Targeting Mononuclear Phagocytes to Treat COVID-19

Coronavirus disease 2019 (COVID-19) and its etiological agent severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) have caused considerable illness and death worldwide. The innate immune system seems to play a principal in the disease, as a hallmark of severe COVID-19 is excessive inflammation. Monocytes and macrophages are important innate immune cells that become pro-inflammatory and promote adaptive immune responses during viral infection. In this chapter we present evidence linking these cells to severity of COVID-19. Namely, monocytes and macrophages infiltrate the infected tissue during the early stages of infection and show pro-inflammatory responses that appear to be linked to those predicting tissue pathology during disease. Additionally, studies in isolated cells demonstrate that monocytes and macrophages respond by producing pro-inflammatory cytokines when directly stimulated by SARS-CoV-2. While most anti-inflammatory pharmaceutical treatments for COVID-19 have focused on systemic infiltration, some of the most promising have known or suspected effects on monocyte and macrophage inflammatory responses. Therefore, targeting these cells to treat severe COVID-19 is a promising strategy for this important disease.