Abstract
Measuring SARS-CoV-2 neutralizing antibodies after vaccination or natural infection remains a priority in the ongoing COVID-19 pandemic to determine immunity, especially against newly emerging variants. The gold standard for assessing antibody-mediated immunity against SARS-CoV-2 are cell-based live virus neutralization assays. These assays usually take several days, thereby limiting test capacities and the availability of rapid results. In this study, therefore, we developed a faster live virus assay, which detects neutralizing antibodies through the early measurement of antibody-mediated intracellular virus reduction by SARS-CoV-2 qRT-PCR. In our assay, Vero E6 cells are infected with virus isolates preincubated with patient sera and controls. After 24 h, the intracellular viral load is determined by qRT-PCR using a standard curve to calculate percent neutralization. Utilizing COVID-19 convalescent-phase sera, we show that our novel assay generates results with high sensitivity and specificity as we detected antiviral activity for all tested convalescent-phase sera, but no antiviral activity in prepandemic sera. The assay showed a strong correlation with a conventional virus neutralization assay (r S = 0.8910), a receptor-binding domain ELISA (r S = 0.8485), and a surrogate neutralization assay (r S = 0.8373), proving that quantifying intracellular viral RNA can be used to measure seroneutralization. Our assay can be adapted easily to new variants, as demonstrated by our cross-neutralization experiments. This characteristic is key for rapidly determining immunity against newly emerging variants. Taken together, the novel assay presented here reduces turnaround time significantly while making use of a highly standardized and sensitive SARS-CoV-2 qRT-PCR method as a readout.
Keywords: COVID-19; SARS-CoV-2; cross-neutralization; neutralization assay; neutralizing antibodies; surrogate neutralization assay.
【저자키워드】 COVID-19, SARS-CoV-2, Neutralizing antibodies, Neutralization assay, cross-neutralization, Surrogate neutralization assay., 【초록키워드】 neutralizing antibody, vaccination, Immunity, Neutralizing antibodies, antibody, neutralization, COVID-19 pandemic, qRT-PCR, antiviral activity, virus, variants, ELISA, Viral, Receptor-binding domain, Sensitivity and specificity, Neutralization assay, Viral load, virus isolate, sera, cross-neutralization, Virus neutralization, gold, VERO E6 cells, Neutralizing, Viral RNA, Vero E6 cell, correlation, characteristic, natural infection, SARS-CoV-2 neutralizing antibodies, Live virus, SARS-CoV-2 neutralizing antibody, standard curve, Antibody-mediated immunity, Vero E6, determined by, reduction, gold standard, domain, priority, patient sera, neutralization assays, controls, SARS-CoV-2 qRT-PCR, tested, detect, significantly, generate, can be used, determine, faster, demonstrated, reduce, experiments, calculate, 【제목키워드】 qPCR, Rapid, development,