bluuebunny/crossref_metadata_2025_split huggingface dataset:
The IRF-3 Transcription Factor Mediates Sendai Virus-Induced Apoptosis
Authors: Heylbroeck Christophe , Balachandran Siddharth , Servant Marc J. , DeLuca Carmela , Barber Glen N. , Lin Rongtuan , Hiscott John 
Published: July 2002

ABSTRACT
Virus infection of target cells can result in different biological outcomes: lytic infection, cellular transformation, or cell death by apoptosis. Cells respond to virus infection by the activation of specific transcription factors involved in cytokine gene regulation and cell growth control. The ubiquitously expressed interferon regulatory factor 3 (IRF-3) transcription factor is directly activated following virus infection through posttranslational modification. Phosphorylation of specific C-terminal serine residues results in IRF-3 dimerization, nuclear translocation, and activation of DNA-binding and transactivation potential. Once activated, IRF-3 transcriptionally up regulates alpha/beta interferon genes, the chemokine RANTES, and potentially other genes that inhibit viral infection. We previously generated constitutively active [IRF-3(5D)] and dominant negative (IRF-3 ΔN) forms of IRF-3 that control target gene expression. In an effort to characterize the growth regulatory properties of IRF-3, we observed that IRF-3 is a mediator of paramyxovirus-induced apoptosis. Expression of the constitutively active form of IRF-3 is toxic, preventing the establishment of stably transfected cells. By using a tetracycline-inducible system, we show that induction of IRF-3(5D) alone is sufficient to induce apoptosis in human embryonic kidney 293 and human Jurkat T cells as measured by DNA laddering, terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling assay, and analysis of DNA content by flow cytometry. Wild-type IRF-3 expression augments paramyxovirus-induced apoptosis, while expression of IRF-3 ΔN blocks virus-induced apoptosis. In addition, we demonstrate an important role of caspases 8, 9, and 3 in IRF-3-induced apoptosis. These results suggest that IRF-3, in addition to potently activating cytokine genes, regulates apoptotic signalling following virus infection.
Clinical Isolates of Measles Virus Use CD46 as a Cellular Receptor
Authors: Manchester Marianne , Eto Danelle S. , Valsamakis Alexandra , Liton Paloma B. , Fernandez-Muñoz Rafael , Rota Paul A. , Bellini William J. , Forthal Donald N. , Oldstone Michael B. A. 
Published: July 2002

ABSTRACTLaboratory strains of measles viruses (MV), such as Edmonston and Halle, use the complement regulatory protein CD46 as a cell surface receptor. The receptor usage of clinical isolates of MV, however, remains unclear. Receptor usage by primary patient isolates of MV was compared to isolates that had been passaged on a variety of tissue culture cell lines. All of the isolates could infect cells in a CD46-dependent manner, but their tropism was restricted according to cell type (e.g., lymphocytes versus fibroblasts). The results indicate that patient isolates that have not been adapted to tissue culture cell lines use CD46 as a receptor. In addition, passaging primary MV patient isolates in B95-8 cells selected variants that had alternate receptor usage compared to the original isolate. Thus, changes in receptor usage by MV are dependent upon the cell type used for isolation. Furthermore, our results confirm the relevance of the CD46 receptor to natural measles infection.
Isolation and Characterization of an Equine Foamy Virus
Authors: Tobaly-Tapiero Joelle , Bittoun Patricia , Neves Manuel , Guillemin Marie-Claude , Lecellier Charles-Henri , Puvion-Dutilleul Francine , Gicquel Bernard , Zientara Stephan , Giron Marie-Louise , de Thé Hugues , Saïb Ali 
Published: July 2002

ABSTRACT
Foamy viruses (FVs) are complex retroviruses which have been isolated from different animal species including nonhuman primates, cattle, and cats. Here, we report the isolation and characterization of a new FV isolated from blood samples of horses. Similar to other FVs, the equine foamy virus (EFV) exhibits a highly characteristic ultrastructure and induces syncytium formation and subsequent cell lysis on a large number of cell lines. Molecular cloning of EFV reveals that the general organization is that of other known FVs, whereas sequence similarity with its bovine FV counterpart is only 40%. Interestingly, EFV buds exclusively from the plasma membrane and not from the endoplasmic reticulum (ER), as previously shown for other FVs. The absence of the ER retrieval dilysine motif in EFV Env is likely responsible for this unexpected sorting pathway.
Virus-Specific Cofactor Requirement and Chimeric Hepatitis C Virus/GB Virus B Nonstructural Protein 3
Authors: Butkiewicz Nancy , Yao Nanhua , Zhong Weidong , Wright-Minogue Jacquelyn , Ingravallo Paul , Zhang Rumin , Durkin James , Standring David N. , Baroudy Bahige M. , Sangar David V. , Lemon Stanley M. , Lau Johnson Y. N. , Hong Zhi 
Published: July 2002

ABSTRACT

GB virus B (GBV-B) is closely related to hepatitis C virus (HCV) and causes acute hepatitis in tamarins (
Saguinus
species), making it an attractive surrogate virus for in vivo testing of anti-HCV inhibitors in a small monkey model. It has been reported that the nonstructural protein 3 (NS3) serine protease of GBV-B shares similar substrate specificity with its counterpart in HCV. Authentic proteolytic processing of the HCV polyprotein junctions (NS4A/4B, NS4B/5A, and NS5A/5B) can be accomplished by the GBV-B NS3 protease in an HCV NS4A cofactor-independent fashion. We further characterized the protease activity of a full-length GBV-B NS3 protein and its cofactor requirement using in vitro-translated GBV-B substrates. Cleavages at the NS4A/4B and NS5A/5B junctions were readily detectable only in the presence of a cofactor peptide derived from the central region of GBV-B NS4A. Interestingly, the GBV-B substrates could also be cleaved by the HCV NS3 protease in an HCV NS4A cofactor-dependent manner, supporting the notion that HCV and GBV-B share similar NS3 protease specificity while retaining a virus-specific cofactor requirement. This finding of a strict virus-specific cofactor requirement is consistent with the lack of sequence homology in the NS4A cofactor regions of HCV and GBV-B. The minimum cofactor region that supported GBV-B protease activity was mapped to a central region of GBV-B NS4A (between amino acids Phe22 and Val36) which overlapped with the cofactor region of HCV. Alanine substitution analysis demonstrated that two amino acids, Val27 and Trp31, were essential for the cofactor activity, a finding reminiscent of the two critical residues in the HCV NS4A cofactor, Ile25 and Ile29. A model for the GBV-B NS3 protease domain and NS4A cofactor complex revealed that GBV-B might have developed a similar structural strategy in the activation and regulation of its NS3 protease activity. Finally, a chimeric HCV/GBV-B bifunctional NS3, consisting of an N-terminal HCV protease domain and a C-terminal GBV-B RNA helicase domain, was engineered. Both enzymatic activities were retained by the chimeric protein, which could lead to the development of a chimeric GBV-B virus that depends on HCV protease function.
A Mutation in Human Immunodeficiency Virus Type 1 Protease, N88S, That Causes In Vitro Hypersensitivity to Amprenavir
Authors: Ziermann Rainer , Limoli Kay , Das Kalyan , Arnold Edward , Petropoulos Christos J. , Parkin Neil T. 
Published: July 2002

ABSTRACT
Amprenavir (Agenerase, 141-W94, VX-478) is a human immunodeficiency virus type 1 (HIV-1) protease inhibitor (PRI) recently approved for the treatment of HIV-1 infection in the United States. A major cause of treatment failure is the development of resistance to PRIs. One potential use for amprenavir is as salvage therapy for patients for whom treatment that includes one (or more) of the other four currently approved PRIs—saquinavir, indinavir, ritonavir, and nelfinavir—has failed. We evaluated the cross-resistance to amprenavir of viruses that evolved during treatment with the two most commonly prescribed PRIs, nelfinavir and indinavir. Unexpectedly, a dramatic increase in susceptibility (2.5- to 12.5-fold) was observed with 20 of 312 (6.4%) patient viruses analyzed. The most pronounced increases in susceptibility were strongly associated with an N88S mutation in protease. All viruses that carried the N88S mutation were hypersensitive to amprenavir. Site-directed mutagenesis studies confirmed the causal role of N88S in determining amprenavir hypersensitivity. The presence of the N88S mutation and associated amprenavir hypersensitivity may be useful in predicting an improved clinical response to amprenavir salvage therapy.
Cooperative Transformation and Coexpression of Bovine Papillomavirus Type 1 E5 and E7 Proteins
Authors: Bohl Joanna , Hull Bruce , Vande Pol Scott B. 
Published: July 2002

ABSTRACT
Productively infected bovine fibropapillomas were examined for bovine papillomavirus type 1 (BPV-1) E7 localization. BPV-1 E7 was observed in the cytoplasm of basal and lower spinous epithelial cells, coexpressed in the cytoplasm of basal cells with the E5 oncoprotein. E7 was also observed in nucleoli throughout the basal and spinous layers but not in the granular cell layer. Ectopic expression of E7 in cultured epithelial cells gave rise to localization similar to that seen in productive fibropapillomas, with cytoplasmic and nucleolar expression observed. Consistent with the coexpression of E7 and E5 in basal keratinocytes, BPV-1 E7 cooperated with E5 as well as E6 in an anchorage independence transformation assay. While E5 is expressed in both basal and superficial differentiating keratinocytes, BPV-1 E7 is only observed in basal and lower spinous epithelial cells. Therefore, BPV-1 E7 may serve to modulate the cellular response of basal epithelial cells to E5 expression.
Kinetics of Murine Gammaherpesvirus 68 Gene Expression following Infection of Murine Cells in Culture and in Mice
Authors: Rochford Rosemary , Lutzke Mary L. , Alfinito Rosiane S. , Clavo Anaira , Cardin Rhonda D. 
Published: July 2002

ABSTRACTA model system to study the pathogenesis of gammaherpesvirus infections is the infection of mice with murine gammaherpesvirus 68 (MHV-68). To define the kinetics of infection, we developed an RNase protection assay to quantitate gene expression from lytic (K3, Rta, M8, DNA polymerase [DNA pol], and gB) and candidate latency (M2, M3, M9, M11, ORF73, and ORF74) genes. All candidate latency genes were expressed during lytic infection of 3T3 cells. Four kinetic classes of transcripts were observed following infection of 3T3 cells: immediate-early (K3, Rta, M8, and ORF73), early (DNA pol), early-late (M3, M11, and ORF74), and late (M2, M9, and gB). To assess the kinetics of viral gene expression in vivo, lungs, spleens, and mediastinal lymph nodes (MLN) were harvested from MHV-68-infected mice. All transcripts were expressed between 3 and 6 days postinfection (dpi) in the lungs. In the spleen, K3, M3, M8, and M9 transcripts were expressed between 10 and 16 dpi when latency is established. The K3, M3, M8, M9, and M11 transcripts were detected in the MLN from 2 through 16 dpi. This is the first demonstration of MHV-68 gene expression in the MLN. Importantly, our data showed that MHV-68 has different kinetics of gene expression at different sites of infection. Furthermore, we demonstrated that K3, a gene recently shown to encode a protein that downregulates major histocompatibility complex class I on the surface of cells, is expressed during latency, which argues for a role of K3 in immune evasion during latent infection.
Transactivation of Murine Cyclin A by Polyomavirus Large and Small T Antigens
Authors: Schüchner Stefan , Nemethova Maria , Belisova Aurelia , Klucky Britta , Holnthoner Wolfgang , Wintersberger Erhard 
Published: July 2002

ABSTRACT
Polyomavirus large and small T antigens cooperate in the induction of S phase in serum-deprived Swiss 3T3 cells. While the large T antigen is able to induce S phase-specific enzymes, we have recently shown that both T antigens contribute to the production of the cyclins E and A and that the small T antigen is essential for the induction of cyclin A-dependent cdk2 activity (S. Schüchner and E. Wintersberger, J. Virol. 73:9266–9273, 1999). Here we present our attempts to elucidate the mechanisms by which the large and the small T antigens transactivate the murine cyclin A gene. Using Swiss 3T3 cells carrying the T antigens and various mutants thereof under the hormone-inducible mouse mammary tumor virus promoter, as well as transient-cotransfection experiments with the T antigens and cyclin A promoter-luciferase reporter constructs, we found the following. The large T antigen activates the cyclin A promoter via two transcription factor binding sites, a cyclic AMP responsive element (CRE), and the major negative regulatory site called CDE-CHR. While an intact binding site for pocket proteins is required for the function of this T antigen at the CDE-CHR, its activity at the CRE is largely independent thereof. In contrast, an intact J domain and an intact zinc finger are required at both sites. The small T antigen also appears to have an influence on the cyclin A promoter through the CRE as well as the CDE-CHR. For this an interaction with protein phosphatase 2A is essential; mutation of the J domain does not totally eliminate but greatly reduces the transactivating ability.
Replication of Phenotypically Mixed Human Immunodeficiency Virus Type 1 Virions Containing Catalytically Active and Catalytically Inactive Reverse Transcriptase
Authors: Julias John G. , Ferris Andrea L. , Boyer Paul L. , Hughes Stephen H. 
Published: July 2002

ABSTRACT
The amount of excess polymerase and RNase H activity in human immunodeficiency virus type 1 virions was measured by using vectors that undergo a single round of replication. Vectors containing wild-type reverse transcriptase (RT), vectors encoding the D110E mutation to inactivate polymerase, and vectors encoding mutations D443A and E478Q to inactivate RNase H were constructed. 293 cells were cotransfected with different proportions of plasmids encoding these vectors to generate phenotypically mixed virions. The resulting viruses were used to infect human osteosarcoma cells, and the relative infectivity of the viruses was determined by measuring transduction of the murine cell surface marker CD24, which is encoded by the vectors. The results indicated that there is an excess of both polymerase and RNase H activities in virions. Viral replication was reduced to 42% of wild-type levels in virions with where half of the RT molecules were predicted to be catalytically active but dropped to 3% of wild-type levels when 25% of the RT molecules were active. However, reducing RNase H activity had a lesser effect on viral replication. As expected, based on previous work with murine leukemia virus, there was relatively inefficient virus replication when the RNase H and polymerase activities were encoded on separate vectors (D110E plus E478Q and D110E plus D443A). To determine how virus replication failed when polymerase and RNase H activities were reduced, reverse transcription intermediates were measured in vector-infected cells by using quantitative real-time PCR. The results indicated that using the D11OE mutation to reduce the amount of active polymerase reduced the number of reverse transcripts that were initiated and also reduced the amounts of products from the late stages of reverse transcription. If the E478Q mutation was used to reduce RNase H activity, the number of reverse transcripts that were initiated was reduced; there was also a strong effect on minus-strand transfer.
Immunoglobulin G3 from Polyclonal Human Immunodeficiency Virus (HIV) Immune Globulin Is More Potent than Other Subclasses in Neutralizing HIV Type 1
Authors: Scharf Orit , Golding Hana , King Lisa R. , Eller Nancy , Frazier Doug , Golding Basil , Scott Dorothy E. 
Published: July 2002

ABSTRACTPassive antibody prophylaxis against human immunodeficiency virus type 1 (HIV-1) has been accomplished in primates, suggesting that this strategy may prove useful in humans. While antibody specificity is crucial for neutralization, other antibody characteristics, such as subclass, have not been explored. Our objective was to compare the efficiencies of immunoglobulin G (IgG) subclasses from polyclonal human HIV immune globulin (HIVIG) in the neutralization of HIV-1 strains differing in coreceptor tropism. IgG1, IgG2, and IgG3 were enriched from HIVIG by using protein A-Sepharose. All three subclasses bound major HIV-1 proteins, as shown by Western blot assay and enzyme-linked immunosorbent assay. In HIV-1 fusion assays using X4, R5, or X4R5 envelope-expressing effector cells, IgG3 more efficiently blocked fusion. In neutralization assays with cell-free viruses using X4 (LAI, IIIB), R5 (BaL), and X4R5 (DH123), a similar hierarchy of neutralization was found: IgG3 > IgG1 > IgG2. IgG3 has a longer, more flexible hinge region than the other subclasses. To test whether this is important, IgG1 and IgG3 were digested with pepsin to generate F(ab′)2fragments or with papain to generate Fab fragments. IgG3 F(ab′)2fragments were still more efficient in neutralization than F(ab′)2of IgG1. However, Fab fragments of IgG3 and IgG1 demonstrated equivalent neutralization capacities and the IgG3 advantage was lost. These results suggest that the IgG3 hinge region confers enhanced HIV-neutralizing ability. Enrichment and stabilization of IgG3 may therefore lead to improved HIVIG preparations. The results of this study have implications for the improvement of passive immunization with polyclonal or monoclonal antibodies and suggest that HIV-1 vaccines which induce high-titer IgG3 responses could be advantageous.
DNA Microarray Analysis of Chimpanzee Liver during Acute Resolving Hepatitis C Virus Infection
Authors: Bigger Catherine B. , Brasky Kathleen M. , Lanford Robert E. 
Published: July 2002

ABSTRACTHepatitis C virus (HCV) poses a worldwide health problem in that the majority of individuals exposed to HCV become chronically infected and are predisposed for developing significant liver disease. DNA microarray technology provides an opportunity to survey transcription modulation in the context of an infectious disease and is a particularly attractive approach in characterizing HCV-host interactions, since the mechanisms underlying viral persistence and disease progression are not understood and are difficult to study. Here, we describe the changes in liver gene expression during the course of an acute-resolving HCV infection in a chimpanzee. Clearance of viremia in this animal occurred between weeks 6 and 8, while clearance of residual infected hepatocytes did not occur until 14 weeks postinfection. The most notable changes in gene expression occurred in numerous interferon response genes (including all three classical interferon antiviral pathways) that increased dramatically, some as early as day 2 postinfection. The data suggest a biphasic mechanism of viral clearance dependent on both the innate and adaptive immune responses and provide insight into the response of the liver to a hepatotropic viral infection.
Interferon-Independent, Human Immunodeficiency Virus Type 1 gp120-Mediated Induction of CXCL10/IP-10 Gene Expression by Astrocytes In Vivo and In Vitro
Authors: Asensio Valérie C. , Maier Joachim , Milner Richard , Boztug Kaan , Kincaid Carrie , Moulard Maxime , Phillipson Curtis , Lindsley Kristen , Krucker Thomas , Fox Howard S. , Campbell Iain L. 
Published: July 2002

ABSTRACTThe CXC chemokine gamma interferon (IFN-γ)-inducible protein CXCL10/IP-10 is markedly elevated in cerebrospinal fluid and brain of individuals infected with human immunodeficiency virus type 1 (HIV-1) and is implicated in the pathogenesis of HIV-associated dementia (HAD). To explore the possible role of CXCL10/IP-10 in HAD, we examined the expression of this and other chemokines in the central nervous system (CNS) of transgenic mice with astrocyte-targeted expression of HIV gp120 under the control of the glial fibrillary acidic protein (GFAP) promoter, a murine model for HIV-1 encephalopathy. Compared with wild-type controls, CNS expression of the CC chemokine gene CCL2/MCP-1 and the CXC chemokine genes CXCL10/IP-10 and CXCL9/Mig was induced in the GFAP-HIV gp120 mice. CXCL10/IP-10 RNA expression was increased most and overlapped the expression of the transgene-encoded HIV gp120 gene. Astrocytes and to a lesser extent microglia were identified as the major cellular sites for CXCL10/IP-10 gene expression. There was no detectable expression of any class of IFN or their responsive genes. In astrocyte cultures, soluble recombinant HIV gp120 protein was capable of directly inducing CXCL10/IP-10 gene expression a process that was independent of STAT1. These findings highlight a novel IFN- and STAT1-independent mechanism for the regulation of CXCL10/IP-10 expression and directly link expression of HIV gp120 to the induction of CXCL10/IP-10 that is found in HIV infection of the CNS. Finally, one function of IP-10 expression may be the recruitment of leukocytes to the CNS, since the brain of GFAP-HIV gp120 mice had increased numbers of CD3+T cells that were found in close proximity to sites of CXCL10/IP-10 RNA expression.
Identification of Key Amino Acids of the Mouse Mammary Tumor Virus Superantigen Involved in the Specific Interaction with T-Cell Receptor VβDomains
Authors: Baribaud Frédéric , Wirth Susanne , Maillard Ivan , Valsesia Sandrine , Acha-Orbea Hans , Diggelmann Heidi 
Published: July 2002

ABSTRACTMouse mammary tumor virus (MMTV) is a retrovirus encoding a superantigen that is recognized in association with major histocompatibility complex class II by the variable region of the beta chain (Vβ) of the T-cell receptor. The C-terminal 30 to 40 amino acids of the superantigen of different MMTVs display high sequence variability that correlates with the recognition of particular T-cell receptor Vβchains. Interestingly, MMTV(SIM) andmtv-8superantigens are highly homologous but have nonoverlapping T-cell receptor Vβspecificities. To determine the importance of these few differences for specific Vβinteraction, we studied superantigen responses in mice to chimeric and mutant MMTV(SIM) andmtv-8superantigens expressed by recombinant vaccinia viruses. We show that only a few changes (two to six residues) within the C terminus are necessary to modify superantigen recognition by specific Vβs. Thus, the introduction of the MMTV(SIM) residues 314-315 into themtv-8superantigen greatly decreased its Vβ12 reactivity without gain of MMTV(SIM)-specific function. The introduction of MMTV(SIM)-specific residues 289 to 295, however, induced a recognition pattern that was a mixture of MMTV(SIM)- andmtv-8-specific Vβreactivities: both weak MMTV(SIM)-specific Vβ4 and fullmtv-8-specific Vβ11 recognition were observed while Vβ12 interaction was lost. The combination of the two MMTV(SIM)-specific regions in themtv-8superantigen established normal MMTV(SIM)-specific Vβ4 reactivity and completely abolishedmtv-8-specific Vβ5, -11, and -12 interactions. These new functional superantigens with mixed Vβrecognition patterns allowed us to precisely delineate sites relevant for molecular interactions between the SIM ormtv-8superantigen and the T-cell receptor Vβdomain within the 30 C-terminal residues of the viral superantigen.
Retroviral Splicing Suppressor Requires Three Nonconsensus Uridines in a 5′ Splice Site-Like Sequence
Authors: Paca Robert E. , Hibbert Catherine S. , O'Sullivan Christopher T. , Beemon Karen L. 
Published: July 2002

ABSTRACT
Rous sarcoma virus RNA contains a negative regulator of splicing (NRS) element that aids in maintenance of unspliced RNA. The NRS binds U1 snRNA at a sequence that deviates from the 5′ splice site consensus by substitution of U's for A's at three positions: −2, +3, and +4. All three of these U's are important for NRS-mediated splicing suppression. Substitution of a single nonconsensus C or G at any of these sites diminished NRS activity, whereas substitution of a single A generated a preferred 5′ splice site within the NRS.