Long-term retinal cone rescue using a capsid mutant AAV8 vector in a mouse model of CNGA3-achromatopsia

PLOS ONE, Nov 2019

Adeno-associated virus (AAV) vectors are important gene delivery tools for the treatment of many recessively inherited retinal diseases. For example, a wild-type (WT) AAV5 vector can deliver a full-length Cnga3 (cyclic nucleotide-gated channel alpha-3) cDNA to target cells of the cone photoreceptor function loss 5 (cpfl5) mouse, a spontaneous animal model of achromatopsia with a Cnga3 mutation. Gene therapy restores cone-mediated function and blocks cone degeneration in the mice. However, since transgene expression delivered by an AAV vector shows relatively short-term effectiveness, this cannot be regarded as a very successful therapy. AAV2 and AAV8 vectors with capsid mutations have significantly enhanced transduction efficiency in retinas compared to WT AAV controls. In this study, AAV8 (Y447, 733F+T494V)-treated cpfl5 retinas showed greater preservation of short-term cone electroretinogram (ERG) responses than AAV8 (Y447, 733F)- or AAV2 (Y272, 444, 500, 730F+T491V)-mediated treatments. To explore the long-term rescue effect, AAV8 (Y447, 733F+T494V)-treated cpfl5 retinas were evaluated at 9 months following postnatal day 14 (P14) treatment. Rescued ERG responses in the cones of treated cpfl5 eyes decreased with increasing age, but still maintained more than 60% of the WT mouse responses at the oldest time point examined. Expression of CNGA3 and M/S-opsins was maintained in cone outer segments of the treated cpfl5 eyes and was equal to expression in age-matched WT retinas. Near-normal cone-mediated water maze behavior was observed in the treated cpfl5 mice. As these are the longest follow-up data reported thus far, AAV8 with capsid Y-F and T-V mutations may be one of the most effective AAV vectors for long-term treatment in a naturally occurring mouse model of CNGA3 achromatopsia.

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Long-term retinal cone rescue using a capsid mutant AAV8 vector in a mouse model of CNGA3-achromatopsia

November Long-term retinal cone rescue using a capsid mutant AAV8 vector in a mouse model of CNGA3-achromatopsia Xufeng Dai 0 1 Ying He¤ 0 1 Hua Zhang 0 1 Yangyang Zhang 0 1 Yan Liu 0 1 Muran Wang 0 1 Hao Chen 0 1 Ji- jing Pang 0 1 0 School of Ophthalmology and Optometry, The Eye Hospital, Wenzhou Medical University , Wenzhou, Zhejiang , P.R. China 1 Editor: Anand Swaroop, National Eye Institute , UNITED STATES Adeno-associated virus (AAV) vectors are important gene delivery tools for the treatment of many recessively inherited retinal diseases. For example, a wild-type (WT) AAV5 vector can deliver a full-length Cnga3 (cyclic nucleotide-gated channel alpha-3) cDNA to target cells of the cone photoreceptor function loss 5 (cpfl5) mouse, a spontaneous animal model of achromatopsia with a Cnga3 mutation. Gene therapy restores cone-mediated function and blocks cone degeneration in the mice. However, since transgene expression delivered by an AAV vector shows relatively short-term effectiveness, this cannot be regarded as a very successful therapy. AAV2 and AAV8 vectors with capsid mutations have significantly enhanced transduction efficiency in retinas compared to WT AAV controls. In this study, AAV8 (Y447, 733F+T494V)-treated cpfl5 retinas showed greater preservation of short-term cone electroretinogram (ERG) responses than AAV8 (Y447, 733F)- or AAV2 (Y272, 444, 500, 730F+T491V)-mediated treatments. To explore the long-term rescue effect, AAV8 (Y447, 733F+T494V)-treated cpfl5 retinas were evaluated at 9 months following postnatal day 14 (P14) treatment. Rescued ERG responses in the cones of treated cpfl5 eyes decreased with increasing age, but still maintained more than 60% of the WT mouse responses at the oldest time point examined. Expression of CNGA3 and M/S-opsins was maintained in cone outer segments of the treated cpfl5 eyes and was equal to expression in age-matched WT retinas. Near-normal cone-mediated water maze behavior was observed in the treated cpfl5 mice. As these are the longest follow-up data reported thus far, AAV8 with capsid Y-F and T-V mutations may be one of the most effective AAV vectors for long-term treatment in a naturally occurring mouse model of CNGA3 achromatopsia. Data Availability Statement; All relevant data are within the paper Introduction Achromatopsia, also known as rod monochromatism, is a relatively rare autosomal recessive retinal disorder characterized by cone photoreceptor dysfunction. Clinically, the disease is generally classified into complete (typical) and incomplete (atypical) forms [ 1 ]. Typical symptoms of collection and analysis, decision to publish, or preparation of the manuscript. complete achromatopsia are more severe than the incomplete form. They include seriously reduced visual acuity, nystagmus, photophobia, and color blindness [ 1 ]. With only rod-mediated vision, patients are extremely sensitive to light and have daylight blindness. To reduce photophobia, currently available medical care is to limit light exposure using dark glasses. With the development of adeno-associated virus (AAV) vectors as gene delivery tools for many recessively inherited retinal diseases, several promising gene therapy projects have been initiated [2±9]. Recent preclinical trials have made significant progress in providing effective treatment for achromatopsia. The first clinical trials of gene therapy are either underway or will be launched soon and they are expected to contribute important data on the safety and efficacy of these treatments [ 10 ]. Thus far, six genes have been implicated in achromatopsia-associated mutations [11±15]: cyclic nucleotide-gated channel alpha-3 (Cnga3) [ 16,17 ], cyclic nucleotide-gated channel beta3 (Cngb3) [ 18,19 ], guanine nucleotide binding protein alpha transduction active peptide 2 (Gnat2) [ 1,20 ], phosphodiesterase 6C (Pde6c) [ 21,22 ], Pde6h [ 12,13 ], and cyclic AMP-dependent activating transcription factor-6 alpha (Atf6) [ 14,15 ]. The proteins encoded by these genes play vital roles in the phototransduction cascade of cone photoreceptors. The Cnga3 gene encodes a member of the cyclic nucleotide-gated ion channel protein family, which is critical for normal vision in cone photoreceptors [23]. As the first identified and second most common cause of achromatopsia, Cnga3 mutations account for approximately 25% of all cases [ 24,25 ]. A cone photoreceptor function loss 5 (cpfl5) mouse strain, with a naturally occurring Cnga3 mutation, was discovered at The Jackson Laboratory [11]. Due to a single nucleotide A to G transition at position 492 of exon 5, the deficient mice exhibit selective loss of cone-mediated electroretinogram (ERG) responses [ 11 ]. In addition, it has been shown that loss of CNGA3 results in impaired expression and trafficking of cone opsins [ 11,26 ]. New generations of viral vectors have made it possible to deliver functional genes to retinal cells [ 27 ]. Gene therapy, which can r (...truncated)


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Xufeng Dai, Ying He, Hua Zhang, Yangyang Zhang, Yan Liu, Muran Wang, Hao Chen, Ji-jing Pang. Long-term retinal cone rescue using a capsid mutant AAV8 vector in a mouse model of CNGA3-achromatopsia, PLOS ONE, 2017, Volume 12, Issue 11, DOI: 10.1371/journal.pone.0188032