Persistence of Neutralizing Antibodies to SARS-CoV-2 in First Wave Infected Individuals at Ten Months Post-Infection: The UnIRSA Cohort Study.

Gloria Griffante,Marisa Gariglio,Alessandra Vasile,Daniela Capello,Daniela Ferrante,Andrea Sarro,Marco Comba,Sara Bortoluzzi,Valeria Caneparo,Salvatore Esposito,Valentina Bettio,Tommaso Testa,Gianmarco Cotrupi,Marco De Andrea,Shikha Chandel,Cinzia Borgogna,Chiara Aleni

doi:10.3390/v13112270

Gloria Griffante, Marisa Gariglio + Show 15 more

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https://doi.org/10.3390/v13112270

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Abstract

Longitudinal mapping of antibody-based SARS-CoV-2 immunity is critical for public health control of the pandemic and vaccine development. We performed a longitudinal analysis of the antibody-based immune response in a cohort of 100 COVID-19 individuals who were infected during the first wave of infection in northern Italy. The SARS-CoV-2 humoral response was tested using the COVID-SeroIndex, Kantaro Quantitative SARS-CoV-2 IgG Antibody RUO Kit (R&D Systems, Bio-Techne, Minneapolis, USA) and pseudotype-based neutralizing antibody assay. Using sequential serum samples collected from 100 COVID-19 recovered individuals from northern Italy—mostly with mild disease—at 2 and 10 months after their first positive PCR test, we show that 93% of them seroconverted at 2 months, with a geometric mean (GeoMean) half-maximal neutralization titer (NT50) of 387.9. Among the 35 unvaccinated subjects retested at 10 months, 7 resulted seronegative, with an 80% drop in seropositivity, while 28 showed decreased anti-receptor binding domain (RBD) and anti-spike (S) IgG titers, with a GeoMean NT50 neutralization titer dropping to 163.5. As an NT50 > 100 is known to confer protection from SARS-CoV-2 re-infection, our data show that the neutralizing activity elicited by the natural infection has lasted for at least 10 months in a large fraction of subjects.

Highlights

From 21 May to 19 June 2020, 100 individuals (77 female, 23 male) who were infected by SARS-CoV-2 during the first wave of infection in Italy were enrolled in this study (Table 1)
All patients provided an initial blood sample defined as M2, which was taken at a median number of 51 days from the first positive PCR test
We have performed a longitudinal analysis of the serological responses to SARS-CoV-2 in 100 COVID-19 patients who were infected during the first wave of infection in Italy, of whom 74 were HCWs working at a hospital setting in northern Italy

Summary

Introduction

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is associated with the development of variable levels of antibodies (Abs) with neutralizing activity, which can protect against infection in animal models [1,2,3]. Given the short time SARS-CoV-2 has been studied, information on long-term antibody dynamics is still limited. In this regard, quantitative titer determination of virusneutralizing Abs (nAbs) is considered an excellent correlate of protection (CoP). Longitudinal studies assessing mid-term kinetics of SARS-CoV2 infection showed persistent neutralizing antibody responses for up to 8–10 months [8,9,10], leading to the possibility that nAbs to SARS-CoV-2 may represent a CoP from emerging

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