Pathogenesis of hepatocellular damage in chronic hepatitis C virus infection

IFNL3/4 genotype is associated with altered immune cell populations in peripheral blood in chronic hepatitis C infection

Single-nucleotide polymorphisms near the interferon lambda 3 (IFNL3) gene predict outcomes to infection and anti-viral treatment in hepatitis C virus (HCV) infection. To identify IFNL3 genotype effects on peripheral blood, we collected phenotype data on 400 patients with genotype 1 chronic hepatitis C (CHC). The IFNL3 responder genotype predicted significantly lower white blood cells (WBCs), as well as lower absolute numbers of monocytes, neutrophils and lymphocytes for both rs8099917 and rs12979860. We sought to define the WBC subsets driving this association using flow cytometry of 67 untreated CHC individuals. Genotype-associated differences were seen in the ratio of CD4CD45RO+ to CD4CD45RO-; CD8CD45RO+ to CD8CD45RO-, NK CD56 dim to bright and monocyte numbers and percentages. Whole blood expression levels of IFNL3, IFNLR1 (interferon lambda receptor 1), IFNLR1-mem (a membrane-associated receptor), IFNLR1-sol (a truncated soluble receptor), MxA and T- and NK (natural killer) cell transcription factors TBX21, GATA3, RORC, FOXP3 and EOMES in two subjects were also determined. CHC patients demonstrated endogenous IFN activation with higher levels of MxA, IFNLR1, IFNLR1-mem and IFNLR1-sol, and IFNL3 genotype-associated differences in transcription factors. Taken together, these data provide evidence of an IFNL3 genotype association with differences in monocyte, T- and NK cell levels in the peripheral blood of patients with CHC. This could underpin genotype associations with spontaneous and treatment-induced HCV clearance and hepatic necroinflammation.

HCV genome-wide genetic analyses in context of disease progression and hepatocellular carcinoma

Hepatitis C virus (HCV) is a major cause of hepatitis and hepatocellular carcinoma (HCC) world-wide. Most HCV patients have relatively stable disease, but approximately 25% have progressive disease that often terminates in liver failure or HCC. HCV is highly variable genetically, with seven genotypes and multiple subtypes per genotype. This variation affects HCV's sensitivity to antiviral therapy and has been implicated to contribute to differences in disease. We sequenced the complete viral coding capacity for 107 HCV genotype 1 isolates to determine whether genetic variation between independent HCV isolates is associated with the rate of disease progression or development of HCC. Consensus sequences were determined by sequencing RT-PCR products from serum or plasma. Positions of amino acid conservation, amino acid diversity patterns, selection pressures, and genome-wide patterns of amino acid covariance were assessed in context of the clinical phenotypes. A few positions were found where the amino acid distributions or degree of positive selection differed between in the HCC and cirrhotic sequences. All other assessments of viral genetic variation and HCC failed to yield significant associations. Sequences from patients with slow disease progression were under a greater degree of positive selection than sequences from rapid progressors, but all other analyses comparing HCV from rapid and slow disease progressors were statistically insignificant. The failure to observe distinct sequence differences associated with disease progression or HCC employing methods that previously revealed strong associations with the outcome of interferon α-based therapy implies that variable ability of HCV to modulate interferon responses is not a dominant cause for differential pathology among HCV patients. This lack of significant associations also implies that host and/or environmental factors are the major causes of differential disease presentation in HCV patients.

The anti-idiotypic antibody 1F7 stimulates monocyte interleukin-10 production and induces endotoxin tolerance

BACKGROUND

Pathogens that establish chronic infection elicit immune responses with suppressive cytokines dominating over pro-inflammatory cytokines. Chronic hepatitis C virus (HCV) infection, human immunodeficiency virus (HIV) infection and simian immunodeficiency virus (SIV) infection are associated with high levels of antiviral antibodies expressing a common idiotype specifically recognized by the 1F7 monoclonal antibody (mAb). The 1F7 mAb is a murine IgMκ antibody raised against immunoglobulin pooled from the plasma of multiple HIV-infected individuals. In this study, we investigated direct effects of the 1F7 mAb itself on peripheral blood mononuclear cells (PBMC).

METHODS

Isolated monocytes or PBMC from healthy controls were incubated with the 1F7 mAb or IgMκ mAb control. Cytokine production was measured in cell culture supernatants by ELISA and cells producing interleukin-10 (IL-10) were identified by subset depletion and intracellular flow cytometry. Endotoxin tolerance was assessed by exposing monocytes to lipopolysaccharide (LPS) following 1F7 mAb or IgMκ mAb control pre-treatment and comparing tumor necrosis factor (TNF)-α levels in cell culture supernatants.

RESULTS

The 1F7 mAb stimulated monocytes and CD36+ lymphocytes to produce IL-10 in a time and dose-dependent manner. Treatment of monocytes with 1F7 mAb also reduced their subsequent responsiveness to LPS stimulation.

CONCLUSIONS

Induction of antibodies expressing the 1F7 idiotype by chronic pathogens may facilitate IL-10 production and progression to chronic infection. Direct effects of IL-10 from human monocytes stimulated by 1F7-like antibodies, followed by monocyte transition to an alternatively activated phenotype illustrated by endotoxin tolerance, are two complementary features favouring a tolerogenic or non-responsive immunological environment.

Dynamic analysis of Th1/Th2 cytokine concentration during antiretroviral therapy of HIV-1/HCV co-infected patients

Background

Co-infection with hepatitis C (HCV) is very common in human immunodeficiency virus 1 (HIV-1) infected patients. Although HIV co-infection clearly accelerates progression of HCV-related fibrosis and liver disease, controversy remains as to the impact of HCV on HIV disease progression in co-infected patients. HIV can cause immune dysfunction, in which the regulatory function of T helper (Th) cells is very essential. Moreover, cytokines derived from Th cells play a prominent role in viral infection. Investigating the functional changes of Th1 and Th2 cells in cytokine level can improve the understanding of the effect of co-infected HCV on HIV infection.

Methods

In this study, we measured the baseline Th1/Th2 cytokine concentration in sera by using flow cytometry in HIV/HCV co-infection, HIV mono-infection, HCV mono-infection, and healthy control group, as well as the dynamic changes of these cytokine levels after receiving highly active antiretroviral therapy (HAART).

Results

The ratio of Th1 and Th2 cytokine concentration in HIV/HCV co-infection was higher than HCV mono-infection and healthy control group, while lower than HIV mono-infection group. After HAART was initiated, the Th1/Th2 ratio of HIV/HCV co-infection group decreased to the same level of healthy control, while HIV mono-infection group was still higher than the control group.

Conclusions

There was no significant evidence showing co-infected with HCV had negative effect on HIV related diseases. However, co-infected with HCV can decrease Th1/Th2 ratio by affecting Th1 cytokine level, especially the secretion of IFN-γ. With the initiation of HAART, Th1 and Th2 cytokine levels were progressively reduced. HIV was the main stimulating factor of T cells in HIV/HCV co-infection group.

Characterization of Anti-HCV Antibodies in IL-10-Treated Patients

There is limited information on the direct role of the neutralizing antibody responses against hepatitis C virus (HCV) infection or methodologies to study them. Previously we have demonstrated that interleukin-10 (IL-10) administered to chronic hepatitis patients led to a decrease in disease activity, but an increase in HCV viral burden. The mechanism behind this is unknown. The objective of this study was to examine the antibody response in IL-10-treated patients. To establish a neutralization antibody assay, HCV-positive and HCV-negative sera were collected and incubated with HCV strain JFH-1 particles before culture with Huh 7.5 cells. Viral replication was measured a week later by either indirect immunofluorescence assay (iIFA) or real-time reverse transcriptase polymerase chain reaction (RT-PCR). After validation of the methodology, the sera from 30 previously-described subjects of a group previously treated with IL-10 were tested for the neutralization capacity of their antibodies. The amount of total anti-HCV antibody in the sera was also measured by direct staining of HCV full-length replicon cells. With this validated neutralization assay for anti-HCV antibodies we found that HCV-neutralizing antibodies are universally present, but with significantly different titers. In patients who were treated with IL-10, the total anti-HCV antibody titers appear to be constant, but with significantly decreased antibody neutralization activity. Our study validates an assay to quantitatively determine the presence and strength of HCV-specific neutralizing antibodies. We have found that IL-10-treated patients have significantly lower HCV antibodies, but maintain the total anti-HCV antibody titer, suggesting a novel mechanism by which IL-10 treatment increases viral load in patients.

Cytokine mRNA expression in hepatitis C virus infection: TH1 predominance in patients with chronic hepatitis C and TH1-TH2 cytokine profile in subjects with self-limited disease

Many determinants of the immune response have been implied in the pathogenesis of chronic hepatitis C. TH1 and TH2 cytokines play a prominent role in viral infections and a dysregulation of these cytokines could account for viral persistence and evolution of chronic disease. To explore a possible TH1 and TH2 cytokine dysregulation resulting in the inability to terminate hepatitis C virus (HCV) infection, we studied TH1 [interferon (IFN)-gamma, interleukin (IL)-2] and TH2 (IL-4, IL-10) mRNA expression of peripheral blood mononuclear cells (PBMC) in response to NS3 HCV antigen stimulation, in 31 untreated patients with chronic hepatitis C and 29 subjects with self-limited disease. After a 48 h culture of PBMC, total RNA isolation was performed and complementary DNA was prepared by reverse transcription. mRNA levels were quantified by real-time polymerase chain reaction using a standard curve formed after cloning each cytokine gene and a reference gene using recombinant DNA technology in a specific plasmid vector. In the patients group, mRNA expression of IFN-gamma, IL-2 and IL-4 but not IL-10 was detected, IFN-gamma being the predominant cytokine expressed. All four cytokines were expressed in subjects with self limited disease, however levels of IFN-gamma were lower and a significant higher expression of IL-10 compared to patients was found. There was a significant correlation between IFN-gamma mRNA expression levels and stage of fibrosis. Our findings show that in chronic hepatitis C, TH1 cytokines predominate and correlate to liver immunopathology. Furthermore, subjects with self-limited disease, maintain the ability to respond to HCV antigens for a long time after disease resolution.

HCV immunopathogenesis: virus-induced strategies against host immunity

Worldwide more than 170 million people are chronically infected with the hepatitis C virus (HCV), which is a frequent cause of chronic hepatitis, cirrhosis, and hepatocellular carcinoma. Unlike infection with other hepatotropic viruses, only a small percentage of acute HCV infections are cleared, and most infected individuals develop lifelong HCV infection in the absence of efficient treatment. It is believed that both viral and host factors contribute to the inability of the host immune system to clear the initial infection and lead to the high propensity of chronic HCV infection.

Poly I:C prevents T cell-mediated hepatitis via an NK-dependent mechanism

BACKGROUND/AIMS

T cell immune responses play key roles in the pathogenesis of viral hepatitis, and innate immunity is known to be also activated during this process, however, the effects of innate immunity activation on T cell-mediated hepatitis remain obscure. Here we examined the effect of the activation of NK cells induced by toll-like receptor 3 (TLR3) ligand, polyinosinic-polycytidylic acid (poly I:C), on concanavalin A (Con A)-induced T cell-mediated liver injury.

METHODS

Mice received nontoxic intraperitoneal poly I:C injection before Con A intravenous administration. The liver injury was examined by measuring serum transaminase and pathology, and the function of hepatic lymphocytes was detected by FACS analysis.

RESULTS

Poly I:C pretreatment protected against T cell-mediated hepatitis, as evidenced by decreased mortality, hepatic necrosis, serum transaminase levels and inflammatory cytokines (IL-4, IFN-gamma). The protective effect of poly I:C was diminished in NK-depleted mice, which could be partially restored by adoptive transfer of NK cells. Administration of poly I:C caused NKT and T cell apoptosis via enhancing expression of Fas protein on these cells and expression of Fas ligand on NK cells.

CONCLUSIONS

These findings suggest that activation of NK cells by poly I:C prevents Con A-induced T cell-hepatitis via downregulation of T/NKT cells and subsequent reduction of inflammatory cytokines.

Transforming growth factor-beta1, Th1 responses, and autoimmune liver disease

Transforming growth factor-beta1 (TGF-beta1) is released during the storage of blood components, particularly platelet concentrates, and transfusion recipients are exposed to high levels of TGF-beta1. Because TGF-beta1 is one of the most potent immunosuppressive cytokines known, understanding the immunobiologic functions of TGF-beta1 may be relevant for understanding the immunobiologic effects of transfusion. Our laboratory studies the biologic effects of TGF-beta1 in the immune system. Mice deficient in TGF-beta1 spontaneously develop autoimmunity, confirming the important role of this cytokinean an immune regulator. A few years ago, my laboratory made the observation that genetic background strongly affects the phenotype of TGF-beta1-/- mice. TGF-beta1-/- mice on the BALB/c background rapidly develop an aggressive T-cell-mediated hepatitis, whereas TGF-beta1-/- mice on the 129/CF-1 background do not. In this review, I summarize findings published or in press from our laboratory on disease pathogenesis in TGF-beta1-/- mice and then discuss some of the exciting (as-yet-unpublished) directions our laboratory is currently taking.

Hepatitis C virus infection in renal transplant patients: a comparative study with immunocompetent patients

The behavior of hepatitis C in states of immunodeficiency is poorly understood and it is still unclear whether the characteristics of hepatitis C virus (HCV) infection in renal transplant patients differ from those observed in immunocompetent subjects. The aim of this study was to compare the biochemical and histologic characteristics of chronic HCV infection between renal transplant and immunocompetent patients. Forty-one HCV-RNA-positive renal transplant patients and 41 immunocompetent controls matched for gender, age at infection and time of infection were included in the study. The groups were compared regarding laboratory and histologic variables. Renal transplant patients showed lower alanine aminotransferase (ALT) levels (p = 0.005) and higher levels of gamma-glutamyltransferase (p = 0.003), alkaline phosphatase (p < 0.001), and direct bilirubin (p < 0.001) when compared with controls. Histologic analysis revealed less intense portal (p < 0.001) and periportal (p = 0.046) inflammatory infiltrate in renal transplant patients but a larger proportion of cases with confluent necrosis (p = 0.043). No difference in the presence of septal fibrosis, hepatic steatosis, bile duct injury and siderosis was observed. However, there was a difference in the presence of lymphoid aggregates, which were less frequent in the renal transplant group (p < 0.001). In conclusion, the characteristics of hepatitis C in renal transplant patients differ from that observed in immunocompetent patients. In renal transplant patients, HCV infection is biochemically characterized by lower ALT levels and higher frequency of cholestasis. Regarding histology, despite lower frequency of lymphoid aggregates and less intense portal/periportal inflammatory infiltrate, a greater lobular damage was observed. The impact of these differences on the progression of fibrosis remains to be established.

New onset diabetes mellitus after liver transplantation: the critical role of hepatitis C infection

Epidemiological studies suggest diabetes mellitus (DM) may be an extrahepatic manifestation of chronic hepatitis C virus (HCV) infection. Since diabetes and HCV are common in liver transplant recipients, we sought to examine the unique contribution of HCV infection to risk of de novo diabetes posttransplantation. Using a cohort of 555 liver transplant recipients (median age 49 years, 54% males, 82% Caucasian) without preexisting diabetes from 3 U.S. centers enrolled between 1990 and 1994 and followed for a median duration of 5 years, we determined the incidence of de novo diabetes and the independent predictors of the development of diabetes. De novo diabetes was defined by the use of antidiabetic medications. De novo diabetes developed in 209/555 (37.7%) patients of whom 157 (28.3%) had transient-DM (T-DM) and 52 (9.4%) had persistent-DM (P-DM). Among HCV-infected transplant recipients, de novo T-DM and P-DM developed in 26% and 14%, respectively. HCV was predictive of P-DM (P =.02) but not T-DM. Older age (P =.03) and tacrolimus use (P =.02) were also independent predictors of P-DM. In conclusion, de novo diabetes is common in transplant recipients, but is typically transient in nature. However, among those developing de novo persistent diabetes, HCV is one of the most important risk factors. This adds further support to the epidemiological data linking HCV and diabetes.

Hepatitis C virus and interferon resistance

Interferon plays a critical role in the host's natural defense against viral infections and in their treatment. It is the only therapy for hepatitis C virus (HCV) infection; however, many virus isolates are resistant. Several HCV proteins have been shown to possess properties that enable the virus to evade the interferon-mediated cellular antiviral responses.

Interleukin 10 treatment reduces fibrosis in patients with chronic hepatitis C: a pilot trial of interferon nonresponders

BACKGROUND & AIMS

Interleukin (IL)-10 is a cytokine that down-regulates the proinflammatory response and has a modulatory effect on hepatic fibrogenesis. The aim of this study was to determine the effect of IL-10 on hepatic injury in patients with chronic hepatitis C.

METHODS

Twenty-four patients with chronic hepatitis C who had not previously responded to interferon-based therapy were enrolled in a randomized, double-blinded 2-dose trial in which they received either 4 or 8 microgram/kg IL-10 subcutaneously daily for 90 days. Liver biopsies were performed before and at the end of therapy.

RESULTS

IL-10 was well tolerated with 22 patients completing the study. Serum ALT levels normalized in 19 of 22 patients by the end of therapy and were sustained in 5 of 22. Hepatic inflammation decreased in 19 of 22 patients, with 11 having a decrease by >/=2. Fibrosis decreased in 14 of 22 patients (mean change, 3.6-2.6; P = 0.001). There was no change in serum HCV RNA levels. IL-10 therapy was associated with changes in serological markers, suggesting a reduction of immune response and fibrogenesis.

CONCLUSIONS

IL-10 therapy is safe and well tolerated in patients with chronic hepatitis C. Although it has no apparent antiviral activity, IL-10 normalizes serum ALT levels, improves liver histology, and reduces liver fibrosis in a large proportion of patients receiving treatment. Therefore, IL-10 may have therapeutic potential in patients with chronic hepatitis C patients who do not respond to interferon-based therapy.

Pathologic features of chronic hepatitis. A review and update

The general histopathologic changes of chronic hepatitis and those related to the various causes are reviewed. Consideration also is given to underlying or associated diseases and to mixed infections in chronic viral hepatitis. Changes occurring in exacerbations or relapses are described. Selected histopathologic changes are illustrated. The nomenclature is reviewed briefly, with emphasis on separation of activity from stage of disease.

Hepatitis C: role of the advanced practice nurse

Hepatitis C virus (HCV) is a common but insidious and indolent viral infection that can lead to chronic hepatitis, cirrhosis, and hepatocellular carcinoma. This article provides the advanced practice nurse with current information on prevalence, incidence, spread, and clinical course of hepatitis C. It presents a discussion of the methods of diagnosis, treatment, and management of affected patients. To date, the diagnosis of hepatitis C in the United States has been serendipitous because no surveillance and screening programs have been established. It has been estimated that approximately 4 million persons in the United States are infected with HCV, with only 30% presently diagnosed. Patients with hepatitis C must make informed choices regarding their care and treatment. As more people are diagnosed with hepatitis C, the advanced practice nurse is at the forefront of providing information about spread and diagnosis, treatment options available, and potential side effects of antiviral therapy. The decision to treat chronic HCV must be made in collaboration with other medical experts in hepatology and antiviral therapy, and it must be made with knowledge and understanding of all facets of the disease process and adverse effects of therapy.

Mechanisms of hepatic toxicity. IV. Pathogenetic mechanisms involved in hepatitis C virus-inducedliver diseases

The pathogenetic mechanisms for liver damage in acute hepatitis C are not clear, but a host immune cellular response may be involved. In chronic hepatitis C, there is strong evidence that host cellular immune response is involved in the control of viral replication and contributes to hepatocellular damage. As hepatitis C virus infection persists, continuous liver damage and regeneration, together with enhanced fibrogenesis, may eventually lead to cirrhosis in a proportion of patients. Transplant patients on high-dose immunosuppression may have high-level intrahepatic hepatitis C viral expression, and, in this setting, the virus may induce direct cytopathic liver damage.