Mutated AAV Capsid Proteins for Retinal Gene Delivery
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Solution Overview
Problem
Current gene delivery methods for treating eye disorders, such as photoreceptor diseases and retinal degeneration, face challenges in achieving high transduction efficiency and specificity, particularly in retinal bipolar cells, due to issues like ubiquitin-mediated protein degradation and limited tissue tropism of adeno-associated virus (AAV) vectors.
Innovation Solution
The use of recombinant AAV vectors with mutated capsid proteins, specifically tyrosine-to-phenylalanine mutations, to enhance transduction efficiency and evade ubiquitin-mediated degradation, combined with light-sensitive proteins like ChR2 linked to metabotropic glutamate receptor 6 (mGluR6) regulatory sequences, for targeted expression in retinal bipolar cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wild-type AAV vectors are used for gene delivery to retinal bipolar cells, then the vectors can maintain natural capsid structure and biological function, but transduction efficiency is limited due to ubiquitin-mediated degradation and restricted tissue tropism
Solution Approach 1:
The patent applies parameter changes by mutating specific tyrosine residues (Y252, Y272, Y444, Y500, Y730) to phenylalanine in the AAV capsid protein sequence. This amino acid substitution changes the chemical properties of the capsid surface, preventing ubiquitin-mediated degradation while maintaining capsid stability and transduction function. The Y→F mutation removes the hydroxyl group from tyrosine, eliminating the ubiquitination site while preserving the aromatic ring structure for structural integrity.
Solution Approach 2:
The patent extracts and removes the harmful ubiquitin-mediated degradation pathway by eliminating the tyrosine residues that serve as ubiquitination sites. By taking out these specific amino acid positions and replacing them with phenylalanine, the patent selectively removes the degradation mechanism while preserving the essential transduction function of the AAV vector.
2Reliability
If wild-type AAV vectors are used for gene delivery, then the vectors maintain natural biological properties, but tissue tropism is limited and cannot efficiently target retinal bipolar cells
Solution Approach 1:
The patent changes the biological parameter of tissue tropism by mutating tyrosine residues to phenylalanine in the capsid protein. This parameter change alters the surface properties of the AAV vector, enabling it to specifically target retinal bipolar cells while maintaining other essential biological functions. The mutation modifies cell surface receptor interactions to achieve enhanced tropism for bipolar cells.
Solution Approach 2:
The patent applies local quality changes by modifying specific regions of the capsid protein (positions 252, 272, 444, 500, 730) while leaving the rest of the capsid structure intact. These localized mutations at specific tyrosine residues confer enhanced targeting ability to retinal bipolar cells without compromising the overall capsid function and stability.
3Productivity
If multiple tyrosine residues are mutated to phenylalanine in the capsid protein, then transduction efficiency and tissue tropism are improved, but the capsid protein structure may be altered
Solution Approach 1:
The patent carefully selects which tyrosine residues to mutate (Y252, Y272, Y444, Y500, Y730) based on their surface exposure and functional importance. By changing only these specific parameters (amino acid positions) and not the entire capsid structure, the patent achieves improved transduction efficiency while maintaining overall capsid stability and biological function.
Solution Approach 2:
The patent applies local quality changes by mutating only specific tyrosine residues that are surface-exposed and involved in cellular interactions, while preserving the core capsid structure. The mutations are localized to positions 252, 272, 444, 500, and 730, which allows improved targeting and transduction without compromising the structural integrity of the entire capsid protein.
Data Source
AI summary
Disclosed are capsid-mutated rAAV vectors and methods for their use in gene therapy, and particularly for use in delivering therapeutic transgenes to treat a variety of mammalian diseases and disorders, including dysfunctions and abnormal conditions of the human eye. VP3 capsid proteins comprising a modification of one or more of the surface-exposed tyrosine residues are disclosed, and in particular, VP3 capsid protein comprising tyrosine-to-phenylalanine mutations at positions corresponding to Y444F, Y500F, and Y730F of the wild-type AAV2 sequence. Also provided are rAAV virions and viral particles that comprise such a mutated AAV capsid protein and a nucleic acid molecule that expresses one or more selected therapeutic or reporter transgenes in one or more mammalian cells of interest. Advantageously, the capsid-mutated rAAV vectors and virions disclosed herein afford improved transduction efficiency in a variety of cells, tissues and organs of interest, when compared to their unmodified (i.e., wild-type) rAAV vector counterparts.