Dynamics of immature subsets of dendritic cells during antiviral therapy in HLA-A24-positive chronic hepatitis C patients

IFN-α promotes rapid human Treg contraction and late Th1-like Treg decrease

Type I IFNs are pleiotropic cytokines that exert concerted activities in the development of antiviral responses. Regulatory T cells represent a physiologic checkpoint in the balance between immunity and tolerance, requiring fine and rapid controls. Here, we show that human regulatory T cells are particularly sensitive to the sequential effects of IFN-α. First, IFN-α exerts a rapid, antiproliferative and proapoptotic effect in vitro and in vivo, as early as after 2 d of pegylated IFN/ribavirin therapy in patients with chronic hepatitis C. Such activities result in the decline, at d 2, in circulating regulatory T cell frequency and specifically of the activated regulatory T cell subset. Later, IFN-based therapy restrains the fraction of regulatory T cells that can be polarized into IFN-γ-producing Th1-like regulatory T cells known to contribute to chronic immune activation in type 1 inflammation. Indeed, Th1-like regulatory T cell frequency significantly declines after 30 d of therapy in vivo in relation to the persistent decline of relevant IL-12 sources, namely, myeloid and 6-sulfo LacNAc-expressing dendritic cells. This event is recapitulated by experiments in vitro, providing evidence that it may be attributable to the inhibitory effect of IFN-α on IL-12-induced, Th1-like regulatory T cell polarization. In summary, our results suggest that IFN-α-driven, early regulatory T cell depletion contributes to the development of antiviral immunity, ultimately resulting in the resolution of type 1 inflammation.

Frequency of CD45RO+ subset in CD4+CD25(high) regulatory T cells associated with progression of hepatocellular carcinoma

The purpose of this study was to assess the properties of CD4+CD25(high/low/negative) T cell subsets and analyze their relation with dendritic cells (DCs) in patients with hepatocellular carcinoma (HCC). In HCC patients, the prevalence of CD45RO+ cells in CD4+CD25(high) T cells was increased and associated with higher frequencies of plasmacytoid DCs. Larger proportions of this T cell subset were detected in the patients with larger tumor burdens. These results suggest that increased frequencies of the CD45RO+ subset in CD4+CD25(high) Tregs in HCC patients may establish the immunosuppressive environment cooperatively with tolerogenic plasmacytoid DCs to promote disease progression of liver cancer.

Dendritic cells in hepatitis C infection: can they (help) win the battle?

Infection with hepatitis C virus (HCV) is a public health problem; it establishes a chronic course in ~85% of infected patients and increases their risk for developing liver cirrhosis, hepatocellular carcinoma, and significant extrahepatic manifestations. The mechanisms of HCV persistence remain elusive and are largely related to inefficient clearance of the virus by the host immune system. Dendritic cells (DCs) are the most efficient inducers of immune responses; they are capable of triggering productive immunity and maintaining the state of tolerance to self- and non-self antigens. During the past decade, multiple research groups have focused on DCs, in hopes of unraveling an HCV-specific DC signature or DC-dependent mechanisms of antiviral immunity which would lead to a successful HCV elimination strategy. This review incorporates the latest update in the current status of knowledge on the role of DCs in anti-HCV immunity as it relates to several challenging questions: (a) the phenotype and function of diverse DC subsets in HCV-infected patients; (b) the characteristics of non-human HCV infection models from the DCs' point of view; (c) how can in vitro systems, ranging from HCV protein- or peptide-exposed DC to HCV protein-expressing DCs, and in vivo systems, ranging from HCV protein-expressing transgenic mice to HCV-infected non-human primates, be employed to dissect the role of DCs in triggering/maintaining a robust antiviral response; and (d) the prospect of DC-based strategy for managing and finding a cure for HCV infection.

Hepatitis C virus modulates human monocyte-derived dendritic cells

This study is to examine the monocyte-derived dendritic cell (DC) response to hepatitis C virus (HCV) in a cell culture system. Adherence-derived DCs were incubated with various titres of JFH-1 (HCV genotype 2a), generated from transfected Huh 7.5 cells or co-incubated with Newcastle disease virus (NDV). Infection and the type 1 interferon (IFN) response were assessed by real-time reverse transcriptase-polymerase chain reaction, morphology by light microscopy and immunophenotype by flow cytometry. Our data demonstrated no viral replication or particle release from DC after HCV infection. Morphologically, monocytes showed a tendency to shift to immature DCs when cultured with HCV, when compared with control monocytes. This shift was confirmed by flow cytometry and appeared to be related to viral titres. There was also an increase in immature DC numbers. HCV infection induced IFNβ expression in DCs, and the amount seemed to be inversely correlated with viral titres indicating that HCV has the capacity to negatively regulate such cells. However, IFNα does not appear to be affected by direct contact with the virus. A strong IFNβ signal induced by NDV in DC was substantially diminished by HCV. HCV negatively affects the maturation of DCs and suppresses the type 1 IFN response of DC. Our results suggest a mechanism of viral evasion of host immunity.

Altered chemotactic response of myeloid and plasmacytoid dendritic cells from patients with chronic hepatitis C: role of alpha interferon

Dendritic cell (DC) frequencies in the blood of patients with chronic hepatitis C virus (HCV) infection have been shown to be reduced significantly compared with those in healthy individuals. There is a further reduction of circulating myeloid DCs (MDCs) and plasmacytoid DCs (PDCs) in HCV patients receiving alpha interferon (IFN-alpha)-based antiviral therapy. Altered homing behaviour of DCs may be a possible mechanism for their 'loss' in peripheral blood in these clinical conditions. Systemic chemokine levels were measured by ELISA. Phenotypes and migratory properties of MDCs and PDCs from HCV patients were analysed by flow cytometry and chemotaxis assay. Compared with healthy controls, HCV patients had increased serum levels of inflammatory and constitutively expressed chemokines. Spontaneously generated MDCs from HCV patients were less mature, and both MDCs and PDCs showed intrinsic activation of receptors for inflammatory chemokines, thus suggesting an increased propensity to migrate towards inflammatory sites. IFN-alpha treatment in vitro induced MDC maturation and skewed the migratory response of both MDCs and PDCs towards chemokines expressed constitutively in secondary lymphoid organs. In conclusion, our results hint at altered homing behaviour of DCs during chronic HCV infection. IFN-alpha therapy may redirect DC migration from inflamed hepatic portal areas towards secondary lymphoid tissue.

Hla-Cw7 allele as predictor of favorable therapeutic response to interferon-alpha in patients with chronic hepatitis C

AIM

To evaluate the association between human leukocyte antigens (HLA) class I and therapeutic response to interferon-alpha in Croatian patients with chronic hepatitis C.

METHODS

HLA-A, -B, and -C genotyping was performed in 55 patients with sustained virological response and in 57 patients without sustained virological response to interferon-alpha therapy. Patients were treated in the period from 1998-2001 with interferon-alpha at a dose of 3 million units three times a week. Patients who became negative for hepatitis C virus RNA after 12 weeks of therapy completed 48 weeks of therapy.

RESULTS

There was no association between therapeutic outcome and frequency of HLA-A, as well as of HLA-B alleles. HLA-Cw7 was significantly more frequent in patients with than those without sustained virological response (27.0% vs 6.7%; P=0.011).

CONCLUSION

In Croatian patients with chronic hepatitis C, HLA-Cw7 is the predictor of sustained virological response to interferon-alpha therapy.