title: Defective B cell tolerance in adenosine deaminase deficiency is corrected by gene therapy.
abstract: Adenosine deaminase (ADA) gene defects are among the most common causes of SCID. Restoration of purine metabolism and immune functions can be achieved by enzyme replacement therapy, or more effectively by bone marrow transplant or HSC gene therapy (HSC-GT). However, autoimmune complications and autoantibody production, including anti-nuclear antibodies (ANAs), frequently occur in ADA-SCID patients after treatment. To assess whether ADA deficiency affects the establishment of B cell tolerance, we tested the reactivity of recombinant antibodies isolated from single B cells of ADA-SCID patients before and after HSC-GT. We found that before HSC-GT, new emigrant/transitional and mature naive B cells from ADA-SCID patients contained more autoreactive and ANA-expressing clones, indicative of defective central and peripheral B cell tolerance checkpoints. We further observed impaired B cell receptor (BCR) and TLR functions in B cells after ADA inhibition, which may underlie the defects in B cell tolerance. Strikingly, after HSC-GT, ADA-SCID patients displayed quasi-normal early B cell tolerance checkpoints, as evidenced by restored removal of developing autoreactive and ANA-expressing B cells. Hence, ADA plays an essential role in controlling autoreactive B cell counterselection by regulating BCR and TLR functions.
authors.affiliation: San Raffaele Telethon Institute for Gene Therapy (HSR-TIGET), Milan, Italy.
authors.forename: Aisha V
authors.initials: AV
authors.lastname: Sauer
authors.forename: Henner
authors.initials: H
authors.lastname: Morbach
authors.forename: Immacolata
authors.initials: I
authors.lastname: Brigida
authors.forename: Yen-Shing
authors.initials: YS
authors.lastname: Ng
authors.forename: Alessandro
authors.initials: A
authors.lastname: Aiuti
authors.forename: Eric
authors.initials: E
authors.lastname: Meffre
mesh_terms: D000243:Adenosine Deaminase / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D000328:Adult; D000974:Antibodies, Antinuclear / Q000276:immunology / Q000378:metabolism; D001402:B-Lymphocytes / Q000201:enzymology / Q000276:immunology*; D005260:Female; D015316:Genetic Therapy / Q000379:methods*; D018380:Hematopoietic Stem Cell Transplantation; D006801:Humans; D007108:Immune Tolerance; D008297:Male; D008875:Middle Aged; D011947:Receptors, Antigen, B-Cell / Q000235:genetics / Q000276:immunology*; D011948:Receptors, Antigen, T-Cell / Q000235:genetics / Q000276:immunology*; D016511:Severe Combined Immunodeficiency / Q000201:enzymology / Q000235:genetics / Q000276:immunology* / Q000628:therapy*; D014182:Transplantation, Autologous
chemical_list: D000974:Antibodies, Antinuclear; D011947:Receptors, Antigen, B-Cell; D011948:Receptors, Antigen, T-Cell; C548482:ADA protein, human; D000243:Adenosine Deaminase