AAV Capsid Amino Acid Tuning for Liver Tropism Control
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Solution Overview
Problem
Existing AAV serotypes exhibit liver tropism that may be undesirable for certain therapeutic applications, necessitating the need to understand and manipulate tissue tropism for improved gene therapy efficacy.
Innovation Solution
Altering the amino acid residues at specific positions in the AAV capsid protein, such as 266 and 168, to enhance or reduce liver tropism, achieved through site-directed mutagenesis, restriction digest, and ligation, or using heterologous or de novo synthesized liver toggle regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If AAV vectors with natural liver tropism are used, then liver transduction efficiency is high, but off-target effects and toxicity increase
Solution Approach 1:
The patent applies local quality by making specific amino acid substitutions at defined positions (266 and 168) within the AAV capsid protein sequence. These localized changes at specific residues modify the capsid's interaction with liver cell receptors, thereby selectively enhancing or reducing liver tropism without altering the entire capsid structure, resolving the contradiction between transduction efficiency and off-target effects.
Solution Approach 2:
The patent employs parameter changes by systematically varying amino acid residues at positions 266 and 168 of the AAV capsid protein. By changing these specific parameters (amino acid identity) in the capsid sequence, the invention modulates liver tropism to achieve optimal transduction efficiency while minimizing off-target effects and toxicity.
2Measurement precision
If AAV capsid amino acids are modified to alter liver tropism, then delivery precision to liver cells is improved, but vector production complexity increases
Solution Approach 1:
The patent reduces production complexity by applying local quality changes - modifying only specific amino acid positions (266 and 168) rather than the entire capsid sequence. This localized approach simplifies vector production compared to comprehensive capsid redesign, as it requires targeted mutagenesis at defined sites while maintaining the overall capsid structure and production workflow.
Solution Approach 2:
The patent manages production complexity through controlled parameter changes - systematically varying amino acid identity at positions 266 and 168. This focused parameter modification approach enables precise control of liver tropism while maintaining relatively simple production protocols, avoiding the complexity of comprehensive capsid redesign or chimeric construction.
3Reliability
If higher doses of AAV are administered to overcome liver tropism, then non-liver tissue transduction improves, but systemic toxicity increases
Solution Approach 1:
The patent applies inversion by reversing the conventional approach - instead of increasing dose to overcome liver tropism and achieve non-liver transduction (which causes toxicity), the invention modifies the capsid to actively reduce liver tropism. This inverted strategy enables non-liver tissue transduction at lower doses, thereby avoiding systemic toxicity while achieving the desired therapeutic effect in target tissues.
Solution Approach 2:
The patent resolves the dose-toxicity contradiction through parameter changes in the capsid amino acid sequence at positions 266 and 168. These modifications alter the virus's tissue selectivity parameters, enabling effective non-liver transduction at reduced doses and thereby eliminating the need for high-dose administration that causes systemic toxicity.
Data Source
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AI summary
This disclosure provides compositions and methods for altering or changing the tissue tropism, e.g., liver tropism, of adeno-associated viruses (AAV).