Outcomes after Allogeneic Transplant in Patients with Wiskott-Aldrich Syndrome

Wiskott-Aldrich syndrome: A new synonym mutation in the WAS gene

Wiskott-Aldrich syndrome (WAS) is a rare X-linked recessive primary immunodeficiency disorder. Mutations in the WAS gene are considered to be the primary cause of WAS. In this work, we report a boy who presented with intracranial hemorrhage (ICH) as an initial symptom and detects a novel pathogenic synonymous mutation in his WAS gene. His mother was a carrier of the mutant gene. The mutation, located at position c.273 (c.273 G>A) in exon 2, is a synonym mutation and predicted to affect protein expression by disrupting gene splicing. This study summarizes the diagnosis and treatment process of the patient and expands the genetic spectrum of WAS.

Outcomes of hematopoietic stem cell gene therapy for Wiskott-Aldrich syndrome

Wiskott-Aldrich syndrome (WAS) is a rare X-linked disorder characterized by combined immunodeficiency, eczema, microthrombocytopenia, autoimmunity, and lymphoid malignancies. Gene therapy (GT) to modify autologous CD34+ cells is an emerging alternative treatment with advantages over standard allogeneic hematopoietic stem cell transplantation for patients who lack well-matched donors, avoiding graft-versus-host-disease. We report the outcomes of a phase 1/2 clinical trial in which 5 patients with severe WAS underwent GT using a self-inactivating lentiviral vector expressing the human WAS complementary DNA under the control of a 1.6-kB fragment of the autologous promoter after busulfan and fludarabine conditioning. All patients were alive and well with sustained multilineage vector gene marking (median follow-up: 7.6 years). Clinical improvement of eczema, infections, and bleeding diathesis was universal. Immune function was consistently improved despite subphysiologic levels of transgenic WAS protein expression. Improvements in platelet count and cytoskeletal function in myeloid cells were most prominent in patients with high vector copy number in the transduced product. Two patients with a history of autoimmunity had flares of autoimmunity after GT, despite similar percentages of WAS protein-expressing cells and gene marking to those without autoimmunity. Patients with flares of autoimmunity demonstrated poor numerical recovery of T cells and regulatory T cells (Tregs), interleukin-10-producing regulatory B cells (Bregs), and transitional B cells. Thus, recovery of the Breg compartment, along with Tregs appears to be protective against development of autoimmunity after GT. These results indicate that clinical and laboratory manifestations of WAS are improved with GT with an acceptable safety profile. This trial is registered at clinicaltrials.gov as #NCT01410825.

Correcting inborn errors of immunity: From viral mediated gene addition to gene editing

Allogeneic hematopoietic stem cell transplantation is an effective treatment to cure inborn errors of immunity. Remarkable progress has been achieved thanks to the development and optimization of effective combination of advanced conditioning regimens and use of immunoablative/suppressive agents preventing rejection as well as graft versus host disease. Despite these tremendous advances, autologous hematopoietic stem/progenitor cell therapy based on ex vivo gene addition exploiting integrating γ-retro- or lenti-viral vectors, has demonstrated to be an innovative and safe therapeutic strategy providing proof of correction without the complications of the allogeneic approach. The recent advent of targeted gene editing able to precisely correct genomic variants in an intended locus of the genome, by introducing deletions, insertions, nucleotide substitutions or introducing a corrective cassette, is emerging in the clinical setting, further extending the therapeutic armamentarium and offering a cure to inherited immune defects not approachable by conventional gene addition. In this review, we will analyze the current state-of-the art of conventional gene therapy and innovative protocols of genome editing in various primary immunodeficiencies, describing preclinical models and clinical data obtained from different trials, highlighting potential advantages and limits of gene correction.

Allogeneic stem cell transplantation compared to conservative management in adults with inborn errors of immunity

Allogeneic hematopoietic stem cell transplantation (alloSCT) is curative for severe inborn errors of immunity (IEIs), with recent data suggesting alloSCT in adulthood is safe and effective in selected patients. However, questions remain regarding the indications for and optimal timing of transplant. We retrospectively compared outcomes of transplanted vs matched nontransplanted adults with severe IEIs. Seventy-nine patients (aged ≥ 15 years) underwent alloSCT between 2008 and 2018 for IEIs such as chronic granulomatous disease (n = 20) and various combined immune deficiencies (n = 59). A cohort of nontransplanted patients from the French Centre de Référence Déficits Immunitaires Héréditaires registry was identified blindly for case-control analysis, with ≤3 matched controls per index patient, without replacement. The nontransplanted patients were matched for birth decade, age at last review greater than index patient age at alloSCT, chronic granulomatous disease or combined immune deficiencies, and autoimmune/lymphoproliferative complications. A total of 281 patients were included (79 transplanted, 202 nontransplanted). Median age at transplant was 21 years. Transplant indications were mainly lymphoproliferative disease (n = 23) or colitis (n = 15). Median follow-up was 4.8 years (interquartile range, 2.5-7.2). One-year transplant-related mortality rate was 13%. Estimated disease-free survival at 5 years was higher in transplanted patients (58% vs 33%; P = .007). Nontransplanted patients had an ongoing risk of severe events, with an increased mean cumulative number of recurrent events compared with transplanted patients. Sensitivity analyses removing patients with common variable immune deficiency and their matched transplanted patients confirm these results. AlloSCT prevents progressive morbidity associated with IEIs in adults, which may outweigh the negative impact of transplant-related mortality.

Diagnosis and clinical management of Wiskott-Aldrich syndrome: current and emerging techniques

INTRODUCTION

Wiskott-Aldrich syndrome (WAS) serves as the prototype of how variants in a gene which encodes a protein central to actin cytoskeletal homeostasis can manifest clinically in a variety of ways including infection, atopy, autoimmunity, inflammation, bleeding, neutropenia, non-malignant lymphoproliferation, and malignancy. Despite the discovery of the WAS gene almost 30 years ago, our understanding of the pathophysiological mechanisms underlying WAS continues to unfold.

AREAS COVERED

This review will provide an overview of the approach to the diagnosis of WAS as well as the management of its associated complications. Advances in the use of allogeneic hematopoietic stem cell transplantation (HSCT) and gene therapy as well as the associated challenges unique to WAS will be discussed.

EXPERT OPINION

Basic research, combined with clinical research focusing on longitudinal analysis of WAS patients, will help clarify determinants that influence WAS pathogenesis as well as clinical complications and outcomes. Advances in curative approaches including the use of alternative donor HSCT for WAS continue to evolve. Gene therapy employing safer and more effective protocols ensuring full correction of WAS will provide life-saving benefit to WAS patients that are unable to undergo HSCT.

Clinical Features, Cancer Biology, Transplant Approach and Other Integrated Management Strategies for Wiskott-Aldrich Syndrome

Wiskott–Aldrich syndrome (WAS) is a rare X-linked recessive inborn error of immunity (IEI) first described in 1937. Classic WAS is characterized by the triad of thrombocytopenia with small platelets, recurrent infections due to combined immunodeficiency, and eczema. Hematopoietic stem cell transplantation (HSCT) was the only curative option available for five decades, with excellent outcomes reported for matched sibling donors (MSD) and matched unrelated donors (MUD). More recently, alternative donor transplants such as umbilical cord blood (UCB) and haploidentical transplant have emerged as viable options due to improvements in better graft selection, cell dosing, and effective allograft manipulation measures. Gene therapy is another potential curative option with promising results, yet currently is offered only as part of a clinical trial.

Hematopoietic Stem Cell Therapy for Wiskott-Aldrich Syndrome: Improved Outcome and Quality of Life

The Wiskott-Aldrich syndrome (WAS) is an X-linked disorder caused by mutations in the WAS gene resulting in congenital thrombocytopenia, eczema, recurrent infections and an increased incidence of autoimmune diseases and malignancies. Without curative therapies, affected patients have diminished life expectancy and reduced quality of life. Since WAS protein (WASP) is constitutively expressed only in hematopoietic stem cell-derived lineages, hematopoietic stem cell transplantation (HSCT) and gene therapy (GT) are well suited to correct the hematologic and immunologic defects. Advances in high-resolution HLA typing, new techniques to prevent GvHD allowing the use of haploidentical donors, and the introduction of reduced intensity conditioning regimens with myeloablative features have increased overall survival (OS) to over 90%. The development of GT for WAS has provided basic knowledge into vector selection and random integration of various viral vectors into the genome, with the possibility of inducing leukemogenesis. After trials and errors, inactivating lentiviral vectors carrying the WAS gene were successfully evaluated in clinical trials, demonstrating cure of the disease except for insufficient resolution of the platelet defect. Thus, 50 years of clinical evaluation, genetic exploration and extensive clinical trials, a lethal syndrome has turned into a curable disorder.

Gene therapy for primary immunodeficiencies

Primary immunodeficiencies (PIDs) are a group of rare inherited disorders of the immune system. Many PIDs are devastating and require a definitive therapy to prevent progressive morbidity and premature mortality. Allogeneic haematopoietic stem cell transplantation (alloHSCT) is curative for many PIDs, and while advances have resulted in improved outcomes, the procedure still carries a risk of mortality and morbidity from graft failure or graft-versus-host disease (GvHD). Autologous haematopoietic stem cell gene therapy (HSC GT) has the potential to correct genetic defects across haematopoietic lineages without the complications of an allogeneic approach. HSC GT for PID has been in development for the last two decades and the first licensed HSC-GT product for adenosine deaminase-deficient severe combined immunodeficiency (ADA-SCID) is now available. New gene editing technologies have the potential to circumvent some of the problems associated with viral gene-addition. HSC GT for PID shows great promise, but requires a unique approach for each disease and carries risks, notably insertional mutagenesis from gamma-retroviral gene addition approaches and possible off-target toxicities from gene-editing techniques. In this review, we discuss the development of HSC GT for PID and outline the current state of clinical development before discussing future developments in the field.

Higher Incidence of B Cell Malignancies in Primary Immunodeficiencies: A Combination of Intrinsic Genomic Instability and Exocytosis Defects at the Immunological Synapse

Congenital defects of the immune system called primary immunodeficiency disorders (PID) describe a group of diseases characterized by a decrease, an absence, or a malfunction of at least one part of the immune system. As a result, PID patients are more prone to develop life-threatening complications, including cancer. PID currently include over 400 different disorders, however, the variety of PID-related cancers is narrow. We discuss here reasons for this clinical phenotype. Namely, PID can lead to cell intrinsic failure to control cell transformation, failure to activate tumor surveillance by cytotoxic cells or both. As the most frequent tumors seen among PID patients stem from faulty lymphocyte development leading to leukemia and lymphoma, we focus on the extensive genomic alterations needed to create the vast diversity of B and T lymphocytes with potential to recognize any pathogen and why defects in these processes lead to malignancies in the immunodeficient environment of PID patients. In the second part of the review, we discuss PID affecting tumor surveillance and especially membrane trafficking defects caused by altered exocytosis and regulation of the actin cytoskeleton. As an impairment of these membrane trafficking pathways often results in dysfunctional effector immune cells, tumor cell immune evasion is elevated in PID. By considering new anti-cancer treatment concepts, such as transfer of genetically engineered immune cells, restoration of anti-tumor immunity in PID patients could be an approach to complement standard therapies.

Haploidentical stem cell transplantation with post-transplant cyclophosphamide for osteopetrosis and other nonmalignant diseases

Allogeneic hematopoietic stem cell transplantation (HSCT) is curative for a variety of nonmalignant disorders including osteopetrosis, bone marrow failures, and immune deficiencies. Haploidentical HSCT is a readily available option in the absence of a matched donor, but engraftment failure and other post-transplant complications are a concern. Post-transplant cyclophosphamide (PT-Cy) regimens are gaining popularity and recent reports show promising results. We report our experience with nine pediatric patients with nonmalignant diseases who were transplanted from a haploidentical donor with PT-Cy. From 2015 to 2019, nine children with nonmalignant diseases underwent haploidentical HSCT with PT-Cy, two as a second transplant and seven as primary grafts after upfront serotherapy and busulfan-based myeloablative conditioning. Patient’s diseases included osteopetrosis (n = 5), congenital amegakaryocytic thrombocytopenia (n = 2), hemophagocytic lymphohistiocytosis (n = 1), and Wiskott Aldrich syndrome (n = 1). Two patients failed to engraft following upfront PT-Cy transplants, one was salvaged with a second PT-Cy transplant, and the other with a CD34+ selected graft. None of the patients suffered from graft-versus-host disease. Three patients died from early posttransplant infectious complications and six patients are alive and well. In conclusion, haploidentical HSCT with PT-Cy is a feasible option for pediatric patients with nonmalignant diseases lacking a matched donor.

Hematopoietic Stem Cell Transplantation Beyond Severe Combined Immunodeficiency: Seeking a Cure for Primary Immunodeficiency

Hematopoietic stem cell transplantation (HSCT) can provide definitive therapy for patients with primary immunodeficiency disease (PIDD). Modern HSCT techniques and supportive care have significantly improved outcomes for patients with PIDD. This review examines current HSCT practice for PIDD other than severe combined immunodeficiency, and explores indications, risks, and long-term outcomes for this group of challenging diseases.

Primary immunodeficiencies and their associated risk of malignancies in children: an overview

Primary immunodeficiency disorders represent a heterogeneous spectrum of diseases, predisposing to recurrent infections, allergy, and autoimmunity. While an association between primary immunodeficiency disorders and increased risk of cancer has been suggested since the 1970s, renewed attention has been given to this topic in the last decade, largely in light of the availability of large registries as well as advances in next generation sequencing. In this narrative review, we will give an insight of the primary immunodeficiencies that are commonly responsible for the greater number of cancers in the primary immunodeficiency disorders population. We will describe clinical presentations, underlying genetic lesions (if known), molecular mechanisms for carcinogenesis, as well as some management considerations. We will also comment on the future directions and challenges related to this topic.Conclusion: The awareness of the association between several primary immunodeficiencies and cancer is crucial to provide the best care for these patients.What is Known: • Patients with primary immunodeficiency have an increased risk of malignancy. The type of malignancy is highly dependent on the specific primary immunodeficiency disorder.What is New: • Survival in patients with primary immunodeficiency disorders has been improving, and conversely also their lifetime risk of malignancy. • International collaboration and multinational registries are needed to improve our knowledge and therapeutic strategies.

Considerations for hematopoietic stem cell transplantation in primary immunodeficiency disorders

Primary immunodeficiency disorders (PIDs) result from inborn errors in immunity. Susceptibility to infections and oftentimes severe autoimmunity pose life-threatening risks to patients with these disorders. Hematopoietic cell transplant (HCT) remains the only curative option for many. Severe combined immunodeficiency disorders (SCID) most commonly present at the time of birth and typically require emergent HCT in the first few weeks of life. HCT poses an unusual challenge for PIDs. Donor source and conditioning regimen often impact the outcome of immune reconstitution after HCT in PIDs. The use of matched or unmatched, as well as related versus unrelated donor has resulted in variable outcomes for different subsets of PIDs. Additionally, there is significant variability in the success of engraftment even for a single patient’s lymphocyte subpopulations. While certain cell lines do well without a conditioning regimen, others will not reconstitute unless conditioning is used. The decision to proceed with a conditioning regimen in an already immunocompromised host is further complicated by the fact that alkylating agents should be avoided in radiosensitive PIDs. This manuscript reviews some of the unique elements of HCT in PIDs and evidence-based approaches to transplant in patients with these rare and challenging disorders.

A Systematic Review on Predisposition to Lymphoid (B and T cell) Neoplasias in Patients With Primary Immunodeficiencies and Immune Dysregulatory Disorders (Inborn Errors of Immunity)

Primary immunodeficiencies and immune dysregulatory disorders (PIDDs; now referred to as inborn errors in immunity) are rare disorders with a prevalence of 41. 4 or 50.5 per 100,000 persons (1). The incidence of malignancy in PIDD patents is the second-highest cause of death in children as well as adults, after infection, and is higher in certain PIDDs compared to others. We performed a systematic review of the literature to identify reports of B cell and T cell neoplasias in PIDDs and clustered them based on their classification in the IUIS schema. As would be expected, higher susceptibility to malignancies are typically reported in patients with Common Variable Immunodeficiency (CVID), combined immunodeficiencies affecting cellular immunity, in particular, DNA repair defects, or in the context of impaired immune regulatory control. There is not much evidence of increased risk for cancer in patients with innate immune defects, indicating that not all types of infection or genetic susceptibility predispose equally to cancer risk. Viral infections, in particular EBV, HHV and HPV, have been shown to increase susceptibility to developing cancer, but also patients with defects in immune regulation, such as Autoimmune Lymphoproliferative Syndrome (ALPS), activated p110delta syndrome (APDS type 1) and IL-10 receptor deficiency among others have a higher incidence of neoplastic disease, particularly lymphomas. In fact, lymphomas account for two-thirds of all malignancies reported in PIDD patients (2), with either a combined immunodeficiency or DNA repair defect predominating as the underlying immune defect in one registry, or antibody deficiencies in another (3). The vast majority of lymphomas reported in the context of PIDDs are B cell lymphomas, though T cell lymphomas have been reported in a few studies, and tend to largely be associated with chromosomal breakage disorders (4) or Cartilage Hair Hypoplasia (5). There appears to be a much higher prevalence of T cell lymphomas in patients with secondary immunodeficiencies (6), though this could reflect treatment bias. We reviewed the literature and summarized the reports of B and T cell lymphoma in PIDD patients to survey the current state of knowledge in this area.

Indications for haematopoietic stem cell transplantation for haematological diseases, solid tumours and immune disorders: current practice in Europe, 2019

This is the seventh special EBMT report on the indications for haematopoietic stem cell transplantation for haematological diseases, solid tumours and immune disorders. Our aim is to provide general guidance on transplant indications according to prevailing clinical practice in EBMT countries and centres. In order to inform patient decisions, these recommendations must be considered together with the risk of the disease, the risk of the transplant procedure and the results of non-transplant strategies. In over two decades since the first report, the EBMT indications manuscripts have incorporated changes in transplant practice coming from scientific and technical developments in the field. In this same period, the establishment of JACIE accreditation has promoted high quality and led to improved outcomes of patient and donor care and laboratory performance in transplantation and cellular therapy. An updated report with operating definitions, revised indications and an additional set of data with overall survival at 1 year and non-relapse mortality at day 100 after transplant in the commonest standard-of-care indications is presented. Additional efforts are currently underway to enable EBMT member centres to benchmark their risk-adapted outcomes as part of the Registry upgrade Project 2020 against national and/or international outcome data.

Inflammatory Bowel Disease: What Very Early Onset Disease Teaches Us

Inflammatory bowel disease (IBD) is a chronic inflammatory disorder of the gastrointestinal tract, of which ulcerative colitis and Crohn's disease are the 2 most prevailing entities. Very early onset IBD (VEO-IBD) children diagnosed with IBD under age 6 years. Although the etiology of IBD is mostly unknown, it involves a complex interaction among host genetics, microbiota, environmental factors, and aberrant immune responses. Advances in the understanding of the genetic contribution, which appears to be much more significant in younger children, gives us a useful insight into the pathogenesis and potential future therapeutic targets in IBD.