Figure 2.

Potential Astroglial and Microglial Roles in SARS-CoV-2 Infection.

Astrocytes and microglia are viral hosts: Perivascular astrocytes may incorporate viral particles by direct contact with infected endothelial cells. However, BBB breakdown may also lead to viral infection of nonperivascular astrocytes and microglia. In both situations, infected cells may act as viral hosts giving nonproductive infection with mild inflammatory response and with microglia acting as antigen-presenting cells; or astrocytes may give rise to a productive infection, with destruction of astroglial network. This latter possibility is more unlikely based on clinical findings.

Astrocytes and microglia are not viral hosts: Astrocytes and microglia are not primary targets of viral infection, but they are responsive to proinflammatory signals from endothelial cells, macrophages, and/or neurons. In such case, astrocytes and microglia may engage in a proinflammatory gene expression program that would expand neuroinflammation. This maladaptive reactive astrogliosis would reduce neuroprotective and metabolic support to neurons which secondarily may degenerate by lack of nutrients and neurotrophic factors.

A = astrocytes; M = microglia; N = neurons.