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Blood, 22 October 2009, Vol. 114, No. 17, pp. 3546-3556. Prepublished online as a Blood First Edition Paper on August 18, 2009; DOI 10.1182/blood-2009-02-202085.
GENE THERAPY Integration of retroviral vectors induces minor changes in the transcriptional activity of T cells from ADA-SCID patients treated with gene therapy1 San Raffaele Telethon Institute for Gene Therapy (HSR-TIGET), Milan, Italy; 2 Department of Biomedical Sciences, University of Modena and Reggio Emilia, Modena, Italy; 3 Centro Universitario di Statistica per le Scienze Biomediche, Vita Salute San Raffaele University, Milan Italy; 4 Division of Allergy and Immunology, Miami Children's Hospital, FL; 5 Vita-Salute San Raffaele University, Milan, Italy; 6 Istituto Italiano di Tecnologia Unit of Molecular Neuroscience, Istituto Scientifico H. San Raffaele, Milan, Italy; and 7 University of Rome Tor Vergata, Rome, Italy
Gene transfer into hematopoietic stem cells by
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| Copyright © 2009 by American Society of Hematology Online ISSN: 1528-0020 | |||||||||
-retroviral vectors (RVs) is an effective treatment for inherited blood disorders, although potentially limited by the risk of insertional mutagenesis. We evaluated the genomic impact of RV integration in T lymphocytes from adenosine deaminase-deficient severe combined immunodeficiency (ADA-SCID) patients 10 to 30 months after infusion of autologous, genetically corrected CD34+ cells. Expression profiling on ex vivo T-cell bulk population revealed no difference with respect to healthy controls. To assess the effect of vector integration on gene expression at the single-cell level, primary T-cell clones were isolated from 2 patients. T-cell clones harbored either 1 (89.8%) or 2 (10.2%) vector copies per cell and displayed partial to full correction of ADA expression, purine metabolism, and T-cell receptor-driven functions. Analysis of RV integration sites indicated a high diversity in T-cell origin, consistently with the polyclonal T-cell receptor-Vβ repertoire. Quantitative transcript analysis of 120 genes within a 200-kb window around RV integration sites showed modest (2.8- to 5.2-fold) dysregulation of 5.8% genes in 18.6% of the T-cell clones compared with controls. Nonetheless, affected clones maintained a stable phenotype and normal in vitro functions. These results confirm that RV-mediated gene transfer for ADA-SCID is safe, and provide crucial information for the development of future gene therapy protocols. The trials described herein have been registered at 
