Mitogen-induced replication of woodchuck hepatitis virus in cultured peripheral blood lymphocytes

Gut virome-colonising Orthohepadnavirus genus is associated with ulcerative colitis pathogenesis and induces intestinal inflammation in vivo

OBJECTIVES

Ulcerative colitis (UC) is a chronic inflammatory disorder of unknown aetiology. Gut virome dysbiosis is fundamental in UC progression, although its role in the early phases of the disease is far from fully understood. Therefore, we sought to investigate the role of a virome-associated protein encoded by the Orthohepadnavirus genus, the hepatitis B virus X protein (HBx), in UC aetiopathogenesis.

DESIGN

HBx positivity of UC patient-derived blood and gut mucosa was assessed by RT-PCR and Sanger sequencing and correlated with clinical characteristics by multivariate analysis. Transcriptomics was performed on HBx-overexpressing endoscopic biopsies from healthy donors.C57BL/6 mice underwent intramucosal injections of liposome-conjugated HBx-encoding plasmids or the control, with or without antibiotic treatment. Multidimensional flow cytometry analysis was performed on colonic samples from HBx-treated and control animals. Transepithelial electrical resistance measurement, proliferation assay, chromatin immunoprecipitation assay with sequencing and RNA-sequencing were performed on in vitro models of the gut barrier. HBx-silencing experiments were performed in vitro and in vivo.

RESULTS

HBx was detected in about 45% of patients with UC and found to induce colonic inflammation in mice, while its silencing reverted the colitis phenotype in vivo. HBx acted as a transcriptional regulator in epithelial cells, provoking barrier leakage and altering both innate and adaptive mucosal immunity ex vivo and in vivo.

CONCLUSION

This study described HBx as a contributor to the UC pathogenesis and provides a new perspective on the virome as a target for tailored treatments.

New insights into hepatitis B virus lymphotropism: Implications for HBV-related lymphomagenesis

HBV is one of the most widespread hepatitis viruses worldwide, and a correlation between chronic infection and liver cancer has been clearly reported. The carcinogenic capacity of HBV has been reported for other solid tumors, but the largest number of studies focus on its possible lymphomagenic role. To update the correlation between HBV infection and the occurrence of lymphatic or hematologic malignancies, the most recent evidence from epidemiological and in vitro studies has been reported. In the context of hematological malignancies, the strongest epidemiological correlations are with the emergence of lymphomas, in particular non-Hodgkin's lymphoma (NHL) (HR 2.10 [95% CI 1.34-3.31], p=0.001) and, more specifically, all NHL B subtypes (HR 2.14 [95% CI 1.61-2.07], p<0.001). Questionable and unconfirmed associations are reported between HBV and NHL T subtypes (HR 1.11 [95% CI 0.88-1.40], p=0.40) and leukemia. The presence of HBV DNA in peripheral blood mononuclear cells has been reported by numerous studies, and its integration in the exonic regions of some genes is considered a possible source of carcinogenesis. Some in vitro studies have shown the ability of HBV to infect, albeit not productively, both lymphomonocytes and bone marrow stem cells, whose differentiation is halted by the virus. As demonstrated in animal models, HBV infection of blood cells and the persistence of HBV DNA in peripheral lymphomonocytes and bone marrow stem cells suggests that these cellular compartments may act as HBV reservoirs, allowing replication to resume later in the immunocompromised patients (such as liver transplant recipients) or in subjects discontinuing effective antiviral therapy. The pathogenetic mechanisms at the basis of HBV carcinogenic potential are not known, and more in-depth studies are needed, considering that a clear correlation between chronic HBV infection and hematological malignancies could benefit both antiviral drugs and vaccines.

Hepadnaviral Lymphotropism and Its Relevance to HBV Persistence and Pathogenesis

Since the discovery of hepatitis B virus (HBV) over five decades ago, there have been many independent studies showing presence of HBV genomes in cells of the immune system. However, the nature of HBV lymphotropism and its significance with respect to HBV biology, persistence and the pathogenesis of liver and extrahepatic disorders remains underappreciated. This is in contrast to studies of other viral pathogens in which the capability to infect immune cells is an area of active investigation. Indeed, in some viral infections, lymphotropism may be essential, and even a primary mechanism of viral persistence, and a major contributor to disease pathogenesis. Nevertheless, there are advances in understanding of HBV lymphotropism in recent years due to cumulative evidence showing that: (i) lymphoid cells are a reservoir of replicating HBV, (ii) are a site of HBV-host DNA integration and (iii) virus genomic diversification leading to pathogenic variants, and (iv) they play a role in HBV resistance to antiviral therapy and (v) likely contribute to reactivation of hepatitis B. Further support for HBV lymphotropic nature is provided by studies in a model infection with the closely related woodchuck hepatitis virus (WHV) naturally infecting susceptible marmots. This animal model faithfully reproduces many aspects of HBV biology, including its replication scheme, tissue tropism, and induction of both symptomatic and silent infections, immunological processes accompanying infection, and progressing liver disease culminating in hepatocellular carcinoma. The most robust evidence came from the ability of WHV to establish persistent infection of the immune system that may not engage the liver when small quantities of virus are experimentally administered or naturally transmitted into virus-naïve animals. Although the concept of HBV lymphotropism is not new, it remains controversial and not accepted by conventional HBV researchers. This review summarizes research advances on HBV and hepadnaviral lymphotropism including the role of immune cells infection in viral persistence and the pathogenesis of HBV-induced liver and extrahepatic diseases. Finally, we discuss the role of immune cells in HBV diagnosis and assessment of antiviral therapy efficacy.

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.

Impact of Hepatitis B Virus Genetic Variation, Integration, and Lymphotropism in Antiviral Treatment and Oncogenesis

Chronic Hepatitis B Virus (HBV) infection poses a significant global health burden. Although, effective treatment and vaccinations against HBV are available, challenges still exist, particularly in the development of curative therapies. The dynamic nature and unique features of HBV such as viral variants, integration of HBV DNA into host chromosomes, and extrahepatic reservoirs are considerations towards understanding the virus biology and developing improved anti-HBV treatments. In this review, we highlight the importance of these viral characteristics in the context of treatment and oncogenesis. Viral genotype and genetic variants can serve as important predictive factors for therapeutic response and outcomes in addition to oncogenic risk. HBV integration, particularly in coding genes, is implicated in the development of hepatocellular carcinoma. Furthermore, we will discuss emerging research that has identified various HBV nucleic acids and infection markers within extrahepatic sites (lymphoid cells). Intriguingly, the presence of hepatocellular carcinoma (HCC)-associated HBV variants and viral integration within the lymphoid cells may contribute towards the development of extrahepatic malignancies. Improved understanding of these HBV characteristics will enhance the development of a cure for chronic HBV infection.

Diverse Virus and Host-Dependent Mechanisms Influence the Systemic and Intrahepatic Immune Responses in the Woodchuck Model of Hepatitis B

Woodchuck infected with woodchuck hepatitis virus (WHV) represents the pathogenically nearest model of hepatitis B and associated hepatocellular carcinoma (HCC). This naturally occurring animal model also is highly valuable for development and preclinical evaluation of new anti-HBV agents and immunotherapies against chronic hepatitis (CH) B and HCC. Studies in this system uncovered a number of molecular and immunological processes which contribute or likely contribute to the immunopathogenesis of liver disease and modulation of the systemic and intrahepatic innate and adaptive immune responses during hepadnaviral infection. Among them, inhibition of presentation of the class I major histocompatibility complex on chronically infected hepatocytes and a role of WHV envelope proteins in this process, as well as augmented hepatocyte cytotoxicity mediated by constitutively expressed components of CD95 (Fas) ligand- and perforin-dependent pathways, capable of eliminating cells brought to contact with hepatocyte surface, including activated T lymphocytes, were uncovered. Other findings pointed to a role of autoimmune response against hepatocyte asialoglycoprotein receptor in augmenting severity of liver damage in hepadnaviral CH. It was also documented that WHV in the first few hours activates intrahepatic innate immunity that transiently decreases hepatic virus load. However, this activation is not translated in a timely manner to induction of virus-specific T cell response which appears to be hindered by defective activation of antigen presenting cells and presentation of viral epitopes to T cells. The early WHV infection also induces generalized polyclonal activation of T cells that precedes emergence of virus-specific T lymphocyte reactivity. The combination of these mechanisms hinder recognition of virus allowing its dissemination in the initial, asymptomatic stages of infection before adaptive cellular response became apparent. This review will highlight a range of diverse mechanisms uncovered in the woodchuck model which affect effectiveness of the anti-viral systemic and intrahepatic immune responses, and modify liver disease outcomes. Further exploration of these and other mechanisms, either already discovered or yet unknown, and their interactions should bring more comprehensive understanding of HBV pathogenesis and help to identify novel targets for therapeutic and preventive interventions. The woodchuck model is uniquely positioned to further contribute to these advances.

Lipopolysaccharide enhances human herpesvirus 1 replication and IL-6 release in epithelial cells

OBJECTIVE

To investigate the effect of lipopolysaccharide (LPS) on human herpesvirus 1 (HHV-1) infection in epithelial cells.

METHODS

Two strains of HHV-1, HHV-1 F strain (HHV-1f) and HHV-1 strain-H129 with GFP knock-in (HHV-g4), were used to infect HCE-T and VERO cells at MOIs of 0.04 and 0.02, respectively. After 1 h, 0, 10, 50, and 100 μg/ml LPS was added to serum-free medium and the cells were cultured for up to 24 h. GFP fluorescence of HHV-g4 in cells was examined under a fluorescence microscope and imaged. HHV-1f titer was determined by quantitative real-time polymerase chain reaction (qPCR) in HCE-T cells and plaque assays in VERO cells. The expression of the viral ICP4 protein of HHV-1f was detected by Western blot assay. IL-6 and IL-10 levels in culture medium were determined by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Similar changes but at different degrees were found in HCE-T and VERO cells that were infected with HHV-1. GFP fluorescence of HHV-g4 and cell lesions increased in a dose-dependent manner. Virus titer was also enhanced by LPS stimulation in HCE-T and VERO cells. ICP4 expression was promoted at higher LPS concentrations (P = 0.04). In addition, viral infection resulted in increased expression of IL-6 in a dose-dependent manner at 12 and 24 h (P = 0.01), while IL-10 expression was unaffected by either HHV-1 infection or LPS stimulation.

CONCLUSION

LPS promotes HHV-1 infection in epithelial cells, which suggests that gram-negative bacteria on ocular surfaces may aggravate HHV-1 infection.

Deciphering the mystery of hepatitis B virus receptors: A historical perspective

Hepatitis B virus is one of the major reasons of viral hepatitis with an estimated 350 million infected patients worldwide. Although, the virus was discovered and cloned more than three decades ago, its entry mechanism has still been in investigation. Numerous potential candidates have been proposed and investigated rigorously to reveal HBV entry mechanism and to unveil the first door of viral entry to hepatocytes. This review provides a short account of role of receptors for entry of HBV into hepatocytes. The viral preS1 region of large surface protein is involved in the attachment of HBV to hepatocytes. The putative attachment site of HBV is located at amino acids 21-47 of preS1. So far, several proteins have been proposed to interact with these different regions of the preS1 domain which includes human immunoglobulin A receptor, glyceraldehyde-3-phosphate dehydrogenase, interleukin-6, a 31-kDa protein, HBV binding factor, asialoglycoprotein receptor, nascent polypeptide-associated complex α polypeptide, lipoprotein lipase, hepatocyte-associated heparan sulfate proteoglycans, glucose-regulated protein 75. However, none of them have appeared to be generally accepted as a true receptor for the virus until recently when sodium taurocholate cotransporting polypeptide identified as HBV entry receptor. Current review provides scientific historical perspective of various candidates known to be interacting with preS1 of HBV for their possible role in viral entry.

Therapeutic strategies for a functional cure of chronic hepatitis B virus infection

Treatment of chronic hepatitis B virus (HBV) infection with the viral DNA polymerase inhibitors or pegylated alpha-interferon has led to a significant retardation in HBV-related disease progression and reduction in mortality related to chronic hepatitis B associated liver decompensation and hepatocellular carcinoma. However, chronic HBV infection remains not cured. The reasons for the failure to eradicate HBV infection by long-term antiviral therapy are not completely understood. However, clinical studies suggest that the intrinsic stability of the nuclear form of viral genome, the covalently closed circular (ccc) DNA, sustained low level viral replication under antiviral therapy and homeostatic proliferation of hepatocytes are the critical virological and pathophysiological factors that affect the persistence and therapeutic outcomes of HBV infection. More importantly, despite potent suppression of HBV replication in livers of the treated patients, the dysfunction of HBV-specific antiviral immunity persists. The inability of the immune system to recognize cells harboring HBV infection and to cure or eliminate cells actively producing virus is the biggest challenge to finding a cure. Unraveling the complex virus–host interactions that lead to persistent infection should facilitate the rational design of antivirals and immunotherapeutics to cure chronic HBV infection.

Pathogenesis of occult chronic hepatitis B virus infection

Occult hepatitis B infection (OBI) is characterized by hepatitis B virus (HBV) DNA in serum in the absence of hepatitis B surface antigen (HBsAg) presenting HBsAg-negative and anti-HBc positive serological patterns. Occult HBV status is associated in some cases with mutant viruses undetectable by HBsAg assays; but more frequently it is due to a strong suppression of viral replication and gene expression. OBI is an entity with world-wide diffusion. The failure to detect HBsAg, despite the persistence of the viral DNA, is due in most cases to the strong suppression of viral replication and gene expression that characterizes this “occult” HBV infection; although the mechanisms responsible for suppression of HBV are not well understood. The majority of OBI cases are secondary to overt HBV infection and represent a residual low viremia level suppressed by a strong immune response together with histological derangements which occurred during acute or chronic HBV infection. Much evidence suggests that it can favour the progression of liver fibrosis and the development of hepatocellular carcinoma.

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.

Lipopolysaccharide-induced innate immune responses in primary hepatocytes downregulates woodchuck hepatitis virus replication via interferon-independent pathways

Our previous studies have shown that Toll-like receptor (TLR) ligands, Poly I:C and lipopolysaccharide (LPS), are able to activate non-parenchymal liver cells and trigger the production of interferon (IFN) to inhibit hepatitis B virus replication in vivo and in vitro. However, little is known about TLR-mediated cellular responses in primary hepatocytes. By the model of woodchuck hepatitis virus (WHV) infected primary woodchuck hepatocytes (PWHs), Poly I:C and LPS stimulation resulted in upregulation of cellular antiviral genes and relevant TLRs mRNA expression respectively. LPS stimulation led to a pronounced reduction of WHV replicative intermediates without a significant IFN induction. Poly I:C transfection resulted in the production of IFN and a highly increased expression of antiviral genes in PWHs and slight inhibitory effect on WHV replication. LPS could activate nuclear factor kappa B, MAPK and PI-3k/Akt pathways in PWHs. Further, inhibitors of MAPK-ERK and PI-3k/Akt pathways, but not that of IFN signalling pathway, were able to block the antiviral effect of LPS. These results indicate that IFN- independent pathways which activated by LPS are able to downregulate hepadnaviral replication in hepatocytes.

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.

Persistence of hepatitis C virus in patients successfully treated for chronic hepatitis C

It is unclear whether the current antiviral treatment for chronic hepatitis C virus (HCV) infection results in complete elimination of the virus, or whether small quantities of virus persist. Our study group comprised 17 patients with chronic HCV who had sustained virological response (SVR) after interferon/ribavirin treatment. Serum and peripheral blood mononudear cells were collected 2 to 3 times at 3- to 6-month intervals starting 40 to 109 months (mean, 64.2 +/- 18.5 months) after the end of therapy. In addition, lymphocyte and macrophage cultures were established at each point. In 11 patients, frozen liver tissue samples were available from follow-up biopsies performed 41 to 98 months (mean, 63.6 +/- 16.7 months) after therapy. Presence of HCV RNA was determined by sensitive reverse-transcriptase polymerase chain reaction, and concentration of positive and negative strands was determined by a novel quantitative real-time reverse transcriptase polymerase chain reaction. Only 2 of 17 patients remained consistently HCV RNA negative in all analyzed compartments. HCV RNA was detected in macrophages from 11 patients (65%) and in lymphocytes from 7 patients (41%). Viral sequences were also detected in 3 of 11 livers and in sera from 4 patients. Viral replicative forms were found in lymphocytes from 2 and in macrophages from 4 patients. In conclusion, our results suggest that in patients with SVR after therapy, small quantities of HCV RNA may persist in liver or macrophages and lymphocytes for up to 9 years. This continuous viral presence could result in persistence of humoral and cellular immunity for many years after therapy and could present a potential risk for infection reactivation.

Hepatitis C virus persistence after spontaneous or treatment-induced resolution of hepatitis C

It is presumed that resolution of hepatitis C, as evidenced by normalization of liver function tests and disappearance of hepatitis C virus (HCV) RNA from serum, as determined by conventional laboratory assays, reflects virus eradication. In this study, we examined the expression of the HCV genome in the sera, peripheral blood mononuclear cells (PBMC), and, on some occasions, monocyte-derived dendritic cells (DC) long after resolution of hepatitis C by using a highly sensitive reverse transcription (RT)-PCR-nucleic acid hybridization (RT-PCR-NAH) assay. The samples obtained from 16 randomly selected patients (5 with spontaneous and 11 with treatment-induced resolution), monitored for up to 5 years, were studied by qualitative and semiquantitative RT-PCR-NAH and by real-time RT-PCR to detect the HCV RNA positive strand. The replicative HCV RNA negative strand was examined in PBMC after culture with a T-cell proliferation stimulating mitogen. The findings show that HCV RNA was carried in the convalescent-phase sera and/or PBMC in all 16 individuals investigated. Also, DC from six of seven patients were reactive for the HCV genome. Importantly, traces of the HCV RNA negative strand, suggesting progressing virus replication, were detected in the majority of mitogen-stimulated PBMC, including four samples collected 5 years after recovery. Sequencing of the HCV 5' untranslated region fragment revealed genotype 1b in four of nine individuals examined and genotypes 1a and 2a in three and two patients, respectively. These results imply that HCV RNA can persist at very low levels in the serum and peripheral lymphoid cells and that an intermediate replicative form of the HCV genome can persist in PBMC for many years after apparently complete spontaneous or antiviral therapy-induced resolution of chronic hepatitis C.

Deficiencies in the acute-phase cell-mediated immune response to viral antigens are associated with development of chronic woodchuck hepatitis virus infection following neonatal inoculation

In vitro proliferation of peripheral blood mononuclear cells was used to measure virus-specific cell-mediated immunity (vCMI) following neonatal woodchuck hepatitis virus (WHV) infection. Fifteen neonates were inoculated with the W8 strain of WHV. In 11, infection was resolved, and 4 became chronic carriers. Nineteen neonates were inoculated with the W7 strain and all became chronic carriers. Seven age-matched uninfected woodchucks served as controls. Virologic and vCMI profiles among the W8 and W7 infections were compared and related to the outcome of infection. Resolving woodchucks had robust, acute-phase vCMI to WHV antigens (core, surface, and x) and to several nonoverlapping core peptides. The acute-phase vCMI was associated temporally with the clearance of viral DNA and of surface antigen from serum at 14 to 22 weeks postinfection. In contrast, in approximately half of the W8 and W7 infections that progressed to chronicity, no significant acute-phase vCMI was detected. In the remaining carriers, acute-phase vCMI was observed, but it was less frequent and incomplete compared to that of resolved woodchucks. Serum viral load developed less rapidly in those carriers that had evidence of acute-phase vCMI, but it was still increased compared to that of resolving woodchucks. Thus, vigorous and multispecific acute-phase vCMI was associated with resolution of neonatal WHV infection. Absent or incomplete acute-phase vCMI was associated with the progression to chronic infection. By analogy, these results suggest that the onset of chronic hepatitis B virus (HBV) infection in humans may be associated with deficiencies in the primary T-cell response to acute HBV infection.

Thymidine utilization abnormality in proliferating lymphocytes and hepatocytes of the woodchuck

Effective incorporation of tritiated thymidine ([(3)H]TdR) into proliferating lymphocytes is important because [(3)H]TdR is a standard label to study proliferate T-cell responses. We analyzed the thymidine utilization of woodchuck peripheral blood lymphocytes (PBL) since the [(3)H]TdR incorporation assay was not applicable to measure proliferative immune responses in the woodchuck, a current major virus/host model for human hepatitis B virus infection. Incorporation of [(3)H]TdR into DNA as well as the activity of the salvage pathway enzyme thymidine kinase (TK) of proliferating woodchuck PBL was low compared to human lymphocytes. Furthermore, [(3)H]TdR incorporation of proliferating woodchuck PBL remained residual regardless of the use of methotrexate, an inhibitor of the competitive deoxythymidine monophosphate de novo synthesis pathway. Using a human probe, specific for the proliferation-associated TK1, we proved the genomic presence and transcription of TK1 sequences in various species. TK1 sequences were detected in the genome of human, mouse, woodchuck, and chicken specimens. In contrast to proliferating human PBL and 3T3 mouse fibroblasts, no TK1 transcript was found in proliferating woodchuck PBL and hepatic cells. Transfection experiments with vectors containing the murine or human TK1 and selection assays demonstrated the ability of woodchuck cells to transcribe TK1 and to express functional TK1 proteins. Our study characterizes the unique failure of sufficient [(3)H]TdR incorporation into proliferating woodchuck cells and demonstrates tritiated adenine and serine as alternative labels to monitor PBL proliferation in the woodchuck.

Levels of HBV-DNA and HBsAg after acute liver allograft rejection treatment by corticoids and OKT3

The aim of this work was to analyze whether the treatment of acute rejection of orthotopic liver transplants (OLT), either with corticoids or OKT3, has any effect on the levels of hepatitis B virus (HBV)-DNA and HBsAg in individuals which were originally affected by cirrhosis or fulminant hepatic failure as a result of B virus. We have found that HBV-DNA is present in macrophages, B cells and both CD4+ and CD8+ T cells after OLT in all cases studied. Interestingly, the levels of HBV-DNA and HBsAg in the serum analyzed were increased extremely rapidly in the patients treated with OKT3 in an acute rejection episode. However, the serum levels of HBV-DNA and HBsAg found were lower when the patients were treated with steroids, and were not found in non-treated patients. As the serum levels of HBV-DNA increase, the process of liver reinfection could be accelerated; therefore, these results may help to understand how OKT3 and corticoids immunosuppressive therapy may accelerate the reinfection of OLT by HBV. In conclusion, our results suggest that special care must be taken in the use of OKT3 in the treatment of acute liver rejection episodes in chronic or fulminant HBV transplanted patients.

Induction of hepatitis B virus gene expression at low temperature

There is a limited understanding of the cellular regulation of HBV gene expression in differentiated hepatocytes. We previously demonstrated that HBV replication inversely correlates with cell proliferation and DNA synthesis. In this report, temperature-induced modulation of cell growth was used as a novel approach to study HBV gene expression in the absence of indirect effects from drugs or serum deprivation. We observed markedly elevated levels of hepatic HBV mRNA expression from integrated and episomal HBV DNA at 32 degrees C. Additionally, hepatoblastoma cells cultured at 32 degrees C expressed increased levels of albumin mRNA and decreased levels of c-myc mRNA, which demonstrates that liver-derived cells cultured at low temperature exhibit characteristics of functional and differentiated hepatocytes. In transiently transfected HepG2 cells cultured at 32 degrees C, the HBV enhancer 1 activated the X promoter and core/pregenomic promoter by 7.3- and 28-fold, respectively. In the absence of enhancer 1, core/pregenomic promoter activity was 2.4-fold higher than the X promoter in HepG2 cells at 32 degrees C. In contrast, enhancer 1 exclusively activated the X promoter in transfected non-liver cells at 32 degrees C. Therefore, the core/pregenomic promoter exhibits strict liver-specificity at low temperature. This work supports the hypothesis that HBV replication and gene expression are optimal in non-activated hepatocytes, and provides a novel system for delineating molecular aspects of the HBV replication process.

Persistence of infectious hepadnavirus in the offspring of woodchuck mothers recovered from viral hepatitis

Mother-to-child transmission is an important route for hepatitis B virus (HBV) dissemination. It has been established that HBV traces persist for years after complete clinical recovery from hepatitis B. Similarly, resolution of hepatitis caused by HBV-related woodchuck hepatitis virus (WHV) is followed by occult lifelong carriage of pathogenic virus. In this study, we documented that WHV persisting after termination of acute hepatitis is transmittable to newborns as an asymptomatic long-term infection. All 11 offspring from 4 dams studied carried transcriptionally active WHV genomes for 3.5 years after birth without immunovirological markers of infection. WHV genomes and mRNA were detected both in the liver and lymphoid tissue in the majority of offspring; WHV covalently closed circular DNA was detected in some samples. In 4 offspring, however, the virus was restricted to the lymphatic system. In the circulation, WHV DNA-reactive particles were DNase resistant and of comparable size and density to complete virions. Importantly, the virus in offspring with or without hepatic WHV DNA expression was infectious to WHV-naive woodchucks. Finally, offspring challenged with WHV were not protected against reinfection. These findings show that mothers with occult hepadnaviral carriage transmit pathogenic virus to their offspring, inducing a persistent infection invariably within the lymphatic system but not always in the liver.

Occult lifelong persistence of infectious hepadnavirus and residual liver inflammation in woodchucks convalescent from acute viral hepatitis

Traces of hepatitis B virus (HBV) genome can persist for years following recovery from hepatitis B. To determine overall duration, molecular characteristics, and pathological implications of this serologically undetectable form of hepadnaviral carriage, we have analyzed the expression of transcriptionally active virus genomes, their infectivity, and examined liver alterations during the natural lifespan of woodchucks convalescent from acute infection with HBV- related woodchuck hepatitis virus (WHV). In this study, we document lifelong persistence of scanty amounts of replicating virus both in the liver and lymphatic system after spontaneous resolution of an episode of experimental hepadnaviral hepatitis. Antibodies to virus nucleocapsid (core) were found to be the most reliable immunovirological marker coexisting with occult infection. In the majority of convalescent woodchucks, serial liver biopsies showed protracted minimal to mild necroinflammation with periods of normal morphology; however, hepatocellular carcinoma (HCC) ultimately developed in 2 of 9 animals studied. Inocula derived from lymphoid cells of convalescent animals induced classical acute hepatitis in virus-naive woodchucks that progressed to chronic hepatitis and HCC in 1 of the animals, demonstrating infectivity and pathogenic competence of the carried virus. Our results reveal that low levels of infectious WHV and residual hepatic inflammation usually continue for life after resolution of hepatitis and that this recovery does not avert HCC development. They also demonstrate that, in addition to the liver, the lymphatic system is the site of the occult lifelong maintenance of replicating hepadnavirus.

HBV viral load within subpopulations of peripheral blood mononuclear cells in HBV infection using limiting dilution PCR

Extrahepatic viral load in peripheral blood mononuclear cells (PBMCs) of patients with hepatitis B virus (HBV) is still under debate. In this study, HBV infection rates and viral titers were examined within all PBMC subpopulations using limiting dilution-PCR (LD-PCR). PBMCs of patients with acute or chronic hepatitis B were separated by magnetic beads in monocytes, B-cells, CD4+ T-cells, CD8+ T-cells, and NK cells. Using two-round nested PCR, HBV-DNA sequences were detected in all patients examined within each PBMC subpopulation. The frequencies of HBV-positive cells and viral loads were calculated by Poisson analysis of HBV PCR results from serial dilutions of cells and cell lysates. Highest infection rates were found in monocytes and B-cells followed by CD8 + T-cells, NK cells, and CD4+ T-cells. Concerning all subsets, frequencies of HBV-positive cells were 50- to 500-fold higher in chronic than in acute hepatitis B. Viral loads were mostly estimated at about one HBV genome per HBV-positive cell. Moreover, slightly elevated HBV titers were seen in B-cells, CD4+ T-cells, and NK cells in both acute and chronic hepatitis B. It was demonstrated that beside a generally more latent HBV infection in PBMCs, elevated HBV titers point to replication or selective viral uptake within particular PBMC subsets. Therefore, the data suggest that HBV-infected PBMCs may participate in persistence of HBV.

Evidence for selection of hepatitis B mutants after liver transplantation through peripheral blood mononuclear cell infection

BACKGROUND/AIMS

Despite anti-HBs immunoglobulin therapy, hepatitis B virus (HBV) infection recurs in a high proportion of patients transplanted for HBsAg positive and serum HBV DNA negative chronic liver disease. The contribution of HBV genetic variability to disease recurrence has not been yet thoroughly addressed. We have therefore undertaken a detailed comparison of preS/S and preC/C sequences in two selected patients with recurrence of HBsAg and HBV DNA after transplantation.

METHODS

PreS/S and preC/C regions were amplified by PCR from the serum, peripheral blood mononuclear cell (PBMC) and liver tissues of two patients transplanted for end stage HBV-related cirrhosis. Samples were taken both pre- and post-transplantation. HBV-sequences from four to nine clones were determined and compared.

RESULTS

A mixing of different HBV DNA molecules was observed within and between serum, liver and PBMC samples. Sequences from both patients showed mutations in the preC region which abolished HBeAg secretion, and in the preS2 initiation codon which prevented preS2 envelope protein production. In addition, for both patients, deletions in the preS2 domain (3 and 21 base pairs) led to the expression of modified preS1 envelope protein. For one patient, the predominant HBs protein sequence found in the PBMC before transplantation showed four specific mutations. One of these mutations was in the "a" determinant (codon 144, asparagine to glycine change) of the major envelope protein. These mutations were not detected, as predominant mutations, in the liver and serum pre-orthotopic liver transplant samples. In contrast, after liver transplantation, this was the major form identified in serum, liver and PBMC.

CONCLUSIONS

Our results have shown the selection of different HBV DNA molecules in liver and mononuclear cells. In addition, they provide direct evidence for the role of PBMC in the infection of liver grafts and support the hypothesis that infection of PBMC might lead to selection of HBV variants which would escape immune therapy. Finally, we provide in vivo evidence for reinfection of the liver by HBV particles lacking preS2 envelope protein expression.

Characterization of T-cell response to woodchuck hepatitis virus core protein and protection of woodchucks from infection by immunization with peptides containing a T-cell epitope

Specific activation of T cells appears to be a prerequisite for viral clearance during hepatitis B virus (HBV) infection. The T-cell response to HBV core protein is essential in determining an acute or chronic outcome of HBV infection, but how this immune response contributes to the course of infection remains unclear. This is due to results obtained from humans, which are restricted to phenomenological observations occurring during the clinical onset after HBV infection. Thus, a useful animal model is needed. Characterization of the T-cell response to the core protein (WHcAg) of woodchuck hepatitis virus (WHV) in woodchucks contributes to the understanding of these mechanisms. Therefore, we investigated the response of woodchuck peripheral blood mononuclear cells (PBMCs) to WHcAg and WHcAg-derived peptides, using our 5-bromo-2'-deoxyuridine assay. We demonstrated WHcAg-specific proliferation of PBMCs and nylon wool-nonadherent cells from acutely WHV-infected woodchucks. Using a cross-reacting anti-human T-cell (CD3) antiserum, we identified nonadherent cells as woodchuck T cells. T-cell epitope mapping with overlapping peptides, covering the entire WHcAg, revealed T-cell responses of acutely WHV-infected woodchucks to peptide1-20, peptide100-119, and peptide112-131. Detailed epitope analysis in the WHcAg region from amino acids 97 to 140 showed that T cells especially recognized peptide97-110. Establishment of polyclonal T-cell lines with WHcAg or peptide97-110 revealed reciprocal stimulation by peptide97-110 or WHcAg, respectively. We vaccinated woodchucks with peptide97-110 or WHcAg to prove the importance of this immunodominant T-cell epitope. All woodchucks immunized with peptide97-110 or WHcAg were protected. Our results show that the cellular immune response to WHcAg or to one T-cell epitope protects woodchucks from WHV infection.

The HNF1/HNF4-dependent We2 element of woodchuck hepatitis virus controls viral replication and can activate the N-myc2 promoter

Transcriptional activation of myc family proto-oncogenes through the insertion of viral sequences is the predominant mechanism by which woodchuck hepatitis virus (WHV) induces liver tumors in chronically infected animals. The main target is N-myc2, a functional retroposon of the N-myc gene, but c-myc and N-myc are also marginally involved. Here we identify a major, liver-specific regulatory element in the WHV genome (We2) which efficiently activates the N-myc2 promoter in cultured hepatoma cells. In the context of the episomal viral genome, We2 governs the production of pregenomic RNA and thus plays a central role in the control of viral replication. We2 activity is primarily controlled by the liver-enriched HNF1 and HNF4 transcription factors, although NF1 and Oct proteins were also shown to bind in a central region. The expression of HNF1 and HNF4 appears to be maintained in woodchuck tumors. Thus, We2 is a prime candidate for controlling myc gene cis activation during WHV-induced hepatocarcinogenesis.

Hepatitis B and C viruses and primary liver cancer

The data presented indicate that viral agents (namely, HBV and HCV) are major environmental aetiological factors for human primary liver cancer. It is important to elucidate the molecular mechanisms further because HCC is one of the few examples of virus-related human cancers. In addition, the available evidence points to the possibility of at least partial prevention of the tumour by large-scale vaccination.

Polymerase chain reaction to monitor repair of the HBV genome, the first step in viral replication

A method based on the polymerase chain reaction (PCR) for evidencing repair of the hepatitis B virus (HBV) genome is described. Hepadnaviruses have a partially double-stranded relaxed circular genome (RC-DNA) which is converted into a covalently closed circular DNA (CCC-DNA) after entry of the virus into a target cell. Our aim was to set up a technique enabling us to determine whether possible in vitro replication of the virus in non-hepatic cells is initiated by formation of CCC-DNA. The relevant part of the strategy used for this PCR consisted of priming the HBV-DNA template with the same forward primer and with a reverse primer located either downstream or upstream from the minus strand gap. The CCC-DNA form was found, as expected, in cells in which the virus was known to be actively replicating; although most sera contained only the RC-DNA form, it was also possible to evidence the CCC form. Such PCR amplification led to detection of 50-500 copies of the viral DNA. The method described should be useful in studying the biological fate of HBV in non-hepatic cells (considered as non-permissive for virus replication), and in exploring the clinical significance of the presence of CCC-DNA in sera.

Persistence of extrahepatic hepatitis B virus DNA in the absence of detectable hepatic replication in patients with baboon liver transplants

The presence of hepatitis B virus (HBV) DNA in extrahepatic tissues has been well documented. Whether HBV DNA can persist in extrahepatic tissues for long periods of time in the absence of replication in the liver has not been determined previously. Recently, two patients with end-stage liver disease secondary to chronic active HBV were treated with baboon liver xenotransplants as these animals are felt to be resistant to HBV infection. Multiple tissues from these two patients were examined for HBV DNA using polymerase chain reaction (PCR). HBV DNA was not detectable in four of five samples of the liver xenografts. A positive signal was observed in a single assay for one sample, but this sample was not positive in subsequent assays. HBV DNA was detected in peripheral blood lymphocytes, spleen, kidney, bone marrow, pancreas, lymph node, heart and small intestine. The level of HBV DNA in these tissues was too low for the detection of HBV DNA replicative intermediates by Southern hybridization; thus, it could not be determined whether the HBV DNA in these tissues represented actively replicating HBV in extrahepatic sites, integrated HBV sequences, HBV in infiltrating lymphocytes, or deposition of HBV immune complexes originating from the plasma. However, it is clear from this study that HBV DNA persisted in multiple tissues for 70 days after replication in the liver had ceased or at least was below the level of detection by PCR.

Lymphotropism of hepatitis B and C viruses: an update and a newcomer

The mechanisms of viral persistence are complex and include infection of the lymphoid cells. In the case of hepatitis B virus, early observations have suggested that HBV may infect peripheral blood mononuclear cells (PBMC). In animal models studies in chronic hepatitis B patients have further confirmed that viral DNA replicative intermediates, as well as viral transcripts and proteins, can be detected in PBMC under certain conditions. The consequences of this lymphotropism are not fully understood, but it seems likely that PBMC represent an extrahepatic reservoir of virus. The ability of hepatitis C virus to infect PBMC has been demonstrated in vivo and in vitro. The link between HCV lymphotropism and both the natural history of the viral infection and the immunological disorders frequently observed in HCV infections still needs to be established. In both cases, the infection of PBMC by HBV or HCV may represent the source of infection of the liver graft in patients transplanted for end-stage liver disease associated with HBV or HCV.

Infection of circulating and liver infiltrating T cells by hepatitis C virus of different subtypes

Hepatitis C virus (HCV) infection display a very high rate of progression to chronicity and, like many other viruses causing persistent infections, it displays a tropism for the cells of the immune system. Peripheral blood mononuclear cells (PBMCs) from 21 HCV chronic carriers and long-term T cell clones derived from circulating or liver infiltrating T lymphocytes were tested by cDNA "nested" PCR for positive and negative strand HCV-RNA. The presence of HCV genomes in PBMCs is a frequent, although not constant, finding and can be accompanied by active viral replication, as suggested by the coexistence of negative strand HCV-RNA. Infected T cells are more represented in livers than in periphery, as indicated by comparing HCV-RNA detection in T cell clones isolated from both the compartments. Sequencing of viral genomes present in PBMCs and liver infiltrating lymphocytes showed that all the three major HCV genotypes present in our population of chronic carriers can infect lymphoid cells. Although each clonal population of T cells is infected by a single strain of HCV, in the same patient lymphoid cells can harbor different viral populations, different from those circulating at that moment in the serum.

Detection of hepatitis B virus DNA and determination of surface antigen expression in peripheral blood mononuclear cells from patients with AIDS

The polymerase chain reaction (PCR) was used to analyze the presence of hepatitis B virus (HBV) DNA in serum and peripheral blood mononuclear cells (PBMCs) from 20 patients with AIDS with and without conventional HBV serological markers. DNA sequences of HBV were detected in PBMCs from 13 patients, nine of whom were positive for anti-HBc only and four of whom were also positive for anti-HBs. When PBMCs from patients were activated in culture with phytohemagglutinin, the presence of HBsAg could be detected in the culture supernatants from four of 13 patients with HBV DNA in their PBMCs; for two of the four, HBV DNA could also be detected in the culture supernatant after DNA amplification. It was observed that HBV DNA sequences found in PBMCs can be reactivated by mitogen stimulation in some HIV-1 infected patients.

Hepatitis B virus persistence after recovery from acute viral hepatitis

Contrary to current opinion, the disappearance of hepatitis B surface antigen (HBsAg) from the serum, the development of anti-HBs antibodies, and normalization of liver function may not reflect complete virological recovery from acute hepatitis B virus (HBV) infection. By using the polymerase chain reaction (PCR), in the current study we demonstrate long-term persistence of HBV DNA in the serum and peripheral blood mononuclear cells (PBMC) of four patients for up to 70 mo after complete clinical, biochemical, and serological recovery from acute viral hepatitis. Serum HBV DNA reactivity co-sedimented with HBsAg in sucrose gradients, and it displayed the size and density characteristics of naked core particles and intact HBV virions, presumably contained within circulating immune complexes in these anti-HBs antibody-positive sera. HBV DNA was also present in PBMC in late convalescent samples from all four patients, and HBV RNA was detected in late convalescent phase PBMC in two of these patients. These results suggest that HBV DNA, and possibly HBV virions, can be present in the serum, and that the viral genome can persist in a transcriptionally active form in PBMC for > 5 yr after complete clinical and serological recovery from acute viral hepatitis.

Detection of replicative intermediates of viral RNA in peripheral blood mononuclear cells from chronic hepatitis C virus carriers

Clinical and experimental evidence suggests the possible existence of one or more extrahepatic sites of HCV infection. In order to demonstrate the "in vivo" infection of lymphoid cells by HCV, we applied a nested PCR to total cytoplasmic RNA extracted from fresh or cultured peripheral blood mononuclear cells (PBMCs) of HCV chronically infected patients, using primers derived from the highly conserved 5' untranslated region of the HCV genome. The presence of virions in PBMCs occurs frequently, if not always, and is often accompanied by active viral replication. Moreover, the appearance of replicative intermediates after stimulation of cellular growth with mitogens suggests that latent genomes could undergo replication upon cellular activation and/or proliferation.

Phytohemagglutinin and concanavalin A activate hepatitis B virus in peripheral blood mononuclear cells of patients with chronic hepatitis B virus infection

Peripheral blood mononuclear cells (PBMC) from 25 patients with chronic hepatitis B were tested for the presence of free monomeric hepatitis B virus (HBV) DNA migrating as a single 3.2 Kb band by Southern blot analysis. The PBMC were cultured for 7 days in the presence of phytohemagglutinin (PHA) or concanavalin A (ConA) both of which yielded a proliferative response. By contrast, both bacterial lipopolysaccharide (LPS) and interleukin 2 (IL2) failed to do so. Dot blot assays were used to monitor HBV DNA level increase within PBMC. Following mitogen exposure HBV DNA levels increased above pre-stimulation levels in 19/25 PHA cultures, 6/15 ConA cultures, 1/15 LPS cultures, and 1/15 IL2 cultures. In 15 patients, Southern blot analysis was carried out before and after PHA exposure. In 13/15 cases, a single 3.2 Kb band was observed in unstimulated cultures as well as in PHA cultures even though PHA induced a HBV DNA increase. One case exhibited bands migrating faster than the 3.2 Kb signal, compatible with replicating intermediates and one case provided evidence of viral concatemers within PBMC after PHA stimulation. No HBV DNA was detected in the culture supernatants. The increase of HBV DNA level in PBMC induced by mitogen was strongly associated with an increase in HBV DNA expression (HBV RNA and HBs antigen). These studies indicate that HBV DNA present in human PBMC does represent a potential reservoir for infection with endogenous reactivation following PBMC activation.

Infection of peripheral mononuclear blood cells by hepatitis C virus

We investigated the infection of peripheral blood mononuclear cells (PBMNC) by hepatitis C virus (HCV) in 5 patients with HCV-related chronic hepatitis. The presence of HCV-RNA-positive and -negative strands was tested with the polymerase chain reaction (PCR) method. In all subjects, HCV-RNA was shown in PBMNC. In 3 cases, HCV-RNA was shown in the T- and B-cell populations, with viral RNA also present in the monocyte-macrophage fraction of two of these. HCV-RNA-negative stranded molecules, indicative of the viral multiplication, were significantly increased in cells maintained in cultures with PHA/PMA stimulation. The results indicate that HCV infect blood mononuclear cells, thus suggesting that this cellular tropism may play a role in HCV infection.

Search for hepatitis B virus cell receptors reveals binding sites for interleukin 6 on the virus envelope protein

The major target organ for hepatitis B virus (HBV) is the liver. However, cells other than hepatocytes, including peripheral blood lymphocytes and monocytes, may become infected with HBV. The cell receptor binding site was assigned to the preS(21-47) segment of the HBV envelope protein. HBV receptors were detected on human liver and hepatoma cells, on B lymphocytes, and, as shown here, on monocytes, and T cell lines, activated by Escherichia coli lipopolysaccharide and concanavalin A, respectively. The cell receptors for HBV have not been characterized until now. The detection of HBV receptors and their "activation antigen" characteristic on distinct cells suggested paths for identification of the receptors with already defined cell surface proteins. This search revealed that interleukin 6 contains recognition sites for the preS(21-47) sequence and mediates HBV-cell interactions. Thus, HBV belongs to a group of viruses utilizing cytokines or cytokine receptors for replication and interference with the host immune system.

Hepatitis B virus. New and evolving issues

Recent developments in molecular biology have advanced our understanding of the pathogenesis of HBV-induced disease. New data derived from the molecular analysis of clinical material have begun to bridge the gap between bench research and the clinical arena. In this review, we consider topics that have relevance to clinical management and that have not been summarized in the recent literature. The recent advances that have been made in the areas of HBV variants, in vitro cell culture systems, and extrahepatic infection are discussed in greater detail.

Production of 22 nm HBsAG particles by human lymphocytes infected with a recombinant vaccinia virus containing the coding sequence for hepatitis B virus surface antigen

To examine the possible role of lymphocytes in the course of hepatitis B virus infection, we studied peripheral blood lymphocytes and Epstein-Barr virus transformed B-cells for their capability to produce hepatitis B virus gene products. Infection of these cells with a recombinant vaccinia virus containing the hepatitis B virus surface antigen resulted in the production and secretion of hepatitis B virus surface antigen shortly after infection reaching a peak after three days. When the supernatants of the cells were analyzed on density gradients, a peak of reactivity for hepatitis B virus surface antigen was reached at 1.21 g/cm3. Electron microscopy revealed the presence of spherical and filamentous HBsAg particles. These findings show that human lymphocytes are capable of producing hepatitis B virus surface antigen.

Persistent hepatitis B virus following interferon alfa therapy and liver transplantation

A 44-year-old man with chronic hepatitis B virus infection and cirrhosis was treated with recombinant human interferon alfa for 67 days immediately before orthotopic liver transplantation and immunoprophylaxis with hyperimmune globulin to hepatitis B virus in the peritransplant period. Dot blots for hepatitis B virus DNA demonstrated marked reduction in viremia after 41 days of interferon alfa treatment. Southern analysis for hepatitis B virus in liver showed a pronounced decrement in actively replicating forms in the explant, although hepatic infection was still detectable. After liver transplantation, tests for serum hepatitis B virus DNA and hepatitis B surface antigen remained negative. The patient died 32 days after transplantation of causes unrelated to hepatitis B virus. DNA isolated from liver and other visceral organs at autopsy showed infection of the engrafted liver and the persistence of monomeric relaxed circular forms of hepatitis B virus DNA in pancreas, kidney, and spleen. Thus, graft reinfection occurred despite aggressive antiviral therapy and immunoprophylaxis combined with liver transplantation. Existing viral serological markers appear insufficiently sensitive to assess residual infectivity.

Influence of hepatitis delta virus replication in the presence of hepatitis B virus DNA in peripheral blood mononuclear cells

The presence of hepatitis B virus DNA was studied in peripheral blood mononuclear cell samples from 259 HBsAg carriers (229 anti-hepatitis delta negative, 30 anti-hepatitis delta positive), 16 anti-HBc-positive HBsAg-negative patients and 30 patients without hepatitis B virus markers. Hepatitis B virus DNA sequences were detected in peripheral blood mononuclear cell from 115 (44.4%) of the chronic HBsAg carriers and from two (12%) of the anti-HBc-positive, HBsAg-negative patients. In anti-hepatitis delta-negative patients, viral DNA was positive in peripheral blood mononuclear cell from 74 (46%) and from 24 (35.5%) with and without serum HBV-DNA, respectively. With respect to anti-hepatitis delta-positive patients, viral DNA was found in peripheral blood mononuclear cell in 8 of 13 (61.5%) of the patients with circulating hepatitis delta virus RNA and in 9 of 17 (53%) of the hepatitis delta virus RNA-negative subjects. Regarding hepatitis B virus DNA in serum and peripheral blood mononuclear cell, 71% (5 of 7) of the patients with serum hepatitis B virus DNA had this marker in peripheral blood mononuclear cell, whereas 52% (12 of 23) of the patients without serum hepatitis B virus DNA had hepatitis B virus DNA in peripheral blood mononuclear cell. A Southern blot analysis was also carried out on peripheral blood mononuclear cell samples from 30 patients. Hepatitis B virus DNA was detected in 16 patients as free forms, in 12 patients as dimers and free forms and as free circular together with free linear forms in the remaining two patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Expression pattern of the hepatitis B virus genome in transfected mouse fibroblasts

Permanent mouse fibroblast LTK- cells were transfected with dimeric hepatitis B virus (HBV) DNA linked to the simian virus 40 (SV40) early promoter/enhancer. Many clones stably expressed high levels of polyadenylated RNAs encoding hepatitis B surface (HBs) proteins (2.1 kb), HBe protein (3.6 kb), and HBx protein (0.6 kb). Although a chimeric RNA (4.0 kb) probably starting from the SV40 promoter was also synthesized, transcription of viral RNAs was predominantly directed by HBV promoters and its terminator. In contrast to HBV-transfected liver cells, the fibroblasts expressed only pregenomic 3.6-kb transcripts starting 5' to, but not within, the precore sequence. Thus, no normal core protein could be synthesized, but the cells expressed and secreted HBe protein of heterogeneous size. Small and middle HBs proteins were strongly expressed, while large HBs protein was almost absent. HBx mRNA expression was more efficient in mouse fibroblasts than in human hepatoma cells and 18-kDa HBx protein was exclusively detected in purified nuclei. Expression of HBe, small and middle HBs, and HBx proteins apparently does not require hepatic factors. Underexpression of HBc mRNA and large HBs mRNA suggests that activity of their promoters depends on cell-type-specific transcription factors.

Replication of hepatitis B virus in transfected nonhepatic cells

Permanent murine fibroblasts (LTK-) were transfected with a dimer of hepatitis B virus (HBV) DNA and a neomycin resistance gene which were both linked to the simian virus 40 (SV40) early promoter/enhancer. One of the stably transfected clones, LTK4/36, which secreted HBsAg, HBeAg, and HBV DNA was further analyzed. It contained eight to nine copies of integrated HBV DNA per haploid genome and low amounts of episomal HBV DNA. The secreted viral DNA was covalently linked to protein and was associated with particles which had the characteristic density of natural virions from serum of human viremic carriers. The particles contained an endogenous DNA polymerase, small and middle surface proteins, but in contrast to natural virions very little core protein and large surface protein. Instead of core protein, they contained incompletely processed HBe protein which is colinear to core protein. The fibroblast-derived virions were less stable than virions from human carriers or from transfected hepatoma cells. After several days of storage, their DNA was only partially protected against DNase. Obviously, nonhepatic cells can express HBV-like particles, even if liver-dependent gene products like large surface protein and core protein are missing.

Natural history of experimental woodchuck hepatitis virus infection: molecular virologic features of the pancreas, kidney, ovary, and testis

The kinetic patterns of woodchuck hepatitis virus (WHV) infection were monitored in the pancreas, kidneys, ovaries, and testes. Groups of woodchucks experimentally infected with a standardized inoculum of WHV were sacrificed at different times over a 65-week period beginning in the preacute phase of viral infection and continuing to the period of serologic recovery or the establishment of chronic infections and subsequent hepatocellular carcinoma (B. E. Korba, P. J. Cote, F. V. Wells, B. Baldwin, H. Popper, R. H. Purcell, B. C. Tennant, and J. L. Gerin, J. Virol. 63:1360-1370, 1989). Tissues from an additional group of long-term (2 to 3 years) chronic WHV carriers which had been infected with the same WHV inocula were also examined. Viral DNA replication intermediates were found in all four tissues during the acute phase of WHV infection. However, WHV DNA replication intermediates were observed only in the kidneys of a small proportion of the chronically infected animals. Following the acute phase of infection, WHV DNA was present only in the pancreas, kidneys, and ovaries of the chronically infected woodchucks. A progressive evolution of different WHV genomic forms related to the replicative state of WHV was observed in these tissues. Histologic evaluation of these four tissues revealed only minimal, localized lesions which were not correlated with the state of WHV activity. The observations compiled in this study further extend the tissue tropism of WHV.

Experimental WHV infection of woodchucks: an animal model of hepadnavirus-induced liver cancer

Woodchuck hepatitis virus (WHV), a member of the Hepadnaviridae, is closely related to HBV in its virus structure, genetic organization and mechanism of replication. Natural infection of woodchucks is associated with chronic liver disease and primary hepatocellular carcinoma (HCC). A concerted effort to develop the woodchuck as an experimental animal model of hepadnavirus-induced disease was initiated in 1980. The experimental studies have established the following: (1) Chronic WHV carriage as an outcome of infection is a function of age of exposure, virus dose and, possibly, virus strain. As in humans, animals infected as newborns develop chronic antigenemia at high rates compared to young adults. (2) WHV causes primary hepatocellular carcinoma (HCC) in woodchucks. Hundred percent of experimentally-induced chronic WHsAg carriers developed HCC within three years; no HCC has occurred in concurrent uninfected control animals born and held in the same laboratory environment. The predictable course of experimental WHV infection leading to liver disease in woodchucks makes this an ideal model in which to study the natural history of hepadnavirus and to develop effective prophylactic and therapeutic strategies.