Engineered PFV Integrase Targeted Integration
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Solution Overview
Problem
Current gene therapy approaches using retroviruses face challenges in achieving targeted and stable integration of exogenous nucleic acids into specific sites in the host genome, often leading to integration-associated side effects such as cancer, due to the multimeric structure of retroviral integrases and host protein-directed integration preferences.
Innovation Solution
Development of an engineered retroviral integration complex comprising a prototype foamy virus (PFV) integrase with modified protomers and nucleic acid binding domains, such as zinc finger or TALE domains, to enable precise targeting and integration of cargo nucleic acids into specific genomic locations, avoiding oncogenic integration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If retroviral integrase is directed to integrate at a genomic locus by host co-factor (e.g., LEDGF/p75), then integration is facilitated, but it will always be impossible to subvert the influence of LEDGF/p75 for targeted integration
Solution Approach 1:
The patent uses an intermediary protein (e.g., zinc finger protein, TALE, or CRISPR/Cas9 complex) that binds to a specific DNA sequence as a mediator between the integrase and the target genome. This intermediary directs the integrase to a predetermined integration site, overcoming the inability to subvert host co-factors like LEDGF/p75. The intermediary protein serves as a customizable guide that enables precise targeting without requiring manipulation of the integrase's natural host factors.
Solution Approach 2:
The patent segments the integration system into separate functional components: the integrase enzyme (which performs the integration function) and the intermediary targeting protein (which provides specificity). This segmentation allows independent optimization of each component - the integrase can be engineered for catalytic activity while the intermediary protein provides customizable targeting, resolving the contradiction between facilitating integration and achieving precise targeting.
2Reliability
If retroviral integrase forms multimeric complexes (octamers, dodecamers, hexadecamers), then functional integration is achieved, but the complex structure prevents fusion of targeting protein domains to integrase
Solution Approach 1:
Instead of fusing the targeting domain directly to the integrase (which is blocked by multimerization), the patent introduces an intermediary protein that binds to the integrase complex and provides the targeting function. This intermediary approach bypasses the structural barrier created by integrase multimerization, allowing targeting protein domains to function without direct fusion to the integrase structure.
Solution Approach 2:
The patent extracts the targeting function from the integrase complex and assigns it to a separate intermediary protein. This extraction allows the integrase to form its necessary multimeric complex for functional integration while the targeting specificity is provided by the independent intermediary protein, avoiding the structural conflict between multimerization and domain fusion.
3Reliability
If MLV vectors deliver wild type gene to treat SCID, then gene therapy cure is achieved, but integration in promoter of oncogenes results in leukemia
Solution Approach 1:
The patent applies local quality by directing integration to a specific local site in the genome (e.g., a safe harbor locus like AMEG1 or a specific intron) rather than allowing random integration. The intermediary protein binds to a specific DNA sequence at the desired location, ensuring that the wild type gene is inserted at a predetermined safe site that does not disrupt oncogenes, thus maintaining therapeutic efficacy while eliminating oncogenic risk.
Solution Approach 2:
The patent performs preliminary action by pre-determining and pre-positioning the integration site before gene delivery. The intermediary protein is designed to bind to a specific target sequence in advance, ensuring that integration occurs at a safe harbor locus that is known not to contain oncogenes. This preliminary targeting prevents oncogenic integration before it can occur, rather than relying on post-integration screening or selection.
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
The engineered PFV integration complex allows for stable and targeted integration of therapeutic genes, reducing the risk of oncogenic side effects and improving the efficacy of gene therapy by precisely delivering wild-type genes to treat genetic disorders like cystic fibrosis.
Implementation Method 1
an engineered retroviral integration complex comprising an engineered prototype foamy virus (PFV) integrase (IN)... allows for stable and targeted integration of therapeutic genes
Data Source
AI summary
Disclosed herein are methods and compositions related to modified prototype foamy virus (PFV) and its uses to treat diseases and disorders. Also disclosed are methods of making said PFVs.