Cysteine-Modified AAV Capsids for Targeted Thioether Coupling
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Solution Overview
Problem
Adeno-associated virus (AAV) vectors face challenges with broad tropism, leading to reduced transduction efficacy and safety concerns due to non-specific targeting, accumulation in the liver, and low efficiency for certain cell types, necessitating improved cell-specific targeting and increased therapeutic delivery capacity.
Innovation Solution
Introduce cysteine residues on the outer surface of AAV capsid proteins through mutation, enabling covalent modification via thioether binding for chemical coupling of ligands, nanoparticles, or drugs, allowing targeted cell entry and increased coding capacity through dual vector systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If AAV vectors are used for gene delivery, then transduction of both dividing and non-dividing cells is achieved, but broad tropism causes reduced transduction efficacy and safety concerns due to non-specific targeting
Solution Approach 1:
The patent applies local quality by introducing cysteine residues at specific localized positions on the AAV capsid surface (positions 446, 458, 459, 525, or 551) to enable targeted chemical modification. This localized modification approach allows specific cell targeting while preserving the overall capsid structure and function, resolving the contradiction between broad tropism and non-specific targeting.
Solution Approach 2:
The patent changes the chemical parameters of the capsid surface by substituting specific amino acids with cysteine residues, which introduce thiol groups capable of covalent bonding. This parameter change enables the attachment of targeting ligands, transforming the non-specific AAV vector into a specifically targeted delivery system while maintaining its ability to transduce both dividing and non-dividing cells.
2Adaptability or versatility
If AAV vectors are administered systemically, then wide distribution is achieved, but accumulation in the liver limits sufficient transduction of other target tissues
Solution Approach 1:
The patent uses targeting ligands as intermediaries between the AAV vector and specific cell surface receptors. By covalently attaching ligands such as antibodies, peptides, or small molecules that specifically bind to receptors on target cells, the vector is directed away from non-target tissues like the liver and toward the intended target, enabling selective tissue transduction while maintaining systemic administration capabilities.
3Adaptability or versatility
If cysteine residues are introduced on the capsid surface, then chemical modification capability is enhanced, but structural stability of the capsid may be compromised
Solution Approach 1:
The patent performs preliminary action by introducing cysteine residues into the capsid protein sequence before capsid assembly occurs. This allows the cysteine-containing capsid proteins to self-assemble into stable capsid structures with the modified amino acids already in place, ensuring that the structural stability is established during assembly rather than being compromised by post-assembly modification.
Solution Approach 2:
The patent applies local quality by selecting specific positions (446, 458, 459, 525, or 551) on the capsid surface for cysteine substitution, ensuring that modifications occur at locations that do not disrupt critical structural elements. This localized approach maintains overall capsid stability while providing sufficient surface exposure for chemical modification capability.
4Quantity of substance
If multiple ligands or nanoparticles are coupled to AAV vectors, then coding capacity and therapeutic delivery are increased, but device complexity increases
Solution Approach 1:
The patent applies universality by creating a multi-functional AAV vector platform where the same cysteine-modified capsid can be used to attach various types of ligands (antibodies, peptides, small molecules) and nanoparticles. This universal modification approach allows a single vector design to serve multiple therapeutic purposes, increasing coding capacity and delivery versatility without proportionally increasing complexity for each specific application.
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
Enhances cell-specific targeting, improves transduction efficiency, and increases the coding capacity of AAV vectors, overcoming limitations of broad tropism and liver accumulation, while maintaining infectivity and safety.
Implementation Method 1
enabling covalent modification via thioether binding for chemical coupling of ligands, nanoparticles, or drugs
Data Source
Figure 1~2
Figure 3~5
AI summary
In a first aspect, the present invention relates to a mutated adeno-associated virus (AAV) capsid protein or fragment thereof wherein a substitution of a wild type non-cysteine amino acid into a cysteine is present whereby the wild type non-cysteine amino acid is exposed on the outer surface of the capsid of an AAV particle. In a further aspect, a mutated AAV particle comprising the AAV capsid protein or fragment thereof according to the present invention is provided. In addition, a nucleic acid encoding the AAV capsid protein according to the present invention is identified together with a corresponding nucleic acid vector, in particular, a plasmid or a gene string. In addition, a host cell containing the nucleic acid vector or the nucleic acid according to the present invention as well as a composition comprising at least an infectious (transducing) AAV particle containing a mutated AAV capsid protein as defined herein together with a non-infectious AAV particle containing a mutated AAV capsid protein as e.g. defined herein is disclosed. Further, a method for the modification of a mutated AAV particle is disclosed allowing a specific modification of the same including an embodiment using a reagent addressing the cysteine residues for binding reaction such as a thioether binding.