Molecular mechanisms of immune deficiency in adenosine deaminase (ADA)-deficient SCID patients: implications for stem cell gene therapy

Cassani, Barbara (2007). Molecular mechanisms of immune deficiency in adenosine deaminase (ADA)-deficient SCID patients: implications for stem cell gene therapy. PhD thesis The Open University.

DOI: https://doi.org/10.21954/ou.ro.0000fa26

Abstract

Mutations in the Adenosine Deaminase (ADA) gene are responsible for a form of Severe Combined Immunodeficiency (SCID), explained by the lymphotoxic accumulation of ADA substrates, adenosine and 2’-deoxy-adenosine. Haematopoietic stem cells (HSCs)-based gene therapy (GT) has been shown to correct both the immune and metabolic defect of ADA-SCID children, thus providing a unique model to investigate the molecular mechanisms linking the altered purine metabolism to T cell dysfunction. We found that severely compromised effector functions in ADA-deficient T cells associate with an intrinsically reduced ERK1/2 signaling, a defective activation of CREB and possibly to an altered nuclear recruitment of NF-kB, as predicted by the decreased phosphorylation of IkBα. Conversely, in T-cell lines generated from patients after GT, the biochemical events following TCR-triggering occur properly, leading to restored effector functions. Remarkably, in ADA-deficient but not in gene-corrected T cells, exposure to 2’-deoxy-adenosine induces a strong inhibition of T cell activation. This effect is consistent with an aberrant A2A receptor-mediated signaling and PKA hyperactivation. To assess the long-term safety of GT, retroviral integration sites (RIS) were cloned and analyzed from transduced bone marrow-derived CD34+ cells before transplantation and from their multilineage progeny in five patients. RIS occur preferentially around transcription start sites and in gene-dense regions, favoring genes transcriptionally active in CD34+ cells at the time of transduction as well as genes expressed in T cells. However, preliminary quantitative transcript analysis, at clonal cell level, showed no significant alteration in expression of genes correlated with the nearby vector integration, in agreement with the normal gene expression profile and functional behavior of T cell population. Altogether, these results contribute to extend the present knowledge on the pathogenesis of ADA-SCID and demonstrate the efficacy and safety of HSC gene therapy as a treatment for this disease.

Viewing alternatives

Download history

Metrics

Public Attention

Altmetrics from Altmetric

Number of Citations

Citations from Dimensions

Item Actions

Export

About

Recommendations