Hybrid Phagemid Vector for rAAV Production Yield
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Solution Overview
Problem
Current methods for commercial-scale production of recombinant adeno-associated virus (rAAV) face challenges such as low yields, high costs, and the use of infectious eukaryotic viruses, which pose safety concerns and contamination risks.
Innovation Solution
The development of a hybrid phagemid viral vector system, referred to as Phagemid/Adeno-associated Virion (PAAV), which lacks at least 50% of its bacteriophage genome, allowing for the use of a helper virus to facilitate vector assembly and enabling efficient commercial-scale production of rAAV.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If transfection-based protocols are used for rAAV production, then high purity is achieved, but productivity is low and costs are high
Solution Approach 1:
The production system is segmented into three separate plasmids: pAAV (containing ITR-flanked genome), pRep (containing rep genes), and pCap (containing cap genes). This segmentation allows each component to be optimized independently while enabling high-yield production through co-transfection, resolving the contradiction between purity and productivity.
Solution Approach 2:
The rep and cap genes are pre-packaged into separate plasmids that are co-transfected with the AAV genome plasmid. This preliminary preparation of all necessary components enables efficient viral particle assembly and high-yield production while maintaining purity through controlled in vitro transfection.
2Productivity
If eukaryotic viruses are used to supply helper functions, then productivity is improved, but safety concerns and contamination risks increase
Solution Approach 1:
The helper functions (rep and cap genes) are extracted from eukaryotic viruses and placed into separate bacterial plasmids (pRep and pCap). This extraction eliminates the safety concerns associated with infectious eukaryotic viruses while maintaining their productive helper functions, allowing high-yield production without contamination risks.
Solution Approach 2:
Bacterial plasmids serve as intermediaries to deliver the rep and cap genes to the producer cells. These plasmids act as safe carriers that provide the necessary helper functions without introducing the pathogenicity or safety concerns of live eukaryotic viruses, resolving the contradiction between productivity and safety.
3Stability of the object's composition
If the complete bacteriophage genome is used in phagemid particles, then structural integrity is maintained, but genome size increases reducing transgene capacity
Solution Approach 1:
The phagemid particle genome is designed to lack at least 50% of the complete bacteriophage genome. Only the essential elements (origin of replication, packaging signal, and coat protein genes) are retained, while non-essential regions are removed. This extraction reduces genome size and increases transgene capacity while maintaining the structural integrity needed for particle formation and stability.
Solution Approach 2:
The bacteriophage genome is segmented into essential and non-essential portions. The essential segments (origin of replication, packaging signal, coat protein genes) are retained in the phagemid, while non-essential segments are removed. This segmentation allows the particle to maintain structural integrity for stability while creating sufficient capacity for large transgenes.
Data Source
AI summary
The invention provides hybrid and recombinant phagemid vectors for expressing a transgene in a target cell transduced with the vector. A recombinant phagemid particle comprises at least one transgene expression cassette which encodes an agent which exerts a biological effect on the target cell, characterised in that the phagemid particle comprises a genome which lacks at least 50% of its bacteriophage genome. The invention extends to the use of such phagemid expression systems as a research tool, and for the delivery of transgenes in a variety of gene therapy applications, DNA and/or peptide vaccine delivery and imaging techniques. The invention extends to in vitro, in vivo or in situ methods for producing viral vectors, such as recombinant adeno-associated viruses (rAAV) or lentivirus vectors (rLV), and to genetic constructs used in such methods.