Comparison of target antigen and immunoglobulin isotypes in anti-SARS-CoV-2 antibodies from natural infection and vaccination

Abstract

Abstract The immune system produces antibodies following SARS-CoV-2 infection and vaccination. However, we lack comprehensive information about the humoral responses after infection and vaccination, which are similar but might differ in type or amount of produced antibodies. Therefore, we compared different types and amounts of antibodies produced by the immune system in response to infection versus those produced by BNT162b2 (Pfizer/BioNTech) vaccines. Our findings indicated that naturally infected individuals had 14-fold higher anti-SARS-CoV-2 spike protein (anti-S) and 41-fold higher anti-SARS-CoV-2 receptor-binding domain of the viral spike protein (anti-RBD) IgM titers than SARS-CoV-2-naïve vaccinees. A significantly rapid increase in anti-S IgG titers in primary infection was observed, eventually reaching a level similar to that in people who had third booster vaccination. Moreover, a significant positive correlation was observed between anti-S and anti-RBD levels in naturally infected and BNT162b2-vaccinated individuals. Collectively, our data suggest that anti-RBD and anti-S IgG can serve as neutralizing antibody predictors during routine laboratory testing.