Asymptomatic and symptomatic SARS-CoV-2 infections elicit polyfunctional antibodies.

Dufloo, Jérémy; Grzelak, Ludivine; Staropoli, Isabelle; Madec, Yoann; Tondeur, Laura; Anna, François; Pelleau, Stéphane; Wiedemann, Aurélie; Planchais, Cyril; Buchrieser, Julian; Robinot, Rémy; Ungeheuer, Marie-Noelle; Mouquet, Hugo; Charneau, Pierre; White, Michael; Lévy, Yves; Hoen, Bruno; Fontanet, Arnaud; Schwartz, Olivier; Bruel, Timothée

A large proportion of SARS-CoV-2 infected individuals remains asymptomatic. Little is known about the extent and quality of their antiviral humoral response. Here, we analyze antibody functions in 52 asymptomatic infected individuals, 119 mild and 21 hospitalized COVID-19 patients. We measured anti-Spike IgG, IgA and IgM levels with the S-Flow assay and map IgG-targeted epitopes by Luminex. We also evaluated neutralization, complement deposition and Antibody-Dependent Cellular Cytotoxicity (ADCC) using replication-competent SARS-CoV-2 or reporter cell systems. We show that COVID-19 sera mediate complement deposition and kill infected cells by ADCC. Sera from asymptomatic individuals neutralize the virus, activate ADCC and trigger complement deposition. Antibody levels and functions are lower in asymptomatic individuals than in symptomatic cases. Antibody functions are correlated, regardless of disease severity. Longitudinal samplings show that antibody functions follow similar kinetics of induction and contraction. Overall, asymptomatic SARS-CoV-2 infection elicits polyfunctional antibodies neutralizing the virus and targeting infected cells.