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Biomedical subjects

T Jake Liang

Publications and source records attributed to T Jake Liang.

At least 19 recordsLinked to original sources
PubMed2007

A functional SNP of interferon-gamma gene is important for interferon-alpha-induced and spontaneous recovery from hepatitis C virus infection.

Cytokine polymorphisms are associated with disease outcome and interferon (IFN) treatment response in hepatitis C virus (HCV) infection. We genotyped eight SNPs spanning the entire IFN-gamma gene in two cohorts and assessed the association between those polymorphisms and treatment response or spontaneous viral clearance. The first cohort was composed of 284 chronically HCV-infected patients who had received IFN-alpha-based therapy and the second was 251 i.v. drug users who had either spontaneously cleared HCV or become chronically infected. A SNP variant located in the proximal IFN-gamma promoter region next to the binding motif of heat shock transcription factor (HSF), -764G, was significantly associated with sustained virological response [P = 0.01, odds ratio (OR) = 2.66 [corrected] (confidence interval 1.3-5.6)[corrected]]. The association was independently significant in multiple logistic regression (P = 0.04) along with race, viral titer, and genotype. This variant was also significantly associated with spontaneous recovery [P = 0.04, OR = 3.51 (1.0-12.5)] in the second cohort. Functional analyses show that the G allele confers a two- to three-fold higher promoter activity and stronger binding affinity to HSF1 than the C allele. Our study suggests that the IFN-gamma promoter SNP -764G/C is functionally important in determining viral clearance and treatment response in HCV-infected patients and may be used as a genetic marker to predict sustained virological response in HCV-infected patients.

Alleles↗
PubMed2006

Changes in serum adipokine levels during pioglitazone treatment for nonalcoholic steatohepatitis: relationship to histological improvement.

BACKGROUND & AIMS: Thiazolidinedione (TZD) therapy improves liver histology in nonalcoholic steatohepatitis (NASH) through a mechanism possibly related to its insulin-sensitizing or anti-inflammatory activity. This study was conducted to assess changes in serum levels of selected adipokines and proinflammatory cytokines and to relate these changes to the improved liver histology resulting from pioglitazone therapy for NASH. METHODS: Serum samples from 18 patients with NASH obtained at day 0 and week 48 of therapy during an open-label study of pioglitazone were tested for adiponectin, leptin, interleukin (IL)-1a, IL-6, and tumor necrosis factor (TNF)-alpha levels. Paired liver biopsy specimens were scored (0-4) for steatosis, parenchymal inflammation, cell injury, and fibrosis. RESULTS: Adiponectin levels increased from 3.7 to 10.3 mug/mL at week 48 (P < .01); the levels of the other cytokines were unchanged: TNF-alpha, 9.1 vs 8.8 pg/mL; IL-1a, 3.9 vs 3.4 pg/mL; IL-6, 19.4 vs 13.4 pg/mL; and leptin, 24.8 vs 29.6 ng/mL (P > .05 for all). Pioglitazone therapy was associated with improvements in steatosis (2.5 vs 1.0), parenchymal inflammation (3.3 vs 2.1), cell injury (2.2 vs 0.9), and fibrosis (2.0 vs 1.4). The change in adiponectin level was associated with the improvement in steatosis (P = .03) as well as in a summary NASH activity index score (P = .01). Changes in IL-1, IL-6, TNF-alpha, and leptin levels did not correlate with improvements in the histological features. CONCLUSIONS: Improvements in liver histology during TZD therapy may be modulated by an adiponectin-mediated effect on insulin sensitivity and hepatic fatty acid metabolism rather than by changes in proinflammatory cytokines.

Adiponectin↗
PubMed2006

Hepatitis C -- identifying patients with progressive liver injury.

Hepatitis C follows a variable course with some patients developing progressive liver fibrosis, cirrhosis and hepatocellular carcinoma, while others have minimal or no significant liver disease after decades of infection. Studies have identified both host and viral factors associated with disease progression. The importance of general factors such as age at infection, gender, immune status and alcohol consumption has long been recognized; however recently, polymorphisms in a wide array of genes have also been shown to be associated with progressive fibrosis. How specific viral proteins may contribute to disease progression has also been studied. This review highlights what is currently known about the factors associated with progressive liver injury in patients with hepatitis C. A greater understanding of the determinants of disease progression will hopefully lead to improved utilization of existing treatments and ultimately may aid in identification of new therapeutic targets.

Adult↗
PubMed2006

Steatosis and progression of fibrosis in untreated patients with chronic hepatitis C infection.

Hepatic steatosis is common in patients with chronic hepatitis C (CHC) and is reported to be a risk factor for progression of fibrosis. The aims of this study were to evaluate the interactions between hepatic steatosis and fibrosis in a well-defined cohort of patients with CHC. The computerized pathology database at the National Institutes of Health Clinical Center was searched for patients with CHC who had undergone liver biopsy between 1980 and 2003. Biopsies were scored for necroinflammation using a modified histology activity index, fibrosis using the Ishak system, and steatosis as either none (<5% of cells), mild (5%-25%), or moderate-to-severe (>25%). Four hundred ninety-four patients were identified. The mean age was 44 +/- 9.8 years; 60% were male, 80% Caucasian, and 65% were infected with genotype 1. Steatosis was mild in 31% and moderate to severe in 9% of patients. In univariate analysis, steatosis was associated with increased age, body weight, body mass index (BMI), alanine aminotransferase (ALT) levels, histological necroinflammatory activity, and fibrosis. However, in multivariate analysis, steatosis was associated only with increased age, BMI, and ALT levels and not with fibrosis. One hundred thirty-six patients had 2 liver biopsies separated by 0.5 to 17 years. Worsening of fibrosis occurred in 40% of patients and correlated independently with increasing age, periportal necroinflammation, and ALT elevations but not with steatosis. In conclusion, in this cohort of patients with CHC, steatosis was associated with older age, higher BMI, and higher serum ALT levels but not with the presence of or subsequent progression of fibrosis.

Adolescent↗
PubMed2006

Hepatitis C virus entry: molecular biology and clinical implications.

With an estimated 170 million infected individuals, hepatitis C virus (HCV) has a major impact on public health. A vaccine protecting against HCV infection is not available, and current antiviral therapies are characterized by limited efficacy, high costs, and substantial side effects. Binding of the virus to the cell surface followed by viral entry is the first step in a cascade of interactions between virus and the target cell that is required for the initiation of infection. Because this step represents a critical determinant of tissue tropism and pathogenesis, it is a major target for host cell responses such as antibody-mediated virus-neutralization-and a promising target for new antiviral therapy. The recent development of novel tissue culture model systems for the study of the first steps of HCV infection has allowed rapid progress in the understanding of the molecular mechanisms of HCV binding and entry. This review summarizes the impact of recently identified viral and host cell factors for HCV attachment and entry. Clinical implications of this important process for the pathogenesis of HCV infection and novel therapeutic interventions are discussed.

Animals↗
PubMed2006

The SH3 binding motif of HCV [corrected] NS5A protein interacts with Bin1 and is important for apoptosis and infectivity.

BACKGROUND & AIMS: HCV nonstructural protein 5A (NS5A) has been implicated in regulating cell growth and interferon response. The NS5A protein contains proline-rich regions that are highly conserved among HCV genotypes and match Src homology 3 (SH3)-binding motifs (PxxP) found in various cellular signaling molecules. METHODS: We screened for HCV NS5A interacting proteins by using the yeast 2-hybrid system and studied the functional consequence of this interaction. RESULTS: Several independent clones containing SH3 domains were isolated along with Bin1, a tumor suppressor with pro-apoptotic properties, being the most frequently identified clone. The protein-protein interaction between NS5A and Bin1 was confirmed by in vitro binding, in vivo co-immunoprecipitation, and confocal microscopy. Deletion and mutation analyses indicated that the SH3 binding motif of HCV NS5A and SH3 domain of Bin1 are essential for interaction. Human hepatoma (HepG2) cells lacking expression of Bin1 undergo apoptosis upon infection with adeno-Bin1. Bin1-induced apoptosis was inhibited in HepG2 cells expressing wild-type NS5A but not NS5A mutant with mutations in the SH3 binding motif. Infectious HCV genome containing mutations in the SH3 binding motif was not infectious in chimpanzees. CONCLUSIONS: Our results indicate that this interaction is implicated in productive HCV infection and may contribute to the pathogenesis of hepatocellular carcinoma. In addition, the NS5A PxxP motif may represent a novel target for antiviral development.

Adaptor Proteins, Signal Transducing↗
PubMed2006

Altered proteolysis and global gene expression in hepatitis B virus X transgenic mouse liver.

Hepatitis B virus X (HBX) is essential for the productive infection of hepatitis B virus (HBV) in vivo and has a pleiotropic effect on host cells. We have previously demonstrated that the proteasome complex is a cellular target of HBX, that HBX alters the proteolytic activity of proteasome in vitro, and that inhibition of proteasome leads to enhanced viral replication, suggesting that HBX and proteasome interaction plays a crucial role in the life cycle and pathogenesis of HBV. In the present study, we tested the effect of HBX on the proteasome activities in vivo in a transgenic mouse model in which HBX expression is developmentally regulated by the mouse major urinary promoter in the liver. In addition, microarray analysis was performed to examine the effect of HBX expression on the global gene expression profile of the liver. The results showed that the peptidase activities of the proteasome were reduced in the HBX transgenic mouse liver, whereas the activity of another cellular protease was elevated, suggesting a compensatory mechanism in protein degradation. In the microarray analysis, diverse genes were altered in the HBX mouse livers and the number of genes with significant changes increased progressively with age. Functional clustering showed that a number of genes involved in transcription and cell growth were significantly affected in the HBX mice, possibly accounting for the observed pleiotropic effect of HBX. In particular, insulin-like growth factor-binding protein 1 was down-regulated in the HBX mouse liver. The down-regulation was similarly observed during acute woodchuck hepatitis virus infection. Other changes including up-regulation of proteolysis-related genes may also contribute to the profound alterations of liver functions in HBV infection.

Animals↗
PubMed2006

Novel approaches to new therapies for hepatitis B virus infection.

Hepatitis B is one of the most prevalent viral diseases in the world. It leads to chronic liver disease in 10% of infected individuals, putting them at an increased risk for liver-related morbidity and mortality from complications of cirrhosis and hepatocellular carcinoma. Despite the success of universal hepatitis B vaccination in many countries, this disease remains a major public health problem, resulting in more than 500,000 deaths per year. Although the current therapy for chronic hepatitis B (CHB) is effective, it is not optimal; novel approaches to the management of CHB are needed. An improved understanding of virus-host interactions, advances in gene therapy, the development of molecular therapies targeted at different stages of the hepatitis B virus life cycle, and new insights into various approaches of immune modulation will lead to the development of better therapeutic agents for the management of CHB. These advances herald a new era of combination therapy. In this review, we will discuss emerging therapies and potential mechanisms, and highlight the promises and pitfalls of these new treatment strategies.

Antiviral Agents↗
PubMed2005

Production of infectious hepatitis C virus in tissue culture from a cloned viral genome.

Hepatitis C virus (HCV) infection causes chronic liver diseases and is a global public health problem. Detailed analyses of HCV have been hampered by the lack of viral culture systems. Subgenomic replicons of the JFH1 genotype 2a strain cloned from an individual with fulminant hepatitis replicate efficiently in cell culture. Here we show that the JFH1 genome replicates efficiently and supports secretion of viral particles after transfection into a human hepatoma cell line (Huh7). Particles have a density of about 1.15-1.17 g/ml and a spherical morphology with an average diameter of about 55 nm. Secreted virus is infectious for Huh7 cells and infectivity can be neutralized by CD81-specific antibodies and by immunoglobulins from chronically infected individuals. The cell culture-generated HCV is infectious for chimpanzee. This system provides a powerful tool for studying the viral life cycle and developing antiviral strategies.

Animals↗
PubMed2005

Pilot study of interferon gamma for chronic hepatitis C.

BACKGROUND/AIMS: Currently, there are no effective therapies available for patients with chronic hepatitis C who have failed to respond to optimal interferon alfa-based regimens. The aims of this pilot study were to assess the antiviral activity and safety of interferon gamma in chronic hepatitis C. METHODS: Patients with chronic hepatitis C, genotype 1, who had not responded to or who had relapsed after therapy with interferon alfa and ribavirin were enrolled in a trial of interferon gamma 1b given in doses of 100, 200 or 400 microg subcutaneously three times weekly for 4 weeks. Frequent blood samples were obtained for HCV RNA levels. RESULTS: Fourteen patients were enrolled. Geometric mean HCV RNA levels remained unchanged. Serum aminotransferase levels also did not change, while there were significant decreases in neutrophil counts (-41% from baseline) and hematocrit (-5%). Low grade fever and malaise were common with the first injection of interferon gamma, but no serious side effects were encountered. CONCLUSIONS: Although relatively well tolerated, interferon gamma in doses of 100-400 microg thrice weekly had no effect on HCV RNA levels in patients with chronic hepatitis C who had failed to achieve a sustained response to interferon alfa-based therapies.

Antiviral Agents↗
PubMed2005

An in vitro model of hepatitis C virion production.

The hepatitis C virus (HCV) is a major cause of liver disease worldwide. The understanding of the viral life cycle has been hampered by the lack of a satisfactory cell culture system. The development of the HCV replicon system has been a major advance, but the system does not produce virions. In this study, we constructed an infectious HCV genotype 1b cDNA between two ribozymes that are designed to generate the exact 5' and 3' ends of HCV. A second construct with a mutation in the active site of the viral RNA-dependent RNA polymerase (RdRp) was generated as a control. The HCV-ribozyme expression construct was transfected into Huh7 cells. Both HCV structural and nonstructural proteins were detected by immunofluorescence and Western blot. RNase protection assays showed positive- and negative-strand HCV RNA. Sequence analysis of the 5' and 3' ends provided further evidence of viral replication. Sucrose density gradient centrifugation of the culture medium revealed colocalization of HCV RNA and structural proteins in a fraction with the density of 1.16 g/ml, the putative density of HCV virions. Electron microscopy showed viral particles of approximately 50 nm in diameter. The level of HCV RNA in the culture medium was as high as 10 million copies per milliliter. The HCV-ribozyme construct with the inactivating mutation in the RdRp did not show evidence of viral replication, assembly, and release. This system supports the production and secretion of high-level HCV virions and extends the repertoire of tools available for the study of HCV biology.

Base Sequence↗
PubMed2005

Uptake and presentation of hepatitis C virus-like particles by human dendritic cells.

Hepatitis C virus (HCV) is a major cause of chronic hepatitis worldwide. Interaction of dendritic cells (DCs) with viral particles may play an important role in the immunopathogenesis of HCV infection. Since the synthesis or purification of infectious virions is limited, we used HCV-like particles (HCV-LPs) to study the interaction of HCV with human DCs. Immature DCs exhibited an envelope-specific and saturable binding of HCV-LPs, indicating receptor-mediated DC-HCV-LP interaction. Confocal microscopy revealed that HCV-LPs were rapidly taken up by DCs in a temperature-dependent manner. Competition experiments demonstrated that C-type lectins such as mannose receptor or DC-SIGN (DC-specific intercellular adhesion molecule 3-grabbing nonintegrin) were not sufficient for mediating HCV-LP binding. HCV-LP uptake was followed by DC activation. DCs pulsed with HCV-LPs stimulated HCV core-specific CD4(+) T cells, indicating that uptake of HCV-LPs by DCs leads to antigen processing and presentation on major histocompatibility complex (MHC) class II molecules. Finally, HCV-LP-derived antigens were efficiently cross-presented to HCV core-specific CD8(+) T cells. These findings demonstrate that HCV-LPs represent a novel model system to study HCV-DC interaction allowing definition of the molecular mechanisms of HCV uptake, DC activation, and antigen presentation to T cells. Furthermore, HCV-LP-mediated DC activation and efficient antigen presentation may explain the marked immunogenicity of HCV-LPs in vivo.

Antigen Presentation↗
PubMed2005

Hepatitis B virus mutations associated with fulminant hepatitis induce apoptosis in primary Tupaia hepatocytes.

Hepatitis B virus (HBV) core promoter mutations have been implicated in the pathogenesis of fulminant hepatitis B. Due to the limited availability of primary human hepatocytes, the functional characterization of HBV mutants has been performed predominantly in transformed cells, which may not represent ideal model systems for studying virus-cell interactions. We and others have shown that primary hepatocytes of the tree shrew Tupaia belangeri support HBV infection and replication. In this study, we used primary Tupaia hepatocytes to analyze the phenotype of two HBV core promoter mutations that have been associated with a clinical outbreak of fatal fulminant hepatitis. Similar to previous findings in human hepatoma cells, the HBV core promoter mutations resulted in enhanced viral replication and core expression. Surprisingly, however, the presence of the mutations had a marked effect on hepatocyte viability not previously observed in hepatoma cells. Reduced cell viability was found to be due to the induction of apoptosis, as evidenced by caspase-3 activation and nuclear fragmentation. In conclusion, HBV mutants exhibit a novel phenotype in primary hepatocytes distinctly different from previous findings in hepatoma cell lines. This phenotype may have important implications for the understanding of the fulminant clinical course associated with HBV mutations.

Animals↗
PubMed2005

Structural proteins of Hepatitis C virus induce interleukin 8 production and apoptosis in human endothelial cells.

Hepatitis C virus (HCV) infection is associated with inflammation of liver endothelium, which contributes to the pathogenesis of chronic hepatitis. The mechanism of this endothelitis is not understood, since the virus does not appear to infect endothelial cells productively. Here, an 'innocent bystander' mechanism related to HCV proteins was hypothesized and it was investigated whether the binding of HCV particles to human endothelium induced functional changes in the cells. Exposure of human umbilical vein endothelial cells (HUVECs) to HCV-like particles (HCV-LPs) resulted in increased interleukin 8 (IL8) production and induction of apoptosis. The IL8 supernatants collected after stimulation of HUVECs with HCV-LPs, BV-GUS (control baculovirus containing beta-glucuronidase) and appropriate controls were used to assay the transendothelial migration of neutrophils. This assay confirmed that HCV-LP-induced IL8 was functionally active. Using specific NF-kappaB inhibitors, it was also shown that HCV-LP-induced NF-kappaB activity mediated IL8 production in HUVECs. Apoptosis appeared to be mediated by the Fas/Fas-L pathway, as neutralizing antibodies for Fas and Fas-L significantly protected HUVECs against HCV-LP-induced apoptosis. Treatment of HUVECs with HCV-LPs also enhanced cellular Fas-L expression and augmented caspase-3 activation. This was confirmed by using a specific caspase-3 inhibitor, Z-Asp-Glu-Val-Asp-fluoromethyl ketone. As shown by blocking of specific chemokine receptors for IL8 on HUVECs, the induction of IL8 did not appear to contribute to HCV-LP-induced apoptosis. These results suggest that HCV proteins can trigger the release of inflammatory chemokines such as IL8 and cause endothelial apoptosis, thereby facilitating endothelitis.

Apoptosis↗
PubMed2005

Robust production of infectious hepatitis C virus (HCV) from stably HCV cDNA-transfected human hepatoma cells.

Hepatitis C virus (HCV) chronically infects approximately 170 million people worldwide, with an increased risk of developing cirrhosis and hepatocellular carcinoma. The study of HCV replication and pathogenesis has been hampered by the lack of an efficient stable cell culture system and small-animal models of HCV infection and propagation. In an effort to develop a robust HCV infection system, we constructed stable human hepatoma cell lines that contain a chromosomally integrated genotype 2a HCV cDNA and constitutively produce infectious virus. Transcriptional expression of the full-length HCV RNA genome is under the control of a cellular Pol II polymerase promoter at the 5' end and a hepatitis delta virus ribozyme at the 3' end. The resulting HCV RNA was expressed and replicated efficiently, as shown by the presence of high levels of HCV proteins as well as both positive- and negative-strand RNAs in the stable Huh7 cell lines. Stable cell lines robustly produce HCV virions with up to 10(8) copies of HCV viral RNA per milliliter (ml) of the culture medium. Subsequent infection of naïve Huh7.5 cells with HCV released from the stable cell lines resulted in high levels of HCV proteins and RNAs. Additionally, HCV infection was inhibited by monoclonal antibodies specific to CD81 and the HCV envelope glycoproteins E1 and E2, and HCV replication was suppressed by alpha interferon. Collectively, these results demonstrate the establishment of a stable HCV culture system that robustly produces infectious virus, which will allow the study of each aspect of the entire HCV life cycle.

Animals↗
PubMed2005

Hepatitis B virus X protein sensitizes primary mouse hepatocytes to ethanol- and TNF-alpha-induced apoptosis by a caspase-3-dependent mechanism.

It is well-documented that alcohol drinking together with hepatitis viral infection accelerates liver injury; however the underlying mechanisms remain unknown. In this paper, we demonstrated that primary hepatocytes from transgenic mice overexpressing hepatitis B virus X protein (HBX) were more susceptible to ethanol- and TNF-alpha-induced apoptotic killing. Compared to normal control mouse hepatocytes, ethanol and/or TNF-alpha treatment led to a significant increase in reactive oxygen species, mitochondrial permeability transition, cytochrome C release, caspase-3 activity, and poly (ADP-ribose) polymerase degradation in hepatocytes from HBX transgenic mice. Blocking caspase-3 activity antagonized ethanol- and TNF-alpha-induced apoptosis in primary hepatocytes from HBX transgenic mice. Taken together, our findings suggest that HBX sensitizes primary mouse hepatocytes to ethanol- and TNF-alpha-induced apoptosis by a caspase-3-dependent mechanism, which may partly explain the synergistic effects of alcohol consumption and hepatitis B virus infection on liver injury.

Animals↗