Vaccinia Virus Vector with Segmented Promoters for Controlled Expression
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Solution Overview
Problem
Current poxvirus vectors do not simultaneously meet the criteria of being non-replicating in humans and animals, achieving high expression of recombinant genes for strong immunogenicity, minimizing anti-vector immune responses, and stable propagation in continuous cell lines.
Innovation Solution
A recombinant viral vector is developed, comprising a nucleic acid sequence encoding a heterologous DNA-dependent RNA polymerase linked to a pre-replicative promoter, a repressor protein linked to a post-replicative promoter, and an inactivating mutation in a transcription factor gene, allowing for controlled expression of heterologous polypeptides and stable replication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If poxvirus vectors are designed to replicate in human cells to achieve high immunogenicity, then immune response is enhanced, but the risk of uncontrolled replication and safety issues increases
Solution Approach 1:
The viral replication cycle is segmented into pre-replicative and post-replicative phases with distinct promoter systems. The pre-replicative promoter drives essential early gene expression for controlled replication initiation, while post-replicative promoters drive immunogenic protein expression only after replication has started, separating replication control from immune response activation.
Solution Approach 2:
Different promoter elements are assigned to different functional regions of the viral genome. Early/promoter regions control replication with restricted activity, while late/post-replicative regions control high-level expression of immunogenic proteins. This local differentiation allows replication and immunogenicity to be controlled independently in different genomic contexts.
2Duration of action of stationary object
If vector proteins are highly expressed to maintain viral replication, then viral propagation is stable, but anti-vector immune responses and competition with recombinant protein expression increase
Solution Approach 1:
Viral protein expression is organized in temporal waves corresponding to the viral replication cycle. Pre-replicative promoters drive early essential protein expression for replication establishment. Post-replicative promoters then drive a second wave of protein expression including immunogenic proteins after replication has been established, reducing competition and immune recognition of vector proteins.
Solution Approach 2:
The pre-replicative promoter system establishes viral replication and essential protein expression before the post-replicative promoter system activates. This preliminary action creates a controlled replication foundation that reduces the need for continued high-level vector protein expression, thereby reducing immune responses during the immunogenic protein expression phase.
3Object-affected harmful factors
If the virus is engineered to be non-replicating in humans for safety, then safety is improved, but the capacity for high-level recombinant protein expression and immunogenicity is reduced
Solution Approach 1:
A heterologous RNA polymerase from bacteriophage T7 serves as an intermediary transcription system. The viral pre-replicative promoter drives expression of this foreign polymerase, which then transcribes recombinant genes under T7 promoters. This intermediary system allows high-level recombinant protein expression without requiring the virus to replicate its own genome in human cells, maintaining safety while achieving productivity.
Data Source
AI summary
Expression vectors ideal for use in vaccinating individuals against disease based on vaccinia virus and other chordopoxviruses having high expression of recombinant genes and low expression of vector genes in target animals, and low expression of recombinant genes and high expression of vector genes in cells used for propagation.