Development and characterization of an indirect ELISA to detect SARS-CoV-2 spike protein-specific antibodies

J Immunol Methods. 2021 Mar;490:112958. doi: 10.1016/j.jim.2021.112958. Epub 2021 Jan 4.


The current Severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2) pandemic is a public health emergency of international concern. Sensitive and precise diagnostic tools are urgently needed. In this study, we developed a SARS-CoV-2 spike (S1) protein enzyme-linked immunosorbent assay (ELISA) to detect SARS-CoV-2-specific antibodies. The SARS-CoV-2 S1 ELISA was found to be specific [97.8% (95% CI, 96.7% - 98.5%)], reproducible and precise (intra-assay coefficient of variability (CV) 5.3%, inter-assay CV 7.9%). A standard curve and the interpolation of arbitrary ELISA units per milliliter served to reduce the variability between different tests and operators. Cross-reactivity to other human coronaviruses was addressed by using sera positive for MERS-CoV- and hCoV HKU1-specific antibodies. Monitoring antibody development in various samples of twenty-three and single samples of twenty-nine coronavirus disease 2019 (COVID-19) patients revealed seroconversion and neutralizing antibodies against authentic SARS-CoV-2 in all cases. The comparison of the SARS-CoV-2 (S1) ELISA with a commercially available assay showed a better sensitivity for the in-house ELISA. The results demonstrate a high reproducibility, specificity and sensitivity of the newly developed ELISA, which is suitable for the detection of SARS-CoV-2 S1 protein-specific antibody responses.

Keywords: COVID-19; Clinical diagnostic; ELISA; SARS-CoV-2; Spike protein.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antibodies, Neutralizing / blood
  • COVID-19 / diagnosis*
  • COVID-19 Serological Testing / methods*
  • Chlorocebus aethiops
  • Enzyme Assays
  • Enzyme-Linked Immunosorbent Assay
  • Epithelial Cells / metabolism*
  • Humans
  • Reproducibility of Results
  • SARS-CoV-2 / metabolism*
  • Sensitivity and Specificity
  • Seroconversion
  • Spike Glycoprotein, Coronavirus / genetics
  • Spike Glycoprotein, Coronavirus / immunology
  • Spike Glycoprotein, Coronavirus / metabolism*
  • Vero Cells


  • Antibodies, Neutralizing
  • Spike Glycoprotein, Coronavirus