Wiskott-Aldrich Syndrome Protein Expression Research Articles

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

AIMTo screen primary immunodeficiency, Wiskott-Aldrich syndrome (WAS), and chronic granulomatous disease (CGD) among children with inflammatory bowel disease (IBD).METHODSThis 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.RESULTSEighteen 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.CONCLUSIONDespite the lack of typical clinical manifestations of WAS, low expression of WASP could be associated with the pathogenesis of a subtype of IBD patients.

BCR\u2013ABL1-induced downregulation of WASP in chronic myeloid leukemia involves epigenetic modification and contributes to malignancy

Chronic myeloid leukemia (CML) is a myeloproliferative disease caused by the BCR–ABL1 tyrosine kinase (TK). The development of TK inhibitors (TKIs) revolutionized the treatment of CML patients. However, TKIs are not effective to those at advanced phases when amplified BCR–ABL1 levels and increased genomic instability lead to secondary oncogenic modifications. Wiskott–Aldrich syndrome protein (WASP) is an important regulator of signaling transduction in hematopoietic cells and was shown to be an endogenous inhibitor of the c-ABL TK. Here, we show that the expression of WASP decreases with the progression of CML, inversely correlates with the expression of BCR–ABL1 and is particularly low in blast crisis. Enforced expression of BCR–ABL1 negatively regulates the expression of WASP. Decreased expression of WASP is partially due to DNA methylation of the proximal WASP promoter. Importantly, lower levels of WASP in CML advanced phase patients correlate with poorer overall survival (OS) and is associated with TKI response. Interestingly, enforced expression of WASP in BCR–ABL1-positive K562 cells increases the susceptibility to apoptosis induced by TRAIL or chemotherapeutic drugs and negatively modulates BCR–ABL1-induced tumorigenesis in vitro and in vivo. Taken together, our data reveal a novel molecular mechanism that operates in BCR–ABL1-induced tumorigenesis that can be used to develop new strategies to help TKI-resistant, CML patients in blast crisis (BC).

Intermittent low platelet counts hampering diagnosis of X-linked thrombocytopenia in children: report of two unrelated cases and a novel mutation in the gene coding for the Wiskott-Aldrich syndrome protein

BackgroundThrombocytopenia can occur in different circumstances during childhood and although immune thrombocytopenia is its most frequent cause, it is important to consider other conditions, especially when there is a persistent or recurrent low platelet count. We report two cases of intermittent thrombocytopenia, previously misdiagnosed as immune thrombocytopenia.Cases presentationBoth cases described were boys who presented with an intermittent pattern of thrombocytopenia, with a persistently low mean platelet volume. In both patients, peripheral blood smear revealed small platelets and flow cytometry showed low expression of Wiskott-Aldrich syndrome protein (WASP) in leucocytes. Molecular analysis of the first case identified a mutation in exon 2 of the gene coding for WASP, leading to a p.Thr45Met amino acid change and confirming the diagnosis of X-linked thrombocytopenia. In the second case, a novel missense mutation in exon 2 of the gene coding for WASP was detected, which resulted in a p.Pro58Leu amino acid change.ConclusionThese two rare presentations of thrombocytopenia highlight the importance of evaluating the peripheral blood smear in the presence of recurrent or persistent thrombocytopenia and show that failing to do so can lead to misdiagnoses. Since thrombocytopenia may be found in pediatric outpatient clinic, increased awareness among general pediatricians will help to improve the differential diagnosis of this condition.

B cell-Intrinsic Defects of Wiskott-Aldrich Syndrome Protein-Deficiency in generating humoral memory responses

Abstract Patients with Wiskott-Aldrich syndrome protein (WASP)-deficiency exhibit severe immunodeficiency, including a lack of long-lasting humoral protection. Our published data reveal that T follicular helper cells in both WAS patients and WASP-deficient mice are impaired. This study demonstrates a B cell-intrinsic role of WASP in generating antigen-specific memory B cells and humoral recall responses. While the serum IgG levels in patients with WAS are equivalent to those in age-matched healthy controls, the number and percentage of isotype-switched CD27+ memory B cells and the serum level of tetanus toxin-specific IgG post immunization in the patients are significantly lower than those in controls. Furthermore, the peripheral blood of the patients exhibits a substantial increase in atypical memory B cells that resemble B cells expanded in persistent viral and parasite infections. In immunized WASP knockout mice, the percentages of antigen-specific germinal center, isotype-switched memory B cells, and plasmablasts in the spleen all are decreased, while the percentages of total germinal center B cells and plasmablasts are unchanged, compared to wild-type mice. In bone marrow chimera mice, where only B cells lack WASP expression, WASP-deficient B cells show reductions in the antigen-specific germinal center and memory subsets similar to those seen in WASP knockout mice. However, the percentages of total germinal center and isotype-switched B cells in the WASP knockout chimera mice are equivalent to or higher than those in the wild-type chimera. These results indicate that WASP-deficient B cells play a critical and cell-intrinsic role in developing the humoral immune deficiency in WAS.

Safe and Effective Gene Therapy for Murine Wiskott-Aldrich Syndrome Using an Insulated Lentiviral Vector

Wiskott-Aldrich syndrome (WAS) is a life-threatening immunodeficiency caused by mutations within the WAS gene. Viral gene therapy to restore WAS protein (WASp) expression in hematopoietic cells of patients with WAS has the potential to improve outcomes relative to the current standard of care, allogeneic bone marrow transplantation. However, the development of viral vectors that are both safe and effective has been problematic. While use of viral transcriptional promoters may increase the risk of insertional mutagenesis, cellular promoters may not achieve WASp expression levels necessary for optimal therapeutic effect. Here we evaluate a self-inactivating (SIN) lentiviral vector combining a chromatin insulator upstream of a viral MND (MPSV LTR, NCR deleted, dl587 PBS) promoter driving WASp expression. Used as a gene therapeutic in Was−/− mice, this vector resulted in stable WASp+ cells in all hematopoietic lineages and rescue of T and B cell defects with a low number of viral integrations per cell, without evidence of insertional mutagenesis in serial bone marrow transplants. In a gene transfer experiment in non-human primates, the insulated MND promoter (driving GFP expression) demonstrated long-term polyclonal engraftment of GFP+ cells. These observations demonstrate that the insulated MND promoter safely and efficiently reconstitutes clinically effective WASp expression and should be considered for future WAS therapy.

Hematopoietic stem cell transplantation corrects WIP deficiency

Hematopoietic stem cell transplantation corrects WIP deficiency

FOXP3+ Tregs require WASP to restrain Th2-mediated food allergy

In addition to the infectious consequences of immunodeficiency, patients with Wiskott-Aldrich syndrome (WAS) often suffer from poorly understood exaggerated immune responses that result in autoimmunity and elevated levels of serum IgE. Here, we have shown that WAS patients and mice deficient in WAS protein (WASP) frequently develop IgE-mediated reactions to common food allergens. WASP-deficient animals displayed an adjuvant-free IgE-sensitization to chow antigens that was most pronounced for wheat and soy and occurred under specific pathogen-free as well as germ-free housing conditions. Conditional deletion of Was in FOXP3+ Tregs resulted in more severe Th2-type intestinal inflammation than that observed in mice with global WASP deficiency, indicating that allergic responses to food allergens are dependent upon loss of WASP expression in this immune compartment. While WASP-deficient Tregs efficiently contained Th1- and Th17-type effector differentiation in vivo, they failed to restrain Th2 effector responses that drive allergic intestinal inflammation. Loss of WASP was phenotypically associated with increased GATA3 expression in effector memory FOXP3+ Tregs, but not in naive-like FOXP3+ Tregs, an effect that occurred independently of increased IL-4 signaling. Our results reveal a Treg-specific role for WASP that is required for prevention of Th2 effector cell differentiation and allergic sensitization to dietary antigens.

A novel genomic inversion in Wiskott-Aldrich–associated autoinflammation

A novel genomic inversion in Wiskott-Aldrich–associated autoinflammation

B Cell Reconstitution after Gene Therapy in Patients with Wiskott Aldrich Syndrome and Comparison with Mismatched Allogeneic Hematopoietic Stem Cell Transplantation

Background. Wiskott Aldrich Syndrome (WAS) is a rare primary immunodeficiency associated with thrombocytopenia, eczema, severe infectious and autoimmune complications, and lymphomas. Mismatched allogeneic hematopoietic stem cell transplantation (HSCT) is an alternative for patient lacking an HLA-matched donor but is associated with an increased frequency of complications. Moreover low lymphoid and myeloid chimerism is related to a higher rate of autoimmunity and thrombocytopenia. Recent gene therapy (GT) trials showed that gene-corrected autologous CD34+ cells infusion could be an appropriate therapeutic approach for these patients. It has been recently shown that B cell homeostasis is altered in WAS. As the B cell reconstitution participates to the restoration of immunological competence, a comprehensive study of this compartment after GT and the comparison with mismatched allogeneic HSCT is crucial.Objective. To perform a longitudinal study of B cell reconstitution in WAS patients after lentiviral vector-mediated GT, compared to mismatched allogeneic HSCT.Methods. Five patients (age 0.8-15.5 years) underwent GT at our center since 2011(follow-up 1.5-4.2 years) after near-myeloablative and immunosuppressive conditioning regimen with (n=3) or without (n=2) anti-CD20 administration. Patient 2 (P2) died 7 months after GT from a pre-existing infectious complication. Eleven patients undergoing mismatched allogeneic HSCT (age 0.6-10.9 years) at the same center were studied (follow-up 5.1-14.7 years). Longitudinal B cell assessment included B cell count before and after treatment, and the following subsets: switched memory (SM, CD19+ CD27+ IgD-), marginal zone (MZ, CD19+ CD27+ IgD+), naives (CD19+ CD27- IgD+), transitional (CD19+ CD27- IgD+ CD24high CD38high), circulating plasma cells (CD19+ CD27+ IgD- CD27high CD38high) and CD21low B cells (CD19+ CD21low CD38-), a subset abnormally expanded in WAS. Quantification of the B cell replication history was assessed through k-deleting recombination excision circles (KRECs). Analyses were compared to age-matched controls. WAS protein (WASP) expression and vector copy number (VCN) were measured in sorted B cells.Results. All alive GT patients show stable engraftment of functionally corrected lymphoid cells, without adverse events. Transduced B cells number and WASP expression increased progressively after GT. Absolute B cell count attained normal values in all the patients, and correlates with WASP expression and VCN in B cells. IgM levels are below normal ranges in four patients. P3 and P4 attained a B-cell phenotype within normal ranges; P3 discontinued intravenous immunoglobulin (IvIg) replacement. No expansion of CD21low B cells was observed. P1 and P5 (follow-up 18 months) present a variable defect in SM, naives and/or MZ B cells. P1 recently developed autoimmune manifestations; no significant changes were observed concomitantly. A defect in B cell lymphopoiesis was observed before GT as measured by KRECs analysis, normalizing after GT (P1, P3 and P4). Several complications were recorded in patients undergoing mismatched allogeneic HSCT, including dysimmunity, arthritis, developmental deficit and infections. Total B cell count normalized in eight patients, IgM levels were low in three. Among patients with available information, four still remain under IvIg replacement. Four patients developed a mixed lymphoid and myeloid chimerism, variably associated with low B cell count, low IgM and IvIg replacement. A complete B cell assessment for these patients is ongoing.Conclusions. B cell transgene expression is obtained after lentiviral vector-mediated GT in WAS patients and is associated with improved B cell lymphopoiesis. A correct B cell phenotype is observed in two patients who did not receive rituximab prior GT. The question whether this is related to the treatment will need a longer follow-up to be answered. Patients undergoing mismatched allogeneic HSCT present a higher frequency of complications. Although a higher proportion of these patients discontinued IvIg replacement, B cell reconstitution is not optimal. Analysis of patients in particular with mixed chimerism will provide important information in the setting of GT. The analysis of B cell reconstitution after GT and mismatched allogeneic HSCT deserves particular attention in the assessment of immunological reconstitution. DisclosuresNo relevant conflicts of interest to declare.

Gene Therapy Using a Self-Inactivating Lentiviral Vector Improves Clinical and Laboratory Manifestations of Wiskott-Aldrich Syndrome

The X-linked disorder Wiskott-Aldrich Syndrome (WAS), characterized by thrombocytopenia, eczema, recurrent infections, autoimmunity and cancer, is typically treated with allogeneic transplantation. Somatic gene therapy (GT) using autologous CD34+ cells is a promising treatment alternative for high-risk patients lacking matched allogeneic donors, as it avoids graft versus host disease. GT using a γ-retroviral vector with intact viral enhancers was efficacious but had a high rate of leukemia due to insertional oncogenesis. We report here preliminary results of 4 WAS patients who underwent GT using a self-inactivating lentiviral (SIN-LV) vector, in which viral enhancers have been deleted and the human WAS cDNA is controlled by a 1.6kB fragment of the human WAS promoter (w1.6_hWASP_WPRE SIN-LV). WASP expression per cell induced by this vector was lower than in normal cells when examined in murine models and human trials. We hypothesized that the SIN-LV would readily correct immune abnormalities due to selective advantage for WAS protein (WASP) expressing T cells whereas correction of myeloid and platelet abnormalities would require high vector copy number (VCN) in the infused cells.Patients with severe WAS (clinical scores 3-5) were enrolled at a median age of 32 months (17 months-8 years). Patients 1 and 3 had detectable but low WASP expression. Patients 2 and 4 carried mutations that abrogated WASP expression but had evidence of somatic reversion in T and/or NK cells. CliniMACS purified CD34+ mobilized peripheral blood or bone marrow cells were transduced with the vector and infused after busulfan (12-15mg/kg) and fludarabine (120mg/m2) conditioning. CD34+ cell doses ranged from 6.3-24.91 x 106 cells/kg. VCN of the infused cells was variable (3.37, 1.34, 0.54, 1.01 copies/cell). Busulfan exposure was myeloablative or near-myeloablative in patients 1, 3, and 4 (81.2, 77.2, 84.5 mg*h/L) and submyeloablative in patient 2 (48.8 mg*h/L).All patients are alive with median follow-up of 13.5 months (9-24 months). All patients had improvement in eczema, remain platelet transfusion independent and have had no severe bleeding events. WASP expression in T cells was increased post-GT over baseline. Selective advantage for WASP expressing T cells was apparent in patients 1, 2 and 4, who had higher VCN in T cells at 6 months post-GT (0.93-2.21) than in B (0.48-1.7) or myeloid (0.13-0.89) cells. The presence of revertants in patients 2 and 4 did not appear to interfere with T cell reconstitution. In contrast patient 3 who had the highest WASP expression at baseline and the lowest VCN of infused cells (0.5 copies/cell), had the lowest VCN in T cells at 8 months (0.1 copies/cell). Defective T cell proliferation in response to anti-CD3 stimulation, characteristic of WAS, was improved post-GT. Next generation sequencing of T cell receptors in sorted naïve, memory and regulatory T cells revealed profound abnormalities of diversity, decreased entropy and marked clonal expansions pre-GT; most of these improved at 6 months post-GT. Cytoskeletal function in myeloid cells was highly abnormal pre-GT, as shown by absence of podosome formation in monocyte-derived dendritic cells (0-1% vs. 61% in controls). Podosome formation at 6 months post GT was improved but subnormal (4-40%). Only patient 1, who received the highest cell dose, the highest VCN, and myeloablative busulfan exposure had robust platelet reconstitution (pre-GT 24 versus 110 x 109/L 6 months post-GT) and high level gene marking in myeloid cells 0.89 copies/cell. At the same timepoint, patients 2, 3 and 4 had platelet counts of 20-30 x 109/L and correspondingly lower VCN in myeloid cells (0.13-0.27 copies/cell).No severe adverse events related to GT have occurred to date, with relatively short follow-up. Integration site analysis of sorted cells showed highly polyclonal reconstitution, with distributions of integration acceptor sites as expected for the lentiviral vector backbone. In summary, GT using a SIN-LV that induces expression of WASP at levels below wild type improved the clinical and laboratory manifestations of WAS, with better reconstitution in patients receiving cells with high VCN. DisclosuresOff Label Use: Off-label use of CliniMACS purified CD34+ cells.

Safety and Clinical Benefit of Lentiviral Hematopoietic Stem Cell Gene Therapy for Wiskott-Aldrich Syndrome

Wiskott-Aldrich Syndrome (WAS) is an X-linked primary immunodeficiency characterized by thrombocytopenia, recurrent infections, eczema, autoimmunity and increased susceptibility to malignancies. Allogeneic hematopoietic stem cell transplantation (HSCT) is a recognized curative treatment for WAS, but is still associated with transplant-related complications and long-term morbidity, particularly in the absence of fully matched donors. In April 2010, we initiated a phase I/II clinical trial with hematopoietic stem cell (HSC) gene therapy (GT) for WAS. The investigational medicinal product (IMP) consists of autologous CD34+ HSC engineered with a lentiviral vector (LV) driving the expression of WAS cDNA from an endogenous 1.6 kb human WAS promoter (LV-WAS), infused after a reduced intensity conditioning (RIC) based on anti-CD20 mAb, targeted busulfan and fludarabine. We previously reported early follow up (FU) results from the first 3 patients (Aiuti et al., Science 2013). Seven patients (Zhu score ≥3) have now been treated at a median age of 1.9 years (1.1 - 11.1). As of May 2015, all patients are alive with a median FU of 3.2 years (0.7 - 5.0). CD34+ cell source was bone marrow (BM) (n=5), mobilized peripheral blood (MPB) (n=1) or both (n=1). IMP dose ranged between 7.0 and 14.1 x106 CD34+/kg, containing on average 94.4 ± 3.5% transduced clonogenic progenitors and a mean vector copy number (VCN)/genome in bulk CD34+ cells of 2.7 ± 0.8. No adverse reactions were observed after IMP infusion and RIC was well tolerated. Median duration of severe neutropenia was 19 days; granulocyte-colony stimulating factor was administered to 1 patient.In the first 6 treated patients with FU >2 years, we observed robust and persistent engraftment of gene corrected cells. At the most recent FU, transduced BM progenitors ranged between 20.7 and 59.7%, and LV-transduced cells were detected in multiple lineages, including PB granulocytes (VCN 0.34 - 0.93) and lymphocytes (VCN 1.18 - 2.73). WAS protein expression, measured by flow-cytometry, was detected in the majority of PB platelets [mean ± standard deviation (SD), 71.4 ± 14.0%], monocytes (63.3 ± 18.5%) and lymphocytes (78.9 ± 14.9%). Lymphocyte subset counts were normal in most patients and proliferative response to anti-CD3 mAb was in the normal range in all 6 patients.After immune reconstitution, a marked reduction in the annualized estimated rate of severe infections was observed, as compared with baseline (figure 1A). The first 6 treated patients discontinued anti-infective prophylaxis and no longer require a protected environment. Four patients stopped immunoglobulin supplementation and 2 of them developed specific antibodies after vaccination. Eczema resolved in 4 patients and remains mild in 2. No clinical manifestations of autoimmunity were observed ≥1 year after GT in accordance with improved B-cell development and decreased autoantibody production. All patients became platelet transfusion independent at a median of 4 months after GT (range: 1.0 - 8.7). Mean platelet counts progressively increased after treatment (mean ± SD: before GT, 13.4 ± 7.8 x109/l; 24-30 month FU, 45.8 ± 22.0 x109/l; 36-42 month FU, 57.0 ± 18.7 x109/l).The frequency and the severity of bleeding events decreased after the 1st year of FU. No severe bleedings were recorded after treatment (figure 1B).Quality of life improved in all patients after GT. From the 2nd year of FU, the number of hospitalizations for infections decreased and no hospitalizations due to bleeding were observed after treatment.The seventh patient treated, who received MPB derived CD34+ cells only, showed the fastest platelet recovery with the highest level of transduced myeloid cell engraftment, and is clinically well.No Serious Adverse Events (SAE) related to the IMP were observed. The most frequent SAE were related to infections (85%), occuring mainly during the 1st year of FU.Importantly, no evidence of abnormal clonal proliferations emerged after GT and the LV integration profile show a polyclonal pattern, with no skewing for proto-oncogenes.In conclusion, this updated report in 7 WAS patients show that GT is well tolerated and leads to a sustained clinical benefit. The high level of gene transfer obtained with LV-WAS results in robust engraftment of transduced HSC, even when combined with RIC. Prolonged FU will provide additional information on the long-term safety and clinical efficacy of this treatment. [Display omitted] DisclosuresVilla:Fondazione Telethon: Research Funding. Dott:GlaxoSmithKline: Consultancy. van Rossem:GlaxoSmithKline: Employment. Naldini:Salk Institute: Patents & Royalties: Lentiviral vectors; San Raffaele Telethon Institute: Patents & Royalties: Lentiviral vector technology; GlaxoSmithKline: Other: GSK licensed gene therapies developed at my Institute and the Institute receives milestone payments; Sangamo Biosciences: Research Funding; Biogen: Research Funding; Genenta Sciences: Equity Ownership, Membership on an entity's Board of Directors or advisory committees. Aiuti:GlaxoSmithKline (GSK): Other: PI of clinical trial which is financially sponsored by GSK; Fondazione Telethon: Research Funding.

289. Safe and Effective Gene Therapy for Wiskott – Aldrich Syndrome Using an Insulated Lentiviral Vector

Wiskott–Aldrich Syndrome (WAS) is a severe X-linked immunodeficiency disorder characterized by recurrent infection, thrombocytopenia, and autoimmunity resulting from mutations within the WAS gene. The encoded gene product, WAS protein (WASp), is a scaffold protein important for activation of the actin cytoskeleton downstream of multiple hematopoietic receptors. Development of safe and effective hematopoietic stem cell (HSC) gene therapy for WAS would provide a valuable treatment alternative to allogeneic bone marrow transplantation. Of critical importance for such an approach is the capacity to achieve sufficient WASp expression in relevant lineages to correct the multiple deficits, while avoiding development of autoimmune disease. We previously tested a panel of self-inactivating (SIN) lentiviral (LV) vectors expressing human WAS via alternative internal promoters and observed optimal expression and rescue using the modified γ-retroviral derived LTR, MND. To improve the potential safety and stability of expression, we incorporated a 650bp chimeric insulator from the chicken β-globin locus into this LV. Using in vitro assays the insulated LV exhibited minimal LMO2 transactivation and no evidence for immortalization of cultured HSC. Next, we generated a stable high-titer producer clone expressing this candidate clinical LV, CL20-i650–MND-WAS. Here, we evaluate the efficacy and safety of the insulted vs uninsulated LV (CL20-MND-WAS) in a large cohort of primary and secondary transplanted Was/- mice. Both vectors enabled stable engraftment of WASp expressing cells in all hematopoietic lineages, positive selection of WASp+ cells, and rescued functional and developmental T and B cell defects without evidence for toxicity. Inclusion of the insulator allowed for higher expression levels at lower numbers of viral integration per cell; a feature that was further exaggerated in secondary recipients. Finally, in parallel, we evaluated CL20-i650–MND LV expressing a fluorescent marker using CD34+ autologous HSC transplants in a non-human primate model (Macaca nemestrina) and observed long term stable polyclonal engraftment of LV expressing hematopoietic cells for up to 2 yr. Based on these extensive pre-clinical and toxicity studies we anticipate that CL20-i650–MND-WAS LV will provide sustained rescue of platelet and lymphocyte development and function in vivo (facilitated, in part, via the insulator) without evidence of toxicity. We plan to directly test this hypothesis in an upcoming WAS LV clinical trial.

In vivo reversion of an inherited mutation in a Chinese patient with Wiskott–Aldrich syndrome

A spontaneous reversion that restores Wiskott–Aldrich syndrome protein (WASP) expression was reported recently. However, the genetic mechanism underlying the reversion event was unclear. In the present study, a WAS patient with a nonsense mutation (155 C>T, R41X) was followed during a three-year period. No expression of WASP was detected in peripheral blood mononucleated cells (PBMCs) in 2009 and a small population of intracellular WASP positive lymphocytes was detected during the following three years. The increasing trend of the revertant genotype was significant. WASP-expressing cells were present mainly CD56+ NK cells and CD8+ T cells. Sorted WASP+ cells were analyzed, indicating that the population of CD3+ T cells increased from 36.81% to 99.8%. Although the revertant cells in vivo may have a growth advantage, the patient presented a persistent autoimmune disease, thrombocytopenia, and died from extensive pulmonary fibrosis. The results suggest that the clinical consequences of T-cell mosaicism in WAS remain difficult to predict and is not sufficient to fully normalize immune functions in patients with WAS.

B-cell reconstitution after lentiviral vector–mediated gene therapy in patients with Wiskott-Aldrich syndrome

BackgroundWiskott-Aldrich syndrome (WAS) is a severe X-linked immunodeficiency characterized by microthrombocytopenia, eczema, recurrent infections, and susceptibility to autoimmunity and lymphomas. Hematopoietic stem cell transplantation is the treatment of choice; however, administration of WAS gene–corrected autologous hematopoietic stem cells has been demonstrated as a feasible alternative therapeutic approach.ObjectiveBecause B-cell homeostasis is perturbed in patients with WAS and restoration of immune competence is one of the main therapeutic goals, we have evaluated reconstitution of the B-cell compartment in 4 patients who received autologous hematopoietic stem cells transduced with lentiviral vector after a reduced-intensity conditioning regimen combined with anti-CD20 administration.MethodsWe evaluated B-cell counts, B-cell subset distribution, B cell–activating factor and immunoglobulin levels, and autoantibody production before and after gene therapy (GT). WAS gene transfer in B cells was assessed by measuring vector copy numbers and expression of Wiskott-Aldrich syndrome protein.ResultsAfter lentiviral vector-mediated GT, the number of transduced B cells progressively increased in the peripheral blood of all patients. Lentiviral vector-transduced progenitor cells were able to repopulate the B-cell compartment with a normal distribution of B-cell subsets both in bone marrow and the periphery, showing a WAS protein expression profile similar to that of healthy donors. In addition, after GT, we observed a normalized frequency of autoimmune-associated CD19+CD21−CD35− and CD21low B cells and a reduction in B cell–activating factor levels. Immunoglobulin serum levels and autoantibody production improved in all treated patients.ConclusionsWe provide evidence that lentiviral vector-mediated GT induces transgene expression in the B-cell compartment, resulting in ameliorated B-cell development and functionality and contributing to immunologic improvement in patients with WAS.

Generation of a lentiviral vector producer cell clone for human Wiskott-Aldrich syndrome gene therapy

We have developed a producer cell line that generates lentiviral vector particles of high titer. The vector encodes the Wiskott-Aldrich syndrome (WAS) protein. An insulator element has been added to the long terminal repeats of the integrated vector to limit proto-oncogene activation. The vector provides high-level, stable expression of WAS protein in transduced murine and human hematopoietic cells. We have also developed a monoclonal antibody specific for intracellular WAS protein. This antibody has been used to monitor expression in blood and bone marrow cells after transfer into lineage negative bone marrow cells from WAS mice and in a WAS negative human B-cell line. Persistent expression of the transgene has been observed in transduced murine cells 12–20 weeks following transplantation. The producer cell line and the specific monoclonal antibody will facilitate the development of a clinical protocol for gene transfer into WAS protein deficient stem cells.

Clinical characteristics and treatment responses of X-linked thrombocytopenia

To analyze the clinical and molecular characteristics of patients with X-linked thrombocytopenia (XLT) and their responsiveness to treatment with various doses of corticosteroids or intravenous immunoglobulin (IVIG) separately. Data from 15 XLT patients who were hospitalized in Children's Hospital Affiliated to Chongqing Medical University from March 2010 to July 2014 were analyzed retrospectively, including clinical manifestations, scores, peripheral blood, immunological functions, responses to IVIG and steroid treatment with various doses and duration. All 15 XLT patients met the inclusion criteria and showed microthrombocytopenia with or without mild-to-moderate eczema or minor infections. Platelet counts ranged from (8-80) × 10⁹/L. The platelet volume value ranged between 5.6 and 10.9 fl (normal range: 9.4-12.5 fl). Raised serum IgG was found in 5 cases, while low serum IgG was found in 2 cases. WAS gene analysis revealed missense mutations in 14 patients, including 4 hotspots (V75M, R86C, R86H, R86L) and 1 novel mutation (Y107C). Flow cytometer analysis of 13 patients showed various amounts of WAS protein (WASP) expression, 2 patients had normal amounts of WASP expression, 5 had reduced amounts, and 6 had absent WASP expression. Their responses to individual steroid and IVIG treatment with various doses and duration were also reviewed. Fourteen patients who were misdiagnosed as immune thrombocytopenic purpura at first received 28 courses of steroids and (or) 47 courses of IVIG treatment. The post-treatment platelet counts of 1 000-2 000 mg/(kg × d) IVIG(25 courses) at 2-7 d and 8-14 d time points were (60 ± 10) × 10⁹/L and (41 ± 7) × 10⁹/L, which indicate a significantly better responsiveness than those by [(31 ± 7) × 10⁹/L, (21 ± 2) × 10⁹/L] of 400-500 mg/(kg·d) IVIG(22 courses) (Z = -4.419, -1.592;P = 0.002,0.011). However, there were no significant differences between the responsiveness of 3 doses [1-2 mg/(kg·d)(8 courses), 3-6 mg/(kg·d) (11 courses) and 20-30 mg/(kg × d)(9 courses)] of steroids (F = 0.387,0.252;P = 0.980,0.761) at 2-7 d and 8-14 d time points. The platelet counts gradually decreased to the primary level at 15-30 d after any doses of steroids and (or) IVIG treatment. The effective rate of 1 000-2 000 mg/(kg × d) IVIG treatment was 18/25, which was significantly higher than that (2/22) of 400-500 mg/(kg × d) (χ² = 9.836, P = 0.008). The effective rate of 20-30 mg/(kg × d) steroids treatment (7/9) was relatively higher than 1-2 mg/(kg × d) (4/8) and 3-6 mg/(kg × d) (6/11) with no significant difference (χ⁹ = 3.235, P = 0.581). After the treatment with steroids and /or IVIG 14 cases with hemorrhage were all improved. The clinical characteristics of X-linked thrombocytopenia were microthrombocytopenia with or without mild-to-moderate eczema or minor infections. WAS gene and WASP analysis were diagnostic methods. There were no significant differences between the responsiveness of 3 doses of steroids; 1 000-2 000 mg/(kg·d) IVIG had a significantly better responsiveness. However, IVIG and steroids with any dose and duration may only transiently increase peripheral platelet level of XLT patients.

Lentiviral hematopoietic stem cell gene therapy in patients with wiskott-Aldrich syndrome.

A Aiuti, L Biasco, S Scaramuzza. Science. 2013;341(6148):1233151 The goal of this study was to develop a clinical protocol for Wiskott-Aldrich syndrome (WAS) by using a lentiviral vector (LV) to introduce a functional WAS gene into hematopoietic stem and progenitor cells (HSPCs) for autologous transplantation. Three patients who had WAS with a severe clinical condition or severe mutation/absent WAS protein expression without a suitable matched donor for allogeneic transplant or ineligible for HSPC transplantation were enrolled. Patients were pretreated with a reduced-intensity myeloablative regimen. Afterward, they received autologous HSPCs that were transduced …

T-cell receptor diversity is selectively skewed in T-cell populations of patients with Wiskott-Aldrich syndrome

Wiskott-Aldrich syndrome (WAS) is a severe disorder characterized by thrombocytopenia, eczema, immunodeficiency, and increased risk of autoimmune disease and lymphoid malignancies. The immunodeficiency caused by a lack of WAS protein expression has been mainly attributed to defective T-cell functions. Whether WAS mutations differentially influence the T-cell receptor (TCR) diversity of different T-cell subsets is unknown. We aimed to identify the degree and pattern of skewing in the variable region of the TCR β-chain (Vβ) in different T-cell subsets from patients with WAS. The TCR repertoire diversity in total peripheral Tcells, sorted CD4(+) and CD8(+) T cells, and CD45RA(+) (CD45RA(+)CD45RO(-) cells) and CD45RO(+) (CD45RA(-)CD45RO(+) cells) CD4(+) and CD8(+) T cells from patients with WAS and age-matched healthy control subjects was analyzed and compared by using spectratyping of complementarity-determining region 3. The complementarity-determining region 3 of TCRβ transcripts in CD45RA(+)CD4(+) and CD45RA(+)CD8(+) T cells, CD45RO(+)CD4(+) T cells, CD8(+) terminally differentiated effector memory T (Temra) cells, and naive CD8(+) T cells (CD8(+)CD45RO(-)CCR7(+) cells) from patients and control subjects were analyzed and compared by using high-throughput sequencing. The TCR repertoire diversity in CD45RO(+)CD4(+) T cells and CD8(+) Temra cells of patients with WAS was significantly skewed in comparison with that seen in age-matched control subjects. Our results indicate that WAS gene mutations selectively influence TCR repertoire development or expansion in CD45RO(+) (memory) CD4(+) T cells.

NK/DC crosstalk in immunosurveillance: a broken relationship caused by WASP-deficiency.

Wiskott-Aldrich syndrome (WAS) is a primary immunodeficiency, which is characterized by abnormal immune system functions caused by the lack of expression of WAS protein (WASp). A higher tumor susceptibility is observed in WAS patients; whether this is a direct consequence of impaired immunosurveillance due to WAS deficiency in immune cells is, however, an open question. In this issue of the European Journal of Immunology, Catucci et al. [Eur. J. Immunol. 2014. 44: 1039-1045] shed light on the link between Was deficiency and immunosurveillance in a tumor-prone mouse model and report a role for the impaired crosstalk between natural killer (NK) cells and dendritic cells (DCs) in mediating this process. The potential mechanisms involved in WASp regulation of NK/DC-mediated immunosurveillance are the focus of this Commentary.

Development of Central Nervous System Autoimmunity Is Impaired in the Absence of Wiskott-Aldrich Syndrome Protein

Wiskott-Aldrich Syndrome protein (WASP) is a key regulator of the actin cytoskeleton in hematopoietic cells. Defective expression of WASP leads to multiple abnormalities in different hematopoietic cells. Despite severe impairment of T cell function, WAS patients exhibit a high prevalence of autoimmune disorders. We attempted to induce EAE, an animal model of organ-specific autoimmunity affecting the CNS that mimics human MS, in Was−/− mice. We describe here that Was−/− mice are markedly resistant against EAE, showing lower incidence and milder score, reduced CNS inflammation and demyelination as compared to WT mice. Microglia was only poorly activated in Was−/− mice. Antigen-induced T-cell proliferation, Th-1 and -17 cytokine production and integrin-dependent adhesion were increased in Was−/− mice. However, adoptive transfer of MOG-activated T cells from Was−/− mice in WT mice failed to induce EAE. Was−/− mice were resistant against EAE also when induced by adoptive transfer of MOG-activated T cells from WT mice. Was+/− heterozygous mice developed an intermediate clinical phenotype between WT and Was−/− mice, and they displayed a mixed population of WASP-positive and -negative T cells in the periphery but not in their CNS parenchyma, where the large majority of inflammatory cells expressed WASP. In conclusion, in absence of WASP, T-cell responses against a CNS autoantigen are increased, but the ability of autoreactive T cells to induce CNS autoimmunity is impaired, most probably because of an inefficient T-cell transmigration into the CNS and defective CNS resident microglial function.