101
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Guha C, Mohan S, Roy-Chowdhury N, Roy-Chowdhury J. Cell culture and animal models of viral hepatitis. Part I: hepatitis B. Lab Anim (NY) 2004; 33:37-46. [PMID: 15224117 DOI: 10.1038/laban0704-37] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2003] [Accepted: 02/25/2004] [Indexed: 12/19/2022]
Abstract
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.
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Affiliation(s)
- Chandan Guha
- Albert Einstein College of Medicine, 1300 Morris Park Ave., Bronx, NY, USA
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102
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Nakamoto Y, Suda T, Momoi T, Kaneko S. Different procarcinogenic potentials of lymphocyte subsets in a transgenic mouse model of chronic hepatitis B. Cancer Res 2004; 64:3326-33. [PMID: 15126377 DOI: 10.1158/0008-5472.can-03-3817] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The immune response to hepatitis viruses is believed to be involved in the development of chronic hepatitis; however, its pathogenetic potential has not been clearly defined. The current study, using a transgenic mouse model of chronic hepatitis B, was designed to determine the relative contributions of the immune cell subsets to the progression of liver disease that induces hepatocellular carcinogenesis. Hepatitis B virus transgenic mice were adoptively transferred with CD4+ and CD8+ T cell-enriched or -depleted and B cell-depleted splenocytes obtained from hepatitis B surface antigen-primed, syngeneic nontransgenic donors. The resultant liver disease, hepatocyte apoptosis, regeneration, and tumor development were assessed and compared with the manifestations in mice that had received unfractionated spleen cells. Transfer of CD8(+)-enriched splenocytes caused prolonged disease kinetics, and a marked increase in the extent of hepatocyte apoptosis and regeneration. In 12 of 14 mice the transfer resulted in multiple hepatocellular carcinomas (HCCs) comparable with the manifestations seen in the mice transferred with total splenocytes. In contrast, mice that had received CD4(+)-enriched cells demonstrated lower levels of liver disease and developed fewer incidences of HCC (4 of 17). The experiment also revealed that all of the groups of mice complicated with HCC developed comparable mean numbers and sizes of tumors. B-cell depletion had no effect on disease kinetics in this model. Taken together, these results demonstrate that the pathogenetic events induced by CD8+ T-cell subset are primarily responsible for the induction of chronic liver disease that increases tumor incidence, suggesting their potential in triggering the process of hepatocarcinogenesis.
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Affiliation(s)
- Yasunari Nakamoto
- Department of Gastroenterology, Graduate School of Medicine, Kanazawa University, Kanazawa, Japan
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103
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Khan N, Guarnieri M, Ahn SH, Li J, Zhou Y, Bang G, Kim KH, Wands JR, Tong S. Modulation of hepatitis B virus secretion by naturally occurring mutations in the S gene. J Virol 2004; 78:3262-70. [PMID: 15016847 PMCID: PMC371066 DOI: 10.1128/jvi.78.7.3262-3270.2004] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Alteration in hepatitis B virus (HBV) secretion efficiency may have pathological consequences. Naturally occurring mutations that regulate virion secretion have not been defined. We recently identified HBV genomes displaying high (4B), substantially reduced (3.4), or negative (4C) virion secretion. In the present study, the underlying mutations were mapped. A T552C point mutation in the 4B genome was responsible for its enhanced virion secretion, whereas a G510A mutation in 3.4 and G660C in 4C impaired virus secretion. The three point mutations generate M133T, G119E, and R169P substitutions in the S domains of viral envelope proteins, respectively, without modifying the coding capacity of the overlapping polymerase gene. The mutated residues are predicted to lie in the luminal side of the endoplasmic reticulum (ER) or to be embedded in the ER membrane and thus are not involved in contact with core particles during envelopment. Of the two mutations inhibitory of virion secretion, G510A greatly reduced small envelope protein (hepatitis B surface antigen [HBsAg]) levels both inside cells and in culture medium, whereas G660C specifically abolished HBsAg secretion. Surprisingly, a T484G mutation in the 4B genome, generating an I110M substitution in the S domain, could also reduce HBsAg secretion and block virion secretion. However, its inhibitory effect was suppressed in the 4B genome by the T552C mutation, the enhancer of virion secretion. T552C can also override the inhibitory G510A mutation, but not the G660C mutation. These findings suggest a hierarchy in the regulation of virion secretion and a close link between defective virion secretion and impaired HBsAg formation or secretion.
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Affiliation(s)
- Nasser Khan
- The Liver Research Center and Brown Medical School, Providence, Rhode Island 02903, USA
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104
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Raimondo G, Costantino L, Caccamo G, Pollicino T, Squadrito G, Cacciola I, Brancatelli S. Non-sequencing molecular approaches to identify preS2-defective hepatitis B virus variants proved to be associated with severe liver diseases. J Hepatol 2004; 40:515-9. [PMID: 15123368 DOI: 10.1016/j.jhep.2003.11.025] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/08/2003] [Revised: 11/17/2003] [Accepted: 11/20/2003] [Indexed: 12/04/2022]
Abstract
BACKGROUND/AIMS PreS2-defective hepatitis B virus (HBV) variants may emerge during chronic HBV infection. These variants carry mutation(s) at the ATG-start-codon and/or in-frame deletion into the preS2 genomic region and are commonly detected by sequencing analyses. We evaluated the prevalence of these variants in a large series of chronic HBV infected patients through non-sequencing molecular approaches. METHODS We examined HBV isolates from 110 HBV carriers: 15 were inactive carriers (IC); 50 had chronic hepatitis (CH); 25 were cirrhotics; 19 had hepatocellular carcinoma (HCC). The entire preS2 genomic region was amplified by PCR technique. The amplicons were processed: (A) through electrophoresis on acrylamide gel to reveal deleted genomes; (B) through electrophoresis on agarose gel after digestion by NlaIII enzyme that cuts the wild ATG-start-codon but not the mutated one. RESULTS We detected preS2 variants in 56/110 cases (51%). In particular, we found preS2-defective mutants in 2/15 IC, 25/50 CH, 13/26 cirrhotics, and 16/19 HCC. The presence of these variants was thus significantly associated with active infection and liver disease (P<0.002). Moreover, among cases with liver disease preS2-mutants were more prevalent in HCC patients (P<0.02). CONCLUSIONS Our non-sequencing molecular methods are sensitive and specific, and simplify the identification of all preS2 HBV variant forms. Infection by these variants is significantly associated with active infection and HCC.
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Affiliation(s)
- Giovanni Raimondo
- Unità di Epatologia Clinica e Biomolecolare, Dipartimento di Medicina Interna, Policlinico Universitario di Messina, 98124 Messina, Italy.
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105
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Wang HC, Wu HC, Chen CF, Fausto N, Lei HY, Su IJ. Different types of ground glass hepatocytes in chronic hepatitis B virus infection contain specific pre-S mutants that may induce endoplasmic reticulum stress. THE AMERICAN JOURNAL OF PATHOLOGY 2003; 163:2441-9. [PMID: 14633616 PMCID: PMC1892360 DOI: 10.1016/s0002-9440(10)63599-7] [Citation(s) in RCA: 180] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Ground glass hepatocyte (GGH) represents a histological hallmark of chronic hepatitis B virus infection and contains surface antigens in the endoplasmic reticulum (ER). Several types of GGHs are recognized at different hepatitis B virus replicative stages. The recent identification of pre-S mutants from GGHs encourages us to investigate whether different GGHs may harbor specific mutants and exhibit differential biological activities. In this study, we applied laser capture microdissection to isolate specific GGHs from a total of 50 samples on eight resected liver specimens. The surface genes in two major types of GGHs were analyzed. Type I GGHs expressed an inclusion-like pattern of hepatitis B surface antigens and harbored mutants with deletions over pre-S1 region, whereas type II GGHs, distributed in clusters and emerged at late replicative phase, contained mutants with deletions over pre-S2 region that defines a cytotoxic T lymphocyte (CTL) immune epitope, and may represent an immune escape mutant. Transfection of pre-S mutants in Huh7 revealed decreased syntheses of middle and small S proteins with accumulation of large surface antigen in ER, which in turn led to the activation of ER stress response with differential activities for different mutants. This study therefore demonstrates that different GGHs may contain specific mutants and exhibit differential biological activities.
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Affiliation(s)
- Hui-Ching Wang
- Graduate Institutes of Basic Medical Sciences, Molecular Medicine, and Immunology and Microbiology, National Cheng Kung University College of Medicine, Tainan, Taiwan
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106
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Roh S, Kim K. Overcoming tolerance in hepatitis B virus transgenic mice: a possible involvement of regulatory T cells. Microbiol Immunol 2003; 47:453-60. [PMID: 12906106 DOI: 10.1111/j.1348-0421.2003.tb03370.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
The hepatitis B virus (HBV) transgenic mouse (Tg) 50-4 strain is immunologically tolerant to HBV antigens. Various vaccination strategies have been attempted but failed to break the tolerance in the mouse. Although the tolerance to HBV antigen is maintained, this mouse strain develops spontaneous liver disease beginning at the age of about 3 months. We attempted to induce immune responses to HBV surface antigen (HBsAg) in the Tg by immunization with recombinant vaccinia virus expressing HBsAg (vvHBV), and observed different immunological responsiveness between 2-month-old and 5-month-old Tg. In contrast to the unbreakable tolerance reported previously, we could induce both the cytotoxic T lymphocyte (CTL) and the antibody response against HBsAg by the vvHBV immunization. The cytokine expression pattern indicated that T helper 1 type immune response was induced. However, interestingly, these immune responses were observed only in the 5-month-old Tg, but not in the 2-month-old Tg. Furthermore, CD4+ T cells from 2-month-old mice, but not those from 5-month-old mice, inhibited CTL response to HBV antigen when adoptively transferred to C57BL/6. These results suggest the possible involvement of regulatory T cell function in the HBV Tg for maintaining tolerance. This study would contribute to a better understanding of immune status of the HBV Tg as a model of human chronic hepatitis and to the search for new therapeutic targets for chronic viral infections.
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Affiliation(s)
- Sujin Roh
- Division of Molecular Life Sciences and College of Pharmacy, Ewha Women's University, 11 Daehyundong, Seoul 120-750, Korea
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107
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Gerner P, Schäfer HMC, Prange R, Pravitt D, Wirth S. Functional analysis of a rare HBV deletion mutant in chronically infected children. Pediatr Res 2003; 53:891-7. [PMID: 12646724 DOI: 10.1203/01.pdr.0000064906.63939.72] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Liver damage caused by chronic hepatitis B virus (HBV) infection may be enhanced through the selection of deleted HBV preS mutants by intracellular accumulation of viral proteins and subsequent cell death. However, the prevalence and impact of such mutants on the clinical course of infection have not yet been studied in children. Serum samples from 60 children (mean age 9.8 y) were investigated by means of PCR and direct sequencing of the entire preS region. Only one patient (1.5%) was found with a mixed HBV population of a deletion spanning 183 nucleotides and wild-type sequences. This mutation alters the HBV large-surface protein and removes the small-surface promoter. To clarify the significance of this mutation, we studied 14 serial serum samples of the child within a follow-up of 10 y. After occurrence of the mutation, the liver enzymes increased, despite seroconversion to anti-HBe. Transfection of an HBV expression construct containing this deletion into human hepatoma cells by using an HBV in vitro replication system showed that the mutant lost the ability of nucleocapsid packaging as a result of alteration of the transmembrane topology of the large surface protein. This effect could not be restored by coexpression of wild-type large- or small-surface proteins in trans. In conclusion, the circulation of HBV preS deletion mutants is rare in childhood. However, our functional and clinical follow-up studies in one child suggest that such a mutant may have the potential to aggravate liver inflammation, especially if corroborated with larger numbers of children.
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Affiliation(s)
- Patrick Gerner
- Children's Hospital, Helios Klini Kum, Wuppertal, Heusnerstrasse 40, D-42283 Wuppertal, Germany
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108
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Holzer GW, Mayrhofer J, Leitner J, Blum M, Webersinke G, Heuritsch S, Falkner FG. Overexpression of hepatitis B virus surface antigens including the preS1 region in a serum-free Chinese hamster ovary cell line. Protein Expr Purif 2003; 29:58-69. [PMID: 12729726 DOI: 10.1016/s1046-5928(03)00011-1] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Current hepatitis B virus (HBV) vaccines consist of preparations of recombinant HBV major surface antigen (sAg) and are protective in about 90-95% of vaccinated subjects. In improved vaccines, the frequency of nonresponders to the classical vaccine could be reduced by including additional epitopes from the preS-domains of the middle and large surface antigens. In this report, the development and characterization of a CHO cell line for HBsAg, expressing major, middle, and large antigens are described. Despite the previously reported retention of secreted proteins by the preS1 domain, cell lines could be amplified that secreted large amounts of the complete set of antigens. A producer line was established that expressed 1mg HBsAg per 100ml suspension culture per week during exponential growth. The productivity per cell increased further by at least threefold when the culture reached the stationary phase at high cell densities. In the production cell line, several hundred copies of the HBV vector were integrated at two adjacent sites into chromosome 2. The cell line was adapted to growth in a defined protein-free medium minimizing the risk of adventitious agents introduced by animal derived supplements. The cell line stably produced antigen over several months. In the candidate vaccine, both preS2 and preS1 domains were present at ratios similar to HBsAg from human sera. In summary, a production cell line for an improved HBV vaccine is presented with properties such as high productivity, long term stability of expression, and growth in protein-free media.
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Affiliation(s)
- Georg W Holzer
- Baxter Vaccine AG, Biomedical Research Center, Uferstrasse 15, A-2304 Orth/Donau, Austria
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109
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Foo NC, Ahn BY, Ma X, Hyun W, Yen TSB. Cellular vacuolization and apoptosis induced by hepatitis B virus large surface protein. Hepatology 2002. [PMID: 12447865 DOI: 10.1002/hep.1840360616] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Fibrosing cholestatic hepatitis (FCH) is a rapidly progressive form of viral hepatitis B that occurs in severely immunosuppressed patients. Pathologically, the liver in FCH is characterized by widespread hepatocyte vacuolization and apoptosis, which, in contrast to more common forms of hepatitis B, is only rarely associated with significant inflammation. Therefore, it has been proposed that, in FCH, hepatocytes may be injured by a direct cytopathic effect of the virus rather than by the host immune response. In support of this hypothesis, we present evidence that cultured hepatoma cells that had been transfected with a plasmid selectively expressing the viral large surface protein form numerous large vacuoles and undergo apoptosis. The similarity of the cytopathology in FCH in vivo and in these transfected cells in vitro strongly implicates the large surface protein as the direct cause of this acute liver disease. This conclusion is further supported by the published demonstration that hepatocytes tend to accumulate large surface protein in FCH, which may reflect its overexpression by the virus. In conclusion, our data implicate the large surface protein as a major cause of hepatocyte injury in fibrosing cholestatic hepatitis.
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Affiliation(s)
- Ngee-Chih Foo
- Pathology Service, San Francisco VA Medical Center, San Francisco, CA, USA
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110
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Dong Y, Xi H, Yu Y, Wang Q, Jiang K, Li L. Effects of oxymatrine on the serum levels of T helper cell 1 and 2 cytokines and the expression of the S gene in hepatitis B virus S gene transgenic mice: a study on the anti-hepatitis B virus mechanism of oxymatrine. J Gastroenterol Hepatol 2002; 17:1299-306. [PMID: 12423275 DOI: 10.1046/j.1440-1746.2002.02885.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
BACKGROUND Oxymatrine has been shown to have a remarkable inhibitory activity to hepatitis B virus (HBV) infection with a hepatitis B virus e antigen (HBeAg) serum conversion rate of approximately 45%. In order to explore the anti-HBV mechanism of oxymatrine, the effects of oxymatrine on serum levels of T helper (h)1 cytokines (interferon (IFN)-gamma and interleukin (IL)-2) and Th2 cytokines (IL-4 and IL-10), and the expression of S gene in HBV S gene transgenic mice were studied. METHODS Each transgenic mouse was either injected with oxymatrine or saline intraperitoneally once a day for 30 days. Serum levels of IFN-gamma, IL-2, IL-4 and IL-10 were quantitated and compared to the data before the treatment. The expression of HBV S gene in transgenic mice was analyzed at the DNA, mRNA and protein levels. RESULTS The serum levels of IFN-gamma in transgenic mice before or after oxymatrine treatment were 3.108 +/- 3.172 and 11.059 +/- 6.971 pg/mL, respectively. In contrast, serum levels before and after oxymatrine treatment for IL-4 were 29.045 +/- 13.235 and 13.024 +/- 9.002 pg/mL, respectively (P < 0.001). The serum levels of IL-2 in the control (saline injection) and oxymatrine-treated mice were 1.070 +/- 0.447 and 5.537 +/- 2.887 pg/mL, respectively (P < 0.0001); and that of IL-10 were 97.226 +/- 73.306 and 33.607 +/- 23.154 pg/mL, respectively (P < 0.01). No significant differences were observed in the expression of HBV S gene in the transgenic mice at the DNA, mRNA and protein levels before or after oxymatrine treatment. CONCLUSIONS The fact that Th1 cytokines are increased while Th2 cytokines are decreased suggests that oxymatrine treatment triggers the change of immune response to hepatitis B infection in transgenic mice, which leads to improved HBV inhibitory activities. The study can help us better understand the mechanisms of the anti-HBV drug, oxymatrine, and how it has potential as an application in clinical chronic hepatitis B treatment.
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Affiliation(s)
- Yuhong Dong
- Department of Infectious Disease, Peking University First Hospital, Beijing, China.
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111
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Nakamoto Y, Kaneko S, Fan H, Momoi T, Tsutsui H, Nakanishi K, Kobayashi K, Suda T. Prevention of hepatocellular carcinoma development associated with chronic hepatitis by anti-fas ligand antibody therapy. J Exp Med 2002; 196:1105-11. [PMID: 12391022 PMCID: PMC2194047 DOI: 10.1084/jem.20020633] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
A persistent immune response to hepatitis viruses is a well-recognized risk factor for hepatocellular carcinoma. However, the molecular and cellular basis for the procarcinogenic potential of the immune response is not well defined. Here, using a unique animal model of chronic hepatitis that induces hepatocellular carcinogenesis, we demonstrate that neutralization of the activity of Fas ligand prevented hepatocyte apoptosis, proliferation, liver inflammation, and the eventual development of hepatocellular carcinoma. The results indicate that Fas ligand is involved not only in direct hepatocyte killing but also in the process of inflammation and hepatocellular carcinogenesis in chronic hepatitis. This is the first demonstration that amelioration of chronic inflammation by some treatment actually caused reduction of cancer development.
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Affiliation(s)
- Yasunari Nakamoto
- Department of Gastroenterology, Graduate School of Medicine. Center for the Development of Molecular Target Drugs, Cancer Research Institute, Kanazawa University, Ishikawa 920-0934, Japan
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112
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Le Pogam S, Shih C. Influence of a putative intermolecular interaction between core and the pre-S1 domain of the large envelope protein on hepatitis B virus secretion. J Virol 2002; 76:6510-7. [PMID: 12050364 PMCID: PMC136289 DOI: 10.1128/jvi.76.13.6510-6517.2002] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Virion release of hepatitis B virus (HBV) from hepatocytes is a tightly regulated event. It is a dogma that only the mature HBV genome is preferentially allowed to export from the intracellular compartment (J. Summers and W. S. Mason, Cell 29:403-415, 1982). Recently, an "immature secretion" phenotype of a highly frequent naturally occurring HBV variant containing a leucine residue at amino acid 97 of the core protein was identified. Unlike wild-type HBV, this variant secretes almost equal amounts of mature and immature genomes. This phenomenon is not caused by any instability of core particles or by any deficiency in viral reverse transcription (T. T. Yuan, P. C. Tai, and C. Shih, J. Virol. 73:10122-10128, 1999). In this study, our kinetic analysis of virion secretion of the mutant F97L (phenylalanine to leucine) indicates that the secretion of its immature genome does not occur earlier than that of its mature genome. In addition, the secretion kinetics of the mature genomes are comparable between the wild-type HBV and the mutant F97L. Therefore, the immature secretion phenomenon of mutant F97L is not caused by premature secretion or more efficient secretion. Previously, we hypothesized that the immature secretion phenotype is probably caused by the aberrant interaction between its mutant core and wild-type envelope proteins. Here, we further demonstrated that a pre-S1 envelope mutation at position 119, changing an alanine (A) to a phenylalanine (F), can offset the immature secretion phenotype of the mutant I97L (isoleucine to leucine) and successfully restore the wild-type-like selective export of the mature genome of the double mutant pre-S1-A119F/core-I97L.
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Affiliation(s)
- Sophie Le Pogam
- Center for Tropical Diseases, Department of Pathology, University of Texas Medical Branch, Galveston, TX 77555-0609, USA
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113
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Abstract
OBJECTIVE Pancreatic cancer has an extremely poor prognosis and the cellular mechanisms contributing to pancreatic cancer are relatively unknown. The goals of this review are to present the epidemiological and experimental data that supports inflammation as a key mediator of pancreatic cancer development, to explain how inflammatory pathways may create an environment that supports tumor formation, and to discuss how the use of novel agents directed at these pathways may be used for the treatment of pancreatic malignancy. SUMMARY BACKGROUND DATA Inflammation has been identified as a significant factor in the development of other solid tumor malignancies. Both hereditary and sporadic forms of chronic pancreatitis are associated with an increased risk of developing pancreatic cancer. The combined increase in genomic damage and cellular proliferation, both of which are seen with inflammation, strongly favors malignant transformation of pancreatic cells. Cytokines, reactive oxygen species, and mediators of the inflammatory pathway (e.g., NF-kappaB and COX-2) have been shown to increase cell cycling, cause loss of tumor suppressor function, and stimulate oncogene expression; all of which may lead to pancreatic malignancy. Anti-cytokine vaccines, inhibitors of pro-inflammatory NF-kappaB and COX-2 pathways, thiazolidinediones, and anti-oxidants are potentially useful for the prevention or treatment of pancreatic cancer. Redirection of experimental interests toward pancreatic inflammation and mechanisms of carcinogenesis may identify other novel anti-inflammatory agents or other ways to screen for or prevent pancreatic cancer. CONCLUSION Pancreatic inflammation, mediated by cytokines, reactive oxygen species, and upregulated pro-inflammatory pathways, may play a key role in the early development of pancreatic malignancy.
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Affiliation(s)
- Buckminster Farrow
- Department of Surgery, The University of Texas Medical Branch, 301 University Boulevard, Galveston 77555, USA
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114
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Trobonjaca Z, Kröger A, Stober D, Leithäuser F, Möller P, Hauser H, Schirmbeck R, Reimann J. Activating immunity in the liver. II. IFN-beta attenuates NK cell-dependent liver injury triggered by liver NKT cell activation. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2002; 168:3763-70. [PMID: 11937527 DOI: 10.4049/jimmunol.168.8.3763] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Dendritic cell (DC)-dependent activation of liver NKT cells triggered by a single i.v. injection of a low dose (10-100 ng/mouse) of alpha-galactosyl ceramide (alphaGalCer) into mice induces liver injury. This response is particularly evident in HBs-tg B6 mice that express a transgene-encoded hepatitis B surface Ag in the liver. Liver injury following alphaGalCer injection is suppressed in mice depleted of NK cells, indicating that NK cells play a role in NK T cell-initiated liver injury. In vitro, liver NKT cells provide a CD80/86-dependent signal to alphaGalCer-pulsed liver DC to release IL-12 p70 that stimulates the IFN-gamma response of NKT and NK cells. Adoptive transfer of NKT cell-activated liver DC into the liver of nontreated, normal (immunocompetent), or immunodeficient (RAG(-/-) or HBs-tg/RAG(-/-)) hosts via the portal vein elicited IFN-gamma responses of liver NK cells in situ. IFN-beta down-regulates the pathogenic IL-12/IFN-gamma cytokine cascade triggered by NKT cell/DC/NK cell interactions in the liver. Pretreating liver DC in vitro with IFN-beta suppressed their IL-12 (but not IL-10) release in response to CD40 ligation or specific (alphaGalCer-dependent) interaction with liver NKT cells and down-regulated the IFN-gamma response of the specifically activated liver NKT cells. In vivo, IFN-beta attenuated the NKT cell-triggered induction of liver immunopathology. This study identifies interacting subsets of the hepatic innate immune system (and cytokines that up- and down-regulate these interactions) activated early in immune-mediated liver pathology.
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MESH Headings
- Adoptive Transfer
- Animals
- Antigens, CD/physiology
- B7-1 Antigen/physiology
- B7-2 Antigen
- Cells, Cultured
- Coculture Techniques
- Cytotoxicity, Immunologic/genetics
- Cytotoxicity, Immunologic/immunology
- Dendritic Cells/drug effects
- Dendritic Cells/immunology
- Dendritic Cells/metabolism
- Dendritic Cells/transplantation
- Galactosylceramides/administration & dosage
- Galactosylceramides/pharmacology
- Immunosuppressive Agents/pharmacology
- Injections, Intravenous
- Interferon-beta/pharmacology
- Interleukin-12/antagonists & inhibitors
- Interleukin-12/metabolism
- Interleukin-12/physiology
- Killer Cells, Natural/drug effects
- Killer Cells, Natural/immunology
- Killer Cells, Natural/metabolism
- Liver/immunology
- Liver/pathology
- Lymphocyte Activation/genetics
- Lymphocyte Activation/immunology
- Membrane Glycoproteins/physiology
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Mice, Transgenic
- T-Lymphocyte Subsets/immunology
- T-Lymphocyte Subsets/metabolism
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Affiliation(s)
- Zlatko Trobonjaca
- Department of Physiology and Immunology, Medical Faculty, University of Rijeka, Rijeka, Croatia
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115
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Baron JL, Gardiner L, Nishimura S, Shinkai K, Locksley R, Ganem D. Activation of a nonclassical NKT cell subset in a transgenic mouse model of hepatitis B virus infection. Immunity 2002; 16:583-94. [PMID: 11970881 DOI: 10.1016/s1074-7613(02)00305-9] [Citation(s) in RCA: 171] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
NKT cells are specialized cells of the immune system that bear both T cell and NK cell markers. Classical NKT cells display TCRs of restricted heterogeneity (Valpha14-Jalpha281) and recognize lipid antigens (e.g., alpha-galactosyl ceramide) presented by nonpolymorphic CD1 molecules. Recently, other nonclassical NKT subsets have been recognized, including NKT cells not reactive with CD1d-alpha-galactosyl ceramide complexes. The biological functions of these cells are unknown. Here, we show that nonclassical NKT cells that are CD1d restricted but nonreactive to alpha-GalCer are activated in response to hepatocytes expressing hepatitis B viral antigens in a transgenic mouse model of acute hepatitis B virus infection. Our results document the first in vivo function for such nonclassical NKT cells and suggest a role for these cells in the host response to HBV infection.
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MESH Headings
- Acute Disease
- Adoptive Transfer
- Animals
- Antigens, CD1/immunology
- Antigens, CD1d
- Antigens, Viral/genetics
- Disease Models, Animal
- Female
- Galactosylceramides/immunology
- Hepatitis B/immunology
- Hepatitis B e Antigens/genetics
- Hepatitis B virus/genetics
- Hepatitis B virus/immunology
- Hepatitis B, Chronic/immunology
- Homeodomain Proteins/genetics
- Humans
- Killer Cells, Natural/immunology
- Liver/cytology
- Lymphocyte Activation/immunology
- Male
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Mice, Transgenic
- Receptors, Antigen, T-Cell, alpha-beta/immunology
- Spleen/cytology
- T-Lymphocyte Subsets/immunology
- Transgenes
- Virus Replication
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Affiliation(s)
- Jody L Baron
- Department of Microbiology/Immunology, Howard Hughes Medical Institute, University of California Medical Center, San Francisco, CA 94143, USA
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116
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Tai PC, Suk FM, Gerlich WH, Neurath AR, Shih C. Hypermodification and immune escape of an internally deleted middle-envelope (M) protein of frequent and predominant hepatitis B virus variants. Virology 2002; 292:44-58. [PMID: 11878907 DOI: 10.1006/viro.2001.1239] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Naturally occurring deletions within the human hepatitis B virus (HBV) preS2 region have frequently been identified in patients with hepatocellular carcinoma (HCC), while chronic carriers without cirrhosis and HCC contain no detectable preS2 deletion variants. We have characterized two different preS2 internal deletion variants from two patients. In addition to several weak phenotypes, our study revealed three unexpected strong phenotypes: (1) a paradoxical "hypermodification" phenomenon was observed with significantly increased size heterogeneity and molecular weights of the secreted middle (M) envelope proteins containing a preS2 internal deletion. This phenomenon was observed in transient transfection with a human hepatoma Huh7 cell line as well as in stable transfection with a rodent hepatoma cell line 7777. (2) A significantly increased intracellular accumulation of all three envelope proteins (large, middle, and small) was detected by both Western blot analysis and immunofluorescence microscopy. (3) The middle envelope proteins with a preS2 internal deletion were not recognized in vitro by a putative neutralizing antiserum, suggesting that these variants can evade immune recognition in vivo. To our knowledge, this is the first identification and characterization of the M deletion variant protein in HBV natural infection.
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Affiliation(s)
- Pei-Ching Tai
- Center for Tropical Diseases, University of Texas Medical Branch, Galveston, Texas, 77555-0609, USA
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117
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Chouteau P, Le Seyec J, Cannie I, Nassal M, Guguen-Guillouzo C, Gripon P. A short N-proximal region in the large envelope protein harbors a determinant that contributes to the species specificity of human hepatitis B virus. J Virol 2001; 75:11565-72. [PMID: 11689638 PMCID: PMC114743 DOI: 10.1128/jvi.75.23.11565-11572.2001] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2001] [Accepted: 08/29/2001] [Indexed: 12/17/2022] Open
Abstract
Infection by hepatitis B virus (HBV) is mainly restricted to humans. This species specificity is likely determined at the early phase of the viral life cycle. Since the envelope proteins are the first viral factors to interact with the cell, they represent attractive candidates for controlling the HBV host range. To investigate this assumption, we took advantage of the recent discovery of a second virus belonging to the primate Orthohepadnavirus genus, the woolly monkey HBV (WMHBV). A recombinant plasmid was constructed for the expression of all WMHBV envelope proteins. In additional constructs, N-terminal sequences of the WMHBV large envelope protein were substituted for their homologous HBV counterparts. All wild-type and chimeric WMHBV surface proteins were properly synthesized by transfected human hepatoma cells, and they were competent to replace the original HBV proteins for the production of complete viral particles. The resulting pseudotyped virions were evaluated for their infectious capacity on human hepatocytes in primary culture. Virions pseudotyped with wild-type WMHBV envelope proteins showed a significant loss of infectivity. By contrast, infectivity was completely restored when the first 30 residues of the large protein originated from HBV. Analysis of smaller substitutions within this domain limited the most important region to a stretch of only nine amino acids. Reciprocally, replacement of this motif by WMHBV residues in the context of the HBV L protein significantly reduced infectivity of HBV. Hence this short region of the L protein contributes to the host range of HBV.
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Affiliation(s)
- P Chouteau
- Régulation des Equilibres Fonctionnels du Foie Normal et Pathologique U 522, Hôpital de Pontchaillou, Institut National de la Santé et de la Recherche Médicale, 35033 Rennes Cedex, France
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118
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Trobonjaca Z, Leithäuser F, Möller P, Schirmbeck R, Reimann J. Activating immunity in the liver. I. Liver dendritic cells (but not hepatocytes) are potent activators of IFN-gamma release by liver NKT cells. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2001; 167:1413-22. [PMID: 11466360 DOI: 10.4049/jimmunol.167.3.1413] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
A prominent subset of the hepatic innate immune system is alpha-galactosylceramide (alphaGalCer)-reactive, (CD4(+) and CD4(-)CD8(-)) CD1d-restricted NKT cells. We investigated in C57BL/6 (B6) mice which hepatic cell type stimulates hepatic NKT cell activation. Surface expression of CD1d but not CD40, CD80, or CD86 costimulator molecules was detected in hepatocytes. Pulsed in vitro or in vivo with alphaGalCer, hepatocytes triggered IL-4 release by liver NKT cells but required exogenous IL-12 to trigger IFN-gamma release by NKT cells. Liver dendritic cells (DC) isolated from nontreated mice showed low surface expression of MHC, CD1d, and CD40, CD80, or CD86 costimulator molecules that were strikingly up-regulated after alphaGalCer injection. Although liver CD11c(+) DC displayed lower CD1d surface expression than hepatocytes, they were potent stimulators of IFN-gamma and IL-4 release by liver NKT when pulsed with alphaGalCer in vitro or in vivo. Liver DC are thus potent stimulators of proinflammatory cytokine release by NKT cells, are activated themselves in the process of NKT cell activation, and express an activated phenotype after the NKT cell population is eliminated following alphaGalCer stimulation.
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Affiliation(s)
- Z Trobonjaca
- Department of Medical Microbiology and Immunology, University of Ulm, Heimholtzstrasse 8/1, D-89081 Ulm, Germany
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119
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Abstract
The narrow host range of infection and lack of suitable tissue culture systems for the propagation of hepatitis B and C viruses are limitations that have prevented a more thorough understanding of persistent infection and the pathogenesis of chronic liver disease. With hepatitis B virus (HBV), this lack of knowledge has been partially overcome by the discovery and characterization of HBV-like viruses in wild animals. With hepatitis C virus (HCV), related flaviviruses have been used as surrogate systems for such studies. Other laboratories have developed transgenic mice that express virus gene products and/or support virus replication. Some HBV transgenic mouse models develop fulminant hepatitis, acute hepatitis, or chronic liver disease after adoptive transfer, and others spontaneously develop hepatocellular carcinoma (HCC), as in human infections. Among HCV transgenic mice, most develop no disease, but acute hepatitis has been observed in one model, and HCC in another. Although mice are not susceptible to HBV and HCV, their ability to replicate these viruses and to develop liver diseases characteristic of human infections provides new opportunities to study pathogenesis and develop novel therapeutics.
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Affiliation(s)
- M A Feitelson
- Department of Pathology, Anatomy, and Cell Biology and in the Department of Microbiology and Immunology, Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, Pennsylvania, USA
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120
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Abstract
Animal models of hepatitis B virus infection have been valuable for determining the mechanisms of hepadnavirus replication, for studies of pathogenesis, and for investigations of viral hepatocarcinogenesis. The woodchuck model also seems to be useful in the discovery and development of antiviral drugs to treat HBV infection and for testing new forms of immunotherapy. In particular, the woodchuck seems to be ideal for studying the effect of antiviral treatment and immunotherapy on the outcome of hepadnavirus infection and on survival. The median life expectancy of experimentally infected, chronic WHV carriers is approximately 29 months, and almost all develop HCC. New types of prophylaxis or therapy can be evaluated under controlled experimental conditions, in a relevant animal model, and within a reasonable time frame.
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Affiliation(s)
- B C Tennant
- Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York, USA
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121
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Fan YF, Lu CC, Chang YC, Chang TT, Lin PW, Lei HY, Su IJ. Identification of a pre-S2 mutant in hepatocytes expressing a novel marginal pattern of surface antigen in advanced diseases of chronic hepatitis B virus infection. J Gastroenterol Hepatol 2000; 15:519-28. [PMID: 10847439 DOI: 10.1046/j.1440-1746.2000.02187.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
BACKGROUND AND AIMS The expression of hepatitis B viral (HBV) antigens in liver tissue reflects the replicative status of chronic HBV infection. We have previously recognized a novel marginal pattern of hepatitis B surface antigen (HBsAg) in hepatocytes, which usually clusters in groups and emerges at the late non-replicative phase. This study was designed to investigate whether the marginal-type HBsAg represented the gene product of a specific HBV-surface mutant. METHODS Microdissection of cirrhotic nodules homogeneously expressing marginal HBsAg was performed on two of 12 resected livers from HBsAg-seropositive patients with hepatocellular carcinoma. The gene presumably encoding marginal HBsAg was polymerase chain reaction (PCR)-cloned, sequenced and analysed. In vitro transfection and expression of the cloned surface mutant plasmids were performed on the Huh7 cell line to illustrate intrahepatic HBsAg expression. RESULTS Immunohistochemical staining revealed that the marginal HBsAg was positive for pre-S1 and thus contained large surface proteins. The PCR cloning and sequencing of the genes presumably encoding marginal-type HBsAg in both cases revealed the same deletion at the 5' terminus (nt 2-55) of pre-S2. A point mutation on the small-surface (S) antigen was also found in one case. The pre-S2 deletion sequence and the mutation sites of the S gene coincide with human lymphocyte antigen-restricted T- and/or B-cell epitopes. In vitro transfection of the mutant plasmid revealed a blot-like retention or accumulation of HBsAg in the cytoplasm or at the periphery of hepatocytes, accompanied by a decreased secretion of HBsAg in the culture supernatant, mimicking intrahepatic expression. CONCLUSION A natural pre-S2 deletion mutant was identified in hepatocytes expressing a novel marginal pattern of HBsAg, which probably contains mutant, large, surface proteins. The biological significance of the pre-S2 deletion mutant should be interesting in view of the clustering proliferation of hepatocytes expressing marginal HBsAg.
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Affiliation(s)
- Y F Fan
- Institute of Basic Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan
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122
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Foo NC, Yen TS. Activation of promoters for cellular lipogenic genes by hepatitis B virus large surface protein. Virology 2000; 269:420-5. [PMID: 10753720 DOI: 10.1006/viro.1999.0148] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Hepatitis B virus large surface protein has the unusual property of accumulating in a particulate form within a preGolgi compartment, leading to marked proliferation of intracellular membranes. We show here that large surface protein activates the promoters for two lipogenic genes that code for farnesyl diphosphate synthase and fatty acid synthase. This activation is transduced, in part, by the transcription factor NF-Y. Although NF-Y is also necessary for the transcriptional induction of chaperone proteins residing in the endoplasmic reticulum by unfolded proteins, other inducers of chaperone synthesis do not activate the promoters for farnesyl diphosphate synthase and fatty acid synthase. Our results suggest the presence of a novel signaling pathway from the endoplasmic reticulum to the nucleus that causes the intracellular membrane proliferation seen in the hepatocytes of persons with accumulated large surface protein particles.
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Affiliation(s)
- N C Foo
- Department of Pathology, University of California, San Francisco, California, 94143-0506, USA
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123
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Chisari FV. Rous-Whipple Award Lecture. Viruses, immunity, and cancer: lessons from hepatitis B. THE AMERICAN JOURNAL OF PATHOLOGY 2000; 156:1117-32. [PMID: 10751335 PMCID: PMC1876872 DOI: 10.1016/s0002-9440(10)64980-2] [Citation(s) in RCA: 242] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- F V Chisari
- Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, California 92037, USA.
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124
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Heise T, Guidotti LG, Chisari FV. La autoantigen specifically recognizes a predicted stem-loop in hepatitis B virus RNA. J Virol 1999; 73:5767-76. [PMID: 10364328 PMCID: PMC112637 DOI: 10.1128/jvi.73.7.5767-5776.1999] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/1999] [Accepted: 04/14/1999] [Indexed: 01/12/2023] Open
Abstract
We recently identified three nuclear proteins (p45, p39, and p26) that bind to a 91-nucleotide (nt) RNA element between nt 1243 and 1333 in hepatitis B virus (HBV) RNA, and we showed that these proteins and HBV RNA are regulated coordinately by gamma interferon and tumor necrosis factor alpha. Purification and sequence analysis of tryptic peptides obtained from p39 revealed sequence homology to the mouse La protein. Immunoprecipitation experiments showed that p45, p39, and p26 were recognized by anti-La-specific antiserum, indicating that p45 is the full-length La protein and that p39 and p26 are likely to be proteolytic La cleavage products. Furthermore, in competition experiments we found that all three La proteins bind, in a phosphorylation-dependent manner, to the same predicted stem-loop structure located between nt 1275 and 1291 of HBV, with Kds of approximately 1.0 nM. Collectively, these results support the notion that the La protein may contribute to HBV RNA stability, constitutively and in response to inflammatory cytokines.
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Affiliation(s)
- T Heise
- Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, California 92037, USA
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125
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126
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Chemin I, Ohgaki H, Chisari FV, Wild CP. Altered expression of hepatic carcinogen metabolizing enzymes with liver injury in HBV transgenic mouse lineages expressing various amounts of hepatitis B surface antigen. LIVER 1999; 19:81-7. [PMID: 10220736 DOI: 10.1111/j.1478-3231.1999.tb00015.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
Abstract
AIMS/BACKGROUND The objective of this work was to evaluate the possible modulation of carcinogen metabolizing enzymes in relation to chronic infection by hepatitis B virus (HBV). This was to test whether enzyme level is altered in association with HBV gene expression per se or only when that expression was associated with an induction of liver injury. METHODS For this purpose, we studied four different HBV transgenic mouse lineages (23.3, 45.2, 50.4 and 107.5) that express the transgene encoding for the large envelope protein (HBsAg) at different levels. These lineages exhibit an associated liver injury which progresses with age and is positively correlated with the degree of accumulation of HBsAg in the hepatocytes. The modulation of levels of cytochrome P450 (1a, 2a-5, 2b, 2c, 3A4 and 2E1) and glutathione S-transferases (GST alpha and pi) involved in carcinogen metabolism was examined by immunohistochemistry in these lineages. RESULTS While we observed an increase in staining intensity of P450s 1-a and 2a-5 in lineages expressing cytopathic amounts of HBsAg (lineages 50.4 and 45.2), we only observed minor changes or no changes at all for the other lineages (23.3 and 107.5). Staining with antibodies to cytosolic pi class GST demonstrated an increase in older mice, although no major alterations were observed for GST alpha. CONCLUSIONS These results suggest that liver cell injury induced by accumulation of HBV antigens can result in the induction of some carcinogen metabolizing enzymes and this may be one mechanism of chemical-viral interaction in hepatocarcinogenesis.
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Affiliation(s)
- I Chemin
- Unit of Environmental Carcinogenesis, International Agency for Research on Cancer, Lyon, France
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127
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Le Seyec J, Chouteau P, Cannie I, Guguen-Guillouzo C, Gripon P. Infection process of the hepatitis B virus depends on the presence of a defined sequence in the pre-S1 domain. J Virol 1999; 73:2052-7. [PMID: 9971786 PMCID: PMC104448 DOI: 10.1128/jvi.73.3.2052-2057.1999] [Citation(s) in RCA: 158] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
During the life cycle of hepatitis B virus (HBV), the large envelope protein (L) plays a pivotal role. Indeed, this polypeptide is essential for viral assembly and probably for the infection process. By performing mutagenesis experiments, we have previously excluded a putative involvement of the pre-S2 domain of the L protein in viral infectivity. In the present study, we have evaluated the role of the pre-S1 region in HBV infection. For this purpose, 21 mutants of the L protein were created. The entire pre-S1 domain was covered by contiguous deletions of 5 amino acids. First, after transfection into HepG2 cells, the efficient expression of both glycosylated and unglycosylated L mutant proteins was verified. The secretion rate of envelope proteins was modified positively or negatively by deletions, indicating that the pre-S1 domain contains several regulating sequences able to influence the surface protein secretion. The ability of mutant proteins to support the production of virions was then studied. Only the four C-terminal deletions, covering the 17 amino acids suspected to interact with the cytoplasmic nucleocapsids, inhibited virion release. Finally, the presence of the modified pre-S1 domain at the external side of all secreted virions was confirmed, and their infectivity was assayed on normal human hepatocytes in primary culture. Only a short sequence including amino acids 78 to 87 tolerates internal deletions without affecting viral infectivity. These results confirm the involvement of the L protein in the infection step and demonstrate that the sequence between amino acids 3 and 77 is involved in this process.
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Affiliation(s)
- J Le Seyec
- Unité de Recherches Hépatologiques U 49, Institut National de la Santé et de la Recherche Médicale, Hôpital de Pontchaillou, 35033 Rennes Cedex, France
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128
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Hildt E, Hofschneider PH. The PreS2 activators of the hepatitis B virus: activators of tumour promoter pathways. Recent Results Cancer Res 1999; 154:315-29. [PMID: 10027012 DOI: 10.1007/978-3-642-46870-4_23] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
In addition to causing acute and chronic hepatitis, hepatitis B virus (HBV) is considered to be a major cliological factor in the development of human hepatocellular carcinoma (HCC). Epidemiological studies have demonstrated an approximately 10-fold increase in the relative risk of HCC among HBV carried compared to noncarriers. Almost all HBV-associated HCCs studied so far harbor chromosomally integrated HBV DNA. Integrated viral DNA can encode two types of transcriptional activators, the HBx protein and the PreS2 activators [the large surface proteins (LHBs) and truncated middle surface proteins (MHBs)]. The activator function of the PreS2 activators is based on the cytoplasmic orientation of the PreS2 domain. The PreS2 domain is PKC-dependent phosphorylated. Moreover, the PreS2 domain binds of PKC alpha/beta and triggers a PKC-dependent activation of the c-Raf-1/MAP2-kinase signal transduction cascade, resulting in an activation of transcription factors such as AP-1 and NF-kB. Furthermore, by activation of this signaling cascade, the PreS2 activators cause an increased proliferation rate of hepatocytes. According to the two-step model of carcinogenesis (initiation/promotion), the PreS2 activators could exert a tumour-promoter-like function by activation of the PKC/c-Raf-1/MAP2-kinase signaling cascade: cells harboring critical mutations (initiation) may be positively selected (promotion). Such a multistep process may account for the long latency period in HCC development, but it also leads to the hypothesis that each tumor reflects an individual case.
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Affiliation(s)
- E Hildt
- Institute of Experimental Surgery, Technical University of Munich, Germany
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129
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Ilan E, Burakova T, Dagan S, Nussbaum O, Lubin I, Eren R, Ben-Moshe O, Arazi J, Berr S, Neville L, Yuen L, Mansour TS, Gillard J, Eid A, Jurim O, Shouval D, Reisner Y, Galun E. The hepatitis B virus-trimera mouse: a model for human HBV infection and evaluation of anti-HBV therapeutic agents. Hepatology 1999; 29:553-62. [PMID: 9918935 DOI: 10.1002/hep.510290228] [Citation(s) in RCA: 72] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Previous studies have demonstrated the feasibility of implantation of human blood cells or tissues in lethally irradiated mice or rats, radioprotected with SCID mouse bone marrow cells: The Trimera system. In the present study, we describe the development of a mouse Trimera model for human hepatitis B virus (HBV) infection. In this model, viremia is induced by transplantation of ex vivo HBV-infected human liver fragments. Engraftment of the human liver fragments, evaluated by hematoxylin-eosin staining and human serum albumin mRNA expression, was observed in 85% of the transplanted animals 1 month postimplantation. Viremia levels were determined in these mice by measuring serum HBV DNA using polymerase chain reaction (PCR), followed by dot-blot hybridization. HBV DNA is first detected 8 days after liver transplantation. Viremia attains a peak between days 18 and 25 when HBV infection is observed in 85% of the transplanted animals. The HBV-Trimera model was used to evaluate the therapeutic effects of human polyclonal anti-HBs antibodies (Hepatect) and of two reverse-transcriptase inhibitors, lamivudine (3TC) and beta-L-5-fluoro-2',3'-dideoxycytidine (beta-L-5FddC). Treatment of HBV-Trimera mice with these drugs effectively reduced both the percentage of infected animals and the viral load in their sera. Treatment cessation resulted in rebound of viral load, indicating HBV replication upon drug withdrawal. These results show that the HBV-Trimera model represents a novel experimental tool for simulating human HBV infection and evaluating potential anti-HBV therapeutic agents.
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Affiliation(s)
- E Ilan
- XTL Biopharmaceuticals Ltd., Kiryat Weizmann, Rehovot, Israel
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130
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Shimizu Y, Guidotti LG, Fowler P, Chisari FV. Dendritic Cell Immunization Breaks Cytotoxic T Lymphocyte Tolerance in Hepatitis B Virus Transgenic Mice. THE JOURNAL OF IMMUNOLOGY 1998. [DOI: 10.4049/jimmunol.161.9.4520] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Abstract
Hepatitis B virus (HBV) transgenic mice that are immunologically tolerant to HBV-encoded Ags represent a model of chronic HBV infection suitable for the development of therapeutic immunization strategies before testing in humans. Five lineages of HBV transgenic mice were immunized with plasmid DNA that encodes hepatitis B surface Ag (HBsAg) or with cytokine-activated bone marrow-derived dendritic cells (DCs) in an attempt to break tolerance to HBsAg at the B and T cell levels. DNA immunization stimulated an Ab response but not a cytotoxic T lymphocyte response to HBsAg in two of the five transgenic lineages studied. In contrast, infusion of activated transgenic or nontransgenic DCs stimulated a splenic CTL response in all three transgenic lineages immunized in this manner at precursor frequencies comparable to those in nontransgenic mice, indicating that DC function is normal, and HBsAg-specific CTLs are present but functionally silent in these transgenic animals. Importantly, none of the animals developed hepatitis or displayed suppressed viral gene expression or replication following either DNA immunization or DC administration even in the presence of anti-hepatitis B surface (HBs) Abs and HBs-specific CTLs. These results indicate that Ag presentation by cytokine-activated DCs can break tolerance and trigger an anti-viral CTL response in HBV transgenic mice, and they suggest that this strategy is more efficient than DNA immunization in this setting. Nonetheless, more efficient immunization strategies are needed to stimulate an immune response of sufficient quality and magnitude to achieve an immunotherapeutic antiviral effect.
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Affiliation(s)
- Yukihiro Shimizu
- Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA 92037
| | - Luca G. Guidotti
- Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA 92037
| | - Patricia Fowler
- Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA 92037
| | - Francis V. Chisari
- Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA 92037
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131
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Nakamoto Y, Guidotti LG, Kuhlen CV, Fowler P, Chisari FV. Immune pathogenesis of hepatocellular carcinoma. J Exp Med 1998; 188:341-50. [PMID: 9670046 PMCID: PMC2212453 DOI: 10.1084/jem.188.2.341] [Citation(s) in RCA: 286] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/1998] [Revised: 04/23/1998] [Indexed: 12/13/2022] Open
Abstract
Hepatocellular carcinoma (HCC) is a common complication of chronic hepatitis B virus (HBV) infection. The pathogenetic mechanisms potentially responsible for HCC during chronic HBV infection are not well defined. This study demonstrates that chronic immune-mediated liver cell injury triggers the development of HCC in the absence of viral transactivation, insertional mutagenesis, and genotoxic chemicals. These results strongly suggest that the immune response to HBV is both necessary and sufficient to cause liver cancer during chronic HBV infection, and that all other procarcinogenic events associated with HCC are probably dependent on this process.
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Affiliation(s)
- Y Nakamoto
- Division of Experimental Pathology, Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, California 92037, USA
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132
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Gazina EV, Lin B, Gallina A, Milanesi G, Anderson DA. Intracellular retention of duck hepatitis B virus large surface protein is independent of preS topology. Virology 1998; 242:266-78. [PMID: 9514970 DOI: 10.1006/viro.1997.9015] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The mechanism of intracellular retention for the large surface protein (L) of duck hepatitis B virus (DHBV) was analyzed by examination of the transmembrane topologies and secretory properties of a collection of DHBV L mutants and compared with that of human hepatitis B virus (HBV) L. Our results demonstrate that, in contrast to its HBV counterpart, intracellular retention of DHBV L does not depend on the cytosolic disposition of its preS domain. L mutants with either cytosolic or lumenal preS were mostly retained in the absence of the small surface protein (S), whereas coexpression with S resulted in efficient secretion of both topological forms. Coexpression of the wild-type DHBV L with S resulted in efficient incorporation of L into secreted S + L particles, whereas HBV L was partially excluded from secreted particles under the same conditions. We propose that HBV provides L retention even in the presence of an excess of S, by exclusion of molecules with cytosolic preS domains from secreted particles at the stage of their assembly. DHBV lacks such a retention mechanism due to the absence of topological selection in particulate assembly.
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Affiliation(s)
- E V Gazina
- Macfarlane Burnet Centre for Medical Research, Fairfield, Victoria, Australia
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133
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Bruns M, Miska S, Chassot S, Will H. Enhancement of hepatitis B virus infection by noninfectious subviral particles. J Virol 1998; 72:1462-8. [PMID: 9445049 PMCID: PMC124627 DOI: 10.1128/jvi.72.2.1462-1468.1998] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The biological function of the huge excess of subviral particles over virions in hepatitis B virus infections is unknown. Using the duck hepatitis B virus as a model, we unexpectedly found that subviral particles strongly enhance intracellular viral replication and gene expression. This effect is dependent on the multiplicity of infection, the ratio of virions over subviral particles, and the time point of addition of subviral particles. Most importantly, we show that the pre-S protein of the subviral particles triggers enhancement and requires the presence of the binding regions for putative cell-encoded virus receptor proteins. These data suggest that enhancement is due either to the recently described transactivation function of the pre-S protein or to signalling pathways which become activated upon binding of subviral particles to cellular receptors. The findings are of clinical importance, since they imply that infectivity of sera containing hepadnaviruses depends not only on the amount of infectious virions but also decisively on the number of particles devoid of nucleic acids. A similarly dramatic enhancing effect of noninfectious particles in other virus infections is well conceivable.
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Affiliation(s)
- M Bruns
- Heinrich-Pette-Institut für Experimentelle Virologie und Immunologie an der Universität Hamburg, Germany.
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134
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Triyatni M, Jilbert AR, Qiao M, Miller DS, Burrell CJ. Protective efficacy of DNA vaccines against duck hepatitis B virus infection. J Virol 1998; 72:84-94. [PMID: 9420203 PMCID: PMC109352 DOI: 10.1128/jvi.72.1.84-94.1998] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The efficacy of DNA vaccines encoding the duck hepatitis B virus (DHBV) pre-S/S and S proteins were tested in Pekin ducks. Plasmid pcDNA I/Amp DNA containing the DHBV pre-S/S or S genes was injected intramuscularly three times, at 3-week intervals. All pre-S/S and S-vaccinated ducks developed total anti-DHBs and specific anti-S antibodies with similar titers reaching 1/10,000 to 1/50,000 and 1/2,500 to 1/4,000, respectively, after the third vaccination. However, following virus challenge, significant differences in the rate of virus removal from the bloodstream and the presence of virus replication in the liver were found between the groups. In three of four S-vaccinated ducks, 90% of the inoculum was removed between <5 and 15 min postchallenge (p.c.) and no virus replication was detected in the liver at 4 days p.c. In contrast, in all four pre-S/S-vaccinated ducks, 90% of the inoculum was removed between 60 and 90 min p.c. and DHBsAg was detected in 10 to 40% of hepatocytes. Anti-S serum abolished virus infectivity when preincubated with DHBV before inoculation into 1-day-old ducklings and primary duck hepatocyte cultures, while anti-pre-S/S serum showed very limited capacity to neutralize virus infectivity in these two systems. Thus, although both DNA vaccines induced high titers of anti-DHBs antibodies, anti-S antibodies induced by the S-DNA construct were highly effective in neutralizing virus infectivity while similar levels of anti-S induced by the pre-S/S-DNA construct conferred only very limited protection. This phenomenon requires further clarification, particularly in light of the development of newer HBV vaccines containing pre-S proteins and a possible discrepancy between anti-HBs titers and protective efficacy.
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Affiliation(s)
- M Triyatni
- Department of Microbiology and Immunology, University of Adelaide, South Australia.
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135
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Abstract
Hepatitis B virus small surface protein is synthesized as a transmembrane protein of the rough endoplasmic reticulum (RER) and then buds into the lumen in the form of subviral particles that are secreted. The closely related large surface protein is also targeted to the RER but is retained in a pre-Golgi compartment and cannot be secreted. It has been assumed that the large surface protein remains as a transmembrane RER protein and hence cannot form particles, possibly because of binding to a host factor on the cytosolic face of the RER membranes. We have reexamined this question and found the following results. (i) The retained large surface protein is associated not with RER but, rather, with a more distal compartment. (ii) Electron microscopy reveals intravesicular 20-nm particles, similar to those formed by the small surface protein. (iii) The large surface protein colocalizes with and binds to calnexin, an ER chaperone protein. Therefore, our results indicate that the large surface protein is capable of budding and forming particles, and hence its intracellular retention cannot be attributed to a cytosolic factor. We interpret the data as evidence that the large surface protein is retained by virtue of interacting with calnexin, a component of what is considered the quality control mechanism of the ER.
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Affiliation(s)
- Z Xu
- Department of Pathology, University of California, Veterans Affairs Medical Center, San Francisco, USA
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136
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Anastassiadis C, Rottmann O, Hörmansdorfer S, Pirchner F. Expression of the hepatitis B surface antigen (HbsAg) under the control of mMT-I promoter in transgenic mice can be induced by zinc sulphate, dexamethasone and lipopolysaccharide. J Anim Breed Genet 1997; 114:225-30. [PMID: 21395818 DOI: 10.1111/j.1439-0388.1997.tb00508.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
SUMMARY Metallothionein genes can be induced in vivo by heavy metals, glucocorticoids, and toxins. In all transgenic mice carrying the MT-I promoter, that have been reported so far, induction by glucocorticoids failed. This study reports two mouse lines, transgenic for the murine MT-I-HBV (hepatitis B virus; map position site: 30-1986) construct, which secrete the viral surface antigen (HBsAg) in their serum. In both lines, males produce more HBsAg than females, and in all cases the MT-I promoter can be induced by dexamethasone, lipopolysaccharide (LPS), and heavy metals. A glucocorticoid-responsive element, which is situated in the HBV fragment used, can explain the dexamethasone induction of the MT-I promoter. ZUSAMMENFASSUNG: Expression des Hepatitis B oberflächen Antigens (HBsAg) unter Kontrolle des mMT-I Promoters kann in transgenen Mäusen durch Zink Sulfat, Dexamethason und Lipopolysacchariden induziert werden Metallothioneingene werden in vivo durch Schwermetalle, Glucocorticoide und Toxine induziert. Soweit bisher bekannt, konnte jedoch in transgenen Mäusen mit dem MT-I-Promotor keine Expression durch Glucocorticioide beobachtet werden. Wir berichten hier von zwei transgenen Mäuselinien mit dem murinen MT-I-Promotor, der das Oberflächenantigen des Hepatitis B Virus (HbsAg, map position site 30-1986) exprimierte. In beiden Linien produzierten die männlichen Tiere mehr HBsAg im Blutserum als die weiblichen. Ohne Ausnahme reagierte der MT-I-Promotor bei Applikation von Dexamethason, Lipopolysaccharid (LPS) und Schwermetall. Ein Glucocorticoid-responsives Element in den HBV-Sequenzen kann die Induktion des MT-I-Promotors erklären.
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Affiliation(s)
- C Anastassiadis
- Institut für Tierwissenschaften der Technischen Universität München-Weihenstephan, Freising, Germany
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137
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Aragona E, Burk RD, Ott M, Shafritz DA, Gupta S. Cell type-specific mechanisms regulate hepatitis B virus transgene expression in liver and other organs. J Pathol 1996; 180:441-9. [PMID: 9014867 DOI: 10.1002/(sici)1096-9896(199612)180:4<441::aid-path713>3.0.co;2-c] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Intracellular expression of hepatitis B virus (HBV) was analysed in transgenic HBV mouse lines designated G7 and G26, the former lacking hepatitis B surface antigen (HBsAg) promoters. HBsAg mRNA expression was greater in the G26 line than in the G7 line, although in situ hybridization showed a qualitatively similar expression pattern in specific cell types. HBsAg mRNA was most abundant in hepatocytes, followed in magnitude by proximal renal tubular epithelial cells, pancreatic acinar cells, and epithelial cells of the gastric, small intestinal, and bronchiolar mucosae. In biliary epithelial cells, brain, spleen, large intestine, testis, heart, and skeletal muscle, HBsAg mRNA was undetectable. In cell transfection assays, the HBV enhancer/preS1 promoter efficiently expressed a luciferase reporter with appropriate upregulation by HNF-3 alpha and C/EBP alpha transcription factors in hepatocyte-derived cells but not in non-parenchymal epithelial liver cells or fibroblasts. These results suggest that cell-type specificity of HBV expression is regulated by interactions between viral elements and cellular transactivators. Variable expression of G7 and G26 HBV transgenes in epithelial cells combined with differences in transgene expression in similar sets of cells suggests at least two levels of regulation: one directing cell specificity of HBV expression and the other governing quantitative expression of HBV mRNA.
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Affiliation(s)
- E Aragona
- Department of Medicine, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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138
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Guidotti LG, Matzke B, Pasquinelli C, Shoenberger JM, Rogler CE, Chisari FV. The hepatitis B virus (HBV) precore protein inhibits HBV replication in transgenic mice. J Virol 1996; 70:7056-61. [PMID: 8794350 PMCID: PMC190756 DOI: 10.1128/jvi.70.10.7056-7061.1996] [Citation(s) in RCA: 96] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
In this study, we examined the ability of the hepatitis B virus (HBV) precore, envelope, and X gene products to modulate HBV replication in the livers of transgenic mice that replicate the virus. Hepatic HBV replication was not affected by overexpression of the envelope or X gene products when these animals were crossed with transgenic mice that express the corresponding viral genes in the hepatocyte. Overexpression of the precore protein, however, eliminated nucleocapsid particles from the cytoplasm of the hepatocytes and abolished HBV replication without affecting the hepatic steady-state content of pregenomic HBV RNA. These observations suggest that the precore protein can exert a dominant negative effect on HBV replication, presumably at the level of nucleocapsid particle maturation or stability, suggesting an important role for this enigmatic viral protein in the HBV life cycle.
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Affiliation(s)
- L G Guidotti
- Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, California 92037, USA
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139
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140
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Schirmacher P, Schauss D, Dienes HP. Intracellular accumulation of incompletely processed transforming growth factor-alpha polypeptides in ground glass hepatocytes of chronic hepatitis B virus infection. J Hepatol 1996; 24:547-54. [PMID: 8773909 DOI: 10.1016/s0168-8278(96)80139-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
BACKGROUND Transforming growth factor-alpha is an intracellularly processed and secreted polypeptide that induces a proliferative response in epithelial target cells and represents a potential regulatory factor in embryonic development, liver regeneration, and also hepatocarcinogenesis. We have observed focal transforming growth factor-alpha expression in liver tissues with chronic hepatitis B virus infection. METHODS To further elucidate the nature of this focal transforming growth factor-alpha accumulation we have analyzed overall 23 different liver tissues with chronic hepatitis B virus and hepatitis C virus infection as well as normal liver tissues by immunohistology, ELISA, and Western immunoblot with and without immunoprecipitation. RESULTS By immunohistology transforming growth factor-alpha polypeptides showed focal subcellular accumulation in ground glass hepatocytes, the histological hallmark of chronic hepatitis B virus infection, in co-localization with HBV-preS1 antigen. By ELISA and Western immunoblot increased tissue concentrations of transforming growth factor-alpha were demonstrated in chronically hepatitis B virus-infected liver tissues with ground glass hepatocytes, especially a 15-kD polypeptide, most likely representing an incompletely processed transforming growth factor-alpha polypeptide. Transforming growth factor-alpha retention in ground glass hepatocytes is not a general unspecific effect, since it was not observed for several other secretory liver proteins. Accumulated transforming growth factor-alpha in ground glass hepatocytes does not co-localize with Epidermal Growth Factor Receptor expression. CONCLUSION Thus evidence is presented that a principally secreted (viral) polypeptide (HBV-preS1) can interfere with the secretion and processing of a second (cellular) protein (transforming growth factor-alpha). Accumulation of transforming growth factor-alpha may result from alteration of the endoplasmic reticulum due to storage of hepatitis B virus surface antigen particles. No evidence was found for transforming growth factor-alpha in ground glass hepatocytes to intracellularly interact with the Epidermal Growth Factor Receptor.
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Affiliation(s)
- P Schirmacher
- Institute of Pathology, University of Mainz, Germany
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141
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Chisari FV. Hepatitis B virus transgenic mice: models of viral immunobiology and pathogenesis. Curr Top Microbiol Immunol 1996; 206:149-73. [PMID: 8608715 DOI: 10.1007/978-3-642-85208-4_9] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
It should be apparent from the foregoing that the transgenic mouse model system has contributed substantially to our understanding of many aspects of HBV biology, immunobiology and pathogenesis in the past several years. We have learned that HBV can replicate within the mouse hepatocyte, as well as other mouse cell types, suggesting that there are probably no strong tissue or species specific constraints to viral replication once the viral genome enters the cell. However, the failure thus far to detect viral cccDNA in the hepatocyte nucleus in several independently derived transgenic lineages suggests that other, currently undefined, constraints on host range and tissue specificity may also be operative. Thanks to the transgenic mouse model we now understand the pathophysiological basis for HBsAg filament formation and ground glass cell production, and we have learned that at least this viral gene product can be toxic for the hepatocyte, first by compromising its ability to survive the hepatocytopathic effects of LPS and IFN alpha and eventually by causing it to die in the absence of any obvious exogenous stimulus. In recent studies, it has been shown that preformed nucleocapsid particles do not cross the nuclear membrane in either direction at least in the mouse hepatocyte. If this is confirmed, it will have two important implications: first, that nucleocapsid disassembly must occur in the cytoplasm before the nascent viral genome can enter the nucleus; second, that the intranuclear nucleocapsid particles are empty, and therefore serve no currently defined purpose in the viral life cycle. This should stimulate new interest in the analysis of the function of these particles that are a prominent feature of mammalian hepadnavirus infection. The transgenic mouse model has also established definitively that HBV-induced liver disease has an immunological basis, and that the class I-restricted CTL response plays a central role in this process. Additionally, the mouse studies have taught us that when the CTL recognize their target antigen on the hepatocytes they cause them to undergo apoptosis, forming the acidophilic, Councilman bodies that are characteristic of viral hepatitis. Further, we have learned that although the CTL initiate the liver disease, they actually contribute more to disease severity indirectly by recruiting antigen nonspecific effector cells into the liver than by directly killing the hepatocytes themselves. In addition, by releasing IFN gamma when they recognize antigen, the CTL can destroy enough of the liver to cause fulminant hepatitis in mice whose hepatocytes overproduce the large envelope protein and are hypersensitive to the cytopathic effects of this cytokine. We have also learned that the CTL are unable to recognize HBV-positive parenchymal cells outside of the liver, apparently because they cannot traverse the microvascular barriers that exist at most extrahepatic tissue sites. This important new discovery may permit the virus to survive a vigorous CTL response and contribute not only to the maintenance of memory T cells following acute hepatitis but also to serve as a reservoir to reseed the liver in patients with chronic hepatitis. The transgenic mouse model has also revealed that activated CTL and the cytokines they secrete can down-regulate HBV gene expression, and possibly even control viral replication, by noncytotoxic intracellular inactivation mechanisms involving the degradation of viral RNA and, perhaps, the degradation of viral nucleocapsids and replicative DNA intermediates without killing the cell. If HBV replication is indeed interrupted by this previously unsuspected activity, it could contribute substantially to viral clearance during acute infection when the immune response to HBV is vigorous. Alternatively, it could also contribute to viral persistence, by only partially down-regulating the virus during chronic infection when the immune response is weak.
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Affiliation(s)
- F V Chisari
- Department of Molecular and Experimental Medicine, Scripps Research Institute, La Jolla, CA 92037, USA
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142
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Guidotti LG, Ishikawa T, Hobbs MV, Matzke B, Schreiber R, Chisari FV. Intracellular inactivation of the hepatitis B virus by cytotoxic T lymphocytes. Immunity 1996; 4:25-36. [PMID: 8574849 DOI: 10.1016/s1074-7613(00)80295-2] [Citation(s) in RCA: 820] [Impact Index Per Article: 29.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
It is widely believed that viral clearance is mediated principally by the destruction of infected cells by CTLs. In this report, we use a transgenic mouse model of HBV replication to demonstrate that this assumption may not be true for all viruses. We find that adoptively transferred virus-specific CTLs can abolish HBV gene expression and replication in the liver without killing the hepatocytes. This antiviral function is mediated by IFN gamma and TNF alpha secreted by the CTL or by the antigen-nonspecific macrophages and T cells that they activate following antigen recognition. These cytokines activate two independent virocidal pathways: the first pathway eliminates HBV nucleocapsid particles and their cargo of replicating viral genomes, while the second pathway destabilizes the viral RNA. Intracellular viral inactivation mechanisms such as these could greatly amplify the protective effects of the immune response, while failure of such mechanisms could lead to viral persistence or to the death of the host.
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Affiliation(s)
- L G Guidotti
- Department of Molecular and Experimental Medicine, Scripps Research Institute, La Jolla, California 92037, USA
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143
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Xu Z, Yen TS. Intracellular retention of surface protein by a hepatitis B virus mutant that releases virion particles. J Virol 1996; 70:133-40. [PMID: 8523517 PMCID: PMC189797 DOI: 10.1128/jvi.70.1.133-140.1996] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
In the course of chronic infection, hepatitis B virus mutants can sometimes be found circulating in the serum as the predominant species. One class of such mutants contains in-frame deletions in the S promoter region. By transfecting hepatoma cells with wild-type or mutant viral genomic DNA, we have shown that one such mutant gives rise to extremely small amounts of S transcripts, as expected, and therefore expresses very little of the middle and small surface (viral envelope) proteins that are translated from these transcripts. In addition, this mutant gives rise to greater-than-wild-type levels of the preS1 transcripts, which are translated into the large surface protein. Because the large surface protein, unlike the other forms of surface protein, is incompetent for secretion, cells transfected with the mutant viral DNA contain large amounts of 20-nm particles within dilated perinuclear vesicles. Therefore, this and similar S promoter mutants may be one contributing factor in the pathogenesis of ground-glass cells, which are hepatocytes containing nonsecretable viral surface proteins within dilated vesicles and are commonly found during chronic hepatitis B. Interestingly, DNA-containing virion particles are secreted into the medium by cells transfected with the mutant DNA, in amounts that are slightly larger than those secreted from wild-type-transfected cells, apparently because the amount of large surface protein is insufficient to block virion secretion. This finding may explain how such mutants can become the predominant circulating species in the serum, especially if there are selection pressures against the wild-type virus.
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Affiliation(s)
- Z Xu
- Department of Pathology, University of California School of Medicine, San Francisco, USA
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144
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Caselmann WH. Trans-activation of cellular genes by hepatitis B virus proteins: a possible mechanism of hepatocarcinogenesis. Adv Virus Res 1996; 47:253-302. [PMID: 8895834 DOI: 10.1016/s0065-3527(08)60737-x] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- W H Caselmann
- Department of Medicine II, Klinikum Grosshadern, Ludwig-Maximilians-Universität, Munich, Germany
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145
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Bruss V, Vieluf K. Functions of the internal pre-S domain of the large surface protein in hepatitis B virus particle morphogenesis. J Virol 1995; 69:6652-7. [PMID: 7474074 PMCID: PMC189574 DOI: 10.1128/jvi.69.11.6652-6657.1995] [Citation(s) in RCA: 92] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The large hepatitis B virus (HBV) surface protein (L) forms two isomers which display their N-terminal pre-S domain at the internal and external side of the viral envelope, respectively. The external pre-S domain has been implicated in binding to a virus receptor. To investigate functions of the internal pre-S domain, a secretion signal sequence was fused to the N terminus of L (sigL), causing exclusive expression of external pre-S domains. A fusion construct with a nonfunctional signal (s25L), which corresponds in its primary sequence to sigL cleaved by signal peptidase, was used as a control. SigL was N glycosylated in transfected COS cells at both potential sites in pre-S in contrast to s25L or wild-type L, confirming the expected transmembrane topologies of sigL and s25L. Phenotypic characterization revealed the following points. (i) SigL lost the inhibitory effect of L or s25L on secretion of subviral hepatitis B surface antigen particles, suggesting that the retention signal mapped to the N terminus of L is recognized in the cytosol and not in the lumen of the endoplasmic reticulum. (ii) SigL was secreted into the culture medium even in the absence of the major HBV surface protein (S), while release of an L mutant lacking the retention signal was still dependent on S coexpression. (iii) s25L but not sigL could complement an L-negative HBV genome defective for virion secretion in cotransfections. This suggests that the cytosolic pre-S domain, like a matrix protein, is involved in the interaction of the viral envelope with preformed cytosolic nucleocapsids during virion assembly.
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Affiliation(s)
- V Bruss
- Department of Medical Microbiology, University of Göttingen, Germany
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146
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Abstract
Hepatitis B virus (HBV) transgenic mice whose hepatocytes replicate the virus at levels comparable to that in the infected livers of patients with chronic hepatitis have been produced, without any evidence of cytopathology. High-level viral gene expression was obtained in the liver and kidney tissues in three independent lineages. These animals were produced with a terminally redundant viral DNA construct (HBV 1.3) that starts just upstream of HBV enhancer I, extends completely around the circular viral genome, and ends just downstream of the unique polyadenylation site in HBV. In these animals, the viral mRNA is more abundant in centrilobular hepatocytes than elsewhere in the hepatic lobule. High-level viral DNA replication occurs inside viral nucleocapsid particles that preferentially form in the cytoplasm of these centrilobular hepatocytes, suggesting that an expression threshold must be reached for nucleocapsid assembly and viral replication to occur. Despite the restricted distribution of the viral replication machinery in centrilobular cytoplasmic nucleocapsids, nucleocapsid particles are detectable in the vast majority of hepatocyte nuclei throughout the hepatic lobule. The intranuclear nucleocapsid particles are empty, however, suggesting that viral nucleocapsid particle assembly occurs independently in the nucleus and the cytoplasm of the hepatocyte and implying that cytoplasmic nucleocapsid particles do not transport the viral genome across the nuclear membrane into the nucleus during the viral life cycle. This model creates the opportunity to examine the influence of viral and host factors on HBV pathogenesis and replication and to assess the antiviral potential of pharmacological agents and physiological processes, including the immune response.
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Affiliation(s)
- L G Guidotti
- Department of Molecular and Experimental Medicine, Scripps Research Institute, La Jolla, California 92037, USA
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147
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Chisari FV, Ferrari C. Hepatitis B virus immunopathology. SPRINGER SEMINARS IN IMMUNOPATHOLOGY 1995; 17:261-81. [PMID: 8571172 DOI: 10.1007/bf00196169] [Citation(s) in RCA: 94] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Approximately 5% of the world population is infected by the hepatitis B virus (HBV) which causes a necroinflammatory liver disease of variable duration and severity. Chronically infected patients with active liver disease carry a high risk of developing cirrhosis and hepatocellular carcinoma. The immune response to HBV-encoded antigens is responsible both for viral clearance and for disease pathogenesis during this infection. While the humoral antibody response to viral envelope antigens contributes to the clearance of circulating virus particles, the cellular immune response to the envelope, nucleocapsid and polymerase antigens eliminates infected cells. The class I- and class II-restricted T cell responses to the virus are vigorous, polyclonal and multispecific in acutely infected patients who successfully clear the virus, and they are relatively weak and more narrowly focussed in chronically infected patients who do not. The pathogenetic and antiviral potential of the cytotoxic T lymphocyte (CTL) response to HBV have been demonstrated by the induction of a severe necroinflammatory liver disease following the adoptive transfer of HBV surface antigen-specific CTL into HBV transgenic mice, and by the noncytolytic suppression of viral gene expression and replication in the same animals by a post-transcriptional mechanism mediated by interferon-gamma, tumor necrosis factor-alpha and interleukin-2. The dominant cause of viral persistence during HBV infection is the development of a weak antiviral immune response to the viral antigens. While neonatal tolerance probably plays an important role in viral persistence in patients infected at birth, the basis for poor responsiveness in adult onset infection is not well understood and requires further analysis. Viral evasion by epitope inactivation and T cell receptor antagonism may contribute to the worsening of viral persistence in the setting of an ineffective immune response, as can the incomplete down-regulation of viral gene expression and the infection of immunologically privileged tissues. Chronic liver cell injury and the attendant inflammatory and regenerative responses create the mutagenic and mitogenic stimuli for the development of DNA damage that can cause hepatocellular carcinoma. Elucidation of the immunological and virological basis for HBV persistence may yield immunotherapeutic and antiviral strategies to terminate chronic HBV infection and reduce the risk of its life-threatening sequellae.
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Affiliation(s)
- F V Chisari
- Department of Molecular and Experimental Medicine, Scripps Research Institute, La Jolla, CA 92037, USA
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148
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Darabi A, Gross S, Watabe M, Malafa M, Watabe K. Differential gene expression in experimental hepatocellular carcinoma induced by woodchuck hepatitis B virus. Cancer Lett 1995; 95:153-9. [PMID: 7656224 DOI: 10.1016/0304-3835(95)03881-v] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Hepatitis B virus infection is closely linked to hepatocellular carcinoma (HCC), the pathological mechanism of hepatocarcinogenesis by this virus is not well understood. In order to gain further insight into the molecular mechanism of HCC, we constructed and screened a subtracted c-DNA library which was specific to HCC cells of a woodchuck infected with woodchuck hepatitis B virus. Among eight clones that were isolated based on their differential expressions, we determined nucleotide sequences of two genes whose expressions were most significantly stimulated in HCC. Our results indicate that these two genes appear to be woodchuck counterpart genes of hemopexin (HPX) and alpha-1 acid glycoprotein (AGP), suggesting that the expression of HPX and AGP genes are strongly augmented in tumor cells partly due to transcriptional regulation.
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Affiliation(s)
- A Darabi
- Department of Medical Microbiology and Immunology, School of Medicine, Southern Illinois University, Springfield 62702, USA
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149
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Strong, sustained hepatocellular proliferation precedes hepatocarcinogenesis in hepatitis B surface antigen transgenic mice. Hepatology 1995. [DOI: 10.1002/hep.1840210303] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 03/29/2023]
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150
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Anastassiadis K, Rottmann O, Weniger JH, Pirchner F. Integration, Transmission und Expression von Transgenen in Mäuselinien. J Anim Breed Genet 1995. [DOI: 10.1111/j.1439-0388.1995.tb00560.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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