Rapid and Quantitative Detection of Human Antibodies Against the 2019 Novel Coronavirus SARS CoV2 and its Variants as a Result of Vaccination and Infection

ABSTRACT Measuring the antibody response to 2019 SARS CoV2 is critical for diagnostic purposes, monitoring the prevalence of infection, and for gauging the efficacy of the worldwide vaccination effort COVID-19. In this study, a microchip-based grating coupled fluorescent plasmonic (GC-FP) assay was used to measure antibody levels that resulted from COVID-19 infection and vaccination. In addition, we measured the relative antibody binding towards antigens from variants CoV2 virus variants, strains B.1.1.7 (UK) and B.1.351 (S. African). Antibody levels against multiple antigens within the SARS CoV2 spike protein were significantly elevated for both vaccinated and infected individuals, while those against the nucleocapsid (N) protein were only elevated for infected individuals. GC-FP was effective for monitoring the IgG-based serological response to vaccination throughout the vaccination sequence, and could also resolve acute (within hours) increases in antibody levels. A significant decrease in antibody binding to antigens from the B.1.351 variant, but not B.1.1.7, was observed for all vaccinated subjects when measured by GC-FP as compared to the 2019 SARS CoV2 antigens. These results were corroborated by competitive ELISA assay. Collectively, the findings suggest that GC-FP is a viable, rapid, and accurate method for measuring both overall antibody levels to CoV2 and relative antibody binding to viral variants during infection or vaccination.