Chimeric Yellow Fever Zika Virus Propagation Protocol
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Solution Overview
Problem
Current methods for developing vaccines against Zika virus are hindered by the challenge of propagating highly attenuated chimeric viruses, such as the YFV 17D-ZIK prME chimera, which fail to spread effectively in cell culture using traditional serial passaging or intracranial inoculation in mice.
Innovation Solution
A protocol involving prolonged passaging of cells transfected with a DNA-based construct expressing the chimeric virus genome is implemented, allowing for the replication of the virus to high titers, enabling effective propagation and infection of naïve Vero cells without the need for intracellular passaging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If classical serial passaging of extracellular recombinant virus particles is used, then virus propagation is attempted, but measurable virus progeny is not obtained for highly attenuated chimeric viruses
Solution Approach 1:
The patent applies preliminary action by performing intracellular passaging before extracellular serial passaging. Cells are first transfected with the chimeric virus genome and allowed to replicate intracellularly, establishing a productive infection before attempting extracellular virus recovery and serial passaging. This preliminary intracellular replication step ensures that the virus has established itself within the cellular environment, overcoming the attenuation barrier that prevents effective extracellular propagation.
Solution Approach 2:
The patent uses cell culture as an intermediary medium between the attenuated chimeric virus and the desired virus progeny. Instead of attempting direct extracellular serial passaging which fails for highly attenuated viruses, the cell culture serves as an intermediary that enables intracellular replication first, followed by successful extracellular virus recovery and serial passaging, thereby bridging the gap between virus attenuation and propagation capability.
2Productivity
If intracranial inoculation in mice is used to rescue recombinant virus, then virus propagation is attempted, but measurable virus progeny is not obtained for highly attenuated chimeric viruses
Solution Approach 1:
The patent replaces the mechanical/invasive approach of intracranial inoculation in mice with an in vitro cell culture-based system. Instead of using animal models to rescue and propagate the virus, the patent employs transfected cell cultures that can replicate the chimeric virus genome intracellularly and produce measurable virus progeny through controlled extracellular passaging, thereby substituting a more suitable and less invasive propagation mechanism.
3Object-affected harmful factors
If the chimeric virus is highly attenuated to ensure safety, then vaccine potential is improved, but ability to propagate in cell culture is severely limited
Solution Approach 1:
The patent segments the virus propagation process into distinct phases: intracellular replication phase (where the attenuated chimeric virus replicates within transfected cells) and extracellular serial passaging phase (where the virus is recovered and propagated in cell culture supernatant). This segmentation allows the virus to maintain its attenuated, safe characteristics during intracellular replication while still achieving successful extracellular propagation through the controlled two-stage process.
Solution Approach 2:
The patent utilizes parameter changes in the cell culture environment to facilitate propagation. By adjusting culture conditions such as medium composition, temperature, and passage timing, the patent optimizes both intracellular replication and extracellular virus recovery. These parameter changes enable the highly attenuated virus to propagate effectively in cell culture while maintaining its safety profile, resolving the contradiction between attenuation and propagability.
Data Source
AI summary
The present invention relates to chimeric yellow fever—Zika strains and attenuated versions thereof, wherein the nucleotide sequence encoding the signal sequence and prME protein of said yellow virus is replaced by a nucleotide sequence encoding the signal sequence and the prME protein of a Zika virus.