Plasma From Recovered COVID-19 Patients Inhibits Spike Protein Binding to ACE2 in a Microsphere-Based Inhibition Assay

J Infect Dis. 2020 Nov 13;222(12):1965-1973. doi: 10.1093/infdis/jiaa508.


We present a microsphere-based flow cytometry assay that quantifies the ability of plasma to inhibit the binding of spike protein to angiotensin-converting enzyme 2. Plasma from 22 patients who had recovered from mild coronavirus disease 2019 (COVID-19) and expressed anti-spike protein trimer immunoglobulin G inhibited angiotensin-converting enzyme 2-spike protein binding to a greater degree than controls. The degree of inhibition was correlated with anti-spike protein immunoglobulin G levels, neutralizing titers in a pseudotyped lentiviral assay, and the presence of fever during illness. This inhibition assay may be broadly useful to quantify the functional antibody response of patients recovered from COVID-19 or vaccine recipients in a cell-free assay system.

Keywords: ACE2; COVID-19; SARS-COV-2; Spike protein; binding inhibition; neutralization; serology.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Angiotensin-Converting Enzyme 2 / metabolism*
  • Antibodies, Neutralizing / immunology*
  • Antibodies, Viral / immunology*
  • Binding Sites
  • COVID-19 / immunology*
  • Female
  • HEK293 Cells
  • Humans
  • Male
  • Microspheres
  • Middle Aged
  • Plasma / immunology
  • Protein Binding
  • SARS-CoV-2 / immunology
  • Serologic Tests / methods*
  • Spike Glycoprotein, Coronavirus / immunology*
  • Young Adult


  • Antibodies, Neutralizing
  • Antibodies, Viral
  • Spike Glycoprotein, Coronavirus
  • spike protein, SARS-CoV-2
  • ACE2 protein, human
  • Angiotensin-Converting Enzyme 2