A peptide-based assay discriminates individual antibody response to SARS-CoV-2

Abstract

SARS-CoV-2 virus is responsible for the current worldwide coronavirus disease 2019 (COVID-19) pandemic, infecting millions of people and causing hundreds of thousands of deaths. Understanding the antibody response to SARS-CoV-2 is crucial for the development of vaccines, therapeutics and public health interventions. However, lack of consistency in methods used to monitor antibody response to SARS-CoV-2 leaves some uncertainty in our fine understanding of the human antibody response mounted following SARS-CoV-2 infection. We developed a peptide-based enzyme-linked immunosorbent assay (ELISA) by selecting 7 synthetic peptides from the spike, membrane, and nucleocapsid protein sequences of SARS-CoV-2, which effectively detects the antibody response mounted by all COVID-19 convalescent tested. Strikingly, the assay shows a profound difference in antibody response among individual subjects, which may have a significant impact on disease severity. Together, our results define an efficient and specific serological assay to consistently measure the antibody response following SARS-CoV-2 infection, as well as help the design of vaccine and therapeuticals for prevention and treatment of COVID-19.

Keywords: Antibodies; Assay; COVID-19; ELISA; Peptides; SARS-Cov-2.

Figure 1

IgG immuno-reacting with the selected peptides at 15–30 days after the RT-qPCR positive detection in 24 COVID-19 convalescents. Results were scored on the basis of the signal/cutoff (S/C) ratio, where the cutoff (C) value (stripped bar) was determined from the mean of four pre-2019 sera plus 3 standard deviations. Samples with absorbance values corresponding to C ± 10% (dotted bars) were scored as uncertain. Data shown is representative of at least 50 independent experiments.

Figure 2

IgA immuno-reacting with the selected peptides at 15–30 days after the RT-qPCR positive detection in 20 COVID-19 convalescents. Results were scored as indicated in Figure 1. Data shown is representative of at least 50 independent experiments.

Supplementary Fig. 2

Selected convalescent sera were tested by ELISA in wells uncoated (w) or coated with the indicated peptide. At the time of the test, sera samples were added to the wells along with the soluble form of the coated peptide or an irrelevant peptide, both at concentration of 1 μg/ml.