Subcellular localization, stability, and trans-cleavage competence of the hepatitis C virus NS3-NS4A complex expressed in tetracycline-regulated cell lines

A tetracycline-regulated gene expression system and a panel of novel monoclonal antibodies were used to examine the subcellular localization, stability, and trans-cleavage competence of the hepatitis C virus (HCV) NS3-NS4A complex in inducible cell lines. The NS3 serine protease domain and the full-length NS3 protein expressed in the absence of the NS4A cofactor were diffusely distributed in the cytoplasm and nucleus. Coexpression of NS4A, however, directed NS3 to the endoplasmic reticulum (ER) or an ER-like modified compartment, as demonstrated by colocalization with 3,3'-dihexyloxacarbocyanine iodide, protein disulfide isomerase, and calnexin, as well as subcellular fractionation analyses. In addition, coexpression with NS4A dramatically increased the intracellular stability of NS3 (mean protein half-life of 26 versus 3 h) and allowed for NS4A-dependent trans-cleavage at the NS4B-NS5A junction. Deletion analyses revealed that the hydrophobic amino-terminal domain of NS4A was required for ER targeting of NS3. These results demonstrate the importance of studying HCV proteins in their biological context and define a well-characterized cell culture system for further analyses of the NS3-NS4A complex and the evaluation of novel antiviral strategies against hepatitis C.

Gene therapy of hepatocellular carcinoma in vitro and in vivo in nude mice by adenoviral transfer of the Escherichia coli purine nucleoside phosphorylase gene

Expression of viral or bacterial enzymes in tumor cells to convert nontoxic prodrugs into highly toxic metabolites is an attractive gene-therapeutic approach for the treatment of hepatocellular carcinoma (HCC). The Escherichia coli purine nucleoside phosphorylase (PNP) converts purine analogs into freely diffusible metabolites, which are highly toxic to dividing and nondividing cells. We investigated the antitumor effects of PNP in the human HCC cell lines, HepG2, Hep3B, and HuH-7, and performed a comparison with herpes simplex thymidine kinase (TK). The genes for PNP, TK, and enhanced green fluorescent protein (EGFP) were delivered to HCC cells by identical adenoviral vectors. Fludarabine and ganciclovir (GCV) served as prodrugs for PNP and TK, respectively. Expression of PNP highly sensitized HCC cells to fludarabine treatment. Fludarabine concentrations between 0.5 and 1 microg/mL killed 100% of the cells expressing PNP with no detectable toxicity in control cells expressing EGFP. Expression of PNP in as few as 10% of HCC cells induced efficient killing of most bystander cells. Expression of TK followed by GCV treatment produced a potent growth inhibition but failed to kill all TK-expressing HCC cells. More importantly, the TK system exhibited a lower degree of bystander effect. Adenoviral delivery of PNP followed by fludarabine administration prevented subcutaneous and intrahepatic tumor formation in nude mice and was also effective for the treatment of established tumors. These results demonstrate the potential of the PNP/fludarabine system for the treatment of HCC.

[Screening for prevention and early detection of colorectal carcinoma]

Colorectal Cancer (CRC) fulfills all the criteria for a successful screening: i) it is a frequent tumor associated with serious morbidity and mortality; ii) recognition and treatment of premalignant lesions or early tumor stages improves prognosis and lowers its incidence, respectively. During recent years, our understanding of the biology, diagnosis and therapy of adenomas and CRCs led to the identification of risk factors. Based on these, screening strategies differ for individuals with average risk (age > or = 50 years, no risk factors) and individuals with increased risk for CRC development (positive personal history [CRC, colorectal adenomas, inflammatory bowel disease]; positive family history [CRC, colorectal adenomas, hereditary syndromes]). The currently available strategies aimed at prevention and early detection of CRCs (past history, family history, rectal digital examination, fecal occult blood testing, endoscopy) are discussed and recommendations for their implementation are formulated.

[Gene technology drugs and gene therapy]

The principles of recombinant DNA technology are illustrated based on the biology of somatic cells with transcription of chromosomal DNA into messenger RNA and its translation into protein. Recombinant DNA technology allows the cloning, identification and characterization of genes and their expression with the production of medically relevant proteins. The products of recombinant DNA technology are cloned genes on the one hand. These may be useful for molecular diagnosis and gene therapy. On the other hand they comprise recombinant proteins which may be useful in the diagnosis, therapy and prevention of human diseases.

Current and evolving therapies for hepatitis C

Hepatitis C virus (HCV) infection is a leading cause of chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma worldwide. Therapeutic options for hepatitis C are limited. Standard monotherapy with interferon-alpha leads to a sustained response in only 10-20% of patients. Recent studies have shown improved sustained response rates for the combination of interferon-alpha and ribavirin. Despite these improvements, more effective therapies are needed. A variety of alternative agents are currently being evaluated in clinical trials. Recent advances in the molecular virology of hepatitis C have identified specific antiviral targets such as the viral NS3 serine protease, the RNA helicase, and the RNA-dependent RNA polymerase. In addition, gene therapeutic strategies aimed at inhibiting HCV gene expression and replication as well as immunotherapeutic concepts aimed at enhancing the cellular immune response against HCV are being explored in various experimental systems. These and other novel antiviral strategies may complement the existing therapeutic modalities in the future.

Expression of hepatitis C virus proteins inhibits signal transduction through the Jak-STAT pathway

Hepatitis C virus (HCV) infection is a leading cause of liver disease worldwide. Alpha interferon (IFN-alpha) therapy of chronic hepatitis C leads to a sustained response in 10 to 20% of patients only. The mechanisms of viral persistence and the pathogenesis of hepatitis C are poorly understood. We established continuous human cell lines, allowing the tightly regulated expression of the entire HCV open reading frame under the control of a tetracycline-responsive promoter. Using this in vitro system, we analyzed the effect of HCV proteins on IFN-induced intracellular signaling. Expression of HCV proteins in these cells strongly inhibited IFN-alpha-induced signal transduction through the Jak-STAT pathway. Inhibition occurred downstream of STAT tyrosine phosphorylation. Inhibition of the Jak-STAT pathway was not restricted to IFN-alpha-induced signaling but was observed in leukemia inhibitory factor-induced signaling through Stat3 as well. By contrast, tumor necrosis factor alpha-induced activation of the transcription factor NF-kappaB was not affected. Interference of HCV with IFN-alpha-induced signaling through the Jak-STAT pathway could contribute to the resistance to IFN-alpha therapy observed in the majority of patients and may represent a general escape strategy of HCV contributing to viral persistence and pathogenesis of chronic liver disease.

Ampullary hamartoma: A rare cause of biliary obstruction

Tumors of the papilla of Vater are very rare. Despite advanced imaging techniques the distinction between benign and malignant tumors remains very difficult. Because most ampullary and periampullary tumors are malignant, primary management is surgical. Here we report the case of a 65-year-old man with biliary obstruction caused by an ampullary hamartoma simulating cancer. The correct diagnosis was not established until surgery.

[The evaluation of HepatoConsult, a hepatological expert system--the initial results and trends]

BACKGROUND AND OBJECTIVE

HepatoConsult (HC) is a medical expert system, based on the expert system building block D3, designed to aid in the diagnosis of liver and biliary tract disease. It was the aim of this study to evaluate its diagnostic competence in clinical cases prospectively.

PATIENTS AND METHODS

The diagnostic accuracy of HC was tested prospectively in 106 consecutive patients with the main diagnosis of liver disease. 57 were ambulant, 49 were in-patients. The data were obtained and stored at defined phases of the diagnosis. The diagnoses put forward by HC were compared with the final clinical diagnosis and, on the basis of the data, checked for plausibility by four experienced physicians.

RESULTS

After history taking and physical examination HC put forward the main diagnosis, as established by the doctors in charge, in 60% of patients. After addition of the results of basic laboratory tests and sonography, HC provided the correct diagnosis in 85% and, after inclusion of all the findings, in 93%. In almost all cases HC put forward diagnoses that were, on the basis of the supplied data, considered correct by the four physicians experienced in liver disease. In 56% of cases HC provided more differentiated diagnoses or items in the differential diagnosis than the attending doctors. In the opinion of the four assessors HC had not put forward any seriously wrong diagnoses.

CONCLUSION

HC can be useful in solving diagnostic problems and thus in ensuring the quality of medical diagnoses.

Dominant negative mutants of the duck hepatitis B virus core protein interfere with RNA pregenome packaging and viral DNA synthesis

Dominant negative (DN) mutants of the hepadnaviral core protein are potent inhibitors of viral replication. We have previously shown that fusion of sequences derived from the duck hepatitis B virus (DHBV) polymerase (Pol), DHBV small surface protein (S), bacterial beta-galactosidase (lacZ), or green fluorescent protein (GFP) to the carboxy terminus of the DHBV core protein yields DN mutants that inhibit viral replication at the posttranslational level. To elucidate the mechanism(s) of their antiviral action, we analyzed the effect of the DN mutants on RNA pregenome packaging and nucleocapsid assembly. Core-Pol and core-S, but not core-lacZ or core-GFP, markedly interfered with RNA pregenome packaging. Nucleocapsid formation was not affected by any of the mutants. The DN core-GFP fusion protein formed mixed particles with wild-type core protein in the cytoplasm of cotransfected cells and interfered with reverse transcription of the viral pregenome. A subpopulation of chimeric nucleocapsids, however, was shown to overcome the block in DNA synthesis and produce mature viral DNA. Thus, at least 2 steps within the viral life cycle can be targeted by DN DHBV core proteins: 1) packaging of the viral pregenome; and 2) reverse transcription within mixed particles. The fact that some mixed particles retain replication competence demonstrates a high structural flexibility of nucleocapsids and indicates a possible mechanism of viral escape.

Neurological manifestations of chronic hepatitis C

Hepatitis C virus (HCV) infection is often associated with abnormal immunological responses. We describe four patients with vasculitic neurological signs and symptoms following HCV infection. A 56-year-old woman with HCV infection developed peripheral neuropathy characterized by asymmetric distal painful hypesthesia, dysesthesia and moderate motor weakness of the lower limbs. Serological examinations revealed cryoglobulinemia and low levels of complement C4. A biopsy of the sural nerve revealed vasculitic neuropathy. HCV infection associated immunomediated vasculitis was diagnosed. While steroid therapy was ineffective, treatment with interferon-alpha improved the neuropathy considerably without, however, eliminating HCV infection. A 62-year-old man with HCV infection developed peripheral sensory neuropathy. Complement C3 was slightly diminished. Nerve biopsy revealed vasculitic neuropathy. A 71-year-old woman developed chronic symmetric sensomotor polyneuropathy. HCV hepatitis followed blood transfusions. Cryoglobulins tested positive, consistent with type II cryoglobulinemia. Complements C3 and C4 were diminished. Inflammatory infiltrates in the sural nerve biopsy specimen led to the diagnosis of chronic vasculitic disorder. A 55-year-old woman with HCV infection developed vasculitis of the skin, connective tissue, visceral organs, and kidney, leading to hemodialysis. Neurologically she developed severe apathy and drowsiness, myoclonic jerks, exaggerated deep tendon reflexes, and positive pyramidal signs. Magnetic resonance imaging of the brain showed diffuse increased signal abnormalities involving supra- and infratentorial white matter suggesting cerebral vasculitis. Cryoglobulins were positive, complements C3 and C4 slightly diminished (54 mg/dl, 4.3 mg/dl). Supportive therapy resulted in neurological improvement. Treatment with interferon-alpha was discontinued because of agranulocytosis. In patients with peripheral neuropathy or signs of leucencephalopathy, a hepatitis C associated vasculitis should be considered in the differential diagnosis.

Intracellular retention of hepatitis B virus surface proteins reduces interleukin-2 augmentation after genetic immunizations

We have previously shown that hepatitis B virus (HBV) surface antigens (HBsAgs) are highly immunogenic after genetic immunization. Compared to the secreted middle HBV surface proteins (MHBs) or small HBV surface proteins (SHBs), the nonsecreted large HBV surface protein (LHBs), however, induced significantly weaker humoral and cellular immune responses that could not be augmented by genetic coimmunizations with cytokine expression plasmids. In order to understand the mechanisms underlying this phenomenon, we examined the effect of coimmunizations with an interleukin-2 (IL-2) DNA expression plasmid on the immunogenicity at the B- and T-cell level of nonsecreted wild-type LHBs, a secreted mutant LHBs, wild-type SHBs, and a nonsecreted mutant SHBs. Coimmunizations of mice with plasmids encoding wild-type SHBs or the secreted mutant LHBs and IL-2 increased anti-HBs responses, helper T-cell proliferative activity and cytotoxic T-lymphocyte killing. By contrast, coimmunizations of plasmids encoding wild-type LHBs or nonsecreted mutant SHBs and IL-2 had no significant effects on immune responses. Interestingly, mice immunized with cytokine expression plasmids 14 days after the injection of the wild-type LHBs plasmid showed augmented immune responses compared to animals simultaneously injected with both expression constructs. Anti-HBs responses in mice injected with plasmids encoding secreted forms of HBsAgs were detectable about 10 days earlier than those in mice immunized with plasmids encoding nonsecreted forms of HBsAgs. Based on these observations, we conclude that cytokines produced by DNA plasmids at the initial site of antigen presentation cannot augment LHBs specific immune responses because LHBs is not produced at high enough levels or is not accessible for uptake by antigen-presenting cells.

Correlation of duplex sonography findings and portal pressure in 375 patients with portal hypertension

OBJECTIVE

The purpose of this study was to determine the potential usefulness of duplex sonography in the grading of portal hypertension.

SUBJECTS AND METHODS

Duplex sonography of the portal vein system and measurement of the portal pressure and portosystemic pressure gradient were performed in 375 patients before placement of transjugular intrahepatic portosystemic shunts. Subgroups included patients with recent variceal bleeding (n = 296) and patients with refractory ascites without previous variceal bleeding (n = 79). A matched cohort of 100 patients without portal hypertension was also examined. Differences between the groups in portal and splenic vein diameter, flow velocity, congestion index, and hepatic arterial resistive index were assessed using the Wilcoxon rank sum test.

RESULTS

Compared with healthy individuals, our patients had an increased portal vein diameter (+30%, p < .001), decreased portal vein flow velocity (-44%, p < .001), and increased congestion index (+185%, p < .001). A portal vein diameter greater than 1.25 cm or a portal vein flow velocity less than 21 cm/sec indicated portal hypertension with a sensitivity and specificity of 80%. If the congestion index exceeded 0.1, portal hypertension was diagnosed with a 95% sensitivity and specificity. The portal pressure and gradient correlated only weakly (r < .2, p < .05) with sonographic variables. Using multivariate analysis, subgroups with variceal bleeding or refractory ascites did not show differences in hemodynamics, including pressures.

CONCLUSION

Duplex sonography contributes to the diagnosis of portal hypertension but does not allow its grading. Similarity of portal hemodynamics between patients with variceal bleeding and patients with refractory ascites suggests that additional factors determine the respective clinical presentation.

Platelet aggregation and platelet-derived growth factor inhibition for prevention of insufficiency of the transjugular intrahepatic portosystemic shunt: a randomized study comparing trapidil plus ticlopidine with heparin treatment

Intimal proliferation at the interface between prosthetic material and tissue is an intrinsic phenomenon of stenting and the major cause of insufficiency of the transjugular intrahepatic portosystemic shunt (TIPS). For its prevention, a randomized study was performed comparing standard heparin treatment with a combination of trapidil, a drug with anti-platelet-derived growth factor (PDGF) activity, and ticlopidine, a platelet aggregation inhibitor. Ninety patients with cirrhosis who received a transjugular shunt were randomized, and 84 patients completed the trial. Group 1 (n = 42) received a bolus of heparin (12 to 24 U/kg) at shunt placement, followed by 1 week of intravenous and 4 weeks of subcutaneous heparin treatment. Group 2 (n = 42) received the same heparin bolus, followed by a 1-day intravenous heparin treatment and a 6-month treatment with trapidil (400 mg/d) and ticlopidine (250 mg/d). Shunt function was assessed by duplex-sonography and angiography. Stenoses were classified according to their location as type 1 (within the stent) and type 2 (in the draining hepatic vein). The estimated rate of overall stenoses (intention-to-treat analysis) at 1 year showed a significant reduction in patients receiving trapidil and ticlopidine (group 2) as compared with heparin (33 vs. 57%; P =.047). There was no difference in the estimated 1-year rate of type 1 stenoses between the two groups, but there was a significant reduction in type 2 stenoses (group 1: 58%, group 2: 19%; P =.016). The treatment effect continued after withdrawal of the drugs and was accompanied by a decreased incidence of rebleeding. The study demonstrates that the incidence of type 2 stenosis of the transjugular shunt can be reduced by combined inhibition of platelet aggregation and PDGF activity. The findings may be of relevance not only for the transjugular shunt, but also for other stent applications, e.g., vascular and biliary, as well as for bypass and shunt surgery.

Molecular biology and gene therapy in gastroenterology and hepatology

Molecular analyses have become an integral part of biomedical research as well as clinical medicine. The definition of the molecular and genetic basis of many human diseases has led to a better understanding of their pathogenesis and has in addition offered new perspectives for their diagnosis, therapy and prevention. Genetically, human diseases can be classified as monogenetic, complex genetic and acquired genetic diseases. Based on this classification, gene therapy is based on four concepts: gene substitution, gene augmentation, block of gene expression or function as well as DNA vaccination. While recent developments are promising, various delivery, targeting and safety issues need to be addressed before gene therapy will enter clinical practice. In the future, molecular diagnosis and gene therapy of gastrointestinal and liver diseases will be part of our patient management and complement existing diagnostic, therapeutic and preventive strategies.

Survival benefit of patients with inoperable hepatocellular carcinoma treated by a combination of transarterial chemoembolization and percutaneous ethanol injection--a single-center analysis including 132 patients

Hepatocellular carcinoma (HCC) is one of the most severe sequelae of chronic liver disease. The only potentially curative therapeutic options are surgical resection and orthotopic liver transplantation. In most HCC patients, however, at clinical presentation the tumors are unresectable because of multicentricity or poor hepatic functional reserve due to pre-existing cirrhosis or not transplantable because of too advanced tumor stage or severe co-morbidity. In clinical practice, therefore, percutaneous ethanol injection (PEI) and transarterial chemoembolization (TACE) are widely used non-surgical therapeutic strategies. We prospectively analyzed the clinical factors determining the prognosis of 132 inoperable HCC patients and assessed the feasibility, therapeutic efficacy and safety of PEI, TACE and a combination thereof. Mean age of patients was 64 years; 95% of patients had liver cirrhosis and 39% were Okuda stage I, 48% stage II and 13% stage III. Fifteen patients were treated by PEI (group 1), 33 by TACE (group 2), 39 by TACE and PEI (group 3) and 45 received best supportive care (group 4). Survival correlated with the Child-Pugh class of liver cirrhosis and the Okuda stage of HCC. Favorable prognostic parameters were alpha-fetoprotein (AFP) levels <100 ng/ml and absence of portal vein thrombosis. Median survival time was 18 months in group 1 [interquartile range (IQR) 10-19], 8 months in group 2 (IQR 5-15), 25 months in group 3 (IQR 13-36) and 2 months in group 4 (IQR 1-9). Multivariate analysis revealed that patients treated with a combination of TACE and PEI have a significantly better survival than patients receiving either PEI or TACE only (p = 0.001). Patients with inoperable HCCs treated by the combination of TACE and PEI have a clear survival benefit. A favorable outcome can be expected in patients with compensated cirrhosis, a low Okuda stage, a baseline AFP level <100 ng/ml and absence of portal vein thrombosis.