Adenoviral Helper Vectors With Conditional Packaging Control
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Solution Overview
Problem
Current gene therapy methods for modifying hematopoietic stem cells (HSCs) are limited by vectors with low payload capacity or high prevalence of neutralizing antibodies, such as lentiviral and adenoviral serotype 5 (Ad5) vectors.
Innovation Solution
Development of adenoviral helper genomes and vectors, including Ad3, Ad7, Ad11, Ad14, Ad16, Ad21, and Ad50 serotypes, with conditionally defective packaging sequences and inverted packaging sequences to reduce recombinase site-excising homologous recombination, allowing for efficient production of helper-dependent adenoviral donor vectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If adenoviral serotype 5 (Ad5) vectors are used for gene therapy, then payload capacity is improved, but prevalence of neutralizing antibodies increases
Solution Approach 1:
The patent extracts the packaging sequence from the adenoviral genome and places it under the control of a conditional promoter system. This allows the packaging sequence to be present and functional during vector production, but inactive during therapeutic administration, thereby eliminating the harmful effect of pre-existing antibodies while maintaining the benefit of high payload capacity
Solution Approach 2:
The patent changes the expression state of the packaging sequence from constitutive to conditional. By using a conditional promoter that can be activated or deactivated, the packaging sequence is only expressed when needed for vector production, not during therapy. This parameter change resolves the contradiction between maintaining packaging functionality and avoiding antibody recognition
2Ease of operation
If helper genome is packaged into adenoviral donor vectors, then viral proteins are provided in trans, but propagation in recipients occurs
Solution Approach 1:
The patent performs preliminary action by conditionally disabling the packaging sequence in the helper genome before vector production. The conditional promoter system is designed in advance to prevent packaging of the helper genome into donor vectors, thereby eliminating the risk of propagation in recipients while still allowing viral proteins to be provided in trans during production
Solution Approach 2:
The conditional promoter acts as an intermediary element that controls the expression of the packaging sequence. It mediates between the need for viral protein provision and the need to prevent propagation, allowing selective expression based on production conditions
3Reliability
If packaging sequence is made conditionally defective, then propagation is reduced, but production efficiency decreases
Solution Approach 1:
The patent introduces dynamics into the packaging sequence expression by using a conditional promoter that can switch between active and inactive states. During vector production, the promoter is activated to ensure efficient packaging and high productivity. During therapeutic administration, the promoter is inactive to prevent propagation and ensure safety. This dynamic control resolves the contradiction between propagation deficiency and production efficiency
Data Source
AI summary
The present disclosure provides, among other things, helper genomes and vectors useful in gene therapy, e.g., for production of helper-dependent donor vectors. Helper genomes of the present disclosure include a conditionally defective packaging sequence.