RARE DISEASE
Severe combined immunodeficiency due to complete RAG1/2 deficiency
Severe combined immunodeficiency due to complete RAG1/2 deficiency
Severe combined immunodeficiency due to complete RAG1/2 deficiency
Synonyms: SCID due to complete RAG1/2 deficiency
Synonyms: SCID due to complete RAG1/2 deficiency
Synonyms: SCID due to complete RAG1/2 deficiency
Drug discovery
2
drugs
With orphan designations
Overview
Severe combined immunodeficiency (SCID) due to complete RAG1/2 deficiency is a rare, autosomal recessive genetic disorder caused by null mutations in RAG1 or RAG2, resulting in <1% residual V(D)J recombination activity. This impairs T/B-cell development, leading to profound lymphopenia, absent immunoglobulins, and severe susceptibility to opportunistic infections (viral, fungal, bacterial) presenting neonatally. Clinical features include failure to thrive, chronic diarrhea, erythroderma, and fatal complications without intervention. Immediate diagnosis via newborn screening and prompt hematopoietic stem cell transplantation (HSCT) are critical for survival [3][4][10].
Burden
Mortality: Near 100% fatality by age 2 without HSCT; survival post-HSCT ranges 54–67%, lower in Omenn syndrome [4][14][16].
Morbidity: Chronic infections, granulomatous disease (skin/viscera), and autoimmunity (cytopenias, vitiligo) drive lifelong disability [4][6][15].
Resource Use: Requires intensive isolation, prolonged hospitalization, and multidisciplinary care pre-/post-HSCT [2][14].
Therapies
Curative: Early HSCT (preferred before 3.5 months), with higher success using matched donors (survival: 54–67%) [4][12][16].
Supportive: Immunoglobulin replacement, antimicrobial prophylaxis, and immunosuppression for autoimmune complications [1][3][10].
Experimental: Gene therapy is under clinical investigation but not yet standard [6][17].
Categories: rare genetic diseases, rare immunological diseases, rare transplant-related disorders
Research Papers
62 drug discovery papers about Severe combined immunodeficiency due to complete RAG1/2 deficiency, with 2 first-in-class emerging drug candidates forecasted to outperform the average preclinical success rate. Recent publications:
62 drug discovery papers about Severe combined immunodeficiency due to complete RAG1/2 deficiency, with 2 first-in-class emerging drug candidates forecasted to outperform the average preclinical success rate. Recent publications:
categories:
Small molecules
cell therapies
2024-04-18 | Antiviral cellular therapy for enhancing T-cell reconstitution before or after hematopoietic stem cell transplantation (ACES): a two-arm, open label phase II interventional trial of pediatric patients with risk factor assessment
Viral infections remain a major risk in immunocompromised pediatric patients, and virus-specific T cell (VST) therapy has been successful for treatment of refractory viral infections in prior studies. We performed a phase II multicenter study (NCT03475212) for the treatment of pediatric patients with inborn errors of immunity and/or post allogeneic hematopoietic stem cell transplant with refractory viral infections using partially-HLA matched VSTs targeting cytomegalovirus, Epstein-Barr virus, or adenovirus. Primary endpoints were feasibility, safety, and clinical responses (>1 log reduction in viremia at 28 days). Secondary endpoints were reconstitution of antiviral immunity and persistence of the infused VSTs. Suitable VST products were identified for 75 of 77 clinical queries. Clinical responses were achieved in 29 of 47 (62%) of patients post-HSCT including 73% of patients evaluable at 1-month post-infusion, meeting the primary efficacy endpoint (>52%). Secondary graft rejection occurred in one child following VST infusion as described in a companion article. Corticosteroids, graft-versus-host disease, transplant-associated thrombotic microangiopathy, and eculizumab treatment correlated with poor response, while uptrending absolute lymphocyte and CD8 T cell counts correlated with good response. This study highlights key clinical factors that impact response to VSTs and demonstrates the feasibility and efficacy of this therapy in pediatric HSCT.
2023-02-07 | Hematopoietic stem cell transplantation for inborn errors of immunity: 30-year single-center experience
Allogeneic hematopoietic stem cell transplantation (allo-HSCT) represents an effective treatment for a variety of inborn errors of immunity (IEI). We report the experience of children affected by IEI who received allo-HSCT over a period of 32 years at IRCCS Istituto Giannina Gaslini, Genoa, Italy. HSCTs were performed in 67 children with IEI. Kaplan-Meier estimates of overall survival (OS) rate at 5 years in the whole group of patients was 83.4% after a median follow-up of 4 years. Median age at transplant was 2.5 years. Eight allo-HSCTs were complicated by either primary or secondary graft failure (GF), the overall incidence of this complication being 10.9%. Incidence of grade 3-4 acute GvHD (aGvHD) was 18.7%, significantly lower in the haploidentical transplant cohort (p = 0.005). Year of transplant (≤2006 vs. >2006) was the main factor influencing the outcome. In fact, a significant improvement in 5-year OS was demonstrated (92.5% >2006 vs. 65% ≤2006, p = 0.049). Frequency of severe aGvHD was significantly reduced in recent years (≤2006 61.5%, vs. >2006 20%, p = 0.027). A significant progress has been the introduction of the TCR αβ/CD19-depleted haploidentical platform, which was associated with the absence of severe aGvHD. However, it was associated with 23.5% incidence of GF. All but one patient experiencing GF in the this specific cohort were successfully retransplanted. In summary, allo-HSCT is confirmed to be an effective treatment for children with IEI, even in the absence of an HLA-matched donor.
2022-02-15 | Bayesian Modeling Immune Reconstitution Apply to CD34+ Selected Stem Cell Transplantation for Severe Combined Immunodeficiency
Severe combined immunodeficiencies (SCIDs) correspond to the most severe form of primary immunodeficiency. Allogeneic hematopoietic stem cell transplantation (HSCT) and gene therapy are curative treatments, depending on the donor's availability and molecular diagnostics. A partially human leukocyte antigen (HLA)-compatible donor used has been developed for this specific HSCT indication in the absence of a matched donor. However, the CD34+ selected process induces prolonged post-transplant T-cell immunodeficiency. The aim here was to investigate a modeling approach to predict the time course and the extent of CD4+ T-cell immune reconstitution after CD34+ selected transplantation. We performed a Bayesian approach based on the age-related changes in thymic output and the cell proliferation/loss model. For that purpose, we defined specific individual covariates from the data collected from 10 years of clinical practice and then evaluated the model's predicted performances and accuracy. We have shown that this Bayesian modeling approach predicted the time course and extent of CD4+ T-cell immune reconstitution after SCID transplantation.
2021-08-27 | Hematopoietic Cell Transplantation for Severe Combined Immunodeficiency Patients: a Japanese Retrospective Study
Hematopoietic cell transplantation (HCT) is a curative therapy for patients with severe combined immunodeficiency (SCID). Here, we conducted a nationwide study to assess the outcome of SCID patients after HCT in Japan.A cohort of 181 SCID patients undergoing their first allogeneic HCT in 1974-2016 was studied by using the Japanese national database (Transplant Registry Unified Management Program, TRUMP).The 10-year overall survival (OS) of the patients who received HCT in 2006-2016 was 67%. Umbilical cord blood (UCB) transplantation was performed in 81 patients (45%). The outcomes of HCT from HLA-matched UCB (n = 21) and matched sibling donors (n = 22) were comparable, including 10-year OS (91% vs. 91%), neutrophil recovery (cumulative incidence at 30 days, 89% vs. 100%), and platelet recovery (cumulative incidence at 60 days, 89% vs. 100%). Multivariate analysis of the patients who received HCT in 2006-2016 demonstrated that the following factors were associated with poor OS: bacterial or fungal infection at HCT (hazard ratio (HR): 3.8, P = 0.006), cytomegalovirus infection prior to HCT (HR: 9.4, P = 0.03), ≥ 4 months of age at HCT (HR: 25.5, P = 0.009), and mismatched UCB (HR: 19.8, P = 0.01).We showed the potential of HLA-matched UCB as a donor source with higher priority for SCID patients. We also demonstrated that early age at HCT without active infection is critical for a better prognosis, highlighting the importance of newborn screening for SCID.
2020-09-29 | Asymptomatic Infant With Atypical SCID and Novel Hypomorphic RAG Variant Identified by Newborn Screening: A Diagnostic and Treatment Dilemma
The T-cell receptor excision circle (TREC) assay was designed to detect T-cell lymphopenia (TCL) in newborns, especially to identify severe combined immunodeficiency (SCID). A spectrum of SCID variants and non-SCID conditions that present with TCL are being discovered by SCID newborn screening (NBS) with increasing frequency. Decisions for treatment are influenced by underlying genetic abnormalities. Recombination-activating gene (RAG) deficiency is one the most common causes of classical and atypical SCID and other conditions with immune dysregulation. This case report aims to highlight how NBS can expedite identification of an asymptomatic newborn with a novel hypomorphic RAG variant and a controversial immune phenotype that required in depth immune evaluation to confirm that the abnormal RAG genotype is linked to the disease and justify definitive therapy with hematopoietic stem cell transplantation (HSCT). Following identification of newborns with out of range TREC levels, the diagnostic approach followed at our center includes lymphocyte subset enumeration by flow-cytometry, quantitative serum immunoglobulin levels, lymphocyte proliferation upon mitogen stimulation and next generation DNA sequencing to search for genetic variants associated with SCID. For babies in whom novel RAG gene variants are detected, we also test for immune biomarkers, and if feasible, analyze the recombinase activity of the novel RAG variants by functional assays and T and B-cell receptor repertoire. We identified and validated pathogenicity for compound heterozygous hypomorphic RAG1 variants in an asymptomatic newborn with undetectable TRECs and controversial immunological phenotype with severe TCL, but normal B cell count and lymphocyte proliferation upon mitogen stimulation. Due to the potential for severe complications with infection and immune dysregulation, the patient underwent a matched unrelated HSCT and is doing well 15 months post-HSCT. In conclusion, partial RAG deficiency can be detected by NBS in some cases such as ours. In case of an atypical immune phenotype and novel RAG gene variants, in vivo and in vitro studies are needed to confirm causative association and expedite treatment with HSCT due to risk of serious infection and non-infectious complications.
gene therapies
2022-07-13 | Genetically Corrected RAG2-SCID Human Hematopoietic Stem Cells Restore V(D)J-Recombinase and Rescue Lymphoid Deficiency
ABSTRACT Recombination-activating genes ( RAG1 and RAG2 ) are critical in lymphoid cell development and function for initiating the V(D)J-recombination process to generate polyclonal lymphocytes with broad antigen-specificity. Clinical manifestations of defective RAG1/2 genes range from immune dysregulation to severe combined immunodeficiencies (SCID), causing life-threatening infections and death early in life in the absence of hematopoietic cell transplantation (HCT). Haploidentical HCT without myeloablative conditioning carries a high risk of graft failure and incomplete immune reconstitution. The RAG complex is only expressed during the G0-G1 phases of the cell cycle at the early stages of T and B cell development, underscoring that a direct gene correction would capture the precise temporal expression of the endogenous gene, is a promising therapeutic approach for RAG1/2 -deficiencies. Here, we report a feasibility study using the CRISPR/Cas9-based “universal gene-correction” approach for the RAG2 locus in human hematopoietic stem/progenitor cells (HSPCs) in healthy donors and one RAG2 -SCID patient. V(D)J recombinase activity was restored following gene correction of RAG2 -SCID-derived HSPCs, resulting in the development of TCR αβ and γδ CD3 + cells and single-positive CD4 + and CD8 + lymphocytes. TCR repertoire analysis indicated a normal distribution of the CDR3 length and preserved usage of distal TRAV genes. We confirmed in vivo rescue of B-cell development, with normal IgM surface expression and a significant decrease in CD56 bright NK cells. Together, we provide specificity, toxicity, and efficacy data supporting the development of a gene-correction therapy to benefit all RAG2 -deficient patients. KEY POINTS Human hematopoietic stem cells can be corrected to restore endogenous RAG2 gene expression while preserving durable engraftment potential. Gene-corrected RAG2 locus restores V(D)J recombination in RAG2 -SCID patient stem cells, promoting T and B-cells’ receptor formation.
2020-02-01 | Intrathymic adeno-associated virus gene transfer rapidly restores thymic function and long-term persistence of gene-corrected T cells
Patients with T-cell immunodeficiencies are generally treated with allogeneic hematopoietic stem cell transplantation, but alternatives are needed for patients without matched donors. An innovative intrathymic gene therapy approach that directly targets the thymus might improve outcomes.We sought to determine the efficacy of intrathymic adeno-associated virus (AAV) serotypes to transduce thymocyte subsets and correct the T-cell immunodeficiency in a zeta-associated protein of 70 kDa (ZAP-70)-deficient murine model.AAV serotypes were injected intrathymically into wild-type mice, and gene transfer efficiency was monitored. ZAP-70-/- mice were intrathymically injected with an AAV8 vector harboring the ZAP70 gene. Thymus structure, immunophenotyping, T-cell receptor clonotypes, T-cell function, immune responses to transgenes and autoantibodies, vector copy number, and integration were evaluated.AAV8, AAV9, and AAV10 serotypes all transduced thymocyte subsets after in situ gene transfer, with transduction of up to 5% of cells. Intrathymic injection of an AAV8-ZAP-70 vector into ZAP-70-/- mice resulted in a rapid thymocyte differentiation associated with the development of a thymic medulla. Strikingly, medullary thymic epithelial cells expressing the autoimmune regulator were detected within 10 days of gene transfer, correlating with the presence of functional effector and regulatory T-cell subsets with diverse T-cell receptor clonotypes in the periphery. Although thymocyte reconstitution was transient, gene-corrected peripheral T cells harboring approximately 1 AAV genome per cell persisted for more than 40 weeks, and AAV vector integration was detected.Intrathymic AAV-transduced progenitors promote a rapid restoration of the thymic architecture, with a single wave of thymopoiesis generating long-term peripheral T-cell function.
2018-09-01 | Efficacy of lentivirus-mediated gene therapy in an Omenn syndrome recombination-activating gene 2 mouse model is not hindered by inflammation and immune dysregulation
BackgroundOmenn syndrome (OS) is a rare severe combined immunodeficiency associated with autoimmunity and caused by defects in lymphoid-specific V(D)J recombination. Most patients carry hypomorphic mutations in recombination-activating gene (RAG) 1 or 2. Hematopoietic stem cell transplantation is the standard treatment; however, gene therapy (GT) might represent a valid alternative, especially for patients lacking a matched donor.ObjectiveWe sought to determine the efficacy of lentiviral vector (LV)–mediated GT in the murine model of OS (Rag2R229Q/R229Q) in correcting immunodeficiency and autoimmunity.MethodsLineage-negative cells from mice with OS were transduced with an LV encoding the human RAG2 gene and injected into irradiated recipients with OS. Control mice underwent transplantation with wild-type or OS-untransduced lineage-negative cells. Immunophenotyping, T-dependent and T-independent antigen challenge, immune spectratyping, autoantibody detection, and detailed tissue immunohistochemical analyses were performed.ResultsLV-mediated GT allowed immunologic reconstitution, although it was suboptimal compared with that seen in wild-type bone marrow (BM)−transplanted OS mice in peripheral blood and hematopoietic organs, such as the BM, thymus, and spleen. We observed in vivo variability in the efficacy of GT correlating with the levels of transduction achieved. Immunoglobulin levels and T-cell repertoire normalized, and gene-corrected mice responded properly to challenges in vivo. Autoimmune manifestations, such as skin infiltration and autoantibodies, dramatically improved in GT mice with a vector copy number/genome higher than 1 in the BM and 2 in the thymus.ConclusionsOur data show that LV-mediated GT for patients with OS significantly ameliorates the immunodeficiency, even in an inflammatory environment. Omenn syndrome (OS) is a rare severe combined immunodeficiency associated with autoimmunity and caused by defects in lymphoid-specific V(D)J recombination. Most patients carry hypomorphic mutations in recombination-activating gene (RAG) 1 or 2. Hematopoietic stem cell transplantation is the standard treatment; however, gene therapy (GT) might represent a valid alternative, especially for patients lacking a matched donor. We sought to determine the efficacy of lentiviral vector (LV)–mediated GT in the murine model of OS (Rag2R229Q/R229Q) in correcting immunodeficiency and autoimmunity. Lineage-negative cells from mice with OS were transduced with an LV encoding the human RAG2 gene and injected into irradiated recipients with OS. Control mice underwent transplantation with wild-type or OS-untransduced lineage-negative cells. Immunophenotyping, T-dependent and T-independent antigen challenge, immune spectratyping, autoantibody detection, and detailed tissue immunohistochemical analyses were performed. LV-mediated GT allowed immunologic reconstitution, although it was suboptimal compared with that seen in wild-type bone marrow (BM)−transplanted OS mice in peripheral blood and hematopoietic organs, such as the BM, thymus, and spleen. We observed in vivo variability in the efficacy of GT correlating with the levels of transduction achieved. Immunoglobulin levels and T-cell repertoire normalized, and gene-corrected mice responded properly to challenges in vivo. Autoimmune manifestations, such as skin infiltration and autoantibodies, dramatically improved in GT mice with a vector copy number/genome higher than 1 in the BM and 2 in the thymus. Our data show that LV-mediated GT for patients with OS significantly ameliorates the immunodeficiency, even in an inflammatory environment.
2017-09-04 | Generation and CRISPR/Cas9 editing of transformed progenitor B cells as a pseudo-physiological system to study DNA repair gene function in V(D)J recombination
Antigen receptor gene assembly is accomplished in developing lymphocytes by the V(D)J recombination reaction, which can be separated into two steps: DNA cleavage by the recombination-activating gene (RAG) nuclease and joining of DNA double strand breaks (DSBs) by components of the nonhomologous end joining (NHEJ) pathway. Deficiencies for NHEJ factors can result in immunodeficiency and a propensity to accumulate genomic instability, thus highlighting the importance of identifying all players in this process and deciphering their functions. Bcl2 transgenic v-Abl kinase-transformed pro-B cells provide a pseudo-physiological cellular system to study V(D)J recombination. Treatment of v-Abl/Bcl2 pro-B cells with the Abl kinase inhibitor Imatinib leads to G1 cell cycle arrest, the rapid induction of Rag1/2 gene expression and V(D)J recombination. In this system, the Bcl2 transgene alleviates Imatinib-induced apoptosis enabling the analysis of induced V(D)J recombination. Although powerful, the use of mouse models carrying the Bcl2 transgene for the generation of v-Abl pro-B cell lines is time and money consuming. Here, we describe a method for generating v-Abl/Bcl2 pro-B cell lines from wild type mice and for performing gene knock-out using episomal CRISPR/Cas9 targeting vectors. Using this approach, we generated distinct NHEJ-deficient pro-B cell lines and quantified V(D)J recombination levels in these cells. Furthermore, this methodology can be adapted to generate pro-B cell lines deficient for any gene suspected to play a role in V(D)J recombination, and more generally DSB repair.
2014-11-24 | Eliminating SCID row: new approaches to SCID
Treatments for patients with SCID by hematopoietic stem cell transplantation (HSCT) have changed this otherwise lethal primary immune deficiency disorder into one with an increasingly good prognosis. SCID has been the paradigm disorder supporting many key advances in the field of HSCT, with first-in-human successes with matched sibling, haploidentical, and matched unrelated donor allogeneic transplantations. Nevertheless, the optimal approaches for HSCT are still being defined, including determining the optimal stem cell sources, the use and types of pretransplantation conditioning, and applications for SCID subtypes associated with radiosensitivity, for patients with active viral infections and for neonates. Alternatively, autologous transplantation after ex vivo gene correction (gene therapy) has been applied successfully to the treatment of adenosine deaminase-deficient SCID and X-linked SCID by vector-mediated gene addition. Gene therapy holds the prospect of avoiding risks of GVHD and would allow each patient to be their own donor. New approaches to gene therapy by gene correction in autologous HSCs using site-specific endonuclease-mediated homology-driven gene repair are under development. With newborn screening becoming more widely adopted to detect SCID patients before they develop complications, the prognosis for SCID is expected to improve further. This chapter reviews recent advances and ongoing controversies in allogeneic and autologous HSCT for SCID.
antibodies
2022-05-19 | Worked to the bone: antibody-based conditioning as the future of transplant biology
Conditioning of the bone marrow prior to haematopoietic stem cell transplant is essential in eradicating the primary cause of disease, facilitating donor cell engraftment and avoiding transplant rejection via immunosuppression. Standard conditioning regimens, typically comprising chemotherapy and/or radiotherapy, have proven successful in bone marrow clearance but are also associated with severe toxicities and high incidence of treatment-related mortality. Antibody-based conditioning is a developing field which, thus far, has largely shown an improved toxicity profile in experimental models and improved transplant outcomes, compared to traditional conditioning. Most antibody-based conditioning therapies involve monoclonal/naked antibodies, such as alemtuzumab for graft-versus-host disease prophylaxis and rituximab for Epstein-Barr virus prophylaxis, which are both in Phase II trials for inclusion in conditioning regimens. Nevertheless, alternative immune-based therapies, including antibody-drug conjugates, radio-labelled antibodies and CAR-T cells, are showing promise in a conditioning setting. Here, we analyse the current status of antibody-based drugs in pre-transplant conditioning regimens and assess their potential in the future of transplant biology.
2019-07-05 | Arthritis in Two Patients With Partial Recombination Activating Gene Deficiency
Autoimmunity is becoming an increasingly recognized complication in patients with primary immunodeficiencies (PIDs), including a variety of combined immune deficiencies such as Recombination Activating Gene (RAG) defects. The approach to treating autoimmunity in PID patients is complex, requiring a balance between immunosuppression and susceptibility to infection. Inflammatory arthritis is a feature of immune dysregulation in many PIDs, and the optimal treatment may differ from first line therapies that usually consist of disease-modifying anti rheumatic drugs (DMARDs). An example of mechanism-based therapy of arthritis in PID uses blockade of IL-6 signaling with tocilizumab for patients with STAT 3 gain-of-function (GOF) mutation and augmented IL-6 pathway. Herein, we describe two PID cases with arthritis who were found to have defects in RAG. One patient with refractory inflammatory arthritis experienced remarkable improvement in symptoms with tocilizumab therapy. Arthritis can be a clinical feature of immune dysregulation in RAG deficiency, and tocilizumab therapy has been suggested to have utility in treatment of arthritis in RAG deficiency.
2011-04-07 | Prevention of bone marrow cell apoptosis and regulation of hematopoiesis by type I IFNs during systemic responses to pneumocystis lung infection.
Abstract We recently demonstrated that lack of type I IFN signaling (IFNAR knockout) in lymphocyte-deficient mice (IFrag−/−) results in bone marrow (BM) failure after Pneumocystis lung infection, whereas lymphocyte-deficient mice with intact IFNAR (RAG−/−) had normal hematopoiesis. In the current work, we performed studies to define further the mechanisms involved in the induction of BM failure in this system. BM chimera experiments revealed that IFNAR expression was required on BM-derived but not stroma-derived cells to prevent BM failure. Signals elicited after day 7 postinfection appeared critical in determining BM cell fate. We observed caspase-8– and caspase-9–mediated apoptotic cell death, beginning with neutrophils. Death of myeloid precursors was associated with secondary oxidative stress, and decreasing colony-forming activity in BM cell cultures. Treatment with N-acetylcysteine could slow the progression of, but not prevent, BM failure. Type I IFN signaling has previously been shown to expand the neutrophil life span and regulate the expression of some antiapoptotic factors. Quantitative RT-PCR demonstrated reduced mRNA abundance for the antiapoptotic factors BCL-2, IAP2, MCL-1, and others in BM cells from IFrag−/− compared with that in BM cells from RAG−/− mice at day 7. mRNA and protein for the proapoptotic cytokine TNF-α was increased, whereas mRNA for the growth factors G-CSF and GM-CSF was reduced. In vivo anti–TNF-α treatment improved precursor cell survival and activity in culture. Thus, we propose that lack of type I IFN signaling results in decreased resistance to inflammation-induced proapoptotic stressors and impaired replenishment by precursors after systemic responses to Pneumocystis lung infection. Our finding may have implications in understanding mechanisms underlying regenerative BM depression/failure during complex immune deficiencies such as AIDS.
cell therapies
2024-04-18 | Antiviral cellular therapy for enhancing T-cell reconstitution before or after hematopoietic stem cell transplantation (ACES): a two-arm, open label phase II interventional trial of pediatric patients with risk factor assessment
Viral infections remain a major risk in immunocompromised pediatric patients, and virus-specific T cell (VST) therapy has been successful for treatment of refractory viral infections in prior studies. We performed a phase II multicenter study (NCT03475212) for the treatment of pediatric patients with inborn errors of immunity and/or post allogeneic hematopoietic stem cell transplant with refractory viral infections using partially-HLA matched VSTs targeting cytomegalovirus, Epstein-Barr virus, or adenovirus. Primary endpoints were feasibility, safety, and clinical responses (>1 log reduction in viremia at 28 days). Secondary endpoints were reconstitution of antiviral immunity and persistence of the infused VSTs. Suitable VST products were identified for 75 of 77 clinical queries. Clinical responses were achieved in 29 of 47 (62%) of patients post-HSCT including 73% of patients evaluable at 1-month post-infusion, meeting the primary efficacy endpoint (>52%). Secondary graft rejection occurred in one child following VST infusion as described in a companion article. Corticosteroids, graft-versus-host disease, transplant-associated thrombotic microangiopathy, and eculizumab treatment correlated with poor response, while uptrending absolute lymphocyte and CD8 T cell counts correlated with good response. This study highlights key clinical factors that impact response to VSTs and demonstrates the feasibility and efficacy of this therapy in pediatric HSCT.
2023-02-07 | Hematopoietic stem cell transplantation for inborn errors of immunity: 30-year single-center experience
Allogeneic hematopoietic stem cell transplantation (allo-HSCT) represents an effective treatment for a variety of inborn errors of immunity (IEI). We report the experience of children affected by IEI who received allo-HSCT over a period of 32 years at IRCCS Istituto Giannina Gaslini, Genoa, Italy. HSCTs were performed in 67 children with IEI. Kaplan-Meier estimates of overall survival (OS) rate at 5 years in the whole group of patients was 83.4% after a median follow-up of 4 years. Median age at transplant was 2.5 years. Eight allo-HSCTs were complicated by either primary or secondary graft failure (GF), the overall incidence of this complication being 10.9%. Incidence of grade 3-4 acute GvHD (aGvHD) was 18.7%, significantly lower in the haploidentical transplant cohort (p = 0.005). Year of transplant (≤2006 vs. >2006) was the main factor influencing the outcome. In fact, a significant improvement in 5-year OS was demonstrated (92.5% >2006 vs. 65% ≤2006, p = 0.049). Frequency of severe aGvHD was significantly reduced in recent years (≤2006 61.5%, vs. >2006 20%, p = 0.027). A significant progress has been the introduction of the TCR αβ/CD19-depleted haploidentical platform, which was associated with the absence of severe aGvHD. However, it was associated with 23.5% incidence of GF. All but one patient experiencing GF in the this specific cohort were successfully retransplanted. In summary, allo-HSCT is confirmed to be an effective treatment for children with IEI, even in the absence of an HLA-matched donor.
2022-02-15 | Bayesian Modeling Immune Reconstitution Apply to CD34+ Selected Stem Cell Transplantation for Severe Combined Immunodeficiency
Severe combined immunodeficiencies (SCIDs) correspond to the most severe form of primary immunodeficiency. Allogeneic hematopoietic stem cell transplantation (HSCT) and gene therapy are curative treatments, depending on the donor's availability and molecular diagnostics. A partially human leukocyte antigen (HLA)-compatible donor used has been developed for this specific HSCT indication in the absence of a matched donor. However, the CD34+ selected process induces prolonged post-transplant T-cell immunodeficiency. The aim here was to investigate a modeling approach to predict the time course and the extent of CD4+ T-cell immune reconstitution after CD34+ selected transplantation. We performed a Bayesian approach based on the age-related changes in thymic output and the cell proliferation/loss model. For that purpose, we defined specific individual covariates from the data collected from 10 years of clinical practice and then evaluated the model's predicted performances and accuracy. We have shown that this Bayesian modeling approach predicted the time course and extent of CD4+ T-cell immune reconstitution after SCID transplantation.
2021-08-27 | Hematopoietic Cell Transplantation for Severe Combined Immunodeficiency Patients: a Japanese Retrospective Study
Hematopoietic cell transplantation (HCT) is a curative therapy for patients with severe combined immunodeficiency (SCID). Here, we conducted a nationwide study to assess the outcome of SCID patients after HCT in Japan.A cohort of 181 SCID patients undergoing their first allogeneic HCT in 1974-2016 was studied by using the Japanese national database (Transplant Registry Unified Management Program, TRUMP).The 10-year overall survival (OS) of the patients who received HCT in 2006-2016 was 67%. Umbilical cord blood (UCB) transplantation was performed in 81 patients (45%). The outcomes of HCT from HLA-matched UCB (n = 21) and matched sibling donors (n = 22) were comparable, including 10-year OS (91% vs. 91%), neutrophil recovery (cumulative incidence at 30 days, 89% vs. 100%), and platelet recovery (cumulative incidence at 60 days, 89% vs. 100%). Multivariate analysis of the patients who received HCT in 2006-2016 demonstrated that the following factors were associated with poor OS: bacterial or fungal infection at HCT (hazard ratio (HR): 3.8, P = 0.006), cytomegalovirus infection prior to HCT (HR: 9.4, P = 0.03), ≥ 4 months of age at HCT (HR: 25.5, P = 0.009), and mismatched UCB (HR: 19.8, P = 0.01).We showed the potential of HLA-matched UCB as a donor source with higher priority for SCID patients. We also demonstrated that early age at HCT without active infection is critical for a better prognosis, highlighting the importance of newborn screening for SCID.
2020-09-29 | Asymptomatic Infant With Atypical SCID and Novel Hypomorphic RAG Variant Identified by Newborn Screening: A Diagnostic and Treatment Dilemma
The T-cell receptor excision circle (TREC) assay was designed to detect T-cell lymphopenia (TCL) in newborns, especially to identify severe combined immunodeficiency (SCID). A spectrum of SCID variants and non-SCID conditions that present with TCL are being discovered by SCID newborn screening (NBS) with increasing frequency. Decisions for treatment are influenced by underlying genetic abnormalities. Recombination-activating gene (RAG) deficiency is one the most common causes of classical and atypical SCID and other conditions with immune dysregulation. This case report aims to highlight how NBS can expedite identification of an asymptomatic newborn with a novel hypomorphic RAG variant and a controversial immune phenotype that required in depth immune evaluation to confirm that the abnormal RAG genotype is linked to the disease and justify definitive therapy with hematopoietic stem cell transplantation (HSCT). Following identification of newborns with out of range TREC levels, the diagnostic approach followed at our center includes lymphocyte subset enumeration by flow-cytometry, quantitative serum immunoglobulin levels, lymphocyte proliferation upon mitogen stimulation and next generation DNA sequencing to search for genetic variants associated with SCID. For babies in whom novel RAG gene variants are detected, we also test for immune biomarkers, and if feasible, analyze the recombinase activity of the novel RAG variants by functional assays and T and B-cell receptor repertoire. We identified and validated pathogenicity for compound heterozygous hypomorphic RAG1 variants in an asymptomatic newborn with undetectable TRECs and controversial immunological phenotype with severe TCL, but normal B cell count and lymphocyte proliferation upon mitogen stimulation. Due to the potential for severe complications with infection and immune dysregulation, the patient underwent a matched unrelated HSCT and is doing well 15 months post-HSCT. In conclusion, partial RAG deficiency can be detected by NBS in some cases such as ours. In case of an atypical immune phenotype and novel RAG gene variants, in vivo and in vitro studies are needed to confirm causative association and expedite treatment with HSCT due to risk of serious infection and non-infectious complications.
gene therapies
2022-07-13 | Genetically Corrected RAG2-SCID Human Hematopoietic Stem Cells Restore V(D)J-Recombinase and Rescue Lymphoid Deficiency
ABSTRACT Recombination-activating genes ( RAG1 and RAG2 ) are critical in lymphoid cell development and function for initiating the V(D)J-recombination process to generate polyclonal lymphocytes with broad antigen-specificity. Clinical manifestations of defective RAG1/2 genes range from immune dysregulation to severe combined immunodeficiencies (SCID), causing life-threatening infections and death early in life in the absence of hematopoietic cell transplantation (HCT). Haploidentical HCT without myeloablative conditioning carries a high risk of graft failure and incomplete immune reconstitution. The RAG complex is only expressed during the G0-G1 phases of the cell cycle at the early stages of T and B cell development, underscoring that a direct gene correction would capture the precise temporal expression of the endogenous gene, is a promising therapeutic approach for RAG1/2 -deficiencies. Here, we report a feasibility study using the CRISPR/Cas9-based “universal gene-correction” approach for the RAG2 locus in human hematopoietic stem/progenitor cells (HSPCs) in healthy donors and one RAG2 -SCID patient. V(D)J recombinase activity was restored following gene correction of RAG2 -SCID-derived HSPCs, resulting in the development of TCR αβ and γδ CD3 + cells and single-positive CD4 + and CD8 + lymphocytes. TCR repertoire analysis indicated a normal distribution of the CDR3 length and preserved usage of distal TRAV genes. We confirmed in vivo rescue of B-cell development, with normal IgM surface expression and a significant decrease in CD56 bright NK cells. Together, we provide specificity, toxicity, and efficacy data supporting the development of a gene-correction therapy to benefit all RAG2 -deficient patients. KEY POINTS Human hematopoietic stem cells can be corrected to restore endogenous RAG2 gene expression while preserving durable engraftment potential. Gene-corrected RAG2 locus restores V(D)J recombination in RAG2 -SCID patient stem cells, promoting T and B-cells’ receptor formation.
2020-02-01 | Intrathymic adeno-associated virus gene transfer rapidly restores thymic function and long-term persistence of gene-corrected T cells
Patients with T-cell immunodeficiencies are generally treated with allogeneic hematopoietic stem cell transplantation, but alternatives are needed for patients without matched donors. An innovative intrathymic gene therapy approach that directly targets the thymus might improve outcomes.We sought to determine the efficacy of intrathymic adeno-associated virus (AAV) serotypes to transduce thymocyte subsets and correct the T-cell immunodeficiency in a zeta-associated protein of 70 kDa (ZAP-70)-deficient murine model.AAV serotypes were injected intrathymically into wild-type mice, and gene transfer efficiency was monitored. ZAP-70-/- mice were intrathymically injected with an AAV8 vector harboring the ZAP70 gene. Thymus structure, immunophenotyping, T-cell receptor clonotypes, T-cell function, immune responses to transgenes and autoantibodies, vector copy number, and integration were evaluated.AAV8, AAV9, and AAV10 serotypes all transduced thymocyte subsets after in situ gene transfer, with transduction of up to 5% of cells. Intrathymic injection of an AAV8-ZAP-70 vector into ZAP-70-/- mice resulted in a rapid thymocyte differentiation associated with the development of a thymic medulla. Strikingly, medullary thymic epithelial cells expressing the autoimmune regulator were detected within 10 days of gene transfer, correlating with the presence of functional effector and regulatory T-cell subsets with diverse T-cell receptor clonotypes in the periphery. Although thymocyte reconstitution was transient, gene-corrected peripheral T cells harboring approximately 1 AAV genome per cell persisted for more than 40 weeks, and AAV vector integration was detected.Intrathymic AAV-transduced progenitors promote a rapid restoration of the thymic architecture, with a single wave of thymopoiesis generating long-term peripheral T-cell function.
2018-09-01 | Efficacy of lentivirus-mediated gene therapy in an Omenn syndrome recombination-activating gene 2 mouse model is not hindered by inflammation and immune dysregulation
BackgroundOmenn syndrome (OS) is a rare severe combined immunodeficiency associated with autoimmunity and caused by defects in lymphoid-specific V(D)J recombination. Most patients carry hypomorphic mutations in recombination-activating gene (RAG) 1 or 2. Hematopoietic stem cell transplantation is the standard treatment; however, gene therapy (GT) might represent a valid alternative, especially for patients lacking a matched donor.ObjectiveWe sought to determine the efficacy of lentiviral vector (LV)–mediated GT in the murine model of OS (Rag2R229Q/R229Q) in correcting immunodeficiency and autoimmunity.MethodsLineage-negative cells from mice with OS were transduced with an LV encoding the human RAG2 gene and injected into irradiated recipients with OS. Control mice underwent transplantation with wild-type or OS-untransduced lineage-negative cells. Immunophenotyping, T-dependent and T-independent antigen challenge, immune spectratyping, autoantibody detection, and detailed tissue immunohistochemical analyses were performed.ResultsLV-mediated GT allowed immunologic reconstitution, although it was suboptimal compared with that seen in wild-type bone marrow (BM)−transplanted OS mice in peripheral blood and hematopoietic organs, such as the BM, thymus, and spleen. We observed in vivo variability in the efficacy of GT correlating with the levels of transduction achieved. Immunoglobulin levels and T-cell repertoire normalized, and gene-corrected mice responded properly to challenges in vivo. Autoimmune manifestations, such as skin infiltration and autoantibodies, dramatically improved in GT mice with a vector copy number/genome higher than 1 in the BM and 2 in the thymus.ConclusionsOur data show that LV-mediated GT for patients with OS significantly ameliorates the immunodeficiency, even in an inflammatory environment. Omenn syndrome (OS) is a rare severe combined immunodeficiency associated with autoimmunity and caused by defects in lymphoid-specific V(D)J recombination. Most patients carry hypomorphic mutations in recombination-activating gene (RAG) 1 or 2. Hematopoietic stem cell transplantation is the standard treatment; however, gene therapy (GT) might represent a valid alternative, especially for patients lacking a matched donor. We sought to determine the efficacy of lentiviral vector (LV)–mediated GT in the murine model of OS (Rag2R229Q/R229Q) in correcting immunodeficiency and autoimmunity. Lineage-negative cells from mice with OS were transduced with an LV encoding the human RAG2 gene and injected into irradiated recipients with OS. Control mice underwent transplantation with wild-type or OS-untransduced lineage-negative cells. Immunophenotyping, T-dependent and T-independent antigen challenge, immune spectratyping, autoantibody detection, and detailed tissue immunohistochemical analyses were performed. LV-mediated GT allowed immunologic reconstitution, although it was suboptimal compared with that seen in wild-type bone marrow (BM)−transplanted OS mice in peripheral blood and hematopoietic organs, such as the BM, thymus, and spleen. We observed in vivo variability in the efficacy of GT correlating with the levels of transduction achieved. Immunoglobulin levels and T-cell repertoire normalized, and gene-corrected mice responded properly to challenges in vivo. Autoimmune manifestations, such as skin infiltration and autoantibodies, dramatically improved in GT mice with a vector copy number/genome higher than 1 in the BM and 2 in the thymus. Our data show that LV-mediated GT for patients with OS significantly ameliorates the immunodeficiency, even in an inflammatory environment.
2017-09-04 | Generation and CRISPR/Cas9 editing of transformed progenitor B cells as a pseudo-physiological system to study DNA repair gene function in V(D)J recombination
Antigen receptor gene assembly is accomplished in developing lymphocytes by the V(D)J recombination reaction, which can be separated into two steps: DNA cleavage by the recombination-activating gene (RAG) nuclease and joining of DNA double strand breaks (DSBs) by components of the nonhomologous end joining (NHEJ) pathway. Deficiencies for NHEJ factors can result in immunodeficiency and a propensity to accumulate genomic instability, thus highlighting the importance of identifying all players in this process and deciphering their functions. Bcl2 transgenic v-Abl kinase-transformed pro-B cells provide a pseudo-physiological cellular system to study V(D)J recombination. Treatment of v-Abl/Bcl2 pro-B cells with the Abl kinase inhibitor Imatinib leads to G1 cell cycle arrest, the rapid induction of Rag1/2 gene expression and V(D)J recombination. In this system, the Bcl2 transgene alleviates Imatinib-induced apoptosis enabling the analysis of induced V(D)J recombination. Although powerful, the use of mouse models carrying the Bcl2 transgene for the generation of v-Abl pro-B cell lines is time and money consuming. Here, we describe a method for generating v-Abl/Bcl2 pro-B cell lines from wild type mice and for performing gene knock-out using episomal CRISPR/Cas9 targeting vectors. Using this approach, we generated distinct NHEJ-deficient pro-B cell lines and quantified V(D)J recombination levels in these cells. Furthermore, this methodology can be adapted to generate pro-B cell lines deficient for any gene suspected to play a role in V(D)J recombination, and more generally DSB repair.
2014-11-24 | Eliminating SCID row: new approaches to SCID
Treatments for patients with SCID by hematopoietic stem cell transplantation (HSCT) have changed this otherwise lethal primary immune deficiency disorder into one with an increasingly good prognosis. SCID has been the paradigm disorder supporting many key advances in the field of HSCT, with first-in-human successes with matched sibling, haploidentical, and matched unrelated donor allogeneic transplantations. Nevertheless, the optimal approaches for HSCT are still being defined, including determining the optimal stem cell sources, the use and types of pretransplantation conditioning, and applications for SCID subtypes associated with radiosensitivity, for patients with active viral infections and for neonates. Alternatively, autologous transplantation after ex vivo gene correction (gene therapy) has been applied successfully to the treatment of adenosine deaminase-deficient SCID and X-linked SCID by vector-mediated gene addition. Gene therapy holds the prospect of avoiding risks of GVHD and would allow each patient to be their own donor. New approaches to gene therapy by gene correction in autologous HSCs using site-specific endonuclease-mediated homology-driven gene repair are under development. With newborn screening becoming more widely adopted to detect SCID patients before they develop complications, the prognosis for SCID is expected to improve further. This chapter reviews recent advances and ongoing controversies in allogeneic and autologous HSCT for SCID.
antibodies
2022-05-19 | Worked to the bone: antibody-based conditioning as the future of transplant biology
Conditioning of the bone marrow prior to haematopoietic stem cell transplant is essential in eradicating the primary cause of disease, facilitating donor cell engraftment and avoiding transplant rejection via immunosuppression. Standard conditioning regimens, typically comprising chemotherapy and/or radiotherapy, have proven successful in bone marrow clearance but are also associated with severe toxicities and high incidence of treatment-related mortality. Antibody-based conditioning is a developing field which, thus far, has largely shown an improved toxicity profile in experimental models and improved transplant outcomes, compared to traditional conditioning. Most antibody-based conditioning therapies involve monoclonal/naked antibodies, such as alemtuzumab for graft-versus-host disease prophylaxis and rituximab for Epstein-Barr virus prophylaxis, which are both in Phase II trials for inclusion in conditioning regimens. Nevertheless, alternative immune-based therapies, including antibody-drug conjugates, radio-labelled antibodies and CAR-T cells, are showing promise in a conditioning setting. Here, we analyse the current status of antibody-based drugs in pre-transplant conditioning regimens and assess their potential in the future of transplant biology.
2019-07-05 | Arthritis in Two Patients With Partial Recombination Activating Gene Deficiency
Autoimmunity is becoming an increasingly recognized complication in patients with primary immunodeficiencies (PIDs), including a variety of combined immune deficiencies such as Recombination Activating Gene (RAG) defects. The approach to treating autoimmunity in PID patients is complex, requiring a balance between immunosuppression and susceptibility to infection. Inflammatory arthritis is a feature of immune dysregulation in many PIDs, and the optimal treatment may differ from first line therapies that usually consist of disease-modifying anti rheumatic drugs (DMARDs). An example of mechanism-based therapy of arthritis in PID uses blockade of IL-6 signaling with tocilizumab for patients with STAT 3 gain-of-function (GOF) mutation and augmented IL-6 pathway. Herein, we describe two PID cases with arthritis who were found to have defects in RAG. One patient with refractory inflammatory arthritis experienced remarkable improvement in symptoms with tocilizumab therapy. Arthritis can be a clinical feature of immune dysregulation in RAG deficiency, and tocilizumab therapy has been suggested to have utility in treatment of arthritis in RAG deficiency.
2011-04-07 | Prevention of bone marrow cell apoptosis and regulation of hematopoiesis by type I IFNs during systemic responses to pneumocystis lung infection.
Abstract We recently demonstrated that lack of type I IFN signaling (IFNAR knockout) in lymphocyte-deficient mice (IFrag−/−) results in bone marrow (BM) failure after Pneumocystis lung infection, whereas lymphocyte-deficient mice with intact IFNAR (RAG−/−) had normal hematopoiesis. In the current work, we performed studies to define further the mechanisms involved in the induction of BM failure in this system. BM chimera experiments revealed that IFNAR expression was required on BM-derived but not stroma-derived cells to prevent BM failure. Signals elicited after day 7 postinfection appeared critical in determining BM cell fate. We observed caspase-8– and caspase-9–mediated apoptotic cell death, beginning with neutrophils. Death of myeloid precursors was associated with secondary oxidative stress, and decreasing colony-forming activity in BM cell cultures. Treatment with N-acetylcysteine could slow the progression of, but not prevent, BM failure. Type I IFN signaling has previously been shown to expand the neutrophil life span and regulate the expression of some antiapoptotic factors. Quantitative RT-PCR demonstrated reduced mRNA abundance for the antiapoptotic factors BCL-2, IAP2, MCL-1, and others in BM cells from IFrag−/− compared with that in BM cells from RAG−/− mice at day 7. mRNA and protein for the proapoptotic cytokine TNF-α was increased, whereas mRNA for the growth factors G-CSF and GM-CSF was reduced. In vivo anti–TNF-α treatment improved precursor cell survival and activity in culture. Thus, we propose that lack of type I IFN signaling results in decreased resistance to inflammation-induced proapoptotic stressors and impaired replenishment by precursors after systemic responses to Pneumocystis lung infection. Our finding may have implications in understanding mechanisms underlying regenerative BM depression/failure during complex immune deficiencies such as AIDS.
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Drug Discovery Landscape
2 orphan drug designations for Severe combined immunodeficiency due to complete RAG1/2 deficiency.
2 orphan drug designations for Severe combined immunodeficiency due to complete RAG1/2 deficiency.
Drug | Therapy type | Orphan designation | Clinical trial status | Sponsor |
|---|---|---|---|---|
Autologous hematopoietic cells genetically modified with a lentiviral vector containing the human RAG2 gene | gene therapies | EMA | — | Leiden University Medical Center |
Autologous CD34+ cells transduced with a lentiviral vector containing the human RAG1 gene | gene therapies | EMA | Videja B.V. |
“Terminated” – programs with discontinued clinical trials, or with no updates reported for 5 years after completion or 12 years after the last trial started.
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