AAV9 Capsid Mutants for Tissue-Specific Gene Delivery
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Solution Overview
Problem
Current AAV vectors, particularly AAV2, face challenges in transduction efficiency and immunological issues due to pre-existing neutralizing antibodies and poor receptor recognition, limiting their effectiveness for gene therapy applications.
Innovation Solution
Modifying the availability of the AAV9 receptor on target cells by using neuraminidase to expose terminal β-galactose residues, allowing for enhanced binding and uptake of AAV9 vectors, and engineering mutant AAV9 capsids to alter tropism and reduce airway epithelium transduction while maintaining liver and heart transduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If AAV2 vectors are used for gene delivery, then broad somatic cell transduction is achieved, but transduction efficiency is poor and immunological problems occur
Solution Approach 1:
The patent applies parameter changes by modifying the capsid protein parameters of AAV vectors. Specifically, it combines the capsid from AAV9 (which has high transduction efficiency and low immunogenicity) with the ITRs and transgene from AAV2, creating a hybrid vector that inherits the beneficial properties of both serotypes. This parameter change in capsid composition resolves the contradiction between broad transduction capability and transduction efficiency.
2Adaptability or versatility
If AAV2 vectors are used, then gene delivery to somatic cells is possible, but pre-existing neutralizing antibodies and T cell activation occur
Solution Approach 1:
The patent changes the immunological parameters by replacing the AAV2 capsid with an AAV9 capsid in the hybrid vector construction. The AAV9 capsid has demonstrated lower pre-existing neutralizing antibody titers and reduced T cell activation compared to AAV2, while maintaining gene delivery capability. This parameter change in capsid identity directly addresses the immunological problems associated with AAV2.
3Productivity
If AAV9 vectors are used to transduce airway epithelium, then efficient transduction is achieved, but off-target transduction in non-desired tissues occurs
Solution Approach 1:
The patent applies local quality by creating mutant AAV9 capsids with specific amino acid substitutions that locally modify the capsid surface properties. The mutations at positions 271, 446, and 470 (and other combinations) create localized changes in the capsid that selectively reduce binding affinity for airway epithelium receptors while preserving binding capability in liver and heart tissues. This localized modification of capsid properties achieves tissue-specific transduction patterns.
Solution Approach 2:
The patent changes the physical-chemical parameters of the AAV9 capsid through site-directed mutagenesis. By substituting specific amino acids (e.g., Asp271Ala, Tyr446Ala, Asn470Ala), the patent modifies the electrostatic and hydrophobic properties of the capsid surface, thereby altering tissue tropism. These parameter changes in capsid composition enable selective reduction of airway epithelium transduction while maintaining transduction in other tissues.
4Productivity
If wild-type AAV9 capsid is used, then broad tissue transduction is achieved, but inability to control tissue distribution occurs
Solution Approach 1:
The patent applies local quality by introducing specific point mutations at defined positions in the AAV9 capsid sequence. These localized amino acid substitutions (at positions 271, 446, 470, and others) create distinct binding profiles for different tissue types, enabling precise control over vector distribution. The local modification approach allows independent optimization of transduction efficiency and tissue specificity.
Solution Approach 2:
The patent applies dynamics by creating a library of AAV9 mutant capsids with varying degrees and patterns of amino acid substitutions. This generates a dynamic system where the tissue tropism can be tuned by selecting appropriate mutant variants. The dynamic approach allows optimization of vector properties for specific therapeutic indications while maintaining high transduction efficiency.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Improves the efficiency and safety of AAV9-mediated gene delivery by increasing cellular uptake and allowing for targeted transduction, reducing immunological responses and optimizing vector distribution within the body.
Implementation Method 1
Modifying the availability of the AAV9 receptor on target cells by using neuraminidase to expose terminal β-galactose residues
Data Source
AI summary
A method of altering the targeting and/or cellular uptake efficiency of an adeno-associated virus (AAV) viral vector having a capsid containing an AAV9 cell surface binding domain is described. The method involves modifying a clade F cell surface receptor which comprises a glycan having a terminal sialic acid residue and a penultimate β-galactose residue. The modification may involve retargeting the vector by temporarily functionally ablate AAV9 binding in a subset of cells, thereby redirecting the vector to another subset of cells. Alternatively, the modification may involve increasing cellular update efficiency by treating the cells with a neuraminidase to expose cell surface β-galactose. Also provided are compositions containing the AAV9 vector and a neuraminidase. Also provided is a method for purifying AAV9 using β-galactose linked to solid support. Also provided are mutant vectors which have been modified to alter their targeting specificity, including mutant AAV9 in which the galactose binding domain is mutated and AAV in which an AAV9 galactose binding domain is engineered.