Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0019158 (hepatitis)
 30,205 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The generation of infectious defective interfering (DI) particles of vesicular stomatitis virus (VSV) entirely from cDNA clones is reported. Bacteriophage T7 RNA polymerase was used to direct the transcription of a complete negative-stranded genomic RNA from a cDNA clone of a VSV DI RNA in cells simultaneously expressing the five VSV proteins from separately transfected cDNA clones. The negative-stranded transcript was encapsidated with N protein, replicated by the VSV polymerase, and the replicated RNAs were assembled and budded to yield infectious DI virions. No helper VSV was required. Replication occurred at high levels and was assayed by direct biochemical means. An exact 3' terminus of the initial transcript, which was generated by autolytic cleavage using a ribozyme from hepatitis delta virus, was critical for replication.
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PMID:Infectious defective interfering particles of VSV from transcripts of a cDNA clone. 131 85

Previously, a system in which an intergenic region from mouse hepatitis virus (MHV) inserted into an MHV defective interfering (DI) RNA led to transcription of a subgenomic DI RNA in helper virus-infected cells was established. In the present study, a DI cDNA containing one UCUAAAC consensus sequence in the middle of the 0.3-kb-long intergenic region located between genes 6 and 7 was constructed. From this DI cDNA clone, 21 mutant DI RNAs were constructed so that each of the seven consensus sequence nucleotides was changed individually to the three alternative bases. These mutants were used to define how changes in the integrity of MHV transcription consensus sequence UCUAAAC affected mRNA transcription. Except for two mutants with the sequences UGUAAAC and UCGAAAC, all of the mutants supported efficient subgenomic DI RNA transcription. This indicated that MHV transcription regulation was sufficiently flexible to recognize altered consensus sequences. Next, these and other mutants were used to examine the leader-body fusion site on the subgenomic DI RNAs. Sequence analysis demonstrated that all subgenomic DI RNAs analyzed contained two pentanucleotide sequences; the first sequence seemed to be contributed by the leader, and the leader-body fusion most likely took place at either the first or the second nucleotide of the second sequence. This observation was not consistent with the proposed coronavirus transcription model (S. C. Baker and M. M. C. Lai, EMBO J. 9:4173-4179, 1990) which states that nucleotide mismatch can be corrected by RNA polymerase proofreading activity.
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PMID:Mutagenic analysis of the coronavirus intergenic consensus sequence. 138 62

The recombinant hepatitis delta virus antigen was obtained as a chimaeric protein fused to the C-terminus of the phage MS2 RNA polymerase. Following induction of the temperature-sensitive promoter, two major polypeptides of about 34 kDa and 29 kDa, and two minor peptides about 21 kDa and 18 kDa, were obtained on PAGE. The 34-kDa protein was identified as the expected recombinant protein by confirming 82% of the primary structure using fast-atom-bombardment mass spectrometry. The most represented degradation product, i.e. the 29-kDa polypeptide, was also characterized by means of mass spectrometry and found to be produced by cleavage between amino acids 261 and 265. The presence of two main protein bands, with a similar difference in size, is also a typical feature of delta antigens, both extracted and recombinant, and it is considered to be derived either from heterogeneity of viral sequences, which can encode hepatitis delta antigen proteins of 195 and 214 amino acids, or from proteolysis of a single precursor. Since the data were obtained with a single viral sequence coding for 195 amino acids fused to 106 residues from MS2 polymerase, there is direct evidence that intrinsic structural properties of the protein sequence are able to cause a specific proteolysis resulting in the presence of two major forms, of which the smaller is 35-40 amino acids at the C-terminus. The recombinant protein can be used as an antigenic substitute of viral antigens both for immunoassays and for the preparation of anti-(hepatitis delta virus) antisera.
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PMID:Characterization by mass spectrometry of a recombinant hepatitis delta virus antigen and its proteolytic products. 154 Dec 67

To examine the role of hepatitis delta virus antigen in the replication of hepatitis delta virus RNA, we have transfected a stable HDAg-positive cell line (A3) and the parental HDAg-negative line (HepG2) with HDV RNA produced in vitro; synthesis of complementary HDV RNA was only detected in HDAg-positive cultures. In contrast, nuclear homogenates from both HDAg-positive and -negative cells synthesized comparable levels of complementary RNA from exogenous HDV RNA. These findings indicate that HDAg is not a necessary component of the transcriptional complex and suggest with other evidence, that a major role for HDAg is likely to be transport of HDV RNA from cytoplasm to nucleus. Transcription of HDV RNA by intact nuclei was sensitive to 1 microgram/ml alpha-amanatin providing firm evidence that, like viroids, this function is performed by host RNA polymerase II.
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PMID:Hepatitis delta antigen is necessary for access of hepatitis delta virus RNA to the cell transcriptional machinery but is not part of the transcriptional complex. 165 99

Sequence analysis of an intracellular defective-interfering (DI) RNA, DIssE, of mouse hepatitis virus (MHV) revealed that it is composed of three noncontiguous genomic regions, representing the first 864 nucleotides of the 5'-end, an internal 748 nucleotides of the polymerase gene, and 601 nucleotides from the 3'-end of the parental MHV genome. DIssE had three base substitutions within the leader sequence and also a deletion of nine nucleotides located at the junction of the leader and the remaining genomic sequence. A system was developed for generating DI RNAs to study the mechanism of MHV RNA replication. A cDNA copy of DIssE RNA was placed downstream of T7 RNA polymerase promoter to generate DI RNAs capable of extremely efficient replication in the presence of a helper virus. We demonstrated that, in the DI RNA-transfected cells, the leader sequence of these DI RNAs was switched to that of the helper virus during one round of replication. This high-frequency leader sequence exchange was not observed if a nine-nucleotide stretch at the junction between the leader and the remaining DI sequence was deleted. This observation suggests that a free leader RNA is utilized for the replication of MHV RNA.
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PMID:Studies of coronavirus DI RNA replication using in vitro constructed DI cDNA clones. 196 21

We have previously shown that most of the defective interfering (DI) RNA of mouse hepatitis virus (MHV) are not packaged into virions. We have now identified, after 21 serial undiluted passages of MHV, a small DI RNA, DIssF, which is efficiently packaged into virions. The DIssF RNA replicated at a high efficiency on its transfection into the helper virus-infected cells. The virus released from the transfected cells interfered strongly with mRNA synthesis and growth of helper virus. cDNA cloning and sequence analysis of DIssF RNA revealed that it is 3.6 kb and consists of sequences derived from five discontinuous regions of the genome of the nondefective virus. The first four regions (domains I to IV) from the 5' end are derived from gene 1, which presumably encodes the RNA polymerase of the nondefective virus. The entire domain I (859 nucleotides) and the first 750 nucleotides of domain II are also present in a previously characterized DI RNA, DIssE, which is not efficiently packaged into virions. Furthermore, the junction between these two domains is identical between the two DI RNAs. The remaining 77 nucleotides at the 3' end of domain II and all of domains III (655 nucleotides) and IV (770 nucleotides) are not present in DIssE RNA. These four domains are derived from gene 1. In contrast, the 3'-most domain (domain V, 447 nucleotides) is derived from the 3' end of the genomic RNA and is also present in DIssE. The comparison of primary sequences and packaging properties between DIsse and DIssF RNAs suggested that domains III and IV and part of the 3' end of domain II contain the packaging signal for MHV RNA. This conclusion was confirmed by inserting these DIssF-unique sequences into a DIssE cDNA construct; the in vitro-transcribed RNA from this hybrid construct was efficiently packaged into virion particles. DIssF RNA also contains an open reading frame, which begins from domain I and ends at the 5'-end 20 bases of domain III. In vitro translation of DIssF RNA and metabolic labeling of the virus-infected cells showed that this open reading frame is indeed translated into a 75-kDa protein. The structures of both DIssE and DIssF RNAs suggest that a protein-encoding capability is a common characteristic of MHV DI RNA.
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PMID:Analysis of efficiently packaged defective interfering RNAs of murine coronavirus: localization of a possible RNA-packaging signal. 224 86

Reverse transcriptase (RT) activity was not detected in any serum sample taken from 22 patients with mainly severe non-A, non-B hepatitis (NANBH), using two assays selected to cover the range of known human and animal retroviruses. The study included patients with fulminant and sub-acute hepatic failure, which was was attributed to sporadic, post-transfusional, and presumed epidemic or water-borne epidemiological forms of NANBH. Although we cannot exclude the possibility that some of the agents implicated in NANBH are retroviruses, our negative findings suggest that other agents may be involved at least in the severe forms of NANBH.
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PMID:Lack of reverse transcriptase activity in serum in sporadic post-transfusional and presumed epidemic or water-borne forms of severe non-A, non-B hepatitis. 245 71

Reverse transcriptase activity was tested in 65 patients with non-A,non-B hepatitis, with positive results in 2 acute sporadic cases with favorable outcome. Virus-like particles were observed in ultra-thin sections of successive serum samples from one of the reverse transcriptase activity-positive patients by electron microscopy. These results suggest that some non-A,non-B hepatitis types could be related to a virus-like agent associated with a reverse transcriptase activity.
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PMID:Virus-like particles associated with reverse transcriptase activity in acute sporadic non-A,non-B hepatitis. 247 89

Viral pathogenicity may be regulated by host defense mechanisms at the virus-immune cell interaction level. The immune system plays an important role in the outcome of acute disease induced by the mouse hepatitis virus type 3 (MHV3) virus. The lymphoid cells act as effectors in the virus elimination as well as targets for viral replication. In order to demonstrate a correlation between MHV3 pathogenicity and viral replication in lymphocytes, genetically-determined resistant A/J and susceptible C57BL/6 mice were infected with pathogenic (L2-MHV3) or nonpathogenic (YAC-MHV3) viral strains. Pathogenicity and histopathologic studies have revealed that lymphoid organs such as thymus and spleen, showed injuries or atrophy in susceptible mice infected with L2-MHV3. No histopathologic lesions in the lymphoid organs occurred in C57BL/6 mice infected with YAC-MHV3 or A/J mice infected with both viruses. The mechanisms involved in the lymphoid injuries were studied regarding viral replication in the lymphoid organs and cells in infected mice. Results indicate that cell depletion in lymphoid organs is caused by a complete viral replication in lymphoid cells. Thy1.2+ and surface IgM+ lymphoid cells from susceptible C57BL/6 mice infected with L2-MHV3 were permissive to viral replication and to subsequent cell lysis. No cell lysis, however, occurred in lymphoid cells from C57BL/6 mice infected with YAC-MHV3 and A/J mice infected with both virus strains. In vitro studies, with purified T and B cell populations were performed to determine the mechanism effecting susceptibility or resistance to viral-induced cell lysis occurring in such cells. A blockade, probably occurring at the viral RNA polymerase activity level, prevents viral replication in resistant cells between the stages of fixation of the virus at the cell-surface receptor and the viral protein translation. These experiments indicate that an intrinsic virus-specific resistant mechanism occurs in lymphoid cells that plays a major role in the viral pathogenicity.
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PMID:Mouse hepatitis virus 3 replication in T and B lymphocytes correlate with viral pathogenicity. 254 12

A system was developed that exploited defective interfering (DI) RNAs of coronavirus to study the role of free leader RNA in RNA replication. A cDNA copy of mouse hepatitis virus DI RNA was placed downstream of the T7 RNA polymerase promoter to generate DI RNAs capable of extremely efficient replication in the presence of a helper virus. We demonstrated that, in the DI RNA-transfected cells, the leader sequence of these DI RNAs was switched to that of the helper virus during one round of replication. This high-frequency leader sequence exchange was not observed if a nine-nucleotide stretch of sequence (UUUAUAAAC) at the junction between the leader and the remaining DI sequence was deleted. This observation suggests that a free leader RNA generated from the genomic RNA of mouse hepatitis virus may participate in the replication of DI RNA.
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PMID:High-frequency leader sequence switching during coronavirus defective interfering RNA replication. 255 55


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