Choosing the right tool for the job: A comprehensive assessment of serological assays for SARS-CoV-2 as surrogates for authentic virus neutralization

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged in late 2019 and has since caused a global pandemic resulting in millions of cases and deaths 1-4 . Diagnostic tools and serological assays are critical for controlling the outbreak 5-7 , especially assays designed to quantitate neutralizing antibody levels, considered the best correlate of protection 8-11 . As vaccines become increasingly available 12 , it is important to identify reliable methods for measuring neutralizing antibody responses that correlate with authentic virus neutralization but can be performed outside of biosafety level 3 (BSL3) laboratories. While many neutralizing assays using pseudotyped virus have been developed, there have been few studies comparing the different assays to each other as surrogates for authentic virus neutralization 9,10,13,14 . Here we characterized three enzyme-linked immunosorbent assays (ELISAs) and three pseudotyped VSV virus neutralization assays and assessed their concordance with authentic virus neutralization. The most accurate assays for predicting authentic virus neutralization were luciferase and secreted embryonic alkaline phosphatase (SEAP) expressing pseudotyped virus neutralizations, followed by GFP expressing pseudotyped virus neutralization, and then the ELISAs.