01 February 2021. Vol.12 No.1
Figure 1. The development of COVID19.
Viral infection: TMPRSS2 cleaves the S protein of SARS-CoV-2; The RBD on the S1 subunit binds to ACE2 on the cell surface. Following entry into the cell, viral RNA is released and combined with RdRp to synthesize a full-length negative-strand RNA as an RNA replication template. After translation, structural proteins are localized to the inner membrane of Golgi for assembly. Cytokine storm syndrome: The immune system is over-activated, followed by the overproduction of multiple inflammatory factors. Multiple immune cells are recruited. As a result, healthy cells are damaged by overactive immune response. Acute respiratory distress syndrome: In the exudative phase, macrophages are activated and release pro-inflammatory mediators, which leads to the aggregation of neutrophils and monocytes. Activated neutrophils induce further damage. The injury leads to loss of barrier function and fluid accumulation in the interstitium and alveoli. In the proliferative period, the tissue homeostasis is recovered.