bluuebunny/crossref_metadata_2025_split huggingface dataset:
In Vitro and In Vivo Infection of Neural Cells by a Recombinant Measles Virus Expressing Enhanced Green Fluorescent Protein
Authors: Duprex W. Paul , Mcquaid Stephen , Roscic-Mrkic Branka , Cattaneo Roberto , Mccallister Cecilia , Rima Bert K. 
Published: July 2002

ABSTRACT
This study focused on the in vitro infection of mouse and human neuroblastoma cells and the in vivo infection of the murine central nervous system with a recombinant measles virus. An undifferentiated mouse neuroblastoma cell line (TMN) was infected with the vaccine strain of measles virus (MVeGFP), which expresses enhanced green fluorescent protein (EGFP). MVeGFP infected the cells, and cell-to-cell spread was studied by virtue of the resulting EGFP autofluorescence, using real-time confocal microscopy. Cells were differentiated to a neuronal phenotype, and extended processes, which interconnected the cells, were observed. It was also possible to infect the differentiated neuroblastoma cells (dTMN) with MVeGFP. Single autofluorescent EGFP-positive cells were selected at the earliest possible point in the infection, and the spread of EGFP autofluorescence was monitored. In this instance the virus used the interconnecting processes to spread from cell to cell. Human neuroblastoma cells (SH-SY-5Y) were also infected with MVeGFP. The virus infected these cells, and existing processes were used to initiate new foci of infection at distinct regions of the monolayer. Transgenic animals expressing CD46, a measles virus receptor, and lacking interferon type 1 receptor gene were infected intracerebrally with MVeGFP. A productive infection ensued, and the mice exhibited clinical signs of infection, such as ataxia and an awkward gait, identical to those previously observed for the parental virus (Edtag). Mice were sacrificed, and brain sections were examined for EGFP autofluorescence by confocal scanning laser microscopy over a period of 6 h. EGFP was detected in discrete focal regions of the brain and in processes, which extended deep into the parenchyma. Collectively, these results indicate (i) that MVeGFP can be used to monitor virus replication sensitively, in real time, in animal tissues, (ii) that infection of ependymal cells and neuroblasts provides a route by which measles virus can enter the central nervous system in mouse models of encephalitis, and (iii) that upon infection, the virus spreads transneuronally.
The Infectivities of Turnip Yellow Mosaic Virus Genomes with Altered tRNA Mimicry Are Not Dependent on Compensating Mutations in the Viral Replication Protein
Authors: Filichkin Sergei A. , Bransom Kay L. , Goodwin Joel B. , Dreher Theo W. 
Published: July 2002

ABSTRACT
Five highly infectious turnip yellow mosaic virus (TYMV) genomes with sequence changes in their 3′-terminal regions that result in altered aminoacylation and eEF1A binding have been studied. These genomes were derived from cloned parental RNAs of low infectivity by sequential passaging in plants. Three of these genomes that are incapable of aminoacylation have been reported previously (J. B. Goodwin, J. M. Skuzeski, and T. W. Dreher, Virology 230:113–124, 1997). We now demonstrate by subcloning the 3′ untranslated regions into wild-type TYMV RNA that the high infectivities and replication rates of these genomes compared to their progenitors are mostly due to a small number of mutations acquired in the 3′ tRNA-like structure during passaging. Mutations in other parts of the genome, including the replication protein coding region, are not required for high infectivity but probably do play a role in optimizing viral amplification and spread in plants. Two other TYMV RNA variants of suboptimal infectivities, one that accepts methionine instead of the usual valine and one that interacts less tightly with eEF1A, were sequentially passaged to produce highly infectious genomes. The improved infectivities of these RNAs were not associated with increased replication in protoplasts, and no mutations were acquired in their 3′ tRNA-like structures. Complete sequencing of one genome identified two mutations that result in amino acid changes in the movement protein gene, suggesting that improved infectivity may be a function of improved viral dissemination in plants. Our results show that the wild-type TYMV replication proteins are able to amplify genomes with 3′ termini of variable sequence and tRNA mimicry. These and previous results have led to a model in which the binding of eEF1A to the 3′ end to antagonize minus-strand initiation is a major role of the tRNA-like structure.
Recovery and Characterization of a Chimeric Rinderpest Virus with the Glycoproteins of Peste-des-Petits-Ruminants Virus: Homologous F and H Proteins Are Required for Virus Viability
Authors: Das Subash C. , Baron Michael D. , Barrett Thomas 
Published: July 2002

ABSTRACT
Rinderpest (RP) and peste-des-petits-ruminants (PPR) are two important diseases of domestic ruminants. To improve on currently available vaccines against PPR, we have created cDNA copies of the RP virus genome in which either the fusion (F) or hemagglutinin (H) gene, or both, was replaced with the corresponding gene from PPR virus. It was necessary to develop a modified rescue system in which the T7 RNA polymerase was provided by a recombinant fowlpox virus and the entire rescue procedure took place in Vero cells before we could obtain live virus from these chimeric constructs. No virus was recovered when only one of the glycoprotein genes was changed, but a chimeric virus containing both F and H genes from PPR virus was reproducibly rescued from cDNA, indicating that a virus-specific functional interaction takes place between the F and H proteins. The rescued virus expressing the PPR glycoproteins grew more slowly in tissue culture than either parental virus and formed abnormally large syncytia. Goats infected with the chimera showed no adverse reaction, as assessed by clinical signs, temperature, leukocyte count, virus isolation, and serology, and were protected from subsequent challenge with wild-type PPR virus.
Foreign and Chimeric External Scaffolding Proteins as Inhibitors of
Microviridae
Morphogenesis
Authors: Burch April D. , Fane Bentley A. 
Published: July 2002

ABSTRACT

Viral assembly is an ideal system in which to investigate the transient recognition and interplay between proteins. During morphogenesis, scaffolding proteins temporarily associate with structural proteins, stimulating conformational changes that promote assembly and inhibit off-pathway reactions.
Microviridae
morphogenesis is dependent on two scaffolding proteins, an internal and an external species. The external scaffolding protein is the most conserved protein within the
Microviridae
, whose canonical members are φX174, G4, and α3. However, despite 70% homology on the amino acid level, overexpression of a foreign
Microviridae
external scaffolding protein is a potent cross-species inhibitor of morphogenesis. Mutants that are resistant to the expression of a foreign scaffolding protein cannot be obtained via one mutational step. To define the requirements for and constraints on scaffolding protein interactions, chimeric external scaffolding proteins have been constructed and analyzed for effects on in vivo assembly. The results of these experiments suggest that at least two cross-species inhibitory domains exist within these proteins; one domain most likely blocks procapsid formation, and the other allows procapsid assembly but blocks DNA packaging. A mutation conferring resistance to the expression of a chimeric protein (chiD
r
) that inhibits DNA packaging was isolated. The mutation maps to gene A, which encodes a protein essential for packaging. The
chiD
r
mutation confers resistance only to a chimeric D protein; the mutant is still inhibited by the expression of foreign D proteins. The results presented here demonstrate how closely related proteins could be developed into antiviral agents that specifically target virion morphogenesis.
Diminished Primary and Secondary Influenza Virus-Specific CD8+T-Cell Responses in CD4-Depleted Ig−/−Mice
Authors: Riberdy Janice M. , Christensen Jan P. , Branum Kristen , Doherty Peter C. 
Published: July 2002

ABSTRACTOptimal expansion of influenza virus nucleoprotein (DbNP366)-specific CD8+T cells following respiratory challenge of naive Ig−/−μMT mice was found to require CD4+T-cell help, and this effect was also observed in primed animals. Absence of the CD4+population was consistently correlated with diminished recruitment of virus-specific CD8+T cells to the infected lung, delayed virus clearance, and increased morbidity. The splenic CD8+set generated during the recall response in Ig−/−mice primed at least 6 months previously showed a normal profile of gamma interferon production subsequent to short-term, in vitro stimulation with viral peptide, irrespective of a concurrent CD4+T-cell response. Both the magnitude and the localization profiles of virus-specific CD8+T cells, though perhaps not their functional characteristics, are thus modified in mice lacking CD4+T cells.
Identification of
Notch1
as a Frequent Target for Provirus Insertional Mutagenesis in T-Cell Lymphomas Induced by Leukemogenic Mutants of Mouse Mammary Tumor Virus
Authors: Yanagawa Shin-ichi , Lee Jong-Seo , Kakimi Kazuhiro , Matsuda Yukihiro , Honjo Tasuku , Ishimoto Akinori 
Published: July 2002

ABSTRACT

In contrast to wild-type mouse mammary tumor virus (MMTV), the MMTV mutants with specific deletions in the U3 region of their long terminal repeats cause T-cell lymphomas. In 30% of T-cell lymphomas arising in BALB/c mice infected with MLA-MMTV, a leukemogenic MMTV mutant, we have found that MMTV proviruses were integrated into a short region of the
Notch1
genome, so that truncated
Notch1
transcripts encoding the transmembrane and the cytoplasmic domains of Notch1 protein could be expressed. Thus,
Notch1
is a major target of provirus insertional mutagenesis in these T-cell lymphomas.
Generation of Subgenomic RNA Directed by a Satellite RNA Associated with Bamboo Mosaic Potexvirus: Analyses of Potexvirus Subgenomic RNA Promoter
Authors: Lee Yun-Shien , Hsu Yau-Heiu , Lin Na-Sheng 
Published: July 2002

ABSTRACTSatellite RNA of bamboo mosaic potexvirus (satBaMV), a single-stranded positive-sense RNA encoding a nonstructural protein of 20 kDa (P20), depends on bamboo mosaic potexvirus (BaMV) for replication and encapsidation. A full-length cDNA clone of satBaMV was used to examine the sequences required for the synthesis of potexvirus subgenomic RNAs (sgRNAs). Subgenomic promoter-like sequences (SGPs), 107 nucleotides (nt) upstream from the capsid protein (CP) gene of BaMV-V, were inserted upstream of the start codon of the P20 gene of satBaMV. Insertion of SGPs gave rise to the synthesis of sgRNA of satBaMV in protoplasts ofNicotiana benthamianaand leaves ofChenopodium quinoawhen coinoculated with BaMV-V genomic RNA. Moreover, both the satBaMV cassette and its sgRNA were encapsidated. From analysis of the SGPs by deletion mutation, we concluded that an SGP contains one core promoterlike sequence (nt −30 through +16), two upstream enhancers (nt −59 through −31 and −91 through −60), and one downstream enhancer (nt +17 through +52), when the transcription initiation site is taken as +1. Site-directed mutagenesis and compensatory mutation to disrupt and restore potential base pairing in the core promoter-like sequence suggest that the stem-loop structure is important for the function of SGP in vivo. Likewise, the insertion of a putative SGP of the BaMV open reading frame 2 gene or a heterologous SGP of potato virus X resulted in generation of an sgRNA. The satBaMV cassette should be a useful tool to gain insight into sequences required for the synthesis of potexvirus sgRNAs.
TVB Receptors for Cytopathic and Noncytopathic Subgroups of Avian Leukosis Viruses Are Functional Death Receptors
Authors: Brojatsch Jürgen , Naughton John , Adkins Heather B. , Young John A. T. 
Published: July 2002

ABSTRACT

The identification of TVB
S3
, a cellular receptor for the cytopathic subgroups B and D of avian leukosis virus (ALV-B and ALV-D), as a tumor necrosis factor receptor-related death receptor with a cytoplasmic death domain, provides a compelling argument that viral Env-receptor interactions are linked to cell death (4). However, other TVB proteins have been described that appear to have similar death domains but are cellular receptors for the noncytopathic subgroup E of ALV (ALV-E): TVB
T
, a turkey subgroup E-specific ALV receptor, and TVB
S1
, a chicken receptor for subgroups B, D, and E ALV. To begin to understand the role of TVB receptors in the cytopathic effects associated with infection by specific ALV subgroups, we asked whether binding of a soluble ALV-E surface envelope protein (SU) to its receptor can lead to cell death. Here we report that ALV-E SU-receptor interactions can induce apoptosis in quail or turkey cells. We also show directly that TVB
S1
and TVB
T
are functional death receptors that can trigger cell death by apoptosis via a mechanism involving their cytoplasmic death domains and activation of the caspase pathway. These data demonstrate that ALV-B and ALV-E use functional death receptors to enter cells, and it remains to be determined why only subgroups B and D viral infections lead specifically to cell death.
Herpes Simplex Virus Type 1 ICP4 Promotes Transcription Preinitiation Complex Formation by Enhancing the Binding of TFIID to DNA
Authors: Grondin Benoit , DeLuca Neal 
Published: July 2002

ABSTRACT
Infected-cell polypeptide 4 (ICP4) of herpes simplex virus type 1 (HSV-1) activates the expression of many HSV genes during infection. It functions along with the cellular general transcription factors to increase the transcription rates of genes. In this study, an HSV late promoter consisting of only a TATA box and an INR element was immobilized on a magnetic resin and incubated with nuclear extracts or purified TFIID in the presence and absence of ICP4. Analysis of the complexes formed on these promoters revealed that ICP4 increased the formation of transcription preinitiation complexes (PICs) in a TATA box-dependent manner, as determined by the presence of ICP4, TFIID, TFIIB, and polymerase II on the promoter. With both nuclear extract and purified TFIID, it was determined that ICP4 helped TFIID bind to the promoter and the TATA box. These observations differed from those for the activator Gal4-VP16. As previously observed by others, Gal4-VP16 also increased the formation of PICs without helping TFIID bind to the promoter, suggesting that ICP4 and VP16 differ in their mechanism of activation and that ICP4 functions to facilitate PIC formation at an earlier step in the formation of PICs. We also observed that the DNA binding activity of ICP4 was not sufficient to help TFIID bind to the promoter and that the region of ICP4 that was responsible for this activity is located between residues 30 and 274. Taken together these results demonstrate that a specific region of ICP4 helps TFIID bind to the TATA box and that this in turn facilitates the formation of transcription PICs.
Internal Ribosomal Entry Site-Mediated Translation Initiation in Equine Rhinitis A Virus: Similarities to and Differences from That of Foot-and-Mouth Disease Virus
Authors: Hinton Tracey M. , Li Feng , Crabb Brendan S. 
Published: July 2002

ABSTRACT

Equine rhinitis A virus
(ERAV) has recently been classified as an aphthovirus, a genus otherwise comprised of the different serotypes of
Foot-and-mouth disease virus
(FMDV). FMDV initiates translation via a type II internal ribosomal entry site (IRES) and utilizes two in-frame AUG codons to produce the leader proteinases Lab and Lb. Here we show that the ERAV 5′ nontranslated region also possesses the core structures of a type II IRES. The functional activity of this region was characterized by transfection of bicistronic plasmids into BHK-21 cells. In this system the core type II structures, stem-loops D to L, in addition to a stem-loop (termed M) downstream of the first putative initiation codon, are required for translation of the second reporter gene. In FMDV, translation of Lb is more efficient than that of Lab despite the downstream location of the Lb AUG codon. The ERAV genome also has putative initiation sites in positions similar to those utilized in FMDV, except that in ERAV these are present as two AUG pairs (AUGAUG). Using the bicistronic expression system, we detected initiation from both AUG pairs, although in contrast to FMDV, the first site is strongly favored over the second. Mutational analysis of the AUG codons indicated that AUG2 is the major initiation site, although AUG1 can be accessed, albeit inefficiently, in the absence of AUG2. Further mutational analysis indicated that codons downstream of AUG2 appear to be accessed by a mechanism other than leaky scanning. Furthermore, we present preliminary evidence that it is possible for ribosomes to access downstream of the two AUG pairs. This study reveals important differences in IRES function between aphthoviruses.
Cap-Independent Translational Enhancement of Turnip Crinkle Virus Genomic and Subgenomic RNAs
Authors: Qu Feng , Morris T. Jack 
Published: July 2002

ABSTRACT

The presence of translational control elements and cap structures has not been carefully investigated for members of the
Carmovirus
genus, a group of small icosahedral plant viruses with positive-sense RNA genomes. In this study, we examined both the 5′ and 3′ untranslated regions (UTRs) of the turnip crinkle carmovirus (TCV) genomic RNA (4 kb) as well as the 5′ UTR of the coat protein subgenomic RNA (1.45 kb) for their roles in translational regulation. All three UTRs enhanced translation of the firefly luciferase reporter gene to different extents. Optimal translational efficiency was achieved when mRNAs contained both 5′ and 3′ UTRs. The synergistic effect due to the 5′-3′ cooperation was at least fourfold greater than the sum of the contributions of the individual UTRs. The observed translational enhancement of TCV mRNAs occurred in a cap-independent manner, a result consistent with the demonstration, using a cap-specific antibody, that the 5′ end of the TCV genomic RNA was uncapped. Finally, the translational enhancement activity within the 5′ UTR of 1.45-kb subgenomic RNA was shown to be important for the translation of coat protein in protoplasts and for virulent infection in
Arabidopsis
plants.
Possible Involvement of the Double-Stranded RNA-Binding Core Protein ςA in the Resistance of Avian Reovirus to Interferon
Authors: Martínez-Costas José , González-López Claudia , Vakharia Vikram N. , Benavente Javier 
Published: July 2002

ABSTRACT
Treatment of primary cultures of chicken embryo fibroblasts with a recombinant chicken alpha/beta interferon (rcIFN) induces an antiviral state that causes a strong inhibition of vaccinia virus and vesicular stomatitis virus replication but has no effect on avian reovirus S1133 replication. The fact that avian reovirus polypeptides are synthesized normally in rcIFN-treated cells prompted us to investigate whether this virus expresses factors that interfere with the activation and/or the activity of the IFN-induced, double-stranded RNA (dsRNA)-dependent enzymes. Our results demonstrate that extracts of avian-reovirus-infected cells, but not those of uninfected cells, are able to relieve the translation-inhibitory activity of dsRNA in reticulocyte lysates, by blocking the activation of the dsRNA-dependent enzymes. In addition, our results show that protein ςA, an S1133 core polypeptide, binds to dsRNA in an irreversible manner and that clearing this protein from extracts of infected cells abolishes their protranslational capacity. Taken together, our results raise the interesting possibility that protein ςA antagonizes the IFN-induced cellular response against avian reovirus by blocking the intracellular activation of enzyme pathways dependent on dsRNA, as has been suggested for several other viral dsRNA-binding proteins.
Cytokine Expression, Natural Killer Cell Activation, and Phenotypic Changes in Lymphoid Cells from Rhesus Macaques during Acute Infection with Pathogenic Simian Immunodeficiency Virus
Authors: Giavedoni Luis D. , Velasquillo M. Cristina , Parodi Laura M. , Hubbard Gene B. , Hodara Vida L. 
Published: July 2002

ABSTRACTWe studied the innate and adaptive immune system of rhesus macaques infected with the virulent simian immunodeficiency virus isolate SIVmac251 by evaluating natural killer (NK) cell activity, cytokine levels in plasma, humoral and virological parameters, and changes in the activation markers CD25 (interleukin 2R [IL-2R] α chain), CD69 (early activation marker), and CD154 (CD40 ligand) in lymphoid cells. We found that infection with SIVmac251 induced the sequential production of interferon-α/β (IFN-α/β), IL-18, and IL-12. IFN-γ, IL-4, and granulocyte-macrophage colony-stimulating factor were undetected in plasma by the assays used. NK cell activity peaked at 1 to 2 weeks postinfection and paralleled changes in viral loads. Maximum expression of CD69 on CD3−CD16+lymphocytes correlated with NK cytotoxicity during this period. CD25 expression, which is associated with proliferation, was static or slightly down-regulated in CD4+T cells from both peripheral blood (PB) and lymph nodes (LN). CD69, which is normally present in LN CD4+T cells and absent in peripheral blood leukocyte (PBL) CD4+T cells, was down-regulated in LN CD4+T cells and up-regulated in PBL CD4+T cells immediately after infection. CD8+T cells increased CD69 but not CD25 expression, indicating the activation of this cellular subset in PB and LN. Finally, CD154 was transiently up-regulated in PBL CD4+T cells but not in LN CD4+T cells. Levels of antibodies to SIV Gag and Env did not correlate with the level of activation of CD154, a critical costimulatory molecule for T-cell-dependent immunity. In summary, we present the first documented evidence that the innate immune system of rhesus macaques recognizes SIV infection by sequential production of proinflammatory cytokines and transient activation of NK cytotoxic activity. Additionally, pathogenic SIV induces drastic changes in the level of activation markers on T cells from different anatomic compartments. These changes involve activation in the absence of proliferation, indicating that activation-induced cell death may cause some of the reported increase in lymphocyte turnover during SIV infection.