Comparison of two assays to detect IgG antibodies to the receptor binding domain of SARS‑CoV‑2 as a surrogate marker for assessing neutralizing antibodies in COVID-19 patients

Achala Kamaladasa,Banuri Gunasekara,Chandima Jeewandara,Deshni Jayathilaka,Ananda Wijewickrama,Dinuka Guruge,Ruwan Wijayamuni,T.K Tan,Graham S Ogg,Alain Townsend,Gathsaurie Neelika Malavige

doi:10.1016/j.ijid.2021.06.031

Abstract

BackgroundNeutralizing antibodies (NAbs) are important for protection against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) reinfection. In this study, two assays that are correlated with NAbs were compared: the haemagglutination test (HAT) and the surrogate virus neutralization test (sVNT). MethodsThe specificity of the HAT was compared with the sVNT, and the sensitivity and persistence of antibodies in patients with varying severity of illness was assessed in a cohort of 71 patients at 4–6 weeks and 13–16 weeks. The kinetics were assessed in the first, second, and third weeks in patients with varying severity of acute illness. ResultsThe specificity of the HAT was >99%, and sensitivity was similar to the sVNT. The levels of HAT were significantly and positively correlated with those of the sVNT (Spearman's r = 0.78, P < 0.0001). Patients with moderate and severe illness had higher HAT titres when compared to those with mild illness. Six of seven patients with severe illness had a titre of >1:640 during the second week of illness, whereas only five of 31 patients with a mild illness had a titre of >1:160 in the second week of illness. ConclusionsSince the HAT is a simple and very cheap assay to perform, it would be ideal to use as an indicator of NAbs in resource-poor settings.

Highlights

There are many antibody assays currently in use to determine IgG, IgM, and IgA specific to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus responsible for coronavirus disease 2019 (COVID-19) (Algaissi et al, 2020; Sun et al, 2020; Vogelzang et al, 2020)
With COVID-19 spreading at an exponential rate around the world, many assays have been developed to measure neutralizing antibodies (NAbs) that can be performed within a few hours in a BSL-2 facility (Tan et al, 2020; Townsend et al, 2020)
Since the majority of NAbs are directed at the receptor binding domain (RBD) (Kreer et al, 2020; Ni et al, 2020) and the level of antibodies detected by the haemagglutination test (HAT) correlates with the neutralising half maximal inhibitory concentration (IC50)(manuscript in preparation), this assay could be used as an inexpensive test to predict NAbs in research and community settings where high throughput assays are required (Townsend et al, 2020)

Summary

Introduction

There are many antibody assays currently in use to determine IgG, IgM, and IgA specific to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus responsible for coronavirus disease 2019 (COVID-19) (Algaissi et al, 2020; Sun et al, 2020; Vogelzang et al, 2020). With COVID-19 spreading at an exponential rate around the world, many assays have been developed to measure NAbs that can be performed within a few hours in a BSL-2 facility (Tan et al, 2020; Townsend et al, 2020) One such assay is the surrogate virus neutralization test (sVNT), which measures the percentage of inhibition of binding of the RBD of the spike protein to recombinant angiotensin-converting enzyme 2 (ACE2) (Tan et al, 2020). Two assays that are correlated with NAbs were compared: the haemagglutination test (HAT) and the surrogate virus neutralization test (sVNT)

Methods

Results

Conclusion