Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.26.4 (RNase H)
 2,751 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Constructs expressing the core, surface, X, or polymerase proteins of hepatitis B virus were transfected into human cells. In transient assays, only the polymerase inhibited the responses to interferons alpha and gamma (IFN-alpha and -gamma). Stable expression of the polymerase was achieved in the cell line 2fTGH, which carries an IFN-inducible marker gene, by growth under conditions that select for inhibition of the response to IFN-alpha, but the clones grew poorly. When expressed alone, the terminal protein domain of the polymerase gene inhibited the response to IFN-alpha and the reverse transcriptase plus RNase H domains appeared to be toxic. Clones of cells expressing terminal protein alone, selected for the loss of response to IFN-alpha, grew normally and had no detectable response to IFN-alpha, IFN-gamma, or double-stranded RNA. Binding of IFN-alpha to these cells was not impaired but did not lead to activation of the E alpha subunit of the IFN-induced transcription factor E. These observations are of potential importance in relation to the pathogenesis of chronic hepatitis B virus infection and the resistance of such infection to IFN-alpha therapy.
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PMID:Expression of the terminal protein region of hepatitis B virus inhibits cellular responses to interferons alpha and gamma and double-stranded RNA. 170 74

Antibodies against the RNase H domain of human hepatitis B virus P protein(s) are frequent markers of acute and chronic virus infection (T. Weimer, K. Weimer, Z.-X. Tu, M.-C. Jung, G. R. Pape, and H. Will, J. Immunol. 143:3750-3756, 1989). In the present study, these antibodies were determined in serial serum samples of experimentally infected chimpanzees and naturally infected human patients with acute and chronic hepatitis B virus infection. Anti-P antibodies were found in the sera of both chimpanzees and humans early in infection shortly after the immunoglobulin M anti-HBc response; they persisted in chronic carriers with ongoing viral replication but declined and disappeared at the time of virus clearance from the sera. These data demonstrate that antibodies to the RNase H domain of the hepatitis B virus P protein are early markers of infection and a signal of ongoing virus replication. Falling titers indicate the decline or end of active virus production and may therefore be a prognostic sign of virus elimination in natural infection and after antiviral therapy.
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PMID:Antibodies to the RNase H domain of hepatitis B virus P protein are associated with ongoing viral replication. 217 Jun 93

Cytotoxic T lymphocytes (CTL) are thought to contribute to viral clearance and liver cell injury during hepatitis B virus (HBV) infection. Using a strategy involving the in vitro stimulation of peripheral blood mononuclear cells (PBMC) with HBV-derived synthetic peptides containing HLA-A2.1, -A31, and -Aw68 binding motifs, we have previously described CTL responses to several epitopes within the HBV nucleocapsid and envelope antigens in patients with acute hepatitis. In this study we define six HLA-A2-restricted CTL epitopes located in the highly conserved reverse transcriptase and RNase H domains of the viral polymerase protein, and we show that the CTL response to polymerase is polyclonal, multispecific, and mediated by CD8+ T cells in patients with acute viral hepatitis, but that it is not detectable in patients with chronic HBV infection or uninfected healthy blood donors. Importantly, the peptide-activated CTL recognize target cells that express endogenously synthesized polymerase protein, suggesting that these peptides represent naturally processed viral epitopes. DNA sequence analysis of the viruses in patients who did not respond to peptide stimulation indicated that CTL nonresponsiveness was not due to infection by viral variants that differed in sequences from the synthetic peptides. CTL specific for one of the epitopes were unable to recognize several naturally occurring viral variants, except at high peptide concentration, underlining the HBV subtype specificity of this response. Furthermore, CTL responses against polymerase, core, and envelope epitopes were detectable for more than a year after complete clinical recovery and seroconversion, reflecting either the persistence of trace amounts of virus or the presence of long lived memory CTL in the absence of viral antigen. Finally, we demonstrated that wild type viral DNA and RNA can persist indefinitely, in trace quantities, in the serum and PBMC after complete clinical and serological recovery, despite a concomitant, vigorous, and sustained polyclonal CTL response. Since viral persistence is not due to escape from CTL recognition under these conditions, the data suggest that HBV may retreat into immunologically privileged sites from which it can seed the circulation and reach CTL-inaccessible tissues, thereby maintaining the CTL response in apparently cured individuals and, perhaps, prolonging the liver disease in patients with chronic hepatitis.
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PMID:The cytotoxic T lymphocyte response to multiple hepatitis B virus polymerase epitopes during and after acute viral hepatitis. 753 75

A single-step reverse transcription polymerase chain reaction (SRT-PCR) method was optimized for hepatitis C virus (HCV) RNA detection. Extraction procedures by proteinase K and guanidinium isothiocyanate gave similar results. The optimal MgCl2 concentration for the SRT-PCR method was 2 mM with 10 units of superscript M-MLV RNase H-reverse transcriptase and 1 unit of Taq polymerase. Shorter PCR cycling steps gave a 10-fold-increased PCR product compared with longer cycling steps. Twenty-five anti-HCV-positive sera from chronic hepatitis C patients were positive with SRT-PCR, whereas only 17 out of 25 were positive by dissociated RT and PCR (dRT/PCR). Specificity was assessed by twenty negative controls. SRT-PCR was 5-fold more sensitive (5 HCV RNA copies per assay) than dRT/PCR with an HCV RNA transcript. Our SRT-PCR method for HCV RNA detection appears fully adapted for routine use in a medical virology laboratory.
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PMID:Detection of hepatitis C virus RNA by a reliable, optimized single-step reverse transcription polymerase chain reaction. 857 10

Extracellular HBV RNA has been detected in both HBV-replicating cell culture media and sera from chronic hepatitis B (CHB) patients, but its exact origin and composition remain controversial. Here, we demonstrated that extracellular HBV RNA species were of heterogeneous lengths, ranging from the length of pregenomic RNA to a few hundred nucleotides. In cell models, these RNAs were predominantly associated with naked capsids, although virions also harbored a minority of them. Moreover, HBV RNAs in hepatitis B patients' blood circulation were localized in unenveloped capsids in the form of capsid-antibody complexes (CACs) and in virions. Furthermore, we showed that extracellular HBV RNAs could serve as the template for viral DNA synthesis. In conclusion, extracellular HBV RNAs mainly consist of pgRNA or the pgRNA species degraded by the RNase H domain of the polymerase in the process of viral DNA synthesis and circulate as CACs and virions. Their presence in blood circulation of CHB patients may be exploited to develop novel biomarkers for HBV persistence.IMPORTANCE Although increasing evidence suggests the presence of extracellular HBV RNA species, their origin and molecular forms are still under debate. In addition to the infectious virions, HBV is known to secrete several species of incomplete viral particles, including hepatitis B surface antigen (HBsAg) particles, naked capsids, and empty virions, during its replication cycle. Here, we demonstrated that extracellular HBV RNAs were associated with naked capsids and virions in HepAD38 cells. Interestingly, we found that unenveloped capsids circulate in the blood of hepatitis B patients in the form of CACs and, together with virions, serve as vehicles carrying these RNA molecules. Moreover, extracellular HBV RNAs are heterogeneous in length and represent either pregenomic RNA (pgRNA) or products of incomplete reverse transcription during viral replication. These findings provide a conceptual basis for further application of extracellular RNA species as novel biomarkers for HBV persistence.
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PMID:Extracellular Hepatitis B Virus RNAs Are Heterogeneous in Length and Circulate as Capsid-Antibody Complexes in Addition to Virions in Chronic Hepatitis B Patients. 3028 9