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F V Chisari

Publications and source records attributed to F V Chisari.

At least 145 records · Page 8Linked to original sources
PubMed1991

Synergy between hepatitis B virus expression and chemical hepatocarcinogens in transgenic mice.

Exposure of female hepatitis B virus transgenic mice of lineage 50-4, which display liver injury secondary to overexpression of the gene for the large envelope polypeptide of hepatitis B virus, to the hepatocarcinogens aflatoxin and diethylnitrosamine produced more rapid and extensive evidence of nodule formation and oval cell proliferation, as well as the development of adenomas and primary hepatocellular carcinomas, than was seen in transgenic mice not exposed to carcinogens. Adult mice are known to be resistant to the effects of aflatoxin or diethylnitrosamine, and the livers of carcinogen-treated nontransgenic littermate controls were essentially normal. By the time of sacrifice (15 mo), 20 adenomas and 2 primary hepatocellular carcinomas were found in 26 transgenic mice given aflatoxin and 8 adenomas and 2 primary hepatocellular carcinomas were seen in the 8 mice exposed to diethylnitrosamine, but no adenomas or carcinomas were identified in the 10 transgenic mice not exposed to carcinogens. These results suggest that the chronic liver damage and repair caused by overexpression of the hepatitis B virus large envelope polypeptide in the hepatocytes of the transgenic lineage 50-4 act synergistically with chemical hepatocarcinogens to produce neoplasia of the liver.

Adenoma↗
PubMed1991

Identification of immunodominant T cell epitopes of the hepatitis B virus nucleocapsid antigen.

Several lines of experimental evidence suggest that inclusion of core sequences in the hepatitis B vaccine may represent a feasible strategy to increase the efficacy of the vaccination. In order to identify immunodominant core epitopes, peripheral blood T cells purified from 23 patients with acute hepatitis B and different HLA haplotypes were tested with a panel of 18 short synthetic peptides (15 to 20 amino acids [AA]) covering the entire core region. All patients except one showed a strong T cell proliferative response to a single immunodominant 20 amino acid sequence located within the aminoterminal half of the core molecule. Two additional important sequences were also identified at the aminoterminal end and within the carboxyterminal half of the core molecule. These sequences were able to induce significant levels of T cell proliferation in 69 and 73% of the patients studied, respectively. T cell response to these epitopes was HLA class II restricted. The observations that (a) polyclonal T cell lines produced by PBMC stimulation with native HBcAg were specifically reactive with the relevant peptides and that (b) polyclonal T cell lines produced with synthetic peptides could be restimulated with native HBcAg, provide evidence that AA sequences contained within the synthetic peptides represent real products of the intracellular processing of the native core molecule. In conclusion, the identification of immunodominant T cell epitopes within the core molecule provides the molecular basis for the design of alternative and hopefully more immunogenic vaccines.

Amino Acid Sequence↗
PubMed1990

Hepatocarcinogenesis due to chronic liver cell injury in hepatitis B virus transgenic mice.

Fifty-nine transgenic mice from a lineage that overproduces the hepatitis B virus large envelope polypeptide and accumulates high intrahepatic concentrations of hepatitis B surface antigen were followed for evidence of liver disease throughout their 24-month life span. By 4 months of age all mice displayed biochemical and histological evidence of moderately severe chronic hepatitis which was followed sequentially by the development of regenerative nodules and oval cell hyperplasia (by 6 months), liver cell adenomas (by 8 months), and hepatocellular carcinomas (by 12 months of age). One hundred % of mice in this lineage developed hepatocellular carcinoma by 20 months of age, whereas no histopathological changes were observed in age- and sex-matched nontransgenic littermate controls over the same period of observation. These results indicate that overproduction of the hepatitis B virus large envelope polypeptide initiates a process characterized by liver cell injury, inflammation, and regenerative hyperplasia, which places large numbers of hepatocytes at risk for the development of transforming mutations, and inexorably progresses to hepatocellular carcinoma. We suggest that this is a general mechanism of hepatocarcinogenesis that may be operative in human hepatitis B virus infection and other necroinflammatory liver diseases as well.

Adenoma↗
PubMed1990

Immunobiology and pathogenesis of hepatocellular injury in hepatitis B virus transgenic mice.

The role of the immune response to hepatitis B virus (HBV)-encoded antigens in the pathogenesis of liver cell injury has not been defined because of the absence of appropriate experimental models. HBV envelope transgenic mice were used to show that HBV-encoded antigens are expressed at the hepatocyte surface in a form recognizable by major histocompatibility complex (MHC) class I-restricted, CD8+ cytotoxic T lymphocytes specific for a dominant T cell epitope within the major envelope polypeptide and by envelope-specific antibodies. Both interactions led to the death of the hepatocyte in vivo, providing direct evidence that hepatocellular injury in human HBV infection may also be immunologically mediated.

Amino Acid Sequence↗
PubMed1990

Overexpression of the multidrug resistance gene mdr3 in spontaneous and chemically induced mouse hepatocellular carcinomas.

Overexpression of a family of plasma membrane glycoproteins, known as P-glycoproteins, is commonly associated with multidrug resistance in animal cells. In rodents, three multidrug resistance (mdr or pgp) genes have been identified, but only two can confer the multidrug resistance phenotype upon transfection into animal cells. Using the RNase protection method, we demonstrated that the levels of three mdr gene transcripts differ among mouse tissues, confirming a previous report that the expression of these genes is tissue specific (J.M. Croop, M. Raymond, D. Huber, A. DeVault, R. J. Arceci, P. Gros, and D. E. Housman, Mol. Cell. Biol. 9:1346-1350, 1989). The levels of mdr transcripts were determined for mouse liver tumors spontaneously arising in both C3H/HeN and transgenic animals containing the hepatitis B virus envelope gene and for tumors induced by two different carcinogenic regimens in C57BL/6N and B6C3-F1 mice. The mdr3 gene was overexpressed in all 22 tumors tested. Our results demonstrate that overexpression of the mdr3 gene in mouse liver tumors does not require exposure of the animals to carcinogenic agents and suggest that its overexpression is associated with a general pathway of hepatic tumor development. The overexpression of the mdr3 gene, which is the homolog of human mdr1 gene, in hepatocellular carcinomas may be responsible for the poor response of these tumors to cancer chemotherapeutic agents.

1,2-Dimethylhydrazine↗
PubMed1990

Expression of HBV envelope and nucleocapsid proteins in human cells using vaccinia virus vectors.

We have analysed the expression of HBV envelope (large, middle, major) and nucleocapsid (core and precore) proteins in human skin fibroblasts and Epstein-Barr virus-transformed human B-cell lines infected with recombinant vaccinia virus vectors. The large envelope protein was not secreted and barely detectable in the cytosol, whereas middle s and major s where both water soluble and efficiently secreted in abundant quantities. The precore polypeptide was also secreted whereas the core protein was totally retained within a water soluble intracellular compartment, thus confirming the presence of a signal peptide within the precore region responsible for targeting the protein to the endoplasmic reticulum for excretion. It is anticipated that such recombinants will provide a useful tool for analysis of HBV-specific cytolytic T lymphocytes.

Capsid↗
PubMed1989

Molecular pathogenesis of hepatocellular carcinoma in hepatitis B virus transgenic mice.

Transgenic mice that overproduce the hepatitis B virus large envelope polypeptide and accumulate toxic quantities of hepatitis B surface antigen (HBsAg) within the hepatocyte develop severe, prolonged hepatocellular injury that initiates a programmed response within the liver, characterized by inflammation, regenerative hyperplasia, transcriptional deregulation, and aneuploidy. This response inexorably progresses to neoplasia. The incidence of hepatocellular carcinoma in this model corresponds to the frequency, severity, and age of onset of liver cell injury, which itself corresponds to the intrahepatic concentration of HBsAg and is influenced by genetic background and sex. Thus, the inappropriate expression of a single structural viral gene is sufficient to cause malignant transformation in this model. These results suggest that severe, prolonged cellular injury induces a preneoplastic proliferative response that fosters secondary genetic events that program the cell for unrestrained growth.

Aging↗
PubMed1989

Retroviral-mediated transfer and expression of hepatitis B e antigen in human primary skin fibroblasts and Epstein-Barr virus-transformed B lymphocytes.

Previously, an amphotropic retroviral expression system coding for the neomycin resistance gene was developed and used to synthesize hepatitis B e antigen (HBeAg) and hepatitis B core/e antigen (HBc/eAg) in transfected mouse NIH 3T3 fibroblasts (A. McLachlan et al., 1987, J. Virol. 61, 683-692). In the present study, these transfected cell lines were infected with a helper amphotropic murine leukemia virus resulting in the production of infectious recombinant retrovirus. The recombinant retrovirus was examined for its capacity to transmit resistance to the antibiotic, G418, and to express hepatitis B virus antigens in mouse NIH 3T3 fibroblasts, human primary skin fibroblasts, and Epstein-Barr virus (EBV)-transformed B lymphocytes. A mouse NIH 3T3 fibroblast clone was generated which produced recombinant retrovirus with the capacity to transmit HBeAg expression to these murine and human cell lines. In contrast, it was not possible to transmit HBc/eAg synthesis efficiently to these cell lines by recombinant retroviral infection. The difference between the efficiencies of transmission of HBeAg and HBc/eAg expression by recombinant retroviral-mediated infection was not predicted as the expression vector coding for HBc/eAg synthesis differs only by the deletion of approximately 90 nucleotides of HBV DNA sequence from the vector coding for HBeAg synthesis.

Adult↗
PubMed1989

Hepatitis B virus gene expression in transgenic mice.

In order to study aspects of the biology and pathogenesis of the hepatitis B virus (HBV), not readily approachable by existing tissue culture systems and animal models, several groups have introduced the HBV genome and subgenomic fragments into the germ line of transgenic mice. Substantial new information has been forthcoming from these studies in several areas including tissue-specific expression, hormonal regulation, sex influences, viral replication and disease pathogenesis. These developments are reviewed in the context of the genetic organization and functional properties of the virus and its gene products, and their implications with respect to HBV biology and pathogenesis are discussed.

Animals↗
PubMed1988

Functional modulation of hepatitis B core antigen-specific T lymphocytes by an autoreactive T cell clone.

Hepatitis B core (HBc)Ag-specific T cells present in the peripheral blood of a patient with chronic active hepatitis B were expanded by co-cultivation for 7 days with rHBcAg. After cloning at 1 cell/well in the presence of PHA and IL-2, five HBcAg-specific CD4+ cloned lines were obtained. All five lines proliferated and produced IL-2, IFN-gamma, and TNF in a dose-dependent fashion in response to HBcAg, but not to HBV envelope Ag. The cloned lines and derivative clones were HLA class II (DR1) restricted. All T cell clones were able to induce anti-HBc production by autologous B cells in response to HBcAg (helper effect). The proliferative response and the helper effect of the HBcAg-specific T cell lines and clones were augmented by co-cultivation with an autologous, autoreactive (HLA-DQ1 specific) T cell clone, even in the absence of HBcAg, and the autoreactive T cells directly stimulated anti-HBc secretion by autologous B cells, presumably due to the release of Ag-nonspecific factors. These findings define a model immunoregulatory circuit the physiologic significance of which remains to be determined.

Adult↗
PubMed1987

Evaluation of monoclonality of cell lines from sequential dilution assays.

The statistical framework necessary to analyze clonality following a two stage cloning procedure is described, and a simple table for determining the probability of monoclonality of derived cell colonies is presented. This statistical framework is designed for multistage cloning procedures and is an extension of the usual Poisson analytic technique.

Cell Line↗
PubMed1987

Intrahepatic, nucleocapsid antigen-specific T cells in chronic active hepatitis B.

Hepatitis B core antigen (HBcAg)-specific T cell lines were established from hepatic lymphomononuclear cells derived from five patients with chronic active hepatitis B. No hepatitis B virus envelope antigen-specific cell lines were established. Proliferation in response to recombinant and native HBcAg, but not to native hepatitis B surface antigen containing the pre-S(2) region, confirmed the specificity of the five T cell lines. All cell lines represented mixed populations of CD4+ and CD8+ T cells. The CD4+ subset provided antigen-specific help to autologous B cells with respect to anti-HBc production and to CD8+ cells with regard to HBcAg-induced proliferation and suppressor activity. The CD8+ subset contained suppressor cells that selectively inhibited the proliferative response of autologous HBcAg-specific CD4+ cells without inhibiting CD4+ cells of unrelated specificity (tetanus toxoid). Moreover, the CD8+ cells were also capable of suppressing HBcAg-stimulated antibody to HBcAg production without showing inhibition of total immunoglobulin production stimulated by pokeweed mitogen. The cytotoxic potential of the T cell lines was established in a lectin-dependent cytotoxicity system; natural killer cytotoxicity was completely absent. Our data suggest that the lesional T cells present at the site of hepatocellular injury in chronic active hepatitis B are primarily HBcAg-specific lymphocytes of the helper and suppressor/cytotoxic phenotypes and that both are functionally competent.

Antibody Formation↗
PubMed1987

Functional characterization of cloned intrahepatic, hepatitis B virus nucleoprotein-specific helper T cell lines.

We have previously reported the establishment and preliminary characterization of polyclonal hepatitis B virus (HBV) nucleoprotein (HBcAg)-specific CD4+ and CD8+ T cell lines derived from the hepatic lymphomononuclear cell infiltrate of several patients with chronic active hepatitis B. The isolated subsets from these lines were specifically activated by HBcAg and displayed antigen-specific help and suppression with respect to proliferation of the alternate subset. One of these lines was recently cloned by limiting dilution, and four HBcAg-specific CD3+ CD4+ CD8-DR+ T cell lines were produced that had a 95.3% likelihood of monoclonality. Antigenic specificity was confirmed by dose-dependent, HLA class II (DR)-restricted proliferation in response to recombinant and human serum-derived HBcAg and the lack of proliferation to HBV envelope antigens (HBsAg and pre-S(2)Ag). All cloned lines were interleukin 2 dependent, produced interferon-gamma in an antigen-specific manner, and provided antigen-specific help to autologous B cells with respect to anti-HBc production. We conclude that HBcAg-specific, HLA-class II restricted helper T cells capable of inducing antigen-specific functional responses by autologous B lymphocytes and T lymphocytes are present at the site of viral antigen synthesis and hepatocellular injury in HBV infection.

Adult↗