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Trimeric SARS-CoV-2 Spike proteins produced from CHO-cells in bioreactors are high-quality antigens

By Paco Pino, Joeri Kint, Divor Kiseljak, Valentina Agnolon, Giampietro Corradin, Andrey V Kajava, Paolo Rovero, Ronald Dijkman, Gerco den Hartog, Jason S McLellan, Patrick Byrne, Maria J Wurm, Florian M Wurm

Posted 16 Nov 2020
bioRxiv DOI: 10.1101/2020.11.15.382044

The Spike protein of SARS-CoV-2 is essential for virus entry into human cells. In fact, most neutralizing antibodies against SARS-CoV-2 are directed against Spike, making it the antigen of choice for use in vaccines and diagnostic tests. In the current pandemic context, global demand for Spike proteins has rapidly increased and could exceed hundreds of grams to kilograms annually. Coronavirus Spikes are large, heavily glycosylated, homo-trimeric complexes, with inherent instability. Their poor manufacturability now threatens the availability of these proteins for vaccines and diagnostic tests. Here, we outline a scalable, GMP-compliant, chemically defined process for the production of a cell-secreted, stabilized form of the trimeric Spike protein. The process is chemically defined and based on clonal, suspension-CHO cell populations and on protein purification via a two-step, scalable down-stream process. The trimeric conformation was confirmed using electron microscopy and HPLC analysis. Binding to susceptible cells was shown using a virus-inhibition assay. The diagnostic sensitivity and specificity for the detection of serum SARS-CoV-2 specific IgG1 was investigated and found to exceed that of Spike fragments (S1 and RBD). The process described here will enable the production of sufficient, high-quality trimeric Spike protein to meet the global demand for SARS-CoV-2 vaccines and diagnostic tests. ### Competing Interest Statement ExcellGene declares that material resulting from this work is being provided commercially. ExcellGene authors declare that the interpretation of the results is done objectively. Conclusions and interpretation of results of non-ExcellGene authors (EM analysis, inhibition of virus infection, reactivity against patient sera) were solely based on their judgment.

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