A High Through-put Assay for Circulating Antibodies Directed against the S Protein of Severe Acute Respiratory Syndrome Corona virus 2

Svenja Weiss; Jeromine Klingler; Catarina Hioe; Fatima Amanat; Ian Baine; Erna Milunka Kojic; Jonathan Stoever; Sean Liu; Denise Jurczyszak; Maria Bermudez-Gonzalez; Viviana Simon; Florian Krammer; Susan Zolla-Pazner

Eleven serum specimens were tested from eight different patients with confirmed SARS-CoV-2 infection. Specimens from four uninfected individuals were used which had been banked as part of an ongoing longitudinal study prior to the COVID-19 outbreak. The assays were performed in a BSL 2 lab since they do not involve live virus; normal blood precautions employed when handling all human specimens were used for these studies. Serum specimens were heat inactivated (30 min at 60 o C) prior to use in the assay. The specimens were screened for the presence of Abs reactive with soluble recombinant trimeric mammalian cell expressed S protein (mSpike) or mRBD (Figure 1 ) using a secondary Ab that detects total Ig. All patient specimens reacted strongly with SARS-CoV-2 antigens (Figures 1 and 2) , although reactivity with the mSpike was generally stronger than with mRBD ( Figure 1 ). This is consistent with the findings of Amanat et al. 7 although different sera were used in their experiments and ours. The three sera from the uninfected patients did not react with either antigen (Figures 1 and 2) , and there was no reactivity in the presence of PBS but no serum (data not shown).