Aspergillus fumigatus tryptophan metabolic route differently affects host immunity

Indoleamine 2,3-dioxygenases (Ms) degrade L-tryptophan to kynurenines and drive the de novo synthesis of nicotinamide adenine dinucleotide. Unsurprisingly, various invertebrates, vertebrates, and even fungi produce IDO. In mammals, IDO1 also serves as a homeostatic regulator, modulating immune response to infection via local tryptophan deprivation, active catabolite production, and non-enzymatic cell signaling, Whether fungal !dos have pleiotropic functions that impact on host-fungal physiology is unclear. Here, we show that Aspergillus fumigatus possesses three ido genes that are expressed under conditions of hypoxia or tryptophan abundance. Loss of these genes results in increased fungal pathogenicity and inflammation in a mouse model of aspergillosis, driven by an alternative tryptophan degradation pathway to indole derivatives and the host aryl hydrocarbon receptor. Fungal tryptophan metabolic pathways thus cooperate with the host xenobiotic response to shape host-microbe interactions in local tissue microenvironments.

Automated summary

Research shows that Aspergillus fumigatus expresses different ido genes under varying environmental conditions, and loss of these genes results in increased pathogenicity and inflammation. Fungal tryptophan metabolic pathways cooperate with the host xenobiotic response to shape host-microbe interactions.