PLoS ONE (Jan 2023)

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

DOI
https://doi.org/10.1371/journal.pone.0291670
Journal volume & issue
Vol. 18, no. 9
p. e0291670

Abstract

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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.