High incidence of lymphomas in a subgroup of Wiskott-Aldrich syndrome patients

Immune dysregulation as a leading principle for lymphoma development in diverse immunological backgrounds

Lymphoma is a heterogeneous group of malignancies arising from lymphocytes, which poses a significant challenge in terms of diagnosis and treatment due to its diverse subtypes and underlying mechanisms. This review aims to explore the shared and distinct features of various forms of lymphoma predisposing conditions, with a focus on genetic, immunological and molecular aspects. While diseases such as autoimmune disorders, inborn errors of immunity and iatrogenic immunodeficiencies are biologically and immunologically distinct, each of these diseases results in profound immune dysregulation and a predisposition to lymphoma development. Interestingly, the increased risk is often skewed towards a particular subtype of lymphoma. Patients with inborn errors of immunity in particular present with extreme forms of lymphoma predisposition, providing a unique opportunity to study the underlying mechanisms. External factors such as chronic infections and environmental exposures further modulate the risk of lymphoma development. Common features of conditions predisposing to lymphoma include: persistent inflammation, recurrent DNA damage or malfunctioning DNA repair, impaired tumor surveillance and viral clearance, and dysregulation of fundamental cellular processes such as activation, proliferation and apoptosis. Our growing understanding of the underlying mechanisms of lymphomagenesis provides opportunities for early detection, prevention and tailored treatment of lymphoma development.

Lymphadenopathy at the crossroad between immunodeficiency and autoinflammation: An intriguing challenge

Lymphadenopathies can be part of the clinical spectrum of several primary immunodeficiencies, including diseases with immune dysregulation and autoinflammatory disorders, as the clinical expression of benign polyclonal lymphoproliferation, granulomatous disease or lymphoid malignancy. Lymphadenopathy poses a significant diagnostic dilemma when it represents the first sign of a disorder of the immune system, leading to a consequently delayed diagnosis. Additionally, the finding of lymphadenopathy in a patient with diagnosed immunodeficiency raises the question of the differential diagnosis between benign lymphoproliferation and malignancies. Lymphadenopathies are evidenced in 15–20% of the patients with common variable immunodeficiency, while in other antibody deficiencies the prevalence is lower. They are also evidenced in different combined immunodeficiency disorders, including Omenn syndrome, which presents in the first months of life. Interestingly, in the activated phosphoinositide 3‐kinase delta syndrome, autoimmune lymphoproliferative syndrome, Epstein–Barr virus (EBV)‐related lymphoproliferative disorders and regulatory T cell disorders, lymphadenopathy is one of the leading signs of the entire clinical picture. Among autoinflammatory diseases, the highest prevalence of lymphadenopathies is observed in patients with periodic fever, aphthous stomatitis, pharyngitis, and cervical adenitis (PFAPA) and hyper‐immunoglobulin (Ig)D syndrome. The mechanisms underlying lymphoproliferation in the different disorders of the immune system are multiple and not completely elucidated. The advances in genetic techniques provide the opportunity of identifying new monogenic disorders, allowing genotype–phenotype correlations to be made and to provide adequate follow‐up and treatment in the single diseases. In this work, we provide an overview of the most relevant immune disorders associated with lymphadenopathy, focusing on their diagnostic and prognostic implications.

Immunodeficiency-Related Lymphoid Proliferations: New Insights With Relevance to Practice

PURPOSE OF REVIEW

Our understanding of risk factors and mechanisms underlying immunosuppression-related lymphoproliferative disorders continues to evolve. An increasing number of patients are living with altered immune status due to HIV, solid organ or hematopoietic stem cell transplant, treatment of autoimmune disease, or advanced age. This review covers advances in understanding, emerging trends, and revisions to diagnostic guidelines.

RECENT FINDINGS

The tumor microenvironment, including interactions between the host immune system and tumor cells, is of increasing interest in the setting of immunosuppression. While some forms of lymphoproliferative disease are associated with unique risk factors, common mechanisms are also emerging. Indolent forms, such as Epstein-Barr virus positive mucocutaneous ulcer, are important to recognize. As methods to modulate the immune system evolve, more data are needed to understand and minimize lymphoproliferative disease risk. A better understanding of individual risk factors and common mechanisms underlying immunosuppression-related lymphoproliferations will ultimately enable improved prevention and treatment of these disorders.

Spleen: Development, anatomy and reactive lymphoid proliferations

The unique architecture of the spleen enables it to play a key role in the interactions between the circulatory, reticuloendothelial and immune systems. Response to circulating antigens in the setting of infection, autoimmune disease or other conditions may result in a range of benign lymphoid proliferations. Moreover, patients with underlying immune deficiency may also show abnormal lymphoid proliferations within the spleen. This review will highlight the histologic, immunophenotypic and clinical features of reactive lymphoid proliferations to aid in their recognition and provide a context for understanding their development in relation to normal splenic structure and function.

Congenital Disorders of Platelet Function and Number

Mucocutaneous bleeding symptoms and/or persistent thrombocytopenia occur in individuals with congenital disorders of platelet function and number. Apart from bleeding, these disorders are often associated with additional hematologic and clinical manifestations, including auditory, immunologic, and oncologic disease. Autosomal recessive, dominant, and X-linked inheritance patterns have been demonstrated. Precise delineation of the molecular cause of the platelet disorder can aid the pediatrician in the detection and prevention of specific disorder-associated manifestations and guide appropriate treatment and anticipatory care for the patient and family.

Clinical Manifestations and Pathophysiological Mechanisms of the Wiskott-Aldrich Syndrome

The Wiskott-Aldrich syndrome (WAS) is a rare X-linked disorder originally described by Dr. Alfred Wiskott in 1937 and Dr. Robert Aldrich in 1954 as a familial disease characterized by infections, bleeding tendency, and eczema. Today, it is well recognized that the syndrome has a wide clinical spectrum ranging from mild, isolated thrombocytopenia to full-blown presentation that can be complicated by life-threatening hemorrhages, immunodeficiency, atopy, autoimmunity, and cancer. The pathophysiology of classic and emerging features is being elucidated by clinical studies, but remains incompletely defined, which hinders the application of targeted therapies. At the same time, progress of hematopoietic stem cell transplantation and gene therapy offer optimistic prospects for treatment options aimed at the replacement of the defective lymphohematopoietic system that have the potential to provide a cure for this rare and polymorphic disease.

Lymphoproliferative disorders in immunocompromised individuals and therapeutic antibodies for treatment

The incidence of lymphoproliferative disease (LPD) is significantly higher in individuals who have congenital, acquired or iatrogenically induced immunodeficiency. Although there are a wide range of LPDs including lymphoma and leukemia, this article only covers LPDs in patients with impaired immune function, which are called immunodeficiency-associated LPDs (ID-LPDs). Three of the four ID-LPD categories recognized by WHO have been selected for discussion: LPD in primary immune disorders, post-transplant LPD and LPD in HIV infection. Because of the high incidence and mortality of ID-LPDs, careful evaluation of the morphology, immunophenotype, genotype, viral status and clinical history is required for accurate diagnosis and treatment. Recently, treatment with monoclonal antibodies (mAbs) has been widely used and developed because of its potential benefits. The aim of this review is to describe new information concerning mAb treatment in LPDs and to draw physicians’ attention to mAb therapy, which should be effective for some types of LPD.

Wiskott-Aldrich syndrome; an x-linked primary immunodeficiency disease with unique and characteristic features

Wiskott-Aldrich syndrome (WAS) is an X-linked primary immunodeficiency disease with unique and characteristic features. In 1994, the responsible gene for WAS, the WASP gene on X-chromosome, was identified. Since then, renewed clinical and basic researches of WAS have started and remarkably developed. I will comment on recent progress in the clinical and basic researches of WAS, including some topics reported by our and other groups.

Preclinical safety and efficacy of human CD34(+) cells transduced with lentiviral vector for the treatment of Wiskott-Aldrich syndrome

Gene therapy with ex vivo-transduced hematopoietic stem/progenitor cells may represent a valid therapeutic option for monogenic immunohematological disorders such as Wiskott-Aldrich syndrome (WAS), a primary immunodeficiency associated with thrombocytopenia. We evaluated the preclinical safety and efficacy of human CD34⁺ cells transduced with lentiviral vectors (LV) encoding WAS protein (WASp). We first set up and validated a transduction protocol for CD34⁺ cells derived from bone marrow (BM) or mobilized peripheral blood (MPB) using a clinical grade, highly purified LV. Robust transduction of progenitor cells was obtained in normal donors and WAS patients' cells, without evidence of toxicity. To study biodistribution of human cells and exclude vector release in vivo, LV-transduced CD34⁺ cells were transplanted in immunodeficient mice, showing a normal engraftment and differentiation ability towards transduced lymphoid and myeloid cells in hematopoietic tissues. Vector mobilization to host cells and transmission to germline cells of the LV were excluded by different molecular assays. Analysis of vector integrations showed polyclonal integration patterns in vitro and in human engrafted cells in vivo. In summary, this work establishes the preclinical safety and efficacy of human CD34⁺ cells gene therapy for the treatment of WAS.

Relevance of laboratory testing for the diagnosis of primary immunodeficiencies: a review of case-based examples of selected immunodeficiencies

The field of primary immunodeficiencies (PIDs) is one of several in the area of clinical immunology that has not been static, but rather has shown exponential growth due to enhanced physician, scientist and patient education and awareness, leading to identification of new diseases, new molecular diagnoses of existing clinical phenotypes, broadening of the spectrum of clinical and phenotypic presentations associated with a single or related gene defects, increased bioinformatics resources, and utilization of advanced diagnostic technology and methodology for disease diagnosis and management resulting in improved outcomes and survival. There are currently over 200 PIDs with at least 170 associated genetic defects identified, with several of these being reported in recent years. The enormous clinical and immunological heterogeneity in the PIDs makes diagnosis challenging, but there is no doubt that early and accurate diagnosis facilitates prompt intervention leading to decreased morbidity and mortality. Diagnosis of PIDs often requires correlation of data obtained from clinical and radiological findings with laboratory immunological analyses and genetic testing. The field of laboratory diagnostic immunology is also rapidly burgeoning, both in terms of novel technologies and applications, and knowledge of human immunology. Over the years, the classification of PIDs has been primarily based on the immunological defect(s) ("immunophenotype") with the relatively recent addition of genotype, though there are clinical classifications as well. There can be substantial overlap in terms of the broad immunophenotype and clinical features between PIDs, and therefore, it is relevant to refine, at a cellular and molecular level, unique immunological defects that allow for a specific and accurate diagnosis. The diagnostic testing armamentarium for PID includes flow cytometry - phenotyping and functional, cellular and molecular assays, protein analysis, and mutation identification by gene sequencing. The complexity and diversity of the laboratory diagnosis of PIDs necessitates many of the above-mentioned tests being performed in highly specialized reference laboratories. Despite these restrictions, there remains an urgent need for improved standardization and optimization of phenotypic and functional flow cytometry and protein-specific assays. A key component in the interpretation of immunological assays is the comparison of patient data to that obtained in a statistically-robust manner from age and gender-matched healthy donors. This review highlights a few of the laboratory assays available for the diagnostic work-up of broad categories of PIDs, based on immunophenotyping, followed by examples of disease-specific testing.

IL-2-inducible T-cell kinase deficiency: clinical presentation and therapeutic approach

Mutations in the IL-2-inducible T-cell kinase gene have recently been shown to cause an autosomal recessive fatal Epstein Barr virus (EBV) associated lymphoproliferation. We report 3 cases from a single family who presented with EBV-positive B-cell proliferation diagnosed as Hodgkin's lymphoma. Single nucleotide polymorphism array-based genome-wide linkage analysis revealed IL-2-inducible T-cell kinase as a candidate gene for this disorder. All 3 patients harbored the same novel homozygous nonsense mutation C1764G which causes a premature stop-codon in the kinase domain. All cases were initially treated with chemotherapy. One patient remains in durable remission, the second patient subsequently developed severe hemophagocytic lymphohistiocytosis with multi-organ failure and died, and the third patient underwent a successful allogeneic bone marrow transplantation. IL-2-inducible T-cell kinase deficiency underlies a new primary immune deficiency which may account for part of the spectrum of Epstein Barr virus related lymphoproliferative disorders which can be successfully corrected by bone marrow transplantation.

An unusual self-limited clonal Mott cell proliferation with lymphoplasmacytic lymphoma-like features in a child with the Wiskott-Aldrich syndrome and Von Recklinghausen's neurofibromatosis

Patients with the Wiskott-Aldrich syndrome are at high risk for development of lymphomas, which are predominantly extranodal and of the immunoblastic type. We present a case of a self-limited lymphoproliferation with features of lymphoplasmacytic lymphoma arising in a patient with the Wiskott-Aldrich syndrome. The patient also had stigmata of von Recklinghausen's neurofibromatosis. The tumor was composed of CD138+, IgGkappa+, CD20-, PAX-5- Mott cells and CD5-, CD10-, CD19+, CD20+, CD43- small lymphoid B-cells that partially expressed CD23. The lymphadenopathy spontaneously resolved after a period of less than a year, and the patient had remained free of detectable lymphoproliferation for almost 4 years. He then developed Burkitt's lymphoma of the left parapharyngeal space. It is remarkable that both known lymphoproliferations with features of lymphoplasmatic lymphoma arising in patients with the Wiskott-Aldrich syndrome, this one and the previously described one, have spontaneously resolved. This observation is truly intriguing and requires further clinico-pathologic studies.

Development of lentiviral gene therapy for Wiskott Aldrich syndrome

BACKGROUND

Wiskott Aldrich syndrome (WAS) is a rare X-linked primary immunodeficiency. This complex disease is characterised by microthrombocytopenia, recurrent infections, eczema and is associated with a high incidence of autoimmunity and of lymphoid malignancies. WAS is attracting growing attention not only because it highlights the rich cellular and systems biology revolving around cytoskeletal regulation but also because it is candidate for a haematopoietic stem cell gene therapy indication.

OBJECTIVES

As several groups are developing this novel approach, this review discusses the state of the art and challenges in clinical development of gene therapy for WAS, with particular regard to biosafety.

METHODS

In spite of the successes of haematopoietic gene therapy for genetic immune deficiencies, there is a need for more efficient transduction protocols and for vectors with a superior safety profile. Preclinical studies have provided reasonable expectations that haematopoietic gene therapy with a self-inactivated HIV-1-derived vector using the native gene promoter for expression of the WAS transgene will be safe and will lead to the restoration of WAS protein in the haematopoietic and immune system at levels sufficient to provide an improvement in the condition of WAS patients.

CONCLUSIONS

Phase I/II clinical studies will soon be initiated in several European centres to assess the safety and efficacy of this lentiviral vector in WAS patients.

Combined Immune Deficiencies in Children

Combined immune deficiencies are a heterogeneous group of congenital disorders usually attributable to a single gene defect. The hallmark of these disorders is recurrent infections resulting from defects in both T- and B-cell function. This article reviews the basic components of the immune system as well as the clinical presentation, laboratory findings, and treatment for 3 distinct combined immune deficiencies.

Efficacy of gene therapy for Wiskott-Aldrich syndrome using a WAS promoter/cDNA-containing lentiviral vector and nonlethal irradiation

Wiskott-Aldrich syndrome (WAS) is a life-threatening X-linked primary immunodeficiency characterized by infections, hemorrhages, autoimmune disorders, and lymphomas. Transplantation of genetically corrected autologous hematopoietic stem cells (HSCs) could represent an alternative treatment to allogeneic HSC transplantation, the latter being often associated with severe complications. We used WAS-/- mice to test the efficacy of a gene therapy approach based on nonlethal irradiation followed by transplantation of WAS-/- HSCs transduced with lentiviral vectors encoding the WAS protein (WASP) from either the ubiquitous PGK promoter or the tissue- specific WAS promoter. The procedure resulted in significant levels of engraftment of WASP-expressing T cells, B cells, platelets, and myeloid cells. T cells harbored one or two vector copies and displayed partial to full correction of T cell receptor-driven interleukin-2 production and proliferation. In addition, polymerization of F-actin and localization of WASP at the site of the immunological synapse were restored. The treatment was well tolerated and no pathology was detected by systematic blood analysis and autopsy. The efficacy of WAS gene transfer into HSCs, using the WAS promoter-containing lentiviral vector, combined with nonlethal irradiation provides a strong rationale for the development of gene therapy for WAS patients.

Genotype-Proteotype Linkage in the Wiskott-Aldrich Syndrome

Wiskott-Aldrich syndrome (WAS) is a platelet/immunodeficiency disease arising from mutations of WAS protein (WASP), a hemopoietic cytoskeletal protein. Clinical symptoms vary widely from mild (X-linked thrombocytopenia) to life threatening. In this study, we examined the molecular effects of individual mutations by quantifying WASP in peripheral lymphocytes of 44 patients and identifying the molecular variant (collectively called proteotype). Nonpredicted proteotypes were found for 14 genotypes. These include WASP-negative lymphocytes found for five missense genotypes and WASP-positive lymphocytes for two nonsense, five frameshift, and two splice site genotypes. Missense mutations in the Ena/VASP homology 1 (EVH1) domain lead to decreased/absent WASP but normal mRNA levels, indicating that proteolysis causes the protein deficit. Because several of the EVH1 missense mutations alter WIP binding sites, the findings suggest that abrogation of WIP binding induces proteolysis. Whereas platelets of most patients were previously shown to lack WASP, WASP-positive platelets were found for two atypical patients, both of whom have mutations outside the EVH1 domain. WASP variants with alternative splicing and intact C-terminal domains were characterized for eight nonsense and frameshift genotypes. One of these, a nonsense genotype in a mild patient, supports expression of WASP lacking half of the proline-rich region. With one notable exception, genotype and proteotype were linked, indicating that a genotype-proteotype registry could be assembled to aid in predicting disease course and planning therapy for newly diagnosed infants. Knowledge of the molecular effect of mutations would aid also in identifying disease-modifying genes.

Lentiviral Vector-Mediated Gene Transfer in T Cells from Wiskott–Aldrich Syndrome Patients Leads to Functional Correction

Wiskott-Aldrich syndrome (WAS) is an X-linked primary immunodeficiency with a median survival below the age of 20 due to infections, severe hemorrhage, and lymphomas. Transplantation of hematopoietic stem cells from HLA-identical sibling donors is a resolutive treatment, but is available for a minority of patients. Transplantation of genetically corrected autologous hematopoietic stem cells or T cells could represent an alternative treatment applicable to all patients. We investigated whether WAS gene transfer with MMLV-based oncoretroviral and HIV-based lentiviral vectors could restore normal functions of patients' T cells. T cells transduced either with lentiviral vectors expressing the WAS protein (WASP) from the ubiquitous PGK promoter or the tissue-specific WASP promoter or with an oncoretroviral vector expressing WASP from the LTR, reached normal levels of WASP with correction of functional defects, including proliferation, IL-2 production, and lipid raft upregulation. Lentiviral vectors transduced T cells from WAS patients at higher rates, compared to oncoretroviral vectors, and efficiently transduced both activated and naive WAS T cells. Furthermore, a selective growth advantage of T cells corrected with the lentiviral vectors was demonstrated. The observation that lentiviral vector-mediated gene transfer results in correction of T cell defects in vitro supports their application for gene therapy in WAS patients.

Mechanisms of WASp-mediated hematologic and immunologic disease

The Wiskott-Aldrich syndrome protein (WASp) is a key regulator of actin polymerization in hematopoietic cells. The dynamic nature of cytoskeletal changes during a variety of cellular processes demands complex mechanisms for coordinated integration of input signals, precise localization within the cell, and regulated activation of the Arp2/3 complex. Mutations in the Wiskott-Aldrich syndrome gene either inhibit or dysregulate normal WASp function, resulting in clinical diseases with complex and disparate phenotypes. This review highlights recent advances that have enhanced our understanding of the mechanisms by which these molecular defects cause hematologic and immunologic disease.

Mutations of the Wiskott-Aldrich Syndrome Protein (WASP): hotspots, effect on transcription, and translation and phenotype/genotype correlation

The Wiskott-Aldrich syndrome (WAS) is an X-linked recessive immune deficiency disorder characterized by thrombocytopenia, small platelet size, eczema, recurrent infections, and increased risk of autoimmune disorders and malignancies. X-linked thrombocytopenia (XLT) is an allelic variant of WAS which presents with a milder phenotype, generally limited to thrombocytopenia. WAS and XLT are caused by mutations of the Wiskott-Aldrich syndrome protein (WASP) gene which encodes a 502-amino acid protein, named WASP. WASP is thought to play a role in actin cytoskeleton organization and cell signaling. Here, we report the identification of 141 unique mutations, 71 not previously reported, from 227 WAS/XLT families with a total of 262 affected members. When possible we studied the effects of these mutations on transcription, RNA splicing, and protein expression. By analyzing a large number of patients with WAS/XLT at the molecular level we identified 5 mutational hotspots in the WASP gene and have been able to establish a strong association between genotype and phenotype.