Anti-SARS-CoV-2 antibodies persistence after natural infection: a repeated serosurvey in Northern Italy
Authors
Giorgio Fedele, Paola Stefanelli, Antonino Bella, Stefano Fiore, Serena Pancheri, Eleonora Benedetti, Concetta Fabiani, Pasqualina Leone, Paola Vacca, Ilaria Schiavoni, Arianna Neri, Anna Carannante, Maurizio Simmaco, Iolanda Santino, Maria Grazia Zuccali, Giancarlo Bizzarri, Rosa Magnoni, Pier Paolo Benetollo, Silvio Brusaferro, Giovanni Rezza, Antonio Ferro
Abstract
Introduction. To evaluate the decline of antibodies induced by SARS-CoV-2 infection, the individuals resident in 5 municipalities of the Autonomous Province of Trento, Northern Italy, who resulted IgG positive for anti-SARS-CoV-2 nucleocapsid (NC) in May 2020, were tested four months later.
Methods. Anti-SARS-CoV-2 NC antibodies were detected using the Abbott SARSCoV-2 IgG assay. Samples that gave a negative result were re-tested using the Liaison SARS-CoV-2 IgG assay to assess anti-spike (S) S1/S2 antibodies. The fifty-percent tissue culture infective dose (TCID50) neutralizing assay was performed on a subgroup of formerly positive sera. Statistical analysis was performed by STATA version 16.1 (STATA Corp., College Station, Texas, USA).
Results. Overall, 480 out of 1159 participants became seronegative for anti-NC IgG antibodies. Age above 70 years and cough were associated with persistent anti-NC IgG levels. Most anti-NC IgG negative sera were positive for anti-S IgG (77.9%). The neutralization assay showed high concordance with anti-S antibodies positivity.
Conclusion. In conclusion, a decline of anti-NC IgG values was recorded four months after the first evaluation. A high proportion of anti-NC seronegative individuals were positive for anti-spike IgG antibodies, which appear to persist longer and to better correlate with neutralization activity.
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