[Show abstract][Hide abstract] ABSTRACT: Autosomal recessive retinitis pigmentosa (RP), a heterogeneous group of degenerations of the retina, can be due to mutations in the MFRP (membrane-type frizzled-related protein) gene. A patient with RP with MFRP mutations, one of which is novel and the first splice site mutation reported, was characterized by noninvasive retinal and visual studies. The phenotype, albeit complex, suggested that this retinal degeneration may be a candidate for gene-based therapy. Proof-of-concept studies were performed in the rd6 Mfrp mutant mouse model. The fast-acting tyrosine-capsid mutant AAV8 (Y733F) vector containing the small chicken β-actin promoter driving the wild-type mouse Mfrp gene was used. Subretinal vector delivery on postnatal day 14 prevented retinal degeneration. Treatment rescued rod and cone photoreceptors, as assessed by electroretinography and retinal histology at 2 months of age. This AAV-mediated gene delivery also resulted in robust MFRP expression predominantly in its normal location within the retinal pigment epithelium apical membrane and its microvilli. The clinical features of MFRP-RP and our preliminary data indicating a response to gene therapy in the rd6 mouse suggest that this form of RP is a potential target for gene-based therapy.
Human gene therapy 12/2011; 23(4):367-76. DOI:10.1089/hum.2011.169 · 3.76 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The authors previously showed that subretinal delivery of AAV5 vectors containing murine guanylate cyclase-1 (GC1) cDNA driven by either photoreceptor-specific (hGRK1) or ubiquitous (smCBA) promoters was capable of restoring cone-mediated function and visual behavior and preserving cone photoreceptors in the GC1 knockout (GC1KO) mouse for 3 months. Here, the authors compared therapy conferred by the aforementioned vectors to that achieved with the highly efficient capsid tyrosine mutant AAV8(Y733F) and asked whether long-term therapy is achievable in this model.
AAV5-hGRK1-mGC1, AAV5-smCBA-mGC1, or AAV8(Y733F)-hGRK1-mGC1 was delivered subretinally to GC1KO mice between postnatal day (P)14 and P25. Retinal function was assayed by electroretinography. Localization of AAV-mediated GC1 expression and cone survival were assayed with immunohistochemistry, and the spread of vector genomes beyond the retina was quantified by PCR of optic nerve and brain tissue.
Cone function was restored with all vectors tested, with AAV8(Y733F) being the most efficient. Electroretinographic responses were clearly measurable out to 1 year after treatment. AAV-mediated expression of GC1 was found exclusively in photoreceptors out to 15 months after injection. Cones were preserved for at least 11 months after treatment. AAV5- and AAV8(733)-delivered vector genomes were recovered primarily from optic nerve of the treated eye and, in only instance, from brain (1 of 20 samples).
The authors demonstrate for the first time that long-term therapy (∼1 year) is achievable in a mammalian model of GC1 deficiency. These data provide additional justification for the development of an AAV-based gene therapy vector for the clinical treatment of Leber congenital amaurosis-1.
[Show abstract][Hide abstract] ABSTRACT: Vectors based on adeno-associated virus serotype 2 (AAV2) have been used extensively in many gene-delivery applications, including several successful clinical trials for one type of Leber congenital amaurosis in the retina. Many studies have focused on improving AAV2 transduction efficiency and cellular specificity by genetically engineering its capsid. We have previously shown that vectors-containing single-point mutations of capsid surface tyrosines in serotypes AAV2, AAV8, and AAV9 displayed significantly increased transduction efficiency in the retina compared with their wild-type counterparts. In the present study, we evaluated the transduction characteristics of AAV2 vectors containing combinations of multiple tyrosine to phenylalanine mutations in seven highly conserved surface-exposed capsid tyrosine residues following subretinal or intravitreal delivery in adult mice. The multiply mutated vectors exhibited different in vivo transduction properties, with some having a unique ability of transgene expression in all retinal layers. Such novel vectors may be useful in developing valuable new therapeutic strategies for the treatment of many genetic diseases.
[Show abstract][Hide abstract] ABSTRACT: Recessive mutations in guanylate cyclase-1 (Gucy2d) are associated with severe, early onset Leber congenital amaurosis-1(LCA1). Gucy2d encodes guanylate cyclase (GC1) is expressed in photoreceptor outer segment membranes and produces cGMP in these cells. LCA1 patients present in infancy with severely impaired vision and extinguished electroretinogram (ERG) but retain some photoreceptors in both their macular and peripheral retina for years. Like LCA1 patients, loss of cone function in the GC1 knockout (GC1KO) mouse precedes cone degeneration. The purpose of this study was to test whether delivery of functional GC1 to cone cells of the postnatal GC1KO mouse could restore function to these cells.
Serotype 5 AAV vectors containing either a photoreceptor-specific, rhodopsin kinase (hGRK1) or ubiquitous (smCBA) promoter driving expression of wild type murine GC1 were subretinally delivered to one eye of P14 GC1KO mice. Visual function (ERG) was analyzed in treated and untreated eyes until 3 months post injection. AAV-treated, isogenic wild type and uninjected control mice were evaluated for restoration of visual behavior using optomotor testing. At 3 months post injection, all animals were sacrificed, and their treated and untreated retinas assayed for expression of GC1 and localization of cone arrestin. Cone-mediated function was restored to treated eyes of GC1KO mice (ERG amplitudes were approximately 45% of normal). Treatment effect was stable for at least 3 months. Robust improvements in cone-mediated visual behavior were also observed, with responses of treated mice being similar or identical to that of wild type mice. AAV-vectored GC1 expression was found in photoreceptors and cone cells were preserved in treated retinas.
This is the first demonstration of gene-based restoration of both visual function/vision-elicited behavior and cone preservation in a mammalian model of GC1 deficiency. Importantly, results were obtained using a well characterized, clinically relevant AAV vector. These results lay the ground work for the development of an AAV-based gene therapy vector for the treatment of LCA1.
PLoS ONE 06/2010; 5(6):e11306. DOI:10.1371/journal.pone.0011306 · 3.23 Impact Factor