We are trying to match an existing product profile. What tools are available to achieve this goal? What do you think about glycoengineering? Do you think it is better to try and control the glycosylation or engineer it?

Answer

The term glycoengineering has been changing over time.  Glycoengineering was traditionally defined as any tool used to modify or change the glycosylation patterns. There are 4 basic levers to pull to control the addition of glycans.  They are (1) the substrate – namely the sugar nucleotide mix and quantity, (2) the enzymes – glycotransferases and glycosidases, (3) the physical location where the additions occur – namely the ER and Golgi, and (4) the environment which can affect all of the other levers.  The early forms of glycoengineering used media components to shift the glycosylation patterns by adding a variety of sugars in addition to glucose.  Once the environmental parameters were shown to effect the glycosylation pattern, a new form of engineering developed in which parameters (such as pH and oxygenation) were monitored to target the profile of choice.  As technology has progressed, the specific genetic and protein targets became more clearly identified, and methods to specifically alter them have have been developed and utilized.  As an example, CRISPR can be used to make a specific genetic modification that would be beneficial for the particular biologic and glycosylation profile you are targeting.  The ideal strategy to optimize glycosylation pattern and achieve consistency would be to use a variety of engineering tools rather than utilizing an either/or strategy.  In our studies, we have looked at providing a method to improve the physical location where post-translational modifications occur – namely the ER and Golgi.  By targeting the physical structure, we have seen both an increase in the higher order glycoforms and increased consistency when Cell-Ess is used.