Engineered Meganucleases for Specific HBV Genome Cleavage
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Solution Overview
Problem
Current anti-HBV drugs have limitations, such as severe adverse reactions and require long-term administration, and existing engineered meganucleases lack sufficient on-target specificity and cause off-target cutting in host cell genomes, hindering effective treatment of HBV infections and hepatocellular carcinoma.
Innovation Solution
Development of optimized engineered meganucleases with enhanced specificity for the HBV 11-12 recognition sequence, reducing off-target cutting and increasing indel formation, which disrupt viral protein expression through non-homologous end joining, or introduce a suicide gene via homologous recombination to degrade the HBV genome.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing engineered meganucleases are used to target HBV, then HBV replication is reduced, but off-target cutting occurs in host cell genomes
Solution Approach 1:
The patent applies local quality by optimizing specific regions of the meganuclease protein structure. Hypervariable regions (HVR1 and HVR2) are identified and mutated to improve DNA binding specificity at the HBV 11-12 recognition sequence while maintaining cleavage activity. This localized optimization at specific protein domains resolves the contradiction between achieving high on-target specificity and minimizing off-target effects.
Solution Approach 2:
The patent employs parameter changes by systematically mutating amino acid sequences at specific positions (residues 24-79 and 215-270) within the meganuclease structure. These sequence parameter modifications alter the DNA recognition and binding characteristics, enabling the enzyme to distinguish more precisely between the target HBV sequence and host genome sequences, thereby reducing off-target cutting.
2Reliability
If current anti-HBV drugs are administered, then HBV infection is suppressed, but severe adverse reactions occur
Solution Approach 1:
The patent replaces the chemical drug mechanism with a protein-based enzymatic mechanism. Instead of using interferon alpha or nucleoside analogues that cause adverse reactions, the invention uses engineered meganucleases that physically cleave the HBV DNA genome. This substitution of mechanism fundamentally changes the therapeutic approach, eliminating the harmful side effects associated with conventional drugs while maintaining anti-HBV efficacy through direct genomic disruption.
3Reliability
If conventional nucleoside analogues are used, then HBV replication is inhibited, but long-term administration is required
Solution Approach 1:
The patent applies preliminary action by delivering the meganuclease to infect hepatocytes before significant viral replication occurs. The enzyme is introduced via viral vector or other delivery mechanisms at the time of infection or early in the infection cycle, where it can immediately begin cleaving HBV DNA. This timing strategy disrupts viral replication before it establishes, potentially achieving long-term suppression without requiring continuous long-term administration.
Solution Approach 2:
The patent employs self-service through the mechanism of homing endonuclease activity. The engineered meganuclease recognizes and binds to specific HBV DNA sequences, and the cellular DNA repair machinery automatically processes the cleavage sites. This self-processing mechanism eliminates the need for continuous external intervention, as the system uses the cell's own repair pathways to achieve viral genome disruption, potentially reducing the need for long-term drug administration.
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 meganucleases effectively reduce HBV replication, leading to improved liver pathology and decreased progression to liver cirrhosis and hepatocellular carcinoma by specifically targeting and cleaving the HBV genome, thereby suppressing infection and proliferation.
Implementation Method 1
Cleavage at the recognition sequence by an engineered meganuclease described herein can disrupt expression of one or more viral proteins due to non-homologous end joining (NHEJ) at the cleavage site.
Implementation Method 2
Alternatively, a 'suicide gene' can be introduced into a Hepatitis B virus (HBV) genome via homologous recombination.
Data Source
AI summary
The present invention encompasses engineered nucleases which recognize and cleave a recognition sequence within a Hepatitis B virus (HBV) genome. The engineered meganucleases can exhibit at least one optimized characteristic, such as enhanced specificity and/or efficiency of indel formation, when compared to previously described HBV meganucleases. Further, the invention encompasses pharmaceutical compositions comprising engineered meganuclease proteins, nucleic acids encoding engineered meganucleases, and the use of such compositions for treating HBV infections or hepatocellular carcinoma.