Hcov oc43 spike proteins

For AIR assays, SARS-CoV-2, SARS-CoV, MERS, and Influenza Type A and B antigens were obtained from Sino Biological, Inc., and are described in more detail below. Most antigens were supplied as lyophilized material and reconstituted at the recommended concentrations using 18-MΩ water, while the remaining antigens were supplied frozen on dry ice. PBS-ET was prepared as phosphate buffer (10 mM monobasic sodium phosphate, 10 mM dibasic sodium phosphate, 150 mM NaCl) with 0.02% w/v Tween-20 and 5 mM EDTA. Amine-reactive substrates for fabrication of AIR arrays were provided by Adarza BioSystems, Inc. For ELISA assays, SARS-CoV-2 full-length spike and RBD were produced in-house using a mammalian expression system (Stadlbauer et al., 2020b ; Amanat et al., 2020 ), as was influenza A/H1N1/California 2009 hemagglutinin. SARS-CoV-2 nucleocapsid expressed in mammalian cells was obtained from RayBiotech, while HCoV-229E and HCoV-OC43 spike proteins (baculovirus-expressed) were obtained from Sino Biological. Tetanus toxoid (TTd) was obtained from Calbiochem.