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autoimmune dysregulation and purine metabolism in Adenosine Deaminase Deficiency

Genetic defects in the Adenosine Deaminase (ADA) gene are among the most common causes for severe combined immunoDeficiency (SCID). ADA-SCID patients suffer from lymphopenia, severely impaired cellular and humoral immunity, failure to thrive and recurrent infections. Currently available therapeutic options for this otherwise fatal disorder include bone marrow transplantation (BMT), enzyme replacement therapy with bovine ADA (PEG-ADA) or hematopoietic stem cell gene therapy (HSC-GT). Although varying degrees of immune reconstitution can be achieved by these treatments, breakdown of tolerance is a major concern in ADA-SCID. Immune dysregulation such as autoimmune hypothyroidism, diabetes mellitus, hemolytic anemia, and immune thrombocytopenia are frequently observed in milder forms of the disease. However, several reports document similar complications also in patients on long-term PEG-ADA and after BMT or GT treatment. A skewed repertoire and decreased immune functions have been implicated in autoimmunity observed in certain B-cell and/or T-cell immunodeficiencies, but it remains unclear to what extent specific mechanisms of tolerance are affected in ADA Deficiency. Herein we provide an overview about ADA-SCID and the autoimmune manifestations reported in these patients before and after treatment. We also assess the value of the ADA-deficient mouse model as a useful tool to study both immune and metabolic disease mechanisms. With focus on regulatory T and B cells we discuss the lymphocyte subpopulations particularly prone to contribute to the loss of self-tolerance and onset of autoimmunity in ADA Deficiency. Moreover we address which aspects of immune dysregulation are specifically related to alterations in purine metabolism caused by the lack of ADA and the subsequent accumulation of metabolites with immunomodulatory properties.

Gene Therapy for Adenosine Deaminase Deficiency

In the last decade, gene therapy for Adenosine Deaminase Deficiency has been developed as a successful alternative strategy to allogeneic bone marrow transplant and enzyme replacement therapy. Infusion of autologous hematopoietic stem cells, corrected ex vivo by retroviral vectors and combined to low-intensity conditioning regimen, has resulted in immunologic improvement, metabolic correction, and long-term clinical benefits. These findings have opened the way to applications of gene therapy in other primary immune deficiencies using novel vector technology.

gene therapy for immunoDeficiency due to Adenosine Deaminase Deficiency

Background We investigated the long-term outcome of gene therapy for severe combined immunoDeficiency (SCID) due to the lack of Adenosine Deaminase (ADA), a fatal disorder of purine metabolism and immunoDeficiency. Methods We infused autologous CD34+ bone marrow cells transduced with a retroviral vector containing the ADA gene into 10 children with SCID due to ADA Deficiency who lacked an HLA-identical sibling donor, after nonmyeloablative conditioning with busulfan. Enzyme-replacement therapy was not given after infusion of the cells. Results All patients are alive after a median follow-up of 4.0 years (range, 1.8 to 8.0). Transduced hematopoietic stem cells have stably engrafted and differentiated into myeloid cells containing ADA (mean range at 1 year in bone marrow lineages, 3.5 to 8.9%) and lymphoid cells (mean range in peripheral blood, 52.4 to 88.0%). Eight patients do not require enzyme-replacement therapy, their blood cells continue to express ADA, and they have no signs of defective detoxificati…

Adenosine Deaminase Deficiency

Clinical characteristics Adenosine Deaminase (ADA) Deficiency is a systemic purine metabolic disorder that primarily affects lymphocyte development, viability, and function. The clinical phenotypic spectrum includes: Infants with typical early-onset ADA-deficient SCID have failure to thrive and opportunistic infections associated with marked depletion of T, B, and NK lymphocytes, and an absence of both humoral and cellular immune function. If immune function is not restored, children with ADA-deficient SCID rarely survive beyond age one to two years. Infections in delayed- and late-onset types (commonly, recurrent otitis, sinusitis, and upper respiratory) may initially be less severe than those in individuals with ADA-deficient SCID; however, by the time of diagnosis these individuals often have chronic pulmonary insufficiency and may have autoimmune phenomena (cytopenias, anti-thyroid antibodies), allergies, and elevated serum concentration of IgE. The longer the disorder goes unrecognized, the more immune function deteriorates and the more likely are chronic sequelae of recurrent infection. Diagnosis/testing The diagnosis of ADA Deficiency is established in a proband: Management Treatment of manifestations: Infections are treated with specific antibiotic, antifungal, and antiviral agents and administration of intravenous immunoglobulin (IVIg); prophylaxis is provided for Pneumocystis jiroveci infection. Prevention of primary manifestations: Restoration of a functional immune system is essential. The preferred treatment is bone marrow/stem cell transplantation (BMT/SCT) from an HLA-identical healthy sib or close relative. However, most individuals with ADA-deficient SCID lack an HLA-identical related donor. For these individuals, alternative therapies can be considered: Surveillance: Annual or more frequent evaluation of lymphocyte counts, serum immunoglobulin levels, and various in vitro tests of cellular and humoral immune function following BMT/SCT and during ERT (more frequent monitoring and other specialized testing would be required for participants in gene therapy trials). Individuals on ERT also require periodic monitoring of PEG-ADA levels in plasma and metabolite levels in erythrocytes, and under some circumstances testing for anti-ADA antibodies. Agents/circumstances to avoid: The use of adenine arabinoside (a substrate for ADA) as an antiviral agent or for chemotherapy of malignancies should be avoided; pentostatin, a potent ADA inhibitor used to treat some lymphoid malignancies, would be ineffective in persons who lack ADA, and would interfere with PEG-ADA. Evaluation of relatives at risk: In the newborn sibs of a proband, it is appropriate to either assay ADA catalytic activity or perform molecular genetic testing (if the family-specific pathogenic variants are known), so that morbidity and mortality can be reduced by early diagnosis and treatment. Genetic counseling ADA Deficiency is inherited in an autosomal recessive manner. At conception, each sib of an affected individual has a 25% chance of being affected, a 50% chance of being an asymptomatic carrier, and a 25% chance of being unaffected and not a carrier. Carrier testing for at-risk family members and prenatal testing for pregnancies at increased risk are possible once the pathogenic variants have been identified in the family.

successful bone marrow transplantation with reduced intensity conditioning in a patient with delayed onset Adenosine Deaminase Deficiency

Kanegane H, Taneichi H, Nomura K, Wada T, Yachie A, Imai K, Ariga T, Santisteban I, Hershfield MS, Miyawaki T. Successful bone marrow transplantation with reduced intensity conditioning in a patient with delayed-onset Adenosine Deaminase Deficiency.

Abstract:  In this case report, we describe successful BMT with RIC in a patient with delayed-onset ADA Deficiency. A three-yr-old Japanese boy was diagnosed with delayed-onset ADA Deficiency because of recurrent bronchitis, bronchiectasia, and lymphopenia. In addition, autoimmune thyroiditis and neutropenia were present. At four yr of age, he underwent BMT with a RIC regimen, including busulfan and fludarabine, from an HLA-identical healthy sister. Engraftment after BMT was uneventful without GVHD. Decreased ADA levels in blood immediately increased following BMT, and the patient was disease-free 13 months after BMT. These results suggest that BMT with RIC may sufficiently restore immune regulation in delayed-onset ADA Deficiency. A longer follow-up period is needed to confirm these observations.

Successful bone marrow transplantation with reduced intensity conditioning in a patient with delayed‐onset Adenosine Deaminase Deficiency

Kanegane H, Taneichi H, Nomura K, Wada T, Yachie A, Imai K, Ariga T, Santisteban I, Hershfield MS, Miyawaki T. Successful bone marrow transplantation with reduced intensity conditioning in a patient with delayed-onset Adenosine Deaminase Deficiency.

Abstract:  In this case report, we describe successful BMT with RIC in a patient with delayed-onset ADA Deficiency. A three-yr-old Japanese boy was diagnosed with delayed-onset ADA Deficiency because of recurrent bronchitis, bronchiectasia, and lymphopenia. In addition, autoimmune thyroiditis and neutropenia were present. At four yr of age, he underwent BMT with a RIC regimen, including busulfan and fludarabine, from an HLA-identical healthy sister. Engraftment after BMT was uneventful without GVHD. Decreased ADA levels in blood immediately increased following BMT, and the patient was disease-free 13 months after BMT. These results suggest that BMT with RIC may sufficiently restore immune regulation in delayed-onset ADA Deficiency. A longer follow-up period is needed to confirm these observations.

autoimmune dysregulation and purine metabolism in Adenosine Deaminase Deficiency

Genetic defects in the Adenosine Deaminase (ADA) gene are among the most common causes for severe combined immunoDeficiency (SCID). ADA-SCID patients suffer from lymphopenia, severely impaired cellular and humoral immunity, failure to thrive and recurrent infections. Currently available therapeutic options for this otherwise fatal disorder include bone marrow transplantation (BMT), enzyme replacement therapy with bovine ADA (PEG-ADA) or hematopoietic stem cell gene therapy (HSC-GT). Although varying degrees of immune reconstitution can be achieved by these treatments, breakdown of tolerance is a major concern in ADA-SCID. Immune dysregulation such as autoimmune hypothyroidism, diabetes mellitus, hemolytic anemia, and immune thrombocytopenia are frequently observed in milder forms of the disease. However, several reports document similar complications also in patients on long-term PEG-ADA and after BMT or GT treatment. A skewed repertoire and decreased immune functions have been implicated in autoimmunity observed in certain B-cell and/or T-cell immunodeficiencies, but it remains unclear to what extent specific mechanisms of tolerance are affected in ADA Deficiency. Herein we provide an overview about ADA-SCID and the autoimmune manifestations reported in these patients before and after treatment. We also assess the value of the ADA-deficient mouse model as a useful tool to study both immune and metabolic disease mechanisms. With focus on regulatory T and B cells we discuss the lymphocyte subpopulations particularly prone to contribute to the loss of self-tolerance and onset of autoimmunity in ADA Deficiency. Moreover we address which aspects of immune dysregulation are specifically related to alterations in purine metabolism caused by the lack of ADA and the subsequent accumulation of metabolites with immunomodulatory properties.

gene therapy for immunoDeficiency due to Adenosine Deaminase Deficiency

Background We investigated the long-term outcome of gene therapy for severe combined immunoDeficiency (SCID) due to the lack of Adenosine Deaminase (ADA), a fatal disorder of purine metabolism and immunoDeficiency. Methods We infused autologous CD34+ bone marrow cells transduced with a retroviral vector containing the ADA gene into 10 children with SCID due to ADA Deficiency who lacked an HLA-identical sibling donor, after nonmyeloablative conditioning with busulfan. Enzyme-replacement therapy was not given after infusion of the cells. Results All patients are alive after a median follow-up of 4.0 years (range, 1.8 to 8.0). Transduced hematopoietic stem cells have stably engrafted and differentiated into myeloid cells containing ADA (mean range at 1 year in bone marrow lineages, 3.5 to 8.9%) and lymphoid cells (mean range in peripheral blood, 52.4 to 88.0%). Eight patients do not require enzyme-replacement therapy, their blood cells continue to express ADA, and they have no signs of defective detoxificati…