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Chad E Bigelow, Shawn M Hanks, Joanna Vrouvlianis, Oliver Turner, Gregory Argentieri, George Bounoutas, Vivian W Choi, Thaddeus P Dryja, Seshidhar Reddy Police, Bruce D Jaffee; A mouse model to assess gene therapy for RLBP1-associated retinal dystrophy. Invest. Ophthalmol. Vis. Sci. 2014;55(13):1640.
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© ARVO (1962-2015); The Authors (2016-present)
To develop a mouse model to test recombinant adeno-associated viral (rAAV) vectors for RLBP1 gene delivery to the eye.
Retinal morphology was evaluated in RLBP1+/+ and RLBP1-/- mice of 4, 10, and 16 months of age. Assessments were made by viewing sections stained with hematoxylin and eosin or by using image processing on a subset of the sections to determine retina and outer nuclear layer thickness. Dark-adapted electroretinograms (ERGs) were used to assess photoreceptor function in RLBP1+/+, RLBP1+/-, and RLBP1-/- mice. Dark-adapted photoreceptor function was compared between genotypes using a 15-step intensity response series (-1.0 to 3.7 log scot cd s m-2). The rate of dark adaptation was assessed by monitoring ERG a-wave amplitude recovery after a photobleach (16 xenon flashes: 3.7 log scot cd s m-2). In order to test the ability of gene delivery to restore visual function to RLBP1-/- mice, 3.6x108 vg/eye of AAV-pRLBP1-hRLBP1 vectors (NVS1 or NVS2) with different serotypes were injected subretinally. 12 weeks post-injection, recovery of a-wave amplitude (dark adaptation) 4 hours post-bleach was measured.
There were no notable differences in retinal morphology with age or between genotypes based on light microscopy examination or image processing. Dark-adapted photoreceptor function was also indistinguishable between genotypes. However, slow dark adaptation was observed in RLBP1-/- mice compared to wild-type or heterozygous controls. RLBP1+/+, RLBP1+/-, and RLBP1-/- groups at ~3 hours post-bleach exhibited a-wave recoveries of 89%, 97%, and 14%, respectively. Subretinal delivery of NVS1 or NVS2 increased the rate of dark adaptation in RLBP1-/- mice. Four hours post-photobleach, naïve eyes recovered 13% of a-wave amplitude compared to 38% (p<0.01) and 87% (p<0.001) for those receiving NVS1 or NVS2, respectively. Serotype-related efficacy differences were significant: eyes that received NVS2 exhibited a >2-fold increase in a-wave amplitude 4 hours post-bleach vs. those receiving NVS1 (p<0.001).
RLBP1-/- mice exhibit slow dark adaptation that is similar to the deficit observed in patients with RLBP1-associated retinal dystrophy. ERG-based assessments in this model indicate that the rate of dark adaptation can be substantially improved with viral vector-mediated gene delivery and that the assay possesses sufficient sensitivity to differentiate viral vectors with different properties.
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