Self-replicating DNA vectors via rolling circle replication
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Solution Overview
Problem
DNA vaccines face challenges in achieving robust immunogenicity due to inefficient DNA delivery into mammalian cell nuclei, leading to low T-cell responses, particularly in retroviral infections like HIV-1, and are limited by biological degradation and gene silencing mechanisms.
Innovation Solution
Development of self-replicating DNA expression vectors derived from Beak and Feather Disease Virus (BFDV) that utilize a viral rolling circle replication cycle to amplify gene copy numbers and maintain episomal presence, stimulating innate immune responses through pathogen recognition receptors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If DNA vaccines are delivered into mammalian cells, then antigen expression is achieved, but delivery into cell nuclei is inefficient leading to low immunogenicity
Solution Approach 1:
The patent applies self-service by enabling the DNA vaccine vector to self-replicate within the host cell using the rolling circle replication mechanism. The vector contains viral origin of replication sequences and replication proteins that allow it to autonomously amplify its copy number without requiring nuclear delivery, thus solving the delivery efficiency problem while maintaining reliable antigen expression and immunogenicity
Solution Approach 2:
The patent changes the fundamental parameter of DNA vector behavior from non-replicating to self-replicating. By incorporating viral replication origins and proteins, the vector transforms its replication parameters to enable autonomous amplification in the cytoplasm, bypassing the nuclear delivery bottleneck and significantly improving both delivery efficiency and immunogenicity
2Ease of manufacture
If conventional DNA vaccines are used, then ease of manufacture and distribution is achieved, but robust T-cell responses are not generated
Solution Approach 1:
The self-replicating vector serves itself by containing all necessary viral replication elements (origins and proteins) to autonomously amplify within host cells. This self-service capability maintains the ease of manufacture and distribution of DNA vaccines while dramatically improving T-cell response through sustained high-level antigen expression from amplified vector copies
Solution Approach 2:
The rolling circle replication mechanism creates periodic action by continuously generating new vector copies over time. This periodic amplification maintains persistent antigen expression levels that significantly enhance T-cell activation compared to transient expression from non-replicating vectors, while preserving DNA vaccine manufacturing advantages
3Reliability
If DNA vaccine dosage is increased to improve immunogenicity, then antigen expression increases, but biological degradation and gene silencing occur
Solution Approach 1:
The self-replicating vector serves itself by autonomously maintaining and amplifying its population within host cells. This self-maintenance capability ensures stable vector composition and persistent antigen expression without requiring increased dosages, thereby improving immunogenicity while avoiding biological degradation and gene silencing that occur with high-dose conventional DNA vaccines
Solution Approach 2:
Instead of using excessive DNA dosage that leads to degradation and silencing, the patent employs partial action through controlled self-replication of a lower initial dose. The vector replicates to achieve sufficient antigen expression levels without the harmful effects of excessive external DNA administration, maintaining stability while improving immunogenicity
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 self-replicating vectors enhance antigen expression and immunogenicity by mimicking acute viral infection, overcoming limitations of non-replicating DNA vaccines, and are safe due to confined replication within cells, activating strong innate and adaptive immune responses.
Implementation Method 1
the Rep protein binds to the BFDV LIR element to initiate rolling circle replication in a mammalian host cell that amplifies the vector including the gene encoding the protein of interest to high copy number
Implementation Method 2
stimulating innate immune responses through pathogen recognition receptors... the detection of pathogen genomic replication might be a critical indicator of pathogen viability, that is used by the innate immune system to determine the level of biological threat
Data Source
AI summary
The present invention relates to self-replicating DNA expression vectors comprising elements from Beak and Feather Disease Virus (BFDV), including a BFDV LIR element comprising an origin of replication (Ori), genes encoding a BFDV Rep protein and a heterologous polypeptide of interest under the control of a mammalian promoter, wherein the Rep protein is capable of binding to the Ori to initiate replication of the expression vector. Pharmaceutical compositions and cells comprising the self-replicating vectors are also provided. The self-replicating vectors may be used in methods of inducing an immune response or expressing a polypeptide in a subject, or as an expression system.