Evaluation of commercially available fully automated and ELISA-based assays for detecting anti-SARS-CoV-2 neutralizing antibodies.

Rapid and accurate measurement of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV2)-specific neutralizing antibodies (nAbs) is paramount for monitoring immunity in infected and vaccinated subjects. The current gold standard relies on pseudovirus neutralization tests which require sophisticated skills and facilities. Alternatively, recent competitive immunoassays measuring anti-SARS-CoV-2 nAbs are proposed as a quick and commercially available surrogate virus neutralization test (sVNT). Here, we report the performance evaluation of three sVNTs, including two ELISA-based assays and an automated bead-based immunoassay for detecting nAbs against SARS-CoV-2. The performance of three sVNTs, including GenScript cPass, Dynamiker, and Mindray NTAb was assessed in samples collected from SARS-CoV-2 infected patients (n = 160), COVID-19 vaccinated individuals (n = 163), and pre-pandemic controls (n = 70). Samples were collected from infected patients and vaccinated individuals 2-24 weeks after symptoms onset or second dose administration. Correlation analysis with pseudovirus neutralization test (pVNT) and immunoassays detecting anti-SARS-CoV-2 binding antibodies was performed. Receiver operating characteristic (ROC) curve analysis was generated to assess the optimal threshold for detecting nAbs by each assay. All three sVNTs showed an excellent performance in terms of specificity (100%) and sensitivity (100%, 97.0%, and 97.1% for GenScript, Dynamiker, and Mindray, respectively) in samples collected from vaccinated subjects. GenScript demonstrated the strongest correlation with pVNT (r = 0.743, R2 = 0.552), followed by Mindray (r = 0.718, R2 = 0.515) and Dynamiker (r = 0.608, R2 = 0.369). Correlation with anti-SARS-CoV-2 binding antibodies was variable, but the strongest correlations were observed between anti-RBD IgG antibodies and Mindray (r = 0.952, R2 = 0.907). ROC curve analyses demonstrated excellent performance for all three sVNT assays in both groups, with an AUC ranging between 0.99 and 1.0 (p < 0.0001). Also, it was shown that the manufacturer's recommended cutoff values could be modified based on the tested cohort without significantly affecting the sVNT performance. The sVNT provides a rapid, low-cost, and scalable alternative to conventional neutralization assays for measuring and expanding nAbs testing across various research and clinical settings. Also, it could aid in evaluating actual protective immunity at the population level and assessing vaccine effectiveness to lay a foundation for boosters' requirements.

Evaluation of Natural and Vaccine-Induced Anti-SARS-CoV-2 Immunity: A Comparative Study between Different Groups of Volunteers.

(1) Background: The production of anti-SARS-CoV-2 antibodies should help minimize the severity of COVID-19 disease. Our focus was to investigate and compare different vaccination schedules, monitoring circulating S-RBD Ab (antibodies anti-Spike protein-Receptor Binding Domain) levels after administering two doses in naïve patients. Likewise, vaccine-stimulated immunity in naïve and previously infected patients was compared. (2) Methods: We included 392 patients. Sera were evaluated by Elecsys anti-SARS-CoV-2 S. Statistical analyses were conducted by MedCalc and JASP. (3) Results: In COVID-19 patients, the median value of Ab levels was 154 BAU/mL, stable up to 9 months after the infection. From the data observed in vaccinated patients, higher median values were recorded in COVID-19/Pfizer BioNTech (18913 BAU/mL) than in other groups (Pfizer BioNTech: 1841; ChadOx1 961; heterologous vaccination: 2687) BAU/mL. (4) Conclusions: In conclusion, a single booster dose given to previously infected patients raised an antibody response much higher than two doses given to naïve individuals and heterologous vaccination generated a robust persistent antibody response at high levels, steady up to three months after administration.

Validation of a quantitative lateral flow immunoassay (LFIA)-based point-of-care (POC) rapid test for SARS-CoV-2 neutralizing antibodies.

With the widespread use of coronavirus disease 2019 (COVID-19) vaccines, a rapid and reliable method to detect SARS-CoV-2 neutralizing antibodies (NAbs) is extremely important for monitoring vaccine effectiveness and immunity in the population. The purpose of this study was to evaluate the performance of the RapiRead™ reader and the TestNOW™ COVID-19 NAb rapid point-of-care (POC) test for quantitative measurement of antibodies against the spike protein receptor-binding domain of severe respiratory syndrome coronavirus 2 (SARS-CoV-2) in different biological matrices compared to chemiluminescence immunoassay (CLIA) methods. Ninety-four samples were collected and analyzed using a RapiRead™ reader and TestNOW™ COVID-19 NAb kits for detecting neutralizing antibodies, and then using two CLIAs. The data were compared statistically using the Kruskal-Wallis test for more than two groups or the Mann-Whitney test for two groups. Specificity and sensitivity were evaluated using a receiver operating characteristic (ROC) curve. Good correlation was observed between the rapid lateral flow immunoassay (LFIA) test system and both CLIA methods. RapiRead™ reader/TestNOW™ COVID-19 NAb vs. Maglumi: correlation coefficient (r) = 0.728 for all patients; r = 0.841 for vaccinated patients. RapiRead™ reader/TestNOW™ COVID-19 NAb vs. Mindray: r = 0.6394 in all patients; r = 0.8724 in vaccinated patients. The time stability of the POC serological test was also assessed considering two times of reading, 12 and 14 minutes. The data revealed no significant differences. The use of a RapiRead™ reader and TestNOW™ COVID-19 NAb assay is a quantitative, rapid, and valid method for detecting SARS-CoV-2 neutralizing antibodies and could be a useful tool for screening studies of SARS-CoV-2 infection and assessing the efficacy of vaccines in a non-laboratory context.

Antibody response to COVID-19 vaccine: A point of view that can help to optimize dose distribution.

The global strategy to control coronavirus disease is based on the availability of COVID-19 vaccines. More information about response to a single dose vaccine could help to better understand and optimize the management of the vaccine campaign. Workers from the University of Rome "Tor Vergata" and the University Hospital of University of Rome "Tor Vergata," were monitored during their vaccination program. Serum samples were collected between the first and second dose and after the second dose. University personnel has been vaccinated with two doses of Vaxzevria vaccine 12 weeks apart, while hospital personnel has been vaccinated with two doses of Comirnaty 3 weeks apart. IgG antibodies (Abs) against the Receptor Binding Domain (RBD) of the virus spike surface glycoprotein and neutralizing antibodies (NT) anti-SARS-CoV-2 that block the interaction between RBD and the surface receptor cellular angiotensin converting enzyme (ACE2) were measured using the CL-series Mindray chemiluminescent assays, respectively. Different amounts of antibodies produced after the two doses of vaccine were found. Individuals with a previous natural infection developed a higher Abs titer. Among the individuals with no history of past SARS-CoV-2 infection, 5% had an Abs level of the same order of magnitude of infected people, suggesting that they acquired the infection in an asymptomatic way. In such individuals, one dose of vaccine may be sufficient to obtain a protective immune response.

Clinical validation of a second generation anti-SARS-CoV-2 IgG and IgM automated chemiluminescent immunoassay.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has proven to be extremely contagious and has spread rapidly all over the world. A key aspect in limiting the virus diffusion is to ensure early and accurate diagnosis. Serological assays could be an alternative in increasing testing capabilities, particularly when used as part of an algorithmic approach combined with molecular analysis. The aim of this study was to evaluate the diagnostic accuracy of a second generation chemiluminescent automated immunoassay able to detect anti-SARS-CoV-2 immunoglobulin G (IgG) and immunoglobulin M (IgM) antibodies. Data are carried out on healthy subjects and other infectious diseases pre-pandemic sera, as controls, and on two different coronavirus disease 2019 hospitalized patient groups (early and late infection time). Data obtained have been analyzed in terms of precision, linearity, sensitivity and specificity. Specificities are: 100% for anti-SARS-CoV-2 IgG and 98% for anti-SARS-CoV-2 IgM, in all patient groups. Sensitivities are: 97%, 100%, and 98% for anti-SARS-CoV-2 IgG and 87%, 83%, and 86% for anti-SARS-CoV-2 IgM in the early infection, in the late infection and in the total patient group, respectively. The Mindray anti-SARS-CoV-2 IgG and IgM assays demonstrated higher sensitivity and specificity, indicating that IgG and IgM simultaneous detection is useful even in the early phases of infection.