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

We report the investigation of the role of humoral and cell mediated immune responses on hepatitis delta virus (HDV) superinfection of woodchucks chronically infected with woodchuck hepatitis virus (WHV). The animals were immunised with baculovirus or vaccinia virus recombinant hepatitis delta antigen (HDAg) but none showed detectable anti-HD titres prior to challenge with HDV. Following infection, both immunised and control animals developed HD-antigenaemia first detected after 2-3 weeks and lasting for up to 8 weeks. In spite of the presence of HDAg, in immunised animals HDV-RNA could only be detected by nested PCR in contrast with the controls, which were positive by dot blot hybridisation. No serum HDAg or HDV-RNA was detected after the acute episode over the six month follow-up period but intrahepatic HDAg was reported in post-mortem biopsies carried out at six months. Our results demonstrate that immunisation of woodchucks with HDAg expressed by vaccinia or baculovirus does not elicit a humoral immune response. The finding of a marked antigenaemia in the absence of serum HDV-RNA indicates a significant reduction in the number of circulating infectious virions possibly due to a cytotoxic T-cell response.
 ...
PMID:Immunisation of woodchucks with hepatitis delta antigen expressed by recombinant vaccinia and baculoviruses, controls HDV superinfection. 850 79

We have studied the production and release of infectious DI-particles in vaccinia-T7-polymerase recombinant virus-infected L cells that were transfected with five different plasmids expressing the synthetic DI RNA MIDI-HD and the four structural proteins (M, N, S, and E) of the murine coronavirus MHV-A59. The DI cDNA contains the hepatitis delta ribozyme sequences to generate in the transfected cells a defined 3' end. In EM studies of transfected cells virus-like particles (VLP) were observed in vesicles. Release of the particles into the medium was studied by immunoprecipitations of proteins released into the culture supernatant. Particle release was independent of S or N, but required M and E. Coexpression of E and M was sufficient for particle release. Coexpression of the structural proteins and the MIDI-HD RNA resulted in the production and release of infectious DI-particles. Infectivity of the DI-particles was determined by adding helper virus MHV-A59 to the medium containing the VLPs and using this mixture to infect new L cells. Intracellular RNA of several subsequent undiluted passages was isolated to detect the MIDI-HD RNA. Passage of the MIDI-HD RNA was dependent on the expression of the structural proteins of MHV-A59 in the transfected cells. In the absence of either E or M, MIDI-HD RNA could not be passaged to fresh L cells. We have thus developed a system in which we can produce coronavirus-like particles and an assay to test their infectivity.
 ...
PMID:The production of recombinant infectious DI-particles of a murine coronavirus in the absence of helper virus. 861 41

Cytotoxic T lymphocyte (CTL) activity specific for mouse hepatitis virus (MHV) JHM strain (JHMV or MHV-4) was examined using in vitro stimulated spleen cells derived from immunized C57BL/6 (H-2b) mice. Target cells infected with JHMV were specifically recognized; however, analysis of target cells expressing the virus structural proteins via recombinant vaccinia viruses showed no recognition of the viral nucleocapsid (N), membrane (M), small membrane (sM) or haemagglutinin-esterase (HE) proteins. Only target cells expressing the virus spike (S) protein were recognized. Furthermore, the majority of CTL activity was restricted to target cells expressing the MHC class I Db molecules. Analysis of truncations and deletions of the S protein expressed by recombinant vaccinia viruses and peptide coated targets identified a single antigenic epitope, aa 510-518, conforming to the Db binding motif. These amino acids are contained within a domain deleted from a number of strains of mouse hepatitis virus, suggesting a role for immune pressure. To determine the potential for CTL specific for an epitope(s) within a non-structural protein, 24 CTL lines were established and characterized. No evidence for the induction of non-specific CTL activity or virus-specific CTL restricted to an epitope in a non-structural protein was obtained. These data indicate that the predominant CTL activity in JHMV-infected C57BL/6 mice is Db restricted and specific for a single epitope contained within aa 510-518 of the S protein.
 ...
PMID:The JHM strain of mouse hepatitis virus induces a spike protein-specific Db-restricted cytotoxic T cell response. 862 36

The envelopes of murine hepatitis virus (MHV) particles are studded with glycoprotein spikes that function both to promote virion binding to its cellular receptor and to mediate virion-cell membrane fusion. In this study, the cysteine-rich spikes were subjected to chemical modification to determine whether such structural alterations impact the virus entry process. Ellman reagent, a membrane-impermeant oxidizing agent which reacts with exposed cysteine residues to effect covalent addition of large thionitrobenzoate moieties, was incubated at 37 degrees C with the JHM strain of MHV. Relative to untreated virus, 1 mM Ellman reagent reduced infectivity by 2 log(10) after 1 h. This level of inhibition was not observed at incubation temperatures below 21 degrees C, suggesting that virion surface proteins undergo thermal transitions that expose cysteine residues to modification by the reagent. Quantitative receptor binding and membrane fusion assays were developed and used to show that Ellman reagent specifically inhibited membrane fusion induced by the MHV JHM spike protein. However, this inhibition was strain specific, because the closely related MHV strain A59 was unaffected. To identify the basis for this strain specificity, spike cDNAs were prepared in which portions encoded either JHM or A59 residues. cDNAs were expressed with vaccinia virus vectors and tested for sensitivity to Ellman reagent in the fusion assays. The results revealed a correlation between the severity of inhibition mediated by Ellman reagent and the presence of a JHM-specific cysteine (Cys-1163). Thus, the presence of this cysteine increases the availability of spikes for a thiol modification that ultimately prevents fusion competence.
 ...
PMID:Murine coronavirus membrane fusion is blocked by modification of thiols buried within the spike protein. 867 94

The positive-strand defective interfering (DI) RNA of the murine coronavirus mouse hepatitis virus (MHV), when introduced into MHV-infected cells, results in DI RNA replication and accumulation. We studied whether the introduction of negative-strand transcripts of MHV DI RNA would also result in replication. At a location downstream of the T7 promoter and upstream of the human hepatitis delta virus ribozyme domain, we inserted a complete cDNA clone of MHV DI RNA in reverse orientation; in vitro-synthesized RNA from this plasmid yielded a negative-strand RNA copy of the MHV DI RNA. When the negative-strand transcripts of the DI RNA were expressed in MHV-infected cells by a vaccinia virus T7 expression system, positive-strand DI RNAs accumulated in the plasmid-transfected cells. DI RNA replication depended on the expression of T7 polymerase and on the presence of the T7 promoter. Transfection of in vitro-synthesized negative-strand transcripts into MHV-infected cells and serial passage of virus samples from RNA-transfected cells also resulted in accumulation of the DI RNA. Positive-strand DI RNA transcripts were undetectable in sample preparations of the in vitro-synthesized negative-strand DI RNA transcripts, and DI RNA did not accumulate after cotransfection of a small amount of positive-strand DI RNA and truncated-replication-disabled negative-strand transcripts; clearly, the DI RNA replicated from the transfected negative-strand transcripts and not from minute amounts of positive-strand DI RNAs that might be envisioned as artifacts of T7 transcription. Sequence analysis of positive-strand DI RNAs in the cells transfected with negative-strand transcripts showed that DI RNAs maintained the DI-specific unique sequences introduced within the leader sequence. These data indicated that positive-strand DI RNA synthesis occurred from introduced negative-strand transcripts in the MHV-infected cells; this demonstration, using MHV, of DI RNA replication from transfected negative-strand DI RNA transcripts is the first such demonstration among all positive-stranded RNA viruses.
 ...
PMID:Replication of murine coronavirus defective interfering RNA from negative-strand transcripts. 870 92

The mouse hepatitis virus (MHV) spike glycoprotein mediates attachment of the virus to the MHV receptor, the murine biliary glycoprotein (BGP) carcinoembryonic antigen. Monoclonal antibody CC1 directed against BGP specifically inhibited infection of DBT, Sac-, GT1-7, and OBL21 cells by wild-type MHV-4 and the neuron-adapted variant OBLV60. Binding to this receptor was necessary to establish infection by cell-free MHV; however, the presence of BGP was not required for infection by cell-associated virus. Cell-associated infectious induced syncytium formation on Vero and BHK cells, which lack murine BGP; this activity was not inhibited by monoclonal antibody CC1. Antibody CC1 also did not prevent syncytium formation on DBT cells, which bear BGP. In infectious center assays, the MHV-4 variant OBLV60, which exhibits acid-dependent fusion, spread to cells lacking BGP only when exposed to acidic media. Therefore, spike-mediated fusion was required for BGP-independent spread of MHV infection. Furthermore, BGP-independent, cell-associated spread of MHV-4 was prevented by monoclonal antibodies 5A13.5 and 5B19.2 directed against the spike glycoprotein, but not by other neutralizing and nonneutralizing anti-spike antibodies. Expression of spike glycoprotein by recombinant vaccinia virus resulted in fusion of BGP-negative cells; monoclonal antibodies 5A13.5 and 5B19.2 strongly inhibited spike-mediated fusion in this assay.
 ...
PMID:Spike glycoprotein-mediated fusion in biliary glycoprotein-independent cell-associated spread of mouse hepatitis virus infection. 880 41

We have investigated the intracellular localization of several of the proteolytic cleavage products derived from the 5' portion of mouse hepatitis virus (MHV) gene 1. Antisera UP1 recognizes the N-terminal ORF1a cleavage product p28. Immunofluorescent staining of cells with this antisera resulted in a diffuse punctate pattern of cytoplasmic staining, indicating that this protein is widely distributed in the cytoplasm. Immunofluorescent staining of infected cells with antisera which recognize polypeptides p240 and p290 stained discrete vesicular perinuclear structures suggesting that these proteins localized to the Golgi. This was confirmed by double immunofluorescent staining of BHK cells expressing the MHV receptor (BHK-R) with a Golgi specific antibody in addition to our anti-MHV ORF1a antibodies. Antisera UP102 recognizes p28 and the immediately downstream p65 gene product. Double immunofluorescent staining of MHV infected BHK-R cells with UP102 labeled discrete vesicular structures overlapping the Golgi complex. In addition there was punctate staining more widely distributed in the cytoplasm. The simplest explanation for this pattern is that p65 is also localized to the Golgi region of the cell, whereas p28 is more widespread. Plasmids containing the first 4.7 and 6.75 kb of ORF 1a have been expressed using the coupled vaccinia virus-T7 polymerase system. Images obtained by immunofluorescent staining of transfectants with our anti-ORF1a antisera are similar to those obtained during infection with A59. These studies indicate that the signals which direct p290 to the Golgi are likely contained between the C-terminus of p28 and ORF1a residue 1494.
 ...
PMID:Intracellular localization of polypeptides encoded in mouse hepatitis virus open reading frame 1A. 883 Apr 88

The intracellular interaction of the coronavirus mouse hepatitis virus (MHV) with its cellular receptor (MHVR) was investigated. Overexpression of MHVR from vaccinia vectors during an ongoing MHV infection resulted in dramatic inhibition of virus production. Infectivity in both cytoplasmic extracts and supernatants was reduced by over three orders of magnitude relative to control cultures in which a truncated MHVR lacking virus binding activity was expressed. Complete MHV virions were not detectable in supernatants of MHVR expressing cells. In the presence of overexpressed MHVR, the coronavirus spike protein was not cleaved into posttranslation products S1 and S2, nor was it fully processed into a form resistant to endoglycosidase H digestion, indicating that intracellular engagement of spike with receptor prevented spike transport and consequent association with virions.
 ...
PMID:Overexpression of the MHV receptor. Effect on progeny virus secretion. 883 May 3

CD8+ CTL responses constitute a critical component for vaccines developed to eliminate intracellular pathogens. One approach to achieve broad CTL diversity is based on genetically linking immunogenic peptides from multiple proteins to form poly-epitope Ags. To address the influence of flanking residues on class I Ag presentation, H-2d-restricted HIV-1 and mouse hepatitis virus CTL epitopes were linked via various spacer residues. The resulting 20 to 31 amino acid peptides were expressed using recombinant vaccinia viruses to monitor both CTL recognition and induction. Our data indicate that recognition is profoundly influenced by the nature of intervening residues forming carboxyl-terminal flanks for one and amino-terminal flanks for the other epitope. Flanking amino acids with aromatic (tyrosine), basic (lysine), and small aliphatic side chains (alanine) supported efficient CTL recognition of both epitopes. By contrast, acidic and helix breaking residues (glycine, proline) specifically inhibited recognition of the adjacent amino-terminal epitope. Flanking residues inhibitory for recognition were also detrimental for CTL induction, suggesting similar processing mechanisms in vitro and in vivo. The ratios of peptide-specific CTL precursors primed by the tandem epitopes varied up to 50-fold depending on molecular context. These data demonstrate a substantial role of carboxyl-flanking residues in governing the efficiency of class I Ag presentation both in vitro and in vivo. The dramatic influence of flanking residues on the hierarchy of CTL responses indicates that CTL induction by poly-epitope Ags can be optimized by strategically linking epitopes via selection of appropriate spacer residues.
 ...
PMID:Flanking residues alter antigenicity and immunogenicity of multi-unit CTL epitopes. 887 18

Two hundred years ago Edward Jenner inoculated James Phipps with vaccinia and 181 years later smallpox had disappeared from the surface of the earth as a result of generalized vaccination. Compared to the requirements of modern vaccinology, the procedures used by Jenner and his successors, were extremely primitive because of an almost total lack of knowledge in the field of microbiology and immunology. The active principle of smallpox vaccine is vaccinia virus, which in many respects, differs from that of natural cowpox; the term "cowpox" has been used for more than a century and a half to designate the vaccine; it appears itself to be a misnomer, because it is most probably by a virus of rodents, which only occasionally infects bovines or other species, especially cats. The origin of vaccinia remains doubtful, but a plausible explanation is that it is derived from horse-pox. Jenner was convinced that he was working with a virus of equine origin, which was occasionally transmitted from the horse to the cow by the personnel on the farms. Horse pox has now completely disappeared. Especially during the first years after Jenner's discovery, great confusion was caused by other lesions on the cow's udder, which were called "spurious cowpox". We know today that these lesions could be caused by the viruses of papular stomatitis, pseudo-cowpox or para-vaccinia (milker's nodules), herpes mammilitis and papillomatosis; they could not be differentiated from those of cowpox or vaccinia, in addition lesions due to bacteria or other causes also led to confusion. During the first eighty years the vaccine was being transferred almost exclusively from arm to arm with the risks inherent in this procedure; one of the reasons for applying this method was the fear of "bestialization" thought to be linked with the use of material of animal origin. Several contaminations have been observed as a result of the use of the arm-to-arm procedure: smallpox was transmitted, especially in the beginning, because vaccinations were carried out in a contaminated environment. Syphilis was diagnosed in several countries after the use of vaccine taken from syphilis patients. At least two foci of hepatitis were reported after the use of contaminated human lymph. Transmission of tuberculosis or what was then designated as scrofulosis was unlikely, but was used as one of the main arguments against vaccination by the antivaccinists. Varicella and measles were transmitted from time to time with the vaccine and also bacterial infections, such as staphylococci, streptococci e.a. From the global point of view, however, the number of contaminations remained limited in comparison with the large numbers of vaccinations that were performed. Another problem the early vaccinators were facing, was that of the decline and disappearance of the immunity after a certain number of years. Jenner and his successors believed that the immunity post vaccination would be lifelong as it was after variolation. When in the early part of the 19th century more and more immunity breakdowns occurred, this observation led to total confusion and it took dozens of years of debate and controversy before the only logical and efficacious measure, i.e. revaccination, was generally accepted and implemented. In the last third of the 19th century "human lymph", obtained by arm-to-arm vaccination, was gradually replaced everywhere by animal lymph i.e. vaccine produced on the skin of animals, mainly calves. The determining factor in the switch was the risk of vaccination syphilis. Everywhere vaccine institutes were created, where the vaccinia virus was propagated on the skin of calves. The harvested virus served each time for the inoculation of fresh calves; this resulted in a gradual increase of the number of passages leading to the possible risk of overattenuation. To avoid this risk, passages in man, donkeys, rabbits or other species were performed from time to time.
 ...
PMID:[Jenner's cowpox vaccine in light of current vaccinology]. 902 32


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>