SARS-CoV-2 Serum Neutralization Assay: A Traditional Tool for a Brand-New Virus

Abstract

SARS-CoV-2 serum neutralization assay represents the gold standard for assessing antibody-mediated protection in naturally infected and vaccinated individuals. In the present study, 662 serum samples collected from February 2020 to January 2021 from acute and convalescent COVID-19 patients were tested to determine neutralizing antibody (NAb) titers using a microneutralization test (MNT) for live SARS-CoV-2. Moreover, anti-SARS-CoV-2 IgG, IgA, and IgM directed against different viral antigens were measured by high-throughput automated platforms. We observed higher levels of NAbs in elderly (>60 years old) individuals and in patients presenting acute respiratory distress syndrome. SARS-CoV-2 NAbs develop as soon as five days from symptom onset and, despite a decline after the second month, persist for over 11 months, showing variable dynamics. Through correlation and receiver operating characteristic (ROC) curve analysis, we set up a testing algorithm, suitable for the laboratory workload, by establishing an optimal cutoff value of anti-SARS-CoV-2 IgG for convalescent plasma donors to exclude from MNT samples foreseen to have low/negative NAb titers and ineligible for plasma donation. Overall, MNT, although cumbersome and not suitable for routine testing of large sample sizes, remains the reference tool for the assessment of antibody-mediated immunity after SARS-CoV-2 infection. Smart testing algorithms may optimize the laboratory workflow to monitor antibody-mediated protection in COVID-19 patients, plasma donors, and vaccinated individuals.

An automated chemiluminescent immunoassay (CLIA) detects SARS-CoV-2 neutralizing antibody levels in COVID-19 patients and vaccinees

“…The ROC curve analysis indicated AUC=0.901(p<0.001), sensitivity 87.4%, and specificity 78.1%. It was much better than that reported by Matusali et al (Matusali et al, 2021).…”

“…The protective capability of vaccine is another important subject concerned by people. Matusali et al reported that according to Italian guidelines, NAb titers ≥1:160 was a selection criterion for convalescent plasma for treating COVID-19 patients (Agenzia et al, 2021;Matusali et al, 2021;Peterhoff et al, 2021). It implies that people who got NAb titers ≥ 1:160 can be protected from SARS-CoV-2 infection.…”

Kinetics of SARS-CoV-2-Neutralising Antibodies of Residents of Long-Term Care Facilities

“…The June 2020 screening campaign evaluated the first epidemic outbreak, which affected our region between March and April 2020, thus allowing us to highlight the persistence of these antibodies over a period of at least a year, although pertinent serological follow-up could not be carried out for the entire period on more than eight residents due to the rest being vaccinated before M9. Similar timeframes have been described in the relevant scientific literature, with study follow-up ranging from 8 to 13 months (19)(20)(21). However, up until now, very few have focused on the elderly, who present with frailty, a high disease burden, and dependency.…”

Utility of Different Surrogate Enzyme-Linked Immunosorbent Assays (sELISAs) for Detection of SARS-CoV-2 Neutralizing Antibodies

“…In our study, we investigated the value of different SARS-CoV-2 surrogate enzyme-linked immunosorbent assays (sELISAs) for the detection of neutralization-competent antibodies compared to a cell culture-based method (PRNT) and a quantitative anti-RBD spike IgG assay. The PRNT is one of the preferred methods to test anti-SARS-CoV-2 neutralization activity, but it is no longer regarded as the only “gold standard” [ 21 , 22 ]. In fact, also microneutralization assays and pseudovirus tests are widely accepted [ 23 , 24 , 25 ].…”