Anti-SARS-CoV-2 antibodies persistence after natural infection: a repeated serosurvey in Northern Italy



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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Giorgio Fedele - Dipartimento di Malattie Infettive, Parassitarie ed Immunomediate, Isituto Superiore di Sanità

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

How to Cite
Fedele, G., Stefanelli, P., Bella, A., Fiore, S., Pancheri, S., Benedetti, E., … Ferro, A. (2021). Anti-SARS-CoV-2 antibodies persistence after natural infection: a repeated serosurvey in Northern Italy. Annali dell’Istituto Superiore Di Sanità, 57(4), 265–271. Retrieved from
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