Stem Cell Therapy for Sickle Cell Disease: Transplantation and Gene Therapy

Extracorporeal photopheresis versus standard treatment for acute graft-versus-host disease after haematopoietic stem cell transplantation in children and adolescents

BACKGROUND

Acute graft-versus-host disease (aGvHD) is a major cause of morbidity and mortality after haematopoietic stem cell transplantation (HSCT), occurring in 8% to 85% of paediatric recipients. Currently, the therapeutic mainstay for aGvHD is treatment with corticosteroids. However, there is no established standard treatment for steroid-refractory aGvHD. Extracorporeal photopheresis (ECP) is a type of immunomodulatory method amongst different therapeutic options that involves ex vivo collection of peripheral mononuclear cells, exposure to the photoactive agent 8-methoxypsoralen and ultraviolet-A radiation, and reinfusion of these treated blood cells to the patient. The mechanisms of action of ECP are not completely understood. This is the second update of a Cochrane Review first published in 2014 and updated in 2015.

OBJECTIVES

To evaluate the effectiveness and safety of ECP for the management of aGvHD in children and adolescents after HSCT.

SEARCH METHODS

We searched the Cochrane Register of Controlled Trials (CENTRAL), MEDLINE (PubMed) and Embase (Ovid) databases from their inception to 25 January 2021. We searched the reference lists of potentially relevant studies without any language restrictions. We searched five conference proceedings and nine clinical trial registries on 9 November 2020 and 12 November 2020, respectively.

SELECTION CRITERIA

We sought to include randomised controlled trials (RCTs) comparing ECP with or without standard treatment versus standard treatment alone in children and adolescents with aGvHD after HSCT.

DATA COLLECTION AND ANALYSIS

Two review authors independently performed the study selection. We resolved disagreement in the selection of trials by consultation with a third review author.

MAIN RESULTS

We identified no additional studies in the 2021 review update, so there are still no studies that meet the criteria for inclusion in this review.

AUTHORS' CONCLUSIONS

The efficacy of ECP in the treatment of aGvHD in children and adolescents after HSCT is unknown, and its use should be restricted to within the context of RCTs. Such studies should address a comparison of ECP alone or in combination with standard treatment versus standard treatment alone. The 2021 review update brought about no additions to these conclusions.

The mRNA-Binding Protein IGF2BP1 Restores Fetal Hemoglobin in Cultured Erythroid Cells from Patients with β-Hemoglobin Disorders

Sickle cell disease (SCD) and β-thalassemia are caused by structural abnormality or inadequate production of adult hemoglobin (HbA, α₂β₂), respectively. Individuals with either disorder are asymptomatic before birth because fetal hemoglobin (HbF, α₂γ₂) is unaffected. Thus, reversal of the switch from HbF to HbA could reduce or even prevent symptoms these disorders. In this study, we show that insulin-like growth factor 2 mRNA-binding protein 1 (IGF2BP1) is one factor that could accomplish this goal. IGF2BP1 is a fetal factor that undergoes a transcriptional switch consistent with the transition from HbF to HbA. Lentivirus delivery of IGF2BP1 to CD34⁺ cells of healthy adult donors reversed hemoglobin production toward the fetal type in culture-differentiated erythroid cells. Analogous studies using patient-derived CD34⁺ cells revealed that IGF2BP1-dependent HbF induction could ameliorate the chain imbalance in β-thalassemia or potently suppress expression of sickle β-globin in SCD. In all cases, fetal γ-globin mRNA increased and adult β-globin decreased due, in part, to formation of contacts between the locus control region (LCR) and γ-globin genes. We conclude that expression of IGF2BP1 in adult erythroid cells has the potential to maximize HbF expression in patients with severe β-hemoglobin disorders by reversing the developmental γ- to β-globin switch.

Genetic treatment of a molecular disorder: gene therapy approaches to sickle cell disease

Effective medical management for sickle cell disease (SCD) remains elusive. As a prevalent and severe monogenic disorder, SCD has been long considered a logical candidate for gene therapy. Significant progress has been made in moving toward this goal. These efforts have provided substantial insight into the natural regulation of the globin genes and illuminated challenges for genetic manipulation of the hematopoietic system. The initial γ-retroviral vectors, next-generation lentiviral vectors, and novel genome engineering and gene regulation approaches each share the goal of preventing erythrocyte sickling. After years of preclinical studies, several clinical trials for SCD gene therapies are now open. This review focuses on progress made toward achieving gene therapy, the current state of the field, consideration of factors that may determine clinical success, and prospects for future development.

Extracorporeal photopheresis versus alternative treatment for chronic graft-versus-host disease after haematopoietic stem cell transplantation in paediatric patients

BACKGROUND

Chronic graft-versus-host disease (GvHD) is a major cause of morbidity and mortality after haematopoietic stem cell transplantation occurring in 6% to 65% of the recipients. Currently, the therapeutic mainstay for chronic GvHD are corticosteroids that are frequently combined with other immunosuppressive agents in people with steroid-refractory manifestations. There is no established standard treatment for steroid-refractory chronic GvHD. The therapeutic options for these patients include extracorporeal photopheresis (ECP), an immunomodulatory treatment that involves ex vivo collection of mononuclear cells from peripheral blood, exposure to the photoactive agent 8-methoxypsoralen, ultraviolet radiation and re-infusion of the processed cell product. The mechanisms of action of ECP are not completely understood. This is an updated version of a Cochrane review first published in 2014.

OBJECTIVES

To evaluate the effectiveness and safety of ECP for the management of chronic GvHD in children and adolescents after haematopoietic stem cell transplantation.

SEARCH METHODS

We searched the Cochrane Register of Controlled Trials (CENTRAL) (Issue 9, 2015), MEDLINE and EMBASE databases from their inception to 23 September 2015. We searched the reference lists of potentially relevant studies without any language restriction. We searched eight trial registers and five conference proceedings on 29 September 2015.

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing ECP with or without alternative treatment versus alternative treatment alone in paediatric patients with chronic GvHD after haematopoietic stem cell transplantation.

DATA COLLECTION AND ANALYSIS

Two review authors independently performed the study selection. We resolved disagreements in the selection of trials by consultation with a third review author.

MAIN RESULTS

No additional studies were identified in this 2015 review update, in total leading to no studies meeting the criteria for inclusion in this review.

AUTHORS' CONCLUSIONS

The efficacy of ECP in the treatment of chronic GvHD in paediatric patients after haematopoietic stem cell transplantation based on RCTs cannot be evaluated since the original version of this review and the first review update found no RCTs. Current recommendations are based on retrospective or observational studies only. Thus, ideally, ECP should be applied in the context of controlled trials only. However, performing RCTs in this patient population will be challenging due to the limited number of patients, the variable disease presentation and the lack of well-defined response criteria. International collaboration, multicentre trials and appropriate funding for such trials will be needed. If treatment decisions based on clinical data are made in favour of ECP, patients should be carefully monitored for beneficial and harmful effects. In addition, efforts should be made to share this information with other clinicians, for example by setting up registries for paediatric patients that are treated with ECP.

Extracorporeal photopheresis versus standard treatment for acute graft-versus-host disease after haematopoietic stem cell transplantation in paediatric patients

BACKGROUND

Acute graft-versus-host disease (aGvHD) is a major cause of morbidity and mortality after haematopoietic stem cell transplantation (HSCT) occurring in 8% to 59% of the recipients. Currently, the therapeutic mainstay for aGvHD is corticosteroids. However, there is no established standard treatment for steroid-refractory aGvHD. Extracorporeal photopheresis (ECP) is a type of immunomodulatory method amongst different therapeutic options that involves ex vivo collection of peripheral mononuclear cells, exposure to the photoactive agent 8-methoxypsoralen and ultraviolet-A radiation, and re-infusion of these treated blood cells to the patient. The mechanisms of action of ECP are not completely understood. This is an updated version of a Cochrane review first published in 2014.

OBJECTIVES

To evaluate the effectiveness and safety of ECP for the management of aGvHD in children and adolescents after HSCT.

SEARCH METHODS

We searched the Cochrane Register of Controlled Trials (CENTRAL) (Issue 9, 2015), MEDLINE (PubMed) and EMBASE (Ovid) databases from their inception to 23 September 2015. We searched the reference lists of potentially relevant studies without any language restrictions. We searched eight trial registers and four conference proceedings on 29 September 2015.

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing ECP with or without standard treatment versus standard treatment alone in paediatric patients with aGvHD after HSCT.

DATA COLLECTION AND ANALYSIS

Two review authors independently performed the study selection. We resolved disagreement in the selection of trials by consultation with a third review author.

MAIN RESULTS

We identified no additional studies in the 2015 review update, in total leading to no studies meeting the criteria for inclusion in this review.

AUTHORS' CONCLUSIONS

The efficacy of ECP in the treatment of aGvHD in paediatric patients after HSCT is unknown and its use should be restricted within the context of RCTs. Such studies should address a comparison of ECP alone or in combination with standard treatment versus standard treatment alone. The 2015 review update brought about no additions to these conclusions.

Potentially therapeutic levels of anti-sickling globin gene expression following lentivirus-mediated gene transfer in sickle cell disease bone marrow CD34+ cells

Sickle cell disease (SCD) can be cured by allogeneic hematopoietic stem cell transplant. However, this is only possible when a matched donor is available, making the development of gene therapy using autologous hematopoietic stem cells a highly desirable alternative. We used a culture model of human erythropoiesis to directly compare two insulated, self-inactivating, and erythroid-specific lentiviral vectors, encoding for γ-globin (V5m3-400) or a modified β-globin (βAS3-FB) for production of antisickling hemoglobin (Hb) and correction of red cell deformability after deoxygenation. Bone marrow CD34+ cells from three SCD patients were transduced using V5m3-400 or βAS3-FB and compared with mock-transduced SCD or healthy donor CD34+ cells. Lentiviral transduction did not impair cell growth or differentiation, as gauged by proliferation and acquisition of erythroid markers. Vector copy number averaged approximately one copy per cell, and corrective globin mRNA levels were increased more than sevenfold over mock-transduced controls. Erythroblasts derived from healthy donor and mock-transduced SCD cells produced a low level of fetal Hb that was increased to 23.6 ± 4.1% per vector copy for cells transduced with V5m3-400. Equivalent levels of modified normal adult Hb of 17.6 ± 3.8% per vector copy were detected for SCD cells transduced with βAS3-FB. These levels of antisickling Hb production were sufficient to reduce sickling of terminal-stage red blood cells upon deoxygenation. We concluded that the achieved levels of fetal Hb and modified normal adult Hb would likely prove therapeutic to SCD patients who lack matched donors.

Management of sickle cell disease: a review for physician education in Nigeria (sub-saharan Africa)

Sickle cell disease (SCD) predominates in sub-Saharan Africa, East Mediterranean areas, Middle East, and India. Nigeria, being the most populous black nation in the world, bears its greatest burden in sub-Saharan Africa. The last few decades have witnessed remarkable scientific progress in the understanding of the complex pathophysiology of the disease. Improved clinical insights have heralded development and establishment of disease modifying interventions such as chronic blood transfusions, hydroxyurea therapy, and haemopoietic stem cell transplantation. Coupled with parallel improvements in general supportive, symptomatic, and preventive measures, current evidence reveals remarkable appreciation in quality of life among affected individuals in developed nations. Currently, in Nigeria and other West African states, treatment and control of SCD are largely suboptimal. Improved knowledge regarding SCD phenotypes and its comprehensive care among Nigerian physicians will enhance quality of care for affected persons. This paper therefore provides a review on the aetiopathogenesis, clinical manifestations, and management of SCD in Nigeria, with a focus on its local patterns and peculiarities. Established treatment guidelines as appropriate in the Nigerian setting are proffered, as well as recommendations for improving care of affected persons.

Extracorporeal photopheresis versus alternative treatment for chronic graft-versus-host disease after haematopoietic stem cell transplantation in paediatric patients

BACKGROUND

Chronic graft-versus-host disease (GvHD) is a major cause of morbidity and mortality after haematopoietic stem cell transplantation occurring in 6% to 65% of the recipients. Currently, the therapeutic mainstay for chronic GvHD are corticosteroids that are frequently combined with other immunosuppressive agents in people with steroid-refractory manifestations. There is no established standard treatment for steroid-refractory chronic GvHD. The therapeutic options in these people include extracorporeal photopheresis (ECP), an immunomodulatory treatment that involves ex vivo collection of mononuclear cells from peripheral blood, exposure to the photoactive agent 8-methoxypsoralen, ultraviolet radiation and re-infusion of the processed cell product. The mechanisms of action of ECP are not completely understood.

OBJECTIVES

To evaluate the effectiveness and safety of ECP for the management of chronic GvHD in children and adolescents after haematopoietic stem cell transplantation.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (Issue 9, 2012), MEDLINE and EMBASE databases from their inception to 12 September 2012. We searched the reference lists of potentially relevant studies without any language restriction. We searched eight trial registers and five conference proceedings. We also contacted experts in the field.

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing ECP with or without alternative treatment versus alternative treatment alone in paediatric patients with chronic GvHD after haematopoietic stem cell transplantation.

DATA COLLECTION AND ANALYSIS

Two review authors independently performed the study selection. We resolved disagreements in the selection of trials by consultation with a third review author.

MAIN RESULTS

We found no studies meeting the criteria for inclusion in this review.

AUTHORS' CONCLUSIONS

The efficacy of ECP in the treatment of chronic GvHD in paediatric patients after haematopoietic stem cell transplantation based on RCTs can currently not be evaluated since we have found no such studies. Current recommendations are based on retrospective or observational studies only. Thus, ideally, ECP should be applied in the context of controlled trials only. However, performing RCTs in this patient population will be challenging due to the limited number of patients, the variable disease presentation and the lack of well-defined response criteria. International collaboration, multicentre trials and appropriate funding for such trials will be needed. If treatment decisions based on clinical grounds in favour of ECP are made, people should be carefully monitored for beneficial and harmful effects and efforts should be made to share this information with other clinicians, for example by setting up registries for paediatric patients that are treated with ECP.

Extracorporeal photopheresis versus standard treatment for acute graft-versus-host disease after haematopoietic stem cell transplantation in paediatric patients

BACKGROUND

Acute graft-versus host disease (aGvHD) is a major cause of morbidity and mortality after haematopoietic stem cell transplantation (HSCT) occurring in 8% to 59% of the recipients. Currently, the therapeutic mainstay for aGvHD is corticosteroids. However, there is no established standard treatment for steroid-refractory aGvHD. Extracorporeal photopheresis (ECP) is a type of immunomodulatory method amongst different therapeutic options that involves ex vivo collection of peripheral mononuclear cells, exposure to the photoactive agent 8-methoxypsoralen and ultraviolet-A radiation, and re-infusion of these treated blood cells to the patient. The mechanisms of action of ECP are not completely understood

OBJECTIVES

To evaluate the effectiveness and safety of ECP for the management of aGvHD in children and adolescents after HSCT.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (Issue 9, 2012), MEDLINE/PubMed and EMBASE (Ovid) databases from their inception to 12 September 2012. We searched the reference lists of potentially relevant studies without any language restriction. We searched eight trial registers and four conference proceedings. We also contacted an expert in the field to request information on unpublished study that involves ECP in aGvHD after HSCT.

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing ECP with or without standard treatment versus standard treatment alone in paediatric patients with aGvHD after HSCT.

DATA COLLECTION AND ANALYSIS

Two review authors independently performed the study selection. We resolved disagreement in the selection of trials by consultation with a third review author.

MAIN RESULTS

We found no studies meeting the criteria for inclusion in this review.

AUTHORS' CONCLUSIONS

The efficacy of ECP in the treatment of aGvHD in paediatric patients after HSCT is unknown and its use should be restricted within the context of RCTs. Such studies should address a comparison of ECP alone or in combination with standard treatment versus standard treatment alone. 

Sickle cell disease: management options and challenges in developing countries

Sickle Cell Disease (SCD) is the most common genetic disorder of haemoglobin in sub-Saharan Africa. This commentary focuses on the management options available and the challenges that health care professionals in developing countries face in caring for patients with SCD. In a developing countries like Ghana, new-born screening is now about to be implemented on a national scale. Common and important morbidities associated with SCD are vaso-occlusive episodes, infections, Acute Chest Syndrome (ACS), Stroke and hip necrosis. Approaches to the management of these morbidities are far advanced in the developed countries. The differences in setting and resource limitations in developing countries bring challenges that have a major influence in management options in developing countries. Obviously clinicians in developing countries face challenges in managing SCD patients. However understanding the disease, its progression, and instituting the appropriate preventive methods are paramount in its management. Emphasis should be placed on early counselling, new-born screening, anti-microbial prophylaxis, vaccination against infections, and training of healthcare workers, patients and caregivers. These interventions are affordable in developing countries.

Chronic graft-versus-host disease (GVHD) in children

Five-year survival rates for childhood cancer now exceed 80% and with the significant progress made by the transplant community in developing less toxic conditioning regimens and in the treatment of posttransplant complications, allo-hematopoietic stem cell transplantation (HSCT) contributes significantly to that population of long-term survivors. In this context, the acute and long-term toxicities of chronic graft-versus-host disease (cGVHD) have an ever-increasing effect on organ function, quality of life, and survival; patients and families who initially felt great relief to be cured from the primary disease, now face the challenge of a chronic debilitating illness for which preventative and treatment strategies are suboptimal. Hence, the development of novel strategies that reduce and or control cGVHD, preserve graft-versus-tumor effects, facilitate engraftment and immune reconstitution, and enhance survival after allo-HSCT represents one of the most significant challenges facing physician-scientists and patients.

Preliminary in vitro antisickilng properties of crude juice extracts of Persia Americana, Citrus sinensis, Carica papaya and Ciklavit®

The antisickling properties of crude juice extracts of the edible portions of three commonly consumed tropical fruits namely Persia americana, Citrus sinensis, and Carica papaya were investigated in vitro alongside a new drug preparation called Ciklavit® that has antisickling activity. Four different solvent extracts of the crude juice of each fruit including aqueous, acidic, alkaline and alcoholic extracts were prepared and their antisickling effects on sickle cell trait (HbAS) and sickle cell disease (HbSS) blood samples checked alongside Ciklavit®. Blood samples were stabilized using normal saline and the antisickling effects were checked by counting the number of sickle cells remaining after incubation of the blood samples with the crude fruit extracts and Ciklavit® for twenty-four hours. The results showed that Ciklavit® produced a sustained reduction in the number of sickle cells in both HbAS and HbSS blood samples. Also the alkaline and alcoholic extracts of P. americana and C. papaya produced significant reduction in the number of sickle cells.

Stem Cell Transplantation in Hemoglobinopathies

beta-Thalassemia (thal) and sickle cell disease are the most common genetic diseases worldwide. Although supportive therapies such as regular transfusion and chelation for beta-thal and hydroxyurea (HU) for sickle cell disease have significantly improved clinical manifestations and the quality of life, they cannot eliminate disease and therapy-related complications. Today, hematopoietic stem cell transplantation (HSCT) is the only curative treatment for patients with hemoglobinopathies. The first successful HSCT was reported in 1981. At that time, more than 1,000 patients underwent HSCT in Pesaro, Italy. Sixty beta-thal patients underwent HSCT at the Department of Pediatric Hematology-Oncology, Akdeniz University School of Medicine, Antalya, Turkey between 1998 and 2006. We found stable mixed chimerism in 14 patients out of 45 (31%) in our transplanted thalassemia patients. The thalassemia free survival and overall survival rates were found to be 84.0 and 91.0%, respectively. The literature and our results indicate that HSCT can offer a cure for hemoglobinopathy patients.

Correction of murine sickle cell disease using gamma-globin lentiviral vectors to mediate high-level expression of fetal hemoglobin

Increased levels of red cell fetal hemogloblin, whether due to hereditary persistence of expression or from induction with hydroxyurea therapy, effectively ameliorate sickle cell disease (SCD). Therefore, we developed erythroid-specific, gamma-globin lentiviral vectors for hematopoietic stem cell (HSC)-targeted gene therapy with the goal of permanently increasing fetal hemoglobin (HbF) production in sickle red cells. We evaluated two different gamma-globin lentiviral vectors for therapeutic efficacy in the BERK sickle cell mouse model. The first vector, V5, contained the gamma-globin gene driven by 3.1 kb of beta-globin regulatory sequences and a 130-bp beta-globin promoter. The second vector, V5m3, was identical except that the gamma-globin 3'-untranslated region (3'-UTR) was replaced with the beta-globin 3'-UTR. Adult erythroid cells have beta-globin mRNA 3'-UTR-binding proteins that enhance beta-globin mRNA stability and we postulated this design might enhance gamma-globin expression. Stem cell gene transfer was efficient and nearly all red cells in transplanted mice expressed human gamma-globin. Both vectors demonstrated efficacy in disease correction, with the V5m3 vector producing a higher level of gamma-globin mRNA which was associated with high-level correction of anemia and secondary organ pathology. These data support the rationale for a gene therapy approach to SCD by permanently enhancing HbF using a gamma-globin lentiviral vector.

Hematopoietic stem cell gene transfer for the treatment of hemoglobin disorders

Hematopoietic stem cell (HSC)-targeted gene transfer is an attractive approach for the treatment of a number of hematopoietic disorders caused by single gene defects. Indeed, in a series of gene transfer trials for two different primary immunodeficiencies beginning early in this decade, outstanding success has been achieved. Despite generally low levels of engrafted, genetically modified HSCs, these trials were successful because of the marked selective advantage of gene-corrected lymphoid precursors that allowed reconstitution of the immune system. Unlike the immunodeficiencies, this robust level of in vivo selection is not available to hematopoietic repopulating cells or early progenitor cells following gene transfer of a therapeutic globin gene in the setting of beta-thalassemia and sickle cell disease. Both preclinical and clinical transplant studies involving bone marrow chimeras suggest that 20% or higher levels of engraftment of genetically modified HSCs will be needed for clinical success in the most severe of these disorders. Encouragingly, gene transfer levels in this range have recently been reported in a lentiviral vector gene transfer clinical trial for children with adrenoleukodystrophy. A clinical gene transfer trial for beta-thalassemia has begun in France, and one patient with transfusion-dependent HbE/beta-thalassemia has demonstrated a therapeutic effect after transplantation with autologous CD34(+) cells genetically modified with a beta-globin lentiviral vector. Here, the development and recent progress of gene therapy for the hemoglobin disorders is reviewed.

Stable long-term donor engraftment following reduced-intensity hematopoietic cell transplantation for sickle cell disease

Reduced-intensity conditioning (RIC) regimens have the potential to decrease toxicities related to hematopoietic stem cell transplantation (HCT) in patients with sickle cell disease (SCD) and thus make HCT a more acceptable therapeutic option for this group of patients. We report the results of 7 patients enrolled on a study to evaluate safety and efficacy of HCT using bone marrow from an HLA matched sibling donor following an RIC regimen for patients with high-risk SCD. The conditioning regimen consisted of busulfan, fludarabine, equine antithymocyte globulin, and total lymphoid irradiation with shielding of the liver, lungs, heart, and gonads on day 1. Graft-versus-host disease (GVHD) prophylaxis consisted of cyclosporine and mycophenolate mofetil. The regimen was well tolerated, and all patients had hematopoietic recovery. Six of 7 patients are stably engrafted off immunosuppression and without sickle cell-related symptoms at 2 to 8.5 years after HCT. Consistent with the complete resolution of SCD related symptoms observed in the 6 engrafted patients, erythropoiesis of complete or predominantly donor origin was detected by red blood cell-specific chimerism assays, despite their having persistent mixed chimerism in the mononuclear and lymphoid compartments. These findings demonstrate the curative potential of allogeneic HCT after an RIC regimen in patients with SCD.

Transfusion policy: when to stop the use of extremely rare blood for an allogeneic hematopoietic progenitor cell transplant recipient with a history of red cell alloimmunization

BACKGROUND

Decisions for when to select, and when to discontinue, antigen-negative blood in hematopoietic progenitor cell transplantation (HPCT) recipients with red blood cell (RBC) antibodies can be confusing. In HPCT performed for sickle cell anemia patients who require extremely rare antigen-negative blood, the balance of caution and practicality is further complicated.

CASE REPORTS

Four sickle cell anemia patients with current or historic RBC antibodies underwent allogeneic HPC transplantation. One required extremely rare (group O D-, hr(B)-) blood. None of the antibodies caused significant hemolysis after transplant. In the case requiring rare blood, antigen-negative blood was requested after donor RBC engraftment because of incomplete donor white blood cell (WBC) chimerism.

CONCLUSIONS

RBC antibodies derived from a recipient of allogeneic HPCT rarely cause significant hemolysis, in contrast to the more severe picture sometimes seen with donor-derived antibodies. When donor WBC chimerism is delayed past the time of donor RBC engraftment, there can be concern for the possibility of future recipient-type antibody production. Even 100 percent donor lymphocyte chimerism is no guarantee of total host plasma cell ablation. Immunoglobulin allotyping, when informative, can suggest chimerism for several years. Recipient-type blood, when extremely rare, may not be available for that duration.

Has stem cell transplantation come of age in the treatment of sickle cell disease?

Currently, hematopoietic SCT (HCT) is the only intervention that can restore normal hematopoiesis to provide a 'cure' in sickle cell disease. Yet, this treatment modality is used sparsely-a total of less than 400 transplants are reported in the Center for International Blood and Marrow Transplant Research database despite 70,000 afflicted in the United States; 88% of transplants are from HLA-matched sibling donors and 84% are <16 years of age at transplant. Overall survival at 3 years is over 90% after HCT in the young but 62% in adult HCT recipients due to increased disease and transplant-related morbidity. The decision and timing of HCT is a dilemma for physicians and families due to the need to consider HCT before severe organ damage in a disease that is generally not fatal in children with adequate supportive care. From the transplant physician's perspective, however, advances in the ability to identify well-matched donors, supportive care and promising conditioning regimens with low toxicity and transplant complications support the development of new HCT trials for sickle cell disease as the risk/benefit ratio can be balanced better. With the recognition of new predictors of early mortality, the anticipation of extensive and expensive life-long medical support, and the poor quality of life despite medical care, the scales tip in favor of HCT. This is prime time for the development of careful unrelated donor HCT trials for sickle cell disease. Research efforts targeting HCT will need to be directed at seeking safe and effective transplant methods applicable to all patients who might derive benefit.

Hematopoietic cell transplantation for sickle cell disease: state of the art

Sickle cell disease is associated with considerable morbidity and premature mortality. Hematopoietic cell transplantation offers the possibility of cure and is associated with excellent results in pediatric patients receiving stem cell transplantation from a matched sibling donor. A reduced-intensity conditioning regimen has the potential to further reduce regimen-related morbidity and mortality. Improved understanding of the natural history of complications, such as stroke and pulmonary hypertension, effects of treatments such as hydroxyurea and blood transfusions, as well as the impact of transplantation on organ damage, are likely to influence the timing and indication of transplantation. Improvements in preparative regimens may enable the safe use of an alternative source of stem cells, such as unrelated matched donors, and further improve the applicability and acceptability of this treatment.

Transplantation of a child with sickle cell anemia with an unrelated cord blood unit after reduced intensity conditioning

Sickle cell disease can be corrected by hematopoietic cell transplantation but success is limited by low availability of matched related/unrelated donors and comorbidities leading to the increased transplant-related morbidity/mortality. There is a need for expanded donor pools and reduced intensity regimens. We describe a case of a second unrelated cord blood transplant after a novel preparative regimen in a child with sickle cell disease related stroke and liver fibrosis. Hydroxyurea, rituximab, and alemtuzumab were followed by thiotepa and low dose total body irradiation before unrelated cord blood transplant. Rapid full donor chimerism and improved performance status was achieved and sustained over 2 years after transplant.