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Indoleamine‐2,3‐dioxygenase as an effector and an indicator of protective immune responses in patients with acute hepatitis B
Author(s) -
Yoshio Sachiyo,
Sugiyama Masaya,
Shoji Hirotaka,
Mano Yohei,
Mita Eiji,
Okamoto Toru,
Matsuura Yoshiharu,
Okuno Alato,
Takikawa Osamu,
Mizokami Masashi,
Kanto Tatsuya
Publication year - 2016
Publication title -
hepatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.488
H-Index - 361
eISSN - 1527-3350
pISSN - 0270-9139
DOI - 10.1002/hep.28282
Subject(s) - indoleamine 2,3 dioxygenase , cxcl10 , immunology , medicine , interferon , hepatitis , chemokine , immune system , kynurenine , cxcl9 , virology , biology , tryptophan , biochemistry , amino acid
Indoleamine‐2, 3‐dioxygenase (IDO), an interferon‐γ‐inducible enzyme catalyzing tryptophan into kynurenine, exerts dual functions in infectious diseases, acting as a suppressor of intracellular pathogens and as an immune regulator. We explored the roles of IDO in hepatitis B virus (HBV) clearance from infected patients. We examined IDO activity, serum chemokines, and cytokines in 53 HBV‐positive patients (25 acute hepatitis, 14 chronic hepatitis, and 14 hepatic flare) and 14 healthy volunteers. In order to clarify the mechanisms of IDO induction and its impact on HBV replication, we used a culture model consisting of human natural killer cells, plasmacytoid dendritic cells, and HBV‐transfected Huh7 cells in which IDO expression is controlled. A robust activation of IDO with an inverse correlation of alanine aminotransferase at the peak was observed in patients with acute hepatitis B but not in patients with hepatic flare. In acute hepatitis patients who eventually cleared HBV, IDO activity, chemokine (C‐X‐C motif) ligand 9 (CXCL9), CXCL10, and CXCL11 increased at the peak of alanine aminotransferase. In contrast, in patients with hepatic flare, IDO activity remained at lower levels during the observation period, regardless of the surge of CXCL9, CXCL10, and CXCL11 at the alanine aminotransferase peak. Natural killer cells and plasmacytoid dendritic cells synergistically produced interferon‐γ and interferon‐α, thereby enhancing IDO activity and HBV suppression in Huh7 cells. Such suppressor capacity of IDO on HBV was abrogated in IDO‐knockout cells and recovered by the reinduction of IDO in the cells. Conclusion: IDO is an anti‐HBV effector and an indicator of subsequent immune responses operative during the early phase of infection; its activity is boosted by coexisting natural killer cells and plasmacytoid dendritic cells. (H epatology 2016;63:83–94)