The Spectrum of the Deficiency of Adenosine Deaminase 2: An Observational Analysis of a 60 Patient Cohort

The deficiency of adenosine deaminase 2 (DADA2) is an autosomal recessively inherited disease that has undergone extensive phenotypic expansion since being first described in patients with fevers, recurrent strokes, livedo racemosa, and polyarteritis nodosa in 2014. It is now recognized that patients may develop multisystem disease that spans multiple medical subspecialties. Here, we describe the findings from a large single center longitudinal cohort of 60 patients, the broad phenotypic presentation, as well as highlight the cohort’s experience with hematopoietic cell transplantation and COVID-19. Disease manifestations could be separated into three major phenotypes: inflammatory/vascular, immune dysregulatory, and hematologic, however, most patients presented with significant overlap between these three phenotype groups. The cardinal features of the inflammatory/vascular group included cutaneous manifestations and stroke. Evidence of immune dysregulation was commonly observed, including hypogammaglobulinemia, absent to low class-switched memory B cells, and inadequate response to vaccination. Despite these findings, infectious complications were exceedingly rare in this cohort. Hematologic findings including pure red cell aplasia (PRCA), immune-mediated neutropenia, and pancytopenia were observed in half of patients. We significantly extended our experience using anti-TNF agents, with no strokes observed in 2026 patient months on TNF inhibitors. Meanwhile, hematologic and immune features had a more varied response to anti-TNF therapy. Six patients received a total of 10 allogeneic hematopoietic cell transplant (HCT) procedures, with secondary graft failure necessitating repeat HCTs in three patients, as well as unplanned donor cell infusions to avoid graft rejection. All transplanted patients had been on anti-TNF agents prior to HCT and received varying degrees of reduced-intensity or non-myeloablative conditioning. All transplanted patients are still alive and have discontinued anti-TNF therapy. The long-term follow up afforded by this large single-center study underscores the clinical heterogeneity of DADA2 and the potential for phenotypes to evolve in any individual patient.

A Case of Deficiency of Adenosine Deaminase 2: 28 years of Diagnostic Challenges

Deficiency of adenosine deaminase 2 (DADA2) is a unique monogenic autoinflammatory disease caused by autosomal recessive loss-of-function mutations in the CECR1 gene which presents as childhood-onset small- and medium-vessel vasculitis. Previously, many of these patients were misdiagnosed and thought to have clinical features of systemic polyarteritis nodosum, which negatively influenced its outcome, since TNF inhibitors seem to have efficacy on the vasculitic phenotype of DADA2. We present a case of a 28-year-old woman with a lifelong unknown syndrome and unique clinical manifestations recently recognized as DADA2. The first manifestation, at 3 months of age, was an episode of facial paralysis during which renovascular hypertension was diagnosed. Later, she developed episodes of prolonged fever, polyarthritis, Raynaud’s phenomenon, gastrointestinal bleeding, and intracerebral hemorrhage. This inflammatory state ultimately led to the development of amyloid A amyloidosis and renal insufficiency.

Lentiviral-Mediated Gene Therapy for the Treatment of Adenosine Deaminase 2 Deficiency

Adenosine deaminase 2 deficiency (DADA2) is a recently defined inborn error of immunity caused by loss-of-function mutations in the ADA2 gene. Patients suffer from severe manifestations, including early-onset lacunar strokes, intracranial hemorrhages, vasculitis/vasculopathy, systemic inflammation, immunodeficiency, and hematologic abnormalities. The therapeutic benefit of the current treatments is unsatisfactory. Anti-tumor necrosis factor therapy reduces strokes and systemic inflammation but does not correct cytopenia and bone marrow failure. Allogeneic hematopoietic stem/progenitor cell (HSPC) transplantation can ameliorate most disease manifestations, but patients are at risk for complications. Therefore, we proposed that autologous HSPC gene therapy may be an alternative curative option for patients who has no compatible donor or cannot receive intense chemotherapy. We performed an in-depth study, using multiparametric flow cytometry, of the bone marrow (BM) cell composition of three adult patients with the hematological phenotype of DADA2. Compared with healthy donors (HDs), patients' BM exhibited a reduced number of mature and immature populations belonging to different hematopoietic lineages. Patients exhibited a substantial reduction in circulating neutrophils and hematopoietic stem cells and progenitor pools in the BM. Severe neutropenia and HSPC defects are direct causes of DADA2. Indeed, ADA2 knock-down in zebrafish - as rodents do not harbor an ADA2 orthologue gene - caused a significant decrease in neutrophil and HSPC numbers, reminiscent of patients' phenotype. Administration of human recombinant ADA2 effectively corrected both neutropenia and defective hematopoiesis in the zebrafish embryo. We used a third-generation LV to restore constitutive ADA2 expression in HSPCs. Transduction of healthy donors' HSPCs allowed efficient delivery of the functional ADA2 enzyme with no toxicity. Supranormal ADA2 expression in healthy donors' and patients' HSPCs was well-tolerated and did not impact HSPC multilineage differentiation potential in vitro and in vivo. We also assessed whether LV-derived ADA2 could correct the hyperinflammatory M1 macrophage phenotype characteristic of DADA2. ADA2 reconstitution in patients' macrophages led to the normalization of IL-6 and TNF release. Similar results were obtained using M1 macrophages differentiated from ADA2-transduced HSPCs. Altogether, our findings indicate that HSPC gene therapy is a promising approach to re-establish stable ADA2 activity and correct the hematological and inflammatory manifestations in patients with DADA2. Disclosures Aiuti: Orchard Therapeutics: Other: PI of clinical trials sponsored by company.

Case Report: Deficiency of Adenosine Deaminase 2 Presenting With Overlapping Features of Autoimmune Lymphoproliferative Syndrome and Bone Marrow Failure

Deficiency of adenosine deaminase 2 (DADA2) is an autosomal recessive disease associated with a highly variable clinical presentation, such as vasculitis, inflammation, and hematologic manifestations. Some associations of clinical features can mimic autoimmune lymphoproliferative syndrome (ALPS). We report a case of a female patient who fulfilled the 2009 National Institute of Health revised criteria for ALPS and received a delayed diagnosis of DADA2. During her childhood, she suffered from autoimmune hemolytic anemia, immune thrombocytopenia, and chronic lymphoproliferation, which partially responded to multiple lines of treatments and were followed, at 25 years of age, by pulmonary embolism, septic shock, and bone marrow failure with myelodysplastic evolution. The patient died from the progression of pulmonary disease and multiorgan failure. Two previously unreported variants of gene ADA2/CECR1 were found through next-generation sequencing analysis, and a pathogenic role was demonstrated through a functional study. A single somatic STAT3 mutation was also found. Clinical phenotypes encompassing immune dysregulation and marrow failure should be evaluated at the early stage of diagnostic work-up with an extended molecular evaluation. A correct genetic diagnosis may lead to a precision medicine approach consisting of the use of targeted treatments or early hematopoietic stem cell transplantation.

A Novel LC–MS/MS-Based Method for the Diagnosis of ADA2 Deficiency from Dried Plasma Spot

Adenosine Deaminase 2 Deficiency (DADA2) (OMIM: 607575) is a monogenic, autoinflammatory disease caused by the loss of functional homozygous or heterozygous mutations in the ADA 2 gene (previously CECR1, Cat Eye Syndrome Chromosome Region 1). A timely diagnosis is crucial to start Anti-TNF therapies that are efficacious in controlling the disease. The confirmation of DADA2 is based on DNA sequencing and enzymatic assay. It is, thus, very important to have robust and reliable assays that can be rapidly utilized in specialized laboratories that can centralize samples from other centers. In this paper, we show a novel enzymatic assay based on liquid chromatography-tandem mass spectrometry that allows the accurate determination of the ADA2 enzyme activity starting from very small amounts of plasma spotted on filter paper (dried plasma spot). The method allows significantly distinguishing healthy controls from affected patients and carriers and could be of help in implementing the diagnostic workflow of DADA2.

Lentiviral correction of enzymatic activity restrains macrophage inflammation in adenosine deaminase 2 deficiency

Adenosine deaminase 2 deficiency (DADA2) is a rare inherited disorder that is caused by autosomal recessive mutations in the ADA2 gene. Clinical manifestations include early-onset lacunar strokes, vasculitis/vasculopathy, systemic inflammation, immunodeficiency, and hematologic defects. Anti–tumor necrosis factor therapy reduces strokes and systemic inflammation. Allogeneic hematopoietic stem/progenitor cell (HSPC) transplantation can ameliorate most disease manifestations, but patients are at risk for complications. Autologous HSPC gene therapy may be an alternative curative option for patients with DADA2. We designed a lentiviral vector encoding ADA2 (LV-ADA2) to genetically correct HSPCs. Lentiviral transduction allowed efficient delivery of the functional ADA2 enzyme into HSPCs from healthy donors. Supranormal ADA2 expression in human and mouse HSPCs did not affect their multipotency and engraftment potential in vivo. The LV-ADA2 induced stable ADA2 expression and corrected the enzymatic defect in HSPCs derived from DADA2 patients. Patients’ HSPCs re-expressing ADA2 retained their potential to differentiate into erythroid and myeloid cells. Delivery of ADA2 enzymatic activity in patients’ macrophages led to a complete rescue of the exaggerated inflammatory cytokine production. Our data indicate that HSPCs ectopically expressing ADA2 retain their multipotent differentiation ability, leading to functional correction of macrophage defects. Altogether, these findings support the implementation of HSPC gene therapy for DADA2.