Welcome to the ESID 2022 Meeting Interactive Programme
The meeting will officially run on Central European Summer Time (CEST)
Introduction
Severe Congenital Neutropenia and the Risk of MDS/AML
Dyskeratosis Congenita
Immune Dysfunction in WASp GOF Variants
CHARACTERIZATION OF HEMATOPOIETIC STEM CELL FUNCTIONS IN PATIENTS WITH ADENOSINE DEAMINASE 2 DEFICIENCY
Abstract
Background and Aims
The deficiency of adenosine deaminase 2 (DADA2) is an inborn error of immunity caused by loss-of-function mutations in the ADA2 gene. Manifestations include vasculopathy and immunological and hematological abnormalities. It is unknown how ADA2 loss causes bone marrow (BM) failure, and understanding these mechanisms is essential for developing new targeted therapies.
Methods
We analyzed the BM composition in patients and evaluated the toxicity and efficacy of ADA2 gene transfer in patients’ hematopoietic stem-progenitor cells (HSPCs).
Results
HSPCs and the primitive compartment were significantly reduced in patients’ BM compared with healthy donors (HDs). Although reduced in number, patients’ HSPCs showed normal clonogenic and differentiation potential. We also characterized patients’ mesenchymal stromal cells (MSCs), critical elements interacting with HSPCs in the BM. They exhibited a reduced clonogenic capacity and low levels of primitive marker expression, while senescence markers increased compared with HDs. To assess whether gene therapy could represent a potent treatment for DADA2, we developed a lentiviral vector (LV) to restore constitutively ADA2 expression in patients’ HSPCs. HSPCs transduction allowed efficient delivery of the functional ADA2 enzyme in patients’ CD34-derived cells without signs of toxicity. Transduced HSPCs infused into immunocompromised mice demonstrated that ADA2-modified cells supported a multilineage reconstitution with a polyclonal integration pattern.
Conclusions
Our results indicate that the loss of ADA2 leads to a reduced number of primitive progenitors in the HSPC pool and an exhausted MSC phenotype. LV-mediated ADA2 reconstitution seems a promising approach to re-establish stable ADA2 activity and correct the hematological manifestations in patients with DADA2.
LOW CTLA-4 EXPRESSION BY NBEAL2 DEFICIENT CONVENTIONAL T CELLS AND IMMUNE DYSREGULATION IN GRAY PLATELET SYNDROME.
Abstract
Background and Aims
Recessive mutations in the NBEAL2 gene lead to gray platelet syndrome (GPS), a bleeding disorder characterized by macrothrombocytopenia and α-granule-deficient platelets. A proportion of NBEAL2-deficient patients present immune system abnormalities (autoimmune disease, autoantibodies, leukopenia, etc) – suggesting a role for NBEAL2 in immune homeostasis and tolerance. And the mechanism behind the development of autoimmunity remains unclear.
Methods
NBEAL2 role in primary human T cells was investigated by mass spectrometry interactome study, CRISPR-Cas-9 knock-down and single-cell RNA sequencing.
Results
In a mass spectrometry interactome study, 76 NBEAL2 partners were found in primary T cells, including LRBA (a member of the BEACH family, like NBEAL2). Recessive LRBA mutations cause autoimmunity and lymphocytic infiltration through defective CTLA-4 trafficking. We found that NBEAL2 deficiency leads to low CTLA-4 expression in patients’ effector T cells but not in their regulatory T cells. The NBEAL2-LRBA-CTLA-4 interaction was confirmed by immunoprecipitation. NBEAL2 knock-down in primary T cells also led to low CTLA-4 expression. Lastly, single cell RNAseq analyses of NBEAL2 and LRBA deficient lymphocytes uncovered an elevated IL6-STAT3 signature in LRBA patients, possibly reflecting their low CTLA-4 expression in regulatory T cells.
Conclusions
Our results show that NBEAL2 is involved in the regulation of CTLA-4 expression in conventional T cells and provide a molecular rationale for considering CTLA-4-immunoglobulin therapy in patients with GPS and autoimmune disease.