Sensitivity in Detection of Antibodies to Nucleocapsid and Spike Proteins of Severe Acute Respiratory Syndrome Coronavirus 2 in Patients With Coronavirus Disease 2019

J Infect Dis. 2020 Jun 29;222(2):206-213. doi: 10.1093/infdis/jiaa273.


Background: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the cause of coronavirus disease 2019 (COVID-19), is associated with respiratory-related disease and death. Assays to detect virus-specific antibodies are important to understand the prevalence of infection and the course of the immune response.

Methods: Quantitative measurements of plasma or serum antibodies to the nucleocapsid and spike proteins were analyzed using luciferase immunoprecipitation system assays in 100 cross-sectional or longitudinal samples from patients with SARS-CoV-2 infection. A subset of samples was tested both with and without heat inactivation.

Results: At >14 days after symptom onset, antibodies against SARS-CoV-2 nucleocapsid protein showed 100% sensitivity and 100% specificity, whereas antibodies to spike protein were detected with 91% sensitivity and 100% specificity. Neither antibody levels nor the rate of seropositivity were significantly reduced by heat inactivation of samples. Analysis of daily samples from 6 patients with COVID-19 showed anti-nucleocapsid and spike protein antibodies appearing between days 8 and 14 after initial symptoms. Immunocompromised patients generally had a delayed antibody response to SARS-CoV-2, compared with immunocompetent patients.

Conclusions: Antibody to the nucleocapsid protein of SARS-CoV-2 is more sensitive than spike protein antibody for detecting early infection. Analyzing heat-inactivated samples with a luciferase immunoprecipitation system assay is a safe and sensitive method for detecting SARS-CoV-2 antibodies.

Keywords: COVID-19; SARS-CoV-2; coronavirus; serology.

Publication types

  • Research Support, N.I.H., Intramural

MeSH terms

  • Adult
  • Antibodies, Viral / blood*
  • Betacoronavirus / immunology*
  • COVID-19
  • COVID-19 Testing
  • Clinical Laboratory Techniques*
  • Coronavirus Infections / diagnosis
  • Coronavirus Infections / immunology*
  • Coronavirus Nucleocapsid Proteins
  • Female
  • Hot Temperature
  • Humans
  • Immunocompetence
  • Immunocompromised Host
  • Immunoprecipitation*
  • Luciferases
  • Male
  • Middle Aged
  • Nucleocapsid Proteins / immunology*
  • Pandemics
  • Phosphoproteins
  • Pneumonia, Viral / immunology*
  • Retrospective Studies
  • SARS-CoV-2
  • Sensitivity and Specificity
  • Spike Glycoprotein, Coronavirus / immunology*
  • Time Factors


  • Antibodies, Viral
  • Coronavirus Nucleocapsid Proteins
  • Nucleocapsid Proteins
  • Phosphoproteins
  • Spike Glycoprotein, Coronavirus
  • nucleocapsid phosphoprotein, SARS-CoV-2
  • spike protein, SARS-CoV-2
  • Luciferases