Measurement of SARS-CoV-2-Spike-specific IgG in Plasma
We next determined the levels of SARS-CoV-2 Spike IgG using CoVS1-RBD ELISA kit (Ray Biotech, GA) per the manufacture’s manual. Briefly, the 96 well plates coated with the SARS-CoV-2 S1 RBD protein were incubated with plasma followed by biotinylated anti-human IgG. After washing, HRP-conjugated streptavidin was added, and spike-specific IgG was quantitated by OD450 nm reading.