Transient expression stands for the temporary expression of a protein. For many applications, e.g., drug discovery, high-throughput screening, assay development or early stage pre-clinical drug development, transient expression offers the advantages of achieving both fast process times and high yields. It is usually achieved by simply transfecting the gene of interest as circular plasmid into the respective producer cells.
The protein is expressed only over a short period of time (few days) since the expression plasmid is lost during mitosis of the cells. To improve the stability of a plasmid, several approaches can be made, one being the use of the Simian Virus 40 (SV40) replication system. Here, the large T antigen of SV40 is expressed allowing the replication of plasmids with an SV40 origin of replication (SV40 ori).
CEVEC´s CAP-T cells stably express intracellular T-antigen of SV40. An optimized plasmid contains an expression cassette for the gene of interest and the SV40 ori. This way, the plasmid replicates extra-chromosomally and can be kept stable for several days up to weeks without further selection pressure.
When directly compared, CAP-T cells clearly outperform different versions of HEK293 cells in protein production yields. Their outstanding performance is due to several features:
- Optimal viability of cells even after extensive process duration
- Upscaling possible, using all common types of bioreactors
- Transfection of very high cell densities results in sustained high-level expression and can be enhanced e.g., by addition of butyrate
Further advantages of transient protein expression with CAP-T cells:
- Easily scalable from laboratory scale up to multiple liters in batch and fed-batch bioreactors
- Especially suited for complex proteins and antibodies
- Authentic human post-translational modifications
- From gene to mg amounts of protein within two weeks