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Biomedical subjects

M A Feitelson

Publications and source records attributed to M A Feitelson.

At least 37 records · Page 2Linked to original sources
PubMed1995

X region deletion mutants associated with surface antigen-positive hepatitis B virus infections.

BACKGROUND/AIMS: The finding of antibodies against the polymerase of hepatitis B virus in renal dialysis patients before the incubation phase of infection implies underlying virus replication. Hence, the aim of the study was to test for virus during infection. METHODS: Viremia was assayed in virus-infected and control patients using the polymerase chain reaction and Southern blotting. RESULTS: Six months before the appearance of surface antigen, most patients had detectable core region, but few patients were X region positive. Three months after surface antigen appeared, most carriers had detectable core and X products. Three years after surface antigen appeared, 5 of 8 carriers with persistent hepatitis B e antigen and 1 of 8 carriers with corresponding antibody had these products. Cloning and sequencing showed deletions within the X/precore region of viral DNA. CONCLUSIONS: Infection with X region mutants precedes that of wild-type virus, and they reappear after wild-type virus is eliminated in carriers.

Base Sequence↗
PubMed1995

Functional inactivation but not structural mutation of p53 causes liver cancer.

Structural mutations in the p53 gene are seen in virtually every form of human cancer. To determine whether such mutations are important for initiating tumorigenesis, we have been studying hepatocellular carcinoma, in which most cases are associated with chronic hepatitis B virus infections. Using a transgenic mouse model where expression of a single HBV gene product, the HBx protein, induces progressive changes in the liver, we show that tumour development correlates precisely with p53 binding to HBx in the cytoplasm and complete blockage of p53 entry into the nucleus. Analysis of tumour cell DNA shows no evidence for p53 mutation, except in advanced tumours where a small proportion of cells may have acquired specific base substitutions. Our results suggest that genetic changes in p53 are late events which may contribute to tumour progression.

Animals↗
PubMed1995

X region deletion variants of hepatitis B virus in surface antigen-negative infections and non-A, non-B hepatitis.

The etiology of non-A, non-B hepatitis (NANBH) in renal dialysis patients was determined. Hepatitis C virus was present in many, but its appearance did not correlate with elevated alanine aminotransaminase. When sera from these patients were tested for antibodies against hepatitis B virus (HBV) X antigen and polymerase, 70% were positive. HBV infection was confirmed by polymerase chain reaction using several HBV-specific primer pairs. However, amplification with X region primers failed to yield products in many patients. Cloning and sequencing of these products demonstrated deletions within the X region. Hence, X-deletion variants of HBV are strongly associated with NANBH in renal dialysis patients.

Alanine Transaminase↗
PubMed1995

Precore and X region mutants in hepatitis B virus infections among renal dialysis patients.

Hepatitis B virus (HBV) variants containing mutations within the X and the precore regions of the viral genome were demonstrated by polymerase chain reaction (PCR) amplification and DNA sequencing in renal dialysis patients with different serological patterns of HBV infection. Among carriers, X region deletion mutants predominated in patients who lost hepatitis B e antigen (HBeAg), or developed anti-HBe, but not in persistently HBeAg-positive patients. The precore region remained wild type in all carriers whether or not they seroconverted from HBeAg to anti-HBe. The frequency of precore and X region mutants was greatest among non-carrier patients with viral antibodies as the only indication of infection and among patients with non-A, non-B hepatitis (NANBH), suggesting an inverse relationship between the presence of wild type HBV markers and the presence of HBV mutants. Furthermore, the detection of one but not the other mutation in many serum samples suggests that these mutations are independently selected for during infection. Finally, the absence of HBV DNA in 21 'uninfected' dialysis patients with normal transaminases and no viral serology, suggests that replication of these mutants is associated with hepatitis. These results have important implications for HBV screening and treatment, as well as for the pathogenesis of chronic infection.

Biomarkers↗
PubMed1994

Hepatitis B virus X protein inhibits p53 sequence-specific DNA binding, transcriptional activity, and association with transcription factor ERCC3.

Chronic active hepatitis caused by infection with hepatitis B virus, a DNA virus, is a major risk factor for human hepatocellular carcinoma. Since the oncogenicity of several DNA viruses is dependent on the interaction of their viral oncoproteins with cellular tumor-suppressor gene products, we investigated the interaction between hepatitis B virus X protein (HBX) and human wild-type p53 protein. HBX complexes with the wild-type p53 protein and inhibits its sequence-specific DNA binding in vitro. HBX expression also inhibits p53-mediated transcriptional activation in vivo and the in vitro association of p53 and ERCC3, a general transcription factor involved in nucleotide excision repair. Therefore, HBX may affect a wide range of p53 functions and contribute to the molecular pathogenesis of human hepatocellular carcinoma.

Cell Line↗
PubMed1993

The value of hepatitis B x antigen as a prognostic marker in the development of hepatocellular carcinoma.

Chronic infection with hepatitis-B virus (HBV) is associated with high risk for the development of hepatocellular carcinoma (HCC). Several studies have implicated that the X gene product(s) of HBV are important to the pathogenesis of HCC. This study tests the hypothesis that immunohistochemical detection of hepatitis B x antigen (HBxAg) is closely associated with HCC. The patterns of HBxAg were determined by staining in tumor and non-tumor liver sections from 30 Chinese patients with HBV-associated HCC, and the results were compared with other markers of infection. HBxAg was the most prevalent marker of HBV infection both in tumor and in non-tumor tissues of HCC patients, as compared with the hepatitis-B surface and core antigens. This pattern was observed among carriers as well as several patients who were HBsAG- in serum. The HBxAg staining results were validated by Southern blotting with an X-region probe and by Western blotting with anti-HBx. These results suggest that the persistence of HBxAg is important to the pathogenesis of early HCC and that HBxAg expression in the liver during chronic HBV infection may be an important prognostic marker for the development of HCC.

Adult↗
PubMed1993

Characteristics of woodchuck hepatitis X-antigen in the livers and sera from infected animals.

This study tests the hypothesis that woodchuck hepatitis virus encoded X-antigen expression correlates with viral replication, with hepatitis, or with both. Paired liver and serum samples from each of 55 infected woodchucks were used. Seven of 8 carriers with high levels of viral DNA in serum also had X-antigen in serum. In contrast, the frequency of X-antigen in serum was low among infected woodchucks that did not have viral surface antigen in the serum. Statistical analysis showed a significant relationship between X-antigen in serum and markers of viral replication. Woodchuck hepatitis X-antigen (WHxAg) expression in liver but not serum of carriers closely correlated with the presence of hepatitis. The finding of X-antigen in the liver of infected animals with hepatitis that cleared the virus surface antigen from serum also suggests that X-antigen is associated with ongoing hepatitis. Hence, the persistence of WHxAg in serum may signal continuing viral replication and, in liver, may contribute to the pathogenesis of chronic infection.

Animals↗
PubMed1993

Hepatitis B x antigen and p53 are associated in vitro and in liver tissues from patients with primary hepatocellular carcinoma.

To test the hypothesis that hepatitis B x antigen (HBxAg) binds to the tumor-suppressor protein p53, immunoprecipitation was carried out with monoclonal anti-x or monoclonal anti-p53 using radiolabeled HBxAg and p53 made by in vitro translation. The results showed that anti-p53 specifically immunoprecipitates HBxAg only in the presence of p53 and that anti-x specifically immunoprecipitates p53 only in the presence of HBxAg. to determine whether HBxAg binds p53 in vivo, immunoprecipitation and Western blot analysis of liver samples from 10 hepatitis B virus (HBV)-infected patients with primary hepatocellular carcinoma (PHC) were carried out. A protein band at 53,000 daltons that specifically immunoprecipitated with a monoclonal anti-x was identified as p53 by Western blotting with a monoclonal anti-p53. Anti-p53 specifically immunoprecipitated bands of 28,000, 17,000 and 13,000 daltons, which were identified as HBxAg polypeptides by Western blotting with anti-HBx. These findings suggest that HBxAg binds to p53 and that this association is important to the development of PHC.

Carcinoma, Hepatocellular↗
PubMed1992

Hepatitis B x antigen and polymerase antibodies in the serum of hepatitis B carriers with or without hepatitis delta virus infection. Effects of interferon treatment.

Previous work has shown that the hepatitis B x antigen (HBxAg) and antibodies directed against the polymerase of hepatitis B virus (anti-pol) are early markers of hepatitis B virus (HBV) replication in natural infections. The present study was carried out to test the hypothesis that the appearance of one or both of these markers signaled reactivation in chronic carriers with liver disease who were treated with alpha-interferon (IFN). The results show that HBV DNA decreased among the patients who responded to therapy, and that among these responders, neither HBxAg nor anti-pol became detectable in serum for 12 months after treatment, in contrast to controls. Hence, the loss of HBxAg and anti-pol correlate with decreased levels of HBV DNA in response to IFN therapy. However, different patterns of HBxAg and anti-pol were observed among alpha-IFN-treated HBV carrier patients who were also chronically infected with the hepatitis delta virus (HDV). The treatment of such patients often resulted in the loss of HDV RNA from serum and delta antigen from liver. Most of these patients had increased levels of HBV DNA in serum. HBxAg and/or anti-pol also became detectable in patients who lost markers of HDV, implying that the suppression of HDV by IFN is accompanied by the appearance of early markers of HBV reactivation in some of the treated patients.

Adult↗
PubMed1991

Hepatitis B x antigen in hepatitis B virus carrier patients with liver cancer.

Formalin-fixed, paraffin-embedded specimens from 110 cases of primary hepatocellular carcinoma were stained for hepatitis B x antigen (HBxAg), hepatitis B surface antigen (HBsAg), and hepatitis B core antigen (HBcAg). Eighty-four % of these patients were HBxAg positive in their tumor cells. Among the 110 cases studied, 80 had adjacent nontumorous tissue in the same block, and 65 of these nontumorous liver tissues stained positive for HBxAg (81%). HBsAg was positive in 19% of cases within tumor tissue and 61% in surrounding nontumorous tissue. HBcAg was positive in 11% of cases within tumor tissue and 26% in surrounding nontumorous tissue. These findings show that HBxAg is a common marker in the liver of patients with hepatitis B virus (HBV)-associated primary hepatocellular carcinoma and that it is closely associated with tumor cells in these individuals. In addition, the finding of HBxAg in the absence of detectable HBsAg and HBcAg in the liver tissues of many HBsAg carriers suggests that HBxAg could be expressed independent of HBV replication and implies that the synthesis of this antigen may be directed from integrated HBV DNA templates. The finding of HBxAg in the nucleus of hepatocytes from primary hepatocellular carcinoma patients with dysplasia, combined with the known trans-activating properties of HBxAg, implies that HBxAg plays one or more important roles in hepatocarcinogenesis. The finding of HBxAg in bile duct epithelium and cholangiocarcinoma tissues is compatible with the hypothesis that HBV may contribute to this other primary tumor type in the liver. Together, these results further implicate HBxAg in the pathogenesis of primary liver cancers.

Carcinoma, Hepatocellular↗
PubMed1991

HBxAg in the liver from carrier patients with chronic hepatitis and cirrhosis.

Formalin-fixed, paraffin-embedded specimens from 110 cases of chronic hepatitis and 108 cases of cirrhosis were stained for HBxAg by the avidin-biotin complex technique using specific antisera made against full-length HBxAg polypeptide or derived synthetic peptides. These tissues were also stained for the HBsAg and HBcAg by the peroxidase-anti-peroxidase method. Among patients with chronic hepatitis, 86% were HBsAg positive in liver cells, 60% were surface antigen positive and 32% were core antigen positive. Among patients with cirrhosis, 97% were HBsAg positive in liver cells, 72% were surface antigen positive and 17% were positive for core antigen. Staining specificity was demonstrated, in part, by using preimmune sera in the place of primary antibody, by blocking of the primary antibody with the appropriate antigen before assay and by testing uninfected liver controls. The persistence and high frequency of HBxAg in liver cells from patients with chronic liver disease suggest that it may play one or more important roles in the pathogenesis of chronic infection. It is possible that detection of HBxAg in the liver could be an additional new diagnostic marker for hepatitis B virus infection. However, the function(s) of HBxAg in the pathogenesis of the chronic liver disease, if any, remains to be explained.

Carrier State↗
PubMed1991

Polymerase-related polypeptides associated with woodchuck hepatitis core antigen (WHcAg) particles.

The woodchuck hepatitis virus (WHV) polymerase (pol)-encoded polypeptide(s), obtained from purified virus nucleocapsid particles, have been characterized by Western blotting. Peptide antibodies to amino-terminal (residues 32-45, WHV pol-6) and carboxy-terminal (residues 861-879, WHV pol-1) sequences were used, in addition to monoclonal antibodies made from purified woodchuck hepatitis core antigen (WHcAg) particles. One of the monoclonal antibodies, WC pol-11, specifically bound WHV pol-1. Both peptide and monoclonal anti-WHV pol-1 also bound a recombinant DNA-produced WHV polymerase polypeptide. These antibodies specifically detected WHcAg-associated polymerase polypeptides at 65,000 (p65) and 31,000 (p31) Da by Western blotting. These results support the conclusion that WHV pol-11 has anti-pol reactivity and that it binds the carboxyl-terminal sequences of the WHV polymerase. The finding that these reagents also specifically bind to corresponding sequences from the carboxy terminus of the hepatitis B virus polymerase suggests that these viral polymerases are cross reactive. Finally, anti-WHV pol-6 did not bind either WHcAg p65 or p31, suggesting that both of these polypeptides have different amino-terminal but the same carboxy-terminal sequences.

Amino Acid Sequence↗
PubMed1991

Characteristics of hepatitis B X antigen, antibodies to X antigen, and antibodies to the viral polymerase during hepatitis B virus infection.

The characteristics of hepatitis B virus (HBV) X antigen (HBxAg) and antibodies against the X antigen (anti-HBx) and the viral polymerase (anti-pol) were determined in 85 HBV-infected patients. HBxAg was detected in sera positive for HBV e antigen (HBeAg) and HBV DNA in patients with acute and chronic hepatitis, while anti-HBx appeared when markers of viral replication became undetectable. HBxAg was common in the liver among patients with chronic hepatitis independent of HBV replication markers but was closely correlated with elevated alanine aminotransferase, implying that HBxAg in liver may be important in the pathogenesis of chronic infection. Anti-pol was detected in many samples positive for HBeAg and HBV DNA and less often in serum samples without markers of HBV replication, suggesting that this marker could reflect ongoing viral replication in the liver, even though such markers were absent from sera.

Acute Disease↗
PubMed1990

Malignant transformation of immortalized transgenic hepatocytes after transfection with hepatitis B virus DNA.

Persistent infection by hepatitis B virus (HBV) is epidemiologically correlated with the prevalence of hepatocellular carcinoma, but its role in tumor development is not yet understood. To study the putative oncogenic potential of HBV, a non-malignant immortal mouse hepatocyte line FMH202 harboring metallothionein promoter-driven simian virus 40 large tumor antigen was transfected with HBV DNA. All stably transfected clones which replicated HBV displayed malignant growth characteristics in soft agar and were tumorigenic upon inoculation in nude mice. The nude mice tumors were histologically classified as differentiated or anaplastic hepatocellular carcinomas. As with human liver carcinomas, rearrangements of in vitro integrated HBV sequences were observed in the nude mouse tumors, and in tumor-derived cell lines. In one case, expression of viral core and surface antigens was blocked in the tumors, correlating with hypermethylation of the HBV genome. However, the expression of X gene was maintained in most tumors and tumor-derived cell lines. X protein was detected in nuclei by immune fluorescence and by immune blot. These results provide the first demonstration that HBV displays oncogenic potential in an experimental system. This system could be useful to functionally identify HBV genes which convey a tumorigenic phenotype.

Animals↗
PubMed1990

X antigen/antibody markers in hepadnavirus infections. Presence and significance of hepadnavirus X gene product(s) in serum.

The finding that X antigen is associated with hepatitis B core antigen particles and that serum hepatitis B e antigen derives from the cleavage of one or more core associated polypeptides raises the question as to whether core associated X antigen could be similarly generated and released into serum. To test this hypothesis, antisera raised to X antigen peptides were used to construct an enzyme-linked solid-phase immunoassay to detect X antigen in sera from patients infected with hepatitis B virus and from woodchucks infected with woodchuck hepatitis virus. X antigen was present in more than half of the individuals tested. There was a significant association between X antigen and markers of viral replication. Most individuals destined to become surface-antigen carriers had X antigen appearing before surface antigen, as did a smaller proportion of individuals transiently positive for surface antigen. A high frequency of X antigen was observed only in sera from human populations with a high frequency of other hepatitis B virus markers. These results suggest that X is a newly identified serum marker of viral replication that often appears before surface antigen in productive infections.

Animals↗
PubMed1990

X antigen/antibody markers in hepadnavirus infections. Antibodies to the X gene product(s).

Antibodies to the X antigen of hepatitis B virus and woodchuck hepatitis virus were assayed in serial sera from infected individuals and compared with other markers of infection. Antibody to the X antigen was found in 11 of 17 (65%) patients and 17 of 40 (42%) woodchucks that were surface-antigen positive. In comparison, this antibody was found in 5 of 14 (36%) patients and in none of 4 woodchucks that were surface-antigen negative. In 5 of 6 patients showing seroconversion from hepatitis B e antigen to antibody, antibody to X appeared at or near the time of seroconversion. In patients persistently positive for e antigen, X antibody often appeared when viral DNA became undetectable in the serum. In 14 of 17 (82%) woodchucks positive for antibody to X antigen, it also appeared near or after the time that viral DNA in serum disappeared. X antibodies were detected with great frequency only in populations with high frequencies of other hepatitis B virus markers. The results are consistent with the conclusion that antibody to X antigen is a marker of hepadnavirus infections that seems to be associated with a decrease in viral replication. Antibodies to the X antigen, then, may be a host response to the replication complex of the virus.

Animals↗
PubMed1990

Monoclonal antibodies raised to purified woodchuck hepatitis virus core antigen particles demonstrate X antigen reactivity.

Woodchuck hepatitis core antigen (WHcAg) particles purified from the liver of chronically infected animals were used for monoclonal antibody production. Most of the putative clones demonstrated anti-WHc specificity. However, the supernatants from several putative clones bound X antigen sequences from woodchuck hepatitis virus (WHV) and hepatitis B virus (HBV). One monoclonal antibody, designated WC9-85 (an IgM), specifically bound hepatitis B X antigen (HBxAg) residues spanning positions 115-131 (peptide 100). WC9-85 also specifically detected liver-derived WHcAg and duck hepatitis B core antigen (DHBcAg) particles in the same CsCl density gradient fractions as did specific anticore and cross-reactive polyclonal anti-x. WC9-85 did not bind to HBcAg particles made by recombinant DNA techniques, in which only the C-gene sequences are expressed, but did bind to liver-derived HBcAg in identical assays. A second monoclonal anti-x, WC8-62, had similar characteristics. Identification of the immunoreactive species in liver-derived core particles by Western blotting showed that WC9-85 bound the major DHBcAg polypeptide having an apparent molecular weight of 35,000 Da. WC9-85 also bound WHcAg-associated bands at approximately 37,000 and 27,000 Da, but little or no binding at the apparent molecular weight of the major WHcAg polypeptide (about 21,000 Da) was observed. These results are consistent with the conclusions that X determinants are associated with core particles purified from naturally infected livers, that such determinants are associated with the major DHBcAg polypeptide and at least two minor WHcAg-associated polypeptides, and that X reactivity is distinct from core and/or e reactivity in hepadnavirus core particles.

Animals↗