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

Abstract

Quantitative and robust serology assays are critical measurements underpinning global COVID-19 response to diagnostic, surveillance, and vaccine development. Here we report 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.Funding: The work was conducted as part of official duty of employee withfederal funds from the National Institute of Standards and Technology.Conflict of Interest: The authors declare no competing interests.Ethical Approval: The study was approved by the institutional research protection office of NIST.