AAV Vector Production via Modified Rep Promoters
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Solution Overview
Problem
Current methods for producing recombinant AAV vectors face challenges such as the toxicity of AAV Rep proteins to adenovirus replication, low yields, and instability of adenoviruses encoding AAV Rep polypeptides, which hinder efficient production and purification of adenoviral vectors.
Innovation Solution
The approach involves modifying AAV rep gene promoters p5, p19, and p40 to reduce Rep protein expression and integrating the AAV Rep-coding sequence into an adenoviral vector without a functional adenovirus inhibitor sequence, allowing for stable encoding and low-level expression of Rep proteins, and using two adenoviral vectors to encode Rep and Cap sequences independently to reduce toxicity and enhance production yields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If AAV Rep genes are integrated into adenoviral vectors for production, then AAV production yields increase, but adenovirus replication is inhibited due to toxicity of Rep proteins
Solution Approach 1:
The AAV Rep gene is divided into two separate adenoviral vectors: one vector contains the Rep-coding sequence under modified promoters (p5, p19, p40), and the other vector contains the adenovirus inhibitor sequence (AIS) that has been mutated to reduce its activity. This segmentation allows controlled expression of Rep proteins while minimizing inhibition of adenovirus replication, resolving the contradiction between high AAV production and stable adenovirus replication.
Solution Approach 2:
The promoters (p5, p19, p40) controlling Rep gene expression are modified to alter their activity levels. By changing the promoter parameters, the system achieves optimized Rep protein expression that is sufficient for AAV production but reduced enough to avoid complete inhibition of adenovirus replication, thus balancing productivity and reliability.
2Productivity
If AAV Rep proteins are expressed at high levels to ensure sufficient replication functions, then AAV vector production efficiency increases, but toxicity to adenovirus replication increases
Solution Approach 1:
The modified promoters act as intermediaries between the Rep gene and the adenovirus replication machinery. By using altered promoter sequences that provide intermediate levels of gene expression, the system achieves sufficient Rep protein production for efficient AAV vector generation while preventing excessive toxicity that would completely halt adenovirus replication.
3Reliability
If adenovirus inhibitor sequence is present in the AAV Rep-coding vector, then Rep protein expression is controlled, but adenovirus replication is strongly inhibited
Solution Approach 1:
The adenovirus inhibitor sequence (AIS) is extracted from its native context and placed in a separate adenoviral vector from the Rep-coding sequence. Additionally, the AIS is mutated to reduce its inhibitory activity. This extraction and modification allow controlled expression of Rep proteins without strong inhibition of adenovirus replication, maintaining both reliability and productivity.
Data Source
AI summary
The invention relates to a nucleic acid molecule encoding at least one AAV Rep polypeptide, wherein one or more of the AAV (p5), (p19) and (p40) promoters have been modified to reduce or eliminate expression of one or more of the Rep polypeptides, or the nucleic acid molecule does not encode functional (Rep52) or (Rep40) polypeptides, or the nucleic acid molecule does not encode a functional adenovirus inhibitor sequence. The invention also relates to a process for producing recombinant AAV vectors through the use of a 2-adenovirus system, wherein all of the genes required for AAV replication and packaging (i.e. an AAV rep sequence of the invention, AAV cap and the AAV transfer vector comprising a transgene) may be encoded within two adenoviruses.