Development and Characterization of a Quantitative ELISA to Detect Anti-SARS-CoV-2 Spike Antibodies

Abstract

A novel clinical assay for the detection and quantitation of antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was adapted from an in-house, research-based enzyme-linked immunosorbent assay (ELISA). Development and validation were performed under regulatory guidelines, and the test obtained emergency use authorization (EUA) from the New York State Department of Health (NYSDOH) and the Food and Drug Administration (FDA). The Mount Sinai COVID-19 antibody assay is an orthogonal, quantitative direct ELISA test which detects antibodies reactive to the receptor binding domain (RBD) and the spike protein of the novel SARS-CoV-2. The assay is performed on 96-well plates coated with either SARS-CoV-2 recombinant RBD or spike proteins. The test is divided into two stages, a qualitative screening assay against RBD and a quantitative assay against the full-length spike protein. The test uses pooled high titer serum as a reference standard. Negative pre-COVID-19 and positive post-COVID-19, PCR-confirmed specimens were incorporated in each ELISA test run, and the assays were performed independently at two different locations. The Mount Sinai COVID-19 serology performed with high sensitivity and specificity, 92.5% (95% CI: 0.785 – 0.980) and 100% (CI: 0.939 – 1.000) respectively. Between-run precision was assessed with a single run repeated over 22 days; and within-run precision was assessed with 10 replicates per day over 22 days. Both were within reported acceptance criteria (CV ≤20%). This population-based study reveals the applicability and reliability of this novel orthogonal COVID-19 serology test for the detection and quantitation of antibodies against SARS-CoV-2, allowing a broad set of clinical applications, including the broad evaluation of SARS-CoV-2 seroprevalence and antibody profiling in different population subsets.Funding: This work was partially supported by the JPB foundation, the Open Philanthropy Project (#2020-215611) and other philanthropic donations.Declaration of Interests: Mount Sinai has licensed serological assays to commercial entities and has filed for patent protection for serological assays. The Icahn School of Medicine at Mount Sinai has filed patent applications relating to the COVID-19 serological assay (“Serology Assay”) and NDV-based SARS-CoV-2 vaccines which list Florian Krammer (“Serology Assay”, vaccines), Daniel Stadlbauer (“Serology Assay”), Damodara Rao Mendu (“Serology Assay”), and Carlos Cordon-Cardo (“Serology Assay”) as co-inventors. The foundational “Serology Assay” intellectual property (IP) was licensed by the Icahn School of Medicine at Mount Sinai to commercial entities including Kantaro Biosciences, a company in which Mount Sinai has a financial interest. Florian Krammer consulted for Merck, Curevac, and Pfizer in the past (before 2020) and is currently consulting for Pfizer, Seqirus, and Avimex. The Krammer laboratory is collaborating with Pfizer on animal models of SARS-CoV-2.Patient Informed Consent Statement: Informed consent was obtained from all individuals included in this study.