Nitrite and nitrosamine synthesis by hepatocytes isolated from normal woodchucks (Marmota monax) and woodchucks chronically infected with woodchuck hepatitis virus.
(73/273)
Hepatocytes isolated from woodchucks (Marmota monax) were shown to produce nitrite in vitro from L-arginine after stimulation with lipopolysaccharide (LPS). Hepatocytes isolated from woodchucks that were chronic carriers of woodchuck hepatitis virus formed twice as much nitrite as hepatocytes from noninfected animals. Nitrite synthesis by hepatocytes was directly related to L-arginine and LPS concentrations in the tissue culture medium and reached a plateau at 0.5 mM L-arginine and 1.0 micrograms/ml LPS. LPS-stimulated hepatocytes nitrosated morpholine to form N-nitrosomorpholine in the presence of L-arginine at a physiological pH of 7.4. There was a 10-fold increase in N-nitrosomorpholine production when hepatocytes were stimulated with LPS compared to unstimulated hepatocytes under similar conditions when both nitrite and morpholine were directly added to the medium. NG-monomethyl-L-arginine, a selective inhibitor of nitric oxide synthase, inhibited formation of both nitrite and N-nitrosomorpholine. These results demonstrate that nitrosating agents are formed in hepatocytes via the L-arginine-nitric oxide pathway. This suggests that endogenous formation of carcinogenic N-nitroso compounds could influence the process of hepatocarcinogenesis in woodchucks with chronic woodchuck hepatitis virus infection. (+info)
Altered proteolysis and global gene expression in hepatitis B virus X transgenic mouse liver.
(74/273)
Hepatitis B virus X (HBX) is essential for the productive infection of hepatitis B virus (HBV) in vivo and has a pleiotropic effect on host cells. We have previously demonstrated that the proteasome complex is a cellular target of HBX, that HBX alters the proteolytic activity of proteasome in vitro, and that inhibition of proteasome leads to enhanced viral replication, suggesting that HBX and proteasome interaction plays a crucial role in the life cycle and pathogenesis of HBV. In the present study, we tested the effect of HBX on the proteasome activities in vivo in a transgenic mouse model in which HBX expression is developmentally regulated by the mouse major urinary promoter in the liver. In addition, microarray analysis was performed to examine the effect of HBX expression on the global gene expression profile of the liver. The results showed that the peptidase activities of the proteasome were reduced in the HBX transgenic mouse liver, whereas the activity of another cellular protease was elevated, suggesting a compensatory mechanism in protein degradation. In the microarray analysis, diverse genes were altered in the HBX mouse livers and the number of genes with significant changes increased progressively with age. Functional clustering showed that a number of genes involved in transcription and cell growth were significantly affected in the HBX mice, possibly accounting for the observed pleiotropic effect of HBX. In particular, insulin-like growth factor-binding protein 1 was down-regulated in the HBX mouse liver. The down-regulation was similarly observed during acute woodchuck hepatitis virus infection. Other changes including up-regulation of proteolysis-related genes may also contribute to the profound alterations of liver functions in HBV infection. (+info)
Replication properties of human adenovirus in vivo and in cultures of primary cells from different animal species.
(75/273)
Oncolytic adenoviruses have emerged as a promising approach for the treatment of tumors resistant to other treatment modalities. However, preclinical safety studies are hampered by the lack of a permissive nonhuman host. Screening of a panel of primary cell cultures from seven different animal species revealed that porcine cells support productive replication of human adenovirus type 5 (Ad5) nearly as efficiently as human A549 cells, while release of infectious virus by cells from other animal species tested was diminished by several orders of magnitude. Restriction of productive Ad5 replication in rodent and rabbit cells seems to act primarily at a postentry step. Replication efficiency of adenoviral vectors harboring different E1 deletions or mutations in porcine cells was similar to that in A549 cells. Side-by-side comparison of the viral load kinetics in blood of swine and mice injected with Ad5 or a replication-deficient adenoviral vector failed to provide clear evidence for virus replication in mice. In contrast, evidence suggests that adenovirus replication occurs in swine, since adenoviral late gene expression produced a 13.5-fold increase in viral load in an individual swine from day 3 to day 7 and 100-fold increase in viral DNA levels in the Ad5-infected swine compared to the animal receiving a replication-deficient adenovirus. Lung histology of Ad5-infected swine revealed a severe interstitial pneumonia. Although the results in swine are based on a small number of animals and need to be confirmed, our data strongly suggest that infection of swine with human adenovirus or oncolytic adenoviral vectors is a more appropriate animal model to study adenoviral pathogenicity or pharmacodynamic and toxicity profiles of adenoviral vectors than infection of mice. (+info)
Genetic changes in hepatitis delta virus from acutely and chronically infected woodchucks.
(76/273)
A woodchuck-derived hepatitis delta virus (HDV) inoculum was created by transfection of a genotype I HDV cDNA clone directly into the liver of a woodchuck that was chronically infected with woodchuck hepatitis virus. All woodchucks receiving this inoculum became positive for HDV RNA in serum, and 67% became chronically infected, similar to the rate of chronic HDV infection in humans. Analysis of HDV sequences obtained at 73 weeks postinfection indicated that changes had occurred at a rate of 0.5% per year; many of these modifications were consistent with editing by host RNA adenosine deaminase. The appearance of sequence changes, which were not evenly distributed on the genome, was correlated with the course of HDV infection. A limited number of modifications occurred in the consensus sequence of the viral genome that altered the sequence of the hepatitis delta antigen (HDAg). All chronically infected animals examined exhibited these changes 73 weeks following infection, but at earlier times, only one of the HDV carriers exhibited consensus sequence substitutions. On the other hand, sequence modifications in animals that eventually recovered from HDV infection were apparent after 27 weeks. The data are consistent with a model in which HDV sequence changes are selected by host immune responses. Chronic HDV infection in woodchucks may result from a delayed and weak immune response that is limited to a small number of epitopes on HDAg. (+info)
Immunogenic domains of hepatitis delta virus antigen: peptide mapping of epitopes recognized by human and woodchuck antibodies.
(77/273)
Hepatitis delta virus (HDV) is a defective RNA virus which is dependent on hepatitis B virus for essential helper functions. Only a single highly basic phosphoprotein, HDV antigen (HDAg), is expressed by the HDV genome during infection in humans. Antibody directed to HDAg is important in the diagnosis of HDV infection, and it is likely but not yet proven that the immune response to HDAg provides significant protection against subsequent exposures to HDV. In an effort to map the antigenic domains of HDAg, 209 overlapping hexapeptides, spanning the entire 214 amino acid residues of the protein, were synthesized on polyethylene pins and probed by enzyme-linked immunosorbent assay with sera containing high titers of anti-HD antibodies. Domains recognized by antibodies present in serum from human chronic carriers of this virus included residues 2 to 7, 63 to 74, 86 to 91, 94 to 100, 159 to 172, 174 to 195, and 197 to 207. Antibody from an acutely superinfected woodchuck recognized similar epitopes, as well as a domain spanning residues 121 to 128. Together, residues in these antigenic domains constitute 41% of the HDAg molecule. Oligopeptides 15 to 29 residues in length and representing epitopes of HDAg found to be dominant in humans (residues 2 to 17, 156 to 184, and 197 to 211) were synthesized in bulk and found to possess significant antigenic activity by microdilution enzyme-linked immunosorbent assay. The reactivity of peptide 197-211 with human sera confirms that the entire 214 amino acids of HDAg are expressed during infection in vivo. In addition, these results suggest that synthetic peptides may be useful reagents for development of new and improved diagnostic tests for HDV infection. (+info)
Cross-species hybridization of woodchuck hepatitis virus-induced hepatocellular carcinoma using human oligonucleotide microarrays.
(78/273)
AIM: To demonstrate the feasibility of using woodchuck samples on human microarrays, to provide insight into pathways involving positron emission tomography (PET) imaging tracers and to identify genes that could be potential molecular imaging targets for woodchuck hepatocellular carcinoma. METHODS: Labeled cRNA from woodchuck tissue samples were hybridized to Affymetrix U133 plus 2.0 GeneChips. Ten genes were selected for validation using quantitative RT-PCR and literature review was made. RESULTS: Testis enhanced gene transcript (BAX Inhibitor 1), alpha-fetoprotein, isocitrate dehydrogenase 3 (NAD+) beta, acetyl-CoA synthetase 2, carnitine palmitoyltransferase 2, and N-myc2 were up-regulated and spermidine/spermine N1-acetyltransferase was down-regulated in the woodchuck HCC. We also found previously published results supporting 8 of the 10 most up-regulated genes and all 10 of the 10 most down-regulated genes. CONCLUSION: Many of our microarray results were validated using RT-PCR or literature search. Hence, we believe that woodchuck HCC and non-cancerous liver samples can be used on human microarrays to yield meaningful results. (+info)
Alpha-fetoprotein in the woodchuck model of hepadnavirus infection and disease: normal physiological patterns and responses to woodchuck hepatitis virus infection and hepatocellular carcinoma.
(79/273)
Persistent infection of the eastern woodchuck (Marmota monax) with the woodchuck hepatitis virus (WHV) produces disease sequelae similar to those observed in humans with persistent hepatitis B virus infection, including hepatocellular carcinoma (HCC). To further characterize serological markers of HCC in the woodchuck, serum alpha-fetoprotein (AFP) was measured under normal physiological conditions and following infection with WHV. Serum AFP was elevated in association with WHV-induced hepatitis and HCC and was a useful indicator of hepatic responses in individual animals throughout the course of experimental WHV infection. The frequent occurrence of normal elevations in serum AFP during the fall and winter, however, limits the use of AFP as a marker for early detection of HCC. The present temporal studies of AFP responses in WHV-infected woodchucks have identified several stages of infection where virological and cellular interactions can be investigated at the molecular level. Studies of AFP in the woodchuck model should provide opportunities to further elucidate the physiological and immunological functions of AFP and to understand virus-host cell interactions during the course of experimental hepadnavirus infection leading to HCC. (+info)
The liver of woodchucks chronically infected with the woodchuck hepatitis virus contains foci of virus core antigen-negative hepatocytes with both altered and normal morphology.
(80/273)
The livers of woodchucks chronically infected with woodchuck hepatitis virus (WHV) contain foci of morphologically altered hepatocytes (FAH) with "basophilic", "amphophilic" and "clear cell" phenotypes, which are possibly pre-neoplastic in nature. Interestingly, most fail to express detectable levels of WHV proteins and nucleic acids. We studied sections of WHV-infected liver tissue to determine if all foci of hepatocytes that failed to express detectable levels of WHV, as assessed by immunoperoxidase staining for WHV core antigen, could be classified morphologically as FAH. We found that at least half of the foci of WHV core antigen-negative hepatocytes did not show clear morphological differences in either H&E or PAS (periodic acid Schiff) stained sections from surrounding hepatocytes, and were therefore not designated as FAH. In the second approach, we assayed core antigen-negative foci for the presence of fetuin B, a serum protein produced by normal hepatocytes, but not by neoplastic hepatocytes in hepatocellular carcinomas. Basophilic and amphophilic FAH had reduced levels of fetuin B compared to hepatocytes present in the surrounding liver; fetuin B staining was detected in clear cell FAH but the level could not be accurately assessed because of the displacement of fetuin B to the cell periphery by accumulated glycogen. The foci of morphologically normal WHV core antigen-negative hepatocytes had similar levels of fetuin B to that of the surrounding hepatocytes. The co-existence of at least four types of WHV core antigen-negative foci, including those with no obvious morphologic changes, raises the possibility that the different foci arise from distinct primary events. We hypothesize that a common event is loss of the ability to express WHV, allowing these hepatocytes to escape immune mediated cell death and to undergo clonal expansion to form distinct foci. (+info)