Dendritic cells (DCs) isolated from patients with chronic hepatitis C virus (HCV) infection display an impaired capacity to generate type 1 CD4(+) T cell immunity. Several reports have described an immunomodulatory function for the HCV core protein, and circulating core has been shown to associate with the putative gC1q receptor, gC1qR, expressed on host immune cells. However, the molecular mechanism(s) of HCV core-mediated DC dysfunction has not been defined. Herein, ligation of gC1qR on human monocyte-derived DCs (MDDCs) with HCV core or anti-gC1qR agonist antibody was shown to inhibit TLR-induced IL-12 production but not the production of other TLR-stimulated cytokines. Furthermore, engagement of gC1qR on MDDCs resulted in reduced IFN-gamma secretion by allogeneic CD4(+) T lymphocytes during mixed lymphocyte culture. Differentiation of CD4(+) T cells cocultured with HCV core- or anti-gC1qR antibody-treated MDDCs was also skewed toward production of Th2 cytokines, including IL-4. Importantly, that addition of IL-12 rescued IFN-gamma production and Th1 differentiation by CD4(+) T cells. Therefore, engagement of gC1qR on DCs by HCV core limits the induction of Th1 responses and may contribute to viral persistence.

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BackgroundHepatitis C Virus (HCV) is remarkably efficient at establishing persistent infection and is associated with the development of chronic liver disease. Impaired T cell responses facilitate and maintain persistent HCV infection. Importantly, CD4+ regulatory T cells (Tregs) act by dampening antiviral T cell responses in HCV infection. The mechanism for induction and/or expansion of Tregs in HCV is unknown.Methodology/Principal FindingsHCV-expressing hepatocytes were used to determine if hepatocytes are able to induce Tregs. The infected liver environment was modeled by establishing the co-culture of the human hepatoma cell line, Huh7.5, containing the full-length genome of HCV genotype 1a (Huh7.5-FL) with activated CD4+ T cells. The production of IFN-γ was diminished following co-culture with Huh7.5-FL as compared to controls. Notably, CD4+ T cells in contact with Huh7.5-FL expressed an increased level of the Treg markers, CD25, Foxp3, CTLA-4 and LAP, and were able to suppress the proliferation of effector T cells. Importantly, HCV+ hepatocytes upregulated the production of TGF-β and blockade of TGF-β abrogated Treg phenotype and function.Conclusions/SignificanceThese results demonstrate that HCV infected hepatocytes are capable of directly inducing Tregs development and may contribute to impaired host T cell responses.

Inflammatory responses in the intestinal mucosa inevitably result in the recruitment of neutrophils (polymorphonuclear leukocytes [PMNs]). Epithelial cells that line the mucosa play an integral role in the recruitment, maintenance, and clearance of PMNs at sites of inflammation. The consequences of such PMN–epithelial interactions often determine tissue responses and, ultimately, organ function. For this reason, there is significant interest in understanding how PMNs function in the mucosa during inflammation. Recent studies have shown that PMNs play a more significant role in molding of the immune response than previously thought. Here, we review the recent literature regarding the contribution of PMNs to the development and resolution of inflammation, with an emphasis on the role of the tissue microenvironment and pathways for promoting epithelial restitution. These studies highlight the complex nature of inflammatory pathways and provide important insight into the difficulties of treating mucosal inflammation.