Baculovirus Budding via VSV-G Stem Fragment
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Solution Overview
Problem
GP64null baculoviruses face severe defects in virion production and lack specificity in cell targeting, limiting their application in gene therapy and other biotechnological uses due to inefficient budding and promiscuous entry into cells.
Innovation Solution
The introduction of a membrane proximal fragment of the VSV G protein (G-stem) into the genome of gp64null baculoviruses, which includes specific amino acid sequences from the C-terminal portion, transmembrane domain, and cytoplasmic tail, enhances budding efficiency and allows for targeted cell entry by displaying heterologous proteins on the virion surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If GP64 is deleted from baculovirus genome to enable heterologous protein expression, then protein expression flexibility is improved, but virion production efficiency deteriorates
Solution Approach 1:
The patent introduces an intermediary protein (such as VSV-G or other viral envelope proteins) that mediates the budding process in place of the deleted GP64 protein. This intermediary protein is expressed from a separate plasmid and facilitates virion assembly and release, thereby maintaining high virion production efficiency while allowing the baculovirus genome to be used for heterologous protein expression.
Solution Approach 2:
The patent segments the viral envelope protein function into two separate components: the structural envelope protein (GP64) that is deleted from the baculovirus genome to allow heterologous expression, and a separate intermediary budding protein (VSV-G or similar) that is expressed from a plasmid to maintain virion production. This functional segmentation resolves the contradiction between protein expression flexibility and virion production efficiency.
2Productivity
If VSV G protein is used to rescue budding in gp64null viruses, then virion production is improved, but cell targeting specificity deteriorates
Solution Approach 1:
The patent employs a dynamic system where the choice of intermediary protein can be changed or optimized based on the specific application requirements. Different envelope proteins (VSV-G, F proteins from other baculoviruses, or custom-designed proteins) can be used as intermediaries to achieve either high virion production or specific cell targeting, allowing the system to adapt dynamically to different needs.
Solution Approach 2:
The patent applies local quality by using different intermediary proteins for different functional requirements: VSV-G for high virion production, or specific F proteins from other baculoviruses for targeted entry into specific cell types. This allows the budding mechanism to have different properties in different contexts, resolving the contradiction between production efficiency and targeting specificity.
3Ease of operation
If F envelope proteins from other baculoviruses are used for pseudotyping, then some cell targeting capability is improved, but entry efficiency into mammalian cells deteriorates
Solution Approach 1:
The patent uses F envelope proteins from other baculoviruses as intermediary proteins that mediate both budding and entry functions. While these F proteins provide some cell targeting capability, they also serve as efficient mediators for virion assembly and release, thereby maintaining good entry efficiency into mammalian cells while providing targeted entry capability through the specific F protein chosen.
Data Source
AI summary
The present invention provides a method for restoring budding capability to GP64null baculoviruses including gp64null AcMNPV by expressing therein a portion of the VSV G protein gene or a truncated “stem” portion of the GP64 gene. Other embodiments provide methods to use portions of the G-stem or GP64 protein to target foreign proteins for display on virions.