551
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Alcon-LePoder S, Drouet MT, Roux P, Frenkiel MP, Arborio M, Durand-Schneider AM, Maurice M, Le Blanc I, Gruenberg J, Flamand M. The secreted form of dengue virus nonstructural protein NS1 is endocytosed by hepatocytes and accumulates in late endosomes: implications for viral infectivity. J Virol 2005; 79:11403-11. [PMID: 16103191 PMCID: PMC1193635 DOI: 10.1128/jvi.79.17.11403-11411.2005] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The flavivirus nonstructural protein NS1 is expressed as three discrete species in infected mammalian cells: an intracellular, membrane-associated form essential for viral replication, a cell surface-associated form that may be involved in signal transduction, and a secreted form (sNS1), the biological properties of which remain elusive. To determine the distribution of the dengue virus (DEN) sNS1 protein in vivo, we have analyzed by immunohistological means the tissue tropism of purified DEN sNS1 injected intravenously into adult mice. The sNS1 protein was found predominantly associated with the liver, where hepatocytes appeared to represent a major target cell. We further showed that sNS1 could be efficiently endocytosed by human Huh7 and HepG2 hepatocytes in vitro. After its internalization, the protein was detected intracellularly for at least 48 h without being substantially degraded. Colocalization studies of sNS1 with markers of the endolysosomal compartments revealed that the protein was specifically targeted to lysobisphosphatidic acid-rich structures reminiscent of late endosomes, as confirmed by electron microscopy. Intracellular accumulation of sNS1 in Huh7 cells enhanced the fluid phase uptake of rhodamine-labeled dextran. Furthermore, preincubation of Huh7 cells with sNS1 increased dengue virus production after infection with the homologous strain of DEN-1 virus. Our results demonstrate that the accumulation of DEN sNS1 in the late endosomal compartment of hepatocytes potentializes subsequent dengue virus infection in vitro, raising the possibility that sNS1 may contribute to viral propagation in vivo.
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Affiliation(s)
- Sophie Alcon-LePoder
- U.P. Interactions Moléculaires Flavivirus-Hôtes, Institut Pasteur, Paris, France
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552
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Scholle F, Mason PW. West Nile virus replication interferes with both poly(I:C)-induced interferon gene transcription and response to interferon treatment. Virology 2005; 342:77-87. [PMID: 16111732 DOI: 10.1016/j.virol.2005.07.021] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2005] [Revised: 06/06/2005] [Accepted: 07/16/2005] [Indexed: 10/25/2022]
Abstract
West Nile virus (WNV), the leading cause of viral encephalitis in the United States, is an arthropod-transmitted member of the family Flaviviridae. We have explored the interaction of this positive-strand RNA virus with signaling pathways involved in induction of the host's innate immune response. Phosphorylation of STAT-1 in response to interferon (IFN) treatment and the ability of IFN to establish an antiviral state were reduced in WNV replicon-bearing cell lines. Similarly, the activation of IRF3 and stimulation of IFN-beta transcription in response to the double-stranded RNA (dsRNA) mimetic poly(I:C) were inhibited in replicon-bearing and WNV-infected HeLa cells. In contrast, WNV replicons did not affect IRF3 activation by Sendai virus infection, suggesting that not all IRF3 activating pathways are inhibited by WNV. Taken together, these findings demonstrate that WNV replication in cultured cells interferes with both the response to IFN and synthesis of IFN-beta in response to dsRNA.
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Affiliation(s)
- Frank Scholle
- Department of Pathology, 3.206B Mary Moody Northen Pavilion, University of Texas Medical Branch, 301 University Boulevard, Galveston, TX 77555-0436, USA
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553
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McElroy KL, Tsetsarkin KA, Vanlandingham DL, Higgs S. Characterization of an infectious clone of the wild-type yellow fever virus Asibi strain that is able to infect and disseminate in mosquitoes. J Gen Virol 2005; 86:1747-1751. [PMID: 15914853 DOI: 10.1099/vir.0.80746-0] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Infectious clone technology provides an opportunity to study the molecular basis of arthropod-virus interactions in detail. This study describes the development of an infectious clone of the prototype yellow fever virus Asibi strain (YFV-As) with the purpose of identifying sequences or domains that influence infection dynamics in the mosquito vector. The full-length cDNA of YFV-As virus was produced from RT-PCR products of parental viral RNA. These were cloned into a low-copy-number plasmid previously used to develop the YFV-17D infectious clone (pACNR/FLYF-17D). Virus recovered from the infectious clone exhibited biological characteristics similar to those of the parental YFV-As, including replication kinetics, reactivity to flavivirus cross-reactive and YFV-specific antibodies and infection and dissemination rates in Aedes aegypti, the principal mosquito vector of YFV. These data provide the basis for future studies with chimeric Asibi/17D viruses to identify the determinants of vaccine attenuation in the vector.
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Affiliation(s)
- Kate L McElroy
- Department of Pathology, University of Texas Medical Branch, Keiller 2.104, 301 University Boulevard, Galveston, TX 77555-0609, USA
| | - Konstantin A Tsetsarkin
- Department of Pathology, University of Texas Medical Branch, Keiller 2.104, 301 University Boulevard, Galveston, TX 77555-0609, USA
| | - Dana L Vanlandingham
- Department of Pathology, University of Texas Medical Branch, Keiller 2.104, 301 University Boulevard, Galveston, TX 77555-0609, USA
| | - Stephen Higgs
- Department of Pathology, University of Texas Medical Branch, Keiller 2.104, 301 University Boulevard, Galveston, TX 77555-0609, USA
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554
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Huang CYH, Silengo SJ, Whiteman MC, Kinney RM. Chimeric dengue 2 PDK-53/West Nile NY99 viruses retain the phenotypic attenuation markers of the candidate PDK-53 vaccine virus and protect mice against lethal challenge with West Nile virus. J Virol 2005; 79:7300-10. [PMID: 15919884 PMCID: PMC1143654 DOI: 10.1128/jvi.79.12.7300-7310.2005] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Chimeric dengue serotype 2/West Nile (D2/WN) viruses expressing prM-E of WN NY99 virus in the genetic background of wild-type D2 16681 virus and two candidate D2 PDK-53 vaccine variants (PDK53-E and PDK53-V) were engineered. The viability of the D2/WN viruses required incorporation of the WN virus-specific signal sequence for prM. Introduction of two mutations at M-58 and E-191 in the chimeric cDNA clones further improved the viability of the chimeras constructed in all three D2 carriers. Two D2/WN chimeras (D2/WN-E2 and -V2) engineered in the backbone of the PDK53-E and -V viruses retained all of the PDK-53 vaccine characteristic phenotypic markers of attenuation and were immunogenic in mice and protected mice from a high-dose 10(7) PFU challenge with wild-type WN NY99 virus. This report further supports application of the genetic background of the D2 PDK-53 virus as a carrier for development of live-attenuated, chimeric flavivirus vaccines in general and the development of a chimeric D2/WN vaccine virus against WN disease in particular.
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Affiliation(s)
- Claire Y-H Huang
- Division of Vector-Borne Infectious Diseases, Centers for Disease Control and Prevention, P.O. Box 2087, Fort Collins, CO 80522, USA.
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555
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Yon C, Teramoto T, Mueller N, Phelan J, Ganesh VK, Murthy KHM, Padmanabhan R. Modulation of the nucleoside triphosphatase/RNA helicase and 5'-RNA triphosphatase activities of Dengue virus type 2 nonstructural protein 3 (NS3) by interaction with NS5, the RNA-dependent RNA polymerase. J Biol Chem 2005; 280:27412-9. [PMID: 15917225 DOI: 10.1074/jbc.m501393200] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Dengue virus type 2 (DEN2), a member of the Flaviviridae family, is a re-emerging human pathogen of global significance. DEN2 nonstructural protein 3 (NS3) has a serine protease domain (NS3-pro) and requires the hydrophilic domain of NS2B (NS2BH) for activation. NS3 is also an RNA-stimulated nucleoside triphosphatase (NTPase)/RNA helicase and a 5'-RNA triphosphatase (RTPase). In this study the first biochemical and kinetic properties of full-length NS3 (NS3FL)-associated NTPase, RTPase, and RNA helicase are presented. The NS3FL showed an enhanced RNA helicase activity compared with the NS3-pro-minus NS3, which was further enhanced by the presence of the NS2BH (NS2BH-NS3FL). An active protease catalytic triad is not required for the stimulatory effect, suggesting that the overall folding of the N-terminal protease domain contributes to this enhancement. In DEN2-infected mammalian cells, NS3 and NS5, the viral 5'-RNA methyltransferase/polymerase, exist as a complex. Therefore, the effect of NS5 on the NS3 NTPase activity was examined. The results show that NS5 stimulated the NS3 NTPase and RTPase activities. The NS5 stimulation of NS3 NTPase was dose-dependent until an equimolar ratio was reached. Moreover, the conserved motif, 184RKRK, of NS3 played a crucial role in binding to RNA substrate and modulating the NTPase/RNA helicase and RTPase activities of NS3.
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Affiliation(s)
- Changsuek Yon
- Department of Microbiology and Immunology, Georgetown University School of Medicine, Washington D. C. 20057, USA
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556
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Kinney RM, Huang CYH, Rose BC, Kroeker AD, Dreher TW, Iversen PL, Stein DA. Inhibition of dengue virus serotypes 1 to 4 in vero cell cultures with morpholino oligomers. J Virol 2005; 79:5116-28. [PMID: 15795296 PMCID: PMC1069583 DOI: 10.1128/jvi.79.8.5116-5128.2005] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Five dengue (DEN) virus-specific R5F2R4 peptide-conjugated phosphorodiamidate morpholino oligomers (P4-PMOs) were evaluated for their ability to inhibit replication of DEN virus serotype 2 (DEN-2 virus) in mammalian cell culture. Initial growth curves of DEN-2 virus 16681 were obtained in Vero cells incubated with 20 microM P4-PMO compounds. At 6 days after infection, a P4-PMO targeting the 3'-terminal nucleotides of the DEN-2 virus genome and a random-sequence P4-PMO showed relatively little suppression of DEN-2 virus titer (0.1 and 0.9 log10, respectively). P4-PMOs targeting the AUG translation start site region of the single open reading frame and the 5' cyclization sequence region had moderate activity, generating 1.6- and 1.8-log10 reductions. Two P4-PMO compounds, 5'SL and 3'CS (targeting the 5'-terminal nucleotides and the 3' cyclization sequence region, respectively), were highly efficacious, each reducing the viral titer by greater than 5.7 log10 compared to controls at 6 days after infection with DEN-2 virus. Further experiments showed that 5'SL and 3'CS inhibited DEN-2 virus replication in a dose-dependent and sequence-specific manner. Treatment with 10 microM 3'CS reduced the titers of all four DEN virus serotypes, i.e., DEN-1 (strain 16007), DEN-2 (16681), DEN-3 (16562), and DEN-4 (1036) viruses by over 4 log10, in most cases to below detectable limits. The extent of 3'CS efficacy was affected by the timing of compound application in relation to viral infection of the cells. The 5'SL and 3'CS P4-PMOs did not suppress the replication of West Nile virus NY99 in Vero cells. These data indicate that further evaluation of the 5'SL and 3'CS compounds as potential DEN virus therapeutics is warranted.
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Affiliation(s)
- Richard M Kinney
- Division of Vector-Borne Infectious Diseases, Centers for Disease Control and Prevention, Public Health Service, U.S. Department of Health and Human Services, Fort Collins, Colorado, USA
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557
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Horscroft N, Lai VCH, Cheney W, Yao N, Wu JZ, Hong Z, Zhong W. Replicon cell culture system as a valuable tool in antiviral drug discovery against hepatitis C virus. Antivir Chem Chemother 2005; 16:1-12. [PMID: 15739617 DOI: 10.1177/095632020501600101] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Discovery of potential therapeutics against hepatitis C virus (HCV) infection has been hampered in the past decade by the inability to grow this virus in tissue culture and by the lack of robust small animal models. This situation has been improved by the recent development of a selectable HCV replicon cell culture system. For the first time, drug discovery scientists are able to screen large compound collections using the replicon cell culture system to identify small molecules with the potential to inhibit HCV RNA replication. The replicon system has also been used to elucidate inhibitors' antiviral mechanism of action and to optimize antiviral potency. In this review, we will summarize the recent development of HCV replicon cell culture system and its use in anti-HCV drug discovery. The antiviral activities of promising lead compounds are also reviewed.
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Affiliation(s)
- Nigel Horscroft
- Drug Discovery, Valeant Pharmaceuticals International, Costa Mesa, CA, USA
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558
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Grassmann CW, Yu H, Isken O, Behrens SE. Hepatitis C virus and the related bovine viral diarrhea virus considerably differ in the functional organization of the 5' non-translated region: implications for the viral life cycle. Virology 2005; 333:349-66. [PMID: 15721367 DOI: 10.1016/j.virol.2005.01.007] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2004] [Revised: 12/04/2004] [Accepted: 01/07/2005] [Indexed: 01/26/2023]
Abstract
The 5' non-translated regions (5'NTRs) of hepatitis C virus (HCV) and bovine viral diarrhea virus (BVDV) initiate translation of the viral RNA genome through an internal ribosomal entry site (IRES) and operate as major determinants of the RNA replication cycle. We report on comparative studies with both virus systems demonstrating that the functional organization of the 5'NTRs of HCV and BVDV shows evident differences despite a similar RNA structure. In the BVDV 5'NTR, replication signals are restricted to the 5' terminal domain I. With HCV, we defined specific replication signals in domain I but also in domains II and III that constitute the functional IRES. While the BVDV domain I supports IRES activity, the HCV domain I appears to down-regulate IRES function. These data suggest that HCV and BVDV apply different mechanisms to coordinate viral protein and RNA synthesis, which may explain differences in the replication efficiency of both related viruses.
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Affiliation(s)
- Claus Wilhelm Grassmann
- Institute for Virology, Justus-Liebig-Universität Giessen, Frankfurter Street 107, 35392 Giessen, Germany
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559
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Horscroft N, Bellows D, Ansari I, Lai VCH, Dempsey S, Liang D, Donis R, Zhong W, Hong Z. Establishment of a subgenomic replicon for bovine viral diarrhea virus in Huh-7 cells and modulation of interferon-regulated factor 3-mediated antiviral response. J Virol 2005; 79:2788-96. [PMID: 15708997 PMCID: PMC548457 DOI: 10.1128/jvi.79.5.2788-2796.2005] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
We describe the development of a selectable, bi-cistronic subgenomic replicon for bovine viral diarrhea virus (BVDV) in Huh-7 cells, similar to that established for hepatitis C virus (HCV). The selection marker and reporter (Luc-Ubi-Neo) in the BVDV replicon was fused with the amino-terminal protease N(pro), and expression of the nonstructural proteins (NS3 to NS5B) was driven by an encephalomyocarditis virus internal ribosome entry site. This BVDV replicon allows us to compare RNA replication of these two related viruses in a similar cellular background and to identify antiviral molecules specific for HCV RNA replication. The BVDV replicon showed similar sensitivity as the HCV replicon to interferons (alpha, beta, and gamma) and 2'-beta-C-methyl ribonucleoside inhibitors. Known nonnucleoside inhibitor molecules specific for either HCV or BVDV can be easily distinguished by using the parallel replicon systems. The HCV replicon has been shown to block, via the NS3/4A serine protease, Sendai virus-induced activation of interferon regulatory factor 3 (IRF-3), a key antiviral signaling molecule. Similar suppression of IRF-3-mediated responses was also observed with the Huh-7-BVDV replicon but was independent of NS3/4A protease activity. Instead, the amino-terminal cysteine protease N(pro) of BVDV appears to be, at least partly, responsible for suppressing IRF-3 activation induced by Sendai virus infection. This result suggests that different viruses, including those closely related, may have developed unique mechanisms for evading host antiviral responses. The parallel BVDV and HCV replicon systems provide robust counterscreens to distinguish viral specificity of small-molecule inhibitors of viral replication and to study the interactions of the viral replication machinery with the host cell innate immune system.
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Affiliation(s)
- Nigel Horscroft
- Valeant Pharmaceuticals International, 3300 Hyland Ave., Costa Mesa, CA 92626, USA
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560
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Mukhopadhyay S, Kuhn RJ, Rossmann MG. A structural perspective of the flavivirus life cycle. Nat Rev Microbiol 2005; 3:13-22. [PMID: 15608696 DOI: 10.1038/nrmicro1067] [Citation(s) in RCA: 838] [Impact Index Per Article: 44.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Dengue, Japanese encephalitis, West Nile and yellow fever belong to the Flavivirus genus, which is a member of the Flaviviridae family. They are human pathogens that cause large epidemics and tens of thousands of deaths annually in many parts of the world. The structural organization of these viruses and their associated structural proteins has provided insight into the molecular transitions that occur during the viral life cycle, such as assembly, budding, maturation and fusion. This review focuses mainly on structural studies of dengue virus.
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Affiliation(s)
- Suchetana Mukhopadhyay
- Department of Biological Sciences, Purdue University, 915 West State Street, West Lafayette, Indiana 47907-2054, USA
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561
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Dokland T, Walsh M, Mackenzie JM, Khromykh AA, Ee KH, Wang S. West Nile virus core protein; tetramer structure and ribbon formation. Structure 2004; 12:1157-63. [PMID: 15242592 PMCID: PMC7173237 DOI: 10.1016/j.str.2004.04.024] [Citation(s) in RCA: 137] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2004] [Revised: 04/05/2004] [Accepted: 04/06/2004] [Indexed: 02/07/2023]
Abstract
We have determined the crystal structure of the core (C) protein from the Kunjin subtype of West Nile virus (WNV), closely related to the NY99 strain of WNV, currently a major health threat in the U.S. WNV is a member of the Flaviviridae family of enveloped RNA viruses that contains many important human pathogens. The C protein is associated with the RNA genome and forms the internal core which is surrounded by the envelope in the virion. The C protein structure contains four alpha helices and forms dimers that are organized into tetramers. The tetramers form extended filamentous ribbons resembling the stacked alpha helices seen in HEAT protein structures.
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Affiliation(s)
- Terje Dokland
- Institute of Molecular and Cell Biology, Singapore, Republic of Singapore.
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