Figure 3.

SARS-CoV-2 viral structure, infective cycle, and cell tropism. The structural proteins of SARS-CoV-2 comprise the S (spike), N (nucleocapsid), M (membrane), and E (envelop) proteins. For viral entry into the host cell, the spike protein interacts with the ACE2 and TMPRRS2 enzymes widely distributed in several human tissues. The infective cycle of SARS-CoV2 includes endocytosis mediated by the viral spike protein–ACE2 cell interaction. Once entering the cell, replicating and forming virions is achieved by the assembly and maturation of new viral particles and subsequent exocytosis. The lower panel shows the target organs previously developed to simulate viral infection processes. These 3D cell cultures resemble in vitro aspects of human pathophysiology, which are crucial to understand and address the current pandemic.