USH2A Minigene Delivery via rAAV Vectors
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Solution Overview
Problem
Current gene therapy approaches, such as those using Adeno-associated Viral (AAV) vectors, face challenges in effectively treating Usher Syndrome due to the large size of the USH2A gene, which limits successful delivery and treatment of the associated retinal degeneration and hearing loss.
Innovation Solution
Development of recombinant adeno-associated virus (rAAV) vectors encoding a USH2A minigene, specifically designed to target ocular cells, including photoreceptor cells and retinal pigmented epithelium, using tropic capsid proteins like AAV8 for efficient delivery and expression of the USH2A protein.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional AAV vector-mediated gene delivery is used to deliver the full USH2A gene, then complete USH2A gene function can be restored, but the large size of the USH2A gene (15.6 kb) exceeds the packaging capacity of conventional AAV vectors
Solution Approach 1:
The USH2A gene is divided into multiple exons, and only the critical coding exons (2-12) are selected to construct a minigene. This segmentation approach reduces the gene size from 15.6 kb to a manageable length that fits within AAV packaging capacity while preserving essential protein function.
Solution Approach 2:
Non-essential portions of the USH2A gene (intron sequences and non-coding regions) are extracted and removed, retaining only the critical coding exons. This extraction creates a streamlined minigene that maintains therapeutic function while reducing size constraints for AAV delivery.
2Length of moving object
If a minigene approach is used to reduce gene size for AAV delivery, then the gene can be successfully packaged and delivered, but the completeness and full functionality of the USH2A protein may be compromised
Solution Approach 1:
The minigene construction focuses on preserving the critical local quality of the USH2A protein by selectively including exons 2-12 that encode essential functional domains. This targeted approach ensures that the most important protein functions are maintained while non-essential regions are omitted.
Solution Approach 2:
Instead of delivering the complete USH2A gene, a partial version (minigene containing exons 2-12) is delivered. This partial action is sufficient to achieve therapeutic benefit by producing a functional protein fragment that can compensate for the defective endogenous gene without requiring the full-length gene.
3Productivity
If AAV vectors are engineered to carry the USH2A minigene, then gene delivery efficiency can be improved, but the complexity of vector design and manufacturing increases
Solution Approach 1:
The AAV vector parameters are optimized by adjusting the transgene size to match the AAV packaging capacity. The minigene design parameters (exon selection, promoter choice, ITR configuration) are carefully tuned to maximize delivery efficiency while maintaining compatibility with standard AAV production systems.
4Reliability
If the complete USH2A gene is attempted to be delivered, then full therapeutic effect can be achieved, but the treatment cost and manufacturing difficulty increase significantly
Solution Approach 1:
Instead of attempting to manufacture and deliver the complete 15.6 kb USH2A gene which would require complex, expensive manufacturing processes, a simplified minigene version is used. This disposable approach uses a reduced genetic construct that can be manufactured with standard AAV production protocols, significantly reducing manufacturing complexity and cost.
Data Source
AI summary
Aspects of the disclosure relate to compositions and methods useful for delivering minigenes to a subject. Accordingly, the disclosure is based, in part, on isolated nucleic acids and gene therapy vectors, such as viral (e.g., rAAV) vectors, comprising one or more gene fragments encoding a therapeutic gene product, such as a protein or peptide (e.g., a minigene). In some embodiments, the disclosure relates to gene therapy vectors encoding a USH2A protein (e.g., the gene product of USH2A gene) or a portion thereof. In some embodiments, compositions described by the disclosure are useful for treating diseases associated with mutations in the USH2A gene, for example Usher Syndrome.