Recombinant Cell Lines for Non-Segmented Negative-Strand RNA Virus Rescue
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Solution Overview
Problem
Current methods for generating recombinant non-segmented negative-strand RNA viruses from cDNA are inefficient and irreproducible, often requiring replication-competent vaccinia vectors and resulting in contamination by helper viruses, which complicates the production of stable and high-titer vaccines.
Innovation Solution
Development of recombinant cell lines expressing T7 phage RNA polymerase, nucleoprotein, and phosphoprotein, which are stably produced and integrated into the genome, allowing for the efficient and reproducible rescue of non-segmented negative-sense RNA viruses without contamination by helper viruses, using a system that includes a DNA flap for enhanced gene transfer and integration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If replication-competent vaccinia vectors are used to generate recombinant non-segmented negative-strand RNA viruses from cDNA, then virus production is enabled, but contamination by helper viruses occurs and reproducibility decreases
Solution Approach 1:
The system divides the helper function into separate stable cell lines, each expressing specific viral proteins (T7 RNA polymerase, nucleoprotein, phosphoprotein) from integrated genomic sequences rather than transient plasmids. This segmentation allows independent optimization and stabilization of each helper component, eliminating contamination issues while maintaining high virus production efficiency.
Solution Approach 2:
The helper proteins are expressed in advance and stably integrated into the cell genome before virus rescue. The T7 RNA polymerase, nucleoprotein, and phosphoprotein are constitutively expressed from integrated DNA sequences, preparing the cellular environment in advance for efficient and reproducible virus generation without requiring transient transfection or helper virus contamination.
2Productivity
If replication-competent vaccinia vectors are used, then virus rescue is achieved, but helper virus contamination complicates vaccine production
Solution Approach 1:
The harmful replication-competent vaccinia vector system is extracted and replaced with a safer alternative. The helper functions are isolated into stable cell lines expressing only the necessary proteins (T7 RNA polymerase, nucleoprotein, phosphoprotein) from integrated genomic sequences, eliminating contaminating helper viruses while maintaining rescue efficiency.
Solution Approach 2:
The system replaces the complex, contaminating replicating vaccinia vector with a stable, non-replicating cellular system where helper proteins are expressed from integrated DNA. This disposable-like approach uses stable cell lines that can be repeatedly used without the risks associated with replicating helper viruses.
3Adaptability or versatility
If cDNA is transfected into cells for virus generation, then recombinant virus production is possible, but stable and high-titer production is not achieved
Solution Approach 1:
The system merges the cDNA transfer system with stable cellular expression of helper proteins. The T7 RNA polymerase, nucleoprotein, and phosphoprotein are integrated into the cell genome and constitutively expressed, creating a unified system where transduced cDNA automatically benefits from stable helper function, achieving both high adaptability and high virus titer production.
Solution Approach 2:
The transduced cells become self-sufficient for virus production. The integrated helper gene sequences enable the cells to autonomously express all necessary proteins (T7 RNA polymerase, nucleoprotein, phosphoprotein) without external helper viruses or transient plasmids, allowing stable and high-titer recombinant virus production.
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
This approach enables the stable and high-efficiency production of recombinant viruses, such as measles vaccines, with improved reproducibility and reduced contamination, facilitating the generation of effective and safe multivalent vaccines.
Implementation Method 1
comprising integrated in its genome, at least one copy of a nucleic acid encoding a T7 phage RNA polymerase or its nuclear form (nlsT7)... wherein said T7 phage RNA polymerase or its nuclear form (nlsT7)... are expressed in a stable manner
Implementation Method 2
at least one copy of a nucleic acid encoding a nucleoprotein (N) of a non-segmented negative-strand RNA virus and at least one copy of a nucleic acid encoding a phosphoprotein (P) of a non-segmented negative-strand RNA virus... as a ribonucleoprotein complex (RNP complex), functional in transcription and replication
Implementation Method 3
and wherein said DNA flap is inserted immediately upstream of the promoter enabling transcription of the at least one nucleic acid... a DNA flap functionally associated with said nucleic acid(s)
Data Source
Figure 1A~1D
Figure 2A~2C
AI summary
The present invention relates to recombinant cells as well as to methods for the generation of non-segmented negative-sense single- stranded RNA viruses (NNV or mononegavirales) from cloned deoxyribonucleic acid (cDNA), especially from measles virus and in particular from attenuated strains such as those approved for vaccination, in particular from the attenuated Schwarz measles virus and various recombinant Schwarz measles-based viruses expressing heterologous sequences. Such rescued viruses can be used, after amplification, as vaccines for immunization against measles and/or against the heterologous peptides or proteins expressed.