Flow cytometry detection of sustained humoral immune response (IgG\u2009+\u2009IgA) against native spike glycoprotein in asymptomatic/mild SARS-CoV-2 infection

Paula Piñero,Marisol Uribe Barrientos,Francisco M Marco De La Calle,Balbino Alarcón,Lydia Horndler,Fabián Tarín,Héctor Sarmiento

doi:10.1038/s41598-021-90054-4

Abstract

SARS-CoV-2 is the virus that causes the disease called COVID-19, which has caused the worst pandemic of the century. Both, to know the immunological status of general population and to evaluate the efficacy of the vaccination process that is taking place around the world, serological tests represent a key tool. Classic serological tests, based on colorimetric techniques, such as ELISA or CLIA, continue to be the most widely used option. However, a real improvement in results is still needed. We developed a highly sensitive and specific FCM assay that allows the detection of IgG and IgA antibodies, directed against the native and functional S-protein of SARS-CoV-2 exposed on the membrane of a transfected cell line, up to 8 months after infection.

Highlights

SARS-CoV-2 is a Baltimore class IV RNA virus that spreads through the respiratory tract and causes an infectious disease called COVID-191,2
SARS-CoV-2 infection promotes the generation of T and B cell responses, against the spike glycoprotein (S-protein) blocking its ability to bind to ACE-2 protein[4,5,6]
To further validate the specificity for S-protein of the signals generated by IgG and IgA antibodies, we studied the correlation between the median fluorescence intensity (MFI) corresponding to IgG or IgA bound to transfected cells and EGFR expression Supplementary Fig. 1

Summary

Introduction

SARS-CoV-2 is a Baltimore class IV RNA virus that spreads through the respiratory tract and causes an infectious disease called COVID-191,2. SARS-CoV-2 infection promotes the generation of T and B cell responses, against the spike glycoprotein (S-protein) blocking its ability to bind to ACE-2 protein[4,5,6]. It is still unknown whether the immune response leads to a prolonged protection against reinfection[6,7,8]. The Enzyme-Linked ImmunoSorbent Assay (ELISA) and chemiluminescence immunoassay (CLIA) have shown to detect seropositivity in the general population reaching good sensitivity and specificity[10,11,12] It has been noted the need for improved specificity and sensitivity. By contrast to other immunological techniques, FCM detects antibodies directed against the native and functional S-proteins, exposed on the membrane of a transfected cell line, allowing optimal conditions for improved sensitivity and s pecificity[14,15]

Methods

Results

Conclusion