Fig. 1.

SARS-CoV-2 enters the host cell through the binding of the viral S protein to the host ACE2 receptor. The S protein is cleaved into S1 and S2 by a cell-derived protease. S1 binds to ACE2 and S2 is activated by the host serine protease TMPRSS2 and results in membrane fusion. Once inside, SARS-CoV-2 hijacks the host machinery to transcribe, replicate, and translate its RNA genome and structural proteins before being reassembled, encapsulated, and exocytosed from the cell. SARS-CoV-2 antigens are presented to host APCs, which produce a range of cytokines. The release of cytokines causes an enhanced, unbalanced, and devastating proinflammatory response in the host. Adapted from Review Invivogen (www.invivogen.com). APCs, antigen-presenting cells; ER, Endoplasmic Reticulum; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2.