Development of Quantitative Spike and Nucleocapsid Protein-Based Enzyme-Linked Immunosorbent Assays (ELISAs) for Measurement of Antibodies against SARS-CoV-2

• Published in: The Journal of immunology (1950) 2022-05, Vol.208 (1_Supplement), p.125-125.23
• Main Authors: Liao, Wen-Chieh, Adame, Marissa, Webb, Jess, Nguyen, Dean, Ni, Jessie
• Format: Article
• Language: English
• ISSN: 0022-1767; 1550-6606
• DOI: 10.4049/jimmunol.208.Supp.125.23

In the COVID-19 pandemic, serological assays will have important public health and clinical uses to monitor and respond to the pandemic. Assays to detect and quantify virus-specific antibodies are important to complement the RNA-based tests, improve our understanding of the pathogenesis of COVID-19, and inform vaccine development. The majority of commercial assays for measuring IgG to SARS-CoV-2 have been limited by a lack of quantitative information about antiviral antibodies in standardized units. Here, we have developed and commercialized several fully validated, quantitative ELISA kits using purified receptor-binding domain (RBD) or full-length of Spike S1, or Nucleocapsid proteins developed in BioLegend as the capture reagents. The SARS-CoV-2 Spike Protein antibody ELISA kits have both LEGEND MAXTM and RAPID MAXTM formats and are optimized to mitigate matrix effects and avoid false-positive results, and have a readout in standardized units (mg/mL). We have applied these sensitive and specific SARS-CoV-2 Spike Protein antibody ELISAs in an employee cohort study to monitor antibody immune response after first and second doses of 2 mRNA SARS-CoV-2 vaccines – BNT162b2 (Pfizer-BioNTech) and mRNA-1273 (Moderna). We found that although all participants in this study are responsive to the first dose of immunization by both mRNA vaccines as evidenced by the elevation of anti-Spike S1 and RBD IgG levels above the pre-immunization baseline levels, more robust antibody responses to Spike S1 and RBD are observed after the second dose. In summary, our assays have good performance characteristics, have a quantitative readout in standardized units, and could be used by research and clinical laboratories that routinely use ELISA.