Monocyte derived dendritic cells retain their functional capacity in patients following infection with hepatitis C virus

Emerging Roles on Immunological Effect of Indoleamine 2,3-Dioxygenase in Liver Injuries

Indoleamine 2,3-dioxygenase (IDO) is one of the initial rate-limiting enzymes of the kynurenine pathway (KP), which causes immune suppression and induction of T cell anergy. It is associated with the imbalance of immune homeostasis in numerous diseases including cancer, chronic viral infection, allergy, and autoimmune diseases. Recently, IDO has extended its role to liver field. In this review, we summarize the dysregulation and potentials of IDO in the emerging field of liver injuries, as well as current challenges for IDO targets. In particular, we discuss unexpected conclusions against previous work published. IDO is induced by pro-inflammatory cytokines in liver dysfunction and exerts an immunosuppressive effect, whereas the improvement of liver injury may require consideration of multiple factors besides IDO.

High-dimensional immune phenotyping of blood cells by mass cytometry in patients infected with hepatitis C virus

OBJECTIVES

Chronic hepatitis C virus (HCV) infection affects the immune system. Whether elimination of HCV with direct-acting antivirals (DAA) restores immunity is unclear. We used mass cytometry to get a broad and in-depth assessment of blood cell populations of patients with chronic HCV before and after DAA therapy.

METHODS

Before and 12 weeks after sustained virological response (SVR12) to DAA therapy, 22 cell populations were analysed by mass cytometry in blood collected from ten healthy control individuals and 20 HCV-infected patients with (ten patients) or without (ten patients) human immunodeficiency virus (HIV) infection.

RESULTS

HCV infection altered the frequency of 14/22 (64%) blood cell populations. At baseline, the frequencies (median, interquartile range (IQR); control, HCV, HCV/HIV) of intermediate monocytes (1.2, IQR 0.47-1.46; 1.76, IQR 0.83-2.66; 0.78, IQR 0.28-1.77), non-classical monocytes (1.11, IQR 0.49-1.26; 0.9, IQR 0.18-0.99; 0.54, IQR 0.28-1.77), conventional dendritic cells type 2 (0.55, IQR 0.35-0.59; 0.31, IQR 0.16-0.38; 0.19, IQR 0.11-0.36) and CD56^dim natural killer cells (8.08, IQR 5.34-9.79; 4.72, IQR 2.59-6.05) 3.61, IQR 2.98-5.07) were reduced by 35% to 65%, particularly in HCV/HIV co-infected patients. In contrast, activated double-negative T cells (0.07, IQR 0.06-0.10; 0.10, IQR 0.09-0.19; 0.19, IQR 0.12-0.25), activated CD4 T cells (0.28, IQR 0.21-0.36; 0.56, IQR 0.33-0.77; 0.40, IQR 0.22-0.53) and activated CD8 T cells (0.23, IQR 0.14-0.42; 0.74, IQR 0.30-1.65; 0.80, IQR 0.58-1.16) were increased 1.4 to 3.5 times. Upon stimulation with Toll-like receptor ligands, the expression of cytokines was up-regulated in 7/9 (78%) and 17/19 (89%) of the conditions in HCV- and HCV/HIV-infected patients, respectively. Most alterations persisted at SVR12.

CONCLUSIONS

Chronic HCV and HCV/HIV infections induce profound and durable perturbations of innate and adaptive immune homeostasis.

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.

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.

Monocyte-derived dendritic cells from cirrhotic patients retain similar capacity for maturation/activation and antigen presentation as those from healthy subjects

Few studies have investigated the impact of liver cirrhosis on dendritic cell function. The purpose of this study was to compare the activation and antigen-presentation capacity of monocyte-derived dendritic cells (MoDC) from cirrhotic patients (CIR) relative to healthy donors (HD). MoDC from CIR and HD were matured, phenotyped, irradiated and pulsed with 15mer peptides for two hepatocellular carcinoma-related antigens, alphafetoprotein and glypican-3, then co-cultured with autologous T-cells. Expanded T-cells were evaluated by interferon-gamma ELISPOT and intracellular staining. 15 CIR and 7 HD were studied. While CD14+ monocytes from CIR displayed enhanced M2 polarization, under MoDC-polarizing conditions, we identified no significant difference between HD and CIR in maturation-induced upregulation of co-stimulation markers. Furthermore, no significant differences were observed between CIR and HD in subsequent expansion of tumor antigen-specific IFNγ+ T-cells.

CONCLUSION

MoDCs isolated from cirrhotic individuals retain similar capacity for in vitro activation, maturation and antigen-presentation as those from healthy donors.

Contradictory immune response in post liver transplantation hepatitis B and C

Hepatitis B and C often progress to decompensated liver cirrhosis requiring orthotopic liver transplantation (OLT). After OLT, hepatitis B recurrence is clinically controlled with a combination of hepatitis B immunoglobulin (HBIG) and nucleos(t)ide analogues. Another approach is to induce self-producing anti-hepatitis B virus (HBV) antibodies using a HBV envelope antigen vaccine. Patients who had not been HBV carriers such as acutely infected liver failure or who received liver from HBV self-limited donor are good candidate. For chronic HBV carrier patients, a successful response can only be achieved in selected patients such as those treated with experimentally reduced immunosuppression protocols or received an anti-HBV adaptive memory carrying donor liver. Hepatitis C virus (HCV) reinfects transplanted livers at a rate of >90%. HCV reinfected patients show different severities of hepatitis, from mild and slowly progressing to severe and rapidly progressing, possibly resulting from different adaptive immune responses. More than half the patients require interferon treatment, although the success rate is low and carries risks for leukocytopenia and rejection. Managing the immune response has an important role in controlling recurrent hepatitis C. This study aimed to review the adaptive immune response in post-OLT hepatitis B and C.

Dendritic cell maturation in HCV infection: altered regulation of MHC class I antigen processing-presenting machinery

BACKGROUND & AIMS

Modulation of dendritic cell (DC) function has been theorized as one of the mechanisms used by hepatitis C virus (HCV) to evade the host immune response and cause persistent infection.

METHODS

We used a range of cell and molecular biology techniques to study DC subsets from uninfected and HCV-infected individuals.

RESULTS

We found that patients with persistent HCV infection have lower numbers of circulating myeloid DC and plasmacytoid DC than healthy controls or patients who spontaneously recovered from HCV infection. Nonetheless, DC from patients with persistent HCV infection display normal phagocytic activity, typical expression of the class I and II HLA and co-stimulatory molecules, and conventional cytokine production when stimulated to mature in vitro. In contrast, they do not display the strong switch from immunoproteasome to standard proteasome subunit expression and the upregulation of the transporter-associated proteins following stimulation, which were instead observed in DC from uninfected individuals. This different modulation of components of the HLA class I antigen processing-presenting machinery results in a differential ability to present a CD8(+) T cell epitope whose generation is dependent on the LMP7 immunoproteasome subunit.

CONCLUSIONS

Overall, these findings establish that under conditions of persistent HCV antigenemia, HLA class I antigen processing and presentation are distinctively regulated during DC maturation.

Association of MRC-1 and IL-28B with the treatment outcome of hepatitis C: a case control study

BACKGROUND

The aim of this study was to evaluate whether polymorphisms of the mannose receptor C type 1 (MRC-1) and interleukin 28B (IL-28B) genes are associated with the treatment outcome of patients infected with hepatitis C virus genotypes 1 and 2 (HCV-1 and HCV-2, respectively) who are treated with peginterferon plus ribavirin (PEG-IFNα-RBV).

METHODS

We analyzed the association of the patients' sustained viral responses (SVRs) to PEG-IFNα-RBV therapy with 2 single nucleotide polymorphisms (SNPs) in MRC-1 and 3 SNPs in IL-28B. We selected patients infected with either HCV-1 (n = 265) or HCV-2 (n = 195) with or without SVR.

RESULTS

Among the MRC-1 SNPs, rs691005 was found to be associated with SVR in HCV-1-infected patients (P < 0.0001). The IL-28B rs8099917 SNP was found to be associated with SVR in HCV-1- and HCV-2-infected patients (HCV-1, P < 0.0001; HCV-2, P = 0.002), while IL-28B rs955155 and rs10853728 SNPs were found to be associated with SVR in HCV-1-infected patients (P = 0.003) and HCV-2-infected patients (P = 0.02), respectively. We also identified an interaction between MRC-1 rs691005 and IL-28B rs8099917 (P = 0.001). The C-T haplotype was shown to have a positive effect on SVR in HCV-1-infected patients (OR = 1.77, 95% CI = 1.2, 2.62), whereas the T-G haplotype was shown to have a negative effect on SVR in HCV-1-infected patients (OR = 0.28, 95% CI = 0.14, 0.58).

CONCLUSIONS

These results suggest that SNPs of IL-28B and MRC-1 can be used as genetic markers for predicting the outcome of PEG-IFNα-RBV treatment of HCV infections.

Therapeutic vaccines against hepatitis C virus

Hepatitis C virus (HCV) is a blood-borne pathogen which has chronically infected about 130-210 million people worldwide. Current standard-of-care (SoC) therapy is an inadequate and expensive treatment with more side effects. Two direct-acting antiviral agents (DAAs) (telaprevir and boceprevir) in combination with SoC therapy have been used in patients infected with HCV genotype 1. Although these drugs result in a shortening of therapy, they also have additional side effects and are expensive. In their stead, several second-generation DAAs are being investigated. What important is that all-oral, interferon (IFN)- and ribavirin-free regimens for the treatment of HCV-infected patients are now being investigated, and will be applied in the next year. Preventive measures against HCV, including vaccine development, are also now in progress. However, no therapeutic vaccine against HCV has been produced to date. An effective vaccine should induce robust and broadly cross-reactive CD4(+), CD8(+)T-cell and neutralising antibody (NAb) responses. Current data indicate that vaccines can usually not completely prevent HCV infection but rather prevent the progression of HCV infection to chronic and persistent infection, which may be a realistic goal. This review discusses the important roles of NAbs and CD8(+)T-cells in the development of therapeutic vaccines, and summarizes some important epitopes of HCV recognized by CD8(+)T-cells and some prospective therapeutic vaccine approaches.

Dendritic cell co-stimulatory and co-inhibitory markers in chronic HCV: an Egyptian study

AIM

To assess co-stimulatory and co-inhibitory markers of dendritic cells (DCs) in hepatitis C virus (HCV) infected subjects with and without uremia.

METHODS

Three subject groups were included in the study: group 1 involved 50 control subjects, group 2 involved 50 patients with chronic HCV infection and group 3 involved 50 HCV uremic subjects undergoing hemodialysis. CD83, CD86 and CD40 as co-stimulatory markers and PD-L1 as a co-inhibitory marker were assessed in peripheral blood mononuclear cells by real-time polymerase chain reaction. Interleukin-10 (IL-10) and hyaluronic acid (HA) levels were also assessed. All findings were correlated with disease activity, viral load and fibrogenesis.

RESULTS

There was a significant decrease in co-stimulatory markers; CD83, CD86 and CD40 in groups 2 and 3 vs the control group. Co-stimulatory markers were significantly higher in group 3 vs group 2. There was a significant elevation in PD-L1 in both HCV groups vs the control group. PD-L1 was significantly lower in group 3 vs group 2. There was a significant elevation in IL-10 and HA levels in groups 2 and 3, where IL-10 was higher in group 3 and HA was lower in group 3 vs group 2. HA level was significantly correlated with disease activity and fibrosis grade in group 2. IL-10 was significantly correlated with fibrosis grade in group 2. There were significant negative correlations between co-stimulatory markers and viral load in groups 2 and 3, except CD83 in dialysis patients. There was a significant positive correlation between PD-L1 and viral load in both HCV groups.

CONCLUSION

A significant decrease in DC co-stimulatory markers and a significant increase in a DC co-inhibitory marker were observed in HCV subjects and to a lesser extent in dialysis patients.

Success of antiviral therapy in chronic hepatitis C infection relates to functional status of myeloid dendritic cells

Chronic hepatitis C infection poses a major global health predicament and appears to be potent threat to mankind. The treatment in wide use is interferon/ribavirin combination therapy which is generally effective in about 60-70 per cent of patients carrying genotype 3 and causes significant morbidity. The response to therapy is largely guided by limited number of factors such as genotype of virus, rapid virological response, ethnicity, pre-therapy viral load, etc. While involvement of host genetic factors has been a major focus of research in playing an important role in the outcome of disease, the role of immune system cannot be marginalized. Poor cellular trafficking and suboptimal T cell responses in liver, the hall marks of chronic hepatitis C virus infection, might be attributed to defective antigen presentation. Various immunological factors, both innate and adaptive, play role in the pathogenesis of the disease and become dysfunctional in active disease. Recent reports suggest the major impact of functional and numerical status of dendritic cells in deciding the fate of antiviral therapy. In this review we take a look at the involvement of dendritic cells in playing an important role in the response to therapy.

HCV viremia drives an increment of CD86 expression by myeloid dendritic cells

The host immune response, including innate and adaptive immunity, plays a critical role in determining the outcome of viral infection. Nevertheless, little is known about the exact reasons for the failure of the host immune system in controlling hepatitis C virus (HCV) infection. Impairment of dendritic cells (DCs) function is probably one of the mechanisms responsible for immune evasion of HCV. In this study, the frequency and phenotype of DCs subsets were analyzed in three groups: HCV-infected individuals who developed viral persistence (1), HCV-infected individuals who spontaneously cleared the virus (2) and HCV-seronegative uninfected subjects (3). The results showed that the frequency of DCs subsets was not statistically significant between groups. Plasmacytoid DCs circulating exhibited an immature phenotype characterized by low expression of CD86. On the other hand, CD86 expression in myeloid DCs was significantly higher in chronic infected individuals compared to healthy controls (P=0.037). A positive correlation was observed between CD86(+) myeloid DC (mDC) and HCV viral load (r=0.4121, P=0.0263). These results suggest that HCV did not have an inhibitory effect on mDC maturation and the HCV viremia drives the increase of CD86 expression in mDC. The regulation of DCs maturation and migration lies at the level of intracellular signaling. HCV can activate or block intracellular signaling pathways and alter DC function. In conclusion, the present study suggests that imbalance of DC maturation by the virus represents a mechanism of evasion of the immune system despite the fact that HCV viremia appears to exert a "stimulatory" effect on cell-surface immune phenotype.

Immunity and hepatitis C: a review

Hepatitis C virus (HCV) is a major cause of chronic hepatitis and hepatocellular carcinoma worldwide. Due to shared transmission routes, the prevalence of HCV is especially high among individuals infected with HIV. HIV uninfected individuals spontaneously clear HCV approximately 30 % of the time, while the rate of control in HIV infected individuals who subsequently acquire HCV is substantially lower. In addition, complications of HCV are more frequent in those with HIV infection, making liver disease the leading cause of non-AIDS-related death in HIV infected individuals. This review summarizes recent advances in understanding the role of the innate and adaptive immune responses to HCV in those with and without HIV. Further defining the interaction between hepatitis C and the host immune system will potentially reveal insights into HCV pathogenesis and the host's ability to prevent persistent infection, as well as direct the development of vaccines.

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

Hepatitis C virus (HCV) is a small, enveloped RNA virus and a major cause of chronic liver disease. Resolution of primary HCV infections depends upon the vigorous responses of CD4⁺ and CD8⁺ T cells to multiple viral epitopes. Although such broad-based responses are readily detected early during the course of infection regardless of clinical outcome, they are not maintained in individuals who develop chronic disease. Ostensibly, a variety of factors contribute to the diminished T cell responses observed in chronic, HCV-infected patients including impaired dendritic cell function and the induction of CD4⁺FoxP3⁺ regulatory T cells. Overwhelming evidence suggests that the complex interaction of dendritic cells and regulatory T cells plays a critical role in the pathogenesis of chronic hepatitis C.

Dendritic cell-based immunity and vaccination against hepatitis C virus infection

Hepatitis C virus (HCV) has chronically infected an estimated 170 million people worldwide. There are many impediments to the development of an effective vaccine for HCV infection. Dendritic cells (DC) remain the most important antigen-presenting cells for host immune responses, and are capable of either inducing productive immunity or maintaining the state of tolerance to self and non-self antigens. Researchers have recently explored the mechanisms by which DC function is regulated during HCV infection, leading to impaired antiviral T-cell responses and so to persistent viral infection. Recently, DC-based vaccines against HCV have been developed. This review summarizes the current understanding of DC function during HCV infection and explores the prospects of DC-based HCV vaccine. In particular, it describes the biology of DC, the phenotype of DC in HCV-infected patients, the effect of HCV on DC development and function, the studies on new DC-based vaccines against HCV infection, and strategies to improve the efficacy of DC-based vaccines.

Therapeutic vaccination against chronic hepatitis C virus infection

Approximately 170 million people worldwide are chronic carriers of Hepatitis C virus (HCV). To date, there is no prophylactic vaccine available against HCV. The standard-of-care therapy for HCV infection involves a combination of pegylated interferon-α and ribavirin. This therapy, which is commonly associated with side effects, has a curative rate varying from 43% (HCV genotype 1) to 80% (HCV genotype 2). In 2011, two direct-acting antiviral agents, telaprevir and boceprevir, were approved by the US Food and drug Administration and are now being used in combination with standard-of-care therapy in selected patients infected with HCV genotype 1. Although both drugs are promising, resulting in a shortening of therapy, these drugs also induce additional side effects and have reduced efficacy in patients who did not respond to standard-of-care previously. An alternative approach would be to treat HCV by stimulating the immune system with a therapeutic vaccine ideally aimed at (i) the eradication of HCV-infected cells and (ii) neutralization of infectious HCV particles. The challenge is to develop therapeutic vaccination strategies that are either at least as effective as antiviral drugs but with lower side effects, or vaccines that, when combined with antiviral drugs, can circumvent long-term use of these drugs thereby reducing their side effects. In this review, we summarize and discuss recent preclinical developments in the area of therapeutic vaccination against chronic HCV infection. Although neutralizing antibodies have been described to exert protective immunity, clinical studies on the induction of neutralizing antibodies in therapeutic settings are limited. Therefore, we will primarily discuss therapeutic vaccines which aim to induce effective cellular immune response against HCV.

Human dendritic cells expressing hepatitis C virus core protein display transcriptional and functional changes consistent with maturation

Hepatitis C virus (HCV) causes a chronic liver infection, which may result in cirrhosis and hepatocellular carcinoma. Impairment of the maturation process in dendritic cells (DCs) may be one of the mechanisms responsible for immune evasion of HCV. The core and NS3 proteins are among the most conserved HCV proteins and play a key role in viral clearance. To evaluate the effects of these proteins on DCs, monocyte-derived immature DCs (iDCs) were transfected with in vitro transcribed (IVT) HCV core or NS3 RNA and treated with maturation factors. Neither core nor NS3 had an inhibitory effect on DC maturation; however, transfection of iDCs with IVT core RNA appeared to result in changes compatible with maturation. To investigate this in more detail, the transcriptional profiles of iDCs transfected with IVT core, NS3 or green fluorescent protein (GFP) RNA were examined using a DC-specific membrane array. Of the 288 genes on the array, 46 genes were distinctively up- or down-regulated by transfection with IVT core RNA in comparison with NS3 or GFP RNA treatments. Forty-two of these genes are involved in DC maturation. The effects of core on maturation of iDCs were confirmed with a significant increase in surface expression of CD83 and HLA-DR, a reduction of phagocytosis, as well as an increase in proliferation and IFN-γ secretion by T cells in a mixed lymphocyte reaction assay. These results show that HCV core does not have an inhibitory effect on human DC maturation, but could be a target for the immune system.

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.

Decreased IFNγ production correlates with diminished production of cytokines by dendritic cells in patients infected with hepatitis C virus and receiving therapy

Toll-like receptor (TLR) expression and the signalling pathways that lead to the production of accessory cytokines by antigen-presenting cells (APCs) both have potential to limit T-cell responses to viral antigens. Here, expression of TLR and retinoic acid inducible gene I (RIG-I) and responses evoked through these proteins were evaluated in patients chronically infected with HCV, before and during pegylated interferon-α (IFNα) and ribavirin therapy. Expression of TLR2, 3, 4, 7, 9 and RIG-I on APCs and cytokine production by DCs were measured by flow cytometry. Production of IL-12 by myeloid dendritic cells (mDCs), IFNα by plasmacytoid cells (pDCs) and IFNγ by peripheral blood mononuclear cells was measured after stimulation with TLR ligands. IFNγ ELISpot responses to HCV and CMV antigens declined on therapy. TLR and RIG-I expression on mDCs, pDCs, B cells and monocytes was either similar or higher in patients than that in controls and generally increased during therapy. Therapy impaired IL-12 and IFNα production by DCs and reduced production of IFNγ by PBMCs after stimulation with ligands for TLR3, TLR7/8, TLR9 and RIG-I. This was independent of whether patients attained a sustained virological response. HCV disease and interferon-based therapy reduced IFN-γ responses to HCV antigens and TLR agonists. This was not accompanied by reduced expression of pertinent TLR but correlated with diminished production of co-stimulatory cytokines by DCs stimulated via TLR.

Immunodominance of HLA-A2-restricted hepatitis C virus-specific CD8+ T cell responses is linked to naive-precursor frequency

The impact of naïve-precursor frequency on human virus-specific CD8(+) T cell immunodominance is not well understood. Using a recently developed major histocompatibility complex (MHC) class I tetramer enrichment protocol, we found a conserved hierarchy and a >10-fold difference in naïve-precursor frequencies across three HLA-A2-restricted hepatitis C virus (HCV)-specific epitopes. Importantly, the NS3(1406) epitope with the highest naïve-precursor frequency in healthy donors was also the most frequently targeted epitope in a large cohort of chronically HCV-infected patients, both ex vivo and after in vitro stimulation. These results indicate for the first time that immunodominance in a human viral infection is linked to naïve-precursor frequency.

Interferon-lambda serum levels in hepatitis C

BACKGROUND & AIMS

Dendritic cells (DCs) trigger adaptive immune responses and are an important source of antiviral cytokines. In hepatitis C virus (HCV) infection DC function is markedly impaired. Thus far, studies have focused on types I and II interferon (IFN). We studied IFN-lambda1 (IL-29) and IFN-lambda2/3 (IL-28A/B) serum levels in patients with different outcomes of HCV infection.

METHODS

IFN-lambdas were measured by ELISAs detecting IL-29 or IL-28A and IL-28B, respectively. Results were stratified with respect to the recently discovered rs12979860 T/C polymorphism upstream of the IL-28B gene.

RESULTS

In general IL-29 serum levels exceeded IL-28A/B at least twofold, with IL-29 and IL-28A/B levels being significantly higher in carriers of the rs12979860 C allele than in TT homozygous individuals (p<0.02). IL-29 levels were substantially lower in patients with chronic hepatitis C than in healthy controls (p=0.005) and patients with spontaneously resolved hepatitis (p=0.001). Patients with acute hepatitis C showed IL-29 levels intermediate between chronic hepatitis C and normal controls; and IL-29 serum levels were higher in patients who spontaneously resolved hepatitis C than in those who became chronic. In vitro HCV proteins NS3 and E2 directly inhibited IL-29 production in poly I:C-stimulated purified DCs.

CONCLUSIONS

Our data suggest that HCV proteins modify IFN-lambda production in DCs. Carriers of the rs12979860 C allele associated with resolution of HCV infection exhibited increased IFN-lambda levels. Moreover, high IFN-lambda levels predisposed to spontaneous resolution of HCV infection. Thus, IFN-lambdas seem to play an important role in the control of hepatitis C.

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.

Impairment of TLR7-dependent signaling in dendritic cells from chronic hepatitis C virus (HCV)-infected non-responders to interferon/ribavirin therapy

BACKGROUND AND AIM

Dendritic cell (DC) dysfunction has been suggested to play a role in the weak antiviral T-cell responsiveness observed during the course of chronic hepatitis C virus (HCV) infection. This study was undertaken to evaluate whether changes in DC functions might be related to a different therapeutic outcome in HCV-infected patients.

METHODS

Peripheral blood DCs (PBDCs) or monocyte-derived DCs (MoDCs) were obtained from chronic HCV-infected patients, sustained virologic responders (SVR) or non-responders (NR) to interferon/ribavirin therapy, and from healthy controls (HC). The frequency of BDCA-1+, BDCA-3+ or CD16+ myeloid DCs (mDCs) and BDCA-2+ plasmacytoid DCs (pDCs), as well as the expression of the costimulatory molecule CD86 in each PBDC subset, were evaluated by flow cytometry. MoDCs from single individuals were stimulated with TLR2, TLR3, TLR4, and TLR7 ligands and analyzed for CD86, CD83, CD40, CD80, and CD209 expression. Finally, mitogen-activated protein kinase (MAPK) phosphorylation of TLR7-triggered MoDCs was assessed by Western blotting.

RESULTS

NR exhibited a reduced percentage of BDCA-1+ mDCs, as well as lower levels of CD86+ cells, in both BDCA-1+ mDCs and pDCs as compared to SVR and HC. Furthermore, MoDCs from NR displayed a defective CD86 and CD83 increase and ERK1/2 or p38-MAPK phosphorylation upon TLR7-cell triggering.

CONCLUSIONS

Our data suggest that a TLR7-dependent impairment of costimulatory molecule expression caused by HCV persistence may affect DC activity in NR patients.

Hepatitis C virus NS4 protein impairs the Th1 polarization of immature dendritic cells

Dendritic cells (DCs) in chronic hepatitis C patients display impaired function, although the details remain unclear. To investigate the hepatitis C virus (HCV) protein that has the most impact on DC function, we compared five recombinant proteins and seven HCV protein genes in modulating DC phenotype and function. Immature DCs (iDCs) were established from healthy donor peripheral blood monocytes with granulocyte-macrophage colony stimulating factor (GM-CSF) and IL-4. Lipopolysaccharide was used to establish mature DCs (mDCs). Cells were then pulsed with HCV recombinant proteins or transfected with HCV plasmids and subsequently assayed for cell surface marker expression by flow cytometry. For cytokine and proliferative T-cell response analysis, DCs were cultured with autologous CD4 T cells and tuberculin purified protein derivative (PPD). Mean fluorescent intensity of CD86 was reduced in HCV protein-pulsed iDCs. Proliferative T-cell responses and Th1 cytokine concentrations were reduced with HCV nonstructural proteins (NS), particularly with HCV NS4. HCV nonstructural proteins, particularly NS4, change the iDC phenotype and reduce antigen-specific T-cell stimulatory function with Th1 cytokine reductions.

Functional changes, increased apoptosis, and diminished nuclear factor-kappaB activity of myeloid dendritic cells during chronic hepatitis C infection

Approximately 70% of patients infected with hepatitis C virus (HCV) develop chronic infections, which have been reported to be caused by impaired specific T-cell responses. Myeloid dendritic cells (mDCs) are important antigen-presenting cells that regulate T-cell responses, however their role during chronic hepatitis C (CHC) is not fully understood. In this study, we found that the ability of mDCs to stimulate T-cell responses was impaired in CHC patients. Furthermore, mDCs from CHC patients underwent apoptosis at a higher rate than mDCs from healthy donors. Nuclear factor-kappaB activity, which is critical for mDC function and apoptosis prevention, was diminished in mDCs from CHC patients. In conclusion, mDCs from CHC patients demonstrated functional changes with increased apoptosis, and diminished nuclear factor-kappaB activity. These changes may contribute to the impaired specific T-cell responses in CHC patients.

Characterization of the cellular immune response in hepatitis C virus infection

Hepatitis C virus (HCV), a hepatotropic RNA virus, is a major causative agent of chronic hepatitis, liver cirrhosis, and hepatocellular carcinomas. The host immune responses, especially cellular immune responses, play an important role in viral clearance, liver injury, and persistent HCV infection. A thorough characterization of the HCV cellular immune responses is important for understanding the interplays between host immune system and viral components, as well as for developing effective therapeutic and prophylactic HCV vaccines. Recent advances that provide better understanding the cell immune responses in HCV infection are summarized in this article.

Impaired plasmacytoid dendritic cell maturation and differential chemotaxis in chronic hepatitis C virus: associations with antiviral treatment outcomes

BACKGROUND

Dendritic cell (DC) defects may contribute to chronicity in hepatitis C virus (HCV) infection and determine response to PEG-interferon and ribavirin therapy via poor T cell stimulation. Studies to date have produced inconsistent results regarding DC maturation and function: no large study has examined DCs before and after therapy.

AIMS

We examined if DC defects in maturation and chemotaxis are present by comparing therapeutic responders to non-responders.

METHODS

We analysed peripheral DCs of 64 HCV genotype 1-infected patients from the Virahep-C study 2 weeks before and 24 weeks after therapy. We used flow cytometry to enumerate plasmacytoid DC (pDC) and myeloid DCs (mDC) and quantify expression of chemokine receptors and maturation markers. Chemotaxis was measured with an in vitro assay.

RESULTS

Pre-treatment frequencies of pDCs and mDCs were significantly lower in HCV patients than controls and successful therapy normalised pDCs. Levels of CXCR3 and CXCR4 on pDCs were higher at baseline compared to normal controls and decreased with therapy. Pre-therapy levels of co-stimulatory marker CD40 and the maturation marker CD83 were higher in pDCs of patients chronically infected with HCV compared to normal patients, and levels of both markers dropped significantly with therapy in the SVR+ group only. Other maturation markers (CD86 and CCR7) were not elevated suggesting a partially activated phenotype. Baseline chemotaxis of pDCs to CXCL12 and CXCL10 predicted failure of antiviral response and correlated with the histological activity index inflammation score.

CONCLUSIONS

Plasmacytoid DC defects exist in chronic HCV and successful antiviral therapy normalises many phenotypic and functional abnormalities.

Early viraemia clearance during antiviral therapy of chronic hepatitis C improves dendritic cell functions

Plasma and cellular HCV RNA and core antigen were tested in monocyte-derived DC (MDDC) from chronic hepatitis C patients undergoing treatment with peg-interferon alpha2b/ribavirin. DC allostimulatory capacity, HCV-specific T-cell reactivity and IL-12 production were measured at baseline and treatment week (TW)12. Using DC and autologous CD4(+)T-cells, obtained at baseline and TW12, we performed cross-over experiments to determine the relative role of DC and/or T-cells for impaired immune reactivity to HCV. HCV RNA and HCV core plasma levels had an impact on DC phenotype and allostimulatory capacity. In contrast, HCV genome/core protein, although detectable in DC from some patients had no effect on DC function. Antiviral immunity at TW12 was not improved in patients who remained HCV RNA positive, while early viraemia clearance (TW12) improved antiviral responses. The cross-over experiment revealed that changes in DC, rather than CD4(+)T cells have a major role for enhanced anti-HCV responses.

Monocyte-derived dendritic cells from HCV-infected patients transduced with an adenovirus expressing NS3 are functional when stimulated with the TLR3 ligand poly(I:C)

Dendritic cells (DC) transfected with an adenovirus encoding hepatitis C virus (HCV) NS3 protein (AdNS3) induce potent antiviral immune responses when used to immunize mice. However, in HCV infected patients, controversial results have been reported regarding the functional properties of monocyte-derived DC (MoDC), a cell population commonly used in DC vaccination protocols. Thus, with the aim of future vaccination studies we decided to characterize MoDC from HCV patients transfected with AdNS3 and stimulated with the TLR3 ligand poly(I:C). Phenotypic and functional properties of these cells were compared with those from MoDC obtained from uninfected individuals. PCR analysis showed that HCV RNA was negative in MoDC from patients after the culture period. Also, phenotypic analysis of these cells showed lower expression of CD80, CD86, and CD40, but similar expression of HLA-DR molecules as compared to MoDC from uninfected individuals. Functional assays of MoDC obtained from patients and controls showed a similar ability to activate allogeneic lymphocytes or to produce IL-12 and IL-10, although lower IFN-alpha levels were produced by cells from HCV patients after poly(I:C) stimulation. Moreover, both groups of MoDC induced similar profiles of IFN-gamma and IL-5 after stimulation of allogeneic T-cells. Finally, migration assays did not reveal any difference in their ability to respond to CCL21 chemokine. In conclusion, MoDC from HCV patients are functional after transduction with AdNS3 and stimulation with poly(I:C). These findings suggest that these cells may be useful for therapeutic vaccination in chronic HCV infection.