bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigation of Structural and Functional Motifs within the Vaccinia Virus A14 Phosphoprotein, an Essential Component of the Virion Membrane
Authors: Mercer Jason , Traktman Paula 
Published: July 2003

ABSTRACT

We have previously reported the construction and characterization of an inducible recombinant virus in which expression of the vaccinia virus membrane protein A14 is experimentally regulated using the tetracycline operator-repressor system. Repression of A14, which results in a 1,000-fold reduction in viral yield, leads to an early block in viral morphogenesis characterized by the accumulation of large virosomes, empty “crescents” that fail to contact these virosomes, and, most strikingly, large numbers of aberrant 25-nm vesicles. Here we report the establishment of a transient-complementation system for the structure-function analysis of A14. We have constructed numerous mutant alleles of A14 designed to identify and test the importance of key structural and sequence motifs within A14, including sites of posttranslational modification, such as glycosylation, phosphorylation, and dimerization. From these studies we have determined that robust complementation ability requires an intact N terminus and two regions flanking the first membrane-spanning domain of A14. We show that A14 is modified by N-linked glycosylation both in vitro and in vivo. However, only a minority of A14 molecules are glycosylated in vivo and these are not encapsidated. In this report we also identify the sole phosphorylated serine residue of A14 as lying within the NHS
85
motif that undergoes glycosylation. Additionally, we show that the Cys
71
residue is required for intermolecular disulfide bond formation and describe the properties of a virus expressing an allele of A14 that cannot form disulfide-linked dimers.
Deletions in the Putative Cell Receptor-Binding Domain of Sindbis Virus Strain MRE16 E2 Glycoprotein Reduce Midgut Infectivity in
Aedes aegypti
Authors: Myles Kevin M. , Pierro Dennis J. , Olson Ken E. 
Published: July 2003

ABSTRACT

The Sindbis virus (
Alphavirus
;
Togaviridae
) strain MRE16 efficiently infects
Aedes aegypti
mosquitoes that ingest a blood meal containing 8 to 9 log
10
PFU of virus/ml. However, a small-plaque variant of this virus, MRE16sp, poorly infects mosquitoes after oral infection with an equivalent titer. To determine the genetic differences between MRE16 and MRE16sp viruses, we have sequenced the MRE16sp structural genes and found a 90-nucleotide deletion in the E2 glycoprotein that spans the 3′ end of the coding region for the putative cell-receptor binding domain (CRBD). We examined the role of this deletion in oral infection of mosquitoes by constructing infectious clones pMRE16icΔE200-Y229 and pMRE16ic, representing MRE16 virus genomes with and without the deletion, respectively. A third infectious clone, pMRE16icΔE200-C220, was also constructed that contained a smaller deletion extending only to the 3′ terminus of the CRBD coding region. Virus derived from pMRE16ic replicated with the same efficiency as parental virus in vertebrate (BHK-21) and mosquito (C6/36) cells and orally infected
A. aegypti
. Viruses derived from pMRE16icΔE200-Y229 and pMRE16icΔE200-C220 replicated 10- to 100-fold less efficiently in C6/36 and BHK-21 cells than did MRE16ic virus. Each deletion mutant poorly infected
A. aegypti
and dramatically reduced midgut infectivity and dissemination. However, all viruses generated nearly equal titers (∼6.0 log
10
PFU/ml) in mosquitoes 4 days after infection by intrathoracic inoculation. These results suggest that the deleted portion of the E2 CRBD represents an important determinant of MRE16 virus midgut infectivity in
A. aegypti
.
Endocytosis of Hepatitis B Immune Globulin into Hepatocytes Inhibits the Secretion of Hepatitis B Virus Surface Antigen and Virions
Authors: Schilling Ralf , Ijaz Samreen , Davidoff Michail , Lee Jia Yee , Locarnini Stephen , Williams Roger , Naoumov Nikolai V. 
Published: July 2003

ABSTRACTHepatitis B immunoglobulin is used for prophylaxis against hepatitis B virus (HBV) and is thought to act by neutralization of virions and hepatitis B virus surface antigen (HBsAg)-containing particles in circulation. Using a panel of hepatocyte-derived cell lines, the present study investigated in vitro whether HBs-specific immunoglobulin G (IgG) is internalized in hepatocytes and whether it interacts with HBsAg in the cells. By immunoelectron microscopy and immunoblotting, human IgG and FcRn receptor for IgG were demonstrated on cellular membranes and in cytoplasmic extracts, irrespective of the HBsAg status of the cells. Furthermore, HBsAg and anti-HBs were shown to be colocalized in the same cellular compartment by two-color confocal microscopy. Endocytosis of HBs-specific IgG caused intracellular accumulation of HBsAg in a dose-dependent manner and inhibited the secretion of HBsAg and HBV virions from the cells. These effects were not observed with F(ab)2fragments or nonimmune IgG as controls. The specificity of intracellular HBsAg- anti-HBs interaction was further investigated in cells transfected with HBV genomes expressing wild-type HBsAg or immune escape HBsAg (with a G145R mutation). Monoclonal anti-HBs markedly reduced the secretion of wild-type HBsAg, while the secretion of mutant HBsAg was not affected. These results suggest that HBs-specific IgG binds to hepatocytes and interacts with HBsAg within the cells. This may be relevant for the selection of surface antibody escape mutations.
Cell Cycle Arrest by Kaposi's Sarcoma-Associated Herpesvirus Replication-Associated Protein Is Mediated at both the Transcriptional and Posttranslational Levels by Binding to CCAAT/Enhancer-Binding Protein α and p21
CIP-1
Authors: Wu Frederick Y. , Wang Shizhen Emily , Tang Qi-Qun , Fujimuro Masahiro , Chiou Chuang-Jiun , Zheng Qizhi , Chen Honglin , Hayward S. Diane , Lane M. Daniel , Hayward Gary S. 
Published: July 2003

ABSTRACT

Lytic-cycle replication of Kaposi's sarcoma-associated herpesvirus (KSHV) in PEL cells causes G
1
cell cycle arrest mediated by the virus-encoded replication-associated protein (RAP) (or K8 protein), which induces high-level expression of the cellular C/EBPα and p21 proteins. Here we have examined the mechanism of this induction at both the transcriptional and posttranslational levels. RAP proved to bind very efficiently to both C/EBPα and p21 and stabilized them by up to 10-fold from proteasome-mediated degradation in vitro. Cross-linking revealed that RAP itself forms stable dimers and tetramers in solution and forms higher-order complexes but not heterodimers with C/EBPα. Cotransfection of RAP with C/EBPα cooperatively stimulated both the C/EBPα and p21 promoters in luciferase reporter gene assays. Only the basic/leucine zipper region of RAP was needed for interaction with and stabilization of C/EBPα, but both the N-terminal and C-terminal domains were required for transcriptional augmentation. In vitro-translated RAP interfered with DNA binding by C/EBPα in electrophonetic mobility shift assay (EMSA) experiments but did not itself bind to the target C/EBPα sites or form supershifted bands. However, in endogenous chromatin immunoprecipitation (ChIP) assays with tetradecanoyl phorbol acetate-induced PEL cells, RAP proved to specifically associate with the C/EBPα promoter in vivo, but only in a C/EBPα-dependent manner, implying an in vivo piggyback interaction with DNA-bound C/EBPα. Expression of exogenous RAP (Ad-RAP) caused G
1
/S cell cycle arrest in human dermal microvascular endothelial cells and also induced both the C/EBPα and p21 proteins, which formed punctate nuclear patterns that colocalized with RAP in PML nuclear bodies. In the presence of RAP, C/EBPα was also efficiently recruited into viral DNA replication compartments in both infected and cotransfected cells. In support of a direct role for this interaction in viral DNA replication, three C/EBPα binding sites were identified by in vitro EMSA experiments within a 220-bp core segment of the duplicated KSHV Ori-Lyt region, and although RAP did not bind to Ori-Lyt DNA directly in vitro, both endogenous RAP and C/EBPα were found to be associated with the Ori-Lyt region by ChIP assays in lytically induced PEL cells. Finally, we found that the KSHV lytic cycle could not be triggered by either synchronizing KSHV latently infected PEL cells in G
1
phase or inducing p21 in a C/EBPα-independent process.
Residues in the Apical Domain of the Feline and Canine Transferrin Receptors Control Host-Specific Binding and Cell Infection of Canine and Feline Parvoviruses
Authors: Palermo Laura M. , Hueffer Karsten , Parrish Colin R. 
Published: July 2003

ABSTRACT
Canine parvovirus (CPV) and feline panleukopenia virus (FPV) capsids bind to the transferrin receptors (TfRs) of their hosts and use these receptors to infect cells. The binding is partially host specific, as FPV binds only to the feline TfR, while CPV binds to both the canine and feline TfRs. The host-specific binding is controlled by a combination of residues within a raised region of the capsid. To define the TfR structures that interact with the virus, we altered the apical domain of the feline or canine TfR or prepared chimeras of these receptors and tested the altered receptors for binding to FPV or CPV capsids. Most changes in the apical domain of the feline TfR did not affect binding, but replacing Leu221 with Ser or Asp prevented receptor binding to either FPV or CPV capsids, while replacing Leu221 with Lys resulted in a receptor that bound only to CPV but not to FPV. Analysis of recombinants of the feline and canine TfRs showed that sequences controlling CPV-specific binding were within the apical domain and that more than one difference between these receptors determined the CPV-specific binding of the canine TfR. Single changes within the canine TfR which removed a single amino acid insertion or which eliminated a glycosylation site gave that receptor the expanded ability to bind to FPV and CPV. In some cases, binding of capsids to mutant receptors did not result in infection, suggesting a structural role for the receptor in cell infection by the viruses.
Incorporation of Tick-Borne Encephalitis Virus Replicons into Virus-Like Particles by a Packaging Cell Line
Authors: Gehrke Rainer , Ecker Michael , Aberle Stephan W. , Allison Steven L. , Heinz Franz X. , Mandl Christian W. 
Published: July 2003

ABSTRACTRNA replicons derived from flavivirus genomes show considerable potential as gene transfer and immunization vectors. A convenient and efficient encapsidation system is an important prerequisite for the practical application of such vectors. In this work, tick-borne encephalitis (TBE) virus replicons and an appropriate packaging cell line were constructed and characterized. A stable CHO cell line constitutively expressing the two surface proteins prM/M and E (named CHO-ME cells) was generated and shown to efficiently export mature recombinant subviral particles (RSPs). When replicon NdΔME lacking the prM/M and E genes was introduced into CHO-ME cells, virus-like particles (VLPs) capable of initiating a single round of infection were released, yielding titers of up to 5 × 107/ml in the supernatant of these cells. Another replicon (NdΔCME) lacking the region encoding most of the capsid protein C in addition to proteins prM/M and E was not packaged by CHO-ME cells. As observed with other flavivirus replicons, both TBE virus replicons appeared to exert no cytopathic effect on their host cells. Sedimentation analysis revealed that the NdΔME-containing VLPs were physically distinct from RSPs and similar to infectious virions. VLPs could be repeatedly passaged in CHO-ME cells but maintained the property of being able to initiate only a single round of infection in other cells during these passages. CHO-ME cells can thus be used both as a source for mature TBE virus RSPs and as a safe and convenient replicon packaging cell line, providing the TBE virus surface proteins prM/M and E intrans.
Reovirus-Induced Alteration in Expression of Apoptosis and DNA Repair Genes with Potential Roles in Viral Pathogenesis
Authors: DeBiasi Roberta L. , Clarke Penny , Meintzer Suzanne , Jotte Robert , Kleinschmidt-Demasters B. K. , Johnson Gary L. , Tyler Kenneth L. 
Published: July 2003

ABSTRACT
Reoviruses are a leading model for understanding cellular mechanisms of virus-induced apoptosis. Reoviruses induce apoptosis in multiple cell lines in vitro, and apoptosis plays a key role in virus-induced tissue injury of the heart and brain in vivo. The activation of transcription factors NF-κB and c-Jun are key events in reovirus-induced apoptosis, indicating that new gene expression is critical to this process. We used high-density oligonucleotide microarrays to analyze cellular transcriptional alterations in HEK293 cells after infection with reovirus strain T3A (i.e., apoptosis inducing) compared to infection with reovirus strain T1L (i.e., minimally apoptosis inducing) and uninfected cells. These strains also differ dramatically in their potential to induce apoptotic injury in hearts of infected mice in vivo—T3A is myocarditic, whereas T1L is not. Using high-throughput microarray analysis of over 12,000 genes, we identified differential expression of a defined subset of genes involved in apoptosis and DNA repair after reovirus infection. This provides the first comparative analysis of altered gene expression after infection with viruses of differing apoptotic phenotypes and provides insight into pathogenic mechanisms of virus-induced disease.
Local Delivery of CpG Oligodeoxynucleotides Induces Rapid Changes in the Genital Mucosa and Inhibits Replication, but Not Entry, of Herpes Simplex Virus Type 2
Authors: Ashkar Ali A. , Bauer Stefan , Mitchell William J. , Vieira Jeff , Rosenthal Kenneth L. 
Published: July 2003

ABSTRACTMucosal surfaces are the entry sites for the vast majority of infectious pathogens and provide the first line of defense against infection. In addition to the epithelial barrier, the innate immune system plays a key role in recognizing and rapidly responding to invading pathogens via innate receptors, such as Toll-like receptors (TLR). Bacterial CpG DNA, a potent activator of innate immunity, is recognized by TLR9. Here, we confirm that local mucosal, but not systemic, delivery of CpG oligodeoxynucleotides (ODN) to the genital tract protects mice from a subsequent lethal vaginal herpes simplex virus type 2 (HSV-2) challenge. Since these effects were so local in action, we examined the genital mucosa. Local delivery of CpG ODN induced rapid proliferation and thickening of the genital epithelium and caused significant recruitment of inflammatory cells to the submucosa. Local CpG ODN treatment also resulted in inhibition of HSV-2 replication but had no effect on HSV-2 entry into the genital mucosa. CpG ODN-induced protection against HSV-2 was not associated with early increases in gamma interferon (IFN-γ) secretion in the genital tract, and CpG ODN-treated IFN-γ−/−mice were protected from subsequent challenge with a lethal dose of HSV-2. Treatment of human HEK-293 cells transfected with murine TLR9 showed that the antiviral activity of CpG ODN was mediated through TLR9. These studies suggest that local induction of mucosal innate immunity can provide protection against sexually transmitted infections, such as HSV-2 or possibly human immunodeficiency virus, at the mucosal surfaces.
Conditional Suppression of Cellular Genes: Lentivirus Vector-Mediated Drug-Inducible RNA Interference
Authors: Wiznerowicz Maciej , Trono Didier 
Published: July 2003

ABSTRACT
RNA interference has emerged as a powerful technique to downregulate the expression of specific genes in cells and in animals, thus opening new perspectives in fields ranging from developmental genetics to molecular therapeutics. Here, we describe a method that significantly expands the potential of RNA interference by permitting the conditional suppression of genes in mammalian cells. Within a lentivirus vector background, we subjected the polymerase III promoter-dependent production of small interfering RNAs to doxycycline-controllable transcriptional repression. The resulting system can achieve the highly efficient and completely drug-inducible knockdown of cellular genes. As lentivirus vectors can stably transduce a wide variety of targets both in vitro and in vivo and can be used to generate transgenic animals, the present system should have broad applications.
Function of Herpes Simplex Virus Type 1 gD Mutants with Different Receptor-Binding Affinities in Virus Entry and Fusion
Authors: Milne Richard S. B. , Hanna Sheri L. , Rux Ann H. , Willis Sharon H. , Cohen Gary H. , Eisenberg Roselyn J. 
Published: July 2003

ABSTRACT
We have studied the receptor-specific function of four linker-insertion mutants of herpes simplex virus type 1 glycoprotein D (gD) representing each of the functional regions of gD. We used biosensor analysis to measure binding of the gD mutants to the receptors HVEM (HveA) and nectin-1 (HveC). One of the mutants, gD(∇34t), failed to bind HVEMt but showed essentially wild-type (WT) affinity for nectin-1t. The receptor-binding kinetics and affinities of the other three gD mutants varied over a 1,000-fold range, but each mutant had the same affinity for both receptors. All of the mutants were functionally impaired in virus entry and cell fusion, and the levels of activity were strikingly similar in these two assays. gD(∇34)-containing virus was defective on HVEM-expressing cells but did enter nectin-1-expressing cells to about 60% of WT levels. This showed that the defect of this form of gD on HVEM-expressing cells was primarily one of binding and that this was separable from its later function in virus entry. gD(∇243t) showed WT binding affinity for both receptors, but virus containing this form of gD had a markedly reduced rate of entry, suggesting that gD(∇243) is impaired in a postbinding step in the entry process. There was no correlation between gD mutant activity in fusion or virus entry and receptor-binding affinity. We conclude that gD functions in virus entry and cell fusion regardless of its receptor-binding kinetics and that as long as binding to a functional receptor occurs, entry will progress.
Complete Genomic Sequencing Shows that Polioviruses and Members of Human Enterovirus Species C Are Closely Related in the Noncapsid Coding Region
Authors: Brown Betty , Oberste M. Steven , Maher Kaija , Pallansch Mark A. 
Published: July 2003

ABSTRACT

The 65 human enterovirus serotypes are currently classified into five species:
Poliovirus
(3 serotypes),
Human enterovirus A
(HEV-A) (12 serotypes), HEV-B (37 serotypes), HEV-C (11 serotypes), and HEV-D (2 serotypes). Coxsackie A virus (CAV) serotypes 1, 11, 13, 15, 17, 18, 19, 20, 21, 22, and 24 constitute HEV-C. We have determined the complete genome sequences for the remaining nine HEV-C serotypes and compared them with the complete sequences of CAV21, CAV24, and the polioviruses. The viruses were most diverse in the capsid region (4 to 36% amino acid difference). A high degree of capsid sequence conservation (96% amino acid identity) suggests that CAV15 and CAV18 should be classified as strains of CAV11 and CAV13, respectively. In the 3CD region, CAV1, CAV19, and CAV22 differed from one another by only 1.2 to 1.4% and CAV11, CAV13, CAV17, CAV20, CAV21, CAV24, and the polioviruses differed from one another by only 1.2 to 3.6%. The two groups, however, differed from one another by 14.6 to 16.2%. The polioviruses as a group were monophyletic only in the capsid region. Only one group of serotypes (CAV1, CAV19, and CAV22) was consistently monophyletic in multiple genome regions. Incongruities among phylogenetic trees based on different genome regions strongly suggest that recombination has occurred between the polioviruses, CAV11, CAV13, CAV17, and CAV20. The close relationship among the polioviruses and CAV11, CAV13, CAV17, CAV20, CAV21, and CAV24 and the uniqueness of CAV1, CAV19, and CAV22 suggest that revisions should be made to the classification of these viruses.
Cellular Localization of Nectin-1 and Glycoprotein D during Herpes Simplex Virus Infection
Authors: Krummenacher Claude , Baribaud Isabelle , Eisenberg Roselyn J. , Cohen Gary H. 
Published: July 2003

ABSTRACT

During viral entry, herpes simplex virus (HSV) glycoprotein D (gD) interacts with a specific cellular receptor such as nectin-1 (PRR1/HveC/CD111) or the herpesvirus entry mediator A (HVEM/HveA). Nectin-1 is involved in cell-to-cell adhesion. It is located at adherens junctions, where it bridges cells through homophilic or heterophilic interactions with other nectins. Binding of HSV gD prevents nectin-1-mediated cell aggregation. Since HSV gD affects the natural function of nectin-1, we further investigated the effects of gD expression on nectin-1 during HSV infection or in transfected cells. We also studied the importance of the interaction between nectin-1 and the cytoplasmic protein afadin for HSV entry and spread as well as the effects of infection on this interaction. In these investigations, we used a panel of cells expressing nectin-1 or nectin-1-green fluorescent protein fusions as the only mediators of HSV entry. During HSV infection, nectin-1 localization at adherens junction was dramatically altered in a manner dependent on gD expression. Nectin-1 and gD colocalized at cell contact areas between infected and noninfected cells and at the edges of plaques. This specific accumulation of gD at junctions was driven by expression of nectin-1 in
trans
on the surface of adjacent cells. Reciprocally, nectin-1 was maintained at junctions by the
trans
expression of gD in the absence of a cellular natural ligand. Our observations indicate that newly synthesized gD substitutes for nectin-1 of infected cells at junctions with noninfected cells. We propose that gD attracts and maintains the receptor at junctions where it can be used for virus spread.