Gene therapy restores vision in a canine model of childhood blindness

James A. Baker Institute for Animal Health, College of Veterinary Medicine, Cornell University, Ithaca, New York, USA.
Nature Genetics (Impact Factor: 29.65). 06/2001; 28(1):92-5. DOI: 10.1038/88327
Source: PubMed

ABSTRACT The relationship between the neurosensory photoreceptors and the adjacent retinal pigment epithelium (RPE) controls not only normal retinal function, but also the pathogenesis of hereditary retinal degenerations. The molecular bases for both primary photoreceptor and RPE diseases that cause blindness have been identified. Gene therapy has been used successfully to slow degeneration in rodent models of primary photoreceptor diseases, but efficacy of gene therapy directed at photoreceptors and RPE in a large-animal model of human disease has not been reported. Here we study one of the most clinically severe retinal degenerations, Leber congenital amaurosis (LCA). LCA causes near total blindness in infancy and can result from mutations in RPE65 (LCA, type II; MIM 180069 and 204100). A naturally occurring animal model, the RPE65-/- dog, suffers from early and severe visual impairment similar to that seen in human LCA. We used a recombinant adeno-associated virus (AAV) carrying wild-type RPE65 (AAV-RPE65) to test the efficacy of gene therapy in this model. Our results indicate that visual function was restored in this large animal model of childhood blindness.

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    • "Natural Mendelian dog mutants have been bred to study diseases such as muscular dystrophy and an early-onset childhood retinal dystrophy that can result from mutation in one of several genes (Leber congenital amaurosis). Both those models have shown significant clinical improvement, with gene therapy addressing the pathological mutations of Dystrophin and RPE65, respectively (Acland et al. 2001; Bainbridge et al. 2008 "
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    ABSTRACT: Here, we briefly review the state of knowledge of human cancer genetics to elaborate on the need for different types of mammalian models, highlighting the strengths of the dog. Mouse models are unparalleled for their experimental tractability and rapid genetic manipulation but have some key limitations in the area of human relevance. Companion dog models are attractive, because they are genetically more similar to humans, share environmental exposures with their owners, suffer from the same diseases as humans, and receive a high level of health care. They are ideal for the study of chronic diseases, because they age five to eight times faster than humans and generally live to old age. In addition, each dog breed is on the order of 100-fold genetically simpler than the whole human or dog population. These traits make the dog ideal for the study of complex genetics of naturally occurring cancers. Here, we contrast the relative strengths of cancer genetics in humans and dogs. We propose that humans are most ideal for the study of somatic cancer genetics, whereas dogs are most ideal for germline genetics. That proposition is supported by comparison of genome-wide association studies (GWASs) in human and canine cancer. One of the advantages of dog cancer GWASs is the ability to rapidly map complex traits, conduct fine mapping and identification of causative variation, and thus be in a position to move on to functional studies. We mention how these strengths of dog models will lead to rapid advances in translational medicine.
    ILAR journal / National Research Council, Institute of Laboratory Animal Resources 06/2014; 55(1):16-45. DOI:10.1093/ilar/ilu010 · 1.05 Impact Factor
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    • "The sensitivity of the conventional ERG is also limited because of the distance between the recording electrode placed on the surface of the cornea and the retina where the ERG signals originate (Brown, 1968). Consequently, subjects with profoundly depressed ERG responses can retain significant visually mediated behavior (Acland et al., 2001; Melillo et al., 2012; Narfstrom et al., 2003a, b). In addition, the PLR can be elicited with significantly dimmer stimuli than can the ERG (Whiting et al., 2013c; Yao et al., 2006). "
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    ABSTRACT: Late-infantile neuronal ceroid lipofuscinosis (CLN2) is a hereditary neurological disorder characterized by progressive retinal degeneration and vision loss, cognitive and motor decline, seizures, and pronounced brain atrophy. The progressive loss of neurological functions eventually leads to death, usually by the early teenage years. Utilizing a canine model of CLN2, therapeutic studies to inhibit the brain and retinal degenerations are currently under way. Using this dog model, studies were undertaken to compare quantitative assessments of the pupillary light reflex (PLR) and electroretinography (ERG) as tools for evaluating the effects of the disease on retinal function. The PLR and ERG were recorded in normal and CLN2-affected Dachshunds at 2 month intervals between the ages of 4 and 10 months. Using custom instrumentation for quantitative PLR assessments, a series of white light stimuli of varying intensity was used to elicit pupil constriction, and pupil images were recorded using continuous infrared illumination and an infrared-sensitive camera. Electroretinography was used to evaluate retinal function in the same dogs. As the disease progressed, affected dogs exhibited progressive and profound declines in ERG amplitudes under both scotopic and photopic conditions. With low intensity light stimuli, CLN2 was also accompanied by progressive deficits in the PLR. Changes in the PLR to dim light stimuli included significant deficits in latency, constriction velocity, constriction amplitude, and redilation velocity. However, despite the almost complete loss of detectable ERG responses by disease end stage, the PLR to bright stimuli was well preserved throughout the disease progression. These findings demonstrate that the PLR is much more sensitive than the ERG in detecting residual retinal function in animal models of retinal degenerative disease. The preservation of the PLR in dogs with profoundly depressed ERGs correlates with a preservation of visually-mediated behavior even late in the disease progression. Quantitative analysis of the PLR has potential as a biomarker in animal models of retinal degenerative diseases and in evaluating the efficacy of therapeutic interventions in preserving retinal function.
    Experimental Eye Research 10/2013; 116. DOI:10.1016/j.exer.2013.10.006 · 3.02 Impact Factor
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    • "Loss of function prior to marked degeneration of photoreceptors provides a ''window of opportunity'' for gene augmentation therapy. The initial proof-of-principle studies in young Rpe65-deficient dogs showed that subretinally delivered recombinant adeno-associated viral (rAAV) vectors expressing either human or canine RPE65 dramatically improved photoreceptor function as assessed by ERG, vision-testing performance, and retinal-mediated visual cortex activity (Acland et al., 2001; Narfströ m et al., 2003; Acland et al., 2005; Aguirre et al., 2007). Similar dramatic improvements in retinal function were achieved in young Rpe65-/- and Rpe65 rd12/rd12 mice treated by rAAV-RPE65 subretinal injection (Dejneka et al., 2004; Pang et al., 2006; Roman et al., 2007; Bennicelli et al., 2008). "
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    ABSTRACT: Aims: Young Rpe65-deficient dogs have been used as a model for human RPE65 Leber congenital amaurosis (RPE65-LCA) in proof-of-concept trials of recombinant adeno-associated virus (rAAV) gene therapy. However, there are relatively few reports of the outcome of rAAV gene therapy in Rpe65-deficient dogs older than two years of age. The purpose of this study was to investigate the success of this therapy in older Rpe65-deficient dogs. Results: Thirteen eyes were treated in dogs aged between 2 and 6 years. A rAAV2 vector expressing the human RPE65 cDNA driven by the human RPE65 promoter was delivered by subretinal injection. Twelve of the thirteen eyes had improved retinal function as assessed by electroretinography and all showed improvement in vision at low lighting intensities. Histologic examination of 5 of the eyes was performed but found no correlation between ERG rescue and numbers of remaining photoreceptors. Conclusions: We conclude that functional rescue is still possible in older dogs and that the use of older Rpe65-deficient dogs, rather than young Rpe65-deficient dogs that have very little loss of photoreceptors more accurately models the situation when treating human RPE65-LCA patients.
    Human gene therapy 09/2013; 24(10). DOI:10.1089/hum.2013.146 · 3.62 Impact Factor
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