Dynamics of Neutralizing Antibody Responses Following Natural SARS-CoV-2 Infection and Correlation with Commercial Serologic Tests. A Reappraisal and Indirect Comparison with Vaccinated Subjects

Abstract

Neutralising antibodies (NAbs) represent the real source of protection against SARS-CoV-2 infections by preventing the virus from entering target cells. The gold standard in the detection of these antibodies is the plaque reduction neutralization test (PRNT). As these experiments must be done in a very secure environment, other techniques based on pseudoviruses: pseudovirus neutralization test (pVNT) or surrogate virus neutralization test (sVNT) have been developed. Binding assays, on the other hand, measure total antibodies or IgG, IgM, and IgA directed against one epitope of the SARS-CoV-2, independently of their neutralizing capacity. The aim of this study is to compare the performance of six commercial binding assays to the pVNT and sVNT. In this study, we used blood samples from a cohort of 62 RT-PCR confirmed COVID-19 patients. Based on the results of the neutralizing assays, adapted cut-offs for the binding assays were calculated. The use of these adapted cut-offs does not permit to improve the accuracy of the serological assays and we did not find an adapted cut-off able to improve the capacity of these tests to detect NAbs. For a part of the population, a longitudinal follow-up with at least two samples for the same patient was performed. From day 14 to day 291, more than 75% of the samples were positive for NAbs (n = 87/110, 79.1%). Interestingly, 6 months post symptoms onset, the majority of the samples (N = 44/52, 84.6%) were still positive for NAbs. This is in sharp contrast with the results we obtained 6 months post-vaccination in our cohort of healthcare workers who have received the two-dose regimens of BNT162b2. In this cohort of vaccinated subjects, 43% (n = 25/58) of the participants no longer exhibit NAbs activity 180 days after the administration of the first dose of BNT162b2.

Induction of SARS-CoV-2 neutralizing antibodies by CoronaVac and BNT162b2 vaccines in naïve and previously infected individuals

“…This suggests that the antibody response in previously uninfected individuals vaccinated with CoronaVac was significantly lower compared to individuals who have recovered from SARS-CoV-2 infection. 2 , 3 , 41 As shown, more severe individuals had higher antibody titres, which other studies have been associated with increased replication and disease burden. 24 Although lower titres are seen in Coronavac vaccinated individuals, as compared to natural infected individuals, this data indicates that immunization by this vaccine affords protection from COVID-19, as shown in recent vaccine effectiveness studies in Chile.…”

Evaluation of commercial Anti-SARS-CoV-2 neutralizing antibody assays in seropositive subjects

“…Most of the previous studies used the cPASS assay from GeneSript,showing the correlation of competitive immunoassay to live VNT, with good sensitivity and specificity compared to VNT ( 5 , 6 , 9 , 14 , 15 , 19 , 20 , 22 , 23 ). Only a few studies reported results with the TECO ( 15 , 20 ) or YHLO assays ( 7 , 8 , 21 ). Of note the study of Chan et al ( 21 ) found a diagnostic cutoff, with the YHLO assay, of 27,7 AU/ml, which is closed from ours of 30 AU/ml.…”

“…These competitive immunoassays, which can be conducted using qualitative immunochromatographic cassettes or quantitative automated or manual enzyme-linked immunosorbent assay (ELISA) platforms, allow rapid and easy processing of large numbers of samples in conventional serological laboratories. However, the performance of these newly developed commercial sVNT assays by comparison to classical serological assays detecting anti-RBD IgG and/or to the reference plaque reduction neutralization test 50% (PRNT 50 ) performed with live virus has been poorly evaluated up to now ( 6 , 7 , 8 , 9 ). Moreover, previous studies have evaluated the specificity using seronegative and/or prepandemic serum which do not inform if commercial sVNT can differentiate serum with or without neutralizing antibody in seropositive samples.…”

Anti-SARS-CoV-2 IgG and Neutralizing Antibody Levels in Patients with Past COVID-19 Infection: A Longitudinal Study

“…Another study revealed that most patients with COVID-19 at 6 months post-symptom onset were still positive for neutralizing antibodies (N = 44/52, 84.6%). 15 …”