Figures & data
Figure 1 Pathogenesis of ADA deficiency
Table 1 Early ADA-SCID gene therapy clinical trials
Figure 2 Mechanisms of insertional mutagenesis.
Schematic representation of two copies of a provirus integrated upstream the regulatory regions and between exons 1 and 2 of a proto-oncogene. The full-length LTRs in the provirus are represented by black boxes L; P represents the promoter region of the gene; the numbered boxes represent the exons; the arrows represent the orientation of transcription. A) as reported in some of the patients of the SCID-X1 trials, the enhancer elements of the LTR can activate the expression of the proto-oncogene or B) as reported by Bokhoven et al in vitro,Citation80 fusion transcripts of viral RNA and cellular RNA are generated due to aberrant splicing between the splicing donor site downstream of the 5′ LTR and a splicing acceptor site upstream of exon 2 of the proto-oncogene.
Figure 3 Comparing the architecture of the γ retroviruses tested in SCID clinical trials and the design of the future generations of vectors.
The new generations of vectors for HSC gene therapy will be lentiviruses without enhancer regions in the LTRs and cellular promoters placed downstream of the major splicing donor site. Codon-optimized genes will be useful in models where overexpression is not a limit. The introduction of insulator sequences in the LTRs may provide another layer of safety particularly when the internal regulatory region includes enhancer elements. The WPRE region improves RNA processing and boosts SIN vector titers.
