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Indoleamine 2,3-dioxygenase (IDO) is induced by proinflammatory cytokines and by CTLA-4-expressing T cells and constitutes an important mediator of peripheral immune tolerance. In chronic hepatitis C, we found upregulation of IDO expression in the liver and an increased serum kynurenine/tryptophan ratio (a reflection of IDO activity). Huh7 cells supporting hepatitis C virus (HCV) replication expressed higher levels of IDO mRNA than noninfected cells when stimulated with gamma interferon or when cocultured with activated T cells. In infected chimpanzees, hepatic IDO expression decreased in animals that cured the infection, while it remained high in those that progressed to chronicity. For both patients and chimpanzees, hepatic expression of IDO and CTLA-4 correlated directly. Induction of IDO may dampen T-cell reactivity to viral antigens in chronic HCV infection.

Original publication

DOI

10.1128/JVI.02248-06

Type

Journal article

Journal

J Virol

Publication Date

04/2007

Volume

81

Pages

3662 - 3666

Keywords

Antigens, CD, Antigens, Differentiation, CTLA-4 Antigen, Cohort Studies, Gene Expression Regulation, Enzymologic, Hepatitis C, Humans, Indoleamine-Pyrrole 2,3,-Dioxygenase, RNA, Messenger, Up-Regulation