Towards Quantitative and Standardized Serological and Neutralization Assays for COVID-19

• Published in: International journal of molecular sciences 2021-03, Vol.22 (5), p.2723
• Main Authors: Tian, Linhua, Elsheikh, Elzafir B, Patrone, Paul N, Kearsley, Anthony J, Gaigalas, Adolfas K, Inwood, Sarah, Lin-Gibson, Sheng, Esposito, Dominic, Wang, Lili
• Format: Article
• Language: English
• Subjects: Antibodies, Neutralizing - blood; Antibodies, Neutralizing - immunology; Antibodies, Viral - blood; Antibodies, Viral - immunology; COVID-19 - blood; COVID-19 - immunology; COVID-19 Serological Testing - methods; COVID-19 Serological Testing - standards; Cross Reactions; Flow Cytometry - methods; Fluorescence; Humans; IgG; IgM; Immunoglobulin G - blood; Immunoglobulin G - immunology; Immunoglobulin M - blood; Immunoglobulin M - immunology; Microspheres; Neutralization Tests - methods; Neutralization Tests - standards; quantitative serology assays; RBD; Receptors, Virus - chemistry; Receptors, Virus - immunology; SARS-CoV-2 - immunology; SARS-CoV-2 virus; spike; Spike Glycoprotein, Coronavirus - chemistry; Spike Glycoprotein, Coronavirus - immunology
• ISSN: 1422-0067; 1661-6596; 1422-0067
• DOI: 10.3390/ijms22052723

Quantitative and robust serology assays are critical measurements underpinning global COVID-19 response to diagnostic, surveillance, and vaccine development. Here, we report a proof-of-concept approach for the development of quantitative, multiplexed flow cytometry-based serological and neutralization assays. The serology assays test the IgG and IgM against both the full-length spike antigens and the receptor binding domain (RBD) of the spike antigen. Benchmarking against an RBD-specific SARS-CoV IgG reference standard, the anti-SARS-CoV-2 RBD antibody titer was quantified in the range of 37.6 µg/mL to 31.0 ng/mL. The quantitative assays are highly specific with no correlative cross-reactivity with the spike proteins of MERS, SARS1, OC43 and HKU1 viruses. We further demonstrated good correlation between anti-RBD antibody titers and neutralizing antibody titers. The suite of serology and neutralization assays help to improve measurement confidence and are complementary and foundational for clinical and epidemiologic studies.