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1 University of Massachusetts Medical School;
2 Banco de Sangre. Caracas
3 E-mail: irene.bosch{at}umassmed.edu
The depletion of L-tryptophan has been associated with the inhibition of growth of microorganisms and also has profound effects on T cell proliferation and immune tolerance. The enzyme Indoleamine 2,3-dioxygenase (IDO) catalyzes the rate-limiting step in the catabolic pathway of L-tryptophan. Gene expression analysis has shown up-regulation of genes involved in L-tryptophan catabolism in models of dengue virus (DENV)-infection in vitro. To understand the role of IDO during DENV infection, we measured IDO activity in serum from controls and DENV-infected patients. We found increased IDO activity, lower levels of L-tryptophan and higher levels of L-kynurenine, in serum from DENV-infected patients during the febrile days of the disease, as compared to patients with other febrile illnesses and healthy donors. Furthermore, we confirmed up-regulation of IDO mRNA expression in response to DENV in vitro, using a dendritic cell (DC) model of DENV infection. We found that the antiviral effect of IFN-
in DENV-infected DC in vitro was partially dependent on IDO activity. Our results demonstrate that IDO plays an important role in the antiviral effect of IFN-
against DENV infection in vitro and suggest a role in the immune response to DENV infections in vivo.
Received 21 June 2008;
accepted 7 December 2008.
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