Objectives To detect neutralizing antibody levels, a specific and sensitive automated chemiluminescent immunoassay (CLIA) was developed. This method can be used for SARS-COV-2 diagnosis, treatment and vaccine evaluation. Methods SARS-CoV-2 receptor-binding domain (RBD) and a stabilized version of the spike (S) ectodomain as antigens were detected by CLIA. Sera neutralizing antibody (NAb) titers and concentrations from 860 SARS-COV-2 vaccinees, 232 SARS-COV-2 convalescent individuals and 675 healthy individuals had been tested by micro neutralization test (MNT) and CLIA respectively. Mathematical methods were established to evaluate the relationship between two variables in different groups. Results Analyzing the relationship between NAb titers and concentration, the R-squares of Decision-making tree was 0.870 and that of Progressive linear fitting was 0.821. The ROC curves indicated specificity (78.1%), sensitivity (87.4%), cutoff value (6.43 AU/mL) and borderline (5.79-7.07 AU/mL) of CLIA. 75.4% vaccinees were detected NAb positive, and 5.35% vaccinees got NAb protective capability. The half-life period of NAb in vaccinees was 10-11weeks. Conclusions With the described RBD-based CLIA protocol, the CLIA can be used to replace MNT in testing SARS-COV-2 NAb. The effectiveness, protectiveness and durability of vaccine can be evaluated effectively by mathmatical models. It is necessary for vaccinees to take NAb assay periodically.
An automated chemiluminescent immunoassay (CLIA) detects SARS-CoV-2 Neutralizing antibody levels in COVID-19 patients and vaccinees