Monocyte-derived dendritic cell function in chronic hepatitis C is impaired at physiological numbers of dendritic cells

Immunological Dynamics Associated with Direct-Acting Antiviral Therapies in Naive and Experimented HCV Chronic-Infected Patients

The therapeutic strategies used in the treatment of hepatitis C are essentially based on the combination of direct-acting antiviral agents (DAAs). This therapy has been shown to be very effective in relation to patient adherence to treatment and has shown high rates of sustained virological response (SVR). However, the immunological dynamics of patients infected with HCV is poorly understood. This fact led us to investigate the immune system of naive and experienced patients, who we followed before the therapy and three months after the end of treatment. In this study, 35 naive and experienced Brazilian patients with chronic hepatitis C and 50 healthy donors (HD group) were studied. The analysis of the soluble immunological biomarkers was performed using the flow cytometry methodology. The SVR rate was >90% among the 35 patients. Before treatment, correlations in the naive HCV group demonstrated a mix of inflammatory response occurring with moderate correlations between chemokines, inflammatory cytokines, and Th2 profile, with a strong regulation between IL-10 and IL-17A. On the other hand, experienced patients demonstrated a poor interaction between cytokines, chemokines, and cells with a strong correlation between IL-10, IL-6, CXCL-10, and CD8⁺ besides the interactions between IFN-γ and IL-4. Furthermore, naive and experienced patients seem to have a distinct soluble biomarker profile; therefore, a long-term follow-up is needed to evaluate patients treated with DAAs.

Alcoholic liver fibrosis: detection and treatment

Alcohol consumption is one of the main risks to public health. Alcohol use disorders (AUDs) cause 80% of hepatotoxic deaths, and approximately 50% of cirrhosis is alcohol-related. The acceptable daily intake (ADI) for ethanol is 2.6 g/day, deduced from morbidity and mortality rates due to liver fibrosis. The relative risk of cirrhosis increases significantly for doses above 60 g/day for men and 20 g/day for women over a period of around 10 years. Twenty to 40% of steatosis cases will evolve into steatohepatitis/steatofibrosis, and 8 to 20% will evolve directly into liver cirrhosis. About 20 to 40% of steatohepatitis cases will evolve into cirrhosis, and 4 to 5% into hepatocellular carcinoma. This cascade of events evolves in 5 to 40 years, with the temporal variability caused by the subjects' genetic patterns and associated risk/comorbidity factors. Steatohepatitis should be considered "the rate limiting step:" usually, it can be resolved through abstinence, although for some patients, once this situation develops, it is not substantially modified by abstention and there is a risk of fibrotic evolution. Early detection of fibrosis, obtained by hepatic elastography, is a crucial step in patients with AUDs. Such strategy allows patients to be included in a detoxification program in order to achieve abstention. Drugs such as silybin, metadoxine, and adenosylmethionine can be used. Other drugs, with promising antifibrotic effects, are currently under study. In this review, we discuss clinical and pathogenetic aspects of alcohol-related liver fibrosis and present and future strategies to prevent cirrhosis.

Increased proportions of dendritic cells and recovery of IFNγ responses in HIV/HCV co-infected patients receiving ART

Dendritic cell (DC) numbers and functions can be affected by HIV and HCV disease, but the effects of antiretroviral therapy (ART) on DC and the implications of these changes are unclear. We examined circulating DC in samples from Indonesian patients beginning ART with advanced HIV disease and documented mild/moderate HCV hepatitis. Frequencies of myeloid and plasmacytoid DC increased after 6 months on ART, but frequencies of DC producing IL-12 or IFNα following stimulation with TLR agonists (CL075, CpG) did not change. IFNγ responses to CL075, HCV and other antigens rose over this period. Hence increased IFNγ responses during ART may be associated with increased DC frequencies rather than changes in their functional capacity.

Indolamine 2,3-dioxygenase expression by monocytes and dendritic cell populations in hepatitis C patients

Dendritic cells (DCs) play an important role in the induction of the primary immune response to infection. DCs may express the tryptophan-catabolizing enzyme indolamine2,3-dioxygenase (IDO), which is an inducer of immune tolerance. Because there is evidence that chronic hepatitis C virus (HCV) infection leads to functional impairment of certain DC populations, we analysed IDO expression in DCs and monocytes from chronically infected and recovered HCV patients. The IDO1 and -2 expression was increased significantly in the monocytes of chronic HCV patients but, interestingly, not in those from recovered patients. The myeloid DCs from chronically infected HCV patients also showed enhanced IDO1 expression, while no change in either IDO1 or -2 was found for plasmacytoid DCs. Up-regulation of IDO1 gene expression was confirmed by the presence of enhanced kynurenine/tryptophan ratios in the plasma from chronic HCV patients. Increased IDO1 and -2 expression was also observed in monocytes from healthy donors infected with an adapted mutant of the HCV JFH-1 strain ex vivo, confirming a direct effect of HCV infection. These changes in IDO expression could be prevented by treatment with the IDO inhibitor 1-methyl tryptophan (1-mT). Furthermore, maturation of monocyte-derived DCs from chronically infected HCV patients, as well as well as monocyte-derived DCs infected ex vivo with HCV, was impaired, but this was reversed by 1-mT treatment. This suggests that IDO inhibitors may be used to treat chronic HCV patients in vivo, in conjunction with current therapies, or to activate DCs from patients ex vivo, such that they can be administered back as a DC-based therapeutic vaccine.

Alcohol and HCV: implications for liver cancer

Liver cancers are one of the deadliest known malignancies which are increasingly becoming a major public health problem in both developed and developing countries. Overwhelming evidence suggests a strong role of infection with hepatitis B and C virus (HBV and HCV), alcohol abuse, as well as metabolic diseases such as obesity and diabetes either individually or synergistically to cause or exacerbate the development of liver cancers. Although numerous etiologic mechanisms for liver cancer development have been advanced and well characterized, the lack of definite curative treatments means that gaps in knowledge still exist in identifying key molecular mechanisms and pathways in the pathophysiology of liver cancers. Given the limited success with current therapies and preventive strategies against liver cancer, there is an urgent need to identify new therapeutic options for patients. Targeting HCV and or alcohol-induced signal transduction, or virus-host protein interactions may offer novel therapies for liver cancer. This review summarizes current knowledge on the mechanistic development of liver cancer associated with HCV infection and alcohol abuse as well as highlights potential novel therapeutic strategies.

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.

Divergent contributions of regulatory T cells to the pathogenesis of chronic hepatitis C

Hepatitis C virus, a small single-stranded RNA virus, is a major cause of chronic liver disease. Resolution of primary hepatitis C virus infections depends upon the vigorous responses of CD4(+) and CD8(+) T cells to multiple viral epitopes. Although such broad CD4(+) and CD8(+) T-cell responses are readily detected early during the course of infection regardless of clinical outcome, they are not maintained in individuals who develop chronic disease. Purportedly, a variety of factors contribute to the diminished T-cell responses observed in chronic, virus-infected patients including the induction of and biological suppression by CD4(+)FoxP3(+) regulatory T cells. Indeed, a wealth of evidence suggests that regulatory T cells play diverse roles in the pathogenesis of chronic hepatitis C, impairing the effector T-cell response and viral clearance early during the course of infection and suppressing liver injury as the disease progresses. The factors that affect the generation and biological response of regulatory T cells in chronic, hepatitis C virus-infected patients is discussed.

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.

Functional reconstitution of defective myeloid dendritic cells in chronic hepatitis C infection on successful antiviral treatment

OBJECTIVE

Poor cellular trafficking and suboptimal T-cell responses in liver, the hall marks of chronic hepatitis C virus (CHC) infection, might be attributed to defective antigen presentation. Controversy exists regarding role of myeloid dendritic cells (DCs) in CHC and response to antiviral treatment. This study examines functional status of DCs before and after completion of treatment with the aim to find any modulatory effect.

DESIGN

Frequency and functions of monocyte-derived DCs (mo-DCs) were evaluated in CHC (n = 25), before the start of therapy (CHC(0) ). These patients were then put on treatment with peg-interferon-α plus ribavirin for 24 or 48 weeks, and the mo-DC functions were evaluated after 6 months of completion of treatment (CHC(6) ) again, using multicolour flow cytometry, endocytosis assay, cytokine assay and mixed lymphocyte reaction.

RESULTS

Pre-treatment frequency of mo-DCs in CHC(0) was lower than that in healthy controls, which became close to normal in patients who achieved virological response (SVR+, n = 20) but not in non-responders (SVR-, n = 5). Pre-treatment levels of CD83, CD80 and CD86 on mo-DC in SVR(0) +, but not SVR(0) -, got upregulated after lipopolysaccharide stimulation supporting the hypothesis that DCs play deciding role in response to therapy. Post-treatment allostimulatory and phagocytosing capacity of mo-DCs in SVR+ patients indicated regain in functional capacity in these patients but not in SVR- patients.

CONCLUSIONS

Our results indicate that DCs in CHC patients exhibiting mature and functional phenotype prior to therapy achieve sustained virological response suggesting that functional modulation of defective DCs is directly associated with successful response to therapy.

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.

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.

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.

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.

Increased immunopotency of monocyte derived dendritic cells from patients with optic neuritis is inhibited in vitro by simvastatin

Multiple sclerosis (MS) is an autoimmune disease where myelin-reactive lymphocytes and their activation depend on interactions with antigen presenting cells (APCs). Dendritic cells (DC) are professional APCs dependent on maturation to attain full T-cell priming capacity. The immunomodulatory properties of simvastatin influence the function of both T cells and APCs and could thus be a potential therapy for MS. The phenotype of myeloid DC in untreated patients with monosymptomatic optic neuritis (ON) was determined by flow cytometry and the impact of simvastatin on the function of myeloid DC derived from peripheral blood mononuclear cells (PBMC) was analysed in vitro. DC from ON patients had more mature phenotype compared with healthy controls (HC). Particularly the fraction of DC expressing CD1a and CD80 was significantly higher in ON than in HC (P<0.05). Addition of 10 muMu simvastatin significantly inhibited the maturation of DC in the ON group. Furthermore, ON derived DC induced stronger T-cell proliferation in the mixed leukocyte reaction (MLR), and simvastatin solely inhibited this proliferation of T-cells in the ON group and not in HC. In conclusion DC from ON patients have a more mature phenotype and an increased stimulatory capacity. Simvastatin has an inhibitory effect on the differentiation and maturation of DC, and selectively reduce the T-cell proliferation induced by DC from patients with ON. The results from these in vitro assays suggest potential beneficial inhibitory effects of Simvastatin in the inflammation in ON and early MS, but we need more clinical trials to confirm it.

Hepatitis C and innate immunity: recent advances

Eradication of hepatitis C virus (HCV) infection requires a complex and coordinated interplay between innate and adaptive immune responses that, when it fails, leads to chronic infection. In this review, the innate immune mechanisms by which HCV is sensed and by which HCV undermines host defense are discussed. The critical role of dendritic cells in antigen presentation and T-cell activation in addition to type I interferon production and interference of HCV with innate immune cell functions are reviewed. Finally, current and emerging therapeutic approaches targeting innate immune pathways are evaluated.