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Fenner BJ, Tan TE, Barathi AV, Tun SBB, Yeo SW, Tsai ASH, Lee SY, Cheung CMG, Chan CM, Mehta JS, Teo KYC. Gene-Based Therapeutics for Inherited Retinal Diseases. Front Genet 2022; 12:794805. [PMID: 35069693 PMCID: PMC8782148 DOI: 10.3389/fgene.2021.794805] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Accepted: 12/14/2021] [Indexed: 12/14/2022] Open
Abstract
Inherited retinal diseases (IRDs) are a heterogenous group of orphan eye diseases that typically result from monogenic mutations and are considered attractive targets for gene-based therapeutics. Following the approval of an IRD gene replacement therapy for Leber's congenital amaurosis due to RPE65 mutations, there has been an intensive international research effort to identify the optimal gene therapy approaches for a range of IRDs and many are now undergoing clinical trials. In this review we explore therapeutic challenges posed by IRDs and review current and future approaches that may be applicable to different subsets of IRD mutations. Emphasis is placed on five distinct approaches to gene-based therapy that have potential to treat the full spectrum of IRDs: 1) gene replacement using adeno-associated virus (AAV) and nonviral delivery vectors, 2) genome editing via the CRISPR/Cas9 system, 3) RNA editing by endogenous and exogenous ADAR, 4) mRNA targeting with antisense oligonucleotides for gene knockdown and splicing modification, and 5) optogenetic approaches that aim to replace the function of native retinal photoreceptors by engineering other retinal cell types to become capable of phototransduction.
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Affiliation(s)
- Beau J Fenner
- Singapore National Eye Centre, Singapore, Singapore.,Singapore Eye Research Institute, Singapore, Singapore.,Duke-NUS Graduate Medical School, Ophthalmology and Visual Sciences Academic Clinical Programme, Singapore, Singapore
| | - Tien-En Tan
- Singapore National Eye Centre, Singapore, Singapore.,Singapore Eye Research Institute, Singapore, Singapore.,Duke-NUS Graduate Medical School, Ophthalmology and Visual Sciences Academic Clinical Programme, Singapore, Singapore
| | | | - Sai Bo Bo Tun
- Singapore Eye Research Institute, Singapore, Singapore
| | - Sia Wey Yeo
- Singapore Eye Research Institute, Singapore, Singapore
| | - Andrew S H Tsai
- Singapore National Eye Centre, Singapore, Singapore.,Singapore Eye Research Institute, Singapore, Singapore.,Duke-NUS Graduate Medical School, Ophthalmology and Visual Sciences Academic Clinical Programme, Singapore, Singapore
| | - Shu Yen Lee
- Singapore National Eye Centre, Singapore, Singapore.,Singapore Eye Research Institute, Singapore, Singapore.,Duke-NUS Graduate Medical School, Ophthalmology and Visual Sciences Academic Clinical Programme, Singapore, Singapore
| | - Chui Ming Gemmy Cheung
- Singapore National Eye Centre, Singapore, Singapore.,Singapore Eye Research Institute, Singapore, Singapore.,Duke-NUS Graduate Medical School, Ophthalmology and Visual Sciences Academic Clinical Programme, Singapore, Singapore
| | - Choi Mun Chan
- Singapore National Eye Centre, Singapore, Singapore.,Singapore Eye Research Institute, Singapore, Singapore.,Duke-NUS Graduate Medical School, Ophthalmology and Visual Sciences Academic Clinical Programme, Singapore, Singapore
| | - Jodhbir S Mehta
- Singapore National Eye Centre, Singapore, Singapore.,Singapore Eye Research Institute, Singapore, Singapore.,Duke-NUS Graduate Medical School, Ophthalmology and Visual Sciences Academic Clinical Programme, Singapore, Singapore.,School of Material Science and Engineering, Nanyang Technological University, Singapore, Singapore.,Yong Loo Lin School of Medicine, Department of Ophthalmology, National University of Singapore, Singapore, Singapore
| | - Kelvin Y C Teo
- Singapore National Eye Centre, Singapore, Singapore.,Singapore Eye Research Institute, Singapore, Singapore.,Duke-NUS Graduate Medical School, Ophthalmology and Visual Sciences Academic Clinical Programme, Singapore, Singapore
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Effects of Altering HSPG Binding and Capsid Hydrophilicity on Retinal Transduction by AAV. J Virol 2021; 95:JVI.02440-20. [PMID: 33658343 PMCID: PMC8139652 DOI: 10.1128/jvi.02440-20] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Adeno-associated viruses (AAVs) have recently emerged as the leading vector for retinal gene therapy. However, AAV vectors which are capable of achieving clinically relevant levels of transgene expression and widespread retinal transduction are still an unmet need. Using rationally designed AAV2-based capsid variants, we investigate the role of capsid hydrophilicity and hydrophobicity as it relates to retinal transduction. We show that hydrophilic, single amino acid (aa) mutations (V387R, W502H, E530K, L583R) in AAV2 negatively impact retinal transduction when heparan sulfate proteoglycan (HSPG) binding remains intact. Conversely, addition of hydrophobic point mutations to an HSPG binding deficient capsid (AAV2ΔHS) lead to increased retinal transduction in both mouse and macaque. Our top performing vector, AAV2(4pMut)ΔHS, achieved robust rod and cone photoreceptor (PR) transduction in macaque, especially in the fovea, and demonstrates the ability to spread laterally beyond the borders of the subretinal injection (SRI) bleb. This study both evaluates biophysical properties of AAV capsids that influence retinal transduction, and assesses the transduction and tropism of a novel capsid variant in a clinically relevant animal model.ImportanceRationally guided engineering of AAV capsids aims to create new generations of vectors with enhanced potential for human gene therapy. By applying rational design principles to AAV2-based capsids, we evaluated the influence of hydrophilic and hydrophobic amino acid (aa) mutations on retinal transduction as it relates to vector administration route. Through this approach we identified a largely deleterious relationship between hydrophilic aa mutations and canonical HSPG binding by AAV2-based capsids. Conversely, the inclusion of hydrophobic aa substitutions on a HSPG binding deficient capsid (AAV2ΔHS), generated a vector capable of robust rod and cone photoreceptor (PR) transduction. This vector AAV2(4pMut)ΔHS also demonstrates a remarkable ability to spread laterally beyond the initial subretinal injection (SRI) bleb, making it an ideal candidate for the treatment of retinal diseases which require a large area of transduction.
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Zhu D, Schieferecke AJ, Lopez PA, Schaffer DV. Adeno-Associated Virus Vector for Central Nervous System Gene Therapy. Trends Mol Med 2021; 27:524-537. [PMID: 33895085 DOI: 10.1016/j.molmed.2021.03.010] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2020] [Revised: 03/15/2021] [Accepted: 03/22/2021] [Indexed: 12/14/2022]
Abstract
The past several years have witnessed significant advances in the development of therapeutic gene delivery for neurological disorders of the central nervous system (CNS). In particular, genome-wide sequencing analysis has deepened our understanding of mutations that underlie many monogenic disorders, which in turn has contributed to clinical advances involving adeno-associated virus (AAV) vector delivery of replacement genes to treat recessive disorders. Moreover, gene therapy has been further bolstered with advances in genome editing tools that allow researchers to silence, repair, and amend endogenous genes. However, despite strong preclinical and clinical progress, challenges remain, including delivery and safety. Here, we discuss advances in AAV engineering, recent developments in cargo design, and translation of these technologies towards clinical progress.
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Affiliation(s)
- Danqing Zhu
- California Institute for Quantitative Biosciences, University of California, Berkeley, CA, 94720, USA
| | - Adam J Schieferecke
- Department of Molecular and Cell Biology, University of California, Berkeley, CA, 94720, USA
| | - Paola A Lopez
- Department of Bioengineering, University of California, Berkeley, CA, 94720, USA
| | - David V Schaffer
- California Institute for Quantitative Biosciences, University of California, Berkeley, CA, 94720, USA; Department of Molecular and Cell Biology, University of California, Berkeley, CA, 94720, USA; Department of Bioengineering, University of California, Berkeley, CA, 94720, USA; Department of Chemical and Biomolecular Engineering, University of California, Berkeley, CA, 94720, USA; Helen Wills Neuroscience Institute, University of California, Berkeley, CA, 94720, USA.
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Ghaderi S, Ahmadian S, Soheili ZS, Ahmadieh H, Samiei S, Kheitan S, Pirmardan ER. AAV delivery of GRP78/BiP promotes adaptation of human RPE cell to ER stress. J Cell Biochem 2017; 119:1355-1367. [PMID: 28782832 DOI: 10.1002/jcb.26296] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2017] [Accepted: 07/18/2017] [Indexed: 12/14/2022]
Abstract
Adeno associated virus (AAV)-mediated gene delivery of GRP78 (78 kDa glucose-regulated protein) attenuates the condition of endoplasmic reticulum (ER) stress and prevents apoptotic loss of photoreceptors in Retinitis pigmentosa (RP) rats. In the current study we overexpressed Grp78 with the help of AAV-2 in primary human retinal pigmented epithelium (hRPE) cell cultures and examined its effect on cell response to ER stress. The purpose of this work was studying potential stimulating effect of GRP78 on adaptation/pro-survival of hRPE cells under ER stress, as an in vitro model for RPE degeneration. To investigate the effect of Grp78 overexpression on unfolded protein response (UPR) markers under ER stress, hRPE primary cultures were transduced by recombinant virus rAAV/Grp78, and treated with ER stressor drug, tunicamycin. Expression changes of four UPR markers including GRP78, PERK, ATF6α, and GADD153/CHOP, were assessed by real-time PCR and western blotting. We found that GRP78 has a great contribution in modulation of UPR markers to favor adaptive response in ER-stressed hRPE cells. In fact, GRP78 overexpression affected adaptation and apoptotic phases of early UPR, through enhancement of two master regulators/ER stress sensors (PERK and ATF6α) and down-regulation of a key pro-apoptotic cascade activator (GADD153/CHOP). Together these findings demonstrate the promoting effect of GRP78 on adaptation/pro-survival of hRPE cells under ER stress. This protein with anti-apoptotic actions in the early UPR and important role in cell fate regulation, can be recruited as a useful candidate for future investigations of RPE degenerative diseases.
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Affiliation(s)
- Shima Ghaderi
- Institute of Biochemistry and Biophysics, University of Tehran, Tehran, Iran
| | - Shahin Ahmadian
- Institute of Biochemistry and Biophysics, University of Tehran, Tehran, Iran
| | - Zahra-Soheila Soheili
- Ministry of Science, Research and Technology, National Institute of Genetic Engineering and Biotechnology, Tehran, Iran
| | - Hamid Ahmadieh
- Ophthalmic Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Shahram Samiei
- Blood Transfusion Research Center, High Institute for Research and Education in Transfusion Medicine, Tehran, Iran
| | - Samira Kheitan
- Ministry of Science, Research and Technology, National Institute of Genetic Engineering and Biotechnology, Tehran, Iran
| | - Ehsan R Pirmardan
- Faculty of Biological Sciences, Tarbiat Modares University, Tehran, Iran
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Heparan Sulfate Binding Promotes Accumulation of Intravitreally Delivered Adeno-associated Viral Vectors at the Retina for Enhanced Transduction but Weakly Influences Tropism. J Virol 2016; 90:9878-9888. [PMID: 27558418 DOI: 10.1128/jvi.01568-16] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2016] [Accepted: 08/15/2016] [Indexed: 12/20/2022] Open
Abstract
Many adeno-associated virus (AAV) serotypes efficiently transduce the retina when delivered to the subretinal space but show limited success when delivered to the vitreous due to the inner limiting membrane (ILM). Subretinal delivery of AAV serotype 2 (AAV2) and its heparan sulfate (HS)-binding-deficient capsid led to similar expression, indicating transduction of the outer retina occurred by HS-independent mechanisms. However, intravitreal delivery of HS-ablated recombinant AAV2 (rAAV2) led to a 300-fold decrease in transduction compared to AAV2. Fluorescence in situ hybridization of AAV transgenes was used to identify differences in retinal trafficking and revealed that HS binding was responsible for AAV2 accumulation at the ILM. This mechanism was tested on human ex vivo retinas and showed similar accumulation with HS-binding AAV2 capsid only. To evaluate if HS binding could be applied to other AAV serotypes to enhance their transduction, AAV1 and AAV8 were modified to bind HS with a single-amino-acid mutation and tested in mice. Both HS-binding mutants of AAV1 and AAV8 had higher intravitreal transduction than their non-HS-binding parent capsid due to increased retinal accumulation. To understand the influence that HS binding has on tropism, chimeric AAV2 capsids with dual-glycan usage were tested intravitreally in mice. Compared to HS binding alone, these chimeric capsids displayed enhanced transduction that was correlated with a change in tropism. Taken together, these data indicate that HS binding serves to sequester AAV capsids from the vitreous to the ILM but does not influence retinal tropism. The enhanced retinal transduction of HS-binding capsids provides a rational design strategy for engineering capsids for intravitreal delivery. IMPORTANCE Adeno-associated virus (AAV) has become the vector of choice for viral gene transfer and has shown great promise in clinical trials. The need for development of an easy, less invasive injection route for ocular gene therapy is met by intravitreal delivery, but delivery of AAV by this route results in poor transduction outcomes. The inner limiting membrane (ILM) creates a barrier separating the vitreous and the retina. Binding of AAV to heparan sulfate proteoglycan (HSPG) at the ILM may allow the virus to traverse this barrier for better retinal transduction. We show that HSPG binding is correlated with greater accumulation and penetration of AAV in the retina. We demonstrated that this accumulation is conserved across mouse and human retinas and that the addition of HSPG binding to other AAV capsids can increase the number of vectors accumulating at the ILM without dictating tropism.
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