Laboratoire de Virologie, Institut des Agents Infectieux, Laboratoire associé au Centre National de Référence des virus des infections respiratoires, Hospices Civils de Lyon, IAI, Centre de Biologie Nord, Groupement Hospitalier Nord, F-69317, Lyon Cedex 04, France.
CIRI- International Center of Research in Infectiology, INSERM U1111, CNRS UMR5308, ENS Lyon, Claude Bernard Lyon 1 University, F-69008, Lyon, France.
J Clin Virol. 2022 Jul;152:105169. doi: 10.1016/j.jcv.2022.105169. Epub 2022 Apr 27.
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 (PRNT) 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 PRNT, 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 PRNT 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 PRNT, our results highlight the difficulty to distinguish true NAb among the anti-RBD antibodies with commercial user-friendly immunoassays.
病毒中和试验（VNT）是评估中和抗体（NAb）阻断 SARS-CoV-2 进入细胞能力的参考指标。新的竞争免疫测定法用于测量阻止刺突蛋白与其细胞受体相互作用的抗体，被提议作为替代 VNT（sVNT）。我们使用来自自然感染或接种过疫苗的患者的 306 份血清样本，将三种商业 sVNT（一种定性免疫层析试验和两种定量免疫测定，分别命名为 YHLO 和 TECO）与传统的抗刺突 IgG 测定（bioMérieux）与内部的蚀斑减少中和试验（PRNT）进行比较，该试验使用了原始的 19A 株和不同的关注变体（VOC）。定性试验由于灵敏度和特异性差而迅速被淘汰。当 PRNT 的阳性阈值为 20 时，YHLO 和 TECO 测定的曲线下面积分别为 85.83 和 84.07（p 值>0.05），当阈值为 80 时，面积分别为 95.63 和 90.35（p 值=0.02）。然而，对于这两个阈值，YHLO 和 bioMérieux 的性能非常接近，表明与传统测定相比，sVNT 对于评估血清阳性个体中 NAb 的存在没有额外的价值。此外，与 19A 株相比，PRNT 试验显示针对不同 VOC 的 NAb 滴度降低，而商业测试无法评估这一点。尽管抗刺突抗体滴度与 PRNT 测定的 NAb 滴度之间存在良好的相关性，但我们的结果突出表明，使用商业易用性免疫测定法很难在抗 RBD 抗体中区分真正的 NAb。
