High Initial Titres of Anti-Spike Antibodies following SARS-CoV-2 Infection is Associated with Faster Decay Rates at Four Months Follow-Up

Abstract

Background Dynamics of humoral immune responses to SARS-CoV-2 antigens following infection suggests an initial decay of antibody followed by subsequent stabilization. We aim to understand the longitudinal humoral responses to SARS-CoV-2 nucleocapsid (N) protein and spike (S) protein and to evaluate their correlation to clinical symptoms among healthcare workers (HCW). Methods In this cross-sectional longitudinal cohort study done in two phases over four months, HCW underwent serial qualitative serology testing for anti-N antibody, quantitative MSH-ELISA to detect Receptor Binding Domain and full-length S reactive antibodies and completed online surveys about COVID-19 related symptoms and healthcare/community exposure. Results Anti-N antibody positivity was 27% and anti-S positivity was 28% in Phase 1. In Phase 2 anti-S titres were higher in symptomatic than in asymptomatic positive subjects in Phase 1. Marginally higher titers were seen in asymptomatic compared to the symptomatic positive subgroup in Phase 2. A positive correlation was noted between age, number and duration of symptoms, and Phase 1 anti-S antibody titre. A strong correlation was observed between Phase 1 titers and decay of anti-S antibody titres between the two phases. Significant correlation with rate of decay was also noted with fever, GI symptoms, and total number and duration of COVID-19 symptoms. Conclusions Higher initial anti-S antibody titres were associated with larger number and longer duration of symptoms as well as faster decay during the two time points.