Evaluation of commercial Anti-SARS-CoV-2 neutralizing antibody assays in seropositive subjects

• Published in: Journal of clinical virology Vol. 152; p. 105169
• Main Authors: Saker, Kahina, Pozzetto, Bruno, Escuret, Vanessa, Pitiot, Virginie, Massardier-Pilonchéry, Amélie, Mokdad, Bouchra, Langlois-Jacques, Carole, Rabilloud, Muriel, Alfaiate, Dulce, Guibert, Nicolas, Fassier, Jean-Baptiste, Bal, Antonin, Trouillet-Assant, Sophie, Trabaud, Mary-Anne
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.07.2022; Elsevier; The Authors. Published by Elsevier B.V
• Subjects: Antibodies, Neutralizing; Antibodies, Viral; Commercial tests; Competitive anti-RBD immunoassays; COVID-19 - diagnosis; Humans; Life Sciences; Neutralization Tests - methods; Neutralizing antibodies; SARS-CoV-2; Surrogate markers of protection; SARS-CoV-2; Commercial tests; Neutralizing antibodies; Competitive anti-RBD immunoassays; Surrogate markers of protection
• ISSN: 1386-6532; 1873-5967; 1873-5967
• DOI: 10.1016/j.jcv.2022.105169

•Performance of surrogate virus neutralization tests in seropositive samples.•Competitive immunoassays based on the interaction between spike protein and ACE2.•Comparison with plaque reduction neutralization test considered as gold standard.•Comparison with a classical serological assay detecting anti-RBD IgG.•Surrogate virus neutralization tests can't predict neutralization of variant. The virus neutralization test (VNT) is the reference for the assessment of the functional ability of neutralizing antibodies (NAb) to block SARS-CoV-2 entry into cells. New competitive immunoassays measuring antibodies preventing interaction between the spike protein and its cellular receptor are proposed as surrogate VNT (sVNT). We tested three commercial sVNT (a qualitative immunochromatographic test and two quantitative immunoassays named YHLO and TECO) together with a conventional anti-spike IgG assay (bioMérieux) in comparison with an in-house plaque reduction neutralization test (PRNT50) using the original 19A strain and different variants of concern (VOC), on a panel of 306 sera from naturally-infected or vaccinated patients. The qualitative test was rapidly discarded because of poor sensitivity and specificity. Areas under the curve of YHLO and TECO assays were, respectively, 85.83 and 84.07 (p-value >0.05) using a positivity threshold of 20 for PRNT50, and 95.63 and 90.35 (p-value =0.02) using a threshold of 80. However, the performances of YHLO and bioMérieux were very close for both thresholds, demonstrating the absence of added value of sVNT compared to a conventional assay for the evaluation of the presence of NAb in seropositive subjects. In addition, the PRNT50 assay showed a reduction of NAb titers towards different VOC in comparison to the 19A strain that could not be appreciated by the commercial tests. Despite the good correlation between the anti-spike antibody titer and the titer of NAb by PRNT50, our results highlight the difficulty to distinguish true NAb among the anti-RBD antibodies with commercial user-friendly immunoassays.