Deficient Severe Combined Immunodeficiency Research Articles

Treatment with Elapegademase Restores Immunity in Infants with Adenosine Deaminase Deficient Severe Combined Immunodeficiency

PurposePatients with adenosine deaminase 1 deficient severe combined immunodeficiency (ADA-SCID) are initially treated with enzyme replacement therapy (ERT) with polyethylene glycol-modified (PEGylated) ADA while awaiting definitive treatment with hematopoietic stem cell transplant (HSCT) or gene therapy. Beginning in 1990, ERT was performed with PEGylated bovine intestinal ADA (ADAGEN®). In 2019, a PEGylated recombinant bovine ADA (Revcovi®) replaced ADAGEN following studies in older patients previously treated with ADAGEN for many years. There are limited longitudinal data on ERT-naïve newborns treated with Revcovi.MethodsWe report our clinical experience with Revcovi as initial bridge therapy in three newly diagnosed infants with ADA-SCID, along with comprehensive biochemical and immunologic data.ResultsRevcovi was initiated at twice weekly dosing (0.2 mg/kg intramuscularly), and monitored by following plasma ADA activity and the concentration of total deoxyadenosine nucleotides (dAXP) in erythrocytes. All patients rapidly achieved a biochemically effective level of plasma ADA activity, and red cell dAXP were eliminated within 2–3 months. Two patients reconstituted B-cells and NK-cells within the first month of ERT, followed by naive T-cells one month later. The third patient reconstituted all lymphocyte subsets within the first month of ERT. One patient experienced declining lymphocyte counts with improvement following Revcovi dose escalation. Two patients developed early, self-resolving thrombocytosis, but no thromboembolic events occurred.ConclusionRevcovi was safe and effective as initial therapy to restore immune function in these newly diagnosed infants with ADA-SCID, however, time course and degree of reconstitution varied. Revcovi dose may need to be optimized based on immune reconstitution, clinical status, and biochemical data.

Purine Nucleoside Phosphorylase Deficient Severe Combined Immunodeficiencies: A Case Report and Systematic Review (1975-2022).

Purine nucleoside phosphorylase deficient severe combined immunodeficiency (PNP SCID) is one of the rare autosomal recessive primary immunodeficiency disease, and the data on epidemiology and outcome are limited. We report the successful management of a child with PNP SCID and present a systematic literature review of published case reports, case series, and cohort studies on PNP SCID listed in PubMed, Web of Science, and Scopus from 1975 until March 2022. Forty-one articles were included from the 2432 articles retrieved and included 100 PNP SCID patients worldwide. Most patients presented with recurrent infections, hypogammaglobulinaemia, autoimmune manifestations, and neurological deficits. There were six reported cases of associated malignancies, mainly lymphomas. Twenty-two patients had undergone allogeneic hematopoietic stem cell transplantation with full donor chimerism seen mainly in those receiving matched sibling donors and/or conditioning chemotherapy before the transplant. This research provides a contemporary, comprehensive overview on clinical manifestations, epidemiology, genotype mutations, and transplant outcome of PNP SCID. These data highlight the importance of screening for PNP SCID in cases presented with recurrent infections, hypogammaglobulinaemia, and neurological deficits.

Treatment of Omenn syndrome using multiple immunosuppressive strategies: a case series

Introduction: Omenn syndrome represents a therapeutic challenge as a state of florid immune dysregulation born out of autoreactive oligoclonal T cells due to hypomorphic variants in genes associated with severe combined immunodeficiency (SCID).Aims: To describe the therapeutic strategies used in the care of three patients with Omenn syndrome from 2013 to 2022. All had negative maternal engraftment studies and received immunosuppression to control autoreactive T cells. All patients ultimately received myeloablative conditioning with anti-thymocyte globulin (ATG), busulfan, and fludarabine for transplant. All patients are currently alive and well.Case 1: 2-month-old female with adenosine deaminase (ADA)-deficient SCID on pegylated ADA replacement developed respiratory distress, rash, and diarrhea in the setting of rising CD3+/CD4+/CD45RO+ cell count. Treated with high-dose systemic steroids. Due to continued CD3+ increase, systemic tacrolimus was added. She clinically improved and underwent matched unrelated donor cord blood transplant at 5 months of age.Case 2: A male with RAG1-SCID developed generalized erythroderma and rapidly rising CD3+/CD4+/CD45RO+ cell and absolute eosinophil counts soon after birth. Systemic steroids were given with clinical improvement. With taper of steroid, ATG 1 mg/kg was given. Initially, the absolute lymphocyte count (ALC) improved; however, within 5 days, his rash worsened and ALC rose. This necessitated re-initiation of high-dose steroids and addition of tacrolimus until matched related donor bone marrow transplant (MRD BMT) at 2 months old.Case 3: 9-day-old male with RAG1-SCID developed diffuse maculopapular rash, lymphadenopathy, and elevated memory T cells and eosinophils. Initiated high-dose systemic steroids and cyclosporine A (CSA) with quick clinical improvement. CSA discontinued due to toxicity and rising ALC and eosinophils. Given ATG 3 mg/kg/dose for 4 doses over 2 weeks with pattern of quick drop then rapid rise in ALC. Treated with steroids and tacrolimus until MRD BMT at 2 months old. ConclusionsWe describe consistent disease control with immunosuppression by systemic steroids and tacrolimus prior to transplant and suggest ATG as a potential adjunctive consideration in poorly-controlled disease. A growing body of knowledge and experience in optimal Omenn syndrome treatment strategies is imperative to improving outcomes.

Early immune reconstitution in an infant with adenosine deaminase deficient severe combined immunodeficiency started on enzyme replacement therapy

Severe Combined Immunodeficiency (SCID) due to adenosine deaminase (ADA) deficiency is an inborn error of immunity resulting in the accumulation of adenosine and deoxyadenosine leading to a T-B-NK-phenotype. Enzyme Replacement Therapy with Elapegademase-IvIr is typically used as a bridge prior to undergoing definitive treatment with HSCT or HSC-GT.We report a full-term female infant born to Caucasian parents. Immediate newborn course was unremarkable. She had two borderline newborn screens (NBS) for SCID. There was no consanguinity or family history of immunodeficiency. Physical exam was normal except for absent tonsils. She had profound lymphopenia (Absolute Lymphocyte Count of 210 cells/mL), and initial lymphocyte enumeration showed low CD3 cells (169/mL), decreased CD19 cells (6/mL) and CD16/56+ cells (26/mL) consistent with a T-B-NK- SCID. There was no maternal engraftment. Immunoglobulin studies showed normal IgG (325) with low IgM and IgA. Mitogen proliferation to phytohemagglutinin (PHA) was significantly low (10,200 CPM).A SCID genetics panel revealed two pathogenic variants in ADA (p.Glu319fs and p.Arg149Trp). Biochemical testing confirmed absent ADA activity and elevated total deoxyadenosine nucleotides (dAXP) of 40.3% in RBCs (normally undetectable), consistent with the diagnosis of ADA-SCID. She was promptly started on ERT twice weekly and developed full immune reconstitution of her T-cells, B-cells and NK-cells after 21 days. At that time, her dAXP remained elevated at 10%. Her T-cell function also normalized (PHA 239,562 CPM).We report an infant with ADA-SCID who had two borderline NBS results and developed full immune reconstitution 3 weeks after starting ERT. This is unusual since thymopoiesis typically requires 60–90 days for T-cell reconstitution. While B and NK immune reconstitution typically occurs early, early T-cell numbers lag behind, especially while dAXP levels remain measurable. Both genetic variants in this patient are severe, but somatic mosaicism with reversion of the Arg149Trp point mutation might account for rapid T-cell recovery; further T-cell analysis is planned to assess this possibility. This child is the first case of SCID diagnosed in North Carolina following a borderline NBS, as opposed to abnormal, reinforcing the utility of highly-sensitive TREC thresholds for identification of at-risk infants. [Display omitted] [Display omitted]

PEGylated Recombinant Adenosine Deaminase Maintains Detoxification and Lymphocyte Counts in Patients with ADA-SCID

PurposeMetabolic detoxification with enzyme replacement therapy (ERT) promotes immune recovery in patients with adenosine deaminase (ADA)–deficient severe combined immunodeficiency (ADA-SCID). Elapegademase is a PEGylated recombinant bovine ADA ERT developed to replace the now-discontinued bovine-derived pegademase. This study was a 1-way crossover from pegademase to elapegademase in 7 patients with ADA-SCID to assess efficacy and safety outcomes for elapegademase.MethodsAfter once-weekly pegademase dosage was adjusted to achieve therapeutic metabolic detoxification and trough ADA activity, patients transitioned to a bioequivalent dose of elapegademase. Maintenance of metabolic detoxification and adequate ADA activity were evaluated periodically.ResultsOne patient withdrew after 2 doses of an early elapegademase formulation due to injection-site pain caused by EDTA. The 6 remaining patients completed 71−216 weeks of elapegademase therapy with a formulation that did not contain EDTA. In these patients, elapegademase improved ADA activity compared with pegademase and maintained metabolic detoxification. Total lymphocyte counts increased for all completer patients from between 1.2- and 2.1-fold at the end of study compared with baseline. Elapegademase had a comparable safety profile to pegademase; no patient developed a severe infectious complication. Three patients had transient, non-neutralizing antibodies to pegademase, elapegademase, and/or polyethylene glycol ≤ 47 weeks of treatment without effect on trough plasma ADA activity or trough erythrocyte deoxyadenosine nucleotide levels.ConclusionElapegademase was safe, well tolerated, achieved stable trough plasma ADA activity with weekly dosing, was effective in maintaining metabolic detoxification, and was associated with maintenance or improvements in lymphocyte counts compared with pegademase therapy in patients with ADA-SCID.

Gene Therapy Hits Its Stride in the Clinic

Gene Therapy Hits Its Stride in the Clinic

Hematopoietic Cell Transplantation for Adenosine Deaminase Severe Combined Immunodeficiency—Improved Outcomes in the Modern Era

Current treatment for adenosine deaminase (ADA)-deficient severe combined immunodeficiency (SCID) includes enzyme replacement therapy (ERT), allogeneic hematopoietic stem cell transplant (HSCT), or ex vivo corrected autologous hematopoietic stem cell gene therapy. Historic data show HSCT survival is superior using unconditioned matched sibling and family compared to matched unrelated and haploidentical donors. Recent improvement in HSCT outcomes prompted us to retrospectively examine HSCT survival and long-term graft function in ADA-SCID transplanted at our center. Thirty-three ADA-deficient patients received HSCT between 1989 and 2020, with follow-up data to January 2021. Chemotherapy conditioning regimens were defined as myeloablative (MAC—busulfan/cyclophosphamide), reduced-toxicity myeloablative (RT-MAC—treosulfan-based, since 2007), or no conditioning. Serotherapy used included alemtuzumab (with or without other conditioning agents) or antithymocyte globulin (ATG). ERT was introduced routinely in 2010 until commencement of conditioning. Median age at HSCT was 3.2 (0.8–99.8) months. Twenty-one (63.6%) received stem cells from unrelated or haploidentical donors. Seventeen (51.5%) received chemotherapy conditioning and 16 (48.5%) received alemtuzumab. Median follow-up was 7.5 (0.8–25.0) years. Overall survival (OS) and event-free survival (EFS) at 8 years were 90.9% (95% CI: 79.7–100.0%) and 79% (55–91%), respectively. OS after 2007 (n = 21) was 100% vs 75% before 2007 (n = 12) (p = 0.02). Three (9.1%) died after HSCT: two from multiorgan failure and one from unexplained encephalopathy. There were no deaths after 2007, among those who received ERT and treosulfan-based conditioning pre-HSCT. Ten (30.3%) developed acute GvDH (3 grade II, 2 grade III); no chronic GvHD was observed. In the modern era, conditioned HSCT with MUD has a favorable outcome for ADA-deficient patients.

Rescue of Murine IL-7 Receptor Deficiency with Human IL-7 Receptor Gene Therapy

▪In humans, interleukin 7 (IL-7) receptor (IL-7R) deficiency causes approximately 10% of cases of severe combined immunodeficiency (SCID). IL-7R deficient SCID is a T-B+NK+ SCID and is caused by autosomal recessive deficiency of the IL-7R alpha chain gene (IL7R). IL-7R is a heterodimeric receptor comprised of the alpha chain and the IL-2 receptor common gamma chain (IL2RG). In both mouse and human, IL-7R is a marker of the common lymphoid progenitor cell, and IL-7 signaling leads to STAT5 phosphorylation and proliferation of developing T and B cells. Mice lacking IL7R, Il7r -/-, lack both T and B cells (Peschon, JJ, et al. J Exp Med. 1994). T cells do not progress to TCR beta chain rearrangement and B cell development is halted at the pre-pro-B cell stage. Similar to the mouse, IL-7 signaling in humans is required for T cell receptor beta gene rearrangement and T cell maintenance, however humans lacking IL-7R can develop B cells.A prior attempt to rescue murine IL-7R deficiency utilized a retroviral vector (mouse stem cell virus, MSCV), the MSCV retroviral promoter, and the murine Il7r gene (Jiang, Q, et al. Gene Therapy. 2005). This strategy did restore T cells and had variable restoration of B cells. However, retroviral-based gene addition of Il7r led to a myeloproliferative condition with significant neutrophilia and splenomegaly. Transduced bone marrow cells formed myeloid progenitors in response to IL-7 in vitro. We evaluated a novel gene therapy for IL-7R deficient SCID that utilizes the human IL7R gene. To prevent lineage skewing, we sought to limit ectopic expression of IL7R in non-lymphoid cells by utilizing the endogenous enhancers and promoters of IL7R. These sequences were identified as sites of high sequence conservation across species and DNA accessibility/hypersensitivity (DHS) in human lymphocytes. We are testing these sequences alone or in combination with the constitutive phosphoglycerate kinase promoter (PGK) in VSV-G pseudotyped lentiviral vectors (LV): vPGK_DHS_hIL7R and vDHS_hIL7R. Here we present the first data evaluating the ability of the human IL-7R protein to functionally replace the murine IL-7R protein and the ability of IL7R gene addition to rescue the murine Il7r -/- immunodeficient phenotype in vivo.Transduction of Il7r -/- bone marrow cells with IL7R encoding LV rescued the formation of lymphocyte precursors from murine bone marrow cells in colony forming unit (CFU) assays (pre-B CFU with human IL-7), with the most robust response seen with vPGK_DHS_hIL7R. Mouse bone marrow from Il7r -/- animals transduced ex vivo engrafted in lethally irradiated (8 Gy) Il7r -/-oppositegender recipients and there were no significant aberrations in absolute neutrophil count, hemoglobin or platelet count. Absolute lymphocyte counts in mice receiving transduced Il7r -/-bone marrow cells was higher (mean 2555/μL) than in mice receiving untransduced bone marrow (mean 1410/μL). The proportion of leukocytes that were T cells was 4.2-fold and 9.8-fold higher at 1 and 2 months post-transplant, respectively. B cells were only seen in mice receiving vPGK_DHS_hIL7R: 7.4% of leukocytes versus 1.5% in controls. A reciprocal decrease in the fraction of Gr1+ cells (neutrophils and monocytes) was seen at two months post-transplant in transduced marrow recipients compared to untransduced controls: 36.5% versus 63% Gr1+, respectively. Lymphocyte subsets are being further analyzed, bone marrow and thymic lymphoid precursors assessed, and T and B cell function in response to immunizations are in progress. Further evaluation in human derived IL7R deficient human cells is warranted.For individuals with IL-7R deficient SCID, but no HLA matched hematopoietic stem cell (HSC) donor, there is a difficult choice between the risks of GVHD with a mismatched HSC donor and supportive care with the hope of identifying a matched HSC donor in the future. In immunodeficiencies however age and serious infection are both associated with increased mortality (Pai, SY, et al. NJEM. 2014). This novel approach to IL7R gene replacement has the potential to be a therapeutic and expedient option for those without a matched donor. Additionally, this would be an ideal disorder for HSC conditioning with less toxic, HSC-targeted strategies given gene corrected lymphocytes and progenitors will preferentially expand post-transplant. DisclosuresRivella: Disc Medicine: Consultancy, Membership on an entity's Board of Directors or advisory committees; Keros Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene Corporation: Consultancy; Ionis Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees; MeiraGTx: Consultancy, Membership on an entity's Board of Directors or advisory committees; Forma Theraputics: Consultancy; Incyte: Consultancy.

Long-Term Immune Recovery After Hematopoietic Stem Cell Transplantation for ADA Deficiency: a Single-Center Experience

Unconditioned hematopoietic stem cell transplantation (HSCT) is the recommended treatment for patients with adenosine deaminase (ADA)-deficient severe combined immunodeficiency with an HLA-matched sibling donor (MSD) or family donor (MFD). Improved overall survival (OS) has been reported compared to the use of unrelated donors, and previous studies have demonstrated that adequate cellular and humoral immune recovery can be achieved even in the absence of conditioning. Detailed insight of the long-term outcome is still limited. We aim to address this by studying a large single-center cohort of 28 adenosine deaminase-deficient patients who underwent a total of 31 HSCT procedures, of which more than half were unconditioned. We report an OS of 85.7% and event-free survival of 71% for the entire cohort, with no statistically significant differences after procedures using related or unrelated HLA-matched donors. We find that donor engraftment in the myeloid compartment is significantly diminished in unconditioned procedures, which typically use a MSD or MFD. This is associated with poor metabolic correction and more frequent failure to discontinue immunoglobulin replacement therapy. Approximately one in four patients receiving an unconditioned procedure required a second procedure, whereas the use of reduced intensity conditioning (RIC) prior to allogeneic transplantation improves the long-term outcome by achieving better myeloid engraftment, humoral immune recovery, and metabolic correction. Further longitudinal studies are needed to optimize future management and guidelines, but our findings support a potential role for the routine use of RIC in most ADA-deficient patients receiving an HLA-identical hematopoietic stem cell transplant, even when a MSD or MFD is available.

Nonconditioned ADA-SCID gene therapy reveals ADA requirement in the hematopoietic system and clonal dominance of vector-marked clones

Two patients with adenosine deaminase (ADA)-deficient severe combined immunodeficiency (ADA-SCID) received stem cell-based gene therapy (SCGT) using GCsapM-ADA retroviral vectors without preconditioning in 2003 and 2004. The first patient (Pt1) was treated at 4.7 years old, and the second patient (Pt2), who had previously received T cell gene therapy (TCGT), was treated at 13 years old. More than 10 years after SCGT, T cells showed a higher vector copy number (VCN) than other lineages. Moreover, the VCN increased with differentiation toward memory T and B cells. The distribution of vector-marked cells reflected variable levels of ADA requirements in hematopoietic subpopulations. Although neither patient developed leukemia, clonal expansion of SCGT-derived clones was observed in both patients. The use of retroviral vectors yielded clonal dominance of vector-marked clones, irrespective of the lack of leukemic changes. Vector integration sites common to all hematopoietic lineages suggested the engraftment of gene-marked progenitors in Pt1, who showed severe osteoblast (OB) insufficiency compared to Pt2, which might cause a reduction in the stem/progenitor cells in the bone marrow (BM). The impaired BM microenvironment due to metabolic abnormalities may create space for the engraftment of vector-marked cells in ADA-SCID, despite the lack of preconditioning.

PPM6 Cost-Effectiveness and Reimbursement of CELL and GENE Therapies: A Review

Cell and gene therapy products offer potential curative effects to chronic but are imbedded with data uncertainty and high-costs. New reimbursement models are emerging, that serve as a catalyst for adoption of cell and gene therapies in the future. This research aims to review the cost-effectiveness evidence for ex vivo gene therapy Strimvelis, and CAR T-cell therapies Kymriah (Tisagenlecleucel), Yescarta (Axicabtagene Ciloleucel) and explore the emerging reimbursement models. Pubmed, MEDLINE and Cochrane Library database were searched to December 2019 for (i) ex vivo gene therapy for adenosine deaminase deficiency severe combined immunodeficiency (Strimvelis) and CAR T-cell therapies (ii) tisagenlecleucel (Kymriah) and (iii) axicabtagene ciloleucel (Yescarta) and (iv) reimbursement models for cell and gene therapies. A total of 13 articles were identified as relevant for full-text screening: 8 (66%) analysed cost-effectiveness of Strimvelis, Kymriah and Yescarta in a NHS healthcare setting. The cost per quality adjusted life year (QALY) estimates were highly variable due to uncertainty in the data. New reimbursement models are set to accommodate future high-cost of cell and gene therapy with data uncertainty. Proposed managed access agreements (MMA) encourage collaboration between NHS England and the manufacturer to manage the risks.

Successful Preclinical Development of Gene Therapy for Recombinase-Activating Gene-1-Deficient SCID

Recombinase-activating gene-1 (RAG1)-deficient severe combined immunodeficiency (SCID) patients lack B and T lymphocytes due to the inability to rearrange immunoglobulin and T cell receptor genes. Gene therapy is an alternative for those RAG1-SCID patients who lack a suitable bone marrow donor. We designed lentiviral vectors with different internal promoters driving codon-optimized RAG1 to ensure optimal expression. We used Rag1−/− mice as a preclinical model for RAG1-SCID to assess the efficacy of the various vectors. We observed that B and T cell reconstitution directly correlated with RAG1 expression. Mice with low RAG1 expression showed poor immune reconstitution; however, higher expression resulted in phenotypic and functional lymphocyte reconstitution comparable to mice receiving wild-type stem cells. No signs of genotoxicity were found. Additionally, RAG1-SCID patient CD34+ cells transduced with our clinical RAG1 vector and transplanted into NSG mice led to improved human B and T cell development. Considering this efficacy outcome, together with favorable safety data, these results substantiate the need for a clinical trial for RAG1-SCID.

Chest Radiographs for Distinguishing ADA-SCID from Other Forms of SCID.

Early differentiation of adenosine deaminase deficient severe combined immunodeficiency (ADA-SCID) from other forms of SCID may initiate appropriate treatment interventions with the aim of metabolic detoxification and improved outcome. Our hypothesis was that previously described radiological features (inferior scapular angle squaring and spurring and costochondral cupping) can differentiate ADA-SCID from other forms of SCID. Chest radiographs at clinical presentation between 2000 and 2017 of children with ADA-SCID were retrospectively included, provided that the radiological features were assessable. Random chest radiographs of children with other forms of SCID were included for comparison. Three paediatric radiologists (2 senior, 1 junior) assessed the radiographs for the specific radiological features and stated their diagnosis (ADA-SCID or non-ADA-SCID). An optimal threshold for test performance was defined using a ROC curve. Thirty-six patients with ADA-SCID and twenty-five patients with non-ADA-SCID were included (median age 3.8 months). The optimal threshold for test performance was at approximately < 7 months old: sensitivity 91.7%, specificity 80.7%, interreader agreement was k = 0.709, AUC 0.862. The positive likelihood ratio for scapular squaring, scapular spur, and costochondral cupping was 4.0, 54.6 and 7.8, respectively. The test was valid when performed by both senior and junior paediatric radiologists. Radiological features such as scapular spurring, scapular squaring and costochondral cupping can reliably differentiate between ADA-SCID and other forms of SCID. This is true for children aged approximately < 7 months, and this is reliable when assessed by both senior and junior paediatric radiologists.

Umbilical Cord Blood Mononuclear Cells for Ex-Vivo Gene Therapy

Cell-mediated (ex-vivo) gene therapy for the treatment of adenosine deaminase (ADA)-deficient severe combined immunodeficiency (SCID) had started in 1990 and nowadays it is the first marketing approval of an ex vivo gene therapy in Europe. The method based on ex-vivo transduction of peripheral blood lymphocytes with retroviral vector carrying the functional ADA gene in 2002 have been improved to use hematopoietic stem cell (HSC) for ex-vivo transduction with 100% survival and the evidence of safety and efficacy. Remarkably, umbilical cord blood mononuclear cells (UCB-MC) were successfully used for treatment of ADA deficiency in neonates as well. Meanwhile SCID is a very rare congenital disorder of the immune system although the option to use peripheral blood lymphocytes as cell carriers of the therapeutic genes for regenerative medicine is highly attractive. In our studies to overcome the neural cells death and stimulate neuroregeneration at neurodegenerative diseases (ALS), spinal cord injury (SCI), and stroke in animal models we employed ex-vivo triple gene therapy based on human UCB-MC transduced with adenoviral vectors carrying vascular endothelial growth factor (VEGF), glial cell-derived neurotrophic factor (GDNF) and neural cell adhesion molecule (NCAM). The reason for clinical application of UCB-MC is based on their availability, ease of preparation and potential for long term storage, as well as legislative, ethical and religious benefits for the transplantation. In our gene-cell construct NCAM was used for homing and survival of UCB-MC at the site of neurodegeneration. VEGF and GDNF are the molecules with well-known neuroprotective function. Moreover VEGF is useful in restoring of the microcirculation as well.The positive results in treatment of ALS mice (Islamov et al, 2016), SCI (Izmailov et al, 2017) and stroke in rats (Sokolov et al, 2018) let us to propose the rationality to use of UCB-MC as cell carriers for the therapeutic genes based on:(1) suitability for both auto- and allotransplantation; (2) low immunogenicity; (3) high level of transduction; (4) high capability of synthetic and secretory activity for production of recombinant therapeutic molecules as well as endogenous growth and neurotrophic factors, cytokines and chemokines; (5) the action of therapeutic molecules on target cells via the paracrine or endocrine mechanism; (6) duration of recombinant molecule production limited by adenoviral vector half-life; (7) elimination of UCB-MC in 1-2 month after administration and possible multiple transplantation. Important, cell-mediated gene delivery makes the viral antigens inside the ex-vivo transduced UCB-MC invisible to the recipient immune system and it is easy to control production of recombinant molecules via the level of cell transduction or the number of transplanted cells. Thus, the cord blood mononuclear cells can serve as powerful tools for address delivery of recombinant genes encoding therapeutic molecules for regenerative medicine. This study was supported by the grant of Russian Science Foundation No 16-15-00010. Kazan Federal University was supported by the Russian Government Program of Competitive Growth. DisclosuresNo relevant conflicts of interest to declare.

First Year of Israeli Newborn Screening for Severe Combined Immunodeficiency-Clinical Achievements and Insights.

Severe combined immunodeficiency (SCID), the most severe form of T cell immunodeficiency, is detectable through quantification of T cell receptor excision circles (TRECs) in dried blood spots obtained at birth. Herein, we describe the results of the first year of the Israeli SCID newborn screening (NBS) program. This important, life-saving screening test is available at no cost for every newborn in Israel. Eight SCID patients were diagnosed through the NBS program in its first year, revealing an incidence of 1:22,500 births in the Israeli population. Consanguine marriages and Muslim ethnic origin were found to be a risk factor in affected newborns, and a founder effect was detected for both IL7Rα and DCLRE1C deficiency SCID. Lymphocyte subset analysis and TREC quantification in the peripheral blood appear to be sufficient for confirmation of typical and leaky SCID and ruling out false positive (FP) results. Detection of secondary targets (infants with non-SCID lymphopenia) did not significantly affect the management or outcomes of these infants in our cohort. In the general, non-immunodeficient population, TREC rises along with gestational age and birth weight, and is significantly higher in females and the firstborn of twin pairs. Low TREC correlates with both gestational age and birth weight in extremely premature newborns. Additionally, the rate of TREC increase per week consistently accelerates with gestational age. Together, these findings mandate a lower cutoff or a more lenient screening algorithm for extremely premature infants, in order to reduce the high rate of FPs within this group. A significant surge in TREC values was observed between 28 and 30 weeks of gestation, where median TREC copy numbers rise by 50% over 2 weeks. These findings suggest a maturational step in T cell development around week 29 gestation, and imply moderate to late preterms should be screened with the same cutoff as term infants. The SCID NBS program is still in its infancy, but is already bearing fruit in the early detection and improved outcomes of children with SCID in Israel and other countries.

The Cost-Effectiveness Of Screening For Severe Combined Immunodeficiency (SCID) In The UK NHS Newborn Bloodspot Screening Programme

To assess the cost-effectiveness of including screening for severe combined immunodeficiency (SCID) in the NHS newborn bloodspot screening programme. A decision tree model with life-table estimates of outcomes was built. Model structure and parameterisation were informed by systematic review and expert clinical judgment. A public service perspective was used and lifetime costs and quality adjusted life years (QALYs) were discounted at 3.5%. Standard treatment following screening was hematopoietic stem cell transplantation with additional treatment options for adenosine deaminase deficiency SCID. The model estimated the number of non-SCID cases identified incidentally. Probabilistic sensitivity analyses was undertaken. An exploratory disbenefit analysis was conducted for false positives and those diagnosed with non-SCID T-cell lymphopenia (TCL) who would have presented as healthy at birth. Screening for SCID was estimated to result in 310 (72-811) presumptive positive cases per year including 260 (25-760) false positives cases, 7 (1-21) preterm cases, 26 (9-50) non-SCID TCL cases and 17 (14-22) SCID cases. Screening would increase overall QALYs and costs and result in an incremental cost-effectiveness ratio (ICER) of £17,642. The increase in QALYs was driven by improved survival in the screened cohort with mortality reducing from 8 (5.3-12) deaths to 1.7 (0.6-4.1). Results were sensitive to a number of parameters including the cost of the screening test, the incidence of SCID and quality of life estimates. The disbenefit analysis estimated that to push the cost-effectiveness over the £20,000 threshold the 6.5 (1.5-16) healthy at birth cases would need to experience a disbenefit of 2 QALYs and the false positive cases a disbenefit of over 12 quality adjusted days. Screening for SCID is potentially cost-effective at £20,000 per QALY, key uncertainties relate to the impact of false positives and the identification of children with non-SCID TCL.

A case of severe combined immunodeficiency caused by adenosine deaminase deficiency with a new mutation

Abstract Adenosine deaminase (ADA) deficiency is a rare autosomal recessive disorder of purine metabolism that leads to severe combined immunodeficiency (SCID) by primarily affecting lymphocyte development and function. ADA deficiency is a medical emergency. Early diagnosis and treatment could provide low morbidity and mortality. Patients present in the first months of life with failure to thrive, diarrhea, oral candidiasis and opportunistic infections. Herein we report a case of a 3 month old patient with ADA deficient SCID having a novel splicing mutation.

Cytoreductive conditioning intensity predicts clonal diversity in ADA-SCID retroviral gene therapy patients

AbstractRetroviral gene therapy has proved efficacious for multiple genetic diseases of the hematopoietic system, but roughly half of clinical gene therapy trial protocols using gammaretroviral vectors have reported leukemias in some of the patients treated. In dramatic contrast, 39 adenosine deaminase–deficient severe combined immunodeficiency (ADA-SCID) patients have been treated with 4 distinct gammaretroviral vectors without oncogenic consequence. We investigated clonal dynamics and diversity in a cohort of 15 ADA-SCID children treated with gammaretroviral vectors and found clear evidence of genotoxicity, indicated by numerous common integration sites near proto-oncogenes and by increased abundance of clones with integrations near MECOM and LMO2. These clones showed stable behavior over multiple years and never expanded to the point of dominance or dysplasia. One patient developed a benign clonal dominance that could not be attributed to insertional mutagenesis and instead likely resulted from expansion of a transduced natural killer clone in response to chronic Epstein-Barr virus viremia. Clonal diversity and T-cell repertoire, measured by vector integration site sequencing and T-cell receptor β-chain rearrangement sequencing, correlated significantly with the amount of busulfan preconditioning delivered to patients and to CD34+ cell dose. These data, in combination with results of other ADA-SCID gene therapy trials, suggest that disease background may be a crucial factor in leukemogenic potential of retroviral gene therapy and underscore the importance of cytoreductive conditioning in this type of gene therapy approach.

Good Laboratory Practice Preclinical Safety Studies for GSK2696273 (MLV Vector-Based Ex Vivo Gene Therapy for Adenosine Deaminase Deficiency Severe Combined Immunodeficiency) in NSG Mice.

GSK2696273 (autologous CD34+ cells transduced with retroviral vector that encodes for the human adenosine deaminase [ADA] enzyme) is a gamma-retroviral ex vivo gene therapy of bone marrow-derived CD34+ cells for the treatment of adenosine deaminase deficiency severe combined immunodeficiency (ADA-SCID). ADA-SCID is a severe monogenic disease characterized by immunologic and nonimmunologic symptoms. Bone-marrow transplant from a matched related donor is the treatment of choice, but it is available for only a small proportion of patients. Ex vivo gene therapy of patient bone-marrow CD34+ cells is an alternative treatment. In order to prepare for a marketing authorization application in the European Union, preclinical safety studies in mice were requested by the European Medicines Agency (EMA). A pilot study and a main biodistribution study were performed according to Good Laboratory Practice (GLP) at the San Raffaele Telethon Institute for Gene Therapy test facility. In the main study, human umbilical cord blood (UCB)-derived CD34+ cells were transduced with gamma-retroviral vector used in the production of GSK2696273. Groups of 10 male and 10 female NOD-SCID gamma (NSG) mice were injected intravenously with a single dose of transduced- or mock-transduced UCB CD34+ cells, and they were observed for 4 months. Engraftment and multilineage differentiation of blood cells was observed in the majority of animals in both groups. There was no significant difference in the level of chimerism between the two groups. In the gene therapy group, vector was detectable in lymphohemopoietic and nonlymphohemopoietic tissues, consistent with the presence of gene-modified human hematopoietic donor cells. Given the absence of relevant safety concerns in the data, the nonclinical studies and the clinical experience with GSK2696273 supported a successful application for market authorization in the European Union for the treatment of ADA-SCID patients, for whom no suitable human leukocyte antigen-matched related donor is available.

A Case of IL-7R Deficiency Caused by a Novel Synonymous Mutation and Implications for Mutation Screening in SCID Diagnosis.

Reported synonymous substitutions are generally non-pathogenic, and rare pathogenic synonymous variants may be disregarded unless there is a high index of suspicion. In a case of IL7 receptor deficiency severe combined immunodeficiency (SCID), the relevance of a non-reported synonymous variant was only suspected through the use of additional in silico computational tools, which focused on the impact of mutations on gene splicing. The pathogenic nature of the variant was confirmed using experimental validation of the effect on mRNA splicing and IL7 pathway function. This case reinforces the need to use additional experimental methods to establish the functional impact of specific mutations, in particular for cases such as SCID where prompt diagnosis can greatly impact on diagnosis, treatment, and survival.