bluuebunny/crossref_metadata_2025_split huggingface dataset:
Salicylates Inhibit Flavivirus Replication Independently of Blocking Nuclear Factor Kappa B Activation
Authors: Liao Ching-Len , Lin Yi-Ling , Wu Bi-Ching , Tsao Chang-Huei , Wang Mei-Chuan , Liu Chiu-I , Huang Yue-Ling , Chen Jui-Hui , Wang Jia-Pey , Chen Li-Kuang 
Published: July 2002

ABSTRACTFlaviviruses comprise a positive-sense RNA genome that replicates exclusively in the cytoplasm of infected cells. Whether flaviviruses require an activated nuclear factor(s) to complete their life cycle and trigger apoptosis in infected cells remains elusive. Flavivirus infections quickly activate nuclear factor kappa B (NF-κB), and salicylates have been shown to inhibit NF-κB activation. In this study, we investigated whether salicylates suppress flavivirus replication and virus-induced apoptosis in cultured cells. In a dose-dependent inhibition, we found salicylates within a range of 1 to 5 mM not only restricted flavivirus replication but also abrogated flavivirus-triggered apoptosis. However, flavivirus replication was not affected by a specific NF-κB peptide inhibitor, SN50, and a proteosome inhibitor, lactacystin. Flaviviruses also replicated and triggered apoptosis in cells stably expressing IκBα-ΔN, a dominant-negative mutant that antagonizes NF-κB activation, as readily as in wild-type BHK-21 cells, suggesting that NF-κB activation is not essential for either flavivirus replication or flavivirus-induced apoptosis. Salicylates still diminished flavivirus replication and blocked apoptosis in the same IκBα-ΔN cells. This inhibition of flaviviruses by salicylates could be partially reversed by a specific p38 mitogen-activated protein (MAP) kinase inhibitor, SB203580. Together, these results show that the mechanism by which salicylates suppress flavivirus infection may involve p38 MAP kinase activity but is independent of blocking the NF-κB pathway.
Activation of Interferon Response Factor-3 in Human Cells Infected with Herpes Simplex Virus Type 1 or Human Cytomegalovirus
Authors: Preston Chris M. , Harman Andrew N. , Nicholl Mary Jane 
Published: July 2002

ABSTRACTActivation of cellular interferon-stimulated genes (ISGs) after infection with herpes simplex virus type 1 (HSV-1) or human cytomegalovirus (HCMV) was investigated. The level of ISG54-specific RNA in human fetal lung (HFL) or human foreskin (BJ) fibroblasts increased substantially after infection with either virus in the presence of cycloheximide. HSV-1 particles lacking glycoprotein D or glycoprotein H failed to induce ISG54-specific RNA synthesis, demonstrating that entry of virus particles rather than binding of virions to the cell surface was required for the effect. A DNA-binding complex that recognized an interferon-responsive sequence motif was induced upon infection with HSV-1 or HCMV in the presence of cycloheximide, and the complex was shown to contain the cell proteins interferon response factor 3 (IRF-3) and CREB-binding protein. IRF-3 was modified after infection with HSV-1 or HCMV to a form of lower electrophoretic mobility, consistent with phosphorylation. De novo transcription of viral or cellular genes was not required for the activation of IRF-3, since the effect was not sensitive to inhibition by actinomycin D. Infection of HFL fibroblasts with HSV-1 under conditions in which viral replication proceeded normally resulted in severely reduced levels of the IRF-3-containing complex, defining the activation of IRF-3 as a target for viral interference with ISG induction. In BJ fibroblasts, however, significant activation of IRF-3 was detected even when the viral gene expression program progressed to later stages, demonstrating that the degree of inhibition of the response was dependent on host cell type. As a consequence of IRF-3 activation, endogenous interferon was released from BJ cells and was capable of triggering the appropriate signal transduction pathway in both infected and uninfected cells. Activation of ISG54-specific RNA synthesis was not detected after infection of human U-373MG glioblastoma cells, showing that the induction of the response by infection is cell type dependent.
Human Immunodeficiency Virus Type 1 Protease Cleavage Site Mutations Associated with Protease Inhibitor Cross-Resistance Selected by Indinavir, Ritonavir, and/or Saquinavir
Authors: Côté Hélène C. F. , Brumme Zabrina L. , Harrigan P. Richard 
Published: July 2002

ABSTRACT

We examined the prevalence of cleavage site mutations, both within and outside the
gag
region, in 28 protease inhibitor (PI) cross-resistant patients treated with indinavir, ritonavir, and/or saquinavir compared to control patients treated with reverse transcriptase inhibitors. Three human immunodeficiency virus protease cleavage sites within
gag
(p2/NC, NC/p1, and NC/TFP) showed considerable in vivo evolution before and after therapy with indinavir, ritonavir, and/or saquinavir. Another
gag
cleavage site (p1/p6

gag

) showed a trend compared to matched controls. The other eight recognized cleavage sites showed relatively little difference between PI-resistant cases and controls. An A→V substitution at the P2 position of the NC/p1 and NC/TFP cleavage sites was the most common (29%) change selected by the PIs used in this study.
Neutralizing Antibodies in Persistent Borna Disease Virus Infection: Prophylactic Effect of gp94-Specific Monoclonal Antibodies in Preventing Encephalitis
Authors: Furrer Esther , Bilzer Thomas , Stitz Lothar , Planz Oliver 
Published: July 2002

ABSTRACTBorna disease virus (BDV) infection triggers an immune-mediated encephalomyelitis and results in a persistent infection. The immune response in the acute phase of the disease is characterized by a cellular response in which CD8+T cells are responsible for the destruction of virus-infected brain cells. CD4+T cells function as helper cells and support the production of antiviral antibodies. Antibodies generated in the acute phase of the disease against the nucleoprotein and the phosphoprotein are nonneutralizing. In the chronic phase of the disease, neutralizing antibodies directed against the matrix protein and glycoprotein are synthesized. In the present work, the biological role of the neutralizing-antibody response to BDV was further investigated. By analyzing the blood of rats infected intracerebrally with BDV, a highly neurotropic virus, nucleic acid could be detected between 30 and 50 days after infection. Neutralizing antibodies were found between 60 and 100 days after infection. Furthermore, we produced hybridomas secreting BDV-specific neutralizing monoclonal antibodies. These antibodies, directed against the major glycoprotein (gp94) of BDV, were able to prevent Borna disease if given prophylactically. These data suggest that the late appearance of BDV-specific neutralizing antibodies is due to the presence of BDV in the blood of chronically infected rats. Furthermore, these antibodies have the potential to neutralize the infectious virus when given early, which is an important finding with respect to the development of a vaccine.
Isolation and Characterization of Noncytopathic Pestivirus Mutants Reveals a Role for Nonstructural Protein NS4B in Viral Cytopathogenicity
Authors: Qu Lin , McMullan Laura K. , Rice Charles M. 
Published: July 2002

ABSTRACT
Isolates of bovine viral diarrhea virus (BVDV), the prototype pestivirus, are divided into cytopathic (cp) and noncytopathic (ncp) biotypes according to their effect on cultured cells. The cp viruses also differ from ncp viruses by the production of viral nonstructural protein NS3. However, the mechanism by which cp viruses induce cytopathic effect in cell culture remains unknown. Here we used a genetic approach to isolate ncp variants that arose from a cp virus at low frequency. A bicistronic BVDV (cp strain NADL) was created that expressed puromycin acetyltransferase as a dominant selectable marker. This bicistronic virus exhibited slightly slower growth kinetics and smaller plaques than NADL but remained cp. A number of independent ncp variants were isolated by puromycin selection. Remarkably, these ncp variants produced NS3 and viral RNA at levels comparable to those of the cp parent. Sequence analyses uncovered no change in NS3, but for all ncp variants a Y2441C substitution at residue 15 of NS4B was found. Introduction of the Y2441C substitution into the NADL or bicistronic cp viruses reconstituted the ncp phenotype. Y2441 is highly conserved among pestiviruses and is located in a region of NS4B predicted to be on the cytosolic side of the endoplasmic reticulum membrane. Other engineered substitutions for Y2441 also affected viral cytopathogenicity and viability, with Y2441V being cp, Y2441A being ncp, and Y2441D rendering the virus unable to replicate. The ncp substitutions for Y2441 resulted in slightly increased levels of NS2-3 relative to NS3. We also showed that NS3, NS4B, and NS5A could be chemically cross-linked in NADL-infected cells, indicating that they are associated as components of a multiprotein complex. Although the mechanism remains to be elucidated, these results demonstrate that mutations in NS4B can attenuate BVDV cytopathogenicity despite NS3 production.
High-Dose Borna Disease Virus Infection Induces a Nucleoprotein-Specific Cytotoxic T-Lymphocyte Response and Prevention of Immunopathology
Authors: Furrer Esther , Bilzer Thomas , Stitz Lothar , Planz Oliver 
Published: July 2002

ABSTRACTExperimental Borna disease virus (BDV) infection of rats and natural infection of horses and sheep leads to severe central nervous system disease based on immunopathological pathways. The virus replicates slowly, and the cellular immune response results in immunopathology. CD8+T cells exert effector cell functions, and their activity results in the destruction of virus-infected cells. Previously, Oldach and colleagues (D. Oldach, M. C. Zink, J. M. Pyper, S. Herzog, R. Rott, O. Narayan, and J. E. Clements, Virology 206:426–434, 1995) have reported protection against Borna disease after inoculation of high-dose cell-adapted BDV. Here we show that the outcome of the infection, i.e., immunopathology versus protection, is simply dependent on the amount of virus used for infection. High-dose BDV (106FFU) triggers an early virus-specific reaction of the immune system, as demonstrated by strong cellular and humoral responses. In particular, the early presence and function of nucleoprotein-specific CD8+T cells could be demonstrated in the brain. We present evidence that in a noncytolytic and usually persistent virus infection, high-dose input virus mediates early control of the pathogen due to an efficient induction of an antiviral immune mechanism. From these data, we conclude that immune reactivity, in particular the cytotoxic T-cell response, determines whether the virus is controlled with prevention of the ensuing immunopathological disease or whether a persistent infection is established.
Herpes Simplex Virus Virion Host Shutoff Protein Requires a Mammalian Factor for Efficient In Vitro Endoribonuclease Activity
Authors: Lu Patricia , Jones Frank E. , Saffran Holly A. , Smiley James R. 
Published: July 2002

ABSTRACT

The virion host shutoff protein (vhs) of herpes simplex virus (HSV) triggers global shutoff of host protein synthesis and accelerated mRNA turnover during virus infection and induces endoribonucleolytic cleavage of exogenous RNA substrates when it is produced in a rabbit reticulocyte (RRL) in vitro translation system. Although vhs induces RNA turnover in the absence of other HSV gene products, it is not yet known whether cellular factors are required for its activity. As one approach to addressing this question, we expressed vhs in the budding yeast
Saccharomyces cerevisiae
. Expression of vhs inhibited colony formation, and the severity of this effect varied with the carbon source. The biological relevance of this effect was assessed by examining the activity of five mutant forms of vhs bearing previously characterized in-frame linker insertions. The results indicated a complete concordance between the growth inhibition phenotype in yeast and mammalian host cell shutoff. Despite these results, expression of vhs did not trigger global mRNA turnover in vivo, and cell extracts of yeast expressing vhs displayed little if any vhs-dependent endoribonuclease activity. However, activity was readily detected when such extracts were mixed with RRL. These data suggest that the vhs-dependent endoribonuclease requires one or more mammalian macromolecular factors for efficient activity.
V Domain of Human SLAM (CDw150) Is Essential for Its Function as a Measles Virus Receptor
Authors: Ono Nobuyuki , Tatsuo Hironobu , Tanaka Kotaro , Minagawa Hiroko , Yanagi Yusuke 
Published: July 2002

ABSTRACTHuman signaling lymphocytic activation molecule (SLAM; also known as CDw150) has been shown to be a cellular receptor for measles virus (MV). Chinese hamster ovary cells transfected with a mouse SLAM cDNA were not susceptible to MV and the vesicular stomatitis virus pseudotype bearing MV envelope proteins alone, indicating that mouse SLAM cannot act as an MV receptor. To determine the functional domain of the receptor, we tested the abilities of several chimeric SLAM proteins to function as MV receptors. The ectodomain of SLAM comprises the two immunoglobulin superfamily domains (V and C2). Various chimeric transmembrane proteins possessing the V domain of human SLAM were able to act as MV receptors, whereas a chimera consisting of human SLAM containing the mouse V domain instead of the human V domain no longer acted as a receptor. To examine the interaction between SLAM and MV envelope proteins, recombinant soluble forms of SLAM were produced. The soluble molecules possessing the V domain of human SLAM were shown to bind to cells expressing the MV hemagglutinin (H) protein but not to cells expressing the MV fusion protein or irrelevant envelope proteins. These results indicate that the V domain of human SLAM is necessary and sufficient to interact with the MV H protein and allow MV entry.
Detection of Infectious Baboon Cytomegalovirus after Baboon-to-Human Liver Xenotransplantation
Authors: Michaels Marian G. , Jenkins Frank J. , St. George Kirsten , Nalesnik Michael A. , Starzl Thomas E. , Rinaldo Charles R. 
Published: July 2002

ABSTRACT
Xenotransplantation is considered to be a solution for the human donor shortage. However, there is a potential risk of transmitting animal infections from the transplanted organ. The known transmissibility and clinical significance of human cytomegalovirus (HCMV) infection after allotransplantation led us to evaluate whether baboon cytomegalovirus (BCMV) transmission could occur after a baboon-to-human liver xenotransplant. We examined serial blood samples from a baboon liver recipient and isolated replication-competent CMV-like agents on days 29, 36, and 42 after xenotransplantation. BCMV and HCMV DNAs were detected in the day 29 isolate, while only HCMV DNA was detected in the other isolates. This is the first report of detecting a replication-competent virus from a source animal after xenotransplantation and is a concern with regard to potential zoonotic transmission to others.
“Hit-and-Run” Transformation by Adenovirus Oncogenes
Authors: Nevels Michael , Täuber Birgitt , Spruss Thilo , Wolf Hans , Dobner Thomas 
Published: July 2002

ABSTRACT
According to classical concepts of viral oncogenesis, the persistence of virus-specific oncogenes is required to maintain the transformed cellular phenotype. In contrast, the “hit-and-run” hypothesis claims that viruses can mediate cellular transformation through an initial “hit,” while maintenance of the transformed state is compatible with the loss (“run”) of viral molecules. It is well established that the adenovirus E1A and E1B gene products can cooperatively transform primary human and rodent cells to a tumorigenic phenotype and that these cells permanently express the viral oncogenes. Additionally, recent studies have shown that the adenovirus E4 region encodes two novel oncoproteins, the products of E4orf6 and E4orf3, which cooperate with the viral E1A proteins to transform primary rat cells in an E1B-like fashion. Unexpectedly, however, cells transformed by E1A and either E4orf6 or E4orf3 fail to express the viral E4 gene products, and only a subset contain E1A proteins. In fact, the majority of these cells lack E4- and E1A-specific DNA sequences, indicating that transformation occurred through a hit-and-run mechanism. We provide evidence that the unusual transforming activities of the adenoviral oncoproteins may be due to their mutagenic potential. Our results strongly support the possibility that even tumors that lack any detectable virus-specific molecules can be of viral origin, which could have a significant impact on the use of adenoviral vectors for gene therapy.
Region of Herpes Simplex Virus Type 1 Latency-Associated Transcript Sufficient for Wild-Type Spontaneous Reactivation Promotes Cell Survival in Tissue Culture
Authors: Inman Melissa , Perng Guey-Chuen , Henderson Gail , Ghiasi Homayon , Nesburn Anthony B. , Wechsler Steven L. , Jones Clinton 
Published: July 2002

ABSTRACT

The latency-associated transcript (LAT) is the only abundant herpes simplex virus type 1 (HSV-1) transcript expressed during latency. In the rabbit eye model, LAT null mutants do not reactivate efficiently from latency. We recently demonstrated that the LAT null mutant
d
LAT2903 induces increased levels of apoptosis in trigeminal ganglia of infected rabbits compared to LAT
+
strains (G.-C. Perng, C. Jones, J. Ciacci-Zarella, M. Stone, G. Henderson, A. Yokht, S. M. Slanina, F. M. Hoffman, H. Ghiasi, A. B. Nesburn, and C. S. Wechsler, Science 287:1500–1503, 2000).The same study also demonstrated that a plasmid expressing LAT nucleotides 301 to 2659 enhanced cell survival of transfected cells after induction of apoptosis. Consequently, we hypothesized that LAT enhances spontaneous reactivation in part, because it promotes survival of infected neurons. Here we report on the ability of plasmids expressing different portions of the 5′ end of LAT to promote cell survival after induction of apoptosis. A plasmid expressing the first 1.5 kb of LAT (LAT nucleotides 1 to 1499) promoted cell survival in neuro-2A (mouse neuronal) and CV-1 (monkey fibroblast) cells. A plasmid expressing just the first 811 nucleotides of LAT promoted cell survival less efficiently. Plasmids expressing the first 661 nucleotides or less of LAT did not promote cell survival. We previously showed that a mutant expressing just the first 1.5 kb of LAT has wild-type spontaneous reactivation in rabbits, and a mutant expressing just the first 811 nucleotides of LAT has a reactivation frequency higher than that of
d
LAT2903 but lower than that of wild-type virus. In addition, mutants reported here for the first time, expressing just the first 661 or 76 nucleotides of LAT, had spontaneous reactivation indistinguishable from that of the LAT null mutant
d
LAT2903. In summary, these studies provide evidence that there is a functional relationship between the ability of LAT to promote cell survival and its ability to enhance spontaneous reactivation.
Characterization of H5N1 Influenza Viruses That Continue To Circulate in Geese in Southeastern China
Authors: Webster Robert G. , Guan Yi , Peiris Malik , Walker David , Krauss Scott , Zhou Nan Nan , Govorkova Elena A. , Ellis Trevor M. , Dyrting K. C. , Sit Thomas , Perez Daniel R. , Shortridge Kennedy F. 
Published: July 2002

ABSTRACT
The H5N1 influenza virus, which killed humans and poultry in 1997, was a reassortant that possibly arose in one type of domestic poultry present in the live-poultry markets of Hong Kong. Given that all the precursors of H5N1/97 are still circulating in poultry in southern China, the reassortment event that generated H5N1 could be repeated. Because A/goose/Guangdong/1/96-like (H5N1; Go/Gd) viruses are the proposed donors of the hemagglutinin gene of the H5N1 virus, we investigated the continued circulation, host range, and transmissibility of Go/Gd-like viruses in poultry. The Go/Gd-like viruses caused weight loss and death in some mice inoculated with high virus doses. Transmission of Go/Gd-like H5N1 viruses to geese by contact with infected geese resulted in infection of all birds but limited signs of overt disease. In contrast, oral inoculation with high doses of Go/Gd-like viruses resulted in the deaths of up to 50% of infected geese. Transmission from infected geese to chickens occurred only by fecal contact, whereas transmission to quail occurred by either aerosol or fecal spread. This difference is probably explained by the higher susceptibility of quail to Go/Gd-like virus. The high degree of susceptibility of quail to Go/Gd (H5N1)-like viruses and the continued circulation of H6N1 and H9N2 viruses in quail support the hypothesis that quail were the host of origin of the H5N1/97 virus. The ease of transmission of Go/Gd (H5N1)-like viruses to land-based birds, especially quail, supports the wisdom of separating aquatic and land-based poultry in the markets in Hong Kong and the need for continued surveillance in the field and live-bird markets in which different types of poultry are in contact with one another.
Molecular and Immunological Significance of Chimpanzee Major Histocompatibility Complex Haplotypes for Hepatitis C Virus Immune Response and Vaccination Studies
Authors: Mizukoshi Eishiro , Nascimbeni Michelina , Blaustein Joshua B. , Mihalik Kathleen , Rice Charles M. , Liang T. Jake , Feinstone Stephen M. , Rehermann Barbara 
Published: July 2002

ABSTRACTThe chimpanzee is a critical animal model for studying cellular immune responses to infectious pathogens such as hepatitis B and C viruses, human immunodeficiency virus, and malaria. Several candidate vaccines and immunotherapies for these infections aim at the induction or enhancement of cellular immune responses against viral epitopes presented by common human major histocompatibility complex (MHC) alleles. To identify and characterize chimpanzee MHC class I molecules that are functionally related to human alleles, we sequenced 18 differentPan troglodytes(Patr) alleles of 14 chimpanzees, 2 of them previously unknown and 3 with only partially reported sequences. Comparative analysis of Patr binding pockets and binding assays with biotinylated peptides demonstrated a molecular homology between the binding grooves of individual Patr alleles and the common human alleles HLA-A1, -A2, -A3, and -B7. Using cytotoxic T cells isolated from the blood of hepatitis C virus (HCV)-infected chimpanzees, we then mapped the Patr restriction of these HCV peptides and demonstrated functional homology between the Patr-HLA orthologues in cytotoxicity and gamma interferon (IFN-γ) release assays. Based on these results, 21 HCV epitopes were selected to characterize the chimpanzees' cellular immune response to HCV. In each case, IFN-γ-producing T cells were detectable in the blood after but not prior to HCV infection and were specifically targeted against those HCV peptides predicted by Patr-HLA homology. This study demonstrates a close functional homology between individual Patr and HLA alleles and shows that HCV infection generates HCV peptides that are recognized by both chimpanzees and humans with Patr and HLA orthologues. These results are relevant for the design and evaluation of vaccines in chimpanzees that can now be selected according to the most frequent human MHC haplotypes.
The Phosphoprotein (P) Binding Site Resides in the N Terminus of the L Polymerase Subunit of Sendai Virus
Authors: Holmes David E. , Moyer Sue A. 
Published: July 2002

ABSTRACT
Sendai virus encodes an RNA-dependent RNA polymerase which is composed of the L and P proteins. Site-directed mutagenesis of the N terminus of L has identified amino acids important for binding P. Seven of nine mutants in amino acids 1 to 350 of Sendai L lost the ability to bind to Sendai P, although they were still able to bind the viral C protein. Loss of P binding correlated with the loss of all RNA synthesis activities. Two L mutants gave limited P-L complex formation and limited viral transcription and replication.