Figure 1.

Microbiome-associated inflammation profiles and potential reactions to severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2).

The microbiome influences host inflammation through the regulation of host immunological processes (proinflammatory effects are indicated by the orange arrow, and anti-inflammatory effects by the blue arrow). These include the production of host pro- and anti-inflammatory mediators, and the migration of bacteria or bacterial products, such as lipopolysaccharide, through the gut lining. (A) A microbiome that contributes to a balanced or low-inflammation state (low-inflammation properties are indicated by the blue systemic background and the pale-pink microbial background) with a relatively higher level of anti-inflammatory cytokines. (B) A microbiome that contributes to a proinflammatory state (high-inflammation properties are indicated by the pale-orange systemic background and the darker-pink gut background), with a relatively higher number of proinflammatory mediators, and potential translocation of bacterial products into systemic circulation (the proinflammatory state is indicated by the relatively larger orange arrow). The bottom two images show the putative reactions of these systems to SARS-CoV-2 infection, denoted by the presence of virions. (C) A relatively muted proinflammatory response to viral infection, represented by the pink systemic background behind the immune cells. (D) A strong proinflammatory response to viral infection, represented by the red systemic background behind the immune cells.