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  • American Society for Microbiology  (7)
  • 1
    Online Resource
    Online Resource
    Glycine Decarboxylase Mediates a Postbinding Step in Duck Hepatitis B Virus Infection
    American Society for Microbiology ; 2004
    In:  Journal of Virology Vol. 78, No. 4 ( 2004-02-15), p. 1873-1881
    Details
    In: Journal of Virology, American Society for Microbiology, Vol. 78, No. 4 ( 2004-02-15), p. 1873-1881
    Abstract: Envelope protein precursors of many viruses are processed by a basic endopeptidase to generate two molecules, one for receptor binding and the other for membrane fusion. Such a cleavage event has not been demonstrated for the hepatitis B virus family. Two binding partners for duck hepatitis B virus (DHBV) pre-S envelope protein have been identified. Duck carboxypeptidase D (DCPD) interacts with the full-length pre-S protein and is the DHBV docking receptor, while duck glycine decarboxylase (DGD) has the potential to bind several deletion constructs of the pre-S protein in vitro. Interestingly, DGD but not DCPD expression was diminished following prolonged culture of primary duck hepatocytes (PDH), which impaired productive DHBV infection. Introduction of exogenous DGD promoted formation of protein-free viral genome, suggesting restoration of several early events in viral life cycle. Conversely, blocking DGD expression in fresh PDH by antisense RNA abolished DHBV infection. Moreover, addition of DGD antibodies soon after virus binding reduced endogenous DGD protein levels and impaired production of covalently closed circular DNA, the template for DHBV gene expression and genome replication. Our findings implicate this second pre-S binding protein as a critical cellular factor for productive DHBV infection. We hypothesize that DCPD, a molecule cycling between the cell surface and the trans -Golgi network, targets DHBV particles to the secretary pathway for proteolytic cleavage of viral envelope protein. DGD represents the functional equivalent of other virus receptors in its interaction with processed viral particles.
    Type of Medium: Online Resource
    ISSN: 0022-538X , 1098-5514
    URL: Article
    DOI: 10.1128/JVI.78.4.1873-1881.2004
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2004
    detail.hit.zdb_id: 1495529-5
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  • 2
    Online Resource
    Online Resource
    Early Detection of Hepatitis E Virus Ribavirin Resistance Using Next-Generation Sequencing
    American Society for Microbiology ; 2019
    In:  Antimicrobial Agents and Chemotherapy Vol. 64, No. 1 ( 2019-12-20)
    Details
    In: Antimicrobial Agents and Chemotherapy, American Society for Microbiology, Vol. 64, No. 1 ( 2019-12-20)
    Type of Medium: Online Resource
    ISSN: 0066-4804 , 1098-6596
    URL: Article
    DOI: 10.1128/AAC.01525-19
    RVK:
    XA 24552
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2019
    detail.hit.zdb_id: 1496156-8
    SSG: 12
    SSG: 15,3
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  • 3
    Online Resource
    Online Resource
    Characterization of the surface layer glycoprotein of Clostridium symbiosum HB25
    American Society for Microbiology ; 1990
    In:  Journal of Bacteriology Vol. 172, No. 5 ( 1990-05), p. 2576-2583
    Details
    In: Journal of Bacteriology, American Society for Microbiology, Vol. 172, No. 5 ( 1990-05), p. 2576-2583
    Abstract: The cell surface of Clostridium symbiosum HB25 is covered by a squarely arranged surface layer (S-layer) glycoprotein. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the sodium dodecyl sulfate-soluble whole-cell extract showed the presence of several high-molecular-weight protein bands in a narrow range (approximate Mr, 140,000) which, upon periodic acid-Schiff staining, gave a positive reaction. After proteolytic degradation of the purified S-layer glycoprotein, a single glycopeptide fraction was obtained by gel permeation chromatography. Hydrolysis, treatment with aqueous hydrofluoric acid, and 1H and 13C nuclear magnetic resonance studies showed that the glycoprotein glycan is a high-molecular-weight polymer (approximate Mr, 15,000) of tetrasaccharide repeating units with the component sugars N-acetylgalactosamine (GalNAc), N-acetylmannosamine (ManNAc), and N-acetylbacillosamine (BacNAc; 2-N-acetyl-4-amino-2,4,6-trideoxy glucose) linked by monophosphate diesters. The following structure is proposed: [----6)-alpha-D-ManpNAc-(1----4)-beta-D-GalpNAc-(1----3)-alpha-D-+ ++BacpNAc- (1----4)-alpha-D-GalpNAc-(1----PO3)----]n. The nuclear magnetic resonance data provided evidence for a charge interaction between the free amino group of BacNAc and the phosphate group of adjacent glycan chains. Since polycationic ferritin did not label the cell surface of intact cells, an electrostatic interaction can also be expected in vivo, leading to a charge-neutral outer surface, which is characteristic of all other S layers from members of the family Bacillaceae studied so far.
    Type of Medium: Online Resource
    ISSN: 0021-9193 , 1098-5530
    URL: Article
    DOI: 10.1128/jb.172.5.2576-2583.1990
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 1990
    detail.hit.zdb_id: 1481988-0
    SSG: 12
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  • 4
    Online Resource
    Online Resource
    The Enhancer I Core Region Contributes to the Replication Level of Hepatitis B Virus In Vivo and In Vitro
    American Society for Microbiology ; 2000
    In:  Journal of Virology Vol. 74, No. 5 ( 2000-03), p. 2193-2202
    Details
    In: Journal of Virology, American Society for Microbiology, Vol. 74, No. 5 ( 2000-03), p. 2193-2202
    Abstract: Chronic hepatitis B virus (HBV) infection can lead to liver cirrhosis and hepatocellular carcinoma. Long-term interaction of the immune system with the virus results in the selection of escape mutants and viral persistence. In this work we characterize mutations in the enhancer I region isolated prior to liver transplantation from the HBV genomes of 10 patients with chronic HBV infection. The HBV-genomes were sequenced, and the enhancer I region was cloned into luciferase reporter constructs to determine the transcriptional activity. Functional studies were performed by transfecting HBV replication-competent plasmids into hepatoma cells. Analyses of the replication fitness of the mutant strains were conducted by biochemical analysis. In all HBV genomes the enhancer I region was mutated. Most of these mutations resulted in decreased transcriptional activity. The strongest effects were detectable in strains with mutations in the hepatocyte nuclear factor 3 and 4 (HNF3 and HNF4) binding sites of the enhancer I core domain. Replication-competent HBV constructs containing these mutations demonstrated up to 10-fold-reduced levels of virus replication. Before liver transplantation, when the mutant strains were detected in the patients' sera, low HBV DNA levels were found. After transplantation and reinfection with a wild-type virus, the levels of replication were up to 240-fold higher. Our results show that mutations in the enhancer I region of HBV have a major impact on HBV replication. These mutations may also determine the switch from high to low levels of viral replication which is frequently observed during chronic HBV infection.
    Type of Medium: Online Resource
    ISSN: 0022-538X , 1098-5514
    URL: Article
    DOI: 10.1128/JVI.74.5.2193-2202.2000
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2000
    detail.hit.zdb_id: 1495529-5
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  • 5
    Online Resource
    Online Resource
    Cross-Resistance Testing of Antihepadnaviral Compounds Using Novel Recombinant Baculoviruses Which Encode Drug-Resistant Strains of Hepatitis B Virus
    American Society for Microbiology ; 2001
    In:  Antimicrobial Agents and Chemotherapy Vol. 45, No. 6 ( 2001-06), p. 1705-1713
    Details
    In: Antimicrobial Agents and Chemotherapy, American Society for Microbiology, Vol. 45, No. 6 ( 2001-06), p. 1705-1713
    Abstract: Long-term nucleoside analog therapy for hepatitis B virus (HBV)-related disease frequently results in the selection of mutant HBV strains that are resistant to therapy. Molecular studies of such drug-resistant variants are clearly warranted but have been difficult to do because of the lack of convenient and reliable in vitro culture systems for HBV. We previously developed a novel in vitro system for studying HBV replication that relies on the use of recombinant baculoviruses to deliver greater than unit length copies of the HBV genome to HepG2 cells. High levels of HBV replication can be achieved in this system, which has recently been used to assess the effects of lamivudine on HBV replication and covalently closed circular DNA accumulation. The further development of this novel system and its application to determine the cross-resistance profiles of drug-resistant HBV strains are described here. For these studies, novel recombinant HBV baculoviruses which encoded the L526M, M550I, and L526M M550V drug resistance mutations were generated and used to examine the effects of these substitutions on viral sensitivity to lamivudine, penciclovir (the active form of famciclovir), and adefovir, three compounds of clinical importance. The following observations were made: (i) the L526M mutation confers resistance to penciclovir and partial resistance to lamivudine, (ii) the YMDD mutations M550I and L526M M550V confer high levels of resistance to lamivudine and penciclovir, and (iii) adefovir is active against each of these mutants. These findings are supported by the limited amount of clinical data currently available and confirm the utility of the HBV-baculovirus system as an in vitro tool for the molecular characterization of clinically significant HBV strains.
    Type of Medium: Online Resource
    ISSN: 0066-4804 , 1098-6596
    URL: Article
    DOI: 10.1128/AAC.45.6.1705-1713.2001
    RVK:
    XA 24552
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2001
    detail.hit.zdb_id: 1496156-8
    SSG: 12
    SSG: 15,3
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  • 6
    Online Resource
    Online Resource
    In Vitro Susceptibilities of Wild-Type or Drug-Resistant Hepatitis B Virus to (−)-β- d -2,6-Diaminopurine Dioxolane and 2′-Fluoro-5-Methyl-β- l -Arabinofuranosyluracil
    American Society for Microbiology ; 2001
    In:  Antimicrobial Agents and Chemotherapy Vol. 45, No. 9 ( 2001-09), p. 2495-2501
    Details
    In: Antimicrobial Agents and Chemotherapy, American Society for Microbiology, Vol. 45, No. 9 ( 2001-09), p. 2495-2501
    Abstract: Prolonged treatment of chronic hepatitis B virus (HBV) infection with lamivudine ([−]-β- l -2′,3′-dideoxy-3′ thiacytidine) or famciclovir may select for viral mutants that are drug resistant due to point mutations in the polymerase gene. Determining whether such HBV mutants are sensitive to new antiviral agents is therefore important. We used a transient transfection system to compare the sensitivities of wild-type HBV and four lamivudine- and/or famciclovir-resistant HBV mutants to adefovir [9-(2-phosphonyl-methoxyethyl)-adenine; PMEA] and the nucleoside analogues (−)-β- d -2, 6-diaminopurine dioxolane (DAPD) and 2′-fluoro-5-methyl-β- l -arabinofuranosyluracil ( l -FMAU). The drug-resistant mutants contained amino acid substitutions in the polymerase protein. We found that the M550I and M550V plus L526M substitutions, which confer lamivudine resistance, did not confer cross-resistance to adefovir or DAPD, but conferred cross-resistance to l -FMAU. The M550V substitution in isolation conferred a similar phenotype to M550I, except that it did not confer significant resistance to l -FMAU. The L526M substitution, which is associated with famciclovir resistance, conferred cross-resistance to l -FMAU but not to adefovir or DAPD. Inhibition of HBV secretion by DAPD, l -FMAU, and adefovir did not always correlate with inhibition of the generation of intracellular HBV replicative intermediates, suggesting that these analogs may preferentially inhibit specific stages of the viral replication cycle.
    Type of Medium: Online Resource
    ISSN: 0066-4804 , 1098-6596
    URL: Article
    DOI: 10.1128/AAC.45.9.2495-2501.2001
    RVK:
    XA 24552
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2001
    detail.hit.zdb_id: 1496156-8
    SSG: 12
    SSG: 15,3
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  • 7
    Online Resource
    Online Resource
    A Short Sequence within Domain C of Duck Carboxypeptidase D Is Critical for Duck Hepatitis B Virus Binding and Determines Host Specificity
    American Society for Microbiology ; 2001
    In:  Journal of Virology Vol. 75, No. 22 ( 2001-11-15), p. 10630-10642
    Details
    In: Journal of Virology, American Society for Microbiology, Vol. 75, No. 22 ( 2001-11-15), p. 10630-10642
    Abstract: Virus-cell surface receptor interactions are of major interest. Hepadnaviruses are a family of partially double-stranded DNA viruses with liver tropism and a narrow host range of susceptibility to infection. At least in the case of duck hepatitis B virus (DHBV), host specificity seems controlled partly at the receptor level. The middle portion in the pre-S region of the viral large envelope protein binds specifically to duck carboxypeptidase D (DCPD) but not to its human or chicken homologue. Although domain C of DCPD is implicated in ligand binding, the exact pre-S contact site remains to be determined. We prepared and tested a panel of chimeric constructs consisting of DCPD and human carboxypeptidase D (HCPD). Our results indicate that a short region at the N terminus of domain C (residues 920 to 949) is critical to DHBV binding and is a major determinant for the host specificity of DHBV infection. Replacing this region of the DCPD molecule with its human homologue abolished the DHBV interaction, whereas introducing this DCPD sequence into HCPD conferred efficient DHBV binding. Extensive analysis of site-directed mutants revealed that both conserved and nonconserved residues were important for the pre-S interaction. There were primary sequence variations and secondary structural differences that contributed to the inability of HCPD to bind the DHBV pre-S domain.
    Type of Medium: Online Resource
    ISSN: 0022-538X , 1098-5514
    URL: Article
    DOI: 10.1128/JVI.75.22.10630-10642.2001
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2001
    detail.hit.zdb_id: 1495529-5
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