Multiple Indirect ELISAs for Serological Detection of SARS-CoV-2 Antibodies

Abstract

<jats:p>As the coronavirus disease 2019 (COVID-19), which is caused by the novel coronavirus SARS-CoV-2, continues to spread rapidly around the world, there is an urgent need for validated serological assays to evaluate viral specific antibody responses in COVID-19 patients or recovered individuals. In this study, we established and used indirect Enzyme Linked Immunosorbent Assay (ELISA)-based serological tests to study the antibody response in COVID-19 patients. In order to validate the assays, we determined the cut-off values, sensitivity and specificity of the developed assays using sera collected from COVID-19 patients in Saudi Arabia at different time points after disease onset, as well as sera that are seropositive to other human CoVs; namely MERS-CoV, hCoV-OC43, hCoV-NL63, hCoV-229E, and hCoV-HKU1. The SARS-CoV-2 S1 subunit of the spike glycoprotein and nucleocapsid (N) ELISAs that we developed here not only showed high specificity and sensitivity, but also did not show any cross-reactivity with other CoVs. We also showed that all RT-PCR confirmed COVID-19 patients included in our study developed both virus specific IgM and IgG as early as one week after the onset of disease. The availability of these validated assays will enable us to determine the nature and duration of the antibody response mounted in response to SARS-CoV-2 infection. It will also allow conducting large-scale epidemiological studies to determine evidence of previous exposure to the virus and assess the true extent of virus spread within communities.</jats:p>

Performance of Commercially Available Rapid Serological Assays for The Detection of SARS-CoV-2 Antibodies

“…On the other hand, the median OD values of the 46 RT-PCR con rmed positive cases were signi cantly higher for both IgM (0.82; ranging from 0.08 to 4.86) and IgG (2.75; ranging from 0.07 to 4.16). Based on the predetermined cut-off values (Algaissi et al, 2020), and the samples used in this study, the overall sensitivity of IgG ELISA vs RT-PCR was 83% (95% CI: 63-91%; 38/46). All the 8 false negative samples were from samples collected at early time points post symptoms onset (6 samples during the rst week and 2 samples on day 8).…”

“…Thus, in this study, we aimed to evaluate the performance of several commercially available immunoassays and compare them to our in-house developed and validated ELISA using samples derived from RT-PCR con rmed COVID-19 patients and healthy controls. In-house indirect ELISA based on the nucleocapsid (N) protein was performed as previously describe (Algaissi et al, 2020). Brie y, 96-well ELISA microplates were coated with in-house produced recombinant SARS-CoV-2 N protein at a concentration of 4 µg/ml in phosphate-buffered saline (PBS).…”