SARS-CoV-2 Serologic Assays Dependent on Dual-Antigen Binding Demonstrate Diverging Kinetics Relative to Other Antibody Detection Methods.

Background: Longitudinal studies assessing durability of the anti-SARS-CoV-2 humoral immune response have generated conflicting results. This has been proposed to be due to differences in patient populations, the lack of standardized methodologies, and the use of assays that measure distinct aspects of the humoral response.
Methods: SARS-CoV-2 antibodies were serially measured in sera from a cohort of 44 well-characterized convalescent plasma donors over 120 days post-COVID-19 symptom onset, utilizing eight assays, which varied according to antigen source, the detected antibody isotype, and the activity measured (i.e., binding, blocking, or neutralizing).
Results: While the majority of assays demonstrated a gradual decline in antibody titers over the course of 120 days, the two electrochemiluminescence immunoassay Roche assays (Roche Diagnostics Elecsys Anti-SARS-CoV-2 [Qualitative; Nucleocapsid-based] and Roche Diagnostics Elecsys Anti-SARS-CoV-2 S [Semi-Quantitative; Spike-based]), which utilize dual-antigen binding for antibody detection, demonstrated stable and/or increasing antibody titers over the study period.
Conclusion: This study is among the first to assess longitudinal, rather than cross-sectional SARS-CoV-2 antibody profiles among convalescent COVID-19 patients, primarily using commercially available serologic assays with Food and Drug Administration Emergency Use Authorization. We show that the SARS-CoV-2 antibody detection is dependent on the serologic method used, which has implications for future assay utilization and clinical value.