PLoS ONE (Jan 2023)

Anti-spike protein to determine SARS-CoV-2 antibody levels: Is there a specific threshold conferring protection in immunocompromised patients?

  • Philippe Halfon,
  • Sylvie Jordana,
  • Stéphane Blachier,
  • Philippe Cartlamy,
  • Laurent Kbaier,
  • Christina K Psomas,
  • Patrick Philibert,
  • Gilles Antoniotti,
  • Julie Allemand-Sourrieu,
  • Stanislas Rebaudet,
  • Guilhem Cavaille,
  • Chloé Stavris,
  • Frédérique Retornaz,
  • Laurent Chiche,
  • Guillaume Penaranda

DOI
https://doi.org/10.1371/journal.pone.0281257
Journal volume & issue
Vol. 18, no. 4
p. e0281257

Abstract

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BackgroundIdentifying a specific threshold level of SARS-CoV-2 antibodies that confers protection in immunocompromised patients has been very challenging. The aim was to assess the threshold of 264 binding antibody units (BAU)/ml using four different SARS-CoV-2 antibody assays (Abbott, Beckman, Roche, and Siemens) and to establish a new optimal threshold of protection for each of the four antibody assays.MethodsThis study was performed on data retrieved from 69 individuals, who received at least one dose of the Pfizer/BioNTech BNT162b2 or Moderna COVID-19 vaccine (Spikevax) at the Alphabio Laboratory in Marseille, France (European Hospital, Alphabio-Biogroup). The results were compared to the percent inhibition calculated using a functional surrogate of a standardized virus neutralization test (Genscript).ResultsSamples from 69 patients were analyzed. For a reference cutoff of 264 BAU/ml, assays showed moderate to good overall concordance with Genscript: 87% concordance for Abbott, 78% for Beckman, 75% for Roche, and 88% for Siemens. Overall concordance increased consistently after applying new thresholds, i.e., 148 BAU/ml (Abbott), 48 (Beckman), 559 (Roche), and 270 (Siemens).ConclusionWe suggest specific adjusted thresholds (BAU/ml) for the four commercial antibody assays that are used to assess pre-exposure prophylaxis in immunocompromised patients.