A key finding of our recent study [22] was that IDO inhibitor treatment reduced parasite burdens when administered to mice with established L. major infections, revealing a constitutive requirement for IDO to maintain local conditions that favor parasite persistence and pathogenesis and suggesting that 1-methyl-[D]-tryptophan (D-1MT) treatment may help reduce parasite burdens in patients with leishmaniasis. Here, IDO1 is linked to leishmaniasis.