Exosomes: Applications in Respiratory Infectious Diseases and Prospects for Coronavirus Disease 2019 (COVID-19)

Exosomes are small extracellular vesicles of 30-150 nm diameter secreted by almost all cells. In recent years, with continuous deeper understanding of exosomes physiological functions, different reports have proven that exosomes can facilitate cell-to-cell communication by binding to target cells and transferring their contents, together with RNAs, DNAs, proteins, and lipids between cells and tissues. With advantages that exosomes can be involved in various types of physiological processes, such as blood coagulation, cellular homeostasis, inflammation, immune surveillance, stem cell differentiation, neuroprotection, and tissue regeneration and angiogenesis. Exosomes have been demonstrated that they can be applied in identification and treatment of multiple disorders such as cancers, cerebral ischemia, and respiratory infectious diseases. Importantly, researchers utilize application of exosomes in the treatment of various respiratory infectious diseases that have made some breakthrough progress. However, with the global pandemic of Coronavirus Disease 2019 (COVID-19), we have focused on applications of exosomes in respiratory infectious diseases and their serious complications, including influenza, TB, ARDS and sepsis. In this review, we explain the use of exosomes in various respiratory infectious diseases and their serious complications, and hope to provide new ideas for the treatment of new coronavirus infections.