Comprehensive mRNA‐sequencing‐based characterization of three HEK‐293 cell lines during an rAAV production process for gene therapy applications

Human embryonal kidney cells (HEK-293) are the most common host cells used for transient recombinant adeno-associated virus (rAAV) production in pharmaceutical industry. To better cover the expected gene therapy product demands in the future, different traditional strategies such as cell line sub-cloning and/or addition of chemical substances to the fermentation media have been used to maximize titers and improve product quality. A more effective and advanced approach to boost yield can be envisaged by characterizing the transcriptome of different HEK-293 cell line pedigrees with distinct rAAV productivity patterns to subsequently identify potential gene targets for cell engineering. In this work, the mRNA expression profile of three HEK-293 cell lines, resulting in various yields during a fermentation batch process for rAAV production, was investigated to gain basic insight into cell variability and eventually to identify genes that correlate with productivity. Mock runs using only transfection reagents were performed in parallel as a control. It finds significant differences in gene regulatory behaviors between the three cell lines at different growth and production stages. The evaluation of these transcriptomics profiles combined with collected in-process control parameters and titers shed some light on potential cell engineering targets to maximize transient production of rAAV in HEK-293 cells.