Microbial Glycogen Debranching Enzymes for AAV-Limited GSD III Therapy
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Solution Overview
Problem
Current gene therapy approaches for glycogen storage disease type III (GSD III) are limited by the small carrying capacity of AAV vectors and the elicitation of immune responses against transgene products, which hinder effective treatment of multiple tissues.
Innovation Solution
The use of microbial polypeptides, such as bacterial glycogen debranching enzymes, encoded by codon-optimized nucleic acid sequences, delivered via AAV vectors with tissue-specific or immunotolerant dual promoters to prevent immune responses and overcome vector capacity limitations, combined with additional therapeutic strategies like RNAi and immune modulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If AAV vectors are used to deliver human GDE gene, then gene therapy can be provided, but the small carrying capacity of AAV vectors limits effective treatment
Solution Approach 1:
The patent changes the key parameter from using human GDE gene to using microbial GDE gene. The microbial GDE gene has a smaller coding sequence that fits within the AAV carrying capacity while maintaining the essential debranching enzyme activity needed to treat GSD III, thereby resolving the contradiction between vector capacity and therapeutic effectiveness.
Solution Approach 2:
The patent uses a microbial version of the GDE enzyme instead of the human version. This microbial copy performs the same therapeutic function (glycogen debranching) but with a more compact gene sequence that can be accommodated within the AAV vector's limited carrying capacity.
2Quantity of substance
If bacterial glycogen debranching enzyme is used, then vector capacity limitation is overcome, but immune responses against transgene products are elicited
Solution Approach 1:
The patent applies tissue-specific promoters to drive expression of the microbial GDE gene only in target tissues (liver, muscle) rather than systemically. This localized expression strategy reduces the overall immune burden while maintaining therapeutic effectiveness in the tissues that need treatment.
Solution Approach 2:
The patent uses codon-optimized versions of the microbial GDE gene that are optimized for mammalian expression. This codon optimization acts as an intermediary that allows the bacterial enzyme to be expressed efficiently in human cells while potentially reducing immune recognition, bridging the gap between microbial origin and human application.
3Object-affected harmful factors
If human GDE gene is used, then immune tolerance may be maintained, but the large gene size exceeds AAV carrying capacity
Solution Approach 1:
The patent fundamentally changes the source of the GDE gene from human to microbial origin. This parameter change reduces the gene size to fit AAV capacity while implementing additional strategies (codon optimization, tissue-specific promoters) to manage the immune response consequence of using non-human sequences.
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
This approach effectively corrects glycogen accumulation in multiple tissues, improves liver and muscle function, and reduces immune response, providing long-term therapeutic efficacy for GSD III.
Implementation Method 1
GDE in bacteria and other microorganisms has only a single α-1,6-glycosidic bond hydrolyzing activity for glycogen and amylopectin
Implementation Method 2
administering a vector containing a coding sequence codon optimized for expressing a therapeutic microbial GDE in human cells
Implementation Method 3
nucleic acid sequences encoding microbial polypeptides for degrading glycogen... codon-optimized for expression in a mammalian cell
Data Source
AI summary
This disclosure provides isolated nucleic acid molecules comprising nucleic acid sequences encoding microbial polypeptides that are codon optimized for expression in mammalian cells, vectors comprising an immunotolerant dual promoter system, and methods using these polynucleotides and polypeptides to treat glycogen storage diseases and other inherited diseases.