Reconciling pillars of transient gene expression: From DNA prep via media, reagent and cell line development to holistic process optimization

Abstract

Transient gene expression (TGE) is a multi-parametric process which is built upon four essential influencing pillars: First of all, it is imperative to have an easy to transfect cell line which allows high product titers and is cultivated in suspension [1]. Secondly, only a few of the commercially available cell culture media allow / support transient transfection and production. Thus, it is highly recommended to select the appropriate medium to grow and transfect the favored cell line [2]. Thirdly, the quality, source and backbone of the plasmid DNA which contains the genetic information for the protein of interest has a major impact [3]. Last but not least, to introduce plasmid DNA into mammalian cells, selection of a suited transfection reagent plays an important role for high-yielding TGE processes. In this work, we summarize our recent development of a novel TGE system for efficient transient transfection and expression in HEK cells. In cooperation with emp Biotech, InVivo BioTech Services developed a transfection reagent with very low cytotoxicity. A culture medium that can be used for transfection and production was designed in collaboration with Xell AG. The establishment of a TGE optimized HEK cell line (HEK-INV) and a method for large scale plasmid preparation of a corresponding vector complete the optimized production platform. It is easy applicable, scalable and supports large scale transfection for the production of gram quantities of IgG within a few days.