Search

FOXP3 is the transcription factor ruling regulatory T cell function and maintenance of peripheral immune tolerance, and mutations in its coding gene causes IPEX autoimmune syndrome. FOXP3 is also a cell-cycle inhibitor and onco-suppressor in different cell types. In this work, we investigate the effect of ectopic FOXP3 expression on HSC differentiation and we challenged this approach as a possible HSC-based gene therapy for IPEX. FOXP3-expressing HSC showed reduced proliferation ability and increased maintenance of primitive markers in vitro in both liquid and OP9-ΔL1 co-cultures. When transplanted into immunodeficient mice, FOXP3-expressing HSC showed significantly enhanced engraftment ability. This was due to a pronounced increase in the frequency of repopulating cells, as assessed by extreme limiting dilution assay. Likely underlying the increased repopulating ability, FOXP3 expressing HSC showed significantly enhanced expression of genes controlling stemness features. However, peripheral T cells developed in the FOXP3-humanized mice were quantitatively reduced and hyporesponsive to cytokine and polyclonal stimulation. Our findings reveal unpredicted effects of FOXP3 in the biology of HSC and may provide new tools to manipulate primitive features in HSC for clinical applications. Moreover, they formally prove the need of preserving endogenous FOXP3 regulation for an HSC-based gene therapy approach for IPEX syndrome.

Gene correction in human long-term hematopoietic stem cells (LT-HSCs) could be an effective therapy for monogenic diseases of the blood and immune system. Here we describe an approach for X-linked sSevere cCombined iImmunodeficiency (SCID-X1) using targeted integration of a cDNA into the endogenous start codon to functionally correct disease-causing mutations throughout the gene. Using a CRISPR-Cas9/AAV6 based strategy, we achieve up to 20% targeted integration frequencies in LT-HSCs. As measures of the lack of toxicity we observe no evidence of abnormal hematopoiesis following transplantation and no evidence of off-target mutations using a high-fidelity Cas9 as a ribonucleoprotein complex. We achieve high levels of targeting frequencies (median 45%) in CD34+ HSPCs from six SCID-X1 patients and demonstrate rescue of lymphopoietic defect in a patient derived HSPC population in vitro and in vivo. In sum, our study provides specificity, toxicity and efficacy data supportive of clinical development of genome editing to treat SCID-Xl., Gene correction in hematopoietic stem cells could be a powerful way to treat monogenic diseases of the blood and immune system. Here the authors develop a strategy using CRISPR-Cas9 and an aAdeno-Associated vVirus(AAV)-delivered IL2RG cDNA to correct X-linked sSevere Ccombined iImmunodeficiency (SCID-X1) with a high success rate.

Summary Immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome is a devastating autoimmune disease caused by mutations in FoxP3, a transcription factor required for the development and function of regulatory T cells (Treg cells). Allogeneic hematopoietic stem cell transplant (HSCT) can be curative, but suitable donors are often unavailable. Here, we demonstrate a strategy for autologous HSCT and gene therapy utilizing a lentiviral vector (LV) to restore FoxP3 expression under the control of endogenous human FOXP3 regulatory elements. Both murine transplant models and humanized mice engrafted with LV-modified HSCs show high levels of LV expression selective for CD4+CD25+FoxP3+ Treg cells. LV transduction of scurfy (FoxP3mut) HSCs restores development of functional FoxP3+ Treg cells that suppress T cell proliferation in vitro and rescue the scurfy autoimmune phenotype in vivo. These findings demonstrate preclinical efficacy for the treatment of IPEX patients by autologous HSC transplant and may provide valuable insights into new cell therapies for autoimmunity.

CD4+ type 1 T regulatory (Tr1) cells are induced in the periphery and have a pivotal role in promoting and maintaining tolerance. The absence of surface markers that uniquely identify Tr1 cells has limited their study and clinical applications. By gene expression profiling of human Tr1 cell clones, we identified the surface markers CD49b and lymphocyte activation gene 3 (LAG-3) as being stably and selectively coexpressed on mouse and human Tr1 cells. We showed the specificity of these markers in mouse models of intestinal inflammation and helminth infection and in the peripheral blood of healthy volunteers. The coexpression of CD49b and LAG-3 enables the isolation of highly suppressive human Tr1 cells from in vitro anergized cultures and allows the tracking of Tr1 cells in the peripheral blood of subjects who developed tolerance after allogeneic hematopoietic stem cell transplantation. The use of these markers makes it feasible to track Tr1 cells in vivo and purify Tr1 cells for cell therapy to induce or restore tolerance in subjects with immune-mediated diseases. © 2013 Nature America, Inc. All rights reserved

Immune dysregulation, Polyendocrinopathy, Enteropathy X-linked (IPEX) syndrome is a unique example of primary immunodeficiency characterized by autoimmune manifestations due to defective regulatory T (Treg) cells, in the presence of FOXP3 mutations. However, autoimmune symptoms phenotypically resembling IPEX often occur in the absence of detectable FOXP3 mutations. The cause of this “IPEX-like” syndrome presently remains unclear. To investigate whether a defect in Treg cells sustains the immunological dysregulation in IPEX-like patients, we measured the amount of peripheral Treg cells within the CD3+ T cells by analysing demethylation of the Treg cell-Specific-Demethylated-Region (TSDR) in the FOXP3 locus and demethylation of the T cell-Specific-Demethylated-Region (TLSDR) in the CD3 locus, highly specific markers for stable Treg cells and overall T cells, respectively. TSDR demethylation analysis, alone or normalized for the total T cells, showed that the amount of peripheral Treg cells in a cohort of IPEX-like patients was significantly reduced, as compared to both healthy subjects and unrelated disease controls. This reduction could not be displayed by flow cytometric analysis, showing highly variable percentages of FOXP3+ and CD25+FOXP3+ T cells. These data provide evidence that a quantitative defect of Treg cells could be considered a common biological hallmark of IPEX-like syndrome. Since Treg cell suppressive function was not impaired, we propose that this reduction per se could sustain autoimmunity., Highlights ► FOXP3 (TSDR) and CD3 (TLSDR) demethylation assays allow Treg cell quantification. ► TSDR/TLSDR ratio is altered in the majority of patients with immune dysregulation. ► IPEX-like syndromes share a quantitative but not functional defect of Treg cells.

Forkhead box P3 (FOXP3) is constitutively expressed by CD4+CD25hi regulatory T cells (nTregs). Mutations of FOXP3 cause a severe autoimmune syndrome known as immune dysregulation polyendocrinopathy enteropathy X-linked, in which nTregs are absent or dysfunctional. Whether FOXP3 is essential for both differentiation and function of human nTreg cells remains to be demonstrated. Because FOXP3 is an X-linked gene subject to X-chromosome inactivation (XCI), we studied 9 healthy female carriers of FOXP3 mutations to investigate the role of wild-type (WT) versus mutated FOXP3 in different cell subsets. Analysis of active WT versus mutated (mut)–FOXP3 allele distribution revealed a random pattern of XCI in peripheral blood lymphocytes and in naive and memory CD4+T cells, whereas nTregs expressed only the active WT-FOXP3. These data demonstrate that expression of WT-FOXP3 is indispensable for the presence of a normal nTreg compartment and suggest that FOXP3 is not necessary for effector T-cell differentiation in humans.

Systemic delivery of lentiviral vector (LV) in immunocompetent mice leads to efficient in vivo cell transduction and expression of the encoded protein under the control of the ubiquitous promoter of human cytomegalovirus (CMV). However, antitransgene immune response results in clearance of transduced cells 4 weeks after injection. T regulatory cells (Tregs), which have been demonstrated to control immune responses in vivo, were tested for their ability to suppress antitransgene response leading to stable long-term expression. Adoptive transfer of natural CD4+CD25+ Tregs (nTregs) isolated from wild type (wt) mice or from transgene tolerant transgenic (tg) mice did not suppress the antitransgene immune response after LV delivery. These data demonstrate that neither increasing the endogenous pool of natural Tregs nor transferring nTregs selected in a transgene-expressing thymus can modulate the immune response and mediate sustained transgene expression. Conversely, adoptive transfer of antigen-presenting cells (APCs) isolated from transgene-tolerant tg mice efficiently reduced the immune response leading to stable LV-encoded protein expression in vivo. Reduction of CD8+ effector T cells was observed in LV-treated mice coinjected with transgene-expressing APCs compared with control mice. These data indicate that antitransgene immune response can be modulated by transgene-expressing APCs possibly through deletion of effector T cells.

A deeper understanding of T lymphocytes survival and differentiation potential in humans is paramount for the development of effective gene/cell therapies based on T-cell engineering. We here performed a comprehensive study of T-cells dynamics and plasticity in humans by a unique combination of phenotypic/functional studies and high-throughput integration sites (IS) analyses. We analyzed samples from hematopoietic stem cells (HSC) (n=10) or mature lymphocytes (PBL) gene therapy (GT) (n=4) treated ADA (adenosine deaminase) deficient-SCID patients. For comparative analyses, we also collected data from pediatric (n=19) and adult (n=52) healthy donors (HD), and from bone marrow transplanted patients (BMT) with primary immunodeficiencies (n=10, 4 with ADA-SCID). We observed that vector-positive CD62L+/CD45RA+ putative T naïve cells were detectable 12 years after last infusion of gene-corrected lymphocytes in peripheral blood of PBL-GT patients that lack the support of transduced lymphocytes precursors. We then unveiled that the vast majority of these CD62L+/CD45RA+ cells (80.3%) in PBL-GT patients could be actually classified phenotypically (CD95, IL2Rβ and IL7Rα surface expression) and functionally (IFNγ production and aCD3/aCD28 in vitro differentiation) as active long-lasting T memory stem cells (Tscm). The peculiar Tscm frequency found in PBL-GT patients was most likely due to a combinatorial in vitro and in vivo effect. Indeed, by a series of in vitro assays, we showed that Tscm relative enrichment in CD45RA+CD62L+ compartment have occurred during the in vitro manipulation of T cells before infusion. Additionally, we found higher-then-normal Tscm contribution among CD45RA+/CD62L+ cells even in ADA-SCID patients receiving HSC-GT and BMT, suggesting a role of disease background on in vivo Tscm persistence. Analyzing our cohorts of healthy donors and treated individuals we were able to further correlate Tscm contribution in vivo with age, conditioning regimen, disease background, cell source, and long-term T-cell reconstitution. One unique aspect of our study consisted in the opportunity to track Tscm clonal dynamics in vivo in humans since each gene-corrected cell infused in our GT patients is univocally and permanently tagged by a retroviral integration site.To perform in vivo molecular tracing of individual T-cell clones we sorted T naïve, Tscm, central memory and effector memory subtypes. We then collected from these subpopulations, by LAM-PCR+Illumina-Miseq sequencing, 2.584.137 integration sites (IS) sequences mapped to 1.746 unique chromosomal positions, corresponding to 910 integrations from 5 HSC-GT patients in vivo, 79 integrations from 2 PBL-GT samples of transduced cell products prior to infusion and 754 integrations from 4 PBL-GT patients in vivo. Firstly, to establish a relationship between precursors and terminally differentiated T cells we searched for the presence of identical insertion sites detected in multiple T-cell subtypes, applying stringent analytical filters for cross-contaminations. Strikingly, the level of shared integrations in each subtype was directly correlated to its stage of differentiation with Tscm, isolated from PBL-GT patients, showing the highest proportion of integration sites shared with the other T-cell subsets. Importantly, the results of the same analysis performed on HSC-GT patients were outstandingly coherent with the progressive developmental model of memory T-cell differentiation. We then assessed the survival of individual Tscm clones by performing a longitudinal IS analysis of different T-cell subtypes isolated from 3 PBL-GT patients over a 2 to 5 years timeframe up to 12 years after last infusion. We were able to formally prove the persistence of individual Tscm by re-capturing identical IS tagging specific Tscm clones in two independent timepoints in a 5- years window. Importantly, the same IS were also detected in multiple T-cell subtypes, representing the best indirect evidence that these clones were endowed with long-term precursor activity. We also documented, by IS sequencing reads, the long-term polyclonal composition of each subtype and we did not observe enrichment for IS flanking proto-oncogenes. Overall, this study validates, for the first time in humans, the safe and functional decade-long survival of engineered Tscm, paving the way for their future application in clinical settings. Disclosures No relevant conflicts of interest to declare.

Human leukocyte antigen (HLA)-G is a non-classical HLA class I molecule with known immune-modulatory functions. Our group identified a subset of human dendritic cells, named DC-10, that induce adaptive interleukin-10-producing T regulatory type 1 (Tr1) cells via the interleukin-10-dependent HLA-G/ILT4 pathway. In this study we aimed at defining the role of HLA-G in DC-10-mediated Tr1 cell differentiation. We analyzed phenotype, functions, and genetic variations in the 3' untranslated region of the HLA-G locus of in vitro-differentiated DC-10 from 67 healthy donors. We showed that HLA-G expression on DC-10 is donor-dependent. Functional studies demonstrated that DC-10, independently of HLA-G expression, secrete interleukin-10 and negligible levels of interleukin-12. Interestingly, DC-10 with high HLA-G promote allo-specific anergic T cells that contain a significantly higher frequency of Tr1 cells, defined as interleukin-10-producing (P=0.0121) or CD49b(+)LAG-3(+) (P=0.0031) T cells, compared to DC-10 with low HLA-G. We found that the HLA-G expression on DC-10 is genetically imprinted, being associated with specific variations in the 3' untranslated region of the gene, and it may be finely tuned by microRNA-mediated post-transcriptional regulation. These data highlight the important role of HLA-G in boosting DC-10 tolerogenic activity and confirm that interleukin-10 production by DC-10 is necessary but not sufficient to promote Tr1 cells at high frequency. These new insights into the role of HLA-G in DC-10-mediated induction of Tr1 cells provide additional information for clinical use in Tr1- or DC-10-based cell therapy approaches.

Mice reconstituted with a human immune system provide a tractable in vivo model to assess human immune cell function. To date, reconstitution of murine strains with human hematopoietic stem cells (HSCs) from patients with monogenic immune disorders have not been reported. One obstacle precluding the development of immune-disease specific “humanized” mice is that optimal adaptive immune responses in current strains have required implantation of autologous human thymic tissue. To address this issue, we developed a mouse strain that lacks murine major histocompatibility complex class II (MHC II) and instead expresses human leukocyte antigen DR1 (HLA-DR1). These mice displayed improved adaptive immune responses when reconstituted with human HSCs including enhanced T-cell reconstitution, delayed-type hypersensitivity responses, and class-switch recombination. Following immune reconstitution of this novel strain with HSCs from a patient with immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome, associated with aberrant FOXP3 function, mice developed a lethal inflammatory disorder with multiorgan involvement and autoantibody production mimicking the pathology seen in affected humans. This humanized mouse model permits in vivo evaluation of immune responses associated with genetically altered HSCs, including primary immunodeficiencies, and should facilitate the study of human immune pathobiology and the development of targeted therapeutics.

BACKGROUND: Enteropathy in coeliac disease (CD) is sustained by a gliadin specific Th1 response. Interleukin (IL)-10 can downregulate Th1 immune responses. AIM: We investigated the ability of recombinant human (rh) IL-10 to suppress gliadin induced Th1 response. PATIENTS AND METHODS: IL-10 RNA transcripts were analysed by competitive reverse transcription-polymerase chain reaction in duodenal biopsies from untreated and treated CD patients, non-coeliac enteropathies (NCE), and controls. CD biopsies were cultured with a peptic-tryptic digest of gliadin with or without rhIL-10. The proportion of CD80+ and CD25+ cells in the lamina propria, epithelial expression of Fas, intraepithelial infiltration of CD3+ cells, as well as cytokine synthesis (interferon gamma (IFN-gamma) and IL-2) were measured. Short term T cell lines (TCLs) obtained from treated CD biopsies cultured with gliadin with or without rhIL-10 were analysed by ELISPOT for gliadin specific production of IFN-gamma. RESULTS: In untreated CD and NCE, IL-10 RNA transcripts were significantly upregulated. In ex vivo organ cultures, rhIL-10 downregulated gliadin induced cytokine synthesis, inhibited intraepithelial migration of CD3+ cells, and reduced the proportion of lamina propria CD25+ and CD80+ cells whereas it did not interfere with epithelial Fas expression. In short term TCLs, rhIL-10 abrogated the IFN-gamma response to gliadin. CONCLUSIONS: rhIL-10 suppresses gliadin specific T cell activation. It may interfere with the antigen presenting capacity of lamina propria mononuclear cells as it reduces the expression of CD80. Interestingly, rhIL-10 also induces a long term hyporesponsiveness of gliadin specific mucosal T cells. These results offer new perspectives for therapeutic strategies in coeliac patients based on immune modulation by IL-10.

Next-Generation Gene Therapy Few disciplines in contemporary clinical research have experienced the high expectations directed at the gene therapy field. However, gene therapy has been challenging to translate to the clinic, often because the therapeutic gene is expressed at insufficient levels in the patient or because the gene delivery vector integrates near protooncogenes, which can cause leukemia (see the Perspective by Verma ). Biffi et al. ( 1233158 , published online 11 July) and Aiuti et al. ( 1233151 ; published online 11 July) report progress on both fronts in gene therapy trials of three patients with metachromatic leukodystrophy (MLD), a neurodegenerative disorder, and three patients with Wiskott-Aldrich syndrome (WAS), an immunodeficiency disorder. Optimized lentiviral vectors were used to introduce functional MLD or WAS genes into the patients' hematopoietic stem cells (HSCs) ex vivo, and the transduced cells were then infused back into the patients, who were then monitored for up to 2 years. In both trials, the patients showed stable engraftment of the transduced HSC and high expression levels of functional MLD or WAS genes. Encouragingly, there was no evidence of lentiviral vector integration near proto-oncogenes, and the gene therapy treatment halted disease progression in most patients. A longer follow-up period will be needed to further validate efficacy and safety.

International audience

"The success of in vivo gene therapy greatly depends on the ability to control the immune response toward the therapeutic transgene. Over the last decade several vector-based and pharmacological approaches have been explored to control the immune-mediated clearance of transgene-expressing cells after viral delivery. One important outcome from these studies is the concept that expression of a transgene in tolerance-promoting organs, such as the liver and tolerogenic antigen-presenting cells, can help safeguard transgene-expressing cells from immune-mediated clearance. Gene therapists are now manipulating vectors to target naturally occurring tolerogenic properties of the body by: (i) incorporating tissue/cell specific promoters for targeted expression, (ii) using viral-capsid engineering to alter tropism and avoid pre-existing immunity, and (iii) regulating cell and activation dependent expression by including micro-RNA (miR) targets into expression cassettes. The combination of these three layers of vector regulation greatly enhances the targeting of tolerogenic cells and limits off-target expression of the transgene, which can lead to the induction of transgene-specific pathogenic effector T cells. In this review, we discuss the application of using miR transgene regulation to generate tolerogenic responses and speculate on possible mechanisms used by the liver to induce the transgene-specific regulatory T cells."

Type 1 T regulatory (Tr1) cells suppress immune responses in vivo and in vitro and play a key role in maintaining tolerance to self- and non–self-antigens. Interleukin-10 (IL-10) is the crucial driving factor for Tr1 cell differentiation, but the molecular mechanisms underlying this induction remain unknown. We identified and characterized a subset of IL-10–producing human dendritic cells (DCs), termed DC-10, which are present in vivo and can be induced in vitro in the presence of IL-10. DC-10 are CD14+, CD16+, CD11c+, CD11b+, HLA-DR+, CD83+, CD1a−, CD1c−, express the Ig-like transcripts (ILTs) ILT2, ILT3, ILT4, and HLA-G antigen, display high levels of CD40 and CD86, and up-regulate CD80 after differentiation in vitro. DC-10 isolated from peripheral blood or generated in vitro are potent inducers of antigen-specific IL-10–producing Tr1 cells. Induction of Tr1 cells by DC-10 is IL-10–dependent and requires the ILT4/HLA-G signaling pathway. Our data indicate that DC-10 represents a novel subset of tolerogenic DCs, which secrete high levels of IL-10, express ILT4 and HLA-G, and have the specific function to induce Tr1 cells.

Adaptive type I regulatory T (Tr1) cells are suppressor cells characterized by the production of interleukin (IL)-10 in the absence of IL-4. IL-10 is essential not only for suppression of effector cells by Tr1 cells, but also for their differentiation in vitro and in vivo. However, little is known on the molecular mechanisms underneath the IL-10-mediated induction of Tr1 cells. Human Leukocyte Antigen (HLA)-G, a non-classical HLA class I molecule, has both direct inhibitory effects on natural killer cells, dendritic cells (DC), and T cells and long-term tolerogenic indirect effects by inducing regulatory T (Tr) cells. in the present review, we discuss current findings on Tr-cell induction by the different isoforms of HLA-G, focusing on the relationship among HLA-G, its ligands, and IL-10. We recently described a subset of human DC, termed DC-10, that express high levels of HLA-G and ILT4, secrete high amounts of IL-10, and induce allospecific Tr1 cells in vitro via an IL-10-dependent ILT4/HLA-G pathway. IL-10, HLA-G, and ILT4 may also be involved in Tr1-cell induction in vivo. Overall, these data demonstrate that cross-regulation between IL-10 and HLA-G may be instrumental for Tr1-cell induction and tolerance. (C) 2009 American Society for Histocompatibility and Immunogenetics. Published by Elsevier Inc. All rights reserved.

Background: We investigated the long-term outcome of gene therapy for severe combined immunodeficiency (SCID) due to the lack of adenosine deaminase (ADA), a fatal disorder of purine metabolism and immunodeficiency. Methods: We infused autologous CD34+ bone marrow cells transduced with a retroviral vector containing the ADA gene into 10 children with SCID due to ADA deficiency who lacked an HLA-identical sibling donor, after nonmyeloablative conditioning with busulfan. Enzyme-replacement therapy was not given after infusion of the cells. Results: All patients are alive after a median follow-up of 4.0 years (range, 1.8 to 8.0). Transduced hematopoietic stem cells have stably engrafted and differentiated into myeloid cells containing ADA (mean range at 1 year in bone marrow lineages, 3.5 to 8.9%) and lymphoid cells (mean range in peripheral blood, 52.4 to 88.0%). Eight patients do not require enzyme-replacement therapy, their blood cells continue to express ADA, and they have no signs of defective detoxification of purine metabolites. Nine patients had immune reconstitution with increases in T-cell counts (median count at 3 years, 1.07 x 10(sup 9) per liter) and normalization of T-cell function. In the five patients in whom intravenous immune globulin replacement was discontinued, antigen-specific antibody responses were elicited after exposure to vaccines or viral antigens. Effective protection against infections and improvement in physical development made a normal lifestyle possible. Serious adverse events included prolonged neutropenia (in two patients), hypertension (in one), central-venous-catheter-related infections (in two), Epstein-Barr virus reactivation (in one), and autoimmune hepatitis (in one). Conclusions: Gene therapy, combined with reduced-intensity conditioning, is a safe and effective treatment for SCID in patients with ADA deficiency. (ClinicalTrials.gov numbers, NCT00598481 and NCT00599781.) N Engl J Med 2009;360:447-58. RI rossi, paolo/D-6504-2012; galimberti, stefania/H-2594-2012 BACKGROUND:We investigated the long-term outcome of gene therapy for severe combined immunodeficiency (SCID) due to the lack of adenosine deaminase (ADA), a fatal disorder of purine metabolism and immunodeficiency.METHODS:We infused autologous CD34+ bone marrow cells transduced with a retroviral vector containing the ADA gene into 10 children with SCID due to ADA deficiency who lacked an HLA-identical sibling donor, after nonmyeloablative conditioning with busulfan. Enzyme-replacement therapy was not given after infusion of the cells.RESULTS:All patients are alive after a median follow-up of 4.0 years (range, 1.8 to 8.0). Transduced hematopoietic stem cells have stably engrafted and differentiated into myeloid cells containing ADA (mean range at 1 year in bone marrow lineages, 3.5 to 8.9%) and lymphoid cells (mean range in peripheral blood, 52.4 to 88.0%). Eight patients do not require enzyme-replacement therapy, their blood cells continue to express ADA, and they have no signs of defective detoxification of purine metabolites. Nine patients had immune reconstitution with increases in T-cell counts (median count at 3 years, 1.07x10(9) per liter) and normalization of T-cell function. In the five patients in whom intravenous immune globulin replacement was discontinued, antigen-specific antibody responses were elicited after exposure to vaccines or viral antigens. Effective protection against infections and improvement in physical development made a normal lifestyle possible. Serious adverse events included prolonged neutropenia (in two patients), hypertension (in one), central-venous-catheter-related infections (in two), Epstein-Barr virus reactivation (in one), and autoimmune hepatitis (in one).CONCLUSIONS:Gene therapy, combined with reduced-intensity conditioning, is a safe and effective treatment for SCID in patients with ADA deficiency. (ClinicalTrials.gov numbers, NCT00598481 and NCT00599781.) BackgroundWe investigated the long-term outcome of gene therapy for severe combined immunodeficiency(SCID) due to the lack of adenosine deaminase (ADA), a fatal disorderof purine metabolism and immunodeficiency.MethodsWe infused autologous CD34+ bone marrow cells transduced with a retroviral vectorcontaining the ADA gene into 10 children with SCID due to ADA deficiency wholacked an HLA-identical sibling donor, after nonmyeloablative conditioning withbusulfan. Enzyme-replacement therapy was not given after infusion of the cells.ResultsAll patients are alive after a median follow-up of 4.0 years (range, 1.8 to 8.0). Transducedhematopoietic stem cells have stably engrafted and differentiated into myeloidcells containing ADA (mean range at 1 year in bone marrow lineages, 3.5 to 8.9%)and lymphoid cells (mean range in peripheral blood, 52.4 to 88.0%). Eight patientsdo not require enzyme-replacement therapy, their blood cells continue to expressADA, and they have no signs of defective detoxification of purine metabolites. Ninepatients had immune reconstitution with increases in T-cell counts (median countat 3 years, 1.07×109 per liter) and normalization of T-cell function. In the five patientsin whom intravenous immune globulin replacement was discontinued, antigenspecificantibody responses were elicited after exposure to vaccines or viral antigens.Effective protection against infections and improvement in physical development madea normal lifestyle possible. Serious adverse events included prolonged neutropenia(in two patients), hypertension (in one), central-venous-catheter–related infections (intwo), Epstein–Barr virus reactivation (in one), and autoimmune hepatitis (in one).ConclusionsGene therapy, combined with reduced-intensity conditioning, is a safe and effectivetreatment for SCID in patients with ADA deficiency. (ClinicalTrials.gov numbers,NCT00598481 and NCT00599781.)

BACKGROUND: Immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome is an autoimmune genetic disorder caused by mutation of the forkhead box protein 3 gene (FOXP3), a key regulator of immune tolerance. OBJECTIVE: We sought to provide clinical and molecular indicators that facilitate the understanding and diagnosis of IPEX syndrome. METHODS: In 14 unrelated affected male subjects who were given diagnoses of IPEX syndrome based on FOXP3 gene sequencing, we determined whether particular FOXP3 mutations affected FOXP3 protein expression and correlated the molecular and clinical data. RESULTS: Molecular analysis of FOXP3 in the 14 subjects revealed 13 missense and splice-site mutations, including 7 novel mutations. Enteropathy, generally associated with endocrinopathy and eczema, was reported in all patients, particularly in those carrying mutations within FOXP3 functional domains or mutations that altered protein expression. However, similar genotypes did not always result in similar phenotypes in terms of disease presentation and severity. In addition, FOXP3 protein expression did not correlate with disease severity. CONCLUSION: Severe autoimmune enteropathy, which is often associated with increased IgE levels and eosinophilia, is the most prominent early manifestation of IPEX syndrome. Nevertheless, the disease course is variable and somewhat unpredictable. Therefore genetic analysis of FOXP3 should always be performed to ensure an accurate diagnosis, and FOXP3 protein expression analysis should not be the only diagnostic tool for IPEX syndrome. OI RONCAROLO, Maria Grazia/0000-0002-2193-9186 ZS 1 ZR 2 ZB 47 Z8 7

Immune regulation and tolerance are specific functions of the immune system, meaning at prevention or limitation of effector immune responses against inner and external insults. Regulatory T (Treg) cells are crucial players in this immune balance network. Research over the last 10 years has significantly contributed to characterizing Treg cell features, their mechanisms of function, and their role in human pathologies. The discovery of FOXP3 as an essential transcription factor not only for differentiation and function of naturally occurring Treg cells but also for regulation of intracellular molecules related to effector T-cell responses has provided new insights into the pathogenesis of immune-mediated diseases. Interestingly, there is increasing evidence that the individual signature of genes relevant for immune regulation definitely influences the final outcome of an immune response.

Background Wiskott-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. Objective Because 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. Methods We 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. Results After 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 CD21 low B cells and a reduction in B cell–activating factor levels. Immunoglobulin serum levels and autoantibody production improved in all treated patients. Conclusions We 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.