Assessment of Antibody Dynamics and Neutralizing Activity Using Serological Assay After SARS-COV-2 Infection and Vaccination
Toshihiro Takahashi, Tomohiko Ai, Kaori Saito, Shuko Nojiri, Maika Takahashi, Gene Igawa, Takamasa Yamamoto, Abdullah Khasawneh, Faith Jessica Paran, Satomi Takei, Yuki Horiuchi, Takayuki Kanno, Minoru Tobiume, Makoto Hiki, Mitsuru Wakita, Takashi Miida, Atsushi Okuzawa, Tadaki Suzuki, Kazuhisa Takahashi, Toshio Naito, Yoko Tabe
Abstract
The COVID-19 antibody test was developed to investigate the humoral immune response to SARS-CoV-2 infection. In this study, we examined whether S antibody titers measured using the anti-SARS-CoV-2 IgG II Quant assay (S-IgG), a high-throughput test method, reflects the neutralizing capacity acquired after SARS-CoV-2 infection or vaccination. To assess the antibody dynamics and neutralizing potency, we utilized a total of 457 serum samples from 253 individuals: 325 samples from 128 COVID-19 patients including 136 samples from 29 severe/critical cases (Group S), 155 samples from 71 mild/moderate cases (Group M), and 132 samples from 132 health care workers (HCWs) who have received 2 doses of the BNT162b2 vaccinations. The authentic virus neutralization assay, the surrogate virus neutralizing antibody test (sVNT), and the Anti-N SARS-CoV-2 IgG assay (N-IgG) have been performed along with the S-IgG. The S-IgG correlated well with the neutralizing activity detected by the authentic virus neutralization assay (0.8904. of Spearman’s rho value, p < 0.0001) and sVNT (0.9206. of Spearman’s rho value, p < 0.0001). However, 4 samples (2.3%) of S-IgG and 8 samples (4.5%) of sVNT were inconsistent with negative results for neutralizing activity of the authentic virus neutralization assay. The kinetics of the SARS-CoV-2 neutralizing antibodies and anti-S IgG in severe cases were faster than the mild cases. All the HCWs elicited anti-S IgG titer after the second vaccination. However, the HCWs with history of COVID-19 or positive N-IgG elicited higher anti-S IgG titers than those who did not have it previously. Furthermore, it is difficult to predict the risk of breakthrough infection from anti-S IgG or sVNT antibody titers in HCWs after the second vaccination.
Introduction
Coronavirus disease 2019 (COVID-19) is an infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which is currently an endemic worldwide [1]. Reverse transcription polymerase chain reaction (RT-PCR) is the gold standard test for the diagnosis of SARS-CoV-2 infection [2, 3]. However, false negative results of RT-PCR can be caused by suboptimal primer design, imperfect RNA extraction techniques, or lower volumes of applied virus [4]. Furthermore, because the RNA concentration of SARS-CoV-2 declines from 1–2 weeks after symptom onset, the detection ratio of RT-PCR is also decreased [5]. On the other hand, because seroconversion of SARS-CoV-2 occurs between one to two weeks after symptom onset, the serological antibody tests’ detection rate of specific antibody gradually increases [6]. Many of the commercial antibody tests can specifically detect immunoglobulins, such as IgG and IgM, binding against the nucleocapsid (N) protein and the receptor-binding domain (RBD) in the spike (S) protein of SARS-CoV-2 [7]. They are used as an adjunct to RT-PCR for COVID-19 diagnosis [8].
Material and methods
Ethics statement
This study complied with all relevant national regulations and institutional policies. It was conducted in accordance with the tenets of the Declaration of Helsinki and was approved by the Institutional Review Board (IRB) at Juntendo University Hospital (IRB # 20–036). The need for informed consent from individual patients was waived because all samples were de-identified in line with the Declaration of Helsinki. Informed consent was obtained from HCWs (IRB # M20-0089-M01).
Results
Correlations between anti-S IgG titer and neutralizing activities
We first compared the results of S-IgG to sVNT and then S-IgG to the neutralizing activity. As shown in Fig 1, the results of 176 samples demonstrated a strong linear correlation between S-IgG and sVNT. The relationship between S-IgG and the authentic virus neutralizing assay also showed a liner correlation. We further confirmed a linear correlation between sVNT and the authentic virus neutralizing assay. Comparison of S-IgG and the authentic virus neutralizing assay revealed a positive percent agreement (PPA) of 96.8% and a negative percent agreement (NPA) of 92.3%. Similarly, a comparison of sVNT and the authentic virus neutralizing assay revealed a PPA of 97.6% and a NPA of 84.6%. However, when compared to the authentic virus neutralization assay, 4 samples (2.3%) tested for S-IgG and 8 samples (4.5%) tested for sVNT were inconsistent with the negative results for the neutralizing activity of the comparative method. On the other hand, 4 samples (2.3%) tested for S-IgG and 3 samples (1.7%) tested for sVNT were inconsistent with the positive results for the neutralizing activity of the comparative method. Samples with a titer ≥ 20 in the authentic virus neutralizing assay were all positive in S-IgG and sVNT.
Discussion
In this study, we investigated the serological of antibody dynamics and neutralizing potency following SARS-CoV-2 infection and post vaccination by comparing three quantitative assays with different principles for detection of antibodies to SARS-CoV-2. S-IgG is correlated well with both sVNT and the authentic virus neutralization assay with high PPA and NPA. However, when the authentic virus neutralization assay was used as the comparative method, the results of 2.3% for S-IgG and 4.5% for sVNT were inconsistent with the negative results for neutralizing activity of the comparative method. Similar results have been reported in other studies [22].
Acknowledgments
The authors thank the Department of Research Support Utilizing Bioresource Bank, Juntendo University Graduate School of Medicine, for use of their facilities.
Citation: Takahashi T, Ai T, Saito K, Nojiri S, Takahashi M, Igawa G, et al. (2023) Assessment of antibody dynamics and neutralizing activity using serological assay after SARS-CoV-2 infection and vaccination. PLoS ONE 18(9): e0291670. https://doi.org/10.1371/journal.pone.0291670
Editor: Etsuro Ito, Waseda University: Waseda Daigaku, JAPAN
Received: December 29, 2022; Accepted: September 1, 2023; Published: September 19, 2023
Copyright: © 2023 Takahashi et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Data Availability: All relevant data are within the manuscript and the accompanying tables and figures.
Funding: This research was partially supported by Japan Agency for Medical Research and Development under Grant Number JP20fk0108472 to TN and by Japan Society for the Promotion of Science Grants-in Aid for Scientific Research under Grant Number 22K15675 to ST. The funders had no role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing interests: The reagent used in this study were partially provided by abbott, but the study was performed by scientifically proper methods without any bias. This does not alter our adherence to PLOS ONE policies on sharing data and materials.
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0291670#abstract0
