Sensitive detection of total anti-Spike antibodies and isotype switching in asymptomatic and symptomatic individuals with COVID-19

Early detection of infections is crucial to limit the spread of coronavirus 2019 disease (COVID-19). Here, we develop a flow cytometry-based assay to detect SARS-CoV-2 Spike protein (S protein) antibodies in COVID-19 patients. The assay detects specific IgM, IgA and IgG in COVID-19 patients and also the acquisition of all IgG subclasses, with IgG1 being the most dominant. The antibody response is significantly higher at a later stage of the infection. Furthermore, asymptomatic COVID-19 patients also develop specific IgM, IgA and IgG, with IgG1 as the most dominant subclass. Although the antibody levels are lower in asymptomatic infections, the assay is highly sensitive and detect 97% of asymptomatic infections. These findings demonstrate that the assay can be used for serological analysis of symptomatic infections, and also asymptomatic infections, which may, otherwise, go undetected.
Graphical Abstract
Highlights Flow cytometry assay detects specific antibodies in symptomatic COVID-19 patients. Asymptomatic COVID-19 patients also develop specific antibodies. IgG1 is the dominant IgG subclass in both symptomatic and asymptomatic patients. The assay is highly sensitive and detects 97% of asymptomatic infections.
Using a flow cytometry-based assay, Goh et al. finds specific antibodies in symptomatic COVID-19 patients’ plasma samples. IgG1 is the most dominant IgG subclass. Despite lower antibody levels, the assay detects 97% of asymptomatic infections, suggesting the feasibility of the assay to detect asymptomatic infections, which may otherwise go undetected.