Modified Muscle-Specific Promoters for Full-Genome AAV Packaging
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Solution Overview
Problem
Existing AAV vectors using the Spc5-12 promoter for muscle-specific gene expression often result in high yields of AAV vectors with partial genomes, necessitating complex purification processes and increased costs.
Innovation Solution
Modifying muscle-specific promoter sequences to reduce hairpin loop secondary structure, such as those in Spc5-12v1 and Spc5-12v2, enhances packaging efficiency of full-length AAV genomes, leading to improved production and recovery of fully packaged viral particles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the Spc5-12 promoter is used to drive muscle-specific gene expression in AAV vectors, then muscle-specific expression is achieved, but the yield of full genome AAV vectors decreases and partial genome vectors increase
Solution Approach 1:
The patent applies parameter changes by modifying the nucleotide sequence of the Spc5-12 promoter to alter its secondary structure properties. Specifically, the invention changes the sequence parameters to reduce hairpin loop formation while preserving the promoter's muscle-specific transcriptional activity, thereby resolving the contradiction between reliable muscle-specific expression and high productivity of full genome vectors
Solution Approach 2:
The patent converts the harmful effect of hairpin loop secondary structures (which cause packaging defects) into a beneficial design criterion. By intentionally designing promoter sequences that minimize hairpin formation while maintaining muscle-specific function, the invention transforms the problematic secondary structure issue into a guiding principle for creating optimized promoters that simultaneously achieve high muscle-specific expression and high full genome vector yield
2Reliability
If promoter sequences with high muscle-specific activity are used, then gene expression in muscle tissue is enhanced, but packaging efficiency of AAV genomes into capsids decreases
Solution Approach 1:
The patent modifies physical-chemical parameters of the promoter sequence, specifically the nucleotide composition and arrangement, to change the secondary structure propensity. The optimized promoters maintain the biochemical parameter of muscle-specific transcriptional activity while changing the structural parameter of hairpin loop formation, thereby improving packaging efficiency without sacrificing gene expression reliability
Solution Approach 2:
The patent applies preliminary action by pre-optimizing the promoter sequences before AAV genome construction and packaging. The modified promoters are designed in advance to have reduced hairpin loop secondary structures, preventing packaging efficiency issues before they occur during the virus production process, rather than attempting to correct them after vector assembly
Data Source
AI summary
Disclosed are nucleic acids comprising or consisting of the nucleic acid sequence of SEQ ID NO: 1 or SEQ ID NO:2, or variants thereof. Also disclosed are recombinant expression cassettes comprising a promoter comprising SEQ ID NO: 1 or SEQ ID NO:2, or variants thereof operably linked to a transgene, such as a Microdystrophin, and recombinant AAV constructs comprising these recombinant expression cassettes. Disclosed are methods of treating muscle-specific disease comprising administering a recombinant AAV construct comprising a promoter comprising SEQ ID NO: 1 or SEQ ID NO:2, or variants thereof operably linked to a transgene, such as a Microdystrophin.