SARS-CoV-2 specific antibody responses in COVID-19 patients

NISREEN M.A. OKBA; Marcel A Muller; Wentao Li; Chunyan Wang; Corine H. GeurtsvanKessel; Victor M. Corman; Mart M. Lamers; Reina S. Sikkema; Erwin de Bruin; Felicity D. Chandler; Yazdan Yazdanpanah; Quentin Le Hingrat; Diane Descamps; Nadhira Houhou-Fidouh; Chantal B. E. M. Reusken; Berend-Jan Bosch; Christian Drosten; Marion P.G. Koopmans; Bart L. Haagmans

Next, we validated the sensitivity and specificity of 2 commercial ELISA kits for detecting S1-specific IgG and IgA antibodies using the same cohort (Table1, Figure 3 ). All three COVID-19 patients had reactive antibodies by both the IgG (6/10 serum samples) and IgA (7/10 serum samples) ELISAs (Figure 3) . While SARS-CoV patient's sera were reactive as noted earlier, we also detected reactivity of serum samples from the validation cohorts A-D; 10/203 for IgA and 7/203 for IgG ELISAs. Two HCoV-OC43 (a β-CoV) patients' sera were reactive in both IgG and IgA ELISA kits. We confirmed the cross-reactivity of the two sera by testing twelve serum samples from both patients collected at different time points, pre-and post-OC43 infection. While all pre-infection sera were negative, all post-infection sera were reactive in both IgG and IgA based ELISAs. We have earlier reported cross-reactivity of these sera in a MERS-CoV S1 IgG ELISA kit (6) . Further validation was also done in a different laboratory author/funder, who has granted medRxiv a license to display the preprint in perpetuity.