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)

Coronaviruses are assembled by budding into smooth membranes of the intermediate ER-to-Golgi compartment. We have studied the association of the viral membrane glycoproteins M and S in the formation of the virion envelope. Using coimmunoprecipitation analysis we demonstrated that the M and S proteins of mouse hepatitis virus (MHV) interact specifically forming heteromultimeric complexes in infected cells. These could be detected only when the detergents used for their solubilization from cells or virions were carefully chosen: a combination of nonionic (NP-40) and ionic (deoxycholic acid) detergents proved to be optimal. Pulse-chase experiments revealed that newly made M and S proteins engaged in complex formation with different kinetics. Whereas the M protein appeared in complexes immediately after its synthesis, newly synthesized S protein did so only after a lag phase of > 20 min. Newly made M was incorporated into virus particles faster than S, which suggests that it associates with preexisting S molecules. Using the vaccinia virus T7-driven coexpression of M and S we also demonstrate formation of M/S complexes in the absence of other coronaviral proteins. Pulse-chase labelings and coimmunoprecipitation analyses revealed that M and S associate in pre-Golgi membranes because the unglycosylated form of M appeared in M/S complexes rapidly. Since no association of M and S was detected when protein export from the ER was blocked by brefeldin A, stable complexes most likely arise in the ER-to-Golgi intermediate compartment. Sucrose velocity gradient analysis showed the M/S complexes to be heterogeneous and of higher order, suggesting that they are maintained by homo- and heterotypic interactions. M/S complexes colocalized with alpha-mannosidase II, a resident Golgi protein. They acquired Golgi-specific oligosaccharide modifications but were not detected at the cell surface. Thus, the S protein, which on itself was transported to the plasma membrane, was retained in the Golgi complex by its association with the M protein. Because coronaviruses bud at pre-Golgi membranes, this result implies that the envelope glycoprotein complexes do not determine the site of budding. Yet, the self-association of the MHV envelope glycoproteins into higher order complexes is indicative of its role in the sorting of the viral membrane proteins and in driving the formation of the viral lipoprotein coat in virus assembly.
 ...
PMID:Envelope glycoprotein interactions in coronavirus assembly. 759 63

We recently found that alterations of amino acids in hypervariable region 1 (HVR1) of the putative envelope glycoprotein (gp70) of hepatitis C virus (HCV) occurred sequentially in the chronic phase of hepatitis at intervals of several months. This finding suggests that mutations in HVR1 are involved in the mechanism of persistent chronic HCV infection involving escape from the immunosurveillance system. To explore this possibility, we examined the humoral immune response to HVR1 with our assay system, in which immunoprecipitation was carried out with sera from patients by using an HVR1 (27-amino-acid) dihydrofolate reductase fusion protein synthesized by in vitro transcription and translation. Results showed that HVR1 contains a sequence-specific immunological epitope that induces the production of antibodies restricted to the specific viral isolate. Furthermore, analysis of the kinetics of the appearance of antibodies in two patients with chronic hepatitis, with whom successive alterations of amino acids of HVR1 have been observed, showed that the titers of anti-HVR1 antibodies usually reached maximal levels several months after the isolation of HCV having the specific sequence of HVR1. This observation suggests that anti-HVR1 antibodies are involved in the genetic drift of HVR1 (minor antigenic variation) by immunoselection. However, the coexistence of HVR1 as an antigen and its specific antibody was sometimes observed. The possibility that HVR1 acts as a neutralizing epitope is discussed.
 ...
PMID:Humoral immune response to hypervariable region 1 of the putative envelope glycoprotein (gp70) of hepatitis C virus. 768 4

In an agammaglobulinemic patient with chronic hepatitis C, a previously identified hypervariable region of the major envelope glycoprotein remained unchanged for 2.5 years. Serum-derived RNA amplified by reverse transcription-polymerase chain reaction was cloned in a bacterial vector, and a minimum of three independent clones were sequenced by dideoxy chain termination reaction. Comparison of consensus sequences from three different time points during the chronic phase of infection showed absolute homology at both amino acid and nucleotide levels. This finding provides support for the role of antibody selection in generating genetic variation and viral persistence; also, it is consistent with the hypothesis that an epitope within this region is the site of virus neutralization. The observations show that the hepatitis seen in hepatitis C virus infection is not dependent on the humoral immune response.
 ...
PMID:Hypervariable region of hepatitis C virus envelope glycoprotein (E2/NS1) in an agammaglobulinemic patient. 814 81

Hepatitis C virus (HCV) is a major cause of post transfusion non-A, non-B hepatitis. The virus contains a positive-strand RNA genome comprised of approximately 9,400 nucleotides. HCV E2/NS1 is probably an envelope glycoprotein (E2). The E2 hypervariable domain appears to contain isolate-specific antibody-binding linear epitopes. Recently, comparative sequence analysis of all the complete and partial HCV sequences published to date indicates that known genotypes of HCV can be classified into six basic groups. We report here that the prevalence of HCV-I, HCV-II, and a mixed form are 77.2%, 11.4%, and 11.4%, respectively. Patients with anti-HCV and HCV-RNA positive chronic active hepatitis received 6MU of interferon-alpha or beta everyday for two weeks followed by 6MU thrice a week for 14 weeks. Complete response to interferon treatment was defined as an ALT level normalized within six months after the end of treatment and maintained within the normal limit for an additional six months. Complete response was found in 42.9% of patients treated for 16 weeks. In a six month follow-up of the complete responders, clearance of viremia was observed in 90.3% at the end of interferon treatment and in 71.0% six months after the end of interferon treatment.
 ...
PMID:[Hepatitis C]. 834 54

Interferon (IFN) has become the standard therapy for chronic hepatitis C. The use of IFN should be accompanied by adequate diagnosis and management using standard practices as well as new and sophisticated techniques now available. A liver biopsy performed prior to IFN therapy initiation remains the standard for adequate histological diagnosis of HCV disease as well as determination of disease severity and the presence of liver cirrhosis. ALT normalization is not adequate to determine complete short-term response to IFN treatment. Adverse effects resulting from IFN therapy include a flulike syndrome, hematologic effects, neuropsychiatric effects, and thyroid abnormalities. The majority of these can be adequately managed without discontinuation of IFN treatment. However, preexisting psychiatric conditions are a contraindication to IFN therapy. IFN treatment also is contraindicated in patients with autoimmune hepatitis (AIH). Therefore, it is important to distinguish AIH from chronic HCV infection using HCV-RNA analysis and determination of autoimmune titers (including anti-LKM antibodies, anti-SMA, and ANA). Recently reported adverse effects of IFN include respiratory and ocular effects. Serological diagnosis of HCV infection has evolved to the use of second- and third-generation ELISA tests. Although sophisticated, these tests cannot distinguish between active and quiescent infection, and therefore are of limited value in monitoring treatment response. Several other techniques have been suggested: the ratio between IgG and IgM class anti-HCV core antibodies, detection of antibodies against a glycosylated recombinant product of the E2 envelope glycoprotein, and several different polymerase chain reaction (PCR) techniques. The latter appears to be the most promising. Use of these techniques should be incorporated into the monitoring of IFN therapy to assist in the evaluation of adequate treatment response, the need for treatment alteration, and estimation of relapse risk upon treatment cessation.
 ...
PMID:Managing patients on interferon therapy. 901 69

Protein:protein interactions, and their subcellular localization, play important roles in coronavirus assembly. In this study, we have identified similar envelope glycoprotein complexes that are present in mouse hepatitis coronavirus A59 (MHV-A59) and bovine coronavirus (BCV) infected cells. Complexes consisting of the spike (S) and membrane (M) proteins were identified in cells infected with MHV-A59 or BCV. Kinetic analyses demonstrated that S and M quickly associated after translation, and suggested that both initially interacted in a pre-Golgi site. In addition, the hemagglutinin esterase (HE) was identified as part of a complex with M and S in BCV infected cells. Taken together, our data indicate that similar glycoprotein complexes are present in cells infected with two different coronaviruses, and thus likely represent important prerequisite complexes involved in virus assembly.
 ...
PMID:Coronavirus envelope glycoprotein assembly complexes. 978 4

Baculovirus gp64 envelope glycoprotein is a major component of the envelope of the budded virus and is involved in virus entry into the host cells by endocytosis. To investigate the cell-surface molecules important for infection of baculovirus into mammalian cells, we constructed a recombinant baculovirus, Ac64-CAluc, which has gp64 and luciferase genes under the polyhedrin and the CAG promoter, respectively. For controls, we constructed recombinant viruses possessing vesicular stomatitis virus (VSV) G protein, mouse hepatitis virus (MHV) S protein, or green fluorescent protein (GFP) gene under the polyhedrin promoter and the luciferase gene under the CAG promoter (AcVSVG-CAluc, AcMHVS-CAluc, and AcGFP-CAluc). Treatment of HepG2 cells with phospholipase C markedly reduced the reporter gene expression by Ac64-CAluc or AcVSVG-CAluc in a dose-dependent manner, whereas AcMHVS-CAluc was shown to be resistant to the treatment. Inhibition with purified lipids and susceptibility to the mutant CHO hamster cell lines deficient in phospholipids synthesis suggest that the interaction of gp64 and phospholipids on the cell surface might play an important role in baculovirus infection into mammalian cells.
 ...
PMID:Characterization of cell-surface determinants important for baculovirus infection. 1114 15

The envelope glycoprotein E2 of hepatitis C virus (HCV) has been shown to bind human target cells. Anti-E2 antibodies have been associated with both recovery from natural infection in humans and protection from challenge with homologous HCV in chimpanzees. Therefore E2 has become a major target for the development of anti-HCV vaccines. Two E2 fragments [amino acids (aa) 450-565 and aa 385-565] derived from a subtype 1b HCV genome were expressed as N-terminally hexahistidine-tagged proteins in Escherichia coli and purified to over 85% purity. Both proteins were specifically recognized by homologous hepatitis-C-patient's serum on Western blotting, suggesting that these E. coli-derived E2 proteins displayed E2-specific antigenicity. E2-116 (aa 450-565) elicited strong antibody responses in BALB/c mice and rabbits. Rabbit antiserum raised against renatured E2-116 (R(E2-116R)) was able to recognize subtype 1b and 1a E2 glycoproteins expressed in mammalian cells on Western blotting. E2-181 (aa 385-565) reacted with 40% of anti-HCV(+) patients' sera in ELISA. R(E2-116R) and E2-181 were successfully used in preliminary modified vaccinia virus Ankara- and DNA-based E2 vaccine studies for detecting antigen expression in vitro and assessing induced humoral immune responses in mice. The E2 proteins and rabbit antiserum reported here could find wider applications in the development of effective diagnostic, prophylactic and therapeutic measures against HCV.
 ...
PMID:Expression, purification, immunological characterization and application of Escherichia coli-derived hepatitis C virus E2 proteins. 1159 17

Hepatitis C virus (HCV) infection induces an acute and chronic liver inflammation through an immune-mediated pathway that may lead to cirrhosis and liver failure. Indeed, HCV-related hepatitis is characterized by a dramatic lymphocyte infiltrate into the liver which is mainly composed by HCV non-specific cells. Several data indicated that interferon (IFN)-gamma secretion by intrahepatic lymphocytes (IHL) may drive non-specific cell homing to the liver, inducing interferon inducible protein-10 (IP-10) production. An interesting hallmark of these IHL is the recruitment of lymphocytes associated with mechanisms of innate immunity, such as natural killer (NK), natural killer T (NKT) and gamma delta T lymphocytes. CD81 triggering on NK cell surface by the HCV envelope glycoprotein E2 was recently shown to inhibit NK cell function in the liver of HCV-infected persons, resulting in a possible mechanism contributing to the lack of virus clearance and to the establishment of chronic infection. In contrast, intrahepatic NKT cells restricted to CD1d molecules expressed on the hepatocyte surface may contribute to a large extent to liver damage. Finally, an increased frequency of T cells expressing the gamma delta T cell receptor (TCR) was observed in HCV-infected liver and recent observations indicate that intrahepatic gamma delta T cell activation could be directly induced by the HCV/E2 particle through CD81 triggering. These cells are not HCV specific, are able to kill target cells including primary hepatocytes and their ability to produce T helper (Th)1 cytokines is associated with a higher degree of liver disease. Together, CD1d/NKT and/or E2/CD81 interactions may play a major role in the establishment of HCV immunopathogenesis. In the absence of virus clearance, the chemokine-driven recruitment of lymphocytes with an innate cytotoxic behavior in the liver of HCV-infected patients may boost itself, leading to necroinflammatory and fibrotic liver disease.
 ...
PMID:Lymphocyte distribution and intrahepatic compartmentalization during HCV infection: a main role for MHC-unrestricted T cells. 1245 64

Group 2 coronaviruses encode an accessory envelope glycoprotein species, the hemagglutinin esterase (HE), which possesses sialate-O-acetylesterase activity and which, presumably, promotes virus spread and entry in vivo by facilitating reversible virion attachment to O-acetylated sialic acids. While HE may provide a strong selective advantage during natural infection, many laboratory strains of mouse hepatitis virus (MHV) fail to produce the protein. Apparently, their HE genes were inactivated during cell culture adaptation. For this report, we have studied the molecular basis of this phenomenon. By using targeted RNA recombination, we generated isogenic recombinant MHVs which differ exclusively in their expression of HE and produce either the wild-type protein (HE+), an enzymatically inactive HE protein (HE0), or no HE at all. HE expression or the lack thereof did not lead to gross differences in in vitro growth properties. Yet the expression of HE was rapidly lost during serial cell culture passaging. Competition experiments with mixed infections revealed that this was not due to the enzymatic activity: MHVs expressing HE+ or HE0 propagated with equal efficiencies. During the propagation of recombinant MHV-HE+, two types of spontaneous mutants accumulated. One produced an anchorless HE, while the other had a Gly-to-Trp substitution at the predicted C-terminal residue of the HE signal peptide. Neither mutant incorporated HE into virion particles, suggesting that wild-type HE reduces the in vitro propagation efficiency, either at the assembly stage or at a postassembly level. Our findings demonstrate that the expression of "luxury" proteins may come at a fitness penalty. Apparently, under natural conditions the costs of maintaining HE are outweighed by the benefits.
 ...
PMID:Luxury at a cost? Recombinant mouse hepatitis viruses expressing the accessory hemagglutinin esterase protein display reduced fitness in vitro. 1630 76


<< Previous 1 2 3 Next >>