Severe combined immunodeficiency (SCID) is a rare class of primary, inherited, immunodeficiency causing infants to suffer from persistent diarrhea, opportunistic infections and a failure to thrive. RAG proteins play a crucial role in the initiation of V(D)J recombination of immunoglobulin (Ig) and T-cell receptor (TCR) gene segments. Inactivating mutations in RAG1 or RAG2 lead to a developmental block at early checkpoints in B- and T-cell development. SCID can be cured by hematopoietic stem cell transplantation, but an HLA-matched donor is not always available. For two types of SCID, ADA- SCID and X-linked SCID, gammaretrovirus-based gene therapy has proven a successful treatment. For my thesis, several aspects of T-cell development and gene therapy were studied. A feature all forms of SCID have in common, is the occurrence of a block in T-cell development. Therefore, one of the studies in my thesis aimed at gaining more detailed knowledge of normal human T-cell development. Subsets corresponding to consecutive stages of human T- cell development were isolated and their gene expression profile was correlated to the T-cell receptor (TCR) gene rearrangement status. This analysis resulted in the identification of candidate factors involved in regulation of TCR gene rearrangements. In one of the X-linked SCID gene therapy trials using hematopoietic stem cells, lymphoproliferations were observed in four patients. In two cases, insertion of the therapeutic vector was found near the T- ALL oncogene LMO2. We found that gammaretrovirus-driven overexpression LMO2, but not the therapeutic IL2RG gene resulted in a block in human T-cell development. HIV-based vectors have been shown to have a more favorable integration pattern then gammaretroviruses, and self-inactivating (SIN) versions of this transfer system have been developed. We tested the feasibility of RAG gene therapy using HIV-based SIN vectors. We evaluated RAG1 and RAG2 gene transfer into hematopoietic stem cells using murine models for RAG-SCID. Correction of both T- and B-cell development was established when using a RAG2 transfer vector in Rag2-/- mice, showing proof-of-principle for the use of lentiviral SIN vectors for RAG gene transfer.

Dongen, Prof. Dr. J.J.M. van (promotor) Prof. Dr. G. Wagemaker (promotor) European Union Netherlands Organization for Health Research and Development
J.J.M. van Dongen (Jacques) , G. Wagemaker (Gerard)
Erasmus University Rotterdam
Erasmus MC: University Medical Center Rotterdam

Pike, K. (2007, November 21). Gene Therapy for RAG-deficient Severe Combined Immunodeficiency. Retrieved from