Neutralizing Antibody Responses in COVID-19 Convalescent Sera

TitleNeutralizing Antibody Responses in COVID-19 Convalescent Sera
Publication TypeJournal Article
Year of Publication2020
AuthorsLee, William T., Girardin Roxanne C., II Alan P. Dupuis, Kulas Karen E., Payne Anne F., Wong Susan J., Arinsburg Suzanne, Nguyen Freddy T., Mendu Damodara Rao, Firpo-Betancourt Adolfo, Jhang Jeffrey, Wajnberg Ania, Krammer Florian, Cordon-Cardo Carlos, Amler Sherlita, Montecalvo Marisa, Hutton Brad, Taylor Jill, and McDonough Kathleen A.
JournalThe Journal of Infectious Diseases
Date Published2020/10/26
Keywordsconvalescent plasma, COVID-19, neutralizing antibodies, SARS-CoV-2

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 ~93% (PRNT50) and ~54% (PRNT90). Sera with high SARS-CoV-2 antibody levels (>960 ELISA 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.