280 lentiviral mediated gene therapy restores b cell homeostasis and tolerance in wiskott aldrich syndrome patients

Wiskott-Aldrich Syndrome (WAS) is a severe X-linked primary immunodeficiency characterized by micro-thrombocytopenia, eczema and increased risk of infections, autoimmunity and tumors. Allogeneic hematopoietic stem cell (HSC) transplantation is a recognized curative treatment for WAS, but when a matched donor is not available, administration of WAS gene-corrected autologous HSCs represents a valid alternative therapeutic approach. Since alterations of WAS protein (WASp)-deficient B lymphocytes contribute to immunodeficiency and autoimmunity in WAS, we followed the B cell reconstitution in 4 WAS patients treated by lentiviral vector-gene therapy (GT) after a reduced-intensity conditioning regimen combined with anti-CD20 administration. We analyzed the B cell subset distribution in the bone marrow and peripheral blood by flow cytometry and the autoantibody profile by a high-throughput autoantigen microarray platform before and after GT. Lentiviral vector-transduced progenitor cells were able to repopulate the B cell compartment with a normal distribution of transitional, naive and memory B cells. The reduction in the proportion of autoimmune-associated CD21low B cells and in the plasma levels of B cell-activating factor was associated with the decreased autoantibody production in WAS patients after GT. Then, we evaluated the functionality of B cell tolerance checkpoints by testing the reactivity of recombinant antibodies isolated from single B cells. Before GT, we found a decreased frequency of autoreactive new emigrant/transitional B cells in WAS patients, suggesting a hyperfunctional central B cell checkpoint in the absence of WASp. In contrast, high frequency of polyreactive and Hep2 reactive clones were found in mature naive B cells of WAS patients, indicating a defective peripheral B cell checkpoint. Both central and peripheral B cell tolerance checkpoints were restored after GT, further supporting the qualitative efficacy of this treatment. In conclusion, WASp plays an important role in the regulation of B cell homeostasis and in the establishment of B cell tolerance in humans and lentiviral-mediated GT is able to ameliorate the functionality of B cell compartment contributing to the clinical and immunological improvement in WAS patients

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

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 CD21low

Partial correction of immunodeficiency by lentiviral vector gene therapy in mouse models carrying Rag1 hypomorphic mutations

IntroductionRecombination activating genes (RAG) 1 and 2 defects are the most frequent form of severe combined immunodeficiency (SCID). Patients with residual RAG activity have a spectrum of clinical manifestations ranging from Omenn syndrome to delayed-onset combined immunodeficiency, often associated with granulomas and/or autoimmunity (CID-G/AI). Lentiviral vector (LV) gene therapy (GT) has been proposed as an alternative treatment to the standard hematopoietic stem cell transplant and a clinical trial for RAG1 SCID patients recently started. However, GT in patients with hypomorphic RAG mutations poses additional risks, because of the residual endogenous RAG1 expression and the general state of immune dysregulation and associated inflammation.MethodsIn this study, we assessed the efficacy of GT in 2 hypomorphic Rag1 murine models (Rag1F971L/F971L and Rag1R972Q/R972Q), exploiting the same LV used in the clinical trial encoding RAG1 under control of the MND promoter.Results and discussionStarting 6 weeks after transplant, GT-treated mice showed a decrease in proportion of myeloid cells and a concomitant increase of B, T and total white blood cells. However, counts remained lower than in mice transplanted with WT Lin- cells. At euthanasia, we observed a general redistribution of immune subsets in tissues, with the appearance of mature recirculating B cells in the bone marrow. In the thymus, we demonstrated correction of the block at double negative stage, with a modest improvement in the cortical/medullary ratio. Analysis of antigenspecific IgM and IgG serum levels after in vivo challenge showed an amelioration of antibody responses, suggesting that the partial immune correction could confer a clinical benefit. Notably, no overt signs of autoimmunity were detected, with B-cell activating factor decreasing to normal levels and autoantibodies remaining stable after GT. On the other hand, thymic enlargement was frequently observed, although not due to vector integration and insertional mutagenesis. In conclusion, our work shows that GT could partially alleviate the combined immunodeficiency of hypomorphic RAG1 patients and that extensive efficacy and safety studies with alternative models are required before commencing RAG gene therapy in thesehighly complex patients

Intestinal microbiota sustains inflammation and autoimmunity induced by hypomorphic RAG defects

Omenn syndrome (OS) is caused by hypomorphic Rag mutations and characterized by a profound immunodeficiency associated with autoimmune-like manifestations. Both in humans and mice, OS is mediated by oligoclonal activated T and B cells. The role of microbial signals in disease pathogenesis is debated. Here, we show that Rag2R229Q knock-in mice developed an inflammatory bowel disease affecting both the small bowel and colon. Lymphocytes were sufficient for disease induction, as intestinal CD4 T cells with a Th1/Th17 phenotype reproduced the pathological picture when transplanted into immunocompromised hosts. Moreover, oral tolerance was impaired in Rag2R229Q mice, and transfer of wild-type (WT) regulatory T cells ameliorated bowel inflammation. Mucosal immunoglobulin A (IgA) deficiency in the gut resulted in enhanced absorption of microbial products and altered composition of commensal communities. The Rag2R229Q microbiota further contributed to the immunopathology because its transplant into WT recipients promoted Th1/Th17 immune response. Consistently, long-term dosing of broad-spectrum antibiotics (ABXs) in Rag2R229Q mice ameliorated intestinal and systemic autoimmunity by diminishing the frequency of mucosal and circulating gut-tropic CCR9+ Th1 and Th17 T cells. Remarkably, serum hyper-IgE, a hallmark of the disease, was also normalized by ABX treatment. These results indicate that intestinal microbes may play a critical role in the distinctive immune dysregulation of OS

Wiskott-Aldrich Syndrome protein deficiency perturbs the homeostasis of B-cell compartment in humans

Wiskott-Aldrich Syndrome protein (WASp) regulates the cytoskeleton in hematopoietic cells and mutations in its gene cause the Wiskott-Aldrich Syndrome (WAS), a primary immunodeficiency with microthrombocytopenia, eczema and a higher susceptibility to develop tumors. Autoimmune manifestations, frequently observed in WAS patients, are associated with an increased risk of mortality and still represent an unsolved aspect of the disease. B cells play a crucial role both in immune competence and self-tolerance and defects in their development and function result in immunodeficiency and/or autoimmunity. We performed a phenotypical and molecular analysis of central and peripheral B-cell compartments in WAS pediatric patients. We found a decreased proportion of immature B cells in the bone marrow correlating with an increased presence of transitional B cells in the periphery. These results could be explained by the defective migratory response of WAS B cells to SDF-1α, essential for the retention of immature B cells in the BM. In the periphery, we observed an unusual expansion of CD21low B-cell population and increased plasma BAFF levels that may contribute to the high susceptibility to develop autoimmune manifestations in WAS patients. WAS memory B cells were characterized by a reduced in vivo proliferation, decreased somatic hypermutation and preferential usage of IGHV4-34, an immunoglobulin gene commonly found in autoreactive B cells. In conclusion, our findings demonstrate that WASp-deficiency perturbs B-cell homeostasis thus adding a new layer of

Wiskott-Aldrich syndrome protein-mediated actin dynamics control type-I interferon production in plasmacytoid dendritic cells

Mutations in Wiskott-Aldrich syndrome (WAS) protein (WASp), a regulator of actin dynamics in hematopoietic cells, cause WAS, an X-linked primary immunodeficiency characterized by recurrent infections and a marked predisposition to develop autoimmune disorders. The mechanisms that link actin alterations to the autoimmune phenotype are still poorly understood. We show that chronic activation of plasmacytoid dendritic cells (pDCs) and elevated type-I interferon (IFN) levels play a role in WAS autoimmunity. WAS patients display increased expression of type-I IFN genes and their inducible targets, alteration in pD

IL-10 critically modulates B cell responsiveness in rankl^-/- mice

Abstract The immune and the skeletal system are tightly interconnected, and B lymphocytes are uniquely endowed with osteo-interactive properties. In this context, receptor activator of NF-κB (RANK) ligand (RANKL) plays a pivotal role in lymphoid tissue formation and bone homeostasis. Although murine models lacking RANK or RANKL show defects in B cell number, the role of the RANKL–RANK axis on B physiology is still a matter of debate. In this study, we have characterized in detail B cell compartment in Rankl−/− mice, finding a relative expansion of marginal zone B cells, B1 cells, and plasma cells associated with increased Ig serum levels, spontaneous germinal center formation, and hyperresponse to CD40 triggering. Such abnormalities were associated with an increased frequency of regulatory B cells and augmented B cell–derived IL-10 production. Remarkably, in vivo IL-10-R blockade reduced T cell–triggered plasma cell differentiation and restrained the expansion of regulatory B cells. These data point to a novel role of the RANKL–RANK axis in the regulation of B cell homeostasis and highlight an unexpected link between IL-10 CD40 signaling and the RANKL pathway.</jats:p

Autonomous role of Wiskott-Aldrich Syndrome platelet deficiency in inducing autoimmunity and inflammation

Wiskott-Aldrich Syndrome (WAS) is an X-linked immunodeficiency characterized by eczema, infections and susceptibility to develop autoimmunity and malignancies. Thrombocytopenia is a constant finding, but its pathogenesis remains elusive