Clinical Correlates of Early IgG Response in Patients with Mild COVID-19

Abstract

Background: We determined the temporal pattern of early SARS-CoV-2 IgG response in patients with mild COVID-19, and sought to identify predictive clinical and laboratory features. Methods: Serum samples were prospectively obtained from 111 convalescent COVID-19 patients, staying in dedicated Isolation–hotels, and tested for the presence of SARS-CoV-2 IgG by anti-S1 protein ELISA.Results: SARS-CoV-2 IgG was detected in 78 (70.3%) patients tested within the first month from diagnosis. While highly variable between patients, the rate of antibody detection generally increased with time, from 47.1% to 93.8% at the first and fourth weeks from diagnosis, respectively, with the largest shift observed between the second and third week. Notably, the presence of more profound symptoms at presentation, namely, fever and chills, positively and independently correlated with early antibody response. IgG-positive patients had higher ferritin levels (p=0.039). Older age (p<0.001) and increased CRP levels (p=0.001) were associated with higher SARS-CoV-2 IgG levels. Conclusions: The identified temporal pattern along with the correlation between inflammation-related clinical and laboratory parameters and early IgG response in patients with mild COVID-19, could provide a basis for better prediction and understating of the immune response to SARS-CoV-2, and inform therapeutic donor-plasma selection.