IDO1 and congenital rubella syndrome: Meanwhile, the levels of KP rate-limiting enzymes indole-amine oxygenase-1 (IDO1), 3-Hydroxyanthranilic acid 3, 4-dioxygenase (3HAO), and quinolinate phosphoribosyl transferase (QPRT) were markedly increased in both the PFC and colon samples from CRS and CRS + DEP-tr mice, and these effects could be rescued by HC-GM transplantation (Fig. 5C–E).