Chronic hepatitis C infection blocks the ability of dendritic cells to secrete IFN-α and stimulate T-cell proliferation

Uncovering Resistance to Hepatitis C Virus Infection: Scientific Contributions and Unanswered Questions in the Irish Anti-D Cohort

Infections caused inadvertently during clinical intervention provide valuable insight into the spectrum of human responses to viruses. Delivery of hepatitis C virus (HCV)-contaminated blood products in the 70s (before HCV was identified) have dramatically increased our understanding of the natural history of HCV infection and the role that host immunity plays in the outcome to viral infection. In Ireland, HCV-contaminated anti-D immunoglobulin (Ig) preparations were administered to approximately 1700 pregnant Irish rhesus-negative women in 1977–1979. Though tragic in nature, this outbreak (alongside a smaller episode in 1993) has provided unique insight into the host factors that influence outcomes after HCV exposure and the subsequent development of disease in an otherwise healthy female population. Despite exposure to highly infectious batches of anti-D, almost 600 of the HCV-exposed women have never shown any evidence of infection (remaining negative for both viral RNA and anti-HCV antibodies). Detailed analysis of these individuals may shed light on innate immune pathways that effectively block HCV infection and potentially inform us more generally about the mechanisms that contribute to viral resistance in human populations.

Impact of infection on transplantation tolerance

Allograft tolerance is the ultimate goal of organ transplantation. Current strategies for tolerance induction mainly focus on inhibiting alloreactive T cells while promoting regulatory immune cells. Pathogenic infections may have direct impact on both effector and regulatory cell populations, therefore can alter host susceptibility to transplantation tolerance induction as well as impair the quality and stability of tolerance once induced. In this review, we will discuss existing data demonstrating the effect of infections on transplantation tolerance, with particular emphasis on the role of the stage of infection (acute, chronic, or latent) and the stage of tolerance (induction or maintenance) in this infection-tolerance interaction. While the deleterious effect of acute infection on tolerance is mainly driven by proinflammatory cytokines induced shortly after the infection, chronic infection may generate exhausted T cells that could in fact facilitate transplantation tolerance. In addition to pathogenic infections, commensal intestinal microbiota also has numerous significant immunomodulatory effects that can shape the host alloimmunity following transplantation. A comprehensive understanding of these mechanisms is crucial for the development of therapeutic strategies for robustly inducing and stably maintaining transplantation tolerance while preserving host anti-pathogen immunity in clinically relevant scenarios.

Mononuclear phagocyte system in hepatitis C virus infection

The mononuclear phagocyte system (MPS), which consists of monocytes, dendritic cells (DCs), and macrophages, plays a vital role in the innate immune defense against pathogens. Hepatitis C virus (HCV) is efficient in evading the host immunity, thereby facilitating its development into chronic infection. Chronic HCV infection is the leading cause of end-stage liver diseases, liver cirrhosis, and hepatocellular carcinoma. Acquired immune response was regarded as the key factor to eradicate HCV. However, innate immunity can regulate the acquired immune response. Innate immunity-derived cytokines shape the adaptive immunity by regulating T-cell differentiation, which determines the outcome of acute HCV infection. Inhibition of HCV-specific T-cell responses is one of the most important strategies for immune system evasion. It is meaningful to illustrate the role of innate immune response in HCV infection. With the MPS being the important factor in innate immunity, therefore, understanding the role of the MPS in HCV infection will shed light on the pathophysiology of chronic HCV infection. In this review, we outline the impact of HCV infection on the MPS and cytokine production. We discuss how HCV is detected by the MPS and describe the function and impairment of MPS components in HCV infection.

Innate and Adaptive Immune Responses in Chronic HCV Infection

Hepatitis C virus (HCV) remains a public health problem of global importance, even in the era of potent directly-acting antiviral drugs. In this chapter, I discuss immune responses to acute and chronic HCV infection. The outcome of HCV infection is influenced by viral strategies that limit or delay the initiation of innate antiviral responses. This delay may enable HCV to establish widespread infection long before the host mounts effective T and B cell responses. HCV's genetic agility, resulting from its high rate of replication and its error prone replication mechanism, enables it to evade immune recognition. Adaptive immune responses fail to keep up with changing viral epitopes. Neutralizing antibody epitopes may be hidden by decoy structures, glycans, and lipoproteins. T cell responses fail due to changing epitope sequences and due to exhaustion, a phenomenon that may have evolved to limit immune-mediated pathology. Despite these difficulties, innate and adaptive immune mechanisms do impact HCV replication. Immune-mediated clearance of infection is possible, occurring in 20-50% of people who contract the disease. New developments raise hopes for effective immunological interventions to prevent or treat HCV infection.

Defining a standard and weighted mathematical index for maturation of dendritic cells

The concept of dendritic cell (DC) maturation generally refers to the changes in morphology and function of DCs. Conventionally, DC maturity is based on three criteria: loss of endocytic ability, gain of high-level capacity to present antigens and induce proliferation of T cells, and mobility of DCs toward high concentrations of CCL19. Impairment of DC maturation has been suggested as the main reason for infectivity or chronicity of several infectious agents. In the case of hepatitis C virus, this has been a matter of controversy for the last two decades. However, insufficient attention has been paid to the method of ex vivo maturation as the possible source of such controversies. We previously reported striking differences between DCs matured with different methods, so we propose the use of a standard quantitative index to determine the level of maturity in DCs as an approach to compare results from different studies. We designed and formulated a mathematically calculated index to numerically define the level of maturity based on experimental data from ex vivo assays. This introduces a standard maturation index (SMI) and weighted maturation index (WMI) based on strictly standardized mean differences between different methods of generating mature DCs. By calculating an SMI and a WMI, numerical values were assigned to the level of maturity achieved by DCs matured with different methods. SMI and WMI could be used as a standard tool to compare diversely generated mature DCs and so better interpret outcomes of ex vivo and in vivo studies with mature DCs.

Current progress in host innate and adaptive immunity against hepatitis C virus infection

Hepatitis C virus (HCV) infects more than 170 million people worldwide and is the main cause of chronic hepatitis, liver cirrhosis and hepatocellular carcinoma. Although the newly developed direct-acting antivirals (DAAs) have transformed the treatment of HCV infection, controlling HCV infection on a global scale remains a challenge because of the high cost, low resistance barrier of DAAs and lack of HCV vaccine. The host immune responses associated with HCV infection, especially HCV-specific T cellular immunity, determine the outcome of HCV infection: either acute or chronic infection. It is important to fully interpret the immunopathogenesis of HCV infection and consequently to exploit effective strategies to eliminate HCV. Here, we review the current progress in HCV immunology, which will deepen our understanding of the spectrum of HCV infection and immunity in humans.

Hepatitis C virus drives increased type I interferon-associated impairments associated with fibrosis severity in antiretroviral treatment-treated HIV-1-hepatitis C virus-coinfected individuals

BACKGROUND

Viral coinfections might contribute to the increased immune activation and inflammation that persist in antiretroviral treatment (ART)-treated HIV-1 patients. We investigated whether the hepatitis C virus (HCV) coinfection contributes to such alterations by impairing the plasmacytoid dendritic cell (pDC) IFNα/TLR7 pathway in a highly homogeneous group of ART-treated HIV-1-HCV-coinfected patients.

METHODS

Twenty-nine HIV-1-infected patients with fully suppressive ART were included, 15 of whom being HCV-coinfected with mild-to-moderate fibrosis and matched for their HIV-1 disease, and 13 control healthy donors. Cellular activation, plasma levels of inflammatory cytokines and pDC transcriptome associated with IFNα/TLR7 pathway were characterized.

RESULTS

Higher plasma levels of type-I interferon (IFN)-associated cytokines [interferon gamma-induced protein 10 (IP-10), MIP-1β, IL-8 and IFN-inducible T-cell alpha chemoattractant) were observed in HIV-1-HCV-coinfected than in HIV-1-monoinfected patients (P = 0.0007, 0.028, 0.028 and 0.035, respectively). The pDCs and T cells displayed a more exhausted (LAG-3+ and CD57+, respectively) phenotype. The pDC IFNα pathway (defined by phosphorylated STAT1 expression) was constitutively activated in all patients, irrespective of HCV coinfection. Expression of interferon-stimulated genes (ISGs) EI2AK2, ISG15, Mx1 and IFI44 was increased in pDCs from HIV-1-HCV-coinfected individuals and was correlated with fibrosis score (Fibroscan, www.echosens.com, Paris, France and aspartate-aminotransferase/platelet-ratio index score, P = 0.026 and 0.019, respectively). Plasma levels of IP-10, STAT1 expression in pDCs and Mx1 mRNA levels in pDCs decreased after interferon-free anti-HCV treatment.

CONCLUSION

HCV replication appears to drive increases in type-I IFN-associated inflammation and ISGs expression in pDCs, in association with fibrosis severity in ART-treated HIV-1-infected patients with mild-to-moderate fibrosis. Preliminary results indicate reduction of these alterations with earlier interferon-free anti-HCV treatment in those patients.

Common haplotypes in CD209 promoter and susceptibility to HIV-1 infection in intravenous drug users

INTRODUCTION

CD209 is a receptor expressed in the dendritic cells involved in recognition of oligosaccharides present in several pathogens with a relevant impact on human health. SNPs located in the promoter region have been associated with HIV-1 susceptibility, although this finding has not been replicated in other populations. The objective of this study is to evaluate the association of CD209 promoter haplotypes with risk of HIV-1 infection in a cohort of Spanish male intravenous drug users (IDU) infected with hepatitis C virus (HCV) and to characterize the phenotypic effects of the associated variants.

METHODS

We genotyped 4 SNPs of CD209 promoter in 295 HCV males exposed to HIV-1 infection by IDU, 165 HIV-1-infected and 130 exposed uninfected (EUI) and 142 healthy controls (HC). We have cloned the promoter variants in a reporter vector and evaluated the promoter activities in a cell culture model. CD209 mRNAs were measured in PBMC.

RESULTS

Single-marker analysis revealed no significant allelic association with the risk of HIV-1 infection by parenteral route. Nevertheless, one haplotype was significantly overrepresented in EUI compared with HIV-1 positive patients and was associated with HIV-1 status (P=0.0008; OR: 0.43). Functional experiments suggested that the protective haplotype displayed lower transcriptional activity in vitro (P<0.05) and this was correlated with lower CD209 mRNA expression in PBMC (P=0.014).

CONCLUSIONS

This study suggests that the promoter haplotypes of CD209 influence the risk of HIV-1 acquisition in IDU and that this association is correlated with the mRNA expression level.

Outcomes of Interferon/Ribavirin Therapy in Patients with HCV Defined by Expression of Plasma Soluble Human Leukocyte Antigen-G but Not IL-37

Background

Chronic hepatitis C virus (HCV) infection leads to life-threatening complications worldwide. Immunomodulation signals the response to virus clearance. The immune-suppressive molecule human leukocyte antigen-G (HLA-G) has been shown to function in inhibiting both innate and adaptive immune responses. The objective of this study was to investigate the expression of HLA-G and IL-37 in sustained virological response (SVR) and non-SVR HCV-positive patients before and after complete treatment with a combination of pegylated interferon (IFN) and ribavirin (RBV).

Material/Methods

Our study included 132 chronic hepatitis C patents who received combined therapy with IFN-α and RBV. Both SVR and non-SVR patients were included. The end-of-treatment response was defined as undetectable HCV RNA at week 48. Patients with end-of-treatment response were detected by HCV RNA at 24 weeks after therapy. The expression levels of HLA-G and IL-37 at the end and 24 weeks after treatment were detected by ELISA.

Results

Plasma HLA-G and IL-37 were significantly increased in HCV-infected patients compared with healthy individuals before treatment. Furthermore, HLA-G in SVR patients was noticeably decreased after treatment, while HLA-G in non-SVR patients had no changes after treatment. Additionally, both in SVR and non-SVR patients, the expression of IL-37 was remarkably reduced compared with baseline after treatment.

Conclusions

These findings suggest that elevation of HLA-G and IL-37 in HCV may play an important role in response to combined therapy with IFN-α and RBV. Monitoring the expression of HLA-G during therapy could contribute to adjusting the treatment program of HCV-infected patients.

Immunopathogenesis of Hepatitis C Virus Infection

Despite advances in therapy, hepatitis C virus infection remains a major global health issue with 3 to 4 million incident cases and 170 million prevalent chronic infections. Complex, partially understood, host-virus interactions determine whether an acute infection with hepatitis C resolves, as occurs in approximately 30% of cases, or generates a persistent hepatic infection, as occurs in the remainder. Once chronic infection is established, the velocity of hepatocyte injury and resultant fibrosis is significantly modulated by immunologic as well as environmental factors. Immunomodulation has been the backbone of antiviral therapy despite poor understanding of its mechanism of action.

Dendritic cells: The warriors upfront-turned defunct in chronic hepatitis C infection

Hepatitis C virus (HCV) infection causes tremendous morbidity and mortality with over 170 million people infected worldwide. HCV gives rise to a sustained, chronic disease in the majority of infected individuals owing to a failure of the host immune system to clear the virus. In general, an adequate immune response is elicited by an efficient antigen presentation by dendritic cells (DCs), the cells that connect innate and adaptive immune system to generate a specific immune response against a pathogen. However, HCV seems to dysregulate the activity of DCs, making them less proficient antigen presenting cells for the optimal stimulation of virus-specific T cells, hence interfering with an optimal anti-viral immune response. There are discordant reports on the functional status of DCs in chronic HCV infection (CHC), from no phenotypic or functional defects to abnormal functions of DCs. Furthermore, the molecular mechanisms behind the impairment of DC function are even so not completely elucidated during CHC. Understanding the mechanisms of immune dysfunction would help in devising strategies for better management of the disease at the immunological level and help to predict the prognosis of the disease in the patients receiving antiviral therapy. In this review, we have discussed the outcomes of the interaction of DCs with HCV and the mechanisms of DC impairment during HCV infection with its adverse effects on the immune response in the infected host.

Bovine viral diarrhea virus type 2 in vivo infection modulates TLR4 responsiveness in differentiated myeloid cells which is associated with decreased MyD88 expression

Symptoms of bovine viral diarrhea virus (BVDV) infection range from subclinical to severe, depending on strain virulence. Several in vitro studies showed BVDV infection impaired leukocyte function. Fewer studies have examined the effects of in vivo BVDV infection on monocyte/macrophage function, especially with strains of differing virulence. We characterized cytokine production by bovine myeloid cells isolated early or late in high (HV) or low virulence (LV) BVDV2 infection. Given BVDV infection may enhance susceptibility to secondary bacterial infection, LPS responses were examined as well. Monocytes from HV and LV infected calves produced higher levels of cytokines compared to cells from controls. In contrast, monocyte-derived macrophage cytokine levels were generally reduced. Modulated cytokine expression in HV BVDV2 macrophages was associated with decreased MyD88 expression, likely due to its interaction with viral NS5A. These data and those of others, suggest that certain Flaviviridae may have evolved strategies for subverting receptor signaling pathways involving MyD88.

Chronic ethanol diet increases regulatory T-cell activity and inhibits hepatitis C virus core-specific cellular immune responses in mice

AIM

Chronic ethanol consumption is associated with persistent hepatitis C viral (HCV) infection. This study explores the role of the host cellular immune response to HCV core protein in a murine model and how chronic ethanol consumption alters T-cell regulatory (Treg) populations.

METHODS

BALB/c mice were fed an isocaloric control or ethanol liquid diet. Dendritic cells (DC) were isolated after expansion with a hFl3tL-expression plasmid and subsequently transfected with HCV core protein. Core-containing DC (1 × 10(6) ) were s.c. injected (×3) in mice every 2 weeks. Splenocytes from immunized mice were isolated and stimulated with HCV core protein to measure generation of viral antigen-specific Treg, as well as secretion of interleukin (IL)-2, tumor necrosis factor (TNF)-α and IL-4. Cytotoxicity was measured by lactate dehydrogenase release from HCV core-expressing syngeneic SP2/19 myeloma cells.

RESULTS

Splenocytes from mice immunized with ethanol-derived and HCV core-loaded DC exhibited significantly lower in vitro cytotoxicity compared to mice immunized with HCV core-loaded DC derived from isocaloric pair-fed controls. Stimulation with HCV core protein triggered higher IL-2, TNF-α and IL-4 release in splenocytes following immunization with core-loaded DC derived from controls as compared to chronic ethanol-fed mice. Splenocytes derived from mice immunized with core-loaded DC isolated from ethanol-fed mice exhibited a significantly higher CD25(+) FOXP3(+) and CD4(+) FOXP3(+) Treg population.

CONCLUSION

These results suggest that immunization with HCV core-containing DC from ethanol-fed mice induces an increase in the CD25(+) FOXP3(+) and CD4(+) FOXP3(+) Treg population and may suppress HCV core-specific CD4(+) and CD8(+) T-cell immune responses.

Functions of liver natural killer cells are dependent on the severity of liver inflammation and fibrosis in chronic hepatitis C

During chronic hepatitis C virus (HCV) infection, the role of intra-hepatic (IH) natural killer (NK) cells is still controversial. To clarify their functions, we investigated anti-viral and cytotoxic activity of NK cells in human fresh liver biopsies. We compared the functions of IH-NK cells in HCV-infected and NASH patients in physiological conditions as well as after stimulation using flow cytometric and immunohistochemical analyses. Interestingly, few IH-NK cells produced anti-viral cytokine IFN-γ in HCV-infected patients similarly as in non-infected individuals. Spontaneous degranulation activity was extremely low in peripheral NK cells compared to IH-NK cells, and was significantly higher in IH-NK cells from HCV-infected patients compared to non-infected individuals. Immunohistochemical analysis revealed that perforin granules were polarized at the apical pole of IH-NK cells. The presence of CD107a and perforin in IH-NK cells demonstrated that NK cells exerted a cytolytic activity at the site of infection. Importantly, IH-NK cell functions from HCV-infected patients were inducible by specific exogenous stimulations. Upon ex vivo K562 target cell stimulations, the number of degranulating NK cells was significantly increased in the pool of IH-NK cells compared to circulating NK cells. Interestingly, after stimulation, the frequency of IFN-γ-producing IH-NK cells in HCV-infected patients was significantly higher at early stage of inflammation whereas the spontaneous IH-NK cell degranulation activity was significantly impaired in patients with highest inflammation and fibrosis Metavir scores. Our study highlights that some IH-NK cells in HCV-infected patients are able to produce INF-γ and degranulate and that those two activities depend on liver environment including the severity of liver injury. Thus, we conclude that critical roles of IH-NK cells have to be taken into account in the course of the liver pathogenesis associated to chronic HCV infection.

HCV-specific immune responses induced by CIGB-230 in combination with IFN-α plus ribavirin

AIM: To analyze hepatitis C virus (HCV)-specific immune responses in chronically infected patients under triple therapy with interferon-α (IFN-α) plus ribavirin and CIGB-230.

METHODS: CIGB-230 was administered in different schedules with respect to IFN-α plus ribavirin therapy. Paired serum and peripheral blood mononuclear cells (PBMC) samples from baseline and end of treatment were analyzed. The HCV-specific humoral response was tested by enzyme-linked immunosorbent assay, neutralizing antibodies were evaluated by cell culture HCV neutralization assays, PBMC proliferation was assayed by carboxyfluorescein succinimidyl ester staining and IFN-γ secretion was assessed by enzyme-linked immunospot. Data on virological and histological response and their association with immune variables are also provided.

RESULTS: From week 12 to week 48, all groups of patients showed a significant reduction in mean leukocyte counts. Statistically significant reductions in antibody titers were frequent, but only individuals immunized with CIGB-230 as early add-on treatment sustained the core-IgG response, and the neutralizing antibody response was enhanced only in patients receiving CIGB-230. Cell-mediated immune responses also tended to decline, but significant reductions in IFN-γ secretion and total absence of core-specific lymphoproliferation were exclusive of the control group. Only CIGB-230-immunized individuals showed de novo induced lymphoproliferative responses against the structural antigens. Importantly, it was demonstrated that the quality of the CIGB-230-induced immune response depended on the number of doses and timing of administration in relation to the antiviral therapy. Specifically, the administration of 6 doses of CIGB-230 as late add-on to therapy increased the neutralizing antibody activity and the de novo core-specific IFN-γ secretion, both of which were associated with the sustained virological response.

CONCLUSION: CIGB-230, combined with IFN-α-based therapy, modifies the immune response in chronic patients. The study provides evidence for the design of more effective therapeutic vaccine interventions against HCV.

Hepatitis C virus targets the interferon-α JAK/STAT pathway by promoting proteasomal degradation in immune cells and hepatocytes

JAK/STAT signalling is essential for anti-viral immunity, making IFN-α an obvious anti-viral therapeutic. However, many HCV+ patients fail treatment, indicating that the virus blocks successful IFN-α signalling. We found that STAT1 and STAT3 proteins, key components of the IFN-α signalling pathway were reduced in immune cells and hepatocytes from HCV infected patients, and upon HCV expression in Huh7 hepatocytes. However, STAT1 and STAT3 mRNA levels were normal. Mechanistic analysis revealed that in the presence of HCV, STAT3 protein was preferentially ubiquitinated, and degradation was blocked by the proteasomal inhibitor MG132. These findings show that HCV inhibits IFN-α responses in a broad spectrum of cells via proteasomal degradation of JAK/STAT pathway components.

Elevated circulating osteoprotegerin and reduced matrix-metalloprotease-9 in post-menopausal women with chronic Hepatitis C virus infection

The failure of the immune response to clear the Hepatitis C virus (HCV) results in chronic inflammation that leads to liver cirrhosis. In general, women have a better prognosis than men and this may be associated with increased levels of anti-inflammatory mediators that are positively regulated by female sex hormones. Our aim was to determine if a cohort of Irish women who acquired infection through administration of HCV genotype 1b-contaminated anti-D immunoglobulin from a single source, had altered levels of circulating cytokine levels compared to women who spontaneously resolved infection, men with HCV infection or age-matched healthy controls. Twenty post-menopausal women and 20 men with chronic HCV infection (genotype 1), 20 post-menopausal women who resolved infection and age and sex-matched controls were recruited for the study. Levels of circulating cytokines were assessed by ELISA. Circulating IL-6, Oncostatin-M, TNF-α, CXCL10, CCL18, VEGF and GM-CSF did not differ between groups. Both men and women with HCV had significantly elevated levels of circulating Osteoprotegerin (OPG). However, male but not female HCV patients had elevated levels of circulating Matrix Metalloprotease-9 (MMP-9). An increased OPG: MMP-9 ratio in the circulation of females compared to males with chronic HCV may help protect against HCV-associated liver disease and explain the slow progress of liver disease in this cohort.

Systems kinomics demonstrates Congo Basin monkeypox virus infection selectively modulates host cell signaling responses as compared to West African monkeypox virus

Monkeypox virus (MPXV) is comprised of two clades: Congo Basin MPXV, with an associated case fatality rate of 10%, and Western African MPXV, which is associated with less severe infection and minimal lethality. We thus postulated that Congo Basin and West African MPXV would differentially modulate host cell responses and, as many host responses are regulated through phosphorylation independent of transcription or translation, we employed systems kinomics with peptide arrays to investigate these functional host responses. Using this approach we have demonstrated that Congo Basin MPXV infection selectively down-regulates host responses as compared with West African MPXV, including growth factor- and apoptosis-related responses. These results were confirmed using fluorescence-activated cell sorting analysis demonstrating that West African MPXV infection resulted in a significant increase in apoptosis in human monocytes as compared with Congo Basin MPXV. Further, differentially phosphorylated kinases were identified through comparison of our MPXV data sets and validated as potential targets for pharmacological inhibition of Congo Basin MPXV infection, including increased Akt S473 phosphorylation and decreased p53 S15 phosphorylation. Inhibition of Akt S473 phosphorylation resulted in a significant decrease in Congo Basin MPXV virus yield (261-fold) but did not affect West African MPXV. In addition, treatment with staurosporine, an apoptosis activator resulted in a 49-fold greater decrease in Congo Basin MPXV yields as compared with West African MPXV. Thus, using a systems kinomics approach, our investigation demonstrates that West African and Congo Basin MPXV differentially modulate host cell responses and has identified potential host targets of therapeutic interest.

The affect of chronic hepatitis C infection on dendritic cell function: a summary of the experimental evidence

Chronic hepatitis C virus (HCV) infection occurs in patients who fail to mount an effective T-cell response against the virus. One hypothesis for poor anti-viral immunity in these patients is that the virus impedes the immune response by disabling dendritic cells (DCs), cells that play a key role in pathogen recognition and initiation of adaptive immunity. Initial studies in the 1990s supported this hypothesis, as they clearly demonstrated that monocyte-derived DCs obtained from patients with chronic HCV infection displayed a reduced ability to stimulate lymphocyte proliferation. However, over the last 20 years, the situation has become more ambiguous. Many studies support the initial observation of a DC defect, while others using different patient cohorts or technologies have clearly demonstrated intact DC function in patients with chronic HCV. It is likely that the true situation lies somewhere in between. Just as there is a spectrum of disease in patients with chronic HCV, DCs obtained from different patients may display different properties. It is important to reconcile these divergent findings, as a clearer understanding of how the virus affects DC function will facilitate the development of immunotherapy and therapeutic vaccination strategies for patients with chronic HCV infection.