Pilot production of SARS-CoV-2 related proteins in plants: a proof of concept for rapid repurposing of indoors farms into biomanufacturing facilities

Abstract

The current CoVid-19 crisis is revealing the strengths and the weaknesses of the world's capacity to respond to a global health crisis. A critical weakness has resulted from the excessive centralization of the current biomanufacturing capacities, a matter of great concern, if not a source of nationalistic tensions. On the positive side, scientific data and information have been shared at an unprecedented speed fuelled by the preprint phenomena, and this has considerably strengthened our ability to develop new technology-based solutions. In this work we explore how, in a context of rapid exchange of scientific information, plant biofactories can serve as a rapid and easily adaptable solution for local manufacturing of bioreagents, more specifically recombinant antibodies. For this purpose, we tested our ability to produce, in the framework of an academic lab and in a matter of weeks, milligram amounts of six different recombinant monoclonal antibodies against SARS-CoV-2 in Nicotiana benthamiana. For the design of the antibodies we took advantage, among other data sources, of the DNA sequence information made rapidly available by other groups in preprint publications. mAbs were all engineered as single-chain fragments fused to a human gamma Fc and transiently expressed using a viral vector. In parallel, we also produced the recombinant SARS-CoV-2 N protein and its Receptor Binding Domain (RBD) in planta and used them to test the binding specificity of the recombinant mAbs. Finally, for two of the antibodies we assayed a simple scale-up production protocol based on the extraction of apoplastic fluid. Our results indicate that gram amounts of anti-SARS-CoV-2 antibodies could be easily produced in little more than 6 weeks in repurposed greenhouses with little infrastructure requirements using N. benthamiana as production platform. Similar procedures could be easily deployed to produce diagnostic reagents and, eventually, could be adapted for rapid therapeutic responses.

Rapid expression of COVID-19 proteins by transient expression in tobacco

“…Other recent reports (Diego-Martin et al, 2020;Makatsa et al, 2020;Margolin et al, 2020;Rattanapisit et al, 2020) indicate similar results. The rapid and high level of expression makes this an attractive system for larger scale production for research, or development of tests or of vaccines.…”

“…We successfully purified recombinant spike and Nucleocapsid SARS-CoV-2 proteins from N. benthamiana at a concentration comparable to other studies (Diego-Martin et al, 2020;Makatsa et al, 2020;Margolin et al, 2020;Rattanapisit et al, 2020). The spike ectodomain was purified in both monomeric and trimeric forms, suggesting that it was folding properly.…”

“…Together, our data support the idea that plants are a suitable eukaryotic system for recombinant production of SARS-CoV-2 proteins. Indeed, other studies have used plant-produced SARS-CoV2 antigens in ELISA assays to detect human antibodies, as well as monoclonal antibodies produced in planta, demonstrating their efficacy in diagnostics (Diego-Martin et al, 2020;Makatsa et al, 2020;Rattanapisit et al, 2020).…”

“…While our yield of SARS-CoV-2 proteins from tobacco was modest compared to other expression systems, plants still offer several advantages as a heterologous system for protein production. Producing recombinant proteins in plants can easily and affordably be scaled up compared to other systems, offering decentralized capabilities in times of rapid demand for diagnostics (Diego-Martin et al, 2020). Although more research is needed to fully understand the dynamics of COVID19 immunity, recent studies indicate that protective immunity may only last over a period of months (Poland et al, 2020).…”

Build a Sustainable Vaccines Industry with Synthetic Biology

“…Using plants as the production factory could prove more rapid and scalable than conventional methods. Medicago recently announced the construction of a facility to grow plants with a capacity for 40–50 million planned doses of flu vaccine per year [ 61 ]. Alt-text: Box 2 …”