Development and Optimization of In-house ELISA for Detection of Human IgG Antibody to SARS-CoV-2 Full Length Spike Protein.

Sherif A El-Kafrawy,Sayed S Sohrab,Ahmed M Tolah,Tagreed L Alsubhi,Esam I Azhar,Ahmed M Hassan,Thamir A Alandijany,Norah A Othman,Arwa A Faizo

doi:10.3390/pathogens9100803

Abstract

The ongoing coronavirus disease 19 (COVID-19) pandemic, caused by the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), poses a threat to human health. Despite this, many affected countries are now in the process of gradual lifting of COVID-19 restrictions that were initially implemented in response to the pandemic. The success of the so-called “exit strategy” requires continued surveillance of virus circulation in the community and evaluation of the prevalence of protective immunity among population. Serology tests are valuable tools for these purposes. Herein, SARS-CoV-2 full-length spike (S) recombinant protein was utilized to develop and optimize an indirect enzyme-linked immunoassay (ELISA) that enables a reliable detection of virus-specific IgG antibody in human sera. Importantly, the performance of this assay was evaluated utilizing micro-neutralization (MN) assay as a reference test. Our developed ELISA offers 100% sensitivity, 98.4% specificity, 98.8% agreement, and high overall accuracy. Moreover, the optical density (OD) values of positive samples significantly correlated with their MN titers. The assay specifically detects human IgG antibodies directed against SARS-CoV-2, but not those to Middle East respiratory syndrome coronavirus (MERS-CoV) or human coronavirus HKU1 (HCoV-HKU1). The availability of this in-house ELISA protocol would be valuable for various diagnostic and epidemiological applications.

Highlights

The coronavirus disease 2019 (COVID-19) is a major public health issue caused by the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) [1]
Plates were initially coated with SARS-CoV-2 full length S (S1 + S2) extracellular domain with a polyhistidine tag (ECD-His) recombinant protein at a range of concentrations, serum samples were serially diluted, and the conjugate was used at different dilutions (1:1000 to 1:128,000) (Figure 1)
We have developed and optimized an in-house enzyme-linked immunoassay (ELISA) protocol based on the SARS-CoV-2 full-length S (S1 + S2) protein that enables the detection of viral-specific human IgG

Summary

Introduction

The coronavirus disease 2019 (COVID-19) is a major public health issue caused by the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) [1]. It was declared a pandemic by the. COVID-19 patients present varied clinical features that range from no or mild symptoms to severe life-threatening manifestations [3]. The main routes of viral transmission include respiratory droplets and direct contact with infected individuals [7,8]. It has been suggested that asymptomatic COVID-19 cases can be infectious to healthy persons, which may have significantly contributed to the massive spread of the infection [7]

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Conclusion