Hepatocarcinogenicity of the woodchuck hepatitis virus

Effect of monosodium glutamate on fetal development and progesterone level in pregnant Wistar Albino rats

Monosodium glutamate (MSG) is a widespread flavor enhancer and stabilizer in manufactured or packaged foods that possess myriad adverse effects. This study aimed to evaluate the effect of MSG on placental progesterone receptors and fetal development. Thirty pregnant Wistar Albino rats were divided into three groups (ten/each). The control group (G1) gavaged distilled water only, low-dose treated group (G2) gavaged 3 g/kg MSG, and high-dose treated group (G3) gavaged 6 g/kg MSG from 1st to 18th days of gestation, and all pregnant rats were sacrificed on the 19th day of gestation. The effect of MSG on fetal weights, crown vertebral length (CVL), placental weight, placental ghrelin expression, and fetal skeleton examination were estimated. MSG induced a significant decrease in fetal weights, CVL lengths, placental weight, and ghrelin expression in both treatment groups compared to the control group. Several parts of the fetal skeleton showed incomplete ossification and delayed chondrification in which high-dose maternally treated fetuses were more affected. Many degenerative changes were detected in both maternal and fetal liver and kidney tissues in MSG-treated groups. Moreover, MSG caused a significant increase in serum ALT, ALP, and creatinine levels in pregnant rats' blood. Serum progesterone was only elevated in G3 on the 19th day of gestation. This study showed that the administration of MSG during pregnancy adversely influences fetal growth and skeletal development and caused several biochemical and histological changes in the maternal and fetal liver and kidney tissues which assure the toxic and teratogenic effects of MSG.

Imaging and Pathologic Evaluation of Cryoablation of Woodchuck (Marmota Monax) Hepatocellular Carcinoma

We characterized cryoablation as a mode of clinical intervention in adult woodchucks with hepatocellular carcinoma (HCC). Woodchucks (n = 4) were infected with woodchuck hepatitis virus at birth and developed LI-RADS-5 hypervascular HCC. At 21 mo of age, they underwent ultrasound (US), contrast-enhanced CT (CECT) imaging, and US-guided subtotal cryoablation (IcePearl 2.1 CX, Galil, BTG) of their largest tumor (Mean HCC volume of 49 ± 9 cm³). Cryoablation was performed using two 10-min freeze cycles, each followed by an 8-min thaw cycle. The first woodchuck developed significant hemorrhage after the procedure and was euthanized. In the other 3 woodchucks, the probe track was cauterized and all 3 completed the study. Fourteen days after ablation, CECT was performed, and woodchucks were euthanized. Explanted tumors were sectioned using subject-specific, 3D-printed cutting molds. Initial tumor volume, the size of the cryoablation ice ball, gross pathology and hematoxylin and eosin-stained tissue sections were evaluated. On US, the edges of the solid ice balls were echogenic with dense acoustic shadowing and average dimensions of 3.1 ± 0.5 × 2.1 ± 0.4 cm and cross-sectional area of 4.7 ± 1.0 cm ². On day 14 after cryoablation, CECT of the 3 woodchucks showed devascularized hypo-attenuating cryolesions with dimensions of 2.8 ± 0.3 × 2.6 ± 0.4 × 2.93 ± 0.7 cm and a cross-sectional area of 5.8 ± 1.2 cm². Histopathologic evaluation showed hemorrhagic necrosis with a central amorphous region of coagulative necrosis surrounded by a rim of karyorrhectic debris. A rim of approximately 2.5 mm of coagulative necrosis and fibrous connective tissue clearly demarcated the cryolesion from adjacent HCC. Partial cryoablation of tumors produced coagulative necrosis with well-defined ablation margins at 14 d. Cauterization appeared to prevent hemorrhage after cryoablation of hypervascular tumors. Our findings indicate that woodchucks with HCC may provide a predictive preclinical model for investigating ablative modalities and developing new combination therapies.

Recent Drug Development in the Woodchuck Model of Chronic Hepatitis B

Infection with hepatitis B virus (HBV) is responsible for the increasing global hepatitis burden, with an estimated 296 million people being carriers and living with the risk of developing chronic liver disease and cancer. While the current treatment options for chronic hepatitis B (CHB), including oral nucleos(t)ide analogs and systemic interferon-alpha, are deemed suboptimal, the path to finding an ultimate cure for this viral disease is rather challenging. The lack of suitable laboratory animal models that support HBV infection and associated liver disease progression is one of the major hurdles in antiviral drug development. For more than four decades, experimental infection of the Eastern woodchuck with woodchuck hepatitis virus has been applied for studying the immunopathogenesis of HBV and developing new antiviral therapeutics against CHB. There are several advantages to this animal model that are beneficial for performing both basic and translational HBV research. Previous review articles have focused on the value of this animal model in regard to HBV replication, pathogenesis, and immune response. In this article, we review studies of drug development and preclinical evaluation of direct-acting antivirals, immunomodulators, therapeutic vaccines, and inhibitors of viral entry, gene expression, and antigen release in the woodchuck model of CHB since 2014 until today and discuss their significance for clinical trials in patients.

Application of the woodchuck animal model for the treatment of hepatitis B virus-induced liver cancer

This review describes woodchucks chronically infected with the woodchuck hepatitis virus (WHV) as an animal model for hepatocarcinogenesis and treatment of primary liver cancer or hepatocellular carcinoma (HCC) induced by the hepatitis B virus (HBV). Since laboratory animal models susceptible to HBV infection are limited, woodchucks experimentally infected with WHV, a hepatitis virus closely related to HBV, are increasingly used to enhance our understanding of virus-host interactions, immune response, and liver disease progression. A correlation of severe liver pathogenesis with high-level viral replication and deficient antiviral immunity has been established, which are present during chronic infection after WHV inoculation of neonatal woodchucks for modeling vertical HBV transmission in humans. HCC in chronic carrier woodchucks develops 17 to 36 mo after neonatal WHV infection and involves liver tumors that are comparable in size, morphology, and molecular gene signature to those of HBV-infected patients. Accordingly, woodchucks with WHV-induced liver tumors have been used for the improvement of imaging and ablation techniques of human HCC. In addition, drug efficacy studies in woodchucks with chronic WHV infection have revealed that prolonged treatment with nucleos(t)ide analogs, alone or in combination with other compounds, minimizes the risk of liver disease progression to HCC. More recently, woodchucks have been utilized in the delineation of mechanisms involved in innate and adaptive immune responses against WHV during acute, self-limited and chronic infections. Therapeutic interventions based on modulating the deficient host antiviral immunity have been explored in woodchucks for inducing functional cure in HBV-infected patients and for reducing or even delaying associated liver disease sequelae, including the onset of HCC. Therefore, woodchucks with chronic WHV infection constitute a well-characterized, fully immunocompetent animal model for HBV-induced liver cancer and for preclinical evaluation of the safety and efficacy of new modalities, which are based on chemo, gene, and immune therapy, for the prevention and treatment of HCC in patients for which current treatment options are dismal.

Treatment with the Immunomodulator AIC649 in Combination with Entecavir Produces Antiviral Efficacy in the Woodchuck Model of Chronic Hepatitis B

As current interventions for chronic hepatitis B (CHB) rarely induce cure, more effective drugs are needed. Short-term treatment of woodchucks with the novel immunomodulator AIC649, a parapoxvirus-based stimulator of toll-like receptor 9 dependent and independent pathways, has been shown to reduce viral DNA and surface antigen via a unique, biphasic response pattern. The present study evaluated long-term AIC649 treatment in combination with Entecavir for potency and safety in woodchucks. AIC649 monotreatment induced modest reductions in serum viral DNA and surface and e antigens that were associated with the same biphasic response pattern previously observed. Entecavir monotreatment reduced transiently viremia but not antigenemia, while AIC649/Entecavir combination treatment mediated superior viral control. Undetectability of viral antigens and elicitation of antibodies in AIC649/Entecavir-treated woodchucks correlated with the expression of interferons and suppression of viral replication in liver. Combination treatment was well tolerated, and liver enzyme elevations were minor and transient. It was concluded that the AIC649-mediated effects were most likely based on an improvement and/or reconstitution of antiviral immune responses that are typically deficient in CHB. As a combination partner to Entecavir, the antiviral efficacy of AIC649 was markedly enhanced. This preclinical study supports future evaluation of AIC649 for treatment of human CHB.

Imaging, Pathology, and Immune Correlates in the Woodchuck Hepatic Tumor Model

Background

Woodchucks chronically infected with woodchuck hepatitis virus (WHV), which resembles human hepatitis B virus, develop spontaneous hepatic tumors and may be an important biological and immunological model for human HCC. Nonetheless, this model requires further validation to fully realize its translational potential.

Methods

Woodchucks infected at birth with WHV that had developed HCC (n=12) were studied. Computed tomography, ultrasound, and magnetic resonance imaging were performed under anesthesia. LI-RADS scoring and correlative histologic analysis of sectioned tissues were performed. For immune characterization of tumors, CD3 (T cells), CD4 (T helpers), NCAM (Natural killers), FOXP3 (T-regulatory), PDL-1 (inhibitory checkpoint protein), and the human hepatocellular carcinoma (HCC) biomarker alpha-fetoprotein (AFP) immunohistochemical stains were performed.

Results

Forty tumors were identified on imaging of which 29 were confirmed to be HCC with 26 categorized as LR-4 or 5. The remainder of the tumors had benign histology including basophilic foci, adenoma, and lipidosis as well as pre-malignant dysplastic foci. LR-4 and LR-5 lesions showed high sensitivity (90%) and specificity (100%) for malignant and pre-malignant tumors. Natural killers count was found to be 2–5 times lower in tumors relative to normal parenchyma while other immune cells were located in the periphery of tumors. Tumors expressed AFP and did not express PD-L1.

Conclusion

Woodchucks chronically infected with WHV developed diverse hepatic tumor types with diagnostic imaging, pathology, and immune patterns comparable to that in humans. This unique animal model may provide a valuable tool for translation and validation of novel image-guided and immune-therapeutic investigations.

Ovarian teratoma in a woodchuck (Marmota monax) with hepatocellular carcinoma: radiologic and pathologic features

Background

Teratomas are germ cell neoplasms composed of a wide variety of tissues. In the woodchuck, only one testicular teratoma has been described in the literature. The objective of this report was to describe the radiologic and pathologic findings in a female woodchuck (Marmota monax) with an ovarian teratoma consisting of mature tissues originating from all three germ layers.

Case presentation

A 2-year-old female woodchuck that had been infected at birth with woodchuck hepatitis virus and subsequently developed hepatocellular carcinoma was incidentally discovered to have a mobile 6.6 × 4.8 × 4.7 cm abdominal mass on computed tomography (CT) imaging. The tumor was predominantly solid and heterogenous on CT with soft tissue, fat, and areas of dense calcification. The teratoma did not enhance with intravenous contrast administration. On ultrasound, the tumor was solid with heterogeneous echogenicity, reflecting the fat content and areas of calcification. Sonolucent areas were present that may have represented cysts. There was heterogeneously increased signal on T1-weighted magnetic resonance imaging (MRI) and heterogeneous hyperintensity in T2-weighted imaging. Fat was evident within the tumor. At necropsy, the tumor was attached to the distal end of the right uterine horn. Histopathology showed mature tissue types representing all three germ layers.

Conclusions

Ovarian teratoma should be considered in the differential diagnosis of ovarian or abdominal masses in woodchucks. The tumor displayed mature tissue derived from all three germ layers. CT, ultrasound, and MRI findings were presented in detail and matched the typical imaging appearance of teratomas.

Nanoparticle Uptake in a Spontaneous and Immunocompetent Woodchuck Liver Cancer Model

There is a tremendous focus on the application of nanomaterials for the treatment of cancer. Nonprimate models are conventionally used to assess the biomedical utility of nanomaterials. However, these animals often lack an intact immunological background, and the tumors in these animals do not develop spontaneously. We introduce a preclinical woodchuck hepatitis virus-induced liver cancer model as a platform for nanoparticle (NP)-based in vivo experiments. Liver cancer development in these out-bred animals occurs as a result of persistent viral infection, mimicking human hepatitis B virus-induced HCC development. We highlight how this model addresses key gaps associated with other commonly used tumor models. We employed this model to (1) track organ biodistribution of gold NPs after intravenous administration, (2) examine their subcellular localization in the liver, (3) determine clearance kinetics, and (4) characterize the identity of hepatic macrophages that take up NPs using RNA-sequencing (RNA-seq). We found that the liver and spleen were the primary sites of NP accumulation. Subcellular analyses revealed accumulation of NPs in the lysosomes of CD14⁺ cells. Through RNA-seq, we uncovered that immunosuppressive macrophages within the woodchuck liver are the major cell type that take up injected NPs. The woodchuck-HCC model has the potential to be an invaluable tool to examine NP-based immune modifiers that promote host anti-tumor immunity.

Liver-specific 3D sectioning molds for correlating in vivo CT and MRI with tumor histopathology in woodchucks (Marmota monax)

Purpose

To evaluate the spatial registration and correlation of liver and tumor histopathology sections with corresponding in vivo CT and MRI using 3D, liver-specific cutting molds in a woodchuck (Marmota monax) hepatic tumor model.

Methods

Five woodchucks chronically infected with woodchuck hepatitis virus following inoculation at birth and with confirmed hepatic tumors were imaged by contrast enhanced CT or MRI. Virtual 3D liver or tumor models were generated by segmentation of in vivo CT or MR imaging. A specimen-specific cavity was created inside a block containing cutting slots aligned with an imaging plane using computer-aided design software, and the final cutting molds were fabricated using a 3D printer. Livers were resected two days after initial imaging, fixed with formalin or left unfixed, inserted into the 3D molds, and cut into parallel pieces by passing a sharp blade through the parallel slots in the mold. Histopathology sections were acquired and their spatial overlap with in vivo image slices was quantified using the Dice similarity coefficient (DSC).

Results

Imaging of the woodchucks revealed heterogeneous hepatic tumors of varying size, number, and location. Specimen-specific 3D molds provided accurate co-localization of histopathology of whole livers, liver lobes, and pedunculated tumors with in vivo CT and MR imaging, with or without tissue fixation. Visual inspection of histopathology sections and corresponding in vivo image slices revealed spatial registration of analogous pathologic features. The mean DSC for all specimens was 0.83+/-0.05.

Conclusion

Use of specimen-specific 3D molds for en bloc liver dissection provided strong spatial overlap and feature correspondence between in vivo image slices and histopathology sections.

A Translational Hepatic Artery Infusion (HAI) Model for Hepatocellular Carcinoma in Woodchucks

BACKGROUND

Woodchucks (Marmota monax) are a well-accepted animal model for the investigation of spontaneous hepatocellular carcinoma (HCC). As HCC tumors obtain nutrient blood supply exclusively from the hepatic artery, hepatic artery infusion (HAI) has been applied to HCC. However, there is a scarcity of experimental animal models to standardize drug regimens and examine novel agents. The purpose of this study was to establish an HAI model in woodchucks.

MATERIALS AND METHODS

HAI ports were placed in the gastroduodenal artery (GDA) of 11 woodchucks. The ports were infused with either a vehicle (dextrose 5% in water) or an experimental drug, CBL0137, once a week for 3 wk. Technical success rates, anatomical variation, morbidity and mortality, and tumor responses between groups were analyzed.

RESULTS

The GDA access was feasible and reproducible in all woodchucks (11/11). The average operation time was 95 ± 20 min with no increase in the levels of liver enzymes detected from either infusate. The most common morbidity of CBL0137 therapy was anorexia after surgery. One woodchuck died due to hemorrhage at the gallbladder removal site from hepatic coagulopathy. Significantly higher CBL0137 concentrations were measured in the liver compared with blood after each HAI. Tumor growth was suppressed after multiple CBL0137 HAI treatments which corresponded to greater T cell infiltration and increased tumor cell apoptosis.

CONCLUSIONS

HAI via GDA was a feasible and reproducible approach with low morbidity and mortality in woodchucks. The described techniques serve as a reliable platform for the identification and characterization of therapeutics for HCC.

Transarterial Chemoembolization in a Woodchuck Model of Hepatocellular Carcinoma

PURPOSE

To assess the feasibility of transarterial chemoembolization with drug-eluting embolic (DEE) microspheres in a woodchuck model of hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

Nine woodchucks were studied: 4 normal animals and 5 animals infected with woodchuck hepatitis virus in which HCC had developed. Three animals with HCC underwent multidetector CT. A 3-F sheath was introduced into the femoral artery, and the hepatic arteries were selectively catheterized with 2.0-2.4-F microcatheters. Normal animals underwent diagnostic angiography and bland embolization. Animals with HCC underwent DEE transarterial chemoembolization with 70-150-μm radiopaque microspheres loaded with 37.5 mg doxorubicin per milliliter. Cone-beam CT and multidetector CT were performed. Following euthanasia, explanted livers underwent micro-CT, histopathologic examination, and fluorescence imaging of doxorubicin.

RESULTS

The tumors were hypervascular and supplied by large-caliber tortuous vessels, with arteriovenous shunts present in 2 animals. There was heterogeneous enhancement on multidetector CT with areas of necrosis. Six tumors were identified. The most common location was the right medial lobe (n = 3). Mean tumor volume was 30.7 cm³ ± 12.3. DEE chemoembolization of tumors was achieved. Excluding the 2 animals with arteriovenous shunts, the mean volume of DEE microspheres injected was 0.49 mL ± 0.17. Fluorescence imaging showed diffusion of doxorubicin from the DEE microspheres into the tumor.

CONCLUSIONS

Woodchuck HCC shares imaging appearances and biologic characteristics with human HCC. Selective catheterization and DEE chemoembolization may similarly be performed. Woodchucks may be used to model interventional therapies and possibly characterize radiologic-pathologic correlations.

Evolution of Hepatitis B Virus Receptor NTCP Reveals Differential Pathogenicities and Species Specificities of Hepadnaviruses in Primates, Rodents, and Bats

Human hepatitis B virus (HBV) is a global health problem, affecting more than 250 million people worldwide. HBV-like viruses, named orthohepadnaviruses, also naturally infect nonhuman primates, rodents, and bats, but their pathogenicity and evolutionary history are unclear. Here, we determined the evolutionary history of the HBV receptors NTCP and GPC5 over millions of years of primate, rodent, and bat evolution. We use this as a proxy to understand the pathogenicity of orthohepadnaviruses in mammalian hosts and to determine the implications for species specificity. We found that NTCP, but not GPC5, has evolved under positive selection in primates (27 species), rodents (18 species), and bats (21 species) although at distinct residues. Notably, the positively selected codons map to the HBV-binding sites in primate NTCP, suggesting past genetic "arms races" with pathogenic orthohepadnaviruses. In rodents, the positively selected codons fall outside and within the presumed HBV-binding sites, which may contribute to the restricted circulation of rodent orthohepadnaviruses. In contrast, the presumed HBV-binding motifs in bat NTCP are conserved, and none of the positively selected codons map to this region. This suggests that orthohepadnaviruses may bind to different surfaces in bat NTCP. Alternatively, the patterns may reflect adaptive changes associated with metabolism rather than pathogens. Overall, our findings further point to NTCP as a naturally occurring genetic barrier for cross-species transmissions in primates, which may contribute to the narrow host range of HBV. In contrast, this constraint seems less important in bats, which may correspond to greater orthohepadnavirus circulation and diversity.IMPORTANCE Chronic infection with hepatitis B virus (HBV) is a major cause of liver disease and cancer in humans. Mammalian HBV-like viruses are also found in nonhuman primates, rodents, and bats. As for most viruses, HBV requires a successful interaction with a host receptor for replication. Cellular receptors are thus key determinants of host susceptibility as well as specificity. One hallmark of pathogenic virus-host relationships is the reciprocal evolution of host receptor and viral envelope proteins, as a result of their antagonistic interaction over time. The dynamics of these so-called "evolutionary arms races" can leave signatures of adaptive selection, which in turn reveal the evolutionary history of the virus-host interaction as well as viral pathogenicity and the genetic determinants of species specificity. Here, we show how HBV-like viruses have shaped the evolutionary history of their mammalian host receptor, as a result of their ancient pathogenicity, and decipher the genetic determinants of cross-species transmissions.

Update Treatment for HBV Infection and Persistent Risk for Hepatocellular Carcinoma: Prospect for an HBV Cure

Since the discovery of the hepatitis B virus (HBV) by Blumberg et al. in 1965, its genome, sequence, epidemiology, and hepatocarcinogenesis have been elucidated. Globally, hepatitis B virus (HBV) is still responsible for the majority of hepatocellular carcinoma (HCC). HCC is the sixth-most common cancer in the world and the second-most common cancer death. The ultimate goal of treating HBV infection is the prevention of HCC. Fortunately, anti-HBV treatment with nucleos(t)ide analogues (NAs), which began with lamivudine in 1998, has resulted in remarkable improvements in the survival of patients with chronic hepatitis B and a reduced incidence of HCC. These results were documented with lamivudine, entecavir, and tenofovir. Nonetheless, as the duration of antiviral treatment increases, the risk for HCC still remains despite undetectable HBV DNA in serum, as reported by different investigators with observation up to 4⁻5 years. In our own experience, we are witnessing the development of HCC in patients who have received antiviral treatment. Some have enjoyed negative serum HBV DNA for over 12 years before developing HCC. Current treatment with NAs can effectively suppress the replication of the virus but cannot eradicate the covalently closed circular DNA (cccDNA) that is within the nucleus of hepatocytes. There still remains a great need for a cure for HBV. Fortunately, several compounds have been identified that have the potential to eradicate HBV, and there are ongoing clinical trials in progress in their early stages.

Suspected Hepadnavirus Association with a Hepatocellular Carcinoma in a Black-Tailed Prairie Dog (Cynomys ludovicianus)

Hepatocellular carcinomas are the most commonly reported neoplasm of black-tailed prairie dogs (Cynomys ludovicianus). In several other closely related Sciuridae species, infection with species-specific hepadnaviruses is associated with the development of these tumours, but such a hepadnavirus has not yet been identified in any prairie dog species, although its presence has been hypothesized previously. An adult prairie dog was humanely destroyed due to progressive illness and the identification of a cranial abdominal mass that was determined on histopathology to be a hepatocellular carcinoma. Deep sequencing of the tumour tissue identified the presence of a hepadnavirus, similar in its genetic structure to woodchuck hepatitis virus. Electron microscopy showed the presence of viral particles similar in structure to other hepadnaviral particles. This report suggests that a hepadnavirus may be associated with the development of hepatocellular carcinomas in the prairie dog.

Chronic viral hepatitis and its association with liver cancer

Chronic infection with hepatitis viruses represents the major causative factor for end-stage liver diseases, including liver cirrhosis and primary liver cancer (hepatocellular carcinoma, HCC). In this review, we highlight the current understanding of the molecular mechanisms that drive the hepatocarcinogenesis associated with chronic hepatitis virus infections. While chronic inflammation (associated with a persistent, but impaired anti-viral immune response) plays a major role in HCC initiation and progression, hepatitis viruses can also directly drive liver cancer. The mechanisms by which hepatitis viruses induce HCC include: hepatitis B virus DNA integration into the host cell genome; metabolic reprogramming by virus infection; induction of the cellular stress response pathway by viral gene products; and interference with tumour suppressors. Finally, we summarise the limitations of hepatitis virus-associated HCC model systems and the development of new techniques to circumvent these shortcomings.

cDNA Microarray Analysis in Hepatocyte Differentiation in Huh 7 Cells

The risk of xenozoonosis infections poses the greatest obstacle against the clinical application of a hybrid artificial liver support system (HALSS). Primary human hepatocytes are an ideal source for HALSS, but the shortage of human livers available for hepatocyte isolation limits this modality. To resolve this issue, we previously demonstrated the upregulation of hepatocyte-specific function by spheroid formation in polyurethane foam and by culturing with the histone deacetylase inhibitor, trichostatin A (TSA), in a human hepatoma cell line (Huh 7). In this article we analyze the gene expression profile using cDNA microarray (1281 genes) in spheroid formation or culturing with TSA in Huh 7 to determine the target genes in hepatocyte differentiation. In both the spheroid formation and in the culture with TSA, the Oct-3/4 transcription factor was upregulated more than twofold, while the early growth response-1 (EGR-1) transactivator was downregulated less than 0.5-fold. These results indicate that expressions of Oct-3/4 and EGR-1 may be key factors in the induction of hepatocyte differentiation in Huh 7.

HBV DNA Integration: Molecular Mechanisms and Clinical Implications

Chronic infection with the Hepatitis B Virus (HBV) is a major cause of liver-related morbidity and mortality. One peculiar observation in cells infected with HBV (or with closely‑related animal hepadnaviruses) is the presence of viral DNA integration in the host cell genome, despite this form being a replicative dead-end for the virus. The frequent finding of somatic integration of viral DNA suggests an evolutionary benefit for the virus; however, the mechanism of integration, its functions, and the clinical implications remain unknown. Here we review the current body of knowledge of HBV DNA integration, with particular focus on the molecular mechanisms and its clinical implications (including the possible consequences of replication-independent antigen expression and its possible role in hepatocellular carcinoma). HBV DNA integration is likely to influence HBV replication, persistence, and pathogenesis, and so deserves greater attention in future studies.

Prevention of liver tumor formation in woodchucks with established hepatocellular carcinoma by treatment with cationic liposome-DNA complexes

Background

Approximately 250 million people worldwide are chronically infected with hepatitis B virus (HBV) and more than half of the hepatocellular carcinoma (HCC) cases are attributed to this infection. As HCC has a high mortality rate, and current treatment options are remarkably limited, the development of new therapeutic treatment strategies is warranted.

Methods

In this study, woodchucks infected with woodchuck hepatitis virus (WHV), and with pre-existing liver tumors, were used as a model to investigate if complexes of cationic liposomes and non-coding DNA (JVRS-100) were effective in treatment of HCC.

Results

It was observed that the high serum viral load that is present in a typical chronic WHV infection (i.e., approximately 100-fold higher than human viral loads) results in immune suppression and resistance to treatment with JVRS-100. Treatment of woodchucks with lower serum viral load that more closely matched with the viral load usually seen in human HBV infection appears a better model for immunotherapeutic development based on the responsiveness to JVRS-100 treatment. In the latter case, marked declines in WHV DNA and WHV surface antigen were determined over the 12-week treatment period and WHV markers stayed suppressed during most time points of the 12-week follow-up period. Even more remarkably, the formation of new liver tumors was not observed in woodchucks treated with a well-tolerated dose of JVRS-100, as compared to several new tumors that developed in vehicle-treated control animals.

Conclusions

Although there was little decrease in the volumes of the liver tumors existing at the time of treatment, it is generally accepted that preventing the spread and metastasis of almost always fatal cancers such as HCC and thus, reducing it to a chronic and treatable disease can also be a successful therapeutic approach. The results in woodchucks warrant the investigation of JVRS-100 as an intervention to prevent liver cancer in patients chronically infected with HBV and at high risk for HCC development.

Hepatocellular carcinoma

The hepatitis B virus (HBV) is a widespread human pathogen that causes liver inflammation, cirrhosis, and hepatocellular carcinoma (HCC). Recent sequencing technologies have refined our knowledge of the genomic landscape and pathogenesis of HCC, but the mechanisms by which HBV exerts its oncogenic role remain controversial. In a prevailing view, inflammation, liver damage, and regeneration may foster the accumulation of genetic and epigenetic defects leading to cancer onset. However, a more direct and specific contribution of the virus is supported by clinical and biological observations. Among genetically heterogeneous HCCs, HBV-related tumors display high genomic instability, which may be attributed to the ability of HBV to integrate its DNA into the host cell genome, provoking chromosomal alterations and insertional mutagenesis of cancer genes. The viral transactivator HBx may also participate in transformation by deregulating diverse cellular machineries. A better understanding of the complex mechanisms linking HBV to HCC will improve prevention and treatment strategies.

Aging and HIV/AIDS: pathogenetic role of therapeutic side effects

The intersection of aging and HIV/AIDS is a looming 'epidemic within an epidemic.' This paper reviews how HIV/AIDS and its therapy cause premature aging or contribute mechanistically to HIV-associated non-AIDS illnesses (HANA). Survival with HIV/AIDS has markedly improved by therapy combinations containing nucleoside reverse transcriptase inhibitors (NRTIs), non-nucleoside reverse transcriptase inhibitors, and protease inhibitors (PIs) called HAART (highly active antiretroviral therapy). Because NRTIs and PIs together prevent or attenuate HIV-1 replication, and prolong life, the population of aging patients with HIV/AIDS increases accordingly. However, illnesses frequently associated with aging in the absence of HIV/AIDS appear to occur prematurely in HIV/AIDS patients. Theories that help to explain biological aging include oxidative stress (where mitochondrial oxidative injury exceeds antioxidant defense), chromosome telomere shortening with associated cellular senescence, and accumulation of lamin A precursors (a nuclear envelop protein). Each of these has the potential to be enhanced or caused by HIV/AIDS, antiretroviral therapy, or both. Antiretroviral therapy has been shown to enhance events seen in biological aging. Specifically, antiretroviral NRTIs cause mitochondrial dysfunction, oxidative stress, and mitochondrial DNA defects that resemble features of both HANA and aging. More recent clinical evidence points to telomere shortening caused by NRTI triphosphate-induced inhibition of telomerase, suggesting telomerase reverse transcriptase (TERT) inhibition as being a pathogenetic contributor to premature aging in HIV/AIDS. PIs may also have a role in premature aging in HIV/AIDS as they cause prelamin A accumulation. Overall, toxic side effects of HAART may both resemble and promote events of aging and are worthy of mechanistic studies.

The roles of hepatitis B virus-encoded X protein in virus replication and the pathogenesis of chronic liver disease

INTRODUCTION

Hepatitis B virus (HBV) is a major cause of chronic liver disease (CLD) and hepatocellular carcinoma (HCC) worldwide. More than 350 million people are at risk for HCC, and with few treatment options available, therapeutic approaches to targets other than the virus polymerase will be needed. This review suggests that the HBV-encoded X protein, HBx, would be an outstanding target because it contributes to the biology and pathogenesis of HBV in three fundamental ways.

AREAS COVERED

First, HBx is a trans-activating protein that stimulates virus gene expression and replication, thereby promoting the development and persistence of the carrier state. Second, HBx partially blocks the development of immune responses that would otherwise clear the virus, and protects infected hepatocytes from immune-mediated destruction. Thus, HBx contributes to the development of CLD without virus clearance. Third, HBx alters patterns of host gene expression that make possible the emergence of HCC. The selected literature cited is from the National Library of Medicine (Pubmed and Medline).

EXPERT OPINION

Understanding the mechanisms, whereby HBx supports virus replication and promotes pathogenesis, suggests that HBx will be an important therapeutic target against both virus replication and CLD aimed at the chemoprevention of HCC.

Roles of microRNAs in the hepatitis B virus infection and related diseases

The hepatitis B virus (HBV) is a small enveloped DNA virus that belongs to the Hepadnaviridae family. HBV can cause acute and persistent infection which can lead to hepatocellular carcinoma (HCC). MicroRNAs (miRNAs) play a crucial role in the main cellular events. The dysregulation of their expression has been linked to the development of the cancer as well as to viral interference. This chapter will describe the involvement of miRNAs in the case of HBV infection and their implication in the development of the HBV-related diseases.

[(Methyl)1-(11)c]-acetate metabolism in hepatocellular carcinoma

PURPOSE

Studies have established the value of [(methyl)1-(11)C]-acetate ([(11)C]Act) combined with 2-deoxy-2[(18)F]fluoro-D-glucose (FDG) for detecting hepatocellular carcinoma (HCC) using positron emission tomography (PET). In this study, the metabolic fate of [(11)C]Act in HCC was characterized.

METHODS

Experiments with acetic acid [1-(14)C] sodium salt ([(14)C]Act) were carried out on WCH-17 cells and freshly derived rat hepatocytes. PET scans with [(11)C]Act were also carried out on woodchucks with HCC before injection of [(14)C]Act. The radioactivity levels in different metabolites were quantified with thin-layer chromatography.

RESULTS

In WCH-17 cells, the predominant metabolite was phosphatidylcholine (PC). Regions of HCCs with the highest [(11)C]Act uptake had higher radioactivity accumulation in lipid-soluble compounds than surrounding hepatic tissues. In those regions, PC and triacylglycerol (TG) accumulated more radioactivity than in surrounding hepatic tissues.

CONCLUSIONS

High [(11)C]Act uptake in HCC is associated with increased de novo lipogenesis. PC and TG are the main metabolites into which the radioactive label from [(11)C]Act is incorporated in HCC.

Therapeutic vaccination in chronic hepatitis B: preclinical studies in the woodchuck

Recommended treatment of chronic hepatitis B with interferon-α and/or nucleos(t)ide analogues does not lead to a satisfactory result. Induction of HBV-specific T cells by therapeutic vaccination or immunotherapies may be an innovative strategy to overcome virus persistence. Vaccination with commercially available HBV vaccines in patients did not result in effective control of HBV infection, suggesting that new formulations of therapeutic vaccines are needed. The woodchuck (Marmota monax) is a useful preclinical model for developing the new therapeutic approaches in chronic hepadnaviral infections. Several innovative approaches combining antiviral treatments with nucleos(t)ide analogues, DNA vaccines, and protein vaccines were tested in the woodchuck model. In this paper we summarize the available data concerning therapeutic immunization and gene therapy using recombinant viral vectors approaches in woodchucks, which show encouraging results. In addition, we present potential innovations in immunomodulatory strategies to be evaluated in this animal model.

Combining antiangiogenic therapy with immunotherapy exerts better therapeutical effects on large tumors in a woodchuck hepatoma model

Cytokine and antiangiogenic gene therapies have proved effective in implanted hepatocellular carcinoma (HCC) models in which small tumor burdens were established in small rodents. These models, however, may not reflect human HCCs, which are frequently detected at a stage when tumors are large and multifocal. In addition, HCC in patients is often associated with viral hepatitis. To investigate the effectiveness of a mixture type of gene therapy strategy on large tumor burdens, we used the woodchuck model in which woodchuck hepatitis virus-induced HCCs are large and multifocal, simulating the conditions in humans. Adenoviruses encoding antiangiogenic factors (pigment epithelium-derived factor and endostatin) or cytokines (GM-CSF and IL-12) were delivered via the hepatic artery separately or in combination into woodchuck livers bearing HCCs. Our results showed that the mixture type of strategy, which contained two cytokines and two antiangiogenic factors, had better antitumor effects on large tumors as compared with monotherapy either with antiangiogenic or cytokine genes. The immunotherapy recruited significant levels of CD3(+) T cells that infiltrated the tumors, whereas the antiangiogenesis-based therapy significantly reduced tumor vasculature. The mixture type of gene therapy achieved both effects. In addition, it induced high levels of natural killer cells and apoptotic cells and reduced the levels of immunosuppressive effectors in the tumor regions. Hence, antiangiogenic therapy may provide the advantage of reducing immune tolerance in large tumors, making them more vulnerable to the immune reactions. Our study implies that in the future, the combination therapy may prove effective for the treatment of patients with advanced HCC.

Primary and secondary prevention of liver cancer caused by HBV

Primary cancer of the liver (hepatocellular carcinoma, HCC) is one of the most common cancers worldwide; HBV is the major cause of HCC. A vaccine that protects against HBV infection was invented in 1969 and is now one of the most commonly used vaccines. National vaccination programs have dramatically reduced the prevalence of HBV infection and carriers, with a concomitant decrease in the incidence of HCC in the vaccine-impacted populations. HBV vaccine is the first widely used cancer prevention vaccine; a second that protects against papilloma virus and cancer of the cervix has recently been introduced. Appropriate treatment of HBV carriers with antivirals can reduce the titers of HBV in their blood and thereby greatly reduce the risk of HCC and chronic liver disease. Further data are required to establish criterion for treatment to enable protocols for medical and prevention programs. There are other viral caused cancers and an understanding of their pathogenesis is an important future direction for research to reduce the human burden of cancer.

Semliki forest virus expressing interleukin-12 induces antiviral and antitumoral responses in woodchucks with chronic viral hepatitis and hepatocellular carcinoma

A vector based on Semliki Forest virus (SFV) expressing high levels of interleukin-12 (SFV-enhIL-12) has previously demonstrated potent antitumoral efficacy in small rodents with hepatocellular carcinoma (HCC) induced by transplantation of tumor cells. In the present study, the infectivity and antitumoral/antiviral effects of SFV vectors were evaluated in the clinically more relevant woodchuck model, in which primary HCC is induced by chronic infection with woodchuck hepatitis virus (WHV). Intratumoral injection of SFV vectors expressing luciferase or IL-12 resulted in high reporter gene activity within tumors and cytokine secretion into serum, respectively, demonstrating that SFV vectors infect woodchuck tumor cells. For evaluating antitumoral efficacy, woodchuck tumors were injected with increasing doses of SFV-enhIL-12, and tumor size was measured by ultrasonography following treatment. In five (83%) of six woodchucks, a dose-dependent, partial tumor remission was observed, with reductions in tumor volume of up to 80%, but tumor growth was restored thereafter. Intratumoral treatment further produced transient changes in WHV viremia and antigenemia, with >or=1.5-log(10) reductions in serum WHV DNA in half of the woodchucks. Antitumoral and antiviral effects were associated with T-cell responses to tumor and WHV antigens and with expression of CD4 and CD8 markers, gamma interferon, and tumor necrosis factor alpha in peripheral blood mononuclear cells, suggesting that immune responses against WHV and HCC had been induced. These experimental observations suggest that intratumoral administration of SFV-enhIL-12 may represent a strategy for treatment of chronic HBV infection and associated HCC in humans but indicate that this approach could benefit from further improvements.

Putative roles of hepatitis B x antigen in the pathogenesis of chronic liver disease

Under most circumstances, hepatitis B virus (HBV) is noncytopathic. However, hepatocellular regeneration that accompanies each bout of hepatitis appears to be associated with increased integration of HBV DNA fragments expressing the virus encoded hepatitis B x antigen (HBxAg). Intrahepatic HBxAg staining correlates with the intensity and progression of chronic liver disease (CLD), and additional work has shown that HBxAg blocks immune mediated killing by Fas and by tumor necrosis factor alpha (TNFalpha). This is not only associated with the blockage of caspase activities by HBxAg, but also by the constitutive stimulation of hepatoprotective pathways, such as nuclear factor kappa B (NF-kappaB), phosphoinositol 3-kinase (PI3K), and beta-catenin (beta-catenin). HBxAg also appears to promote fibrogenesis, by stimulating the production of fibronectin. HBxAg also stimulates the production and activity of transforming growth factor beta1 (TGFbeta1) by several mechanisms, thereby promoting the profibrogenic and tumorigenic properties of this important cytokine. In addition, HBxAg appears to remodel the extracellular matrix (ECM) by altering the expression of several matrix metalloproteinases (MMPs), which may promote tumor metastasis. Hence, HBxAg appears to promote chronic infection by preventing immune mediated apoptosis of infected hepatocytes, by promoting the establishment and persistence of fibrosis and cirrhosis preceding the development of HCC, and by promoting the remodeling of EMC during tumor progression.

HBV X protein: elucidating a role in oncogenesis

Chronic HBV infection is associated with the development of hepatocellular carcinoma (HCC). HBV contributes to tumorigenesis by encoding hepatitis B x antigen (HBxAg), which is a trans-regulatory protein that appears to contribute to HCC by altering patterns of host gene expression. In this review, recent data is presented that outlines some of the putative mechanisms whereby HBxAg contributes to HCC. With the development of animal models of HBxAg-mediated HCC, the relevance and temporal order of putative steps in this process can now be dissected to elucidate what is rate limiting and when. This will have a profound impact on the design of novel and specific therapeutics for HCC.

Elevated expression of the miR-17-92 polycistron and miR-21 in hepadnavirus-associated hepatocellular carcinoma contributes to the malignant phenotype

Alterations in microRNA (miRNA) expression in both human and animal models have been linked to many forms of cancer. Such miRNAs, which act directly as repressors of gene expression, have been found to frequently reside in fragile sites and genomic regions associated with cancer. This study describes a miRNA signature for human primary hepatitis B virus-positive human hepatocellular carcinoma. Moreover, two known oncomiRs--miRNAs with known roles in cancer--the miR-17-92 polycistron and miR-21, exhibited increased expression in 100% of primary human and woodchuck hepatocellular carcinomas surveyed. To determine the importance of these miRNAs in tumorigenesis, an in vitro antisense oligonucleotide knockdown model was evaluated for its ability to reverse the malignant phenotype. Both in human and woodchuck HCC cell lines, separate treatments with antisense oligonucleotides specific for either the miR-17-92 polycistron (all six members) or miR-21 caused a 50% reduction in both hepatocyte proliferation and anchorage-independent growth. The combination of assays presented here supports a role for these miRNAs in the maintenance of the malignant transformation of hepatocytes.

Host-range and pathogenicity of hepatitis B viruses

Hepatitis B viruses are small enveloped DNA viruses referred to as Hepadnaviridae that cause transient or persistent (chronic) infections of the liver. This family is divided into two genera, orthohepadnavirus and avihepadnavirus, which infect mammals or birds as natural hosts, respectively. They possess a narrow host range determined by the initial steps of viral attachment and entry. Hepatitis B virus is the focus of biomedical research owing to its medical significance. Approximately 2 billion people have serological evidence of hepatitis B, and of these approximately 350 million people have chronic infections (World Health Organisation, Fact Sheet WHO/204, October 2000). Depending on viral and host factors, the outcomes of infection with hepatitis B virus vary between acute hepatitis, mild or severe chronic hepatitis or cirrhosis. Chronic infections are associated with an increased risk for the development of hepatocellular carcinoma.

The hepatitis B x antigen effector, URG7, blocks tumour necrosis factor α-mediated apoptosis by activation of phosphoinositol 3-kinase and β-catenin

Hepatitis B x antigen (HBxAg) contributes significantly to the pathogenesis of chronic infection and development of hepatocellular carcinoma. To discern some of its operative pathways, HepG2 cells were stably transduced with HBx or the bacterial chloramphenicol acetyltransferase (CAT) gene. Differential gene expression has previously revealed an upregulated gene, clone 7 (URG7), that conferred resistance to anti-Fas killing on HepG2X cells. Given that tumour necrosis factor alpha (TNFα) is also an important mediator of chronic hepatitis, and partially shares signalling with Fas, experiments were designed to test whether URG7 blocks TNFα killing of HepG2X cells. HepG2X cells expressing URG7 and HepG2 cells overexpressing URG7 in the absence of HBxAg were resistant to TNFα killing compared with HepG2CAT cells. URG7 small interfering RNA restored the sensitivity of HepG2X cells to TNFα killing. Killing was associated with the activation of caspases 3 and 8, suggesting that URG7 blocked these caspases. This resistance was also associated with activation of phosphoinositol 3-kinase/Akt. Given that Akt and HBxAg also activate β-catenin, experiments were designed to determine whether URG7 blocked apoptosis via activation of β-catenin. Both HBxAg and URG7 activated fragments of the β-catenin promoter, and also promoted expression of β-catenin target genes. Hence, URG7 inhibits TNFα-mediated killing by blocking one or more caspases in the apoptotic pathway and by activating phosphoinositol 3-kinase and β-catenin, thereby overriding the apoptotic signalling of TNFα. This suggests that URG7 helps to protect virus-infected hepatocytes during chronic hepatitis B virus infection.

The role of the woodchuck model in the treatment of hepatitis B virus infection

Experimental studies of animals with chronic hepadnavirus infection could provide valuable insight into optimal therapeutic strategies for individuals with chronic HBV infection. In this review, we focus on the contributions of the woodchuck model to our understanding of HBV biology and on its role in the development of antiviral drug. Furthermore, we consider the implications of studies focusing on the natural history of WHV infection for the management of HBV and the capacity of treatment to prevent complications of chronic hepatitis B infection.

Hepatitis B virus infection, the immune response and hepatocellular carcinoma

More than 250 million people worldwide are chronically infected with the hepatitis B virus (HBV) and have a 200-fold increased risk of developing hepatocellular carcinoma (HCC). This is one of the most common cancers in the world with a geographical distribution highest in areas where HBV is endemic. A number of molecular mechanisms have been proposed to explain this correlation including an acutely transforming viral oncogene; chromosomal aberrations due to HBV integration (i.e. deletions, translocations, duplications); activation of cellular proto-oncogenes; inactivation of cellular anti-oncogenes; and transactivation of cellular genes by HBV gene products. HCC usually develops only after 20-30 years of persistent HBV infection accompanied by hepatocyte necrosis, inflammation and regenerative hyperplasia. Because HBV is not directly cytopathic, liver injury must be immune mediated. Factors that predispose HBV-infected individuals to develop HCC are chronicity, an immune response and liver injury rather than a direct genetic event. Hepatic injury and continuous hepatocyte regeneration may allow an accumulation of multiple mutational events sufficient for the emergence of HCC. Pathways which lead to chronicity, the immune response during HBV infection, mechanisms of pathogenesis and methods to prevent HBV infection are all relevant to the development of HCC. Recent studies characterizing the humoral and cellular immune responses in patients chronically infected with HBV and transgenic mouse models of HBV-specific immune tolerance and pathogenesis are providing new insights into the complex association between HBV infection and HCC.

The liver of woodchucks chronically infected with the woodchuck hepatitis virus contains foci of virus core antigen-negative hepatocytes with both altered and normal morphology

The livers of woodchucks chronically infected with woodchuck hepatitis virus (WHV) contain foci of morphologically altered hepatocytes (FAH) with "basophilic", "amphophilic" and "clear cell" phenotypes, which are possibly pre-neoplastic in nature. Interestingly, most fail to express detectable levels of WHV proteins and nucleic acids. We studied sections of WHV-infected liver tissue to determine if all foci of hepatocytes that failed to express detectable levels of WHV, as assessed by immunoperoxidase staining for WHV core antigen, could be classified morphologically as FAH. We found that at least half of the foci of WHV core antigen-negative hepatocytes did not show clear morphological differences in either H&E or PAS (periodic acid Schiff) stained sections from surrounding hepatocytes, and were therefore not designated as FAH. In the second approach, we assayed core antigen-negative foci for the presence of fetuin B, a serum protein produced by normal hepatocytes, but not by neoplastic hepatocytes in hepatocellular carcinomas. Basophilic and amphophilic FAH had reduced levels of fetuin B compared to hepatocytes present in the surrounding liver; fetuin B staining was detected in clear cell FAH but the level could not be accurately assessed because of the displacement of fetuin B to the cell periphery by accumulated glycogen. The foci of morphologically normal WHV core antigen-negative hepatocytes had similar levels of fetuin B to that of the surrounding hepatocytes. The co-existence of at least four types of WHV core antigen-negative foci, including those with no obvious morphologic changes, raises the possibility that the different foci arise from distinct primary events. We hypothesize that a common event is loss of the ability to express WHV, allowing these hepatocytes to escape immune mediated cell death and to undergo clonal expansion to form distinct foci.

The woodchuck as an animal model for pathogenesis and therapy of chronic hepatitis B virus infection

This review describes the woodchuck and the woodchuck hepatitis virus (WHV) as an animal model for pathogenesis and therapy of chronic hepatitis B virus (HBV) infection and disease in humans. The establishment of woodchuck breeding colonies, and use of laboratory-reared woodchucks infected with defined WHV inocula, have enhanced our understanding of the virology and immunology of HBV infection and disease pathogenesis, including major sequelae like chronic hepatitis and hepatocellular carcinoma. The role of persistent WHV infection and of viral load on the natural history of infection and disease progression has been firmly established along the way. More recently, the model has shed new light on the role of host immune responses in these natural processes, and on how the immune system of the chronic carrier can be manipulated therapeutically to reduce or delay serious disease sequelae through induction of the recovery phenotype. The woodchuck is an outbred species and is not well defined immunologically due to a limitation of available host markers. However, the recent development of several key host response assays for woodchucks provides experimental opportunities for further mechanistic studies of outcome predictors in neonatal- and adult-acquired infections. Understanding the virological and immunological mechanisms responsible for resolution of self-limited infection, and for the onset and maintenance of chronic infection, will greatly facilitate the development of successful strategies for the therapeutic eradication of established chronic HBV infection. Likewise, the results of drug efficacy and toxicity studies in the chronic carrier woodchucks are predictive for responses of patients chronically infected with HBV. Therefore, chronic WHV carrier woodchucks provide a well-characterized mammalian model for preclinical evaluation of the safety and efficacy of drug candidates, experimental therapeutic vaccines, and immunomodulators for the treatment and prevention of HBV disease sequelae.

Lack of WHV integration nearby N-myc2 and in the downstream b3n and win loci in a considerable fraction of liver tumors with activated N-myc2 from naturally infected wild woodchucks

In liver tumors induced by chronic WHV infection in the WHV/woodchuck model of HBV infection, activation of genes of the myc family by WHV insertion has been well documented. Several studies have shown that N-myc2 is by far the most frequently involved, and in most cases, its transcriptional activation is due to WHV insertion nearby the gene. N-myc2 has been shown to be also activated by WHV insertion in two downstream loci, b3n and win. Although the extent of insertion in these latter loci in woodchuck tumors has not been investigated, their discovery has led to the notion that therein WHV insertion accounts for N-myc2 activation in the remaining tumors expressing the proto-oncogene in absence of any detectable alteration nearby the gene, a notion remained unproved and not further investigated yet. In the majority of cases, the above observations were derived from tumors developed in colony born laboratory bred woodchucks experimentally infected with standardized viral inocula, mostly of the same lineage. In the present work, we investigated a survey of liver tumors naturally developed in wild woodchucks with naturally acquired chronic WHV infection. Tumors had histological features of well to moderately differentiated HCCs. In most animals, multiple tumor nodules were observed; in the great majority of cases, they were shown to be independent tumors because their WHV integration patterns were not clonally related. 53 independent tumors were investigated for N-myc activation and WHV integration nearby N-myc genes and in the b3n and win loci. Comparison of our results with data from previous studies revealed that, in tumors from naturally infected wild woodchucks, the frequency of WHV integration nearby N-myc2 has a tendency to be lower and, in addition, N-myc2 activation is due to WHV integration nearby the gene significantly less frequently than in tumors from experimentally infected colony born animals (12/28, 43% vs. 15/20, 75%, P = 0.0397). These findings are likely related to the less uniform conditions as to infecting virus and host genetic background in naturally infected wild woodchucks with respect to experimentally infected colony born woodchucks and suggest that viral and/or host factors may influence the site of viral insertion finally detected in overt tumors. In addition, more than one third (11/28, 39%) tumors with activated N-myc2 transcription did not show rearrangement either nearby the gene, or in b3n or in win. These findings challenge the notion that integration in the downstream b3n and win loci is responsible for N-myc2 activation in tumors lacking insertion nearby N-myc2 and suggest that in a considerable fraction of liver tumors, at least from wild woodchucks, N-myc2 activation might be due either to WHV integration in further regions of the N-myc2 chromosomal domain or to other mechanisms related or unrelated to viral insertion.

Comparison of biological activity of recombinant woodchuck interferon gamma and tumor necrosis factor alpha produced in baculovirus and Escherichia coli expression systems

The full-length cDNAs of recombinant woodchuck interferon gamma (rwIFN gamma) and woodchuck tumor necrosis factor alpha (rwTNF alpha) were cloned into baculovirus transfer vectors and expressed in insect Sf9 cells. The recombinant proteins secreted by the insect cells, bac-rwIFN gamma and bac-rwTNF alpha, were found to be functionally competent. Their biological activities were compared to those of rwIFN gamma and rwTNF alpha produced in the Escherichia coli (E. coli) expression system. The bac-rwIFN gamma demonstrated a 4.5-fold greater protective activity against encephalomyocarditis virus-induced cytolysis of woodchuck hepatocytes and that of class I MHC antigen presentation on the hepatocytes than rwIFN gamma derived from E. coli. The bac-rwTNF alpha was cytotoxic towards murine fibroblasts and able to upregulate class I MHC antigen display and these effects were about 18-fold greater than those triggered by rwTNF alpha from E. coli at a comparable protein level. In addition, the antiviral activity of bac-rwIFN gamma was inhibited by anti-wIFN gamma antibodies and the cytotoxicity of bac-rwTNF alpha neutralized by cross-reactive antibodies to murine TNF alpha. The study showed that the expression of rwIFN gamma and rwTNF alpha in the baculovirus system generated biologically active cytokines whose potency was considerably greater than those produced in E. coli.

Epidemiology and natural history of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a major contributor to cancer incidence and mortality. There is a wide variation, however, in the global distribution of HCC. Eighty percent of the burden is borne by countries in Asia and sub-Saharan Africa. In most high-risk countries, principal risk factors include infection with hepatitis B virus and dietary exposure to aflatoxin B(1). In contrast, hepatitis C virus and alcohol consumption are more important risk factors in low-risk countries. In recent years, the incidence of HCC has decreased in some high-risk countries and increased in some low-risk countries. Reasons for both trends are not completely understood, but are likely related to public health efforts in Asia and the increase in hepatitis C virus infection in low-risk countries. Vaccination programs against hepatitis B virus will likely decrease the HCC rate even further in decades to come.

The win locus involved in activation of the distal N-myc2 gene upon WHV integration in woodchuck liver tumors harbors S/MAR elements

Woodchuck hepatitis virus (WHV) and the woodchuck (Marmota monax) are models for hepatocellular carcinoma (HCC) induced by hepatitis B virus (HBV). In woodchuck liver tumors, the N-myc2 proto-oncogene is frequently activated by WHV integration either close to the gene or in the b3n and win downstream loci, located 10 and 150 kb from N-myc2, respectively. A scaffold/matrix attachment region (S/MAR) regulative element was shown to be in b3n, possibly mediating activation of the upstream N-myc2 gene upon WHV integration. To investigate if S/MAR elements are in win too, a 17-kb DNA fragment corresponding to the major region of WHV insertion in this locus was cloned and sequenced. Overlapping subcloned fragments spanning candidate S/MARs predicted by sequence analysis were tested by standard in vitro binding assays. Results showed the presence of two S/MAR elements in win. The distribution of previously described WHV insertions relative to the S/MARs reinforces the hypothesis that S/MARs nearby distal WHV insertions might be involved in long-range activation of N-myc2.

Oxidative stress in viral hepatitis and AIDS

Dominant types of viral hepatitis are presently A, B, and C with prophylactic immunization available only for A and B. Hepatitis B and C and human immunodeficiency virus (HIV) infection constitute a worldwide scourge and treatment is far from satisfactory. Each produces severe oxidative stress (OS) and secondary cellular damage of varying severity and, as in toxic hepatitis, progression and regression are dependent on redox balance between oxidation and antioxidation. Experimental and clinical studies suggest that xenobiotics and co-infections exert cumulative, detrimental effects on their pathogeneses and further deplete antioxidants. It is proposed therefore that in the clinical management of these infections and especially in their early stages, considerable benefit should accrue from antioxidant repletion at dosages substantially above recommended daily allowances (RDAs) in conjunction with a nutritious high protein diet. Because plasma zinc and selenium concentrations are very low, their replenishment by high dosages is urgent and mandatory particularly in advanced HIV infections bordering on acrodermatitis enteropathica. Also recommended is their long-term continuance at high normal levels.

Hepatocellular carcinoma in the woodchuck model of hepatitis B virus infection

The Eastern woodchuck ( Marmota monax ) harbors a DNA virus (Woodchuck hepatitis virus [WHV]) that is similar in structure and replicative life cycle to the human hepatitis B virus (HBV). Like HBV, WHV infects the liver and can cause acute and chronic hepatitis. Furthermore, chronic WHV infection in woodchucks usually leads to development of hepatocellular carcinoma (HCC) within the first 2-4 years of life. The woodchuck model has been important in the preclinical evaluation of safety and efficacy of the antiviral drugs now in use for treatment of HBV infection and continues to serve as an important, predictive model for innovative forms of therapy of hepatitis B using antiviral nucleosides and immune response modifiers alone or in combination. Almost all woodchucks that become chronic WHV carriers after experimental neonatal inoculation develop HCC with a median HCC-free survival of 24 months and a median life expectancy of 30-32 months. The woodchuck model of viral-induced HCC has been used effectively for the development of new imaging agents for enhancement of detection of hepatic neoplasms by ultrasound and magnetic resonance imaging. The chemoprevention of HCC using long-term antiviral nucleoside therapy has been shown in the woodchuck, and "proof of principal" has been established for some of the innovative, molecular methods for treatment of HCC. The model is available for fundamental investigations of the viral and molecular mechanisms responsible for hepatocarcinogenesis and should have substantial value for future development of innovative methods for chemoprevention and gene therapy of human HCC.

Preneoplastic Markers of Hepatitis B Virus-Associated Hepatocellular Carcinoma

Hepatitis B virus (HBV) carriers are at high risk for the development of hepatocellular carcinoma (HCC), but there are no reliable markers that will identify such high-risk carriers. The objective of this work is to identify serologic markers that may indicate the early presence of HCC. Since HBV-encoded X antigen (HBxAg) likely contributes to HCC by up- or down-regulation of host gene expression, X positive and negative HepG2 cells were made and subjected to cDNA subtraction. When specific ELISAs were constructed measuring differentially expressed antigens and corresponding antibodies, antibodies to several differentially expressed genes were detected. In cross-sectional and longitudinal studies, antibodies were predominantly present in patients with HBV-associated cirrhosis and HCC, but not in most carriers with hepatic inflammation alone or without active liver disease. Antibodies were also present in patients with hepatitis C virus (HCV)-related HCC, but rarely detected in sera from uninfected individuals, those with tumors other than HCC, or those with drug-induced hepatitis. Statistical analysis showed that HCC patients with four or more antibodies detectable before the appearance of HCC had decreased survival, suggesting that these markers may reflect stepwise hepatocarcinogenesis. Hence, these antibodies may serve as preneoplastic markers for HCC in HBV carriers with chronic liver disease, and may be identified by a simple blood test.

Cell culture and animal models of viral hepatitis. Part I: hepatitis B

Despite the existence of a preventative vaccine, HBV represents a substantial threat to public health, suggesting the need for research to develop new treatments to combat the disease. The authors review the available in vitro and in vivo models, including recently developed transgenic and chimeric mouse models.

Interferon-gamma-associated responses to woodchuck hepatitis virus infection in neonatal woodchucks and virus-infected hepatocytes

Acute hepatitis and recovery from woodchuck hepatitis virus (WHV) infection involves increased intrahepatic expression of interferon-gamma (IFN-gamma) and tumour necrosis factor-alpha (TNF-alpha) mRNAs. In the present study, recovery correlated with increased intrahepatic expression of mRNAs for major histocompatibility complex class 1 (MHC1), beta(2)-microglobulin, 2'5'-oligoadenylate synthetase (2'5'-OAS), and indoleamine dioxygenase (IDO). By comparison, acute WHV infection progressing to chronicity was associated with diminished expression of these IFN-gamma-associated mRNAs in liver. Transfection of WHV-infected primary hepatocytes (WPH) from WHV carriers with an IFN-gamma-expressing plasmid (pIFN-gamma) resulted in dose-dependent accumulations of MHC1, TNF-alpha, 2'5'-OAS, and IDO mRNAs within 96 h. Markers of T cells and immune-mediated cytotoxicity that accumulate in recovering liver were not apparent in WPH based on the relative lack of CD3, CD4, Fas ligand, perforin, and granzyme B mRNAs. Expression of pIFN-gamma, and TNF-alpha-expressing plasmid (pTNF-alpha), did not affect total WHV RNA, or fully double-stranded WHV DNA in WPH, but each reduced some of the replicative intermediate (RI) species of WHV DNA synthesis. WPH treated with recombinant IFN-alpha protein had a higher fold induction of 2'5'-OAS mRNA associated with partial reductions in WHV RNAs and the major RI species. Thus, IFN-gamma expression in carrier WPH induced several host responses often observed in liver of recovering woodchucks, and impaired a stage of WHV DNA synthesis by a non-cytolytic mechanism mediated by TNF-alpha. Local enhancement of IFN-gamma-associated responses in chronic WHV-infected hepatocytes may promote therapeutic antiviral effects, but additional effector mechanisms evident during recovery appear necessary for more complete clearance of WHV infection.

Kinetics of viremia and acute liver injury in relation to outcome of neonatal woodchuck hepatitis virus infection

The kinetics of serum viral responses and acute liver injury were studied during neonatal woodchuck hepatitis virus (WHV) infection in relation to the chronic or resolved outcome. The mean concentrations of serum WHV DNA and surface antigen were significantly higher by week 10 post infection in chronic infections compared to resolving infections, and diverged even further by the time of peak viral load development in serum (week 12). After week 12, these viral markers were detected less frequently with time and at lower concentrations in the resolved outcome. In both outcomes, mean serum activities of hepatic enzymes became increased significantly above baseline by weeks 10-12, peaked at week 14, and normalized by weeks 20-22, thus indicating transient acute liver injury. The increasing liver injury responses were comparable between outcomes at week 12, when serum viral load was markedly higher in the developing chronic infections. This suggested a deficiency in early non-cytolytic control of infection in the chronic outcome. At week 14, liver injury was significantly greater in the resolved outcome and associated with higher mean Fas ligand (FasL) and perforin messenger RNAs (mRNAs) in liver compared to the chronic outcome. This indicated greater immune-mediated killing of infected hepatocytes during resolution. Thus, chronicity as an outcome of neonatal WHV infection develops relatively early during the acute phase of infection due to reduced immune-mediated clearance of infected hepatocytes by both cytolytic and non-cytolytic processes.

Scaffold attachment region located in a locus targeted by hepadnavirus integration in hepatocellular carcinomas

The role of viral integration in HBV induced hepatocellular carcinoma (HCC) is still controversial. In the WHV/woodchuck animal model, WHV integration was found to activate the N-myc2 oncogene either by enhancer insertion in proximity of the gene, or by integration in a distantly located uncoding locus, win. In addition, we have reported that N-myc2 activation also results from WHV integration in the b3n locus, located several kilobases downstream of N-myc2. In this work we report the search for function(s) of the b3n locus that might be possibly affected by WHV integration and indirectly activate N-myc2. A 0.5 kb region of the sequence of this locus exhibited unusual features, typical of scaffold/matrix attachment regions (S/MAR). Standard in vitro binding assays are commonly used to assess if a DNA fragment is a S/MAR. DNA fragments cloned from the b3n locus were tested for in vitro binding affinity for both heterologous and autologous nuclear scaffold preparations. Only the fragment spanning the region rich of S/MAR motifs was found to bind specifically nuclear scaffolds, thus demonstrating that a S/MAR element is present in the b3n locus. Based on these findings, we speculate that WHV integration might deregulate the S/MAR element and indirectly affect the expression of the N-myc2 gene located upstream of the S/MAR. Our findings also suggest that the role of HBV integration should be reconsidered, because a similar mechanism has not been investigated to date in human HCC.

Mutations within the hepatitis B virus genome among chronic hepatitis B patients with hepatocellular carcinoma

Chronic hepatitis B infection is a major cause of hepatocellular cancer (HCC). The pathogenesis of the carcinogenesis is not fully understood. Viral proteins such as the X protein and the truncated middle S protein have been implicated to be transactivators. In order to investigate whether any mutations within relevant parts of the hepatitis B virus (HBV) genome could be associated with the development of HCC, the genomes of 16 HBV strains from chronic HBV carriers with HCC were studied. Serum samples were subjected to PCR and the HBV DNA sequenced subsequently. Genotypes A-D were represented. The sequence analysis showed that an especially high proportion, 50% (CI 95%, 25-75%), of the patients with HCC carried HBV mutants with deletions or insertions in the N-terminal half of the pre-S2 region or had a point mutation in the start codon of pre-S2 compared with controls with chronic HBV infection, 21% (CI 95%, 3-39%). A high proportion (69%) also had mutations at position 1762 (A --> T) and/or 1764 (G --> A) in the core promoter region, but the proportion of core promoter mutations was no different from what was found in a control group of HBV carriers without HCC (68%). The pre-S2 variants, which involve deletions of immunogenic regions, may have a survival advantage as they are mostly found in long-standing HBV infection. There were no other mutations found frequently within the region coding for the X protein.