Effect of indole-3-propionic acid supplementation on the composition of the gut microbiota during experimental influenza infection

Influenza still poses serious medical and economic issues worldwide, and preventive strategies that limit infection incidence and disease severity would be invaluable. A growing body of literature data suggests that manipulation of the gut microbiota can usefully influence influenza outcomes. Indeed, host immune responses to respiratory viruses are closely linked to the microbiome and metabolism via the gut-lung axis. Indole-3-propionic acid (IPA) is a tryptophan derivative produced by the gut microbiota. Its concentration dropped 7 days postinfection, the peak of the acute response, and correlated with disease severity markers. In view of IPA s functions in influenza, we hypothesized that IPA supplementation can therapeutically protect against this disease in a mouse model. In the present study, we demonstrate that IPA partially protects against influenza by reducing viral load and lung inflammation. The protective effects were associated with the recovery in IPA levels and with a distinct, but not significant, shift in the gut microbial composition.