Mini-PCDH15 AAV Vector for PCDH15 Size-Limited Gene Delivery
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Solution Overview
Problem
Current AAV vectors are unable to efficiently deliver the large PCDH15 coding sequence for treating Usher 1F, which causes deafness and blindness, due to size limitations and inefficient expression in inner ear and eye cells.
Innovation Solution
Development of a mini-PCDH15 nucleic acid sequence that fits within a single AAV genome, comprising a truncated extracellular portion and a functional transmembrane and cytoplasmic domain, delivered using AAV vectors like AAV5, AAV7, AAV8, or AAV9, capable of targeting inner and outer hair cells and photoreceptor cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the full-length PCDH15 coding sequence is used for gene therapy, then the therapeutic effect is complete, but the sequence size (5.8 kb) exceeds the AAV capsid capacity (4.7 kb)
Solution Approach 1:
The patent extracts only the essential functional domains of the PCDH15 protein by deleting non-essential extracellular calcium-binding domains (EC1-EC6), retaining the transmembrane and cytoplasmic domains plus minimal extracellular regions (EC7-EC11). This creates a mini-PCDH15 construct that fits within AAV capsid capacity while maintaining core therapeutic function in hair cell tip links.
Solution Approach 2:
The full-length PCDH15 protein is segmented into functional domains, with the patent retaining only the necessary portions for tip link function. The extracellular domain is divided into calcium-binding domains (EC1-EC11), and the patent selectively includes only EC7-EC11 along with transmembrane and cytoplasmic regions, creating a functional fragment that fits viral vector constraints.
2Reliability
If conventional AAV vectors are used for gene delivery, then the vectors are safe and currently used in clinical trials, but they fail to achieve efficient expression in most types of cells in the inner ear and eye
Solution Approach 1:
The patent optimizes the AAV vector for specific local tissues (inner ear and eye) by selecting appropriate serotypes (AAV2, AAV5, AAV8, AAV9) with enhanced tropism for these regions. The vector is designed with tissue-specific promoters and regulatory elements that enhance expression efficiency in hair cells, photoreceptors, and retinal cells while maintaining safety profile.
Data Source
AI summary
Aspects of the disclosure relate to compositions, nucleic acids, vectors, viruses, and methods useful for treating hearing loss and/or blindness, for example, Usher Syndrome type IF. The present disclosure provides isolated nucleic acids, vectors, and rAAV.9.PHP.B comprising a transgene encoding a mini-PCDH15, and methods of treating hearing loss using the same. The present disclosure also provides a gRNA associated with a base editor to correct one or more mutations in PCDH15 for treating hearing loss and/or vision loss.