Recombinant AAV Library Production via Capsid Segmentation
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Solution Overview
Problem
Existing AAV production methods face challenges in achieving specific cell tropism and avoiding non-specific infection, particularly in cells that are difficult to transduce or require more targeted gene delivery.
Innovation Solution
A process is developed to produce a library of recombinant AAV particles with diverse capsid polypeptides, where the first AAV particles are encapsidated by common capsid polypeptides and then used to infect second host cells, allowing the expression of different capsid polypeptides encoded within their genomes, thereby creating a phenotype-to-genotype link.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If AAV particles are produced with diverse capsid polypeptides to achieve specific cell tropism, then the specificity of gene delivery is improved, but the complexity of the production process increases
Solution Approach 1:
The production process is divided into two distinct phases: first, producing AAV particles with common capsid polypeptides that can infect a broad range of cells; second, allowing expression of diverse capsid polypeptides within the infected cells to generate particles with specific tropism. This segmentation resolves the contradiction by separating the infection function from the specific tropism function.
Solution Approach 2:
The patent performs preliminary action by first infecting host cells with AAV particles containing diverse cap gene sequences but encapsidated with common capsid polypeptides. This preliminary infection step enables subsequent expression of the diverse capsid polypeptides within the infected cells, achieving specific tropism without directly producing diverse capsid particles in the initial production step.
2Ease of manufacture
If AAV particles use common capsid polypeptides for infection, then the ease of production is improved, but the adaptability to different target cells deteriorates
Solution Approach 1:
The patent uses an intermediary mechanism where AAV particles with common capsid polypeptides serve as vectors to deliver diverse cap gene sequences into host cells. These common capsid particles act as intermediaries that facilitate initial infection, after which the delivered cap genes express diverse capsid polypeptides to achieve adaptability to different target cells.
Solution Approach 2:
The system transitions from a static state where particles have fixed capsid polypeptides to a dynamic state where particles can change their capsid type. Initially, particles use common capsid polypeptides for easy production and broad infection, then dynamically switch to diverse capsid polypeptides expressed from the delivered genomes to achieve specific tropism for different target cells.
3Productivity
If AAV particles are designed to infect a broad range of cells, then the productivity of gene delivery is improved, but the harmful non-specific infection increases
Solution Approach 1:
The patent applies local quality by giving different parts of the gene delivery system different functions: the outer capsid polypeptide provides broad infection capability for high productivity, while the inner delivered cap gene sequence provides localized specific tropism. This spatial and functional differentiation allows the particle to first achieve broad infection then switch to specific targeting, reducing non-specific infection.
Data Source
AI summary
The present invention relates to a process for producing a library of recombinant adeno-associated virus (AAV) particles which are encapsidated by a variety of different capsid polypeptides. Each recombinant AAV particle in the library comprises an AAV genome which comprises AAV ITRs flanking a first AAV cap gene encoding a first Cap polypeptide, wherein the particles in the library differ in the nucleotide sequences of their first AAV cap genes, and wherein each particle in the library is encapsidated by a Cap polypeptide which is encoded by the cap gene within its AAV genome. The library may be used to screen for recombinant AAV particles which have high specificity for cells of a target therapeutic tissue.