title: B-cell development and functions and therapeutic options in adenosine deaminase-deficient patients.
abstract: BACKGROUND
  Adenosine deaminase (ADA) deficiency causes severe cellular and humoral immune defects and dysregulation because of metabolic toxicity. Alterations in B-cell development and function have been poorly studied. Enzyme replacement therapy (ERT) and hematopoietic stem cell (HSC) gene therapy (GT) are therapeutic options for patients lacking a suitable bone marrow (BM) transplant donor.
  
  
  OBJECTIVE
  We sought to study alterations in B-cell development in ADA-deficient patients and investigate the ability of ERT and HSC-GT to restore normal B-cell differentiation and function.
  
  
  METHODS
  Flow cytometry was used to characterize B-cell development in BM and the periphery. The percentage of gene-corrected B cells was measured by using quantitative PCR. B cells were assessed for their capacity to proliferate and release IgM after stimulation.
  
  
  RESULTS
  Despite the severe peripheral B-cell lymphopenia, patients with ADA-deficient severe combined immunodeficiency showed a partial block in central BM development. Treatment with ERT or HSC-GT reverted most BM alterations, but ERT led to immature B-cell expansion. In the periphery transitional B cells accumulated under ERT, and the defect in maturation persisted long-term. HSC-GT led to a progressive improvement in B-cell numbers and development, along with increased levels of gene correction. The strongest selective advantage for ADA-transduced cells occurred at the transition from immature to naive cells. B-cell proliferative responses and differentiation to immunoglobulin secreting IgM after B-cell receptor and Toll-like receptor triggering were severely impaired after ERT and improved significantly after HSC-GT.
  
  
  CONCLUSIONS
  ADA-deficient patients show specific defects in B-cell development and functions that are differently corrected after ERT and HSC-GT.
authors: San Raffaele Telethon Institute for Gene Therapy (TIGET), San Raffaele Scientific Institute, Milan, Italy.
authors: Immacolata
authors: I
authors: Brigida
authors: San Raffaele Telethon Institute for Gene Therapy (TIGET), San Raffaele Scientific Institute, Milan, Italy.
authors: Aisha V
authors: AV
authors: Sauer
authors: Pediatric Immunohematology and Bone Marrow Transplantation Unit, San Raffaele Scientific Institute, Milan, Italy.
authors: Francesca
authors: F
authors: Ferrua
authors: San Raffaele Telethon Institute for Gene Therapy (TIGET), San Raffaele Scientific Institute, Milan, Italy.
authors: Stefania
authors: S
authors: Giannelli
authors: San Raffaele Telethon Institute for Gene Therapy (TIGET), San Raffaele Scientific Institute, Milan, Italy.
authors: Samantha
authors: S
authors: Scaramuzza
authors: San Raffaele Telethon Institute for Gene Therapy (TIGET), San Raffaele Scientific Institute, Milan, Italy.
authors: Valentina
authors: V
authors: Pistoia
authors: San Raffaele Telethon Institute for Gene Therapy (TIGET), San Raffaele Scientific Institute, Milan, Italy; Vita-Salute San Raffaele University, Milan, Italy.
authors: Maria Carmina
authors: MC
authors: Castiello
authors: Department of Immunology, Erasmus MC, University Medical Center, Rotterdam, The Netherlands.
authors: Barbara H
authors: BH
authors: Barendregt
authors: Pediatric Immunohematology and Bone Marrow Transplantation Unit, San Raffaele Scientific Institute, Milan, Italy.
authors: Maria Pia
authors: MP
authors: Cicalese
authors: Pediatric Immunohematology and Bone Marrow Transplantation Unit, San Raffaele Scientific Institute, Milan, Italy.
authors: Miriam
authors: M
authors: Casiraghi
authors: CUSSB, Vita-Salute San Raffaele University, Milan, Italy.
authors: Chiara
authors: C
authors: Brombin
authors: Division of Allergy, Immunology and Bone Marrow Transplantation, Department of Pediatrics, University of California San Francisco, San Francisco, Calif.
authors: Jennifer
authors: J
authors: Puck
authors: Pediatric Clinic, Juliane Marie Center, Copenhagen, Denmark.
authors: Klaus
authors: K
authors: Müller
authors: Pediatric Onco-Hematology and BMT Unit, Children's Hospital, Spedali Civili, Brescia, Italy.
authors: Lucia Dora
authors: LD
authors: Notarangelo
authors: Department of Pediatrics, University of Turin, Turin, Italy.
authors: Davide
authors: D
authors: Montin
authors: Department of Pediatric Immunology and Infectious Diseases, University Medical Center Utrecht, Utrecht, The Netherlands.
authors: Joris M
authors: JM
authors: van Montfrans
authors: San Raffaele Telethon Institute for Gene Therapy (TIGET), San Raffaele Scientific Institute, Milan, Italy; Vita-Salute San Raffaele University, Milan, Italy.
authors: Maria Grazia
authors: MG
authors: Roncarolo
authors: Novartis Institute for Research in Biomedicine, Basel, Switzerland.
authors: Elisabetta
authors: E
authors: Traggiai
authors: Department of Immunology, Erasmus MC, University Medical Center, Rotterdam, The Netherlands.
authors: Jacques J M
authors: JJ
authors: van Dongen
authors: Department of Immunology, Erasmus MC, University Medical Center, Rotterdam, The Netherlands.
authors: Mirjam
authors: M
authors: van der Burg
authors: San Raffaele Telethon Institute for Gene Therapy (TIGET), San Raffaele Scientific Institute, Milan, Italy; Department of Systems Medicine, Tor Vergata University, Rome, Italy. Electronic address: aiuti.alessandro@hsr.it.
authors: Alessandro
authors: A
authors: Aiuti
mesh_terms: D000243:Adenosine Deaminase / Q000172:deficiency* / Q000235:genetics / Q000627:therapeutic use; D000293:Adolescent; D053264:B-Cell Activating Factor / Q000502:physiology; D001402:B-Lymphocytes / Q000276:immunology / Q000502:physiology*; D002648:Child; D002675:Child, Preschool; D056947:Enzyme Replacement Therapy; D015316:Genetic Therapy; D018380:Hematopoietic Stem Cell Transplantation; D006801:Humans; D007223:Infant
chemical_list: D053264:B-Cell Activating Factor; D000243:Adenosine Deaminase
keywords: B-cell development; Gene therapy; adenosine deaminase–deficient severe combined immunodeficiency; antibodies