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.