Serological testing is a tool to predict protection against later infection. This potential heavily relies on antibody levels showing acceptable agreement with gold standard virus neutralization tests. The aim of our study was to investigate diagnostic value of the available serological tests in terms of predicting virus neutralizing activity of serum samples drawn 5–7 weeks after onset of symptoms from 101 donors with a history of COVID-19. Immune responses against Receptor Binding Domain (RBD), Spike1 and 2 proteins and Nucleocapsid antigens were measured by various ELISA tests. Neutralizing antibody activity in serum samples was assessed by a cell-based virus neutralization test. Spearman correlation coefficients between serological and neutralization results ranged from 0.41 to 0.91 indicating moderate to strong correlation between ELISA test results and virus neutralization. The sensitivity and specificity of ELISA tests in the prediction of neutralization were 35–100% and 35–90% respectively. No clear cut off levels can be established that would reliably indicate neutralization activity. For some tests, however, a value below which the sample is not expected to neutralize can be established. Our data suggests that several of the ELISA kits tested may be suitable for epidemiological surveys 1–2 months after the infection, estimating whether a person may have recently exposed to the virus. Sensitivities considerably superseding specificity at the cut-off values proposed by the manufacturers suggest greater potential in the identification of insufficient antibody responses than in confirming protection. Nevertheless, the former might be important in assessing response to vaccination and characterizing therapeutic plasma preparations. Highlights • SARS-CoV-2 antibody levels 5-7 weeks after the onset of COVID show moderate to strong correlation with virus neutralization. • Tests based on the use of S1, nucleocapsid or RBD antigens performed similarly in predicting antibody neutralization. • None of the examined serological tests could safely identify individuals protected against a later SARS-CoV-2 infection. • The products assessed might still provide important epidemiological information. • Serological tests might still have potential in screening donors for therapeutic plasma products or vaccinated individuals.
【저자키워드】 COVID-19, serological test, SARS-CoV-2, neutralization, Antibody Response, COVID-19, Coronavirus disease 2019, SARS-CoV-2, Severe acute respiratory syndrome coronavirus 2, Correlate of protection, ROC, Receiver Operating Characteristic, AUC, area under the curve, ECDC, European Centre for Disease Prevention and Control, NAbs, neutralizing antibodies, VNT, virus neutralization test, NC, Nucleocapsid, S1, Spike protein 1, S2, Spike protein 2, OD, optical density, 【초록키워드】 antibody, SARS-COV-2 infection, Infection, Test, virus, ELISA, Antigen, COVID, Protein, specificity, Neutralizing activity, SARS-CoV-2 antibody, Sensitivity and specificity, nucleocapsid, RBD, virus neutralization test, therapeutic, Virus neutralization, epidemiological survey, plasma, epidemiological, correlation, information, serological, moderate, predict, Antibody neutralization, Donor, gold standard, individual, diagnostic value, neutralization activity, cut-off value, vaccinated individuals, ELISA test, ELISA kit, serum sample, RBD antigen, neutralize, Spearman correlation coefficient, greater, tested, identify, performed, examined, onset of symptom, expected, responses against, were measured, ranged, cut off, response to vaccination, 【제목키워드】 anti-SARS-CoV-2, Virus neutralization, plasma, Donor,