Mild SARS-CoV-2 Infection After Gene Therapy in a Child With Wiskott-Aldrich Syndrome: A Case Report

In this work we present the case of SARS-CoV-2 infection in a 1.5-year-old boy affected by severe Wiskott-Aldrich Syndrome with previous history of autoinflammatory disease, occurring 5 months after treatment with gene therapy. Before SARS-CoV-2 infection, the patient had obtained engraftment of gene corrected cells, resulting in WASP expression restoration and early immune reconstitution. The patient produced specific immunoglobulins to SARS-CoV-2 at high titer with neutralizing capacity and experienced a mild course of infection, with limited inflammatory complications, despite pre-gene therapy clinical phenotype.

Long-term outcome and chimerism in patients with Wiskott-Aldrich syndrome treated by hematopoietic cell transplantation: a retrospective nationwide survey

We analyzed the outcomes of allogeneic stem cell transplantation (SCT) and risk factors for chimerism in 108 patients with Wiskott-Aldrich syndrome (WAS) who were registered with The Japan Society for Hematopoietic Cell Transplantation between January 1985 and December 2016. A preparative conditioning regimen consisting of myeloablative conditioning (MAC) was provided to 76 patients, and reduced-intensity conditioning was provided to 30 patients. Fifty-one patients received prophylaxis against graft-versus-host disease (GVHD) with cyclosporine, and 51 patients received tacrolimus (Tac). Chimerism analyses had been performed in 91 patients. Neutrophil engraftment was achieved in 91 patients (84.3%). The engraftment rate was significantly higher in patients who received Tac for GVHD prophylaxis (p = 0.028). Overall survival rate (OS) was significantly higher in patients with complete chimerism than in patients with mixed chimerism (88.2 ± 6.1% and 66.7 ± 9.9%, respectively, p = 0.003). Multivariate analysis showed that the rate of complete chimerism in patients who received MAC including cyclophosphamide (CY) at a dose of 200 mg/kg was significantly higher (p = 0.021) than that in patients who received other conditioning. Thus, MAC including CY at a dose of 200 mg/kg and Tac for GVHD prophylaxis were optimal conditions of SCT for patients with WAS under existing study.

Childhood-onset inflammatory bowel diseases associated with mutation of Wiskott-Aldrich syndrome protein gene

AIM

To screen primary immunodeficiency, Wiskott-Aldrich syndrome (WAS), and chronic granulomatous disease (CGD) among children with inflammatory bowel disease (IBD).

METHODS

This was a single-center retrospective study. Eighteen children with IBD were investigated. We analyzed their expression of Wiskott-Aldrich syndrome protein (WASP) in lymphocytes and superoxide generation in phagocytes using flow cytometry. When the expression of WASP or superoxide generation was low or absent, we performed genetic analysis to determine the cause of this.

RESULTS

Eighteen patients were classified as having ulcerative colitis (n = 10), Crohn’s disease (n = 5), or IBD-unclassified (n = 3). In total, three patients revealed low expression of WASP associated with a WAS gene c.1378 C>T p.Pro460Ser mutation, which has previously been reported as a pathogenic mutation in WAS and X-linked thrombocytopenia. However, with respect to the major symptoms of WAS, none of these three patients showed either thrombocytopenia or increased susceptibility to infection, but one patient showed generalized eczema. No CGD patients were discovered in this study.

CONCLUSION

Despite the lack of typical clinical manifestations of WAS, low expression of WASP could be associated with the pathogenesis of a subtype of IBD patients.

CLINICAL FEATURES AND GENETIC ANALYSIS OF SIX PATIENTS WITH WISKOTT-ALDRICH SYNDROME REPORTING TWO NOVEL MUTATIONS: EXPERIENCE OF ERCIYES UNIVERSITY, KAYSERI, TURKEY

AIM

The Wiskott-Aldrich syndrome (WAS) is an X-linked immunodeficiency characterized by micro-thrombocytopenia, eczema, and recurrent infections. We aimed to share our experience with six children with WAS, including two patients with two novel mutations.

MATERIAL AND METHOD

We present phenotypical and laboratory description of six patients with WAS. The initial clinical presentation, biochemical and radiological features, molecular diagnosis together with long-term follow-up data are provided.

RESULTS

The patients showed increased serum levels of IgE; otherwise the serum levels of IgM were decreased. The percentages of CD3+ T cells were decreased or within lower limit. Four patients underwent molecular genetics analysis and Western blot studies; two of them showed unpublished mutations: a hemizygous splice site mutation in intron 8 (c.778-2A>T), and a hemizygous deletion in exon10 of the WASP gene (c.1017delT; p.S339fsX444) were detected. Western blot studies confirmed the reduced WAS protein expression in peripheral mononuclear blood cells in four studied patients.

CONCLUSIONS

The major characteristics of patients were thrombocytopenia with decreased mean platelet volume and bleeding. All patients had been previously misdiagnosed as idiopathic thrombocytopenic purpura, demonstrating the importance of a careful differential diagnosis, and intense evaluation.

Effects of eltrombopag on platelet count and platelet activation in Wiskott-Aldrich syndrome/X-linked thrombocytopenia

Because Wiskott-Aldrich syndrome (WAS) and X-linked thrombocytopenia (XLT) patients have microthrombocytopenia, hemorrhage is a major problem. We asked whether eltrombopag, a thrombopoietic agent, would increase platelet counts, improve platelet activation, and/or reduce bleeding in WAS/XLT patients. In 9 WAS/XLT patients and 8 age-matched healthy controls, platelet activation was assessed by whole blood flow cytometry. Agonist-induced platelet surface activated glycoprotein (GP) IIb-IIIa and P-selectin in WAS/XLT patients were proportional to platelet size and therefore decreased compared with controls. In contrast, annexin V binding showed no differences between WAS/XLT and controls. Eltrombopag treatment resulted in an increased platelet count in 5 out of 8 patients. Among responders to eltrombopag, immature platelet fraction in 3 WAS/XLT patients was significantly less increased compared with 7 pediatric chronic immune thrombocytopenia (ITP) patients. Platelet activation did not improve in 3 WAS/XLT patients whose platelet count improved on eltrombopag.

IN CONCLUSION

(1) the reduced platelet activation observed in WAS/XLT is primarily due to the microthrombocytopenia; and (2) although the eltrombopag-induced increase in platelet production in WAS/XLT is less than in ITP, eltrombopag has beneficial effects on platelet count but not platelet activation in the majority of WAS/XLT patients. This trial was registered at www.clinicaltrials.gov as #NCT00909363.

Large granular lymphocyte proliferation and revertant mosaicism: two rare events in a Wiskott-Aldrich syndrome patient

We report on a 6 year old patient with an unusual clinical presentation of WAS and oligoclonal proliferation of TCR+ large granular lymphocytes (LGL). Flow cytometry demonstrated two distinct populations of lymphocytes with strongly decreased (WASP-) or normal expression levels of WASP (WASP+), respectively. Molecular analysis confirmed a splice site mutation in intron 2 of the WASP gene in the WASP- cells but not in WASP+ cells. LGL cells were WASP+, suggesting that two independent rare events, somatic revertant mosaicism and LGL expansion, have occurred in a child with WAS. Our report points to diagnostic difficulties in the presence of partial WASP reversions and LGL.

Wiskott-Aldrich syndrome protein is involved in alphaIIb beta3-mediated cell adhesion

The Wiskott-Aldrich syndrome (WAS) is an X-chromosome-linked immunodeficiency disorder. The most common symptom seen in WAS patients is bleeding. One of the main causes of bleeding is defective platelet aggregation. The causative gene of WAS encodes WAS protein (WASP). Here, we show that WASP binds to the calcium- and integrin-binding protein (CIB) in platelets. CIB was originally identified as a protein binding to the alphaIIb cytoplasmic tail of platelet integrin alphaIIb beta3, which has a primary role in platelet aggregation. We also show that the WASP-CIB complex is important in alphaIIb beta3-mediated cell adhesion, and that in patients mutant forms of WASP are expressed at reduced levels or show lower affinities for CIB than wild-type WASP. Our results indicate that impaired complex formation between mutant WASPs and CIB reduces alphaIIb beta3-mediated cell adhesion and causes defective platelet aggregation, resulting in bleeding.

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.

Inherited Thrombocytopenias: Molecular Mechanisms

Each megakaryocyte forms 10(3) platelets and 10(11) platelets are replenished daily. The unique and amazing mechanisms that allow megakaryocytes to become giant and polyploid and to release such a large number of platelets are still poorly understood. The study of inherited thrombocytopenias offers the possibility to gain new information on these processes because several different forms, deriving from defective megakaryocytic commitment, differentiation, maturation, or platelet formation, have been identified. Moreover, in the presence of some genetic defects, megakaryocytes produce platelets with a shortened life span. In this review, we summarize what we have learned about inherited thrombocytopenias in the last few years.

Clinical course of patients with WASP gene mutations

Mutations of the Wiskott-Aldrich syndrome protein (WASP) gene result either in the classic Wiskott-Aldrich syndrome (WAS) or in a less severe form, X-linked thrombocytopenia (XLT). A phenotype-genotype correlation has been reported by some but not by other investigators. In this study, we characterized WASP gene mutations in 50 Japanese patients and analyzed the clinical phenotype and course of each. All patients with missense mutations were WASP-positive. In contrast, patients with nonsense mutations, large deletions, small deletions, and small insertions were WASP-negative. Patients with splice anomalies were either WASP-positive or WASP-negative. The clinical phenotype of each patient was correlated with the presence or absence of WASP. Lack of WASP expression was associated with susceptibility to bacterial, viral, fungal, and Pneumocystis carinii infections and with severe eczema, intestinal hemorrhage, death from intracranial bleeding, and malignancies. Rates for overall survival and survival without intracranial hemorrhage or other serious complications were significantly lower in WASP-negative patients. This analysis provides evidence for a strong phenotype-genotype correlation and demonstrates that WAS protein expression is a useful tool for predicting long-term prognosis for patients with WAS/XLT. Based on data presented here, hematopoietic stem cell transplantation should be considered, especially for WASP-negative patients, while the patients are young to improve prognosis.

WAVE2 deficiency reveals distinct roles in embryogenesis and Rac-mediated actin-based motility

The Wiskott-Aldrich syndrome related protein WAVE2 is implicated in the regulation of actin-cytoskeletal reorganization downstream of the small Rho GTPase, Rac. We inactivated the WAVE2 gene by gene-targeted mutation to examine its role in murine development and in actin assembly. WAVE2-deficient embryos survived until approximately embryonic day 12.5 and displayed growth retardation and certain morphological defects, including malformations of the ventricles in the developing brain. WAVE2-deficient embryonic stem cells displayed normal proliferation, whereas WAVE2-deficient embryonic fibroblasts exhibited severe growth defects, as well as defective cell motility in response to PDGF, lamellipodium formation and Rac-mediated actin polymerization. These results imply a non-redundant role for WAVE2 in murine embryogenesis and a critical role for WAVE2 in actin-based processes downstream of Rac that are essential for cell movement.

Autoimmunity in Wiskott-Aldrich syndrome: risk factors, clinical features, and outcome in a single-center cohort of 55 patients

OBJECTIVES

To evaluate the occurrence of autoimmune and inflammatory complications in Wiskott-Aldrich syndrome (WAS) and to determine risk factors and the prognosis of such complications with the aim of improving the definition of treatment options.

METHODS

We reviewed the records of 55 patients with WAS evaluated at Necker-Enfants Malades Hospital (Paris) from 1980 to 2000.

RESULTS

Forty patients (72%) had at least 1 autoimmune or inflammatory complication. Autoimmune hemolytic anemia was detected in 20 cases (36%); in all cases, onset occurred before the age of 5 years. Other complications included neutropenia (25%), arthritis (29%), skin vasculitis (22%), cerebral vasculitis (7%), inflammatory bowel disease (9%), and renal disease (3%). The median survival of the entire population was 14.5 years. Two autoimmune complications and 1 biological factor were predictive of a poor prognosis in this population: autoimmune hemolytic anemia, severe thrombocytopenia recurring after splenectomy, and high serum immunoglobulin M (IgM) levels before splenectomy. Autoimmune hemolytic anemia was significantly more observed in patients with high serum IgM level.

CONCLUSIONS

High serum IgM concentration before splenectomy was identified as a risk factor for autoimmune hemolytic anemia; however, it must be confirmed. Autoimmune hemolytic anemia and severe thrombocytopenia recurring after splenectomy were 2 indicators of a poor prognosis. Those results suggest that patients with WAS and IgM levels more than mean + 2 standard deviations before splenectomy should be placed under strict surveillance. Furthermore, severe autoimmune complications should lead, as early as possible, to hematopoietic stem cell transplantation using the best available donor.

Wiskott-Aldrich syndrome in a female

Wiskott-Aldrich syndrome (WAS) is an X-linked disease characterized by thrombocytopenia, eczema, and various degrees of immune deficiency. Carriers of mutated WASP have nonrandom X chromosome inactivation in their blood cells and are disease-free. We report data on a 14-month-old girl with a history of WAS in her family who presented with thrombocytopenia, small platelets, and immunologic dysfunction. Sequencing of the WASP gene showed that the patient was heterozygous for the splice site mutation previously found in one of her relatives with WAS. Sequencing of all WASP exons revealed no other mutation. Levels of WASP in blood mononuclear cells were 60% of normal. Flow cytometry after intracellular staining of peripheral blood mononuclear cells with WASP monoclonal antibody revealed both WASP(bright) and WASP(dim) populations. X chromosome inactivation in the patient's blood cells was found to be random, demonstrating that both maternal and paternal active X chromosomes are present. These findings indicate that the female patient has a defect in the mechanisms that lead in disease-free WAS carriers to preferential survival/proliferation of cells bearing the active wild-type X chromosome. Whereas the patient's lymphocytes are skewed toward WASP(bright) cells, about 65% of her monocytes and the majority of her B cells (CD19(+)) are WASP(dim). Her naive T cells (CD3(+)CD45RA(+)) include WASP(bright) and WASP(dim) populations, but her memory T cells (CD3(+)CD45RA(-)) are all WASP(bright). After activation in vitro of T cells, all cells exhibited CD3(+)CD45RA(-) phenotype and most were WASP(bright) with active paternal (wild-type) X chromosome, suggesting selection against the mutated WASP allele during terminal T-cell maturation/differentiation.

Mechanisms of CD47-induced caspase-independent cell death in normal and leukemic cells: link between phosphatidylserine exposure and cytoskeleton organization

Dying cells, apoptotic or necrotic, are swiftly eliminated by professional phagocytes. We previously reported that CD47 engagement by CD47 mAb or thrombospondin induced caspase-independent cell death of chronic lymphocytic leukemic B cells (B-CLL). Here we show that human immature dendritic cells (iDCs) phagocytosed the CD47 mAb-killed leukemic cells in the absence of caspases 3, 7, 8, and 9 activation in the malignant lymphocytes. Yet the dead cells displayed the cytoplasmic features of apoptosis, including cell shrinkage, phosphatidylserine exposure, and decreased mitochondrial transmembrane potential (DeltaPsim). CD47 mAb-induced cell death also occurred in normal resting and activated lymphocytes, with B-CLL cells demonstrating the highest susceptibility. Importantly, iDCs and CD34(+) progenitors were resistant. Structure-function studies in cell lines transfected with various CD47 chimeras demonstrated that killing exclusively required the extracellular and transmembrane domains of the CD47 molecule. Cytochalasin D, an inhibitor of actin polymerization, and antimycin A, an inhibitor of mitochondrial electron transfer, completely suppressed CD47-induced phosphatidylserine exposure. Interestingly, CD47 ligation failed to induce cell death in mononuclear cells isolated from Wiskott-Aldrich syndrome (WAS) patients, suggesting the involvement of Cdc42/WAS protein (WASP) signaling pathway. We propose that CD47-induced caspase-independent cell death be mediated by cytoskeleton reorganization. This form of cell death may be relevant to maintenance of homeostasis and as such might be explored for the development of future therapeutic approaches in lymphoid malignancies.

Normal Arp2/3 complex activation in platelets lacking WASp

Arp2/3 complex is believed to induce de novo nucleation of actin filaments at the edge of motile cells downstream of WASp family proteins. In this study, the signaling pathways leading to Arp2/3 complex activation, actin assembly, and shape change were investigated in platelets isolated from patients with Wiskott-Aldrich Syndrome (WAS), that is, who lack WASp, and in WASp-deficient mouse platelets. WASp-deficient human and mouse platelets elaborate filopodia, spread lamellae, and assemble actin, identical to control WASp-expressing platelets. Human platelets contain 2 microM Arp2/3 complex, or 8600 molecules/cell. Arp2/3 complex redistributes to the edge of the lamellae and to the Triton X-100-insoluble actin cytoskeleton of activated WASp-deficient platelets. Furthermore, the C-terminal CA domain of N-WASp, which sequesters Arp2/3 complex, inhibits by half the actin nucleation capacity of octylglucoside-permeabilized and activated WAS platelets, similar to its effect in WASp-expressing cells. Along with WASp, platelets express WAVE-2 as a physiologic activator of Arp2/3 complex and a small amount of N-WASp. Taken together, our findings show that platelets activate Arp2/3 complex, assemble actin, and change shape in the absence of WASp, indicating a more specialized role for WASp in these cells.

WASp in immune-system organization and function

The regulation of many immunological events depends on systems that mediate dynamic actin reorganization in response to signals from the cell membrane. The Wiskott-Aldrich syndrome protein (WASp) is the founding member of a family of proteins that have emerged as crucial effectors of Rho GTPases and activators of the cytoskeletal-organizing complex Arp2/3. Now, WASp has been shown to be intimately involved in many pathways that influence the function of the immune system. Disturbances in these systems result in the complex immunodysregulation of Wiskott-Aldrich syndrome.

Treatment of severe thrombocytopenia with IL-11 in children with Wiskott-Aldrich syndrome

This report examines the safety and efficacy of IL-11 in treating severe thrombocytopenia secondary to Wiskott-Aldrich syndrome in two pediatric patients before allogeneic stem cell transplantation (SCT). Both patients had a substantial increase in their platelet counts and a decrease in bleeding episodes and platelet transfusions. The median platelet count increased from 32,000/mm3 to 64,000/mm3. Each subsequently received allogeneic SCT; 1 year after transplantation, both are reconstituted with 100% donor hematopoietic stem cells with sustained normal platelet counts (>200 K/mm3). Larger studies are required to confirm this observation of the safety and efficacy of IL-11 in this setting.

Missense mutations of the WASP gene cause intermittent X-linked thrombocytopenia

Mutations of the WASP gene have been previously shown to be responsible for classical Wiskott-Aldrich syndrome, isolated X-linked thrombocytopenia, and severe, congenital X-linked neutropenia. We report herewith 2 families in which affected males had a history of intermittent thrombocytopenia with consistently reduced platelet volume, in the absence of other major clinical features, and carried missense mutations of the WASP gene that allowed substantial protein expression. This observation broadens the spectrum of clinical phenotypes associated with WASP gene defects, and it indicates the need for molecular analysis in males with reduced platelet volume, regardless of the platelet number.

Flow cytometric determination of intracytoplasmic Wiskott-Aldrich syndrome protein in peripheral blood lymphocyte subpopulations

We have produced a novel monoclonal antibody (mAb) directed against Wiskott-Aldrich syndrome protein (WASP) by immunizing mice with the recombinant protein. The mAb designated 5A5 is highly specific to WASP and suitable for Western blot analysis and immunoprecipitation. A flow cytometric assay using the 5A5 mAb identifies expression of intracytoplasmic WASP in lymphocytes from normal individuals. Double staining analysis with cell surface CD3, CD19, and CD56, and intracytoplasmic molecules revealed WASP expression in each subpopulation. With regard to WASP expression in patients with Wiskott-Aldrich syndrome (WAS) and X-linked thrombocytopenia (XLT), peripheral blood mononuclear cells (PBMCs) from nine patients and Epstein-Barr virus-transformed B-lymphoblastoid cell lines from seven patients examined did not show WASP expression by flow cytometric analysis. These results were confirmed by Western blot analysis. We conclude that WASP expression in lymphocyte subpopulations from patients with WAS and XLT can be more precisely evaluated by flow cytometry as compared with Western blot analysis. This flow cytometry method is important as a supplement to Western blots, but even more important as an alternative and powerful assay that can contribute to research on WASP as well as diagnosis in a clinical setting.

WASP and N-WASP in human platelets differ in sensitivity to protease calpain

Mutations of Wiskott-Aldrich syndrome protein (WASP) underlie the severe thrombocytopenia and immunodeficiency of the Wiskott-Aldrich syndrome. WASP, a specific blood cell protein, and its close homologue, the broadly distributed N-WASP, function in dynamic actin polymerization processes. Here it is demonstrated that N-WASP is expressed along with WASP, albeit at low levels, in human blood cells. The presence of approximately 160 nmol/L rapidly acting N-WASP molecules may explain the normal capacity of WASP-negative patient platelets for early agonist-induced aggregation and filopodia formation. Ex vivo experiments revealed a significant difference between WASP and N-WASP in sensitivity to calpain, the Ca++-dependent protease activated in agonist-stimulated platelets. Through the use of a series of calpain-containing broken cell systems, it is shown that WASP is cleaved in a Ca++-dependent reaction inhibitable by calpeptin and E64d and that N-WASP is not cleaved, suggesting that the cleavage of WASP by calpain functions in normal platelets as part of a Ca++-dependent switch mechanism that terminates the surface projection phase of blood cell activation processes.

The interaction between Cdc42 and WASP is required for SDF-1-induced T-lymphocyte chemotaxis

In studies aimed at further characterizing the cellular immunodeficiency of the Wiskott-Aldrich syndrome (WAS), we found that T lymphocytes from WAS patients display abnormal chemotaxis in response to the T-cell chemoattractant stromal cell-derived factor (SDF)-1. The Wiskott- Aldrich syndrome protein (WASP), together with the Rho family GTPase Cdc42, control stimulus-induced actin cytoskeleton rearrangements that are involved in cell motility. Because WASP is an effector of Cdc42, we further studied how Cdc42 and WASP are involved in SDF-1-induced chemotaxis of T lymphocytes. We provide here direct evidence that SDF-1 activates Cdc42. We then specifically investigated the role of the interaction between Cdc42 and WASP in SDF-1-responsive cells. This was achieved by abrogating this interaction with a recombinant polypeptide (TAT-CRIB), comprising the Cdc42/Rac interactive binding (CRIB) domain of WASP and a human immunodeficiency virus-TAT peptide that renders the fusion protein cell-permeant. This TAT-CRIB protein was shown to bind specifically to Cdc42-GTP and to inhibit the chemotactic response of a T-cell line to SDF-1. Altogether, these data demonstrate that Cdc42-WASP interaction is critical for SDF-1-induced chemotaxis of T cells.

Wiskott-Aldrich syndrome protein and platelets

Wiskott-Aldrich syndrome (WAS) and X-linked thrombocy topenia (XLT) are caused by mutations of the WAS protein (WASP) gene. The manifestations of the classic WAS phenotype consist of immunodeficiency, eczema and thrombocytopenia. However, thrombocytopenia and small platelets are the only consistent features of WAS and XLT. The exact mechanisms of the development of thrombocytopenia in patients with WAS or XLT are unknown. To date, platelets are the only primary cells in which inducible tyrosine phosphorylation of WASP has been consistently demonstrated. This review focuses on the recent progress in dissecting the causes of thrombocytopenia and the emerging understanding of WASP phosphorylation.

Impaired interleukin-2 production in T-cells from a patient with Wiskott-Aldrich syndrome: basis of clinical effect of interleukin-2 replacement therapy

Interleukin-2 production may be one of the underlying causes of Wiskott-Aldrich syndrome immunodeficiency and recombinant interleukin-2 administration (or an infusion of T-cells expanded by CD3 stimulation and rIL-2) is able, to some extent, to restore defective T-cell function.

Determination of carrier status for the Wiskott-Aldrich syndrome by flow cytometric analysis of Wiskott-Aldrich syndrome protein expression in peripheral blood mononuclear cells

The Wiskott-Aldrich syndrome (WAS) is caused by defects in the WAS protein (WASP) gene on the X chromosome. Previous study disclosed that flow cytometric analysis of intracellular WASP expression (FCM-WASP analysis) in lymphocytes was useful for the diagnosis of WAS patients. Lymphocytes from all WAS patients showed WASPdim instead of WASPbright. Here we report that FCM-WASP analysis in monocytes could be a useful tool for the WAS carrier diagnosis. Monocytes from all nine WAS carriers showed varied population of WASPdim together with WASPbright. None of control individuals possessed the WASPdim population. In contrast, lymphocytes from all the carriers except two lacked the WASPdim population. The difference of the WASPdim population in monocytes and lymphocytes observed in WAS carriers suggests that WASP plays a more critical role in the development of lymphocytes than in that of monocytes. The present studies suggest that a skewed X-chromosomal inactivation pattern observed in WAS carrier peripheral blood cells is not fixed at the hemopoietic stem cell level but progresses after the lineage commitment.

Actin cytoskeletal function is spared, but apoptosis is increased, in WAS patient hematopoietic cells

Mutations in the Wiskott-Aldrich syndrome protein (WASP) have been hypothesized to cause defective actin cytoskeletal function. This resultant dysfunction of the actin cytoskeleton has been implicated in the pathogenesis of Wiskott-Aldrich syndrome (WAS). In contrast, it was found that stimulated actin polymerization is kinetically normal in the hematopoietic lineages affected in WAS. It was also found that the actin cytoskeleton in WAS platelets is capable of producing the hallmark cytoarchitectural features associated with activation. Further analysis revealed accelerated cell death in WAS lymphocytes as evidenced by increased caspase-3 activity. This increased activity resulted in accelerated apoptosis of these cells. CD95 expression was also increased in these cells, suggesting an up-regulation in the FAS pathway in WAS lymphocytes. Additionally, inhibition of actin polymerization in lymphocytes using cytochalasin B did not accelerate apoptosis in these cells. This suggests that the accelerated apoptosis observed in WAS lymphocytes was not secondary to an underlying defect in actin polymerization caused by mutation of the WAS gene. These data indicate that WASP does not play a universal role in signaling actin polymerization, but does play a role in delaying cell death. Therefore, the principal consequence of mutations in the WAS gene is to accelerate lymphocyte apoptosis, potentially through up-regulation of the FAS-mediated cell death pathway. This accelerated apoptosis may ultimately give rise to the clinical manifestations observed in WAS. (Blood. 2000;95:1283-1292)

Mutations of the WASP gene in 10 Japanese patients with Wiskott-Aldrich syndrome and X-linked thrombocytopenia

Wiskott-Aldrich syndrome (WAS) is an X-linked recessive disorder characterized by thrombocytopenia, immunodeficiency, and eczema. X-linked thrombocytopenia (XLT) is a mild form of WAS with isolated thrombocytopenia. Both phenotypes are caused by mutation of the Wiskott-Aldrich syndrome protein (WASP) gene. In this study, we identified mutations of the WASP gene in 10 Japanese patients from 9 unrelated families with WAS/XLT. All XLT patients (n = 3) and one WAS patient had a missense mutation at the PH domain of WASP. Two WAS patients had nonsense mutations. One WAS patient had exon 8 skipping caused by one nucleotide deletion at the acceptor site of intron 7. Three WAS patients had genomic deletions; one of the three had a large genomic deletion involving exons 3 to 7. Codons 45 and 86 seem to be the hot spots of the WASP mutation, because missense mutations in these codons have been reported previously in several WAS/XLT patients in addition to the patients in this report, and patients with the same mutation show a similar clinical phenotype. All other mutations are novel, indicating that the mutations of WASP are heterogeneous. EB virus-transformed cell lines from XLT patients expressed nearly normal amounts of WASP, whereas those from typical WAS patients expressed almost undetectable amounts of WASP. We conclude that the analysis of gene mutation and protein expression of WASP are useful together in assessing the severity of WAS.

Regulation and function of WASp in platelets by the collagen receptor, glycoprotein VI

Wiskott Aldrich syndrome (WAS) is an X-linked recessive disorder associated with abnormalities in platelets and lymphocytes giving rise to thrombocytopenia and immunodeficiency. WAS is caused by a mutation in the gene encoding the cytoskeletal protein (WASp). Despite its importance, the role of WASp in platelet function is not established. WASp was recently shown to undergo tyrosine phosphorylation in platelets after activation by collagen, suggesting that it may play a selective role in activation by the adhesion molecule. In the present study, we show that WASp is heavily tyrosine phosphorylated by a collagen-related peptide (CRP) that binds to the collagen receptor glycoprotein (GP) VI, but not to the integrin alpha2beta1. Tyrosine phosphorylation of WASp was blocked by Src family kinase inhibitors and reduced by treatment with wortmannin and in patients with X-linked agammaglobulinemia (XLA), a condition caused by a lack of functional expression of Btk. This indicates that Src kinases, phosphatidylinositol 3-kinase (PI 3-kinase), and Btk all contribute to the regulation of tyrosine phosphorylation of WASp. The functional importance of WASp was investigated in 2 WAS brothers who show no detectable expression of WASp. Platelet aggregation and secretion from dense granules induced by CRP and thrombin was slightly enhanced in the WAS platelets relative to controls. Furthermore, there was no apparent difference in morphology in WAS platelets after stimulation by these agonists. These observations suggest that WASp does not play a critical role in intracellular signaling downstream of tyrosine kinase-linked and G protein-coupled receptors in platelets.

WASP levels in platelets and lymphocytes of wiskott-aldrich syndrome patients correlate with cell dysfunction

Wiskott-Aldrich syndrome, an inherited blood cell disorder due to mutations of the X-chromosome gene WASP (Wiskott-Aldrich syndrome protein), was characterized originally by thrombocytopenia, immunodeficiency, and eczema. Whereas platelet dysfunction is severe and consistent, immune defects are clinically variable, ranging from negligible to life threatening. To understand this heterogeneity, we quantified WASP in PBMC and platelets, and also in neutrophils, of patients with diverse mutations. A surprisingly complex pattern of WASP expression found for lymphoid cells formed the basis for dividing the patient mutations into four groups. Group A have low WASP levels in PBMC and higher levels in EBV cell lines, as well as near normal WASP RNA levels (7 patients, most with mild disease), suggesting that group A WASP molecules are hypersusceptible to proteolysis. Group B have low WASP levels in PBMC and EBV cells and similar low RNA levels (2 patients, moderate disease). Group C have discordant expression: WASP-positive peripheral T cells and WASP-negative peripheral B cells and EBV cell lines (9 patients, variable disease severity). Noteworthy among group C kindred are several instances of B cell lymphomas. In group D, PBMC and EBV cell lines are WASP negative (7 patients, severe disease). In contrast to the complex lymphoid cell expression patterns, all patient platelets examined were WASP negative (18 diverse patients). WASP absence in platelets provides an apparent molecular explanation for the universally severe platelet dysfunction in this disease, and the cumulative lymphoid cell findings suggest that WASP levels play a substantial role in determining immune outcome.

Pathological events in platelets of Wiskott-Aldrich syndrome patients

The Wiskott-Aldrich syndrome (WAS) is a severe X-linked platelet/immunological disorder arising from mutations of the gene WASP. At the clinical level, the major platelet abnormalities are small size and low number, both partially correctable by splenectomy. To identify underlying pathological events, we examined WAS platelets at various stages of their lifetime. In spleen sections from WAS patients, fluorescence microscopy showed dramatic co-localization of markers of platelets (CD41) and macrophages (CD68) compared to non-thrombocytopenic controls, suggesting that WAS splenic macrophages are involved in platelet removal. Study of isolated WAS blood platelets by flow cytometry showed substantial enhancement of surface exposure of phosphatidylserine (PS), a signal for engulfment by macrophages. Isolated resting WAS platelets were also aberrantly susceptible to microparticle release, and plasma samples of WAS patients contained > 5 times normal numbers of platelet-derived microparticles which may explain the small size of circulating platelets. Measurements with the Ca2+ sensitive dye fluo-3 revealed significantly increased Ca2+ levels, 310 +/- 13 nmol/l for WAS platelets versus 106 +/- 12 nmol/l for normal platelets, and also prolongation of agonist-induced Ca2+ flux. Cumulatively, these studies identify abnormal events occurring in WAS platelets: increased Ca2+ levels and enhancement of two Ca2+ dependent processes, PS exposure and microparticle release; these abnormal events may contribute to the in vivo decrease of platelet number and reduction of platelet size in this disease.

Telomere length changes in patients undergoing hematopoietic stem cell transplantation

Telomere length indicates the replicative history of cells, serving as a molecular measure of the replicative potential remaining in cells. To investigate telomere length changes in hematopoietic stem cells, patients undergoing hematopoietic stem cell transplantation (HSCT) were evaluated. Fifteen patients after allogeneic bone marrow transplantation (allo-BMT group), seven patients after autologous peripheral blood stem cell transplantation (auto-PBSCT group), and 39 healthy controls were studied. Telomere length was measured in peripheral mononuclear cells by Southern blot hybridization. There was no significant difference between the allo-BMT and the auto-PBSCT groups. In the allo-BMT group, the mean telomere length of recipients was 2.01 kb shorter than that of their donors (P = 0. 008), and was 1.59 kb shorter than that of age-matched putative normal controls (P = 0.002). Telomere shortening in the allo-BMT group was equivalent to 41.4 years of aging in the donors, and to 52. 4 years of aging in the normal controls. The mean telomere length in the auto-PBSCT group was 2.36 kb shorter than that of the age-matched putative controls (P = 0.043), which was equivalent to 61.5 years of aging in normal controls. The extent of telomere shortening in the allo-BMT group showed a trend to negative correlation with the number of mononuclear cells infused. These findings suggest that hematopoietic stem cells after HSCT lose telomere length and these shortened telomeres may result in a higher incidence of clonal disorders later in life.

The thrombocytopenia of Wiskott Aldrich syndrome is not related to a defect in proplatelet formation

The Wiskott-Aldrich syndrome (WAS) is an X-linked hereditary disease characterized by thrombocytopenia with small platelet size, eczema, and increased susceptibility to infections. The gene responsible for WAS was recently cloned. Although the precise function of WAS protein (WASP) is unknown, it appears to play a critical role in the regulation of cytoskeletal organization. The platelet defect, resulting in thombocytopenia and small platelet size, is a consistent finding in patients with mutations in the WASP gene. However, its exact mechanism is unknown. Regarding WASP function in cytoskeletal organization, we investigated whether these platelet abnormalities could be due to a defect in proplatelet formation or in megakaryocyte (MK) migration. CD34(+) cells were isolated from blood and/or marrow of 14 WAS patients and five patients with hereditary X-linked thrombocytopenia (XLT) and cultured in serum-free liquid medium containing recombinant human Mpl-L (PEG-rHuMGDF) and stem-cell factor (SCF) to study in vitro megakaryocytopoiesis. In all cases, under an inverted microscope, normal MK differentiation and proplatelet formation were observed. At the ultrastructural level, there was also no abnormality in MK maturation, and normal filamentous MK were present. Moreover, the in vitro produced platelets had a normal size, while peripheral blood platelets of the same patients exhibited an abnormally small size. However, despite this normal platelet production, we observed that F-actin distribution was abnormal in MKs from WAS patients. Indeed, F-actin was regularly and linearly distributed under the cytoplasmic membrane in normal MKs, but it was found concentrated in the center of the WAS MKs. After adhesion, normal MKs extended very long filopodia in which WASP could be detected. In contrast, MKs from WAS patients showed shorter and less numerous filopodia. However, despite this abnormal filopodia formation, MKs from WAS patients normally migrated in response to stroma-derived factor-1alpha (SDF-1alpha), and actin normally polymerized after SDF-1alpha or thrombin stimulation. These results suggest that the platelet defect in WAS patients is not due to abnormal platelet production, but instead to cytoskeletal changes occuring in platelets during circulation.

The cytoskeletal linker protein moesin: decreased levels in Wiskott-Aldrich syndrome platelets and identification of a cleavage pathway in normal platelets

The Wiskott-Aldrich syndrome (WAS) is a severe disease of platelets (small size, thrombocytopenia) and lymphocytes (immunodeficiency) arising from mutations of the X-chromosome gene WASP. Because of the prominent role of cytoskeletal abnormalities, particularly the paucity of surface microvilli, in the cellular pathology of this disease, blood cells from WAS patients were examined for moesin, a cytoskeletal linker protein that stabilizes cell surface microvilli, filopodia and lamellipodia. Comparison of patient and normal lymphocytes by immunofluorescence microscopy and immunoblotting showed normal levels and distribution of moesin in lymphocytes of WAS patients. In contrast, platelets from WAS patients stained only dimly for moesin relative to normal platelets. Quantitation by immunoblot revealed significantly decreased moesin levels in WAS patient platelets relative to normal platelets (63.5 +/- 4.9% of normal levels, n = 8, P < 0.0001). A novel reaction of normal platelets was discovered that may play a role in the depletion of moesin in patient platelets, namely the cleavage of moesin as a late event in platelet activation in response to certain platelet agonists.

Intrinsic dendritic cell abnormalities in Wiskott-Aldrich syndrome

Wiskott-Aldrich syndrome (WAS) is an X-linked disorder characterized by immune deficiency, eczema, and microthrombocytopenia. Biochemical evidence indicates that the Wiskott-Aldrich syndrome protein (WASp) is involved in regulating the actin cytoskeleton. Here we report that WAS dendritic cells (DC) have an immunophenotype very similar to normal DC. However, as a consequence of an intrinsically abnormal cytoarchitecture, they are unable to polarize normally and have severely reduced translocational motility in vitro. These findings indicate that WASp is an essential effector for Cdc-42-mediated polarization of primary hematopoietic cells, and suggest that a significant component of the clinical phenotype of WAS could arise from peripheral DC dysmotility and aberrant immune cell trafficking in vivo. Intrinsic dysfunction of the DC population may also have an important role in the pathogenesis of other primary immunodeficiency syndromes, while induced changes in DC cytoskeletal signaling pathways may contribute to the initiation of acquired immunological and inflammatory disorders.

Collagen induces tyrosine phosphorylation of Wiskott-Aldrich syndrome protein in human platelets

Wiskott-Aldrich syndrome (WAS) and X-linked thrombocytopenia (XLT) are caused by mutations of the WAS protein (WASP) gene. All hematopoietic stem cell-derived lineages, including platelets, express WASP. Platelets from WAS patients are smaller than their normal counterparts and defects in platelet aggregation and actin polymerization have been reported. To determine if WASP is important for normal platelet function, we examined its role in signal transduction. We found that collagen but not thrombopoietin or thrombin induces a rapid and robust increase in tyrosine phosphorylation of platelet-associated WASP. Collagen-induced tyrosine phosphorylation of WASP was inhibited by cytochalasin D and wortmannin, respectively, suggesting that actin polymerization and phosphatidylinositol 3-kinase (PI3-kinase) play a role in the induction of tyrosine phosphorylation of WASP. Binding of glutathion S-transferase (GST)-Grb2 to WASP was seen in the lysate of resting platelets. The binding was reduced when lysates from collagen-stimulated platelets were incubated with GST-Grb2, suggesting that tyrosine phosphorylation of WASP may directly or indirectly modulate the adapter function of WASP. Although thrombin- and thrombopoietin-induced increase in tyrosine phosphorylation of WASP is negligible or marginal, WASP from thrombin-activated platelets became incorporated into the Triton X-100-insoluble 10, 000g sedimentable residue in an aggregation-dependent manner, suggesting that it may have a regulatory role in platelet cytoskeletal processes during aggregation. Lastly, we found that WASP is cleaved in response to activation of calpain, a protease that may have a role in postaggregation signaling processes. Our data suggest that collagen specifically induces an increase in tyrosine phosphorylation of WASP and that WASP is involved in signaling during thrombin-induced aggregation by its redistribution to the cytoskeleton and its cleavage during aggregation.

Absence of expression of the Wiskott-Aldrich syndrome protein in peripheral blood cells of Wiskott-Aldrich syndrome patients

Wiskott-Aldrich syndrome (WAS) is an X-linked primary immunodeficiency that is usually associated with thrombocytopenia and eczema. The very variable phenotype of WAS results from defects in the WAS protein (WASP), the function of which is not well understood. In many cases causative mutations have now been identified in the WAS gene. Attempts have been made to correlate the nature of the mutations with the severity of the disease. In this study we investigated mutations in 13 patients with WAS and analyzed the expression of WASP in patient blood samples by immunoblot analysis. We found that despite extensive variation in the nature of the mutations in patients with severe WAS symptoms, none express the protein. However, in 1 patient with a mild clinical phenotype WASP expression was detected. Such an analysis could be used as an initial screening procedure for the diagnosis of WAS prior to genotypic analysis.

[Rare hyperimmunoglobulinemia E syndromes]

Total immunoglobulin E levels are very frequently measured, particularly for allergy. Their high levels are ordinarily found in atopy and parasitosis. This article subject is to determine rare diseases where high levels of total immunoglobulin E are found except in classic diseases. These rare hyper-immunoglobulin E syndromes are more often associated with immunologic deficiency more or less intense that lead to viral, fungal and bacterial infections. Buckley syndrome: deep infections due to Staphylococcus aureus, chronic dermatitis. Netherton disease: cutaneous and hair disease, allergic manifestations. Wiskott-Aldrich syndrome: thrombocytopeny and -pathy, dermatitis. Di-George disease: hypoparathyroidism, infections. Selective deficit of immunoglobulin A: recurrent infections. It is difficult to differentiate between atopic dermatitis and Buckley syndrome and Netherton disease because of eczematiform chronic dermatitis and high-levels of total immunoglobulin E found in all these diseases.

Autoimmune manifestations of the Wiskott-Aldrich syndrome

OBJECTIVE

To describe and review the autoimmune features and typical manifestations of Wiskott-Aldrich syndrome (WAS).

DESIGN

Case series and review of the literature.

SETTING

Tertiary care medical center and pediatric referral center.

PATIENTS

The presentation, diagnosis, and management of two cases are reported. In addition to the typical features of WAS, the first patient had hemolytic anemia, arthritis, leukocytoclastic vasculitis, and colitis. The second patient had colitis and arthralgias. Detailed review of features and therapeutic options in WAS as exemplified by these two patients are presented. Both patients had bone marrow transplantation, the only definitive treatment for WAS.

CONCLUSIONS

WAS has variable clinical and autoimmune manifestations. Diagnosis must be suspected in a boy with small, decreased number of platelets and autoimmune problems or infections. Bone marrow transplantation is the only successful mode of treatment for all aspects of WAS.

Defective actin reorganization and polymerization of Wiskott-Aldrich T cells in response to CD3-mediated stimulation

The Wiskott-Aldrich syndrome (WAS) is a severe immunodeficiency and platelet deficiency disease arising from mutation(s) in the WASP gene, which in normal cells encodes an intracellular protein able to interact with other proteins relevant to the control of cytoskeleton organization. Immunodeficiency is mainly due to T-cell progressive malfunction. Salient defects of WAS T cells are a CD3-restricted impairment in proliferative responses and cytoskeletal abnormalities, including the frequent appearance of T cells with atypical morphology. We have investigated the possibility that the CD3-restricted defect and some of the cytoskeletal defects of WAS T cells are linked. For this purpose, we immortalized by means of infection with Herpesvirus Saimiri a number of previously described allospecific WAS T-cell lines. The resulting cells preserve the surface, molecular, and functional phenotypes of their parental lines, including a negligible WASP mRNA expression as well as the CD3-restricted defect and cytoskeleton abnormalities. Results show that, in CD3-stimulated WAS T cells, the pattern of temporal changes in cell shape and F-actin distribution is substantially different from that of control cells. Furthermore, polymerization of actin, a critical step in the CD3-mediated cytoskeleton reorganization, does not occur in WAS T-cell lines in response to OKT3 stimulation. In conclusion, our data link both CD3 and cytoskeletal defects in WAS T cells, strongly suggesting that cytoskeleton abnormalities are an underlying cause for WAS immunodeficiency.

Flow cytometric analysis of platelets from children with the Wiskott-Aldrich syndrome reveals defects in platelet development, activation and structure

The pathophysiology of platelet dysfunction in the Wiskott-Aldrich immune deficiency syndrome (WAS) remains unclear. Using flow cytometry, we have characterized the functional properties of platelets from 10 children with WAS. Patients with WAS had thrombocytopenia, small platelets, increased platelet-associated IgG and reduced platelet-dense granule content. Levels of reticulated 'young' platelets were normal in the WAS patients. Although the mean numbers of platelet glycoprotein (GP) Ib, GPIIbIIIa and GPIV molecules per platelet appeared lower in WAS patients than in healthy controls, analysis of similar-sized platelets revealed the mean number of GPIb molecules per platelet to be comparable in patients and normal controls. Surface GPIIbIIIa and GPIV expression was, however, significantly lower on the WAS platelets than on normal platelets. Compared with normal platelets, WAS platelets showed a reduced ability to modulate GPIIbIIIa expression following thrombin stimulation. In addition, thrombin- and ADP-induced expression of CD62P and CD63 was defective in WAS platelets. Phallacidin staining of the WAS platelets revealed less F-actin content than in normal platelets. Together, these data suggest that the reduced platelet number and function in WAS reflects, at least in part, a defect in bone marrow production as well as an intrinsic platelet abnormality.

Epstein-Barr virus-associated malignant lymphoma with macroamylasemia and monoclonal gammopathy in a patient with Wiskott-Aldrich syndrome

A 1-year-old boy with Wiskott-Aldrich Syndrome (WAS) who developed malignant lymphoma is described. He showed various complications such as atypical lymphocytosis, disseminated intravascular coagulation (DIC), intracranial hemorrhage, macroamylasemia, and monoclonal gammopathy (immunoglobulin A kappa chain). Epstein-Barr virus (EBV) DNA was detected in the tumor tissue, and the monoclonality of B cells from the tumor tissue was established. EBV-associated lymphoma is frequently observed in immunocompromised patients including those with WAS. The development of macroamylasemia, which is rare in childhood, is discussed in relation to lymphoma and monoclonal gammopathy. This case is unique in that the EBV-associated malignant lymphoma developed at an early age and was accompanied by macroamylasemia.

Decreased alpha/beta heterodimer among CD8 molecules of peripheral blood T cells in Wiskott-Aldrich syndrome

Cell surface CD8 molecules exist as either alpha/alpha homodimers or alpha/beta heterodimers, and most CD8+ T cells that undergo differentiation in the thymus express alpha/beta heterodimers. CD8 molecules on peripheral blood lymphocytes of patients with Wiskott-Aldrich syndrome (WAS), an X-linked immunodeficiency disease, have now been shown to be composed mostly of alpha/alpha homodimers, while the total number of lymphocytes was maintained. This observation may indicate aberrant differentiation of CD8+ T cells in the thymus of WAS. Decreased CD8alpha/beta heterodimer expression, and the relative increase of CD8+ T cells expressing CD8alpha/alpha homodimer, may explain a part of the defective lymphocyte functions in WAS patients.