Decreased interferon‐α production and impaired regulatory function of plasmacytoid dendritic cells induced by the hepatitis C virus NS 5 protein

Abstract

pDC are known to produce large amount of IFN-α/β in response to viruses, and act as a major link between the innate and adaptive immune response. This study concentrated on the interaction of human peripheral blood derived pDC with HCV NS3, NS4, and NS5 proteins, and their maturation, cytokine secretion and functional properties. It was shown that HCV NS5 interferes with CD40L induced maturation of pDC as indicated by decreased expression of CD83 and CD86 markers. CpG ODN stimulated HCV NS3 and NS5 treated pDC showed decreased production of IFN-α. In the case of NS3, IFN-α production was reduced to 126 pg/ml as compared to 245 pg/ml in controls (P < 0.01), and with NS5, IFN-α production was reduced to 92 pg/ml as compared to 238 pg/ml in controls (P < 0.05). In the presence of HCV NS5, the T cell stimulatory capacity of pDC was impaired, as indicated by decreased proliferation of T cells, and decreased production by the T cells of IFN-γ, which were down to 86 pg/ml as compared to 260 pg/ml in controls (P < 0.05). These results suggest that HCV NS5 impairs pDC function and is in agreement with several other in vivo studies indicating decreased numbers of, and dysfunctional pDC, in chronic HCV infected patients. Key words dendritic cells, hepatitis C virus, interferon-α, nonstructural proteins.HCV, a member of the Flaviviridiae family of viruses, is a major cause of chronic hepatitis, cirrhosis and hepatocellular carcinoma. HCV infection is characterized by its ability to become chronic in 70% to 80% patients. The clinical course of HCV infection results from the fluctuating balance between the capacity of the virus to replicate, spread, and mutate rapidly and the inability of the host to eliminate it. Following HCV infection, an initial high level List of Abbreviations: APC, antigen presenting cells; CFSE, carboxyfluorescein diacetate succinidyl ester; CpG ODN, cytosine-phosphate-guanisone oligonucleotide; DC, dendritic cells; FACS, fluorescent-activated cell sorting; GADPH, glyceraldehyde-3-phosphate dehydrogenase; HCV, hepatitis C virus; HCVcc, cell culture-produced HCV; IFN, interferon; IL, interleukin; mDC, myeloid dendritic cells; MFI, mean fluorescent intensity; MHC, major histocompatibility complex; NK, natural killer; NS, nonstructural; PBMC, peripheral blood mononuclear cells; pDC, plasmacytoid dendritic cells; PHA, phytohemagglutinin; PI, propidium iodide; Th, helper T cells; TLR, toll like receptor; TNF-α, tumor necrosis factor-α of viremia is generally reduced by the immune system. In those cases where the virus is not completely removed, a controlled infection persists over many years (1). Several ex vivo and in vitro studies have indicated that chronic HCV infected patients show decreased DC function as compared to both healthy individuals and patients who have resolved their infection. A number of groups have confirmed that DC derived from HCV-infected patients

Impaired Toll-like receptor 7 and 9 signaling: from chronic viral infections to cancer

“…Recent studies have shown that another non-structural HCV protein, NS5A, interacts with the TLR7 and TLR9 adaptor MyD88 to prevent recruitment of IRAK1 and assembly of a multiprotein signal-transducing complex [48,49]. However, this interaction also does not seem to occur in pDCs in which HCV does not replicate and thus non-structural HCV proteins are not expressed [44].…”

Hepatitis C Virus Is a Weak Inducer of Interferon Alpha in Plasmacytoid Dendritic Cells in Comparison with Influenza and Human Herpesvirus Type-1

“…Alternatively, the E1 protein (which was not tested in this study) could play a role in mediating the inhibition to CpG-A induced production of IFN-α. A recent report by Amjad et al [46] showed that non-structural proteins of HCV (namely NS3 and NS5) inhibit TLR9-induced IFN-α secretion. Because HCV particles do not contain non-structural proteins and because HCV does not express its genome in pDCs [21], it is difficult to interpret these results in the context of interaction of NS3 and NS5 with circulating pDCs studied in our work.…”

Dendritic cells, regulatory T cells and the pathogenesis of chronic hepatitis C

“…Additional studies reported that DCs obtained from chronically-infected patients were phenotypically immature and failed to upregulate maturation (costimulatory) markers in response to stimuli such as TNF-α 66 , 73 . Circulating pDCs in chronic HCV-infected patients exhibit: diminished HLA-DR expression, a markedly reduced capacity to secrete IFN-α and, consequently, decreased anti-viral potency 36 , 39 , 44 , 67 , 68 , 80 . mDCs in chronic HCV infections secrete significantly lower levels of IL-12 and increased concentrations of IL-10, which tends to skew the immune response toward tolerance and a reduced ability to induce T-cell proliferation and T h1 polarization 36 , 47 , 49 , 67 , 69 , 72 , 75 - 77 , 81 .…”