Mechanisms underlying improved molecular pharming by protease inhibitors

Molecular Pharming is a fast-growing new industry in which plants are used to produce vaccines, antibodies, glycohormones and other pharmaceutical proteins. Thanks to the quick, transient expression of biopharmaceuticals in glyco-engineered Nicotiana benthamiana plants by infiltration with Agrobacterium tumefaciens (agroinfiltration), there are now companies that are able to produce 10 million influenza vaccines in only 6 weeks compared to more traditional methods that can take in excess of 9 months. Since early 2017, the UK now has a purpose-built facility based on the Norwich Research Park. The company, Leaf Expression Systems (LES), is able to use a proprietary plant-based expression platform to prepare a variety of different proteins, including vaccines and antibodies.
Processing and proteolysis by endogenous plant proteases is currently a major obstacle in the agroinfiltration platform. Supported by ERC funding, the VdH laboratory is unravelling the proteolytic machinery of N. benthamiana. We have recently identified three new, unrelated protease inhibitors that boost levels of recombinant glycoproteins (RGPs: antibodies, glycohormones and human enzymes). When co-expressed with RGPs, these protease inhibitors cause a 10-40 fold increase in RGP levels. Interestingly, co-expression of protease inhibitor combinations increases the RGP expression levels even further, indicating that they suppress a proteolytic network that involves proteases from different catalytic classes.
The AIM OF THIS PROJECT is to use these protease inhibitors in the Molecular Pharming context at LES in Norwich, and to identify the underlying molecular mechanism in the VdH lab in Oxford. This project takes advantage of the extensive toolbox and expertise on proteases in the VdH laboratory and establishes an exciting collaboration with a new industry in the UK.