bluuebunny/crossref_metadata_2025_split huggingface dataset:
Enhanced Antiscrapie Effect Using Combination Drug Treatment
Authors: Kocisko David A. , Caughey Byron , Morrey John D. , Race Richard E. 
Published: September 2006

ABSTRACT

Combination treatment with pentosan polysulfate and Fe(III)
meso
-tetra(4-sulfonatophenyl)porphine in mice beginning 14 or 28 days after scrapie inoculation significantly increased survival times. This increase may be synergistic, implying that the compounds act cooperatively in vivo. Combination therapy may therefore be more effective for treatment of transmissible spongiform encephalopathies and other protein-misfolding diseases.
Weak Mutators Can Drive the Evolution of Fluoroquinolone Resistance in
Escherichia coli
Authors: Örlén Hanna , Hughes Diarmaid 
Published: September 2006

ABSTRACT

Weak mutators are common among clinical isolates of
Escherichia coli
. We show that the relative mutation rate and the “evolvability of fluoroquinolone resistance” are related by a power law slope of 1.2 over 3 orders of magnitude. Thus, even weak mutators can drive the evolution of fluoroquinolone resistance under selection pressure.
Standardization of an Experimental Murine Model of Invasive Pulmonary Aspergillosis
Authors: Sheppard Donald C. , Graybill John R. , Najvar Laura K. , Chiang Lisa Y. , Doedt Thomas , Kirkpatrick William R. , Bocanegra Rosie , Vallor Ana C. , Patterson Thomas F. , Filler Scott G. 
Published: September 2006

ABSTRACT
Evaluating new therapeutic agents for invasive aspergillosis requires animal models that are reproducible among different laboratories. We therefore evaluated a murine model of aerosol infection in two independent laboratories and found a high level of both intra- and interlaboratory reproducibility of survival, fungal burden over time, and the efficacy of liposomal amphotericin B.
Vaccinia Virus Infection Attenuates Innate Immune Responses and Antigen Presentation by Epidermal Dendritic Cells
Authors: Deng Liang , Dai Peihong , Ding Wanhong , Granstein Richard D. , Shuman Stewart 
Published: September 2006

ABSTRACTLangerhans cells (LCs) are antigen-presenting cells in the skin that play sentinel roles in host immune defense by secreting proinflammatory molecules and activating T cells. Here we studied the interaction of vaccinia virus with XS52 cells, a murine epidermis-derived dendritic cell line that serves as a surrogate model for LCs. We found that vaccinia virus productively infects XS52 cells, yet this infection displays an atypical response to anti-poxvirus agents. Whereas adenosine N1-oxide blocked virus production and viral protein synthesis during a synchronous infection, cytosine arabinoside had no effect at concentrations sufficient to prevent virus replication in BSC40 monkey kidney cells. Vaccinia virus infection of XS52 cells not only failed to elicit the production of various cytokines, including tumor necrosis factor alpha (TNF-α), interleukin-1β (IL-1β), IL-6, IL-10, IL-12 p40, alpha interferon (IFN-α), and IFN-γ, it actively inhibited the production of proinflammatory cytokines TNF-α and IL-6 by XS52 cells in response to exogenous lipopolysaccharide (LPS) or poly(I:C). Infection with a vaccinia virus mutant lacking the E3L gene resulted in TNF-α secretion in the absence of applied stimuli. Infection of XS52 cells or BSC40 cells with the ΔE3L virus, but not wild-type vaccinia virus, triggered proteolytic decay of IκBα. These results suggest a novel role for the E3L protein as an antagonist of the NF-κB signaling pathway. ΔE3L-infected XS52 cells secreted higher levels of TNF-α and IL-6 in response to LPS and poly(I:C) than did cells infected with the wild-type virus. XS52 cells were productively infected by a vaccinia virus mutant lacking the K1L gene. ΔK1L-infected cells secreted higher levels of TNF-α and IL-6 in response to LPS than wild-type virus-infected cells. Vaccinia virus infection of primary LCs harvested from mouse epidermis was nonpermissive, although a viral reporter protein was expressed in the infected LCs. Vaccinia virus infection of primary LCs strongly inhibited their capacity for antigen-specific activation of T cells. Our results highlight suppression of the skin immune response as a feature of orthopoxvirus infection.
Phosphorylation of MCM4 at Sites Inactivating DNA Helicase Activity of the MCM4-MCM6-MCM7 Complex during Epstein-Barr Virus Productive Replication
Authors: Kudoh Ayumi , Daikoku Tohru , Ishimi Yukio , Kawaguchi Yasushi , Shirata Noriko , Iwahori Satoko , Isomura Hiroki , Tsurumi Tatsuya 
Published: September 2006

ABSTRACT
Induction of Epstein-Barr virus (EBV) lytic replication blocks chromosomal DNA replication notwithstanding an S-phase-like cellular environment with high cyclin-dependent kinase (CDK) activity. We report here that the phosphorylated form of MCM4, a subunit of the MCM complex essential for chromosomal DNA replication, increases with progression of lytic replication, Thr-19 and Thr-110 being CDK2/CDK1 targets whose phosphorylation inactivates MCM4-MCM6-MCM7 (MCM4-6-7) complex-associated DNA helicase. Expression of EBV-encoded protein kinase (EBV-PK) in HeLa cells caused phosphorylation of these sites on MCM4, leading to cell growth arrest. In vitro, the sites of MCM4 of the MCM4-6-7 hexamer were confirmed to be phosphorylated with EBV-PK, with the same loss of helicase activity as with CDK2/cyclin A. Introducing mutations in the N-terminal six Ser and Thr residues of MCM4 reduced the inhibition by CDK2/cyclin A, while EBV-PK inhibited the helicase activities of both wild-type and mutant MCM4-6-7 hexamers, probably since EBV-PK can phosphorylate MCM6 and another site(s) of MCM4 in addition to the N-terminal residues. Therefore, phosphorylation of the MCM complex by redundant actions of CDK and EBV-PK during lytic replication might provide one mechanism to block chromosomal DNA replication in the infected cells through inactivation of DNA unwinding by the MCM4-6-7 complex.
The Amino Terminus of the Herpes Simplex Virus 1 Protein Vhs Mediates Membrane Association and Tegument Incorporation
Authors: Mukhopadhyay Aparna , Lee Grace E. , Wilson Duncan W. 
Published: September 2006

ABSTRACT

Assembly of herpes simplex viruses (HSV) is a poorly understood process involving multiple redundant interactions between large number of tegument and envelope proteins. We have previously shown (G. E. Lee, G. A. Church, and D. W. Wilson, J. Virol.
77:
2038-2045, 2003) that the virion host shutoff (Vhs) tegument protein is largely insoluble in HSV-infected cells and is also stably associated with membranes. Here we demonstrate that both insolubility and stable membrane binding are stimulated during the course of an HSV infection. Furthermore, we have found that the amino-terminal 42 residues of Vhs are sufficient to mediate membrane association and tegument incorporation when fused to a green fluorescent protein (GFP) reporter. Particle incorporation correlates with sorting to cytoplasmic punctate structures that may correspond to sites of HSV assembly. We conclude that the amino terminus of Vhs mediates targeting to sites of HSV assembly and to the viral tegument.
EBNA-3B- and EBNA-3C-Regulated Cellular Genes in Epstein-Barr Virus-Immortalized Lymphoblastoid Cell Lines
Authors: Chen Adrienne , Zhao Bo , Kieff Elliott , Aster Jon C. , Wang Fred 
Published: September 2006

ABSTRACTThe cellular pathways that Epstein-Barr virus (EBV) manipulates in order to effect its lifelong persistence within hosts and facilitate its transmission between hosts are not well understood. The EBV nuclear antigen 3 (EBNA-3) family of latent infection proteins consists of transcriptional regulators that influence viral and cellular gene expression in EBV-infected cells. To identify EBNA-3B- and EBNA-3C-regulated cellular genes potentially important for virus infection in vivo, we studied a lymphoblastoid cell line (LCL) infected with an unusual EBV mutant, where a genetic manipulation to delete EBNA-3B also resulted in a significant decrease in EBNA-3C expression and slower than normal growth (3B−/3Clow). Transcriptional profiling was performed on the 3B−/3ClowLCLs, and comparison of mutant and wild-type LCL profiles resulted in a group of 21 probe sets representing 16 individual genes showing statistically significant differences in expression. Further quantitative reverse transcription-PCR analyses comparing 3B−/3ClowLCLs to a previously described EBNA-3B mutant (3B−) where EBNA-3C expression was normal revealed three potential EBNA-3B-repressed genes, three potential EBNA-3C-repressed genes, and two potential EBNA-3C-activated genes. The most highly EBNA-3C-repressed gene was Jagged1, a cell surface ligand and inducer of the Notch receptor signaling pathway that is usurped by EBV genes essential for B-cell immortalization. 3B−/3ClowLCLs expressed increased levels of Jagged1 protein and were able to more efficiently induce functional Notch signaling, and this signaling was dependent on Notch cleavage by γ-secretase. However, inhibiting γ-secretase-mediated Notch cleavage did not rescue 3B−/3ClowLCL growth, suggesting that EBNA-3C-mediated repression of this signaling pathway did not contribute to LCL growth in tissue culture. Similarly, expression of the chemokine receptor CXCR4 was reproducibly upregulated in EBNA-3B-null LCLs. Since deletion of EBNA-3B has no significant impact on B-cell immortalization in tissue culture, this finding suggested that EBNA-3B-mediated regulation of CXCR4 may be an important viral strategy for alteration of B-cell homing in the infected host. These studies identify two cellular genes that do not contribute to EBV-induced B-cell growth but whose expression levels are strongly EBNA-3 regulated in EBV-infected primary B cells. These EBV-manipulated cellular pathways may be important for virus survival or transmission in humans, and their independence from EBV-induced B-cell growth makes them potential targets for testing in vivo with the rhesus lymphocryptovirus animal model for EBV infection.
Double-Stranded RNA Binding by a Heterodimeric Complex of Murine Cytomegalovirus m142 and m143 Proteins
Authors: Child Stephanie J. , Hanson Laura K. , Brown Crystal E. , Janzen Deanna M. , Geballe Adam P. 
Published: September 2006

ABSTRACT
In response to viral infection, cells activate a variety of antiviral responses, including several that are triggered by double-stranded (ds) RNA. Among these are the protein kinase R and oligoadenylate synthetase/RNase L pathways, both of which result in the shutoff of protein synthesis. Many viruses, including human cytomegalovirus, encode dsRNA-binding proteins that prevent the activation of these pathways and thereby enable continued protein synthesis and viral replication. We have extended these analyses to another member of the β subfamily of herpesviruses, murine cytomegalovirus (MCMV), and now report that products of the m142 and m143 genes together bind dsRNA. Coimmunoprecipitation experiments demonstrate that these two proteins interact in infected cells, consistent with their previously reported colocalization. Jointly, but not individually, the proteins rescue replication of a vaccinia virus mutant with a deletion of the dsRNA-binding protein gene E3L (VVΔE3L). Like the human cytomegalovirus dsRNA-binding protein genes TRS1 and IRS1, m142 and m143 are members of the US22 gene family. We also found that two other members of the MCMV US22 family, M23 and M24, encode dsRNA-binding proteins, but they do not rescue VVΔE3L replication. These results reveal that MCMV, like many other viruses, encodes dsRNA-binding proteins, at least two of which can inhibit dsRNA-activated antiviral pathways. However, unlike other well-studied examples, the MCMV proteins appear to act in a heterodimeric complex.
Murine Cytomegalovirus m142 and m143 Are both Required To Block Protein Kinase R-Mediated Shutdown of Protein Synthesis
Authors: Valchanova Ralitsa S. , Picard-Maureau Marcus , Budt Matthias , Brune Wolfram 
Published: September 2006

ABSTRACT
Cytomegaloviruses carry the US22 family of genes, which have common sequence motifs but diverse functions. Only two of the 12 US22 family genes of murine cytomegalovirus (MCMV) are essential for virus replication, but their functions have remained unknown. In the present study, we deleted the essential US22 family genes, m142 and m143, from the MCMV genome and propagated the mutant viruses on complementing cells. The m142 and the m143 deletion mutants were both unable to replicate in noncomplementing cells at low and high multiplicities of infection. In cells infected with the deletion mutants, viral immediate-early and early proteins were expressed, but viral DNA replication and synthesis of the late-gene product glycoprotein B were inhibited, even though mRNAs of late genes were present. Global protein synthesis was impaired in these cells, which correlated with phosphorylation of the double-stranded RNA-dependent protein kinase R (PKR) and its target protein, the eukaryotic translation initiation factor 2α, suggesting that m142 and m143 are necessary to block the PKR-mediated shutdown of protein synthesis. Replication of the m142 and m143 knockout mutants was partially restored by expression of the human cytomegalovirus TRS1 gene, a known double-stranded-RNA-binding protein that inhibits PKR activation. These results indicate that m142 and m143 are both required for inhibition of the PKR-mediated host antiviral response.
RNA Silencing Suppression by a Second Copy of the P1 Serine Protease ofCucumber Vein Yellowing Ipomovirus, a Member of the FamilyPotyviridaeThat Lacks the Cysteine Protease HCPro
Authors: Valli Adrian , Martín-Hernández Ana Montserrat , López-Moya Juan José , García Juan Antonio 
Published: September 2006

ABSTRACTThe P1 protein of viruses of the familyPotyviridaeis a serine proteinase, which is highly variable in length and sequence, and its role in the virus infection cycle is not clear. One of the proposed activities of P1 is to assist HCPro, the product that viruses of the genusPotyvirususe to counteract antiviral defense mediated by RNA silencing. Indeed, an HCPro-coding region is present in all the genomes of members of the generaPotyvirus,Rymovirus, andTritimovirusthat have been sequenced. However, it was recently reported that a sequence coding for HCPro is lacking in the genome ofCucumber vein yellowing virus(CVYV), a member of the genusIpomovirus, the fourth monopartite genus of the family. In this study, we provide further evidence that P1 enhances the activity of HCPro in members of the genusPotyvirusand show that it is duplicated in the ipomovirus CVYV. The two CVYV P1 copies are arranged in tandem, and the second copy (P1b) has RNA silencing suppression activity. CVYV P1b suppressed RNA silencing induced either by sense green fluorescent protein (GFP) mRNA or by a GFP inverted repeat RNA, indicating that CVYV P1b acts downstream of the formation of double-stranded RNA. CVYV P1b also suppressed local silencing in agroinfiltrated patches of transgenicNicotiana benthamianaline 16c and delayed its propagation to the neighboring cells. However, neither the short-distance nor long-distance systemic spread of silencing of the GFP transgene was completely blocked by CVYV P1b. CVYV P1b and P1-HCPro from the potyvirusPlum pox virusshowed very similar behaviors in all the assays carried out, suggesting that evolution has found a way to counteract RNA silencing by similar mechanisms using very different proteins in viruses of the same family.
trans
Regulation of Cap-Independent Translation by a Viral Subgenomic RNA
Authors: Shen Ruizhong , Rakotondrafara Aurélie M. , Miller W. Allen 
Published: September 2006

ABSTRACT

Many positive-strand RNA viruses generate 3′-coterminal subgenomic
mRNAs to allow translation of 5′-distal open reading frames. It
is unclear how viral genomic and subgenomic mRNAs compete with each
other for the cellular translation machinery. Translation of the
uncapped Barley yellow dwarf virus genomic RNA (gRNA) and subgenomic
RNA1 (sgRNA1) is driven by the powerful cap-independent translation
element (BTE) in their 3′ untranslated regions (UTRs). The BTE
forms a kissing stem-loop interaction with the 5′ UTR to
mediate translation initiation at the 5′ end. Here, using
reporter mRNAs that mimic gRNA and sgRNA1, we show that the abundant
sgRNA2 inhibits translation of gRNA, but not sgRNA1, in vitro and in
vivo. This
trans
inhibition requires the functional BTE in the
5′ UTR of sgRNA2, but no translation of sgRNA2 itself is
detectable. The efficiency of translation of the viral mRNAs in the
presence of sgRNA2 is determined by proximity to the mRNA 5′
end of the stem-loop that kisses the 3′ BTE. Thus, the gRNA and
sgRNA1 have “tuned” their expression efficiencies via
the site in the 5′ UTR to which the 3′ BTE base pairs.
We conclude that sgRNA2 is a riboregulator that switches off
translation of replication genes from gRNA while permitting translation
of structural genes from sgRNA1. These results reveal (i) a new level
of control of subgenomic-RNA gene expression, (ii) a new role for a
viral subgenomic RNA, and (iii) a new mechanism for RNA-mediated
regulation of
translation.
Human Cytomegalovirus UL84 Protein Contains Two Nuclear Export Signals and Shuttles between the Nucleus and the Cytoplasm
Authors: Lischka Peter , Rauh Claudia , Mueller Regina , Stamminger Thomas 
Published: September 2006

ABSTRACT
Previous studies defined pUL84 of human cytomegalovirus as an essential regulatory protein with nuclear localization that was proposed to act during initiation of viral-DNA synthesis. Recently, we demonstrated that a complex domain of 282 amino acids within pUL84 functions as a nonconventional nuclear localization signal. Sequence inspection of this domain revealed the presence of motifs with homology to leucine-rich nuclear export signals. Here, we report the identification of two functional, autonomous nuclear export signals and show that pUL84 acts as a CRM-1-dependent nucleocytoplasmic shuttling protein. This suggests an unexpected cytoplasmic role for this essential viral regulatory protein.
Induction of Innate Immunity against Herpes Simplex Virus Type 2 Infection via Local Delivery of Toll-Like Receptor Ligands Correlates with Beta Interferon Production
Authors: Gill Navkiran , Deacon Philip M. , Lichty Brian , Mossman Karen L. , Ashkar Ali A. 
Published: September 2006

ABSTRACT

Toll-like receptors (TLRs) constitute a family of innate receptors that recognize and respond to a wide spectrum of microorganisms, including fungi, bacteria, viruses, and protozoa. Previous studies have demonstrated that ligands for TLR3 and TLR9 induce potent innate antiviral responses against herpes simplex virus type 2 (HSV-2). However, the factor(s) involved in this innate protection is not well-defined. Here we report that production of beta interferon (IFN-β) but not production of IFN-α, IFN-γ, or tumor necrosis factor alpha (TNF-α) strongly correlates with innate protection against HSV-2. Local delivery of poly(I:C) and CpG oligodeoxynucleotides induced significant production of IFN-β in the genital tract and provided complete protection against intravaginal (IVAG) HSV-2 challenge. There was no detectable IFN-β in mice treated with ligands for TLR4 or TLR2, and these mice were not protected against subsequent IVAG HSV-2 challenge. There was no correlation between levels of TNF-α or IFN-γ in the genital tract and protection against IVAG HSV-2 challenge following TLR ligand delivery. Both TNF-α
−/−
and IFN-γ
−/−
mice were protected against IVAG HSV-2 challenge following local delivery of poly(I:C). To confirm that type I interferon, particularly IFN-β, mediates innate protection, mice unresponsive to type I interferons (IFN-α/βR
−/−
mice) and mice lacking IFN regulatory factor-3 (IRF-3
−/−
mice) were treated with poly(I:C) and then challenged with IVAG HSV-2. There was no protection against HSV-2 infection following poly(I:C) treatment of IFN-α/βR
−/−
or IRF-3
−/−
mice. Local delivery of murine recombinant IFN-β protected C57BL/6 and IRF-3
−/−
mice against IVAG HSV-2 challenge. Results from these in vivo studies clearly suggest a strong correlation between IFN-β production and innate antiviral immunity against HSV-2.
Production of Infectious Hepatitis C Virus by Well-Differentiated, Growth-Arrested Human Hepatoma-Derived Cells
Authors: Sainz Bruno , Chisari Francis V. 
Published: September 2006

ABSTRACTDimethyl sulfoxide (DMSO) has been shown to induce the differentiation of primary hepatocytes in vitro. When actively dividing poorly differentiated human hepatoma-derived (Huh7) cells were cultured in the presence of 1% DMSO, cells became cytologically differentiated and transitioned into a nondividing state, characterized by the induction of hepatocyte-specific genes. Moreover, these cells were highly permissive for acute hepatitis C virus (HCV) infection, and persistent long term infection of these cultures could also be achieved. As HCV naturally replicates in highly differentiated nondividing human hepatocytes, this system may more accurately mimic the conditions under which HCV replicates in vivo than previous models using poorly differentiated rapidly dividing hepatoma cells.
Quantification of Poly(I:C)-Mediated Protection against Genital Herpes Simplex Virus Type 2 Infection
Authors: Herbst-Kralovetz Melissa M. , Pyles Richard B. 
Published: September 2006

ABSTRACTAlternative strategies for controlling the growing herpes simplex virus type 2 (HSV-2) epidemic are needed. A novel class of immunomodulatory microbicides has shown promise as antiherpetics, including intravaginally applied CpG-containing oligodeoxynucleotides that stimulate toll-like receptor 9 (TLR9). In the current study, we quantified protection against experimental genital HSV-2 infection provided by an alternative nucleic acid-based TLR agonist, polyinosine-poly(C) (PIC) (TLR3 agonist). Using a protection quantification paradigm, groups of mice were PIC treated and then subdivided into groups challenged with escalating doses of HSV-2. Using this paradigm, a temporal window of PIC efficacy for single applications was defined as 1 day prior to (prophylactic) through 4 h after (therapeutic) viral challenge. PIC treatment within this window protected against 10-fold-higher HSV-2 challenges, as indicated by increased 50% infectious dose values relative to those for vehicle-treated controls. Disease resolution and survival were significantly enhanced by repetitive PIC doses. Using optimal PIC regimens, cytokine induction was evaluated in murine vaginal lavages and in human vaginal epithelial cells. Similar induction patterns were observed, with kinetics that explained the limited durability of PIC-afforded protection. Daily PIC delivery courses did not generate sustained cytokine levels in murine vaginal fluids that would be indicative of local immunotoxicity. No evidence of immunotoxicity was observed in selected organs that were analyzed following repetitive vaginal PIC doses. Animal and in vitro data indicate that PIC may prove to be a valuable preventative microbicide and/or therapeutic agent against genital herpes by increasing resistance to HSV-2 and enhancing disease resolution following a failure of prevention.