title: Dengue virus activates membrane TRAIL relocalization and IFN-α production by human plasmacytoid dendritic cells in vitro and in vivo.
abstract: BACKGROUND
  Dengue displays a broad spectrum of clinical manifestations that may vary from asymptomatic to severe and even fatal features. Plasma leakage/hemorrhages can be caused by a cytokine storm induced by monocytes and dendritic cells during dengue virus (DENV) replication. Plasmacytoid dendritic cells (pDCs) are innate immune cells and in response to virus exposure secrete IFN-α and express membrane TRAIL (mTRAIL). We aimed to characterize pDC activation in dengue patients and their function under DENV-2 stimulation in vitro. METHODS FINDINGS: Flow cytometry analysis (FCA) revealed that pDCs of mild dengue patients exhibit significantly higher frequencies of mTRAIL compared to severe cases or healthy controls. Plasma levels of IFN-α and soluble TRAIL are increased in mild compared to severe dengue patients, positively correlating with pDC activation. FCA experiments showed that in vitro exposure to DENV-2 induced mTRAIL expression on pDC. Furthermore, three dimension microscopy highlighted that TRAIL was relocalized from intracellular compartment to plasma membrane. Chloroquine treatment inhibited DENV-2-induced mTRAIL relocalization and IFN-α production by pDC. Endosomal viral degradation blockade by chloroquine allowed viral antigens detection inside pDCs. All those data are in favor of endocytosis pathway activation by DENV-2 in pDC. Coculture of pDC/DENV-2-infected monocytes revealed a dramatic decrease of antigen detection by FCA. This viral antigens reduction in monocytes was also observed after exogenous IFN-α treatment. Thus, pDC effect on viral load reduction was mainly dependent on IFN-α production.
  
  
  CONCLUSIONS
  This investigation characterizes, during DENV-2 infection, activation of pDCs in vivo and their antiviral role in vitro. Thus, we propose TRAIL-expressing pDCs may have an important role in the outcome of disease.
authors.affiliation: Laboratório de Imunologia Viral, Instituto Oswaldo Cruz, FIOCRUZ, Rio de Janeiro, Brazil.
authors.forename: Mariana
authors.initials: M
authors.lastname: Gandini
authors.forename: Christophe
authors.initials: C
authors.lastname: Gras
authors.forename: Elzinandes Leal
authors.initials: EL
authors.lastname: Azeredo
authors.forename: Luzia Maria de Oliveira
authors.initials: LM
authors.lastname: Pinto
authors.forename: Nikaïa
authors.initials: N
authors.lastname: Smith
authors.forename: Philippe
authors.initials: P
authors.lastname: Despres
authors.forename: Rivaldo Venâncio
authors.initials: RV
authors.lastname: da Cunha
authors.forename: Luiz José
authors.initials: LJ
authors.lastname: de Souza
authors.forename: Claire Fernandes
authors.initials: CF
authors.lastname: Kubelka
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: Herbeuval
mesh_terms: D000328:Adult; D003713:Dendritic Cells / Q000276:immunology* / Q000821:virology*; D003716:Dengue Virus / Q000276:immunology*; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D016898:Interferon-alpha / Q000097:blood*; D008297:Male; D008875:Middle Aged; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000378:metabolism*; D055815:Young Adult
chemical_list: D016898:Interferon-alpha; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human