COVID-19 antibodies in convalescent plasma evaluated by the C19-kodecyte (Anti-SARSCoV- 2 Red Cell) Assay

ABSTRACT

Background/Case Studies We had developed a simple and rapid red cell agglutination assay for serologic screening of antibodies to the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We evaluated this new C19-kodecyte assay in a cohort of convalescent patients with PCR-confirmed SARS-CoV-2 infection and compared its analytical performance with three established assays. Study Design/Methods: Red cells modified with peptides from SARS-CoV-2 spike protein using the Kode Technology were prepared.We tested plasma samples from 140 convalescent plasma donors and 125 healthy donors that had tested negative for anti-SARS-CoV-2 Total (Ortho). Plasma samples were stored at -30 °C before testing. Testing was performed using the column agglutination technology commonly employed for blood typing. The results were evaluated and compared with the results of a virus neutralization assay and two commercial chemiluminescent antibody tests Ortho anti-SARS-CoV-2 Total (IgG, IgM and IgA) assay and Ortho anti-SARS-CoV-2 IgG antibody assay. Results/Findings: The median time interval from the onset of symptoms and plasma donation was 94 days (range 33 - 331 days). Our simple and rapid C19-kodecyte assay detected SARS-CoV-2 antibodies with a specificity of 95.2% and sensitivity of 92.1%. Correlation analysis of measurement data among the different platforms showed a weak to moderate concordance. The Pearson correlation coefficient ranged between 0.21 and 0.28 for C19-kodecyte versus Ortho anti-SARS-CoV-2 Total and Ortho anti-SARS-CoV-2 IgG assays while it was 0.24 between C19-kodecyte and neutralizing titer. Agreements among C19-kodecyte versus Ortho anti-SARS-CoV-2 Total and Ortho anti-SARS-CoV-2 IgG assays were moderate 0.41 (0.09-0.73) and 0.41 (0.14-0.68), respectively. Conclusions: Sensitivity and specificity of the C19-kodecyte assay are within the estimated range of FDA issued EUA authorized serology tests (88% to 100% sensitivity and 95% to 100% specificity). The low correlation between C19-kodecyte versus Ortho anti-SARSCoV- 2 results and between C19-kodecyte versus neutralizing titer suggests that COVID-19 patients develop a broad antibody repertoire against multiple SARS-CoV-2 proteins and epitopes and different assays detect diverse antibody specificities. Our easily scalable approach using C19-kodecytes can be operated in blood typing laboratories worldwide using common routine setups. The availability of standard blood group serology techniques for SARS-CoV-2 antibody screening could vastly improve assay capacity. This would be particularly useful in developing countries, where dedicated virology and microbiology may be lacking the necessary turnaround capacity.