitations of Applying the Hematopoietic Cell Transplantation Comorbidity Index in Pediatric Patients Receiving Allogeneic Hematopoietic Cell Transplantation

Identifying which patients are at high risk for transplant-related mortality, prior to allogeneic hematopoietic cell transplantation (alloHCT), is crucial both to guide decision making with patients and families and to inform the alloHCT approach. There is a paucity of data evaluating the utility of the HCT comorbidity index (HCT-CI) in pediatric patients. We performed a retrospective cohort study of 188 patients who underwent alloHCT between January 2008 and October 2016 and assessed pretransplant comorbidities defined and weighted by the HCT-CI. The primary endpoint of our study was overall survival (OS). Kaplan-Meier method was used to assess survival estimates at 1-year post-transplant and did not differ based on HCT-CI scores: 78.7% (SE 6.69%) for HCT-CI = 0, 74.7% (SE 6.33%) for HCT-CI = 1 to 2, and 77.3% (SE 4.17%) for HCT-CI ≥3. Multivariable Cox proportional hazards analysis did not show HCT-CI having an effect on OS: hazard ratio (HR) of 0.633 (95% confidence interval [CI], 0.297 to 1.347) for HCT-CI scores 1 to 2 and HR of 0.935 (95% CI, 0.456 to 1.918) for HCT-CI scores ≥3 compared to scores of 0. The most frequent comorbidities observed were hepatic disease (mild in 29%, severe in 23%) and pulmonary disease (moderate in 15% and severe in 29%). However, only 55% were able to complete pulmonary function testing. Hepatic disease was based on transaminitis in 48% and by bilirubin alone in 26% of patients; 46% of patients with hepatic dysfunction had an underlying hemoglobinopathy and hyperbilirubinemia related to ongoing hemolysis. This study evaluates HCT-CI comorbidities in greater detail than has been performed previously in children undergoing alloHCT. We identify challenges with the HCT-CI in the pediatric population and highlight the comorbidities that may benefit from adjustments to their definition to create an improved risk assessment tool for children.

How to setup a successful transplant program for hemoglobinopathies in developing countries: The Cure2Children approach

Hematopoietic stem cell transplantation (HSCT) remains the only established definitive cure for severe hemoglobinopathies, such as sickle cell disease (SCD) and thalassemia-the most prevalent life-threatening non-communicable disease of childhood globally. HSCT can not only cure over 85% of children with a compatible sibling but also restore normal health-related quality of life in most cases who do not have major irreversible organ damage at transplant. In low- and middle-income countries (LMICs), particularly in sub-Saharan Africa, SCD carrier rate can be up to 30% and 1% of live births have SCD. Relatively simple and inexpensive measures such as newborn screening, early diagnosis, caregiver education, and timely institution of anti-pneumococcal prophylaxis and hydroxyurea therapy can substantially reduce SCD-related mortality and morbidity. Improved prevention and early care should proceed in parallel with the development of transplant services and hope for cure. Cure2Children, an Italian NGO, has supported the startup of several bone marrow transplantation programs in LMICs where over 500 transplants have been performed over the last 10 years, with outcomes not substantially different from high-income countries but at a fraction of the cost. This report summarizes this experience and suggests some strategies to set up new HSCT units.

Is There Any Improvement of the Coagulation Imbalance in Sickle Cell Disease after Hematopoietic Stem Cell Transplantation?

Several components of the clotting system are modified towards hypercoagulability in sickle cell disease (SCD). To date, hematopoietic stem cell transplantation (HSCT) is the only validated curative treatment of SCD. Here, we investigated the changes in the hemostatic potential of SCD children who've received a successful HSCT. Seventeen children with severe SCD were enrolled in the study. Thrombin generation (TG) was performed on citrated platelet-poor plasma, obtained before and 3, 6, 9, 12 and 15 months after HSCT. TG was triggered using 1 pM tissue factor and 4 µM phospholipids with or without thrombomodulin (TM). Before the HSCT, SCD children showed a higher endogenous thrombin potential (ETP), higher peak, higher velocity and shorter time-to-peak of TG than the normal controls (NC). ETP did not significantly change following the HSCT. However, the peak, velocity and time-to-peak of TG reversed to normal ranges from 3 months post-HSCT and remained so up to 15 months post-HSCT. The reduction of ETP after the addition of thrombomodulin (RETP) was dramatically reduced in SCD children before HSCT as compared with the NC. A partial reversal of RETP was observed from 3 months through 15 months post-HSCT. No statistical difference was observed for patient age or donor hemoglobinopathy status. In summary, successful HSCT improves the kinetics of TG but not the total thrombin capacity in SCD children.

Extensive multilineage analysis in patients with mixed chimerism after allogeneic transplantation for sickle cell disease: insight into hematopoiesis and engraftment thresholds for gene therapy

Although studies of mixed chimerism following hematopoietic stem cell transplantation in patients with sickle cell disease (SCD) may provide insights into the engraftment needed to correct the disease and into immunological reconstitution, an extensive multilineage analysis is lacking. We analyzed chimerism simultaneously in peripheral erythroid and granulomonocytic precursors/progenitors, highly purified B and T lymphocytes, monocytes, granulocytes and red blood cells (RBC). Thirty-four patients with mixed chimerism and ≥12 months of follow-up were included. A selective advantage of donor RBC and their progenitors/precursors led to full chimerism in mature RBC (despite partial engraftment of other lineages), and resulted in the clinical control of the disease. Six patients with donor chimerism <50% had hemolysis (reticulocytosis) and higher HbS than their donor. Four of them had donor chimerism <30%, including a patient with AA donor (hemoglobin >10 g/dL) and three with AS donors (hemoglobin <10 g/dL). However, only one vaso-occlusive crisis occurred with 68.7% HbS. Except in the patients with the lowest chimerism, the donor engraftment was lower for T cells than for the other lineages. In a context of mixed chimerism after hematopoietic stem cell transplantation for SCD, myeloid (rather than T cell) engraftment was the key efficacy criterion. Results show that myeloid chimerism as low as 30% was sufficient to prevent a vaso-occlusive crisis in transplants from an AA donor but not constantly from an AS donor. However, the correction of hemolysis requires higher donor chimerism levels (i.e ≥50%) in both AA and AS recipients. In the future, this group of patients may need a different therapeutic approach.

Parent and Guardian Knowledge of Hematopoietic Cell Transplantation as a Treatment Option for Sickle Cell Disease

Beginning early in childhood, patients with sickle cell disease (SCD) are at risk of life-threatening and debilitating health events. Despite the high morbidity and mortality of this disease, hematopoietic cell transplantation (HCT), a curative treatment for SCD, remains underutilized. In the literature there is a paucity of data concerning medical decision maker (MDM) awareness of HCT as a treatment option for SCD. The objective of this study was to estimate the proportion of parents/guardians of children with SCD who are aware of HCT as a treatment option, and to identify the demographic factors associated with knowledge of this therapy's curative potential. Between November 2015 and December 2016, 327 parents/guardians were surveyed across 4 clinical sites in 3 Midwestern US cities. Although 82% of parents/guardians had heard of HCT in the past and 78% were aware of the therapy's curative potential, nearly half indicated that they did not know whether HCT could specifically cure their child of the disease. Respondents who had discussed HCT with their child's physician had 5 times higher odds of being aware of HCT's curative potential than those who had not. These findings suggest that additional efforts to enhance MDM knowledge of HCT as well as shared decision making in the use of this therapy, is warranted.

The Hematopoietic Cell Transplant Comorbidity Index predicts survival after allogeneic transplant for nonmalignant diseases

Despite improvements, mortality after allogeneic hematopoietic cell transplantation (HCT) for nonmalignant diseases remains a significant problem. We evaluated whether pre-HCT conditions defined by the HCT Comorbidity Index (HCT-CI) predict probability of posttransplant survival. Using the Center for International Blood and Marrow Transplant Research database, we identified 4083 patients with nonmalignant diseases transplanted between 2007 and 2014. Primary outcome was overall survival (OS) using the Kaplan-Meier method. Hazard ratios (HRs) were estimated by multivariable Cox regression models. Increasing HCT-CI scores translated to decreased 2-year OS of 82.7%, 80.3%, 74%, and 55.8% for patients with HCT-CI scores of 0, 1 to 2, 3 to 4, and ≥5, respectively, regardless of conditioning intensity. HCT-CI scores of 1 to 2 did not differ relative to scores of 0 (HR, 1.12 [95% CI, 0.93-1.34]), but HCT-CI of 3 to 4 and ≥5 posed significantly greater risks of mortality (HR, 1.33 [95% CI, 1.09-1.63]; and HR, 2.31 [95% CI, 1.79-2.96], respectively). The effect of HCT-CI differed by disease indication. Patients with acquired aplastic anemia, primary immune deficiencies, and congenital bone marrow failure syndromes with scores ≥3 had increased risk of death after HCT. However, higher HCT-CI scores among hemoglobinopathy patients did not increase mortality risk. In conclusion, this is the largest study to date reporting on patients with nonmalignant diseases demonstrating HCT-CI scores ≥3 that had inferior survival after HCT, except for patients with hemoglobinopathies. Our findings suggest that using the HCT-CI score, in addition to disease-specific factors, could be useful when developing treatment plans for nonmalignant diseases.

Gene therapy for sickle cell disease: An update

Sickle cell disease (SCD) is one of the most common life-threatening monogenic diseases affecting millions of people worldwide. Allogenic hematopietic stem cell transplantation is the only known cure for the disease with high success rates, but the limited availability of matched sibling donors and the high risk of transplantation-related side effects force the scientific community to envision additional therapies. Ex vivo gene therapy through globin gene addition has been investigated extensively and is currently being tested in clinical trials that have begun reporting encouraging data. Recent improvements in our understanding of the molecular pathways controlling mammalian erythropoiesis and globin switching offer new and exciting therapeutic options. Rapid and substantial advances in genome engineering tools, particularly CRISPR/Cas9, have raised the possibility of genetic correction in induced pluripotent stem cells as well as patient-derived hematopoietic stem and progenitor cells. However, these techniques are still in their infancy, and safety/efficacy issues remain that must be addressed before translating these promising techniques into clinical practice.

Acute pain crisis in a patient with sickle cell disease undergoing ovarian simulation for fertility preservation prior to curative stem cell transplantation: case report and literature review

PURPOSE

Hematopoietic stem cell transplantation (HSCT) is a cure for sickle cell disease (SCD) but frequently results in permanent sterility. The complications associated with oocyte cryopreservation and risks of future pregnancy are increased in SCD patients. This case report discusses risk reduction strategies and includes a literature review of pregnancy after HSCT.

CASE

A 23-year-old woman underwent ovarian stimulation for fertility preservation resulting in cancelation due to acute pain crisis. She underwent a successful oocyte retrieval after exchange transfusion to decrease her hemoglobin S to 30%. This is the second report of a pain crisis in a woman with SCD undergoing oocyte banking.

CONCLUSION(S)

Women with SCD undergoing fertility preservation may be at increased risk of complications from ovarian stimulation. Risks in pregnancy after HSCT should also be considered before proceeding with fertility preservation.

Gene Therapy in a Patient with Sickle Cell Disease

Sickle cell disease results from a homozygous missense mutation in the β-globin gene that causes polymerization of hemoglobin S. Gene therapy for patients with this disorder is complicated by the complex cellular abnormalities and challenges in achieving effective, persistent inhibition of polymerization of hemoglobin S. We describe our first patient treated with lentiviral vector-mediated addition of an antisickling β-globin gene into autologous hematopoietic stem cells. Adverse events were consistent with busulfan conditioning. Fifteen months after treatment, the level of therapeutic antisickling β-globin remained high (approximately 50% of β-like-globin chains) without recurrence of sickle crises and with correction of the biologic hallmarks of the disease. (Funded by Bluebird Bio and others; HGB-205 ClinicalTrials.gov number, NCT02151526 .).

Hydroxycarbamine: from an Old Drug Used in Malignant Hemopathies to a Current Standard in Sickle Cell Disease

While hydroxycarbamide (hydroxyurea, HU) has less and fewer indications in malignant hemopathies, it represents the only widely used drug which modifies sickle cell disease pathogenesis. Clinical experience with HU for patients with sickle cell disease has been accumulated over the past 25 years in Western countries. The review of the literature provides increasing support for safety and efficacy in both children and adults for reducing acute vaso-occlusive events including pain episodes and acute chest syndrome. No increased incidence of leukemia and teratogenicity was demonstrated. HU has become the standard-of-care for sickle cell anemia but remains underused. Barriers to its use should be identified and overcome.

Enhanced Long-Term Brain Magnetic Resonance Imaging Evaluation of Children with Sickle Cell Disease after Hematopoietic Cell Transplantation

Progressive neurovasculopathy in children with sickle cell disease (SCD) results in decreased cognitive function and quality of life (QoL). Hematopoietic cell transplantation (HCT) is believed to halt progression of neurovasculopathy. Quantitative analysis of T2-weighted fluid attenuated inversion recovery (FLAIR) magnetic resonance imaging (MRI) for white matter hyperintensity (WMH) burden provides a meaningful estimate of small vessel cerebrovascular disease. We asked if quantitative analysis of WMH could complement standardized clinical assessment of MRI/magnetic resonance angiography (MRA) for assessing SCD central nervous system vasculopathy before and after HCT. Retrospective longitudinal clinical examination of scheduled annual MRI/MRA and quantitative analysis of WMH were performed before and 1 to 7 years after HCT at scheduled annual intervals, along with QoL measurements, in children who had engrafted after HCT. Of 18 patients alive and persistently engrafted (median age, 9.1 years), pretransplantation MRI demonstrated that 9 and 5 had sickle-related stroke and/or small infarcts, respectively. Patients were divided into WMH severity tertiles based on pretransplantation WMH volumes. MRI and WMH were assessed 1 to 7 years after HCT. MRI/MRA and WMH volume were stable or slightly better in 17 of 18 patients. By parent- and self-report, post-HCT QoL improved for children in the lowest WMH tertile significantly more than in the other groups. Based on this single-institution retrospective sample, we report that WMH appears to quantitatively support MRI-based findings that HCT stabilizes long-term small and large vessel cerebrovascular changes and is associated with the degree of improved QoL. While confirmation in larger prospective studies and evaluation by neurocognitive testing are needed, these findings suggest that WMH is a useful biomarker of neurovasculopathy after transplantation for SCD.

Favorable outcomes after in utero transfusion in fetuses with alpha thalassemia major: a case series and review of the literature

OBJECTIVE

Alpha thalassemia major (ATM) is often fatal in utero due to severe hydrops fetalis. Although in utero transfusions (IUTs) are increasingly used to allow fetal survival in ATM, prenatal and postnatal outcomes are not well described.

METHODS

We retrospectively reviewed cases of ATM at our institution treated with consecutive IUT. Clinical records were reviewed for transfusion history, neurodevelopmental outcomes, anatomic abnormalities, survival to hematopoietic cell transplantation, and transfusion independence. A systematic review was performed, and additional reported cases are discussed.

RESULTS

Three patients who underwent IUT for ATM were identified, and review of the literature revealed 17 reported cases. Of patients who received IUT, reported neurodevelopmental deficits occurred in 29% (4/14) and anatomic abnormalities in 55% (11/20). Four patients eventually underwent successful hematopoietic cell transplantation. Transfusion volumes were less than suggested guidelines for other causes of fetal anemia in 91.7% of the transfusions.

CONCLUSION

This series demonstrates the potential for achieving full fetal development with normal neurologic outcomes in those affected by ATM. It provides support for continued patient and provider education about current benefits and risks of active prenatal therapy for fetuses with ATM, as well as continued research to optimize therapeutic strategies such as in utero transplantation. © 2016 John Wiley & Sons, Ltd.

Magnetic resonance imaging in pediatric sickle cell anemia

Sickle cell disease is the result of altered genetic make up due to hereditary encounter and its form as homozygous sickle cell anemia is the most common and severe. The disease is characterized by chronic anemia, recurrent pain crises and vascular occlusion. Neurologically, there is a high incidence of stroke in childhood, as well as cognitive dysfunction. Newborn screening programmes and preventative treatments have allowed a much longer lifespan. However, recently, neurological research has shifted to characterizing more subtle aspects of brain development and functioning that may be critically important to the individual's quality of life. The present review article examines the neurological and neurocognitive complications of sickle cell disease, and discusses the importance of magnetic resonance imaging scans in the management of the disease.

Allogeneic Stem Cell Transplantation in Congenital Hemoglobinopathies Using a Tailored Busulfan-Based Conditioning Regimen: Single-Center Experience

Hematopoietic stem cell transplantation (HSCT) is the only proven curative option for patients with hemoglobinopathies, both thalassemia and sickle cell anemia (SCA). A busulfan-based myeloablative conditioning regimen is the standard of care for HSCT in these patients, although increased treatment-related morbidity, including veno-occlusive disease (VOD), has been demonstrated. Thirty-eight pediatric patients, median age 8 years (range, 6 months to 22 years), suffering from hemoglobinopathy were treated at Rambam Medical Center in Haifa, Israel, between 1998 and 2011. Thirty-four patients had thalassemia major and 4 had SCA. The 38 patients underwent 40 HSCTs, 34 of which were first transplants and 6 second transplants. Most transplants (32/40) were from matched sibling donors. Sources of stem cells were peripheral blood in 30 transplants, bone marrow in 7 transplants, and cord blood in 3 transplants. All received different customized busulfan-based conditioning regimens tailored by pharmacokinetic analysis of busulfan levels. Primary engraftment occurred in 37 of 40 transplants. Neutrophil engraftment (>.5 × 10(9)/L) occurred at a median of 15.3 days post-transplantation (range, 10 to 45). Platelet transfusion independence (>20 × 10(9)/L) occurred at a median of 22.3 days (range, 11 to 60). The rate of 5-year overall survival for thalassemia patients after first transplantation was 90.5% ± 5.3%. The rate of 5-year thalassemia-free survival was 81.7% ± 6.8%. Cumulative incidence of acute graft-versus-host disease (GVHD) was 17.6%. Rate of grades III to IV GVHD was 8.8%. Cumulative incidence of chronic GVHD was 23.5%, with 11.8% incidence of extensive chronic GVHD. One patient developed VOD. Full donor chimerism occurred in 36.4% of patients with class 1 + 2 thalassemia, compared with 78.6% in class 3 thalassemia (P = .049). Overall survival above 90% in patients undergoing their first transplant was demonstrated using busulfan-based conditioning regimens. The low incidence of VOD was probably due to busulfan area under the curve measurements and dose adjustment.

Hematopoietic stem cell transplantation from non-sibling matched family donors for patients with thalassemia major in Jordan

There are limited data on the outcome of patients with thalassemia receiving HSCT from non-sibling matched family donors. Of the 341 patients with thalassemia major that underwent donor search at our center from January 2003 to December 2011, 236 (69.2%) had fully matched family donor of which 28 patients (8.2%) had non-sibling matched family donors identified. We report on seven patients with a median age of eight yr (4-21) who underwent myeloablative (n = 4) or RIC (n = 3) HSCT. The median age of the donors was 33 yr (4-47), three were parents, two first cousins, one paternal uncle, and one paternal aunt. All patients achieved primary neutrophil and platelet engraftment at a median of 18 (13-20) and 16 days (11-20), respectively. One patient developed grade II acute GVHD, and two patients developed limited chronic GVHD. One patient experienced secondary GF requiring a second transplant. At a median follow-up of 69 months (7-110), all patients are alive and thalassemia free. Our data emphasize the need for extended family HLA typing for patients with thalassemia major in regions where there is high rate of consanguinity. Transplant from non-sibling matched family donor can result in excellent outcome.

Amelioration of murine sickle cell disease by nonablative conditioning and γ-globin gene-corrected bone marrow cells

Patients with severe sickle cell disease (SCD) are candidates for gene therapy using autologous hematopoietic stem cells (HSCs), but concomitant multi-organ disease may contraindicate pretransplant conditioning with full myeloablation. We tested whether nonmyeloablative conditioning, a regimen used successfully for allogeneic bone marrow transplantation of adult SCD patients, allows engraftment of γ-globin gene-corrected cells to a therapeutic level in the Berkeley mouse model of SCD. Animals transplanted according to this regimen averaged 35% engraftment of transduced hematopoietic stem cells with an average vector copy < 2.0. Fetal hemoglobin (HbF) levels ranged from 20 to 44% of total hemoglobin and approximately two-thirds of circulating red blood cells expressed HbF detected by immunofluorescence (F-cells). Gene therapy treatment of SCD mice ameliorated anemia, reduced hyperleukocytosis, improved renal function, and reduced iron accumulation in liver, spleen, and kidneys. Thus, modest levels of chimerism with donor cells expressing high levels of HbF from an insulated γ-globin lentiviral vector can improve the pathology of SCD in mice, thereby illustrating a potentially safe and effective strategy for gene therapy in humans.

The Effect of Structural Violence on Patients with Sickle Cell Disease

Sickle Cell Disease (SCD) is a burdensome and prevalent condition predominantly seen in populations of African heritage. Treatments for SCD, particularly those related to pain crisis, are largely insufficient. We argue that it is through structural violence-a systemic series of policies, institutions, and practices-that individuals who live with SCD suffer from health disparities. Similarly, we argue against other suggested mechanisms and causes, such as purely economic factors or low public interest and knowledge. We shall do this in part by comparing the systemic response to SCD to that of Cystic Fibrosis (CF), another genetic based illness with similar prevalence. Notably, CF that affects a very different target population, and has very different research, funding, and treatment trajectories. Underlying these arguments is the hypothesis that structural violence can harm a population in a developed nation just as it can in a developing one.

Reproductive issues in sickle cell disease

As medical advances improve survival, reduce disease-related morbidity, and improve quality of life, reproductive issues will take higher priority in the sickle cell disease (SCD) community. A wide variety of topics are addressed in this chapter, including fertility, gonadal failure, erectile dysfunction, and menstrual issues in SCD. Etiologies of impaired male fertility are multifactorial and include hypogonadism, erectile dysfunction, sperm abnormalities, and complications of medical therapies. Much less is known about the prevalence and etiology of infertility in women with SCD. Other reproductive issues in women included in this review are pain and the menstrual cycle, contraception, and preconception counseling. Finally, long-term therapies for SCD and their impact on fertility are presented. Transfusional iron overload and gonadal failure are addressed, followed by options for fertility preservation after stem cell transplantation. Focus is placed on hydroxyurea therapy given its benefits and increasing use in SCD. The impact of this agent on spermatogenesis, azoospermia, and the developing fetus is discussed.

Health-related quality of life after allogeneic hematopoietic stem cell transplantation for sickle cell disease

Sickle cell disease (SCD) is a hereditary hemoglobinopathy that affects over 100,000 people in the United States. Patients with SCD are known to experience suboptimal health-related quality of life (HRQoL). In addition to the physical manifestations of SCD, psychological and social stress, along with academic difficulties, secondary to the chronicity of the disease and its complications often affect patients with SCD. Although medical therapy of SCD has improved, allogeneic hematopoietic cell transplantation (allo-HCT) remains the only curative therapy. The objective of this study was to measure HRQoL before and after allo-HCT by assessing physical, psychological, and social functioning in patients with SCD who have undergone reduced-toxicity conditioning (busulfan/fludarabine/alemtuzumab) followed by allo-HCT. Patients < 21 years of age undergoing allo-HCT (matched siblings and unrelated donors) for SCD and their primary caregiver were enrolled using either the English or Spanish version of the PedsQoL 4.0. Data were collected at 3 time points: before allo-HCT and on days 180 and 365 after allo-HCT. The change in HRQoL from baseline was assessed with unadjusted and adjusted mixed-effects models in which subjects were treated as random effects, and variance component structure was used. Seventeen patients and 23 primary caregivers were enrolled and reported a mean overall HRQoL of 66.05 (SD, 15.62) and 72.20 (SD, 15.50) at baseline, respectively. In the patient-reported analysis with adjusted mixed-effects models, the estimated improvements in overall HRQoL were 4.45 (SE, 4.98; P = .380) and 16.58 (SE, 5.06; P = .003) at 180 and 365 days, respectively, after allo-HCT. For parent-reported overall HRQoL, the estimated improvements were 1.57 (SE, 4.82; P = .747) and 9.28 (SE, 4.62; P = .053) at 180 and 365 days, respectively, after allo-HCT. Similar results were found across the physical, social, and emotional HRQoL domains with mixed-effects models after adjustment of demographic and medical variables. In addition to the alleviation of clinical manifestations of SCD, these patients demonstrated significant improvement in most aspects of HRQoL by 1 year after allo-HCT. These data represent the trajectory of HRQoL during the initial year of follow-up within this population and should be integrated into the decision-making process when considering allo-HCT in patients with SCD.

Advances in sickle cell therapies in the hydroxyurea era

In the hydroxyurea era, insights into mechanisms downstream of erythrocyte sickling have led to new therapeutic approaches for patients with sickle cell disease (SCD). Therapies have been developed that target vascular adhesion, inflammation and hemolysis, including innovative biologics directed against P-selectin and invariant natural killer T cells. Advances in hematopoietic stem cell transplant and gene therapy may also provide more opportunities for cures in the near future. Several clinical studies are underway to determine the safety and efficacy of these new treatments. Novel approaches to treat SCD are desperately needed, since current therapies are limited and rates of morbidity and mortality remain high.

Reproductive issues in sickle cell disease

As medical advances improve survival, reduce disease-related morbidity, and improve quality of life, reproductive issues will take higher priority in the sickle cell disease (SCD) community. A wide variety of topics are addressed in this chapter, including fertility, gonadal failure, erectile dysfunction, and menstrual issues in SCD. Etiologies of impaired male fertility are multifactorial and include hypogonadism, erectile dysfunction, sperm abnormalities, and complications of medical therapies. Much less is known about the prevalence and etiology of infertility in women with SCD. Other reproductive issues in women included in this review are pain and the menstrual cycle, contraception, and preconception counseling. Finally, long-term therapies for SCD and their impact on fertility are presented. Transfusional iron overload and gonadal failure are addressed, followed by options for fertility preservation after stem cell transplantation. Focus is placed on hydroxyurea therapy given its benefits and increasing use in SCD. The impact of this agent on spermatogenesis, azoospermia, and the developing fetus is discussed.

Natural Remedies for the Treatment of Beta-Thalassemia and Sickle Cell Anemia-Current Status and Perspectives in Fetal Hemoglobin Reactivation

For the treatment of β-thalassemia and sickle cell disease (SCD), pharmacological induction of fetal hemoglobin (HbF) production may be a promising approach. To date, numerous studies have been done on identifying the novel HbF-inducing agents and understanding the underlying mechanism for stimulating the HbF production. In this review, we have summarized the identified HbF-inducing agents by far. By examining the action mechanisms of the HbF-inducing agents, various studies have suggested that despite the ability of stimulating HbF production, the chemotherapeutic agents could not be practically applied for treating β-hemoglobinopathies, especially β-thalassemia, due to the their cytotoxicity and growth-inhibitory effect. Owing to this therapeutic obstacle, much effort has been put on identifying new HbF-inducing agents from the natural world with the combination of efficacy, safety, and ease of use. Therefore, this review aims to (i) reveal the novel screening platforms for identifying potential inducers with high efficiency and accuracy and to (ii) summarize the new identified natural remedies for stimulating HbF production. Hopefully, this review can provide a new insight into the current status and future perspectives in fetal hemoglobin reactivation for treating β-thalassaemia and SCD.

Pediatric hematology providers on referral for transplant evaluation for sickle cell disease: a regional perspective

Hematology referral for evaluation is a key step for hematopoietic stem cell transplantation for sickle cell disease (SCD). Pediatric SCD providers in the US Northeast (New York-Mid-Atlantic and New England regions) were surveyed anonymously for perspectives and practices regarding transplant referral and compared by whether they practiced at SCD transplant centers. Data were analyzed using the Fisher exact test, χ test, and logistic regression. Half of the respondents practiced primarily at transplant sites. Most (79%) were enthusiastic about transplant for SCD and 78% had recently referred ≥1 child for evaluation. Overall, 77% limited referral to certain sickle hemoglobinopathies and 44% preferred referral for β-thalassemia to SCD. Indications selected for referral resembled current transplant criteria, plus family request or poor response to therapy. Referral for children on chronic transfusions predicted enthusiasm and prior referral. Many (66%) referred children with multiple SCD complications, even without matched sibling donors, 37% with sibling donors despite limited disease. Practitioners at transplant centers more commonly accepted event-free survival rates of ≤90% (P=0.002). Northeastern providers expressed varying enthusiasm for referral for evaluation based on eligibility, donor availability, and acceptable risk, with modestly more interest from practitioners at transplant centers. Differing provider perspectives may affect patient referral for transplant consideration.

Themes reported by families as important when proceeding with pediatric hematopoietic stem cell transplantation

BACKGROUND

Hematopoietic stem cell transplantation (HSCT) is an accepted treatment for pediatric malignant and non-malignant conditions. Agreeing to HSCT can be challenging for families. This study explored themes reported by family members as influencing their acceptance of HSCT as a necessary treatment intervention.

PROCEDURE

In a four-site study, 107 individuals within 30 families pursuing HSCT for a pediatric malignancy, and 25 individuals within 6 families pursuing HSCT for a pediatric non-malignancy were interviewed pre-HSCT. Semantic content analysis was used in this secondary analysis to identify relevant themes.

RESULTS

Fifty-eight parents (and surrogates) 19 patients, 16 donor siblings, and 39 non-donor siblings, half-siblings and cousins, participated. Thirteen themes were identified as influencing the acceptance of HSCT. The most frequently reported were: "recommendation by the child's physician," viewing HSCT as the "best chance for cure," and "desiring a more normal and better quality of life for the patient and family." Seven themes were reported by all categories of family members, though at different frequencies. Two themes ("HSCT being part of the upfront treatment plan": "hearing of HSCT success in others") were only reported by the malignancy group, and one theme ("worrying about disease progression and losing a window of HSCT opportunity") was only reported by the non-malignancy group.

CONCLUSION

Parents, patients, and other family members can articulate multiple themes that influence their considerations of HSCT. Understanding these themes may guide discussions between families and healthcare teams.

Outcome of invasive mechanical ventilation after pediatric allogeneic hematopoietic SCT: results from a prospective, multicenter registry

Exact data on prognosis of children receiving invasive mechanical ventilation (IMV) after allogeneic hematopoietic SCT (HSCT) is lacking. We therefore started a prospective registry in four European university HSCT centers (Leiden, Paris, Prague and Utrecht) and their pediatric intensive care units (PICUs). The registry started in January 2009. In January 2013, the four centers together had treated a total of 83 admissions with IMV. The case fatality rate in these patients was 52%. Mortality 6 months after PICU discharge was 45%. There were significant differences between centers in the proportion of children who received IMV after HSCT (6-23%, P<0.01), in severity of disease on admission to PICU (predicted mortality 14-37%, P<0.01), in applying noninvasive ventilation before IMV (3-75% of admissions, P<0.01) and in the use of renal replacement therapy (RRT) (8-58% of admissions, P<0.01). Severe impairment in oxygenation, use of RRT and CMV viremia were independent predictors of mortality. Our study shows that mortality in children receiving IMV after HSCT remains high, but has clearly improved compared with older studies. Patient selection and treatment in PICU differed significantly between centers, which underscores the need to standardize and optimize the PICU admission criteria, ventilatory strategies and therapies applied in PICU.

Reduced toxicity, myeloablative conditioning with BU, fludarabine, alemtuzumab and SCT from sibling donors in children with sickle cell disease

BU and CY (BU/CY; 200 mg/kg) before HLA-matched sibling allo-SCT in children with sickle cell disease (SCD) is associated with ~85% EFS but is limited by the acute and late effects of BU/CY myeloablative conditioning. Alternatives include reduced toxicity but more immunosuppressive conditioning. We investigated in a prospective single institutional study, the safety and efficacy of a reduced-toxicity conditioning (RTC) regimen of BU 12.8-16 mg/kg, fludarabine 180 mg/m(2), alemtuzumab 54 mg/m(2) (BFA) before HLA-matched sibling donor transplantation in pediatric recipients with symptomatic SCD. Eighteen patients, median age 8.9 years (2.3-20.2), M/F 15/3, 15 sibling BM and 3 sibling cord blood (CB) were transplanted. Mean whole blood and erythroid donor chimerism was 91% and 88%, at days +100 and +365, respectively. Probability of grade II-IV acute GVHD was 17%. Two-year EFS and OS were both 100%. Neurological, pulmonary and cardiovascular function were stable or improved at 2 years. BFA RTC and HLA-matched sibling BM and CB allo-SCT in pediatric recipients result in excellent EFS, long-term donor chimerism, low incidence of GVHD and stable/improved organ function.

Conditioning regimens in allo-SCT for thalassemia major

Allogeneic hematopoietic SCT remains the only treatment that can correct the hematological manifestations in patients with thalassemia major. Improving the clinical outcomes of high-risk, heavily transfused patients with liver fibrosis and inadequate iron chelation remains a challenge. Because of the relatively high probability of graft rejection and regimen-related toxicity in many patients receiving SCT for advanced thalassemia major, further development of new treatment regimens is warranted. This review addresses the reported clinical studies in patients with advanced thalassemia major and we have summarized our suggested conditioning approach to improve the outcome after SCT.

Haematopoietic stem cell transplantation for severe sickle cell disease in childhood: a single centre experience of 50 patients

Despite improvements in medical management, sickle cell disease (SCD) remains associated with severe morbidity and decreased survival. Allogeneic haematopoietic stem cell transplantation (HSCT) remains the only curative approach. We report the outcome of 50 consecutive children with severe SCD that received HSCT in our unit between November 1988 and April 2013. The stem cell source was bone marrow (n = 39), cord blood (n = 3), bone marrow and cord blood (n = 7) and peripheral blood stem cells (n = 1). All patients had ≥1 severe manifestation: 37 presented with recurrent vaso-occlusive crises/acute chest syndrome, 27 cerebral vasculopathy and 1 nephropathy. The conditioning regimen consisted of busulfan + cyclophosphamide (BuCy) before November 1991 and BuCy + rabbit antithymocyte globulin after that date. Since 1995, all patients have been treated with hydroxycarbamide (HC) prior to transplantation for a median duration of 2·7 years. Median age at transplantation and median follow-up was 8·3 and 7·7 years, respectively. Acute graft-versus-host disease (GVHD) and chronic GVHD were observed in 11 and 10 patients, respectively. An excellent outcome was achieved, with 8-year overall survival and event-free survival (EFS) rates of 94·1% and 85·6%, respectively. Since HC introduction, no graft failure occurred and EFS reached 97·4%. Prior treatment with HC may have contributed to successful engraftment.

Transfusion-induced bone marrow transplant rejection due to minor histocompatibility antigens

Traditionally, alloimmunization to transfused blood products has focused exclusively on recipient antibodies recognizing donor alloantigens present on the cell surface. Accordingly, the immunologic sequelae of alloimmunization have been antibody mediated effects (ie, hemolytic transfusion reactions, platelet refractoriness, anti-HLA and anti-HNA effects, etc). However, in addition to the above sequelae, there is also a correlation between the number of antecedent transfusions in humans and the rate of bone marrow transplant (BMT) rejection-under reduced intensity conditioning with HLA-matched or HLA-identical marrow. Bone marrow transplant of this nature is the only existing cure for a series of nonmalignant hematologic diseases (eg, sickle cell disease, thalassemias, etc); however, rejection remains a clinical problem. It has been hypothesized that transfusion induces subsequent BMT rejection through immunization. Studies in animal models have observed the same effect and have demonstrated that transfusion-induced BMT rejection can occur in response to alloimmunization. However, unlike traditional antibody responses, sensitization in this case results in cellular immune effects, involving populations such as T cell or natural killer cells. In this case, rejection occurs in the absence of alloantibodies and would not be detected by existing immune-hematologic methods. We review human and animal studies in light of the hypothesis that, for distinct clinical populations, enhanced rejection of BMT may be an unappreciated adverse consequence of transfusion, which current blood bank methodologies are unable to detect.

Novel dominant β-thalassemia: Hb Boston-Kuwait [codon 139/140(+T)]

Dominant β-thalassemias exhibit a hybrid phenotype of unstable hemoglobin and ineffective erythropoiesis. Most arise from heterozygous β-globin gene mutations in exons 3 or 2 and present in adulthood as thalassemia intermedia. We report a novel, de novo β-globin mutation presenting in a toddler with features of thalassemia major and chromaturia. Hemoglobin Boston-Kuwait is an elongated β-chain variant (163 amino acids) that results from a frameshift mutation caused by a thymidine insertion in codons 139/140. Hematopoietic stem cell transplant provided a successful alternative therapy for this severe form of dominant β-thalassemia.

Fertility preservation in patients with haematological disorders: a retrospective cohort study

This study investigated the factors associated with utilization of fertility preservation and the differences in treatments and outcomes by prior chemotherapy exposure in patients with haematological diseases. This study included all 67 women with haematological diseases seen for fertility preservation consultation at two university hospitals between 2006 and 2011. Of the total, 49% had lymphoma, 33% had leukaemia, 7% had myelodysplastic syndrome and 4% had aplastic anaemia; 46% had prior chemotherapy; and 33% were planning for bone marrow transplantation, 33% pursued ovarian stimulation and 7% used ovarian tissue banking; and 48% of patients did not pursue fertility preservation treatment. All five cycle cancellations were in the post-chemotherapy group: three patients with leukaemia and two with lymphoma. Patients with prior chemotherapy had lower baseline antral follicle count (10 versus 22) and received more gonadotrophins to achieve similar peak oestradiol concentrations, with no difference in oocyte yield (10.5 versus 10) after adjustment for age. Embryo yield was similar between those who had prior chemotherapy and those who had not. Half of the patients with haematological diseases who present for fertility preservation have been exposed to chemotherapy. While ovarian reserve is likely impaired in this group, oocyte yield may be acceptable.

Risk adopted allogeneic hematopoietic stem cell transplantation using a reduced intensity regimen for children with thalassemia major

BACKGROUND

Patients with thalassemia in developing countries have limited access to safe transfusions, regular medical care and chelation therapy. Although allogeneic hematopoietic stem cell transplantation (HSCT) can offer a curative approach, there are limited data on the use of this procedure in developing countries.

PROCEDURE

Forty-four patients underwent a risk adopted HSCT from matched related family donor in Jordan. Thirty-one patients (7 Class 1 and 24 Class 2) underwent myeloablative conditioning (MAC) with busulfan (16 mg/kg), cyclophosphamide (200 mg/kg) and antithymocyte globulin (ATG). Thirteen patients all with Class 3, seven with hepatitis C received reduced intensity conditioning (RIC) with busulfan (8 mg/kg), fludarabine (175 mg/m(2)), total lymphoid irradiation (500 cGy) and ATG.

RESULTS

All patients had initial neutrophil and platelet engraftment. Secondary graft failure was observed in 2 (6%) patients receiving myeloablative HSCT and 3 (23%) patients receiving RIC. At a median follow up of 64 months (13-108), 43 of 44 patients are alive. The 5-year probability of overall survival (OS) was 97.8% for all patients, 96.8% for patients received MAC and 100% for patients received RIC. The 5-year probability of thalassemia-free survival was 86.4% for all patients, 90.3% and 77% for patients who received MAC and RIC, respectively.

CONCLUSION

Implementing a risk-adopted therapy in patient with thalassemia in Jordan can result in an excellent thalassemia free and OS, especially in those at highest risk.

Stem cell transplantation for treatment of sickle cell disease: bone marrow versus cord blood transplants

PURPOSE

The transplantation of stem cells harvested from bone marrow and cord blood for the treatment of sickle cell disease (SCD) is reviewed.

SUMMARY

Current treatment options have lengthened the lifespan of patients with SCD. Hydroxyurea is the standard of care for the management of SCD, but it does not prevent serious complications in all patients. For those patients with severe disease, stem cell transplantation may be an appropriate curative option. However, less than one third of these patients find an appropriate matched related bone marrow donor. Cord blood offers a more readily available source of stem cells for transplantation. Donor morbidity is eliminated, since the cells come from banked cords, and the harvesting process is noninvasive for the donor. Another advantage of cord blood transplantation is the lower occurrence of graft-versus-host disease (GVHD). One disadvantage of transplantation with cord blood includes delayed time to engraftment. Due to the mortality associated with stem cell transplantation, it may be most appropriate to reserve the procedure for patients who have a more severe course of SCD.

CONCLUSION

Although bone marrow, peripheral blood, and cord blood transplantation has been successfully performed in patients with SCD, data remain limited regarding the optimal preparative regimens, the most appropriate stem cell source, and the type of GVHD prophylaxis to be used after transplantation. More data are warranted before this treatment approach can be recommended as a standard of care for SCD.

FK228 Analogues Induce Fetal Hemoglobin in Human Erythroid Progenitors

Fetal hemoglobin (HbF) improves the clinical severity of sickle cell disease (SCD), therefore, research to identify HbF-inducing agents for treatment purposes is desirable. The focus of our study is to investigate the ability of FK228 analogues to induce HbF using a novel KU812 dual-luciferase reporter system. Molecular modeling studies showed that the structure of twenty FK228 analogues with isosteric substitutions did not disturb the global structure of the molecule. Using the dual-luciferase system, a subgroup of FK228 analogues was shown to be inducers of HbF at nanomolar concentrations. To determine the physiological relevance of these compounds, studies in primary erythroid progenitors confirmed that JMA26 and JMA33 activated HbF synthesis at levels comparable to FK228 with low cellular toxicity. These data support our lead compounds as potential therapeutic agents for further development in the treatment of SCD.

Mechanisms of alloimmunization and subsequent bone marrow transplantation rejection induced by platelet transfusion in a murine model

For many nonmalignant hematological disorders, HLA-matched bone marrow transplantation (BMT) is curative. However, due to lack of neoplasia, the toxicity of stringent conditioning regimens is difficult to justify, and reduced intensity conditioning is used. Unfortunately, current reduced intensity regimens have high rates of BMT rejection. We have recently reported in a murine model that mHAs on transfused platelet products induce subsequent BMT rejection. Most nonmalignant hematological disorders require transfusion support prior to BMT and the rate of BMT rejection in humans correlates with the number of transfusions given. Herein, we perform a mechanistic analysis of platelet transfusion-induced BMT rejection and report that unlike exposure to alloantigens during transplantation, platelet transfusion primes alloimmunity but does not stimulate full effector function. Subsequent BMT is itself an additional and distinct immunizing event, which does not induce rejection without antecedent priming from transfusion. Both CD4(+) and CD8(+) T cells are required for priming during platelet transfusion, but only CD8(+) T cells are required for BMT rejection. In neither case are antibodies required for rejection to occur.