biostudies-literatureCollins JMNational Institute of Allergy and Infectious DiseasesNIAID NIH HHSFIC NIH HHSNational Institutes of HealthNIH Fogarty International CenterNIH HHS235-243https://www.ebi.ac.uk/biostudies/studies/S-EPMC12573232biostudies-literatureUnknown233(2)Greater understanding of the role of tryptophan metabolism in the immune response to tuberculosis (TB) has provided promising avenues to explore new diagnostic and therapeutic modalities. Animal and human studies have demonstrated that host indoleamine 2,3-dioxygenase 1 (IDO1) is upregulated in response to infection with Mycobacterium tuberculosis, resulting in increased tryptophan metabolism to kynurenine. In TB disease, this is evidenced by elevation of the plasma kynurenine to tryptophan ratio, which is reversed with effective TB treatment, thus showing utility as a potential diagnostic and therapeutic biomarker. Kynurenine and downstream metabolites promote an immunosuppressive microenvironment in TB granulomas, which may facilitate immune evasion. IDO inhibition in nonhuman primates hThe Journal of infectious diseasesTargeting Tryptophan Metabolism for Tuberculosis Biomarkers and Host-Directed Therapy.PMC12573232P30AI168386R01AI173946D43 TW007124K23AI144040K24 AI190403P30 AI168386D43TW007124R01 AI173946R21AI178324R21 AI178324K23 AI144040R01 AI182244R01AI182244Collins JMTukvadze NKempker RRfalseTargeting Tryptophan Metabolism for Tuberculosis Biomarkers and Host-Directed Therapy.Greater understanding of the role of tryptophan metabolism in the immune response to tuberculosis (TB) has provided promising avenues to explore new diagnostic and therapeutic modalities. Animal and human studies have demonstrated that host indoleamine 2,3-dioxygenase 1 (IDO1) is upregulated in response to infection with Mycobacterium tuberculosis, resulting in increased tryptophan metabolism to kynurenine. In TB disease, this is evidenced by elevation of the plasma kynurenine to tryptophan ratio, which is reversed with effective TB treatment, thus showing utility as a potential diagnostic and therapeutic biomarker. Kynurenine and downstream metabolites promote an immunosuppressive microenvironment in TB granulomas, which may facilitate immune evasion. IDO inhibition in nonhuman primates h2026-01-01T00:00:00Z2026 Feb2026-07-09T11:11:02.734Z2026-07-09T10:42:03.482ZS-EPMC125732324103749010.1093/infdis/jiaf510