An Assessment of Serological Assays for SARS-CoV-2 as Surrogates for Authentic Virus Neutralization.

Nicholas Wohlgemuth,Kendall Whitt,Sean Cherry,Chun-Yang Lin,Ashleigh Gowen,Florian Krammer,Tomi Mori,Michael A Whitt,Pamela Freiden,E Kaitlynn Allen,Li Tang,Jeremie H Estepp,Joshua Wolf,Paul G Thomas,Maureen A Mcgargill,Ericka Kirkpatrick Roubidoux,Diego R Hijano,Aditya H Gaur,Hana Hakim,St Jude Investigative Team ,Kim Allison ,Stacey Schultz‐Cherry

doi:10.1128/spectrum.01059-21

Abstract

ABSTRACTSevere 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. Diagnostic tools and serological assays are critical for controlling the outbreak, especially assays designed to quantitate neutralizing antibody levels, considered the best correlate of protection. As vaccines become increasingly available, it is important to identify reliable methods for measuring neutralizing antibody responses that correlate with authentic virus neutralization but can be performed outside 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. Here, we characterized three enzyme-linked immunosorbent assays (ELISAs) and three pseudotyped vesicular stomatitis virus (VSV) 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 green fluorescent protein (GFP)-expressing pseudotyped virus neutralization, and then the ELISAs.IMPORTANCE The ongoing COVID-19 pandemic is caused by infection with severe acute respiratory syndrome virus 2 (SARS-CoV-2). Prior infection or vaccination can be detected by the presence of antibodies in the blood. Antibodies in the blood are also considered to be protective against future infections from the same virus. The “gold standard” assay for detecting protective antibodies against SARS-CoV-2 is neutralization of authentic SARS-CoV-2 virus. However, this assay can only be performed under highly restrictive biocontainment conditions. We therefore characterized six antibody-detecting assays for their correlation with authentic virus neutralization. The significance of our research is in outlining the advantages and disadvantages of the different assays and identifying the optimal surrogate assay for authentic virus neutralization. This will allow for more accurate assessments of protective immunity against SARS-CoV-2 following infection and vaccination.

Highlights

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
One disadvantage of the pseudotyped virus neutralization assay is the pseudotyped viruses lack all but the spike protein from SARS-CoV-2, meaning they can only be neutralized by spike-specific antibodies, and the organization of proteins may not be representative of authentic virus particles
SARS-CoV-2 antibody titers in 39 plasma samples from 34 individuals: 10 samples were taken from PCR-negative individuals, and 29 samples were taken an average of 36 days following a positive PCR test

Summary

Introduction

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. The most accurate assays for predicting authentic virus neutralization were luciferase- and secreted embryonic alkaline phosphatase (SEAP)-expressing pseudotyped virus neutralizations, followed by green fluorescent protein (GFP)-expressing pseudotyped virus neutralization, and the ELISAs. IMPORTANCE The ongoing COVID-19 pandemic is caused by infection with severe acute respiratory syndrome virus 2 (SARS-CoV-2). The significance of our research is in outlining the advantages and disadvantages of the different assays and identifying the optimal surrogate assay for authentic virus neutralization This will allow for more accurate assessments of protective immunity against SARS-CoV-2 following infection and vaccination. Authentic virus neutralization is considered the “gold standard” for detecting protective antibody responses, but for SARS-CoV-2, it can only be performed in biosafety level 3 (BSL3) laboratories [8,9,10,11]. The most predictive assay was green fluorescent protein (GFP)-expressing pseudotyped virus neutralization, followed by the ELISAs

Methods

Results

Conclusion