Dynamic Anti-Spike Protein Antibody Profiles in COVID-19 Patients.

Abstract Objectives This study intended to investigate the dynamics of anti-spike (S) IgG and IgM antibodies in COVID-19 patients. Methods Anti-S IgG/IgM were determined by a semi-quantitative fluorescence immunoassay in the plasma of COVID-19 patients at the manifestation and rehabilitation stages. The immunoreactivity to full-length S proteins,C-terminal domain (CTD) andN-terminal domain (NTD)of S1fragment were determined by an ELISA assay. Clinical properties at admission and discharge were collected simultaneously. Results The positive rates of anti-S IgG/IgM in COVID-19 patients were elevated after rehabilitation when compared to the in-patients. Anti-S IgG and IgM were not apparent until day 14 and day 10 respectively according to Simple Moving Average analysis with 5 days’ slide window deduction. More than 90% of the rehabilitation patients exhibited IgG and IgM responses targeting CTD-S1 fragments. There exhibited the decrease in peripheral total lymphocytes, CD4+ and CD8+ T cell counts in COVID-19 patients at admission and recovered after therehabilitation. Conclusions Anti-S IgG and IgM do not appear at the onset with the decrease in T cells, making early serological screening less significant. However, the presence of high IgG and IgM to S1-CTD in the recovered patients highlights humoral responses after SARS-CoV-2 infection, which might be associated with efficient immune protection in COVID-19 patients.