Complementarity Determining Regions in SARS-CoV-2 hybrid immunity

Pre-vaccination SARS-CoV-2 infection can boost protection elicited by COVID-19 vaccination and post-vaccination breakthrough SARS-CoV-2 infection can boost existing immunity conferred by COVID-19 vaccination. Such ‘hybrid immunity’ is effective against SARS-CoV-2 variants. In order to understand ‘hybrid immunity’ at the molecular level we studied the complementarity determining regions (CDR) of anti-RBD (receptor binding domain) antibodies isolated from individuals with ‘hybrid immunity’ as well as from ‘naive’ (notSARS-CoV-2 infected) vaccinated individuals. CDR analysis was done by liquid chromatography/mass spectrometry-mass spectrometry.