Figure 2.

Protective and Pathogenic Roles of Type I IFNs during Coronavirus Infection

Both viral and host factors can affect the timing of IFN response. When the initial viral burden is low (left), IFNs can be induced early and clear the infection effectively. High viral load (right) may strongly suppress the IFN response due to viral evasion mechanisms, causing its delayed induction. Alternatively, IFN induction may be compromised in older hosts. When the IFN response is insufficient to control initial viral replication, late onset IFN could lead to inflammation and lung injury.