SARS-CoV-2 Delta B.1.617.2 Variant Recombinant Spike Trimer His Tag

Concentration–response curves for binding of CoV2 spike protein to human ACE2 in cell-free ELISA-type assays. Microtiter wells were coated with 100 uL of ACE2-Fc at 2 ug/mL in PBS at 4˚C overnight. The wells were washed with PBS and blocked with 200 µL of 1% BSA/PBS at RT for 1 hour. Spike trimer was serially diluted from 10 µg/mL in 1% BSA/PBS. The blocker was discarded, and the wells were incubated with 100 µL of serially diluted spike trimer at RT for 1 hour. The wells were washed with PBS and the bound spike trimer was detected with 100 µL of Peroxidase AffiniPure Rabbit Anti-His Tag (Jackson Immuno Research 300-035-240)(1:5,000 in 1% BSA/PBS) at RT for 1 hour. The wells were washed with PBS and the wells were developed with 100 µL of MB/E Ultra-Sensitive, Blue, Horseradish Peroxidase Substrate (EMD Millipore ES022-500ml) at RT for 5 min. The reaction was stopped with 100 µL of 0.6N H2SO4 and the signals were read at 450 nm using a plate reader (Biotek).

SARS-CoV-2 Spike Trimer, His Tag B.1.617.2 on SDS-PAGE under non-reducing (NR) and reducing (R) conditions. The gel was stained with Coomassie G-250 per manufacturer instructions. The purity of the protein is greater than 95% and it is between 175 and 270 kDa.