The Sleeping Beauty transposon system: a non-viral vector for gene therapy

Abstract

Over the past decade, the Sleeping Beauty (SB) transposon system has been developed as the leading non-viral vector for gene therapy. This vector combines the advantages of viruses and naked DNA. Here we review progress over the last 2 years in vector design, methods of delivery and safety that have supported its use in the clinic. Currently, the SB vector has been validated for ex vivo gene delivery to stem cells, including T-cells for the treatment of lymphoma. Progress in delivery of SB transposons to liver for treatment of various systemic diseases, such as hemophilia and mucopolysaccharidoses types I and VII, has encountered some problems, but even here progress is being made.

Figure 1.

History of some vectors used for human gene therapy. For each type of vector, the lines indicate the period between its discovery and its use for gene transfer (in the case of retroviruses and lentiviruses, the initial virus discovered and the virus actually used for gene therapy are indicated by dashed and solid lines, respectively). Rectangles show the period of use for each vector as a gene transfer agent and the arrowheads indicate its use in humans. SB transposons were synthetically made and therefore validated by their use for gene transfer into cultured cells. Hence, they have no associated line; the first clinical trial has been initiated. LV, lentiviruses; AAV, adeno-associated viruses; AdV, adenoviruses; RV, retroviruses.

Figure 2.

SB transposon-mediated gene transfer into chromosomal DNA for long-term expression of a therapeutic gene. An SB transposon (the inverted arrowheads) in a plasmid provides only transient expression of a transgene from a promoter unless transposed into a host genome. There are several methods for delivery of the transposon system into a cell based on whether the cell is in culture (electroporation or transfection) or in a tissue (e.g. hydrodynamic injection). In most studies, the source of the SB transposase is a gene on either the same (shown here) or a different plasmid as that harboring the transposon.

Figure 3.

Success in clinical trials depends on three aspects of a vector such as its efficacy, its delivery and its safety. Recent developments in each of these areas support the application of the SBTS in clinical trials.