Phenotypic and functional characterization of intrahepatic T lymphocytes during chronic hepatitis C

Immune Cell Trafficking to the Liver

The human liver is an organ with a diverse array of immunologic functions. Its unique anatomic position that leads to it receiving all the mesenteric venous blood, combined with its unique micro anatomy, allows it to serve as a sentinel for the body's immune system. Hepatocytes, biliary epithelial cells, Kupffer cells, stellate cells, and liver sinusoidal endothelial cells express key molecules that recruit and activate innate and adaptive immunity. Additionally, a diverse array of lymphoid and myeloid immune cells resides within and traffics to the liver in specific circumstances. Derangement of these trafficking mechanisms underlies the pathophysiology of autoimmune liver diseases, nonalcoholic steatohepatitis, and liver transplantation. Here, we review these pathways and interactions along with potential targets that have been identified to be exploited for therapeutic purposes.

Host-virus interactions in hepatitis B and hepatitis C infection

Hepatitis B virus (HBV) and hepatitis C virus (HCV) are among the most endemic pathogens worldwide, with more than 500 million people globally currently infected with these viruses. These pathogens can cause acute and chronic hepatitis that progress to liver cirrhosis or hepatocellular carcinoma. Both viruses utilize multifaceted strategies to evade the host surveillance system and fall below the immunological radar. HBV has developed specific strategies to evade recognition by the innate immune system and is acknowledged to be a stealth virus. However, extensive research has revealed that HBV is recognized by dendritic cells (DCs) and natural killer (NK) cells. Indoleamine-2, 3-dioxygenase is an enforcer of sequential immune reactions in acute hepatitis B, and this molecule has been shown to be induced by the interaction of HBV-infected hepatocytes, DCs, and NK cells. The interleukin-28B genotype has been reported to influence HCV eradication either therapeutically or spontaneously, but the biological function of its gene product, a type-III interferon (IFN-λ3), remains to be elucidated. Human BDCA3(+)DCs have also been shown to be a potent producer of IFN-λ3 in HCV infection, suggesting the possibility that BDCA3(+)DCs could play a key role in developing therapeutic HCV vaccine. Here we review the current state of research on immune responses against HBV and HCV infection, with a specific focus on innate immunity. A comprehensive study based on clinical samples is urgently needed to improve our understanding of the immune mechanisms associated with viral control and thus to develop novel immune modulatory therapies to cure chronic HBV and HCV infection.

Host-virus interactions in hepatitis B and hepatitis C infection

Hepatitis B virus (HBV) and hepatitis C virus (HCV) are among the most endemic pathogens worldwide, with more than 500 million people globally currently infected with these viruses. These pathogens can cause acute and chronic hepatitis that progress to liver cirrhosis or hepatocellular carcinoma. Both viruses utilize multifaceted strategies to evade the host surveillance system and fall below the immunological radar. HBV has developed specific strategies to evade recognition by the innate immune system and is acknowledged to be a stealth virus. However, extensive research has revealed that HBV is recognized by dendritic cells (DCs) and natural killer (NK) cells. Indoleamine-2, 3-dioxygenase is an enforcer of sequential immune reactions in acute hepatitis B, and this molecule has been shown to be induced by the interaction of HBV-infected hepatocytes, DCs, and NK cells. The interleukin-28B genotype has been reported to influence HCV eradication either therapeutically or spontaneously, but the biological function of its gene product, a type-III interferon (IFN-λ3), remains to be elucidated. Human BDCA3(+)DCs have also been shown to be a potent producer of IFN-λ3 in HCV infection, suggesting the possibility that BDCA3(+)DCs could play a key role in developing therapeutic HCV vaccine. Here we review the current state of research on immune responses against HBV and HCV infection, with a specific focus on innate immunity. A comprehensive study based on clinical samples is urgently needed to improve our understanding of the immune mechanisms associated with viral control and thus to develop novel immune modulatory therapies to cure chronic HBV and HCV infection.

Liver sinusoidal endothelial cells induce tolerance of autoreactive CD4+ recent thymic emigrants

The liver is a unique lymphoid organ whose microenvironment is biased towards tolerance induction. We previously found that a proportion of CD4(+) autoreactive recent thymic emigrants (RTEs) retained in the liver after thymic egress and acquired IL-10 producing capability. To investigate the tolerance of these liver persisting CD4(+) RTEs in more detail and to study the liver stromal cell types that facilitate the tolerogenic changes in young T cells, the phenotype and function of liver RTEs were further characterized and the impact of liver sinusoidal endothelial cells (LSECs) and Kupffer cells on RTEs were examined using an in vitro co-culture system. More than 70% of CD4(+) CD44(hi) RTEs in the liver acquired Foxp3(-)LAG3(+) CD49b(-) regulatory phenotype and function. But higher ratio of apoptosis with enhanced FasL and Bim expression was also found in these CD4(+) liver RTEs when compared to those in the lymph nodes and spleen. LSECs played an important role in RTEs' acquisition of tolerogenic and regulatory phenotype. These results indicate an important role of liver microenvironment in enforcing peripheral tolerance to CD4(+) thymic emigrants against self- and gut-derived antigens.

HIV virological rebounds but not blips predict liver fibrosis progression in antiretroviral-treated HIV/hepatitis C virus-coinfected patients

OBJECTIVES

Antiretroviral interruption is associated with liver fibrosis progression in HIV/hepatitis C virus (HCV) coinfection. It is not known what level of HIV viraemia affects fibrosis progression.

METHODS

We evaluated 288 HIV/HCV-coinfected cohort participants with undetectable HIV RNA (<50 HIV-1 RNA copies/mL) on two consecutive visits while on combination antiretroviral therapy (cART) without fibrosis [aspartate aminotransferase to platelet ratio index (APRI) <1.5], end-stage liver disease or HCV therapy. An HIV blip was defined as a viral load of ≥ 50 and <1000 copies/mL, preceded and followed by undetectable values. HIV rebound was defined as: (i) HIV RNA ≥ 50 copies/mL on two consecutive visits, or (ii) a single HIV RNA measurement ≥ 1000 copies/mL. Multivariate discrete-time proportional hazards models were used to assess the effect of different viraemia levels on liver fibrosis progression (APRI ≥ 1.5).

RESULTS

The mean age of the patients was 45 years, 74% were male, 81% reported a history of injecting drug use, 51% currently used alcohol and the median baseline CD4 count was 440 [interquartile range (IQR) 298, 609] cells/μL. Fifty-seven (20%) participants [12.4/100 person-years (PY); 95% confidence interval (CI) 9.2-15.7/100 PY] progressed to an APRI ≥ 1.5 over a mean 1.1 (IQR 0.6, 2.0) years of follow-up time at risk. Virological rebound [hazard ratio (HR) 2.3; 95% CI 1.1, 4.7] but not blips (HR 0.5; 95% CI 0.2, 1.1) predicted progression to APRI ≥ 1.5. Each additional 1 log10 copies/mL HIV RNA exposure (cumulative) was associated with a 20% increase in the risk of fibrosis progression (HR 1.2; 95% CI 1.0-1.3).

CONCLUSIONS

Liver fibrosis progression was associated with HIV rebound, but not blips, and with increasing cumulative exposure to HIV RNA, highlighting the importance of achieving and maintaining HIV suppression in the setting of HIV/HCV coinfection.

Overexpression of Regulatory T Cells Type 1 (Tr1) Specific Markers in a Patient with HCV-Induced Hepatocellular Carcinoma

Hepatitis C virus (HCV) is an important causative agent of liver disease, but factors that determine the resolution or progression of infection are poorly understood. In this study, we suggested that existence of immunosuppressive mechanisms, supported by regulatory T cells and especially the regulatory T cell 1 subset (Tr1), may explain the impaired immune response during infection and thus the fibrosis aggravation to hepatocellular carcinoma (HCC). Using quantitative real-time PCR, we investigated the intra-hepatic presence of Tr1 cells in biopsies from a genotype 1b infected patient followed for an 18-year period from cirrhosis to HCC. We described a significant increase of gene expression in particular for the cytokines IL-10, TGF-β, and their receptors that were perfectly correlated with an increased expression of the Tr1 specific markers (combined expression of CD4, CD18, and CD49b). This was strongly marked since the patient evolved in the pathology and could explain the failure of the treatment. In conclusion, evidence of regulatory T cell installation in the liver of chronically infected patient with cirrhosis and HCC suggests for the first time a key role for these cells in the course of HCV infection.

Reactive oxygen species delay control of lymphocytic choriomeningitis virus

Cluster of differentiation (CD)8(+) T cells are like a double edged sword during chronic viral infections because they not only promote virus elimination but also induce virus-mediated immunopathology. Elevated levels of reactive oxygen species (ROS) have been reported during virus infections. However, the role of ROS in T-cell-mediated immunopathology remains unclear. Here we used the murine lymphocytic choriomeningitis virus to explore the role of ROS during the processes of virus elimination and induction of immunopathology. We found that virus infection led to elevated levels of ROS producing granulocytes and macrophages in virus-infected liver and spleen tissues that were triggered by the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. Lack of the regulatory subunit p47phox of the NADPH oxidase diminished ROS production in these cells. While CD8(+) T cells exhibited ROS production that was independent of NADPH oxidase expression, survival and T-cell function was elevated in p47phox-deficient (Ncf1(-/-)) mice. In the absence of p47phox, enhanced T-cell immunity promoted virus elimination and blunted corresponding immunopathology. In conclusion, we find that NADPH-mediated production of ROS critically impairs the immune response, impacting elimination of virus and outcome of liver cell damage.

Effector CD8 T cell trafficking within the liver

CD8 T cells play a critical role in several pathological conditions affecting the liver, most notably viral hepatitis. Accordingly, understanding the mechanisms that modulate the intrahepatic recruitment of CD8 T cells is of paramount importance. Some of the rules governing the behavior of these cells in the liver have been characterized at the population level, or have been inferred by studying the intrahepatic behavior of other leukocyte subpopulations. In contrast to most microvascular beds where leukocyte adhesion is restricted to the endothelium of post-capillary venules, it is now becoming clear that in the liver leukocytes, including CD8 T cells, can efficiently interact with the endothelium of hepatic capillaries (i.e. the sinusoids). While physical trapping has been proposed to play an important role in leukocyte adhesion to hepatic sinusoids, there is mounting evidence that T cell recruitment to the liver is highly regulated and depends on recruitment signals that are either constitutive or induced by inflammation. We review here several specific adhesive mechanisms that have been shown to regulate CD8 T cell trafficking within the liver, as well as highlight recent data that establish platelets as key cellular regulators of intrahepatic CD8 T cell accumulation.

Liver restores immune homeostasis after local inflammation despite the presence of autoreactive T cells

The liver must keep equilibrium between immune tolerance and immunity in order to protect itself from pathogens while maintaining tolerance to food antigens. An imbalance between these two states could result in an inflammatory liver disease. The aims of this study were to identify factors responsible for a break of tolerance and characterize the subsequent restoration of liver immune homeostasis. A pro-inflammatory environment was created in the liver by the co-administration of TLR ligands CpG and Poly(I:C) in presence or absence of activated liver-specific autoreactive CD8(+) T cells. Regardless of autoreactive CD8(+) T cells, mice injected with CpG and Poly(I:C) showed elevated serum ALT levels and a transient liver inflammation. Both CpG/Poly(I:C) and autoreactive CD8(+)T cells induced expression of TLR9 and INF-γ by the liver, and an up-regulation of homing and adhesion molecules CXCL9, CXCL10, CXCL16, ICAM-1 and VCAM-1. Transferred CFSE-labeled autoreactive CD8(+) T cells, in presence of TLR3 and 9 ligands, were recruited by the liver and spleen and proliferated. This population then contracted by apoptosis through intrinsic and extrinsic pathways. Up-regulation of FasL and PD-L1 in the liver was observed. In conclusion, TLR-mediated activation of the innate immune system results in a pro-inflammatory environment that promotes the recruitment of lymphocytes resulting in bystander hepatitis. Despite this pro-inflammatory environment, the presence of autoreactive CD8(+) T cells is not sufficient to sustain an autoimmune response against the liver and immune homeostasis is rapidly restored through the apoptosis of T cells.

Impact of hepatitis B and C co-infection on health-related quality of life in HIV positive individuals

PURPOSE

Concurrent infection with HIV, hepatitis B virus (HBV), and hepatitis C virus (HCV) often occurs due to the commonality in risk factors for acquisition. Few studies have examined the effect of co-infection on health-related quality of life (HRQOL) in HIV positive individuals.

METHODS

Ontario HIV Treatment Network Cohort Study (OCS) participants who completed an annual interviewer-administered questionnaire on up to three occasions were included. Generalized estimating equations (GEE) were used to assess the impact of HBV and HCV co-infection on physical and mental HRQOL component summary scores (range 0-100) as measured by the Medical Outcomes SF-36 health survey.

RESULTS

As of March 2010, 1,223 participants had completed the questionnaire; 964 were HIV mono-infected, 128 were HIV-HBV co-infected, 112 were HIV-HCV co-infected, and 19 were HIV-HBV-HCV tri-infected. Eighty percent were male, median age 46 (IQR 40-53) years, 61% Caucasian, median CD4 count 464 (IQR 319-636) cells/mm(3), and 74% had undetectable HIV viremia. Physical HRQOL was lower in HIV-HBV and HIV-HCV co-infected individuals (49.4 (IQR 42.0-53.9) and 48.1 (IQR 36.9-52.8) vs. 51.5 (IQR 45.0-55.4); p = 0.01 and <0.0001) compared to mono-infected individuals. In the multivariable GEE model, the negative impact of HCV remained significant (-2.18; p = 0.01) after adjusting for drug use, smoking, age, and gender. Unadjusted mental HRQOL was lower in HIV-HCV co-infected individuals (44.6 (IQR 34.6-54.0) vs. 48.9 (IQR 36.8-55.9); p = 0.03) compared to mono-infected individuals but no association of mental HRQOL with either co-infection was observed in multivariable GEE models.

CONCLUSIONS

HCV appears to negatively impact physical HRQOL suggesting a greater health burden for co-infected individuals. HBV and HCV co-infections were not related to lower mental HRQOL among people living with HIV/AIDS.

CD44 participates in IP-10 induction in cells in which hepatitis C virus RNA is replicating, through an interaction with Toll-like receptor 2 and hyaluronan

The mechanisms of induction of liver injury during chronic infection with hepatitis C virus (HCV) are not well understood. Gamma interferon (IFN-γ)-inducible protein 10 (IP-10), a member of the CXC chemokine family, is expressed in the liver of chronic hepatitis C (CHC) patients and selectively recruits activated T cells to the sites of inflammation. Recently, it was shown that a low plasma concentration of IP-10 in CHC patients was closely associated with the outcome of antiviral therapy. In this study, we examined the role of the Toll-like receptor (TLR) pathway on IP-10 production in cells replicating HCV. Among the CXC chemokines, the expression of IP-10 was specifically increased in cells replicating HCV upon stimulation with conventional TLR2 ligands. The enhancement of IP-10 production upon stimulation with TLR2 ligands in cells replicating HCV induced CD44 expression. CD44 is a broadly distributed type I transmembrane glycoprotein and a receptor for the glycosaminoglycan hyaluronan (HA). In CHC patients, the expression of HA in serum has been shown to increase in accord with the progression of liver fibrosis, and HA also works as a ligand for TLR2. In the present study, IP-10 production upon HA stimulation was dependent on the expression of TLR2 and CD44, and a direct association between TLR2 and CD44 was observed. These results suggest that endogenous expression of HA in hepatocytes in CHC patients participates in IP-10 production through an engagement of TLR2 and CD44.

Clinical implications of chemokines in acute and chronic hepatitis C virus infection

Hepatitis C virus (HCV), a non-cytopathic positive-stranded RNA virus, is one of the most common causes of chronic liver diseases such as chronic hepatitis, liver cirrhosis and hepatocellular carcinoma. Upon HCV infection, the majority of patients fail to clear the virus and progress to chronic hepatitis C. Chemokines are small chemotactic cytokines that direct the recruitment of immune cells and coordinate immune responses upon viral infection. Chemokine production during acute HCV infection contributes to the recruitment of immune cells with antiviral effector functions and subsequent viral clearance. In chronic HCV infection, however, continuous production of chemokines due to persistent viral replication might result in incessant recruitment of inflammatory cells to the liver, giving rise to persistence of chronic inflammation and liver injury. In this review, we will summarize the roles of chemokines in acute and chronic settings of HCV infection and the clinical relevance of chemokines in the treatment of hepatitis C.

Adoptive transfer of splenocytes to study cell-mediated immune responses in hepatitis C infection using HCV transgenic mice

Background

Hepatitis C virus (HCV) is a major cause of chronic hepatitis and a health problem affecting over 170 million people around the world. We previously studied transgenic mice that express HCV Core, Envelope 1 and Envelope 2 proteins predominantly in the liver, resulting in steatosis, liver and lymphoid tumors, and hepatocellular carcinoma. Herein, the immune-mediated cell response to hepatitis C antigens was evaluated by adoptive transfers of carboxyfluorescein succinimidyl ester (CFSE) labelled splenocytes from HCV immunized mice into HCV transgenic mice.

Results

In comparison to non-transgenic mice, there was a significant decrease in the percentage of CFSE-labeled CD4⁺ and CD8⁺ T cells in transgenic mouse peripheral blood receiving adoptive transfers from immunized donors. Moreover, the percentage of CFSE-labeled CD4⁺ and CD8⁺ T cells were significantly higher in the spleen of transgenic and non-transgenic mice when they received splenocytes from non-immunized than from immunized mice. On the other hand, the percentages of CD4⁺ and CD8⁺ T cells in the non-transgenic recipient mouse lymph nodes were significantly higher than the transgenic mice when they received the adoptive transfer from immunized donors. Interestingly, livers of transgenic mice that received transfers from immunized mice had a significantly higher percentage of CFSE labeled T cells than livers of non-transgenic mice receiving non-immunized transfers.

Conclusions

These results suggest that the T cells from HCV immunized mice recognize the HCV proteins in the liver of the transgenic mouse model and homed to the HCV antigen expression sites. We propose using this model system to study active T cell responses in HCV infection.

Pathogenesis of HIV-HCV Coinfection

Hepatitis C virus (HCV) and HIV-1 are often harbored in the same host, establishing chronic infections typically characterized by persistent viremia. HIV-1 has deleterious effects on the course of HCV infection by increasing the rate of HCV viral persistence, quantitative HCV RNA levels, and ultimately the liver fibrosis progression rate. Conversely, HCV may blunt the effectiveness of immune reconstitution following antiretroviral therapy in HIV-infected individuals. Better understanding of the pathogenic mechanisms underlying these clinical observations may facilitate novel and effective therapeutic interventions that tackle the clinical conundrums raised by HIV/HCV coinfection.

The role of chemokines in the recruitment of lymphocytes to the liver

Chemokines direct leukocyte trafficking and positioning within tissues, thus playing critical roles in regulating immune responses and inflammation. The chemokine system is complex, involving interactions between multiple chemokines and their receptors that operate in combinatorial cascades with adhesion molecules. The involvement of multiple chemokines and chemokine receptors in these processes brings flexibility and specificity to recruitment. The hepatic vascular bed is a unique low-flow environment through which leukocytes are recruited to the liver during homeostatic immune surveillance and in response to infection or injury. The rate of leukocyte recruitment and the nature of cells recruited through the sinusoids in response to inflammatory signals will shape the severity of disease. At one end of the spectrum, fulminant liver failure results from a rapid recruitment of leukocytes that leads to hepatocyte destruction and liver failure; at the other end, diseases such as chronic hepatitis C infection may progress over many years from hepatitis to fibrosis and cirrhosis. Chronic hepatitis is characterized by a T lymphocyte-rich infiltrate and the nature and outcome of hepatitis will depend on the T cell subsets recruited, their activation and function within the liver. Different subsets of effector T cells have been described based on their secretion of cytokines and specific functions. These include Th1 and Th2 cells, and more recently Th17 and Th9 cells, which are associated with different types of immune response and which express distinct patterns of chemokine receptors that promote their recruitment under particular conditions. The effector function of these cells is balanced by the recruitment of regulatory T cells that are able to suppress antigen-specific effectors to allow resolution of immune responses and restoration of immune homeostasis. Understanding the signals that are responsible for recruiting different lymphocyte subsets to the liver will elucidate disease pathogenesis and open up new therapeutic approaches to modulate recruitment in favor of resolution rather than injury.

NOD2 ligation subverts IFN-alpha production by liver plasmacytoid dendritic cells and inhibits their T cell allostimulatory activity via B7-H1 up-regulation

The nucleotide-binding oligomerization domain (NOD)2/CARD15 protein, which senses muramyl dipeptide (MDP), a product of bacterial peptidoglycan, appears to play an important role in regulating intestinal immunity. Although the liver is exposed to gut-derived MDP, the influence of NOD2 ligation on hepatic APC, in particular dendritic cells (DC), is unknown. Freshly isolated mouse liver and spleen plasmacytoid (p)DC expressed higher levels of NOD2 message than conventional myeloid (m)DC. Following MDP stimulation in vivo, liver pDC, but not mDC, up-regulated expression of IFN regulatory factor 4 (IRF-4), a negative regulator of TLR signaling, and induced less allogeneic T cell proliferation and IFN-gamma production. The adoptive transfer of liver pDC from MDP-treated mice failed to prime allogeneic T cells in vivo. By contrast, splenic DC IRF-4 levels and T cell stimulatory activity remained unchanged. Liver pDC from MDP-stimulated mice also displayed greater IkappaBalpha, cell surface B7-H1, and B7-H1 relative to CD86 than control liver pDC. No similar effects were observed for liver mDC or spleen DC. Absence of B7-H1 on liver pDC reversed the inhibitory effect of MDP. After ex vivo stimulation with LPS or CpG, liver pDC but not mDC from MDP-treated animals secreted less IL-12p70, IL-6, and TNF-alpha and induced weaker allogeneic T cell proliferation than those from controls. Moreover, CpG-stimulated liver pDC from MDP-treated mice secreted less IFN-alpha than their splenic counterparts, and systemic levels of IFN-alpha were reduced in MDP-treated animals after CpG administration. These findings suggest that differential effects of NOD2 ligation on liver pDC may play a role in regulating hepatic innate and adaptive immunity.

Role of chemokines and their receptors in viral persistence and liver damage during chronic hepatitis C virus infection

Chemokines produced in the liver during hepatitis C virus (HCV) infection induce migration of activated T cells from the periphery to infected parenchyma. The milieu of chemokines secreted by infected hepatocytes is predominantly associated with the T-helper cell/Tc1 T cell (Th1/Tc1) response. These chemokines consist of CCL3 (macrophage inflammatory protein-1 alpha; MIP-1 alpha), CCL4 (MIP-1 beta), CCL5 (regulated on activation normal T cell expressed and secreted; RANTES), CXCL10 (interferon-gamma-inducible protein-10; IP-10), CXCL11 (interferon-inducible T-cell alpha chemoattractant; I-TAC), and CXCL9 (monokine induced by interferon gamma; Mig) and they recruit T cells expressing either CCR5 or CXCR3 chemokine receptors. Intrahepatic and peripheral blood levels of these chemokines are increased during chronic hepatitis C. The interaction between chemokines and their receptors is essential in recruiting HCV-specific T cells to control the infection. When the adaptive immune response fails in this task, non-specific T cells without the capacity to control the infection are also recruited to the liver, and these are ultimately responsible for the persistent hepatic damage. The modulation of chemokine receptor expression and chemokine secretion could be a viral escape mechanism to avoid specific T cell migration to the liver during the early phase of infection, and to maintain liver viability during the chronic phase, by impairing non-specific T cell migration. Some chemokines and their receptors correlate with liver damage, and CXCL10 (IP-10) and CXCR3 levels have shown a clinical utility as predictors of treatment response outcome. The regulation of chemokines and their receptors could be a future potential therapeutic target to decrease liver inflammation and to increase specific T cell migration to the infected liver.

Role of chemokines and their receptors in viral persistence and liver damage during chronic hepatitis C virus infection

Chemokines produced in the liver during hepatitis C virus (HCV) infection induce migration of activated T cells from the periphery to infected parenchyma. The milieu of chemokines secreted by infected hepatocytes is predominantly associated with the T-helper/T-cytotoxic type-1 cell (Th1/Tc1) response. These chemokines consist of CCL3 (macrophage inflammatory protein-1α; MIP-1α), CCL4 (MIP-1β), CCL5 (regulated on activation normal T cell expressed and secreted; RANTES), CXCL10 (interferon-γ−inducible protein-10; IP-10), CXCL11 (interferon-inducible T-cell α chemoattractant; I-TAC), and CXCL9 (monokine induced by interferon γ; Mig) and they recruit T cells expressing either CCR5 or CXCR3 chemokine receptors. Intrahepatic and peripheral blood levels of these chemokines are increased during chronic hepatitis C. The interaction between chemokines and their receptors is essential in recruiting HCV-specific T cells to control the infection. When the adaptive immune response fails in this task, non-specific T cells without the capacity to control the infection are also recruited to the liver, and these are ultimately responsible for the persistent hepatic damage. The modulation of chemokine receptor expression and chemokine secretion could be a viral escape mechanism to avoid specific T cell migration to the liver during the early phase of infection, and to maintain liver viability during the chronic phase, by impairing non-specific T cell migration. Some chemokines and their receptors correlate with liver damage, and CXCL10 (IP-10) and CXCR3 levels have shown a clinical utility as predictors of treatment response outcome. The regulation of chemokines and their receptors could be a future potential therapeutic target to decrease liver inflammation and to increase specific T cell migration to the infected liver.

Liver enzyme alterations in HCV-monoinfected and HCV/HIV-coinfected patients

Hepatitis C virus (HCV) is the most common blood-borne infection in developed countries and co-infection with the Human Immunodeficiency Virus (HIV) is frequent in individuals with history of injecting drug use (IDU).We aimed to analyze liver transaminases in HCV monoinfected and HCV/HIV co-infected patients to assess the effect of HIV infection on liver enzyme elevations.We studied 429 current IDUs admitted to substance abuse treatment (82.5% males). Serum samples for liver tests, HIV infection and viral hepatitis serologies were obtained at admission.

RESULTS

Median age was 30 years (IQR:27-34), median duration of IDU was 10 years (IQR:5-14), 52% of patients were HCV/HIV co-infected, 40.8% were HCV monoinfected, and 7.2% were HCV and HIV- seronegatives. Elevated AST was associated with male gender and lower CD8(+) cell count in the HCV monoinfected patients, and with age and lower cholesterol in the HCV/HIV coinfected subjects. ALT elevation was associated with younger age, higher body mass index and male gender in the monoinfected patients, and with higher CD4(+) cell counts and lower cholesterol in the co-infected group. Male sex was strongly associated with elevated ALT and AST transaminase in the monoinfected but not in dual-infected subjects.These data suggest that the effect of gender on liver enzymes may be lost in patients with HIV infection. The overall differences observed between groups regarding liver enzyme elevations are of clinical relevance in the management of IDUs with chronic hepatitis C.

Differential expression of the CXCR3 ligands in chronic hepatitis C virus (HCV) infection and their modulation by HCV in vitro

To investigate chemokine expression networks in chronic hepatitis C virus (HCV) infection, we used microarray analysis to determine chemokine expression in human infection and in chimpanzees experimentally infected with HCV. The CXCR3 chemokine family was highly expressed in both human and chimpanzee infection. CXCL10 was the only CXCR3 chemokine elevated in the serum, suggesting that it may neutralize any CXCR3 chemokine gradient established between the periphery and liver by CXCL11 and CXCL9. Thus, CXCR3 chemokines may not be responsible for recruitment of T lymphocytes but may play a role in positioning these cells within the liver. The importance of the CXCR3 chemokines, in particular CXCL11, was highlighted by replicating HCV (JFH-1) to selectively upregulate its expression in response to gamma interferon (IFN-gamma) and tumor necrosis factor alpha (TNF-alpha). This selective upregulation was confirmed at the transcriptional level by using the CXCL11 promoter driving the luciferase reporter gene. This synergistic increase in expression was not a result of HCV protein expression but the nonspecific innate response to double-stranded RNA (dsRNA), as both in vitro-transcribed HCV RNA and the dsRNA analogue poly(I:C) increased CXCL11 expression and promoter activity. Furthermore, we show that CXCL11 is an IRF3 (interferon regulatory factor 3) response gene whose expression is selectively enhanced by IFN-gamma and TNF-alpha. In conclusion, the CXCR3 chemokines are the most significantly expressed chemokines in chronic hepatitis C and most likely play a role in positioning T cells in the liver. Furthermore, HCV can selectively increase CXCL11 expression in response to IFN-gamma and TNF-alpha stimulation that may play a role in the pathogenesis of HCV-related liver disease.

Hepatic microenvironment programs hematopoietic progenitor differentiation into regulatory dendritic cells, maintaining liver tolerance

The liver has been generally considered an organ prone to tolerance induction and maintenance. However, whether and how the unique liver microenvironment contributes to tolerance maintenance is largely unknown. Here, we used liver fibroblastic stromal cells to mimic the liver microenvironment and found that liver stroma could induce Lin(-)CD117(+) progenitors to differentiate into dendritic cells (DCs) with low CD11c, MHC II but high CD11b expression, high IL-10, but low IL-12 secretion. Such regulatory DCs could inhibit T-cell proliferation in vitro and in vivo, induce apoptosis of the activated T cells, and alleviate the damage of autoimmune hepatitis. Furthermore, liver stroma-derived macrophage colony-stimulating factor (M-CSF) was found to contribute to the generation of such regulatory DCs. Regulatory DC-derived PGE2 and T cell-derived IFN-gamma were responsible for the regulatory function. The natural counterpart of regulatory DCs was phenotypically and functionally identified in the liver. Importantly, Lin(-)CD117(+) progenitors could be differentiated into regulatory DCs in the liver once transferred into the liver. Infusion with liver regulatory DCs alleviated experimental autoimmune hepatitis. Therefore, we demonstrate that the liver microenvironment is highly important to program progenitors to differentiate into regulatory DCs in situ, which contributes to the maintenance of liver tolerance.

Immune responses during acute and chronic infection with hepatitis C virus

Hepatitis C virus (HCV) induces persistent infection and causes chronic liver disease in most infected patients. Vigorous HCV-specific CD4+ and CD8+ T cell responses against HCV multiple epitopes are necessary for spontaneous viral clearance during the acute phase, but the virus appears to have multiple strategies to evade these defenses. There are relatively few studies on the role of immune responses during the chronic phase of infection. CD4+ T cell responses appear to protect against liver injury and may be important to clearance during interferon and ribavirin based therapy. Classic cytotoxic T cells (CTL) may primarily damage the liver in chronic HCV, but there may be subpopulations of T cells that protect against liver inflammation. Resolution of these outstanding questions is important to the development of a prophylactic vaccine as well as improving therapeutic options for those with chronic infection.

The role of chemokines as inflammatory mediators in chronic hepatitis C virus infection

Hepatitis C virus (HCV) is a leading cause of chronic liver disease that can progress to cirrhosis and/or hepatocellular carcinoma. Intrahepatic inflammation and liver cell injury are defining features of chronic HCV infection. Chemokines, chemotactic cytokines that attract leucocytes to inflammatory sites, may be important in the development of intrahepatic inflammation. As T-helper (Th)1 inflammatory cells, characterized by interferon (IFN)-gamma and interleukin (IL)-2 secretion, predominate in the liver during chronic HCV infection, chemokines that attract these cells might be particularly important in disease progression. In this review, we focus on the role of Th1 chemokines, which are all members of the CXC or CC subfamilies. Among the CXC chemokines, the non-ELR group comprised of IFN-gamma-inducible protein 10 (IP-10), monokine induced by IFN-gamma (Mig) and IFN-inducible T-cell-alpha chemoattractant (I-TAC), attract Th1 cells through the interaction with their receptor, CXCR3. Among the CC subfamily, Th1-associated chemokines include regulated upon activation, normal T-cell expressed and secreted (RANTES) and macrophage inflammatory proteins (MIP)1alpha and beta. These chemokines attract cells through an interaction with their receptor, CCR5. While peripheral blood and intrahepatic levels of all of these chemokines are elevated in chronic hepatitis C patients, only select chemokines have been found to be correlated with hepatic inflammation. Among the six chemokines, IP-10 has uniquely been shown to have prognostic utility as a marker of treatment outcome. In the future, chemokines might be used to monitor the natural course and progression of HCV-associated liver disease, to identify patients with a high likelihood of achieving a therapeutic response, and they may even have potential as therapeutic targets.

Activation of Wnt/beta-catenin pathway mediates growth and survival in B-cell progenitor acute lymphoblastic leukaemia

This study investigated the response of acute lymphoblastic leukaemia (ALL) cells to Wnt proteins. Accumulation of beta-catenin was measured by Western blotting and immunofluorescence microscopy. Reverse transcription polymerase chain reaction (RT-PCR) analysis of B-cell progenitor acute lymphoblastic leukaemia (ALL) cells revealed expression of Wnt genes, including WNT2B in 33%, WNT5A in 42%, WNT10B in 58% and WNT16B in 25% of cases. The Wnt receptors, (Frizzled) FZD7 and FZD8 were also expressed in most cases while FZD3, FZD4 and FZD9 were occasionally detected. Stimulation of ALL cells with Wnt-3a activated canonical Wnt signalling with increased expression and nuclear translocation of beta-catenin. This resulted in a 1.7- to 5.3-fold increase in cell proliferation, which was associated with enhanced cell cycle entry. A significant increase in the survival of ALL cells under conditions of serum deprivation was also observed. Microarray analysis and quantitative RT-PCR revealed that activation of the Wnt/beta-catenin pathway led to altered expression of genes involved in cell cycle regulation and apoptosis in normal and leukaemic B-cell progenitors. Our results demonstrate that Wnt-3a provides proliferative and survival cues in ALL cells. This data suggests that targeting the Wnt signalling pathway may be a useful therapeutic strategy in ALL.

Characterization of CD4, CD8, CD56 positive lymphocytes and C4d deposits to distinguish acute cellular rejection from recurrent hepatitis C in post-liver transplant biopsies

INTRODUCTION

Hepatitis C viral (HCV) infection is the most common cause for liver transplantation (LTx) in USA. Hepatitis C viral recurrence in liver allograft is almost universal, which is often difficult to distinguish from acute cellular rejection (ACR).

AIM

Aim of the present study is to examine the differences between distribution of CD4, CD8, CD56 positive lymphocytes, and C4d deposits in patients with ACR and recurrent HCV.

PATIENTS AND METHODS

As a pilot project, a group of five post-LTx HCV RNA negative patients, strongly suspicious for ACR based on clinical findings and history of medication non-compliance and another group of five post-LTx HCV positive, medication compliant patients with abnormal liver function were retrospectively selected. Liver biopsies of these patients were stained with monoclonal CD4, CD8, CD56, and polyclonal C4d antibodies and compared.

RESULTS

Mean CD4, CD8, and CD56 counts in ACR group were 156.7 +/- 17.6, 35.4 +/- 8.8, and 1.0 +/- 1.8/HPF, respectively and were 89.7 +/- 41.3, 20.3 +/- 23.2, and 0.6 +/- 0.9/HPF, respectively in HCV recurrence group. Biopsies of four of five patients with ACR demonstrated moderate to strong C4d staining, whereas all patients with recurrent HCV had none to mild C4d staining.

CONCLUSION

Mean CD4, CD8, and CD56 were similar for acute rejection and recurrent HCV infection. However, 80% of patients with ACR showed moderate to strong staining for C4d and all recurrent HCV patients showed none to mild C4d staining.

Distinct cellular responses differentiating alcohol- and hepatitis C virus-induced liver cirrhosis

BACKGROUND

Little is known at the molecular level concerning the differences and/or similarities between alcohol and hepatitis C virus induced liver disease. Global transcriptional profiling using oligonucleotide microarrays was therefore performed on liver biopsies from patients with cirrhosis caused by either chronic alcohol consumption or chronic hepatitis C virus (HCV).

RESULTS

Global gene expression patterns varied significantly depending upon etiology of liver disease, with a greater number of differentially regulated genes seen in HCV-infected patients. Many of the gene expression changes specifically observed in HCV-infected cirrhotic livers were expectedly associated with activation of the innate antiviral immune response. We also compared severity (CTP class) of cirrhosis for each etiology and identified gene expression patterns that differentiated ethanol-induced cirrhosis by class. CTP class A ethanol-cirrhotic livers showed unique expression patterns for genes implicated in the inflammatory response, including those related to macrophage activation and migration, as well as lipid metabolism and oxidative stress genes.

CONCLUSION

Stages of liver cirrhosis could be differentiated based on gene expression patterns in ethanol-induced, but not HCV-induced, disease. In addition to genes specifically regulating the innate antiviral immune response, mechanisms responsible for differentiating chronic liver damage due to HCV or ethanol may be closely related to regulation of lipid metabolism and to effects of macrophage activation on deposition of extracellular matrix components.

CXCR 3 activation promotes lymphocyte transendothelial migration across human hepatic endothelium under fluid flow

T cells infiltrating the inflamed liver express high levels of CXCR 3 and show enhanced migration to CXCR 3 ligands in chemotactic assays. Moreover, CXCR 3 ligands are up-regulated on hepatic endothelium at sites of T-cell infiltration in chronic hepatitis, and their presence correlates with outcome of inflammatory liver disease. We used a flow-based adhesion assay with human hepatic endothelium to investigate the function of CXCR 3 on lymphocyte adhesion to and transmigration through hepatic endothelium under physiological conditions of blood flow. To more accurately model the function of in vivo activated CXCR 3(high) lymphocytes, we isolated T cells from human liver tissue and studied their behavior in flow-based adhesion assays. We demonstrate that CXCR 3 not only promoted the adhesion of effector T cells to endothelium from flow but also drove transendothelial migration. Moreover, these responses could be stimulated either by endogenous CXCR 3 ligands secreted by the endothelium or by exogenous CXCR 3 ligands derived from other cell types and presented by the endothelium. This study thus demonstrates that activation of CXCR 3 promotes lymphocyte adhesion and transendothelial migration under flow and that human hepatic endothelium can present functionally active chemokines secreted by other cell types within the liver.

Semiquantitative analysis of intrahepatic CC-chemokine mRNas in chronic hepatitis C

BACKGROUND: The mechanisms leading to hepatic injury in chronic hepatitis C virus (HCV) infection are only incompletely understood. Recent data propose a correlation of the intrahepatic expression of the CC chemokine RANTES and the degree of periportal and portal inflammatory liver damage. AIM: Here, we have studied the intrahepatic mRNA levels of CC chemokines RANTES together with that of other members of this chemokine family (MIP-1beta, MCP-1, and MCP-2) in chronic hepatitis C as compared with healthy controls. METHODS: Liver samples from 22 HCV-infected patients, nine individuals with primary biliary cirrhosis and from 12 normal controls were included into this study. Intrahepatic mRNA levels of CC chemokines RANTES, MIP-1beta, MCP-1, and MCP-2 were analyzed by a semi-quantitative reverse transcription/real-time polymerase chain reaction assay. RESULTS: In chronic HCV infection, intrahepatic RANTES mRNA levels were significantly higher than in non-infected controls (7.2-fold, p < 0.001) or in the disease control group (2.8-fold, p < 0.001) and higher levels of RANTES mRNA levels were observed in livers with an advanced stage of liver cell injury (histologic activity index > or = 6), although this difference was not statistically significant (p = 0.08). In contrast, mRNA levels of MIP-1beta (p = 0.021) and MCP-1 (p = 0.021) were significantly lower in HCV liver samples while MCP-2 expression was similar in all groups analyzed. CONCLUSION: The data support the concept of chemokines as mediators of liver cell injury in chronic hepatitis C.

Semiquantitative analysis of intrahepatic CC-chemokine mRNas in chronic hepatitis C

BACKGROUND

The mechanisms leading to hepatic injury in chronic hepatitis C virus (HCV) infection are only incompletely understood. Recent data propose a correlation of the intrahepatic expression of the CC chemokine RANTES and the degree of periportal and portal inflammatory liver damage.

AIM

Here, we have studied the intrahepatic mRNA levels of CC chemokines RANTES together with that of other members of this chemokine family (MIP-1beta, MCP-1, and MCP-2) in chronic hepatitis C as compared with healthy controls.

METHODS

Liver samples from 22 HCV-infected patients, nine individuals with primary biliary cirrhosis and from 12 normal controls were included into this study. Intrahepatic mRNA levels of CC chemokines RANTES, MIP-1beta, MCP-1, and MCP-2 were analyzed by a semi-quantitative reverse transcription/real-time polymerase chain reaction assay.

RESULTS

In chronic HCV infection, intrahepatic RANTES mRNA levels were significantly higher than in non-infected controls (7.2-fold, p < 0.001) or in the disease control group (2.8-fold, p < 0.001) and higher levels of RANTES mRNA levels were observed in livers with an advanced stage of liver cell injury (histologic activity index > or = 6), although this difference was not statistically significant (p = 0.08). In contrast, mRNA levels of MIP-1beta (p = 0.021) and MCP-1 (p = 0.021) were significantly lower in HCV liver samples while MCP-2 expression was similar in all groups analyzed.

CONCLUSION

The data support the concept of chemokines as mediators of liver cell injury in chronic hepatitis C.

Hepatitis C: What is the nature of the problem?

This review concentrates on the natural history of the infection. The virology and epidemiology of the disease are covered elsewhere. There are a number of inherent difficulties in studying the outcome of HCV infection: the onset is often not recognized, it can be asymptomatic, the progression is slow and patients may have had treatment. However some insights in recent years have been made.