Transient Transfection of 293E Cells Using PEI and EBNA1
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for large-scale transient transfection of mammalian cells for recombinant protein production are limited by scalability, require complex processes, and are not well-suited for high-throughput production due to issues with cell line selection, transfection reagents, culture medium requirements, and the need for medium changes.
Innovation Solution
A process involving the use of suspension-growing 293 cell lines, specifically the 293E or 293SFE cells, combined with a polyethylenimine (PEI) transfection reagent and an expression vector containing the Epstein-Barr virus oriP sequence, which allows for high-level transient expression of recombinant proteins in a serum-free medium without medium changes, enabling scalable and high-throughput production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If stable transfectoma isolation and characterization is used for recombinant protein production, then sufficient amounts of protein with proper post-translational modifications are obtained, but the process becomes long and tedious
Solution Approach 1:
The invention extracts and utilizes specific viral elements (oriP and EBNA1) from the Epstein-Barr virus system to create a transient expression platform that achieves stable-like expression levels without requiring stable transfectoma isolation. This allows obtaining sufficient recombinant protein amounts while avoiding the time-consuming stable transfection process.
Solution Approach 2:
The expression vector is pre-designed with oriP origin and EBNA1 transgene incorporated, enabling the cells to maintain high levels of plasmid copies and protein expression transiently. This preliminary configuration of the vector system eliminates the need for subsequent stable transfectoma isolation steps.
2Quantity of substance
If monolayer culture is used for transient transfection, then significant amounts of recombinant proteins can be generated, but scalability is limited by culture surface availability
Solution Approach 1:
The invention transitions from static monolayer culture to dynamic suspension culture, allowing cells to grow in three-dimensional space rather than being constrained to two-dimensional surfaces. This dynamic culture system enables scalable production while maintaining high transient expression levels through the specialized expression vector system.
3Ease of manufacture
If calcium phosphate precipitation or PEI transfection is used for large-scale transient transfection, then cost-effective gene delivery is achieved, but expression levels and transfection efficiency vary
Solution Approach 1:
The invention changes the key parameters of the transfection system by incorporating specific viral elements (oriP and EBNA1) into the expression vector. This parameter change in the vector design enables consistent high-level expression and reliable transfection efficiency across large-scale operations while maintaining cost-effectiveness.
Solution Approach 2:
The expression vector functions as a composite system combining multiple functional elements: the CMV promoter for strong transcriptional activity, the oriP origin for episomal replication, and the EBNA1 transgene for maintaining plasmid copies. This composite vector structure ensures reliable and consistent transfection efficiency and expression levels.
4Quantity of substance
If 293T cells expressing SV40 large-T antigen are used, then episomal amplification of plasmids is enabled, but the system requires specific viral elements that may limit versatility
Solution Approach 1:
The invention creates a universal expression platform using the Epstein-Barr virus oriP and EBNA1 system that can be applied across different cell types and expression needs. The oriP-EBNA1 mechanism provides episomal amplification similar to SV40 systems but with broader applicability and fewer restrictions on vector design and cell line selection.
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 achieves high expression levels of recombinant proteins, up to 20% of total cellular proteins, with efficient transfection and protein production in a short time frame, facilitating the production of milligram quantities suitable for biochemical studies and screenings.
Implementation Method 1
a second DNA sequence enhancing transcriptional activity of the promoter and increasing nuclear import of the expression vector... the second DNA sequence additionally supports an episomal replication of the vector in the transfected cells
Implementation Method 2
the human cytomegalovirus (CMV) promoter... This promoter is particularly powerful in 293 cells, where it has been shown to be strongly transactivated by the constitutively expressed adenovirus E1a protein
Implementation Method 3
the recently described cationic polymer polyethylenimine (PEI)... provides cost-effective ways of introducing plasmid DNA into mammalian cells
Data Source
AI summary
Disclosed is a new process for the production of recombinant proteins, by transient transfection of suspension-grown human embryonic kidney cells (293 cell line and its genetic variants) with an expression vector, using polyethylenimine (PEI) as a transfection reagent. In a preferred embodiment, the process uses 293E cells expressing the Epstein-Barr virus (EBV) EBNA 1 protein, in combination with an oriP-based episomal expression vector having an improved cytomegalovirus expression cassette comprising the CMV5 promoter. The process combines in a single step the cell growth, transfection and protein expression, is carried out without changing the culture medium, and allows to achieve high expression levels in a short period of time. The process may be carried out in a serum-free, low-protein culture medium, is easily scalable, compatible with continuous production processes, and fully adapted to high-throughput production of milligram quantities of recombinant proteins.