Non-transfected (–) and transfected (+) 293T whole cell extracts (30 μg) were separated by 5% SDS-PAGE, and the membrane was blotted with SARS-CoV-2 (COVID-19) Spike (N439K Mutant) antibody (GTX135961) diluted at 1:5000. The HRP-conjugated anti-rabbit IgG antibody (GTX213110-01) was used to detect the primary antibody.