Clonality analysis after retroviral-mediated gene transfer to CD34+ cells from the cord blood of ADA

Abstract

A clinical trial of retroviral-mediated transfer of the adenosine deaminase (ADA) gene into umbilical cord blood CD34+ cells was started in 1993. ADA-containing peripheral blood mononuclear cells (PBMCs) have persisted in patients from this trial, with T lymphocytes showing the highest prevalence of gene marking1,2. To gain a greater understanding of the nature and number of the transduced cells that were engrafted, we used linear amplification–mediated PCR (LAM-PCR) to identify clonal vector proviral integrants3,4. In one patient, a single vector integrant was predominant in T lymphocytes at a stable level over most of the eight-year time span analyzed and was also detected in some myeloid samples. T-cell clones with the predominant integrant, isolated after eight years, showed multiple patterns of T-cell receptor (TCR) gene rearrangement, indicating that a single pre-thymic stem or progenitor cell served as the source of the majority of the gene-marked cells over an extended period of time. It is important to distinguish the stable pattern of monoclonal gene marking that we observed here from the progressive increase of a T-cell clone with monoclonal gene marking that results from leukemic transformation, as observed in two subjects in a clinical trial of gene therapy for X-linked severe combined immunodeficiency (SCID)5,6.

Cite this article

Schmidt, M., Carbonaro, D., Speckmann, C. et al. Clonality analysis after retroviral-mediated gene transfer to CD34⁺ cells from the cord blood of ADA-deficient SCID neonates. Nat Med 9, 463–468 (2003). https://doi.org/10.1038/nm844

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