Heterogeneous antibodies against SARS-CoV-2 spike receptor binding domain and nucleocapsid with implications for COVID-19 immunity

JCI Insight. 2020 Sep 17;5(18):e142386. doi: 10.1172/jci.insight.142386.


Evaluation of potential immunity against the novel severe acute respiratory syndrome (SARS) coronavirus that emerged in 2019 (SARS-CoV-2) is essential for health, as well as social and economic recovery. Generation of antibody response to SARS-CoV-2 (seroconversion) may inform on acquired immunity from prior exposure, and antibodies against the SARS-CoV-2 spike protein receptor binding domain (S-RBD) are speculated to neutralize virus infection. Some serology assays rely solely on SARS-CoV-2 nucleocapsid protein (N-protein) as the antibody detection antigen; however, whether such immune responses correlate with S-RBD response and COVID-19 immunity remains unknown. Here, we generated a quantitative serological ELISA using recombinant S-RBD and N-protein for the detection of circulating antibodies in 138 serial serum samples from 30 reverse transcription PCR-confirmed, SARS-CoV-2-hospitalized patients, as well as 464 healthy and non-COVID-19 serum samples that were collected between June 2017 and June 2020. Quantitative detection of IgG antibodies against the 2 different viral proteins showed a moderate correlation. Antibodies against N-protein were detected at a rate of 3.6% in healthy and non-COVID-19 sera collected during the pandemic in 2020, whereas 1.9% of these sera were positive for S-RBD. Approximately 86% of individuals positive for S-RBD-binding antibodies exhibited neutralizing capacity, but only 74% of N-protein-positive individuals exhibited neutralizing capacity. Collectively, our studies show that detection of N-protein-binding antibodies does not always correlate with presence of S-RBD-neutralizing antibodies and caution against the extensive use of N-protein-based serology testing for determination of potential COVID-19 immunity.

Keywords: Adaptive immunity; COVID-19; Immunology.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptive Immunity / immunology
  • Antibodies, Neutralizing* / analysis
  • Antibodies, Neutralizing* / immunology
  • Antibodies, Viral* / analysis
  • Antibodies, Viral* / blood
  • Betacoronavirus / isolation & purification
  • Betacoronavirus / physiology*
  • Clinical Laboratory Techniques / methods
  • Coronavirus Infections* / diagnosis
  • Coronavirus Infections* / immunology
  • Coronavirus Infections* / therapy
  • Coronavirus Infections* / virology
  • Female
  • Humans
  • Male
  • Middle Aged
  • Nucleocapsid / immunology*
  • Outcome Assessment, Health Care
  • Pandemics*
  • Pneumonia, Viral* / immunology
  • Pneumonia, Viral* / therapy
  • Pneumonia, Viral* / virology
  • Protein Binding
  • Sensitivity and Specificity
  • Seroconversion
  • Serologic Tests / methods
  • Spike Glycoprotein, Coronavirus / immunology*


  • Antibodies, Neutralizing
  • Antibodies, Viral
  • Spike Glycoprotein, Coronavirus
  • spike protein, SARS-CoV-2

Supplementary concepts

  • COVID-19
  • COVID-19 diagnostic testing
  • severe acute respiratory syndrome coronavirus 2