ZIKV infection of NPCs and HepG2 cells was demonstrated to induce kynurenine (Kyn), a tryptophan-derived aryl hydrocarbon receptor (AHR) ligand typically produced during inflammation by the enzymatic activity of indoleamine 2,3-dioxygenase 1 and 2 and tryptophan 2,3-dioxygenase [64]. Here, AHR is linked to Zika virus infectious disease.