PLoS ONE (Jan 2021)

Early detection of neutralizing antibodies against SARS-CoV-2 in COVID-19 patients in Thailand.

  • Opass Putcharoen,
  • Supaporn Wacharapluesadee,
  • Wan Ni Chia,
  • Leilani Paitoonpong,
  • Chee Wah Tan,
  • Gompol Suwanpimolkul,
  • Watsamon Jantarabenjakul,
  • Chanida Ruchisrisarod,
  • Phanni Wanthong,
  • Jiratchaya Sophonphan,
  • Pajaree Chariyavilaskul,
  • Lin-Fa Wang,
  • Thiravat Hemachudha

DOI
https://doi.org/10.1371/journal.pone.0246864
Journal volume & issue
Vol. 16, no. 2
p. e0246864

Abstract

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BackgroundThe presence of neutralizing antibodies (NAbs) is an indicator of protective immunity for most viral infections. A newly developed surrogate viral neutralization assay (sVNT) offers the ability to detect total receptor binding domain-targeting NAbs in an isotype-independent manner, increasing the test sensitivity. Thus, specimens with low IgM/ IgG antibody levels showed strong neutralization activity in sVNT.MethodsThis study aimed to measure the %inhibition of NAbs measured by sVNT in PCR-confirmed COVID-19 patients. The sensitivity of sVNT for the diagnosis of SARS-CoV-2 infection and its kinetics were determined.ResultsNinety-seven patients with PCR-confirmed SARS-CoV-2 infection were included in this study. Majority of the patients were 21-40 years old (67%) and 63% had mild symptoms. The sensitivity of sVNT for the diagnosis of SARS-CoV-2 infection was 99% (95% confidence interval (CI) 94.4-100%) and the specificity was 100% (95% CI 98.3-100%). The negative predictive value of sVNT from the samples collected before and after 7 days of symptom onset was 99.5% (95% CI 97.4-100%) and 100% (95% CI 93.8-100%), respectively. The level of inhibition at days 8-14 were significantly higher than days 0-7 (pConclusionThe sVNT is a practical and robust serological test for SARS-CoV-2 infection and does not require specialized biosafety containment. It can be used clinically to aid diagnosis in both early and late infection especially in cases when the real-time RT-PCR results in weakly negative or weakly positive, and to determine the protective immune response from SARS-CoV-2 infection in patients.