Importance of glycosylation for SARS-CoV-2 virus, antibodies and COVID-19

Summary In addition to the known endemic respiratory viruses, the pandemic SARS-CoV-2 has been added, with terrible effects on the population worldwide. This virus, like many others, has a glycoprotein structure the so-called spike protein, which interacts with the ACE-2 receptor as a cellular entry gate and thus initiates the infection. Just as this glycosylation causes infectiousness, the effect of the protective antibodies is also determined by their degree of glycosylation. In particular, the so-called Fc part of the immunoglobulins plays an important role. The type of bound sugar such as fucose, mannose, sialic acid, etc. determines, among other things, which reactions are triggered by binding to immune cells such as NK cells to their existing Fc receptors. These include antibody-dependent cellular phagocytosis (ADCP), antibody-dependent cellular cytotoxicity (ADCC), antibody-dependent cellular trogocytosis (ADCT) and antibody-dependent cellular complement deposition (ADCD). In addition to protective phagocytosis, these reactions can trigger the antibody-dependent enhancement (ADE) of the infection and also the dreaded cytokine storm in COVID-19 patients. The functional diversification of IgGs by Fc glycosylation can be determined and tracked both after vaccination and during the disease.