DNA nanoparticle-mediated ABCA4 delivery rescues Stargardt dystrophy in mice

Abstract

Mutations in the photoreceptor-specific flippase ABCA4 are associated with Stargardt disease and many other forms of retinal degeneration that currently lack curative therapies. Gene replacement is a logical strategy for ABCA4-associated disease, particularly given the current success of traditional viral-mediated gene delivery, such as with adeno-associated viral (AAV) vectors. However, the large size of the ABCA4 cDNA (6.8 kbp) has hampered progress in the development of genetic treatments. Nonviral DNA nanoparticles (NPs) can accommodate large genes, unlike traditional viral vectors, which have capacity limitations. We utilized an optimized DNA NP technology to subretinally deliver ABCA4 to Abca4-deficient mice. We detected persistent ABCA4 transgene expression for up to 8 months after injection and found marked correction of functional and structural Stargardt phenotypes, such as improved recovery of dark adaptation and reduced lipofuscin granules. These data suggest that DNA NPs may be an excellent, clinically relevant gene delivery approach for genes too large for traditional viral vectors.

Retbindin Is an Extracellular Riboflavin-binding Protein Found at the Photoreceptor/Retinal Pigment Epithelium Interface

“…Relative Quantitative Real Time-PCR-Relative quantitative real time-PCR was performed as described previously (27). Briefly, RNA was extracted from the various tissues shown in Fig.…”

Gene Therapy of ABCA4-Associated Diseases

“…This mouse model shows some of the clinical features associated with STGD1, such as accumulation of lipofuscin (A2E) in RPE (Weng et al 1999;Mata et al 2001), thickening of the RPE cells (Allocca et al 2008;Radu et al 2008;Conley et al 2012), delayed recovery from light desensitization (Weng et al 1999;Maiti et al 2006;Allocca et al 2008;Radu et al 2008), and thinning of the outer nuclear (PR cell) layer in albino KO mice (Radu et al 2008;Wu et al 2010a). In this mouse model, after subretinal injection of the CK30-NPs carrying the human ABCA4 gene, Han et al (2012) detected ABCA4 transgene expression for up to 8 months after injection and found both improved recovery of dark adaptation and reduced lipofuscin accumulation. These promising data have provided the first evidence of effective nonviral vector-mediated delivery of large genes, such as ABCA4, to the PR cell layer.…”

“…Given the success of CK30-NPs to mediate phenotypic rescue in rodent models of retinitis pigmentosa (Cai et al 2009(Cai et al , 2010 and their favorable safety and efficacy profile in a human clinical trial for cystic fibrosis (Konstan et al 2004). Han et al (2012) have recently tested CK30-NPs for ABCA4 delivery in the Abca4…”

DNA nanoparticles are safe and nontoxic in non-human primate eyes

“…2,3 We have shown that they efficiently transfect both photoreceptors 3,4 and the RPE, 2,4,5 and can improve the disease phenotype in the rds +/− and rhodopsin-knockout models of retinitis pigmentosa, 3,[6][7][8] the Abca4 −/− model of Stargardt's dystrophy, 9 and the Rpe65 −/− model of Leber's congenital amaurosis.…”

“…1 These NPs have also been successfully used in the lung and brain [10][11][12][13][14] and result in no toxic effects in the eye 5,6,15 even after repeated subretinal injection. 5 Perhaps most excitingly, these NPs have a large capacity; we have shown that they can successfully incorporate and deliver DNA of up to 14 kbp in photoreceptors (largest size tested) 9 without significant decrease in transduction efficiency, and others have demonstrated effective transfection in the lung with plasmids of up to 20 kbp (largest size tested). 16 These results confirm that the CK30PEG NP technology has advanced sufficiently to have the potential to be a successful addition to the available repertoire of clinical ocular gene delivery tools.…”