Figure 1:

Potential mechanisms of action of anti–severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies in coronavirus disease 2019 (COVID-19). This figure illustrates the normal entry of SARS-CoV-2 in a host cell, in which membrane fusion is mediated by the interaction between the SARS-CoV-2 spike glycoprotein (red) and the angiotensin-converting enzyme 2 (ACE2) receptor (green) on the host cell, either through the cytoplasmic or endosomal route. Antibodies directed against the receptor-binding domain (RBD) of the spike protein can interfere with its interaction with the ACE2 receptor and prevent viral entry in the host cell (panel A). Antibodies directed against epitopes outside the RBD can also exert antiviral functions through other mechanisms (panels B, C and D). The relative importance of these various functions in rescuing patients from an active SARS-CoV-2 infection is unknown. Importantly, neutralization assays generally used to qualify hyperimmune products measure only 1 of the 4 mechanisms depicted here and do not necessarily correlate with the others.