Defective B cell tolerance in adenosine deaminase deficiency is corrected by gene therapy
Aisha V. Sauer, … , Alessandro Aiuti, Eric Meffre
Aisha V. Sauer, … , Alessandro Aiuti, Eric Meffre
Published May 24, 2012
Citation Information: J Clin Invest. 2012;122(6):2141-2152. https://doi.org/10.1172/JCI61788.
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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

Aisha V. Sauer, Henner Morbach, Immacolata Brigida, Yen-Shing Ng, Alessandro Aiuti, Eric Meffre

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Figure 7

ADA HSC-GT also restores the peripheral B cell tolerance checkpoint in ADA-SCID patients.

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ADA HSC-GT also restores the peripheral B cell tolerance checkpoint in ...
(A) Antibodies from mature naive B cells from 3 ADA-SCID patients were tested by ELISA for reactivity with HEp-2 cell lysate. Dotted lines show ED38-positive control. Horizontal lines show cutoff OD405 for positive reactivity. The frequencies of HEp-2–reactive and non–HEp-2–reactive clones are summarized in the pie charts, with the number of antibodies tested shown in the center. (B) The frequency of HEp-2–reactive clones in mature naive B cells of ADA-SCID patients was corrected after HSC-GT and comparable to HDs. (C) The frequencies of polyreactive (tested against dsDNA, insulin, and LPS) clones in mature naive B cells of post–HSC-GT ADA-SCID patients were significantly reduced, but remained higher than those in HDs. (D) The removal of ANA-expressing mature naive B cells was completely restored by HSC-GT. (B–D) Each symbol represents an individual, horizontal bars denote means, and dashed lines show the average frequency in HDs. *P ≤ 0.05. (E) Antibodies expressed by post–HSC-GT ADA-SCID mature naive B cells showed various cytoplasmic staining patterns and did not recognize nuclear structures. 2 examples for anti-cytoplasmic new emigrant B cells are shown for each patient. Original magnification, ×40.