Establishment of the REMBAC-cassette, a rapid, efficient and manifold BacMam tool for recombinant protein expression.

Efficient recombinant protein production requires mammalian stable cell lines or often relies on inefficient transfection processes. Baculoviral transduction of mammalian cells (BacMam) offers cost-effective and robust gene transfer and straightforward scalability. The advantages over conventional approaches are, no need of high biosafety level laboratories, efficient transduction of various cell types and transfer of large transgenes into host cells. In our study, we aim to develop a high expression cassette to increase yields of baculoviral transduction. The establishment follows a sequential approach by first identifying the strongest promoter, followed by intron and WPRE sequences as enhancer elements for transcription and translation. The resulting REMBAC-cassette was compared to conventional transfection in suspension and adherent cells. Irrespective of the cell line, transduction reached nearly 100 % efficiency and led to almost 10-fold increases of gene expression levels. We confirmed these results in larger scale with batch and fed-batch cultivations. Finally, expression of different soluble proteins with high degrees of complexity confirmed the versatility of our established cassette. Overall, the REMBAC-cassette incorporated into the BacMam platform is a manifold tool offering advantages over standard transfection, in the scalability, efficiency and gene expression, which results in higher yields, shorter cultivation times and consequently cost-effective production processes.