Use of CHO cell synthetic promoters to control transcription of mAb expression vector genes and screening of ER genes for their effect on mAb production

The recombinant manufacture of therapeutic monoclonal antibody (mAb) molecules from Chinese hamster ovary (CHO) cell cultures represents a vital supply of important medicines with global demand. Innovations within this recombinant manufacturing process that can either increase mAb yield or speed up the supply of mAb product are therefore very highly sought after. These innovations could come from genetic engineering of either the mAb expression vector or the CHO host cell. Chapters 3, 4 and 5 of this manuscript focus on plasmid vector engineering, specifically the development and implementation of synthetic promoter sequences to control the transcription of mAb LC/HC and GS selection marker genes, replacing the conventionally-used viral promoters hCMV and SV40 respectively. In chapter 4 different LC/HC synthetic promoter pairs were used, for the first time, in the generation of stably expressing CHO pools. Compared to the use of conventional hCMV promoters to control LC and HC transcription, these synthetic promoter-containing pools consistently recovered 3 – 7 days faster from MSX selection and in some cases produced higher mean mAb titres (up to 1.3-fold). In chapter 5, synthetic promoters were used for the control of GS transcription in stably expressing CHO pools. The synthetic GS promoter SynSV40_2 was found to generate up to 1.9-fold higher mean cell-specific productivity (qP) when combined with LC/HC synthetic promoters compared to the conventional SV40 promoter. Chapter 6 focused on finding targets for CHO host cell engineering through high-throughput transient transfection screening of genes acting within the endoplasmic reticulum (ER) for their effect on mAb production. The gene pERP1 was shown consistently and robustly to increase qP of mAb-expressing cells by up to 1.6-fold and overexpression of this gene therefore represents a novel CHO host cell engineering target. Overall, the work described within this manuscript led to the discovery of strategies for improving CHO-based recombinant mAb manufacture.