Assessment of antibody dynamics and neutralizing activity using serological assay after SARS-CoV-2 infection and vaccination

• Published in: PloS one Vol. 18; no. 9; p. e0291670
• Main Authors: Takahashi, Toshihiro, Ai, Tomohiko, Saito, Kaori, Nojiri, Shuko, Takahashi, Maika, Igawa, Gene, Yamamoto, Takamasa, Khasawneh, Abdullah, Paran, Faith Jessica, Takei, Satomi, Horiuchi, Yuki, Kanno, Takayuki, Tobiume, Minoru, Hiki, Makoto, Wakita, Mitsuru, Miida, Takashi, Okuzawa, Atsushi, Suzuki, Tadaki, Takahashi, Kazuhisa, Naito, Toshio, Tabe, Yoko
• Format: Journal Article
• Language: English
• Published: San Francisco Public Library of Science 19.09.2023; Public Library of Science (PLoS)
• Subjects: Antibodies; Assaying; Biology and life sciences; COVID-19; COVID-19 vaccines; Enzymes; Ethics; Evaluation; Health aspects; Health risks; Immune response; Immune response (humoral); Immunoassay; Immunoglobulin G; Infection; Infections; Infectious diseases; Medical personnel; Medical research; Medicine and health sciences; Medicine, Experimental; Neutralization; Neutralizing; Pneumonia; Prophylaxis; Proteins; Research and Analysis Methods; Serology; Severe acute respiratory syndrome coronavirus 2; Vaccination; Variance analysis; Viral antibodies; Viral diseases; Viruses; Japan; United States > US
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0291670

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. Our data shows that the use of anti-S IgG titers as direct quantitative markers of neutralizing capacity is limited. Thus, antibody tests should be carefully interpreted when used as serological markers for diagnosis, treatment, and prophylaxis of COVID-19.