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Andras M Komaromy, Guo-jie Ye, Christine Harman, Kristin L Koehl, Gustavo D Aguirre, Savitri Mandapati, Jeffrey D Chulay; Long-term Cone ERG Functional Rescue in CNGB3 Mutant Achromatopsia Dogs by AAV-hCNGB3 Vectors Containing the PR1.7 Promoter and Packaged in AAV5, AAV9 or Mutant AAV2 Capsids. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):2066.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate the efficacy of an AAV vector expressing codon-optimized human CNGB3 (hCNGB3co) cDNA driven by a PR1.7 promoter compared to other cone-specific promoters for rescue of cone function in CNGB3 mutant dogs.
PR1.7 is a shorter version of the 2.1 kb human red cone opsin promoter (PR2.1). In non-human primates (NHPs) PR1.7 is much more efficient than PR2.1 in directing specific expression of GFP in L-, M- and S-cones (Ye et al., 2014). In CNGB3 mutant dogs, an AAV5 vector expressing hCNGB3 driven by PR2.1 achieved long-term cone functional rescue, but similar vectors containing shorter versions of the PR2.1 promoter (PR0.5 or 3LCR-PR0.5) resulted in only transient functional rescue (Komaromy et al., 2010). In the present study, the efficiency of cone functional rescue by AAV vectors expressing hCNGB3 or hCNGB3co cDNAs, driven by PR1.7 or PR2.1 promoters and packaged in AAV5, AAV9, or AAV2tYF mutant capsids, was evaluated in CNGB3 mutant dogs by subretinal injection. Photopic flicker ERG amplitudes were recorded at baseline and 8 and 12 weeks after vector injection in all animals, and once every 3 months thereafter in a subset of animals. Objective behavioral testing was also performed at different time points.
Rescue of cone ERG responses was observed in all eyes treated with AAV5-PR2.1-hCNGB3co (3/3), AAV5-PR2.1-hCNGB3 (5/5), AAV9-PR1.7-hCNGB3co (5/5), and AAV2tYF-PR1.7-hCNGB3co vector (5/5). There was less than a 2-fold difference in the magnitude of cone flicker ERG responses between eyes treated with vectors containing hCNGB3co or hCNGB3 cDNA (4.04±3.44 vs 2.35±1.25 μV) and between vectors packaged in AAV9 and AAV2tYF capsids (5.22±1.79 vs 2.71±0.96 μV). Two animals treated with AAV2tYF-PR1.7-hCNGB3co in one eye and AAV9-PR1.7-hCNGB3co in the other eye continued to show robust ERG responses for at least 8 months after treatment with no decrease in ERG amplitude.
AAV vectors expressing codon-optimized human CNGB3 driven by the PR1.7 cone-specific promoter achieved long-term cone functional rescue in CNGB3 mutant achromatopsia dogs. Because the PR1.7 promoter has also been shown to direct robust and specific gene expression in L-, M- and S-cones in NHPs, these results support the development of an AAV-PR1.7-hCNGB3co vector for treatment of patients with CNGB3-related achromatopsia.
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