Validation of a SARS-CoV-2 surrogate neutralization test detecting neutralizing antibodies against the major variants of concern

SARS-CoV-2 infection and/or vaccination elicit a broad range of neutralizing antibody responses against the different variants of concern (VOC). We established a new variant-adapted surrogate neutralization test (sVNT) and assessed the neutralization activity against the ancestral B.1 (WT) as well as VOC Delta, Omicron BA.1, BA.2 and BA.5. Performances were compared to the reference virus neutralization test (VNT) against the respective VOC using three different cohorts collected during the COVID waves. Pre-COVID samples confirmed 100% specificity of the sVNT. Correlation analyses showed moderate to strong correlation for Omicron sub-variants (Spearman’s r=0.7081 for BA.1, r=0.7205 for BA.2 and r=0.6042 for BA.5), and for WT (r=0.8458) and Delta-sVNT (r=0.8158), respectively. Comparison of the WT-sVNT performance with two CE-IVD commercial kits “Icosagen SARS-CoV-2 Neutralizing Antibody ELISA kit” and “Genscript cPass kit” revealed an overall good correlation ranging from 0.8673 to -0.8773 and a midway profile between both commercial kits with 87.76% sensitivity and 90.48% clinical specificity resulting in a Youden Index of 78.24. This midway trend was further confirmed on 100 double-vaccinated individuals. The BA.2-sVNT performance was similar to that of the Genscript test. Finally, sVNT ability to assess neutralizing antibodies against Omicron BA.5 was validated on a double-vaccinated cohort (n=100) and an Omicron-breakthrough infection cohort (n=91). Correlation analysis revealed a strong association (r=0.8583) between BA.5-sVNT and VNT. Accurate classification was confirmed by receiving operating characteristic (ROC) analysis reporting an area under the curve (AUC) of 0.9543. In conclusion, the sVNT allows for efficient prediction of immune protection against the various VOCs.严重急性呼吸综合征冠状病毒2型（Severe Acute Respiratory Syndrome Coronavirus 2, SARS-CoV-2）感染和/或疫苗接种可引发针对各类关切变异株（Variant of Concern, VOC）的广泛中和抗体应答。本研究建立了一种新型适配变异株的替代中和试验（surrogate neutralization test, sVNT），并针对原始株B.1（野生型WT）以及关切变异株Delta、Omicron BA.1、BA.2和BA.5评估了其中和活性。将该试验与采用新冠疫情各波流行期收集的三批独立队列的对应关切变异株参考病毒中和试验（virus neutralization test, VNT）进行性能对比。新冠感染前样本证实该sVNT的特异性达100%。相关性分析显示，Omicron亚变异株（BA.1的斯皮尔曼相关系数r=0.7081、BA.2为r=0.7205、BA.5为r=0.6042）以及野生型（r=0.8458）和Delta-sVNT（r=0.8158）均呈现中等至强相关性。将WT-sVNT的性能与两款获得CE-IVD认证的商用试剂盒——"Icosagen SARS-CoV-2中和抗体ELISA试剂盒"和"Genscript cPass试剂盒"进行对比，结果显示整体相关性良好，相关系数区间为0.8673至-0.8773；该试验性能介于两款商用试剂盒之间，其灵敏度为87.76%，临床特异性为90.48%，约登指数（Youden Index）为78.24。这一中间性能趋势在100名双剂疫苗接种者队列中得到进一步验证。BA.2-sVNT的性能与Genscript试剂盒相似。最后，针对Omicron BA.5的中和抗体检测能力在双剂疫苗接种队列（n=100）以及Omicron突破感染队列（n=91）中得到验证。相关性分析显示BA.5-sVNT与VNT之间存在强相关性（r=0.8583）。受试者工作特征曲线（Receiver Operating Characteristic, ROC）分析证实了其精准分类能力，曲线下面积（Area Under the Curve, AUC）为0.9543。综上，该sVNT可有效预测针对各类关切变异株的免疫保护效果。