Figure 1.

Hypothetical Model of the Two Phases of Coronavirus Disease 2019 (COVID-19) and the Steps at Which Various Treatments Are Likely to Be Efficient (Blue Rectangles).

During the initial phase, infection of epithelial cells by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) induces weak production of interferon (IFN) α/β by these cells and the initiation of a limited antiviral immune response, leading to apoptosis of infected cells, the production of proinflammatory molecules, and the recruitment of immune cells. At this time, the viral load might be reduced by antivirals combined with an antiviral IFNα/β response enhanced by immunomodulator treatments [e.g., potentially transforming growth factor β (TGFβ) blockade]. Later, in some patients, an excessive inflammatory/immune response might give rise to a cytokine storm and/or acute respiratory distress syndrome (ARDS). This deleterious hyperinflammatory immune response might be dampened by anti-inflammatory/immunosuppressive treatments. Abbreviations: Abs, antibodies; ACE2, angiotensin-converting enzyme 2; IVIg, intravenous immunoglobulin therapy; IL, interleukin; TNF, tumor necrosis factor.