Monoclonal antibodies (mAbs) are used for specific treatment of a wide range of diseases that affect the cardiovascular, liver, gastrointestinal and immune systems. The efficacy, safety, and serum half-life are all important characteristics that can be affected by glycans. Glycans are carbohydrate chains found on the antibody whose presence and composition influence the interactions of the mAbs within the body. Process changes such as temperature shifts and culture feeding strategies are known to have significant effects on glycan structures.
In this project, Chinese hamster ovary cells were used to produce a novel antibody product with Fab glycosylation. The cells were subjected to changes in culture and the affects on culture pH affected antibody production, glycosylation, the cell metabolome, and transcriptome were investigated. A reduction in pH to 6.8, was found to increase productivity by up to 50% and increase the level of glycan processing on the antibody. An increased pH of 7.3 was found to have an opposite effect, reducing the productivity by up to 40%, and reducing the level of glycan processing. These differences were consistent across different parent cells tested.
The mechanism behind the effect of the pH shift was investigated through a combination of transcriptomics, metabolomics, and flow cytometry. A significant change in the cell’s Golgi body was seen in cultures subjected to a reduction in pH. Cultures grown at pH 6.8 were found to have an initial reduction in Golgi size but as culture time progressed the Golgi body increased to 2-3 times the size that of the control cultures. This was hypothesized to lead to the increased processing of the glycans seen in the reduced pH cultures. A Golgi stress pathway was investigated as the source of the increase in Golgi size, but RNA-sequencing results eliminated this. Further work needs to be conducted in order to fully elucidate the mechanisms behind the increase in Golgi body size and how this affects the production and glycosylation of the antibody.