The antigen was produced in a bioreactor based on a selected stable CHO clone. A fed-batch strategy was used for high-cell-density cultivation and expression of the RBD fusion heterodimer. Upon harvest, the cell broth was clarified by depth filtration. The clarified supernatant was further purified via sequential chromatography. The purified antigen was then buffer exchanged by tangential flow filtration and filter sterilised. Purity and integrity were evaluated by SDS-PAGE with
Bolt™ 4 to 12% Bis-Tris gels (Thermo Fisher, ref. NW04120BOX), stained with
One-Step Blue Protein Gel Stain (Biotium, ref. 21003), and by SEC-HPLC with an Xbridge Protein BEH SEC (Waters, ref. 186009160) connected to an
HP1100 system (Agilent Technologies).
The affinity test of the RBD heterodimer with human ACE2 by surface plasmon resonance (SPR) was performed by ACROBiosystems. The Fc-tagged ACE2 (AC2-H5257, ACROBiosystems) was immobilised in a
Series S Sensor Chip CM5 (Cytiva) on a
Biacore T200 (Cytiva) using the
Human Antibody Capture Kit (Cytiva). The affinity measure was obtained using 8 different RBD heterodimer concentrations. The antigen structure simulations were performed with UCSF ChimeraX.
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Barreiro A., Prenafeta A., Bech-Sabat G., Roca M., Perozo Mur E., March R., González-González L., Madrenas L., Corominas J., Fernández A., Moros A., Cañete M., Molas M., Pentinat-Pelegrin T., Panosa C., Moreno A., Puigvert Molas E., Pol Vilarrassa E., Palmada J., Garriga C., Prat Cabañas T., Iglesias-Fernández J., Vergara-Alert J., Lorca-Oró C., Roca N., Fernández-Bastit L., Rodon J., Pérez M., Segalés J., Pradenas E., Marfil S., Trinité B., Ortiz R., Clotet B., Blanco J., Díaz Pedroza J., Ampudia Carrasco R., Rosales Salgado Y., Loubat-Casanovas J., Capdevila Larripa S., Prado J.G., Barretina J., Sisteré-Oró M., Cebollada Rica P., Meyerhans A, & Ferrer L. (2023). Preclinical evaluation of a COVID-19 vaccine candidate based on a recombinant RBD fusion heterodimer of SARS-CoV-2. iScience, 26(3), 106126.