Longitudinal Study of SARS-CoV-2 Antibody Characteristics Using Label-Free Immunoassays

Abstract Introduction/Objective Since the start of COVID-19 pandemic, much research has focused on kinetics and magnitude humoral immune response. With advantages monitoring real-time immunoreactions, label-free immunoassay (LFIA) is becoming a powerful tool in serology studies. We have developed LFIAs to measure SARS- CoV-2 antibody avidity neutralization activity cohort patients determine if they correlate with concentration. Serial serum samples collected from mild severe were measured out 8 months post-symptom onset durability neutralizing Methods/Case Report Based thin-film interferometry technology, we established IgG assay surrogate virus test (LF-sVNT). For measurement, sensing probes pre-coated receptor-binding domain (RBD) SARS-CoV-2 spike protein are applied containing antibodies. The measures binding strength between RBD under urea dissociation. LF-sVNT analyzes ability ACE2 after Results (if Case Study enter NA) indices titers (IC50) determined (n=246) (n=113). concentrations using fluorescent immunoassay. showed weak correlation no indices. Over time course up onset, presented similar trends: an initial rise, plateau then some cases gradual decline 40 days. indices, same cases, plateaued rise. Conclusion results demonstrated that LFIA could be used excellent solution determination characteristics. study found concentration titer declined over time, while index remained constant reaching plateau. can attributed reduction quantity rather than deterioration quality, as by avidity.