Neutralizing Antibody Responses in COVID-19 Convalescent Sera

William T. Lee, Roxanne C. Girardin, Alan P. Dupuis, Karen E. Kulas, Anne F. Payne, Susan J. Wong, Suzanne Arinsburg, Freddy T. Nguyen, Damodara Rao Mendu, Adolfo Firpo-Betancourt, Jeffrey Jhang, Ania Wajnberg, Florian Krammer, Carlos Cordon-Cardo, Sherlita Amler, Marisa Montecalvo, Brad Hutton, Jill Taylor, Kathleen A. Mcdonough

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45 Scopus citations


Passive transfer of antibodies from COVID-19 convalescent patients is being used as an experimental treatment for eligible patients with SARS-CoV-2 infections. The United States Food and Drug Administration's (FDA) guidelines for convalescent plasma initially recommended target antibody titers of 160. We evaluated SARS-CoV-2 neutralizing antibodies in sera from recovered COVID-19 patients using plaque reduction neutralization tests (PRNT) at moderate (PRNT50) and high (PRNT90) stringency thresholds. We found that neutralizing activity significantly increased with time post symptom onset (PSO), reaching a peak at 31-35 days PSO. At this point, the number of sera having neutralizing titers of at least 160 was approximately 93% (PRNT50) and approximately 54% (PRNT90). Sera with high SARS-CoV-2 antibody levels (>960 enzyme-linked immunosorbent assay titers) showed maximal activity, but not all high-titer sera contained neutralizing antibody at FDA recommended levels, particularly at high stringency. These results underscore the value of serum characterization for neutralization activity.

Original languageEnglish
Pages (from-to)47-55
Number of pages9
JournalJournal of Infectious Diseases
Issue number1
StatePublished - 1 Jan 2021


  • COVID-19
  • SARS-CoV-2
  • convalescent plasma
  • neutralizing antibodies


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