Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.7.7 (DNA polymerase)
17,007 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Two patients referred for cancer chemotherapy were found to be chronic, asymptomatic hepatitis B surface antigen (HBsAg) carriers. They had normal serum aminotransferase levels, but their sera were positive for HGsAg and antibody to hepatitis B e antigen. Both patients developed acute, icteric hepatitis within 3 months of starting cycled chemotherapy. In both cases, the disease seemed to be caused by a recurrence of type B hepatitis; it was accompanied by a marked increase in HBsAg titer and the appearance of hepatitis B virus DNA and DNA polymerase in the serum. One patient had a second episode of acute hepatitis after a second course of chemotherapy, but both patients ultimately recovered and became seronegative for HBsAg. Thus, it seems that cancer chemotherapeutic agents can reactivate type B hepatitis in asymptomatic HBsAg carriers. This reactivation is most likely due to an increase in hepatitis B virus synthesis followed by a rebound in host immune responses to hepatitis B virus infection when therapy is stopped. Such a phenomenon could have important implications for the therapy of chronic hepatitis B virus infection.
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PMID:Reactivation of chronic hepatitis B virus infection by cancer chemotherapy. 706 60

Twenty carriers of hepatitis B virus (HBV) were followed for two to seven years, and their histologic progression was correlated with HBV core-associated DNA polymerase (DNAP) activity as a marker of viral replication. Seventeen patients were divided into two groups according to their pattern of viral replication: group 1, consistently high levels of DNAP; group 2, low levels of DNAP. Chronic persistent hepatitis predominated in group 1; chronic active hepatitis predominated in group 2. The three remaining patients were consistently negative for DNAP. In two patients in group 2, prominent viral replication preceded a transient increase in transaminase levels, as in acute hepatitis. Although groups 1 and 2 were distinct in their patterns of viral replication, they did not differ significantly in histologic progression. Thus, viral replication is related, at least in part, to hepatic cell necrosis but does not correlate closely with progression to liver cirrhosis.
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PMID:Chronic hepatitis B: correlation between viral replication and clinical course. 728 10

The proliferative activity and ultrastructural characteristics of proliferating biliary epithelial cells were analysed immunohistocytochemically in 39 biopsied liver specimens from patients with acute viral hepatitis, chronic hepatitis and liver cirrhosis using a monoclonal antibody against DNA polymerase alpha (DNA-PA). In acute viral hepatitis with perivenular confluent necrosis, proliferation of typical bile ducts was found frequently in portal areas. In chronic aggressive hepatitis and cirrhosis, ductular proliferation of both typical and atypical forms was found in enlarged portal and periportal areas and in confluent necrotic areas. The number of proliferating biliary epithelial cells that stained positive for DNA-PA was small. There were very few positively stained cells in atypical bile ducts in confluent necrotic areas of cirrhosis. Atypical bile ducts seen in chronic aggressive hepatitis, cirrhosis and acute hepatitis with confluent necrosis were positively stained for both cytokeratins 8 and 19. In cirrhosis, the number of stained biliary epithelial cells in typical bile ducts was larger than the number of such cells in atypical bile ducts (P < 0.01). By electron microscopy, the cells positively stained for DNA-PA were mostly so-called clear cells with irregular nuclei containing coarse nucleoplasm, and a few small cells with scanty cytoplasm and few organelles.
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PMID:Analysis of proliferating biliary epithelial cells in human liver disease using a monoclonal antibody against DNA polymerase alpha. 768 20

There are several published case series of acute hepatitis A, with coverage ranging from epidemics to case reports, that provide information regarding the clinical course and outcome of hepatitis A in patients with underlying chronic hepatitis B virus (HBV) infection (1-12). Only a few reports have addressed the outcome of hepatitis A in patients with other chronic liver diseases (2, 13). Some, but not all, of these reports suggest that hepatitis A superimposed on chronic hepatitis B or other chronic liver diseases is associated with higher peak laboratory abnormalities, more severe disease, including fulminant hepatic failure, and a higher case fatality rate. In addition, analysis of HBsAg titer and serum markers of HBV replication, including HBeAg, HBV DNA, and DNA polymerase, reveals suppression of HBV replication. With the availability of hepatitis A virus (HAV) vaccine in many countries and its imminent approval for use in the United States, the issue of whether or not patients with chronic liver diseases, including chronic HBV infection, should be a target group for vaccination to prevent hepatitis A warrants consideration. The purpose of this review is to analyze the published literature addressing the clinical course and outcome of acute hepatitis A in patients with chronic HBV infection and other chronic liver diseases to determine if hepatitis A is more severe in these patients.
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PMID:Is hepatitis A more severe in patients with chronic hepatitis B and other chronic liver diseases? 784 85

A 47-year-old man with acute hepatitis B virus (HBV) infection who had been receiving immunosuppressants after renal transplantation developed progressive liver failure. During the clinical course (approximately 7 months), anti-HBc IgM antibody and HBV-DNA polymerase levels remained high, but the serum alanine aminotransferase (ALT) level was consistently less than 150 K.U. Histopathologic examination of the liver showed submassive hepatic necrosis without significant inflammation accompanied by marked fibrosis. Most hepatocytes showed strong nuclear expression of HBc antigen by immunohistochemical staining and electron microscopy revealed numerous intranuclear core-like particles. Hepatitis B virus infection in immunosuppressed individuals occasionally insidiously progresses, resulting in liver failure. The clinical course of such patients thus merits close scrutiny.
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PMID:Fatal acute hepatitis B virus infection while receiving immunosuppressants after renal transplantation. 828 32

The hepatitis B virus is a member of an unusual family of noncytopathogenic, hepatotropic DNA viruses--the hepadnaviruses. The complete virus comprises a lipoprotein coat, the hepatitis B surface antigen, enveloping a nucleocapsid core that contains a small, circular DNA molecule. Four open reading frames have been identified on the hepatitis B virus DNA genome. They encode seven proteins, including a hepatitis B virus DNA polymerase molecule with reverse transcriptase activity. The replication of the virus resembles that of retroviruses and occurs predominantly but not exclusively in hepatocytes. Virus variants involving genomic mutations have been identified. Testing for hepatitis B surface antigen permits detection of many but not all acutely infected patients. Diagnosis of acute infection rests on the identification of IgM antibodies to the hepatitis B core antigen. Antibody to hepatitis B surface antigen appears in serum during the convalescent phase of hepatitis B virus infection. It is the neutralizing, protective antibody largely responsible for immunity to reinfection. In persistent infection hepatitis B surface antigen is present, antibody to hepatitis B core antigen is predominantly an IgG antibody, antibody to hepatitis B surface antigen is not detectable or is present in very low titers and viral replication may be active. Persistent infection leads to an asymptomatic carrier state, chronic hepatitis, cirrhosis and hepatocellular carcinoma. No specific treatment exists for acute hepatitis B virus infection. Current data indicate that approximately 50% of adults who have chronic infection achieve virologic, biochemical and histologic remission from treatment with alpha-2b-interferon.
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PMID:Hepatitis B today: clinical and diagnostic overview. 832 12

Altered expression of asialoglycoprotein (ASGP) receptors on hepatocytes has been reported during hepatic neoplasia mostly in animal models. In this study, we examined immunohistochemically the distribution of the ASGP receptor in humans with various liver diseases, including ten cases of hepatocellular carcinoma (HCC). In livers of acute hepatitis, chronic hepatitis, cirrhosis and the non-cancerous tissues (mostly cirrhosis) adjacent to HCC, the receptor was present in its normal distribution, i.e. mostly along the sinusoidal margin and partly on the lateral surface of hepatocytes. In four of six well-differentiated HCCs, the receptor was also normally distributed on the plasma membrane; by immunoelectron microscopy, it was seen in the endoplasmic reticulum and in pits in the plasma membrane but not on bile canaliculus-like structures, suggesting that it was synthesized, transported, and integrated into the plasma membrane in a polar manner. In contrast, there was no surface expression of the ASGP receptor in the remaining six HCCs (two well-differentiated and four poorly differentiated). In two of the poorly differentiated HCCs, the receptor, although absent from the cell surface, was prominent in the endoplasmic reticulum, suggesting disturbed transport of the ASGP receptor to the cell surface. When we examined proliferative activity of HCCs by immunohistochemical labeling of DNA polymerase alpha, HCCs with high percentages (above 30%) of DNA polymerase alpha-positive cells had lost the cell-surface expression of the receptor. Thus, the expression of the ASGP receptor in human HCC appears to be closely related to differentiation and proliferative activity of the tumor cells.
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PMID:Distribution of asialoglycoprotein receptor in human hepatocellular carcinoma. 838 55

We report a case of simultaneous infection with hepatitis B virus (HBV) and human immunodeficiency virus type 1 (HIV-1) in a 26-year-old Japanese homosexual man. He was admitted to our hospital for acute hepatitis caused by HBV. At that time, HIV-1antibody (Ab) was not detected in his serum. After 6 months, he was readmitted to our hospital for further examination of his liver because of confined liver enzyme abnormalities. Anti-HIV- Ab was detected in his serum by both enzyme immunosorbent assay (EIA) and particle agglutination (PA). His serum HIV-1 RNA level was 50 x 10(4) copies/ml and serum levels of HBV DNA polymerase (DNA-P) and HBV DNA were 6535cpm and 3 plus (>1000 copies/ml). His clinical course and laboratory data suggested progression from acute to chronic hepatitis related to coinfection with HIV-1. The diagnosis was chronic active hepatitis caused by HBV as an opportunistic infection due to coinfection with HIV-1. We began highly active antiretroviral therapy (HAART) because interferon (IFN) therapy was ineffective. HAART was started at an initial dosage of 600 mg zidovudine (AZT), 300 mg lamivudine (3TC), and 2400 mg indinavir (IDV) daily. After 4 weeks, the serum level of HBV DNA-polymerase (p) had decreased markedly to 37cpm and that of HIV-1 RNA had decreased to below the sensitivity threshold, indicating considerable suppression of the replication of these viruses by the treatment. But HBV DNA remained at low levels. Although the incidence of HBV infection in patients with HIV-1 infection has been reported to be high in the United States and Europe, simultaneous HBV and HIV-1 infection leading to persistent HBV infection is rare.
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PMID:Highly active antiretroviral therapy used to treat concurrent hepatitis B and human immunodeficiency virus infections. 1021 32

Hepatitis B virus (HBV) is a small enveloped virus containing partially double-stranded DNA. The DNA and HBV-specific DNA polymerase are surrounded by the HBV core antigen (HBcAg), which in turn is surrounded by a lipoprotein envelope containing the HBV surface antigen (HBsAg). Serum of HBV-infected patients contains complete virus particles, as well as non-infectious spherical or filamentous HBsAg particles. Acute hepatitis is characterized by the appearance of serum HBV markers, including HBsAg and IgM anti-HBc, which then disappear during convalescence. Persistence of HBsAg for more than 6 months indicates a carrier state. Chronic hepatitis develops in 90% of newborns who become infected, compared with 29-40% of children infected and 5-10% of adults infected. The immune status of the infected person also influences the development of chronic hepatitis. Chronic HBV infection can be diagnosed by serology (identification of HBsAg and HBV DNA), biochemistry (elevated aminotransferase levels) and liver biopsy. The last is important to assess the severity of disease, its stage and prognosis, and to exclude other hepatic diseases. The outcome of chronic HBV infection varies between individuals, with estimated 5-year survivals of 97% for chronic persistent hepatitis, 86% for chronic active hepatitis, and 55% for chronic active hepatitis with cirrhosis. Treatment with interferon alpha is effective in up to 40% of cases, but in view of the very large number of infected people worldwide, vaccination to prevent spread of the disease is a more cost-effective option.
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PMID:Clinical course and consequences of hepatitis B infection. 1068 39

Hepatitis B virus (HBV) reactivation, a well-known complication in immunosuppressed patients, can give rise to acute hepatitis and even fatal fulminant hepatitis. Three Japanese males with non-Hodgkin's lymphoma (NHL) who were carriers of HBV received high-dose chemotherapy followed by autologous peripheral blood stem cell transplantation (PBSCT). To prevent HBV reactivation, all received oral lamivudine (150 mg/day), a nucleoside analogue, at the start of chemotherapy. All were treated at full-dose intensity, including corticosteroids, without modification of treatment regimens. All three patients completed the total course of chemotherapy and PBSCT, with no signs of HBV reactivation. Peripheral blood stem cell (PBSC) harvests and hematological recoveries after transplantation were not affected by lamivudine, which was continued for at least 16 weeks after transplantation. HBV-DNA and DNA polymerase levels remained negative/normal after discontinuation of lamivudine. Lamivudine effectively inhibits HBV replication and has few serious adverse effects, particularly those related to hematopoiesis. Thus, prophylactic use of lamivudine from initiation of chemotherapy deserves consideration in the treatment of HBV carriers who require immunosuppressive chemotherapy, and may prevent HBV reactivation.
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PMID:A possible role for lamivudine as prophylaxis against hepatitis B reactivation in carriers of hepatitis B who undergo chemotherapy and autologous peripheral blood stem cell transplantation for non-Hodgkin's lymphoma. 1131 73


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