Neutralization of SARS-CoV-2 with IgG from COVID-19-convalescent plasma

Sci Rep. 2021 Mar 10;11(1):5563. doi: 10.1038/s41598-021-84733-5.


While there are various attempts to administer COVID-19-convalescent plasmas to SARS-CoV-2-infected patients, neither appropriate approach nor clinical utility has been established. We examined the presence and temporal changes of the neutralizing activity of IgG fractions from 43 COVID-19-convalescent plasmas using cell-based assays with multiple endpoints. IgG fractions from 27 cases (62.8%) had significant neutralizing activity and moderately to potently inhibited SARS-CoV-2 infection in cell-based assays; however, no detectable neutralizing activity was found in 16 cases (37.2%). Approximately half of the patients (~ 41%), who had significant neutralizing activity, lost the neutralization activity within ~ 1 month. Despite the rapid decline of neutralizing activity in plasmas, good amounts of SARS-CoV-2-S1-binding antibodies were persistently seen. The longer exposure of COVID-19 patients to greater amounts of SARS-CoV-2 elicits potent immune response to SARS-CoV-2, producing greater neutralization activity and SARS-CoV-2-S1-binding antibody amounts. The dilution of highly-neutralizing plasmas with poorly-neutralizing plasmas relatively readily reduced neutralizing activity. The presence of good amounts of SARS-CoV-2-S1-binding antibodies does not serve as a surrogate ensuring the presence of good neutralizing activity. In selecting good COVID-19-convalescent plasmas, quantification of neutralizing activity in each plasma sample before collection and use is required.

Publication types

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

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Antibodies, Neutralizing / immunology
  • Antibodies, Viral / immunology
  • COVID-19 / immunology*
  • COVID-19 / prevention & control
  • COVID-19 / therapy*
  • COVID-19 Serotherapy
  • Female
  • Humans
  • Immunization, Passive / methods
  • Immunoglobulin G / immunology*
  • Male
  • Middle Aged
  • Pandemics / prevention & control
  • Plasma / chemistry
  • Receptors, Virus / metabolism
  • SARS-CoV-2 / immunology
  • SARS-CoV-2 / pathogenicity


  • Antibodies, Neutralizing
  • Antibodies, Viral
  • Immunoglobulin G
  • Receptors, Virus