bluuebunny/crossref_metadata_2025_split huggingface dataset:
Measles Virus DNA Vaccination: Antibody Isotype Is Determined by the Method of Immunization and by the Nature of both the Antigen and the Coimmunized Antigen
Authors: Cardoso Alicia I. , Sixt Nathalie , Vallier Agnes , Fayolle Joel , Buckland Robin , Wild T. Fabian 
Published: December 2019

ABSTRACTPlasmids encoding the measles virus hemagglutinin (HA) and nucleoprotein (NP) proteins inoculated into the skin of BALB/c mice by the gene gun method induced both humoral and cytotoxic lymphocyte class I-restrict- ed immune responses. Although intramuscular immunization induces the immunoglobulin G2a (IgG2a) antibody isotype for both antigens, with gene gun immunization, the NP still generated mainly IgG2a and the major isotype induced by the HA was IgG1. Interestingly, gene gun coimmunization of HA and NP plasmids resulted in a dominant IgG1 HA response and the switching of antibodies generated against the NP to the IgG1 isotype.
The Glycoprotein D (US6) Homolog Is Not Essential for Oncogenicity or Horizontal Transmission of Marek’s Disease Virus
Authors: Anderson Amy S. , Parcells Mark S. , Morgan Robin W. 
Published: December 2019

ABSTRACT

RB1BUS6
lacgpt
, a Marek’s disease virus (MDV) mutant having a disrupted glycoprotein D (gD) homolog gene, established infection and induced tumors in chickens exposed to it by inoculation or by contact. Lymphoblastoid cell lines derived from RB1BUS6
lacgpt
-induced tumors harbored only the mutant virus. These results provide strong evidence that an intact gD homolog gene is not essential for oncogenicity or horizontal transmission of MDV.
Glucagon Treatment Interferes with an Early Step of Duck Hepatitis B Virus Infection
Authors: Hild Marc , Weber Olaf , Schaller Heinz 
Published: December 2019

ABSTRACT
The effect of glucagon on the establishment of hepadnavirus infection was studied in vitro with the duck hepatitis B virus (DHBV) model. The presence of the peptide hormone throughout infection or starting up to 8 h after virus uptake resulted in a dose-dependent reduction in the levels of intra- and extracellular viral gene products and of secreted virions. Treatment with forskolin or dibutyryl-cyclic AMP, two drugs that also stimulate the cyclic AMP (cAMP) signal transduction pathway, resulted in comparable inhibition, suggesting that the inhibitor effect is related to changes in the activity of protein kinase A. In persistently infected hepatocytes, only a slight, but continuous, decrease in viral replication was observed upon prolonged drug treatment. Time course analysis, including detection of DHBV covalently closed circular (ccc) DNA templates, revealed that glucagon acts late during the establishment of infection, at a time when the virus is already internalized, but before detectable ccc DNA accumulation in the nucleus. These data suggest that nuclear import (and reimport) of DHBV DNA genomes from cytosolic capsids is subject to cAMP-mediated regulation by cellular factors responding to changes in the state of the host cell.
Mutation of the Lck-Binding Motif of Tip Enhances Lymphoid Cell Activation by Herpesvirus Saimiri
Authors: Duboise S. Monroe , Lee Heuiran , Guo Jie , Choi Joong-Kook , Czajak Susan , Simon Meredith , Desrosiers Ronald C. , Jung Jae U. 
Published: December 2019

ABSTRACTThe proline-rich SH3-binding (SH3B) motif of the tyrosine kinase-interacting protein (Tip) of herpesvirus saimiri (HVS) is required for binding to the cellular Src family kinase Lck. We constructed a mutant form of HVS in which prolines in the SH3B motif of Tip were altered to alanines. This mutant form of Tip was incapable of binding to Lck. The mutant virus, HVS/Tip mSH3B, retained its ability to immortalize common marmoset lymphocytes in culture. In fact, common marmoset lymphocytes immortalized by the HVS/Tip mSH3B mutant displayed increased expression of HLA-DR lymphocyte activation marker, an altered pattern of tyrosine phosphorylation, increased expression of the tyrosine kinase Lyn, and a shift in electrophoretic mobility of Lck compared to cells immortalized by wild-type HVS. Experimental infection of common marmosets resulted in fulminant lymphoma with both HVS/Tip mSH3B and wild-type HVS. However, HVS/Tip mSH3B produced greater infiltration of affected organs by proliferating lymphoid cells compared to wild-type HVS. These results demonstrate that Tip binding to Lck is not necessary for transformation and that abrogation of Tip binding to Lck alters the characteristics of transformed cells and the severity of the pathologic lesions.
Separate DNA Elements Containing ATF/CREB and IE86 Binding Sites Differentially Regulate the Human Cytomegalovirus UL112-113 Promoter at Early and Late Times in the Infection
Authors: Rodems Steven M. , Clark Charles L. , Spector Deborah H. 
Published: December 2019

ABSTRACT

The human cytomegalovirus (HCMV) UL112-113 promoter represents a useful model for studying temporal regulation of viral gene expression. Stimulation of this promoter by the 86-kDa immediate-early protein (IE86) is controlled by sequences between nucleotides −113 and −59, which include both an ATF/CREB and an IE86 binding site. In transient assays, the ATF/CREB site is essential, and the IE86 site, although nonessential, can enhance transcription. With recombinant viruses, we have assessed the function of these promoter elements in the context of the viral genome. Transcription from the inserted UL112-113 promoter shows the same temporal pattern as the endogenous promoter, including the switch to an upstream RNA start site late in infection. Deletion of sequences containing the IE86 site results in a decrease in the level of early transcription and elimination of late transcription. In contrast, when the ATF/CREB site is deleted, early RNA synthesis is almost completely abolished, but late transcription is comparable to that of the wild type, with repositioning of the RNA start site downstream by the number of nucleotides deleted. Replacement of sequences between −108 and −95 with the HCMV
cis
-repression signal from the major immediate-early promoter had no effect on the level of late RNAs but resulted in the repositioning of the RNA start site 39 nucleotides upstream. These results suggest that the ATF/CREB site is functional only at early times, while sequences containing the IE86 site modulate the level of early RNAs and may be required for activating late transcription in a distance-dependent manner.
Herpes Simplex Virus DNA Packaging without Measurable DNA Synthesis
Authors: Church Geoffrey A. , Dasgupta Anindya , Wilson Duncan W. 
Published: December 2019

ABSTRACT

Herpes simplex virus (HSV) type 1 DNA synthesis and packaging occur within the nuclei of infected cells; however, the extent to which the two processes are coupled remains unclear. Correct packaging is thought to be dependent upon DNA debranching or other repair processes, and such events commonly involve new DNA synthesis. Furthermore, the HSV UL15 gene product, essential for packaging, nevertheless localizes to sites of active DNA replication and may link the two events. It has previously been difficult to determine whether packaging requires concomitant DNA synthesis due to the complexity of these processes and of the viral life cycle; however, we have recently described a model system which simplifies the study of HSV assembly. Cells infected with HSV strain
ts
Prot.A accumulate unpackaged capsids at the nonpermissive temperature of 39°C. Following release of the temperature block, these capsids proceed to package viral DNA in a single, synchronous wave. Here we report that, when DNA replication was inhibited prior to release of the temperature block, DNA packaging and later events in viral assembly nevertheless occurred at near-normal levels. We conclude that, under our conditions, HSV DNA packaging does not require detectable levels of DNA synthesis.
Genotype-Specific Complementation of Hepatitis Delta Virus RNA Replication by Hepatitis Delta Antigen
Authors: Casey John L. , Gerin John L. 
Published: December 2019

ABSTRACT
Characterizations of genetic variations among hepatitis delta virus (HDV) isolates have focused principally on phylogenetic analysis of sequences, which vary by 30 to 40% among three genotypes and about 10 to 15% among isolates of the same genotype. The significance of the sequence differences has been unclear but could be responsible for pathogenic variations associated with the different genotypes. Studies of the mechanisms of HDV replication have been limited to cDNA clones from HDV genotype I, which is the most common. To perform a comparative analysis of HDV RNA replication in genotypes I and III, we have obtained a full-length cDNA clone from an HDV genotype III isolate. In transfected Huh-7 cells, the functional roles of the two forms of the viral protein, hepatitis delta antigen (HDAg), in HDV RNA replication are similar for both genotypes I and III; the short form is required for RNA replication, while the long form inhibits replication. For both genotypes, HDAg was able to support replication of RNAs of the same genotype that were mutated so as to be defective for HDAg production. Surprisingly, however, neither genotype I nor genotype III HDAg was able to support replication of such mutated RNAs of the other genotype. The inability of genotype III HDAg to support replication of genotype I RNA could have been due to a weak interaction between the RNA and HDAg. The clear genotype-specific activity of HDAg in supporting HDV RNA replication confirms the original categorization of HDV sequences in three genotypes and further suggests that these should be referred to as types (i.e., HDV-I and HDV-III) rather than genotypes.
Specific Interactions between Retrovirus Env and Gag Proteins in Rat Neurons
Authors: Weclewicz Katarzyna , Ekström Maria , Kristensson Krister , Garoff Henrik 
Published: December 2019

ABSTRACT

In this work we have studied the intracellular localization properties of the Gag and Env proteins of Moloney murine leukemia virus (MLV) and human immunodeficiency virus (HIV) in dorsal root ganglion (DRG) neurons of rat. These neurons form thick bundles of axons, which facilitates protein localization studies by immunofluorescence analyses. When such neuron cultures were infected with recombinant Semliki Forest virus particles carrying the
gag
genes of either retrovirus, the expressed Gag proteins were localized to both the somatic and the axonal regions of the DRG neurons. In contrast, the Env proteins were confined only to the somatic region. When the Gag and Env proteins were coexpressed, the Gag proteins were also excluded from the axons. This effect of the Env proteins was shown to be dependent on the concentration of the Gag proteins in the neuron and also to be specific for homologous pairs of retrovirus proteins. Therefore, the results suggest that there are specific interactions between the Env and the Gag proteins of MLV and HIV in the DRG neurons.
Increased Induction of Apoptosis by a Sendai Virus Mutant Is Associated with Attenuation of Mouse Pathogenicity
Authors: Itoh Masae , Hotta Hak , Homma Morio 
Published: December 2019

ABSTRACT

An avirulent mutant of Sendai virus, Ohita-MVC11 (MVC11), was generated from a highly virulent field strain, Ohita-M1 (M1), through successive passages in LLC-MK
2
cell cultures (M. Itoh, Y. Isegawa, H. Hotta, and M. Homma, J. Gen. Virol. 78:3207-3215, 1997). In LLC-MK
2
cells, MVC11 induced a high degree of apoptotic cell death that was demonstrated by chromatin condensation of the nucleus and DNA fragmentation, and production of MVC11 declined markedly after prolonged culture. On the other hand, M1 did not induce prominent apoptosis and maintained high virus titers. In primary mouse pulmonary epithelial cell cultures, M1 replicated rather slowly to reach maximum level of virus production at 3 days postinfection, and high levels of virus production were maintained thereafter without causing apoptosis. In contrast, MVC11, which produced 20 times more progeny virus than M1 at 1 day postinfection, induced a high degree of apoptotic cell death before the virus replication cycle was completed. Accordingly, the production of progeny virus was strongly inhibited thereafter. In the lungs of mice infected with MVC11, virus antigens and signals of DNA fragmentation detected by the in situ terminal deoxynucleotidyltransferase-mediated dUTP nick end-labeling technique colocalized in bronchial epithelial cells, clearly demonstrating that infection by MVC11 triggered apoptosis in vivo as well as in vitro. These results suggest the possibility that induction of apoptosis by MVC11 plays an important role in attenuation of mouse pathogenicity by restricting progeny virus production in the lung. The C protein was shown to have the capacity to induce apoptosis, and the increased level of the C protein in MVC11-infected cells was considered to account partly, if not entirely, for the induction of apoptosis.
Human Parvovirus B19 Nonstructural (NS1) Protein Induces Apoptosis in Erythroid Lineage Cells
Authors: Moffatt Stanley , Yaegashi Nobuo , Tada Kohtaro , Tanaka Nobuyuki , Sugamura Kazuo 
Published: December 2019

ABSTRACTInfection of erythroid-lineage cells by human parvovirus B19 is characterized by a gradual cytocidal effect. Accumulating evidence now implicates the nonstructural (NS1) protein of the virus in cytotoxicity, but the mechanism underlying the NS1-induced cell death is not known. Using a stringent regulatory system, we demonstrate that NS1 cytotoxicity is closely related to apoptosis, as evidenced by cell morphology, genomic DNA fragmentation, and cell cycle analysis with the human erythroleukemia cell line K562 and the erythropoietin-dependent megakaryocytic cell line UT-7/Epo. Apoptosis was significantly inhibited by an interleukin-1β (IL-1β)-converting enzyme (ICE)/CED-3 family protease inhibitor, Ac-DEVD-CHO (CPP32; caspase 3), whereas a similar inhibitor of ICE (caspase 1), Ac-YVAD-CHO, had no effect. Furthermore, stable expression of the human Bcl-2 proto-oncogene resulted in near-total protection from cell death in response to NS1 induction. Mutations engineered into the nucleoside triphosphate-binding domain of NS1 significantly rescued cells from NS1-induced apoptosis without having any effect on NS1-induced activation of the IL-6 gene expression which is mediated by NF-κB. Furthermore, using pentoxifylline, an inhibitor of NF-κB activation, we demonstrate that the NF-κB-mediated IL-6 activation by NS1 is uncoupled from the apoptotic pathway. This functional dissection indicates a complexity underlying the biochemical function of human parvovirus NS1 in transcriptional activation and induction of apoptosis. Our findings indicate that NS1 of parvovirus B19 induces cell death by apoptosis in at least erythroid-lineage cells by a pathway that involves caspase 3, whose activation may be a key event during NS1-induced cell death.
Detection of Hepatitis G Virus Replication Sites by Using Highly Strand-Specific Tth-Based Reverse Transcriptase PCR
Authors: Laskus Tomasz , Radkowski Marek , Wang Lian-Fu , Vargas Hugo , Rakela Jorge 
Published: December 2019

ABSTRACT
The replication sites of the recently discovered hepatitis G virus (HGV) remain unknown. Using highly strand-specific Tth-based reverse transcriptase PCR, we searched for the presence of viral RNA negative strand in multiple autopsy tissues from four patients with AIDS and in peripheral blood mononuclear cells from six other human immunodeficiency virus-positive patients. Negative-strand HGV RNA was detected in three of four bone marrow samples, in two of two spleen samples, and in one of four liver tissue samples. However, the specific cellular site of replication within the positive tissues was not determined. This study does not support HGV as a primary hepatotropic virus.
Viruses and Cells with Mutations Affecting Viral Entry Are Selected during Persistent Rotavirus Infections of MA104 Cells
Authors: Mrukowicz Jacek Z. , Wetzel J. Denise , Goral Mehmet I. , Fogo Agnes B. , Wright Peter F. , Dermody Terence S. 
Published: December 2019

ABSTRACT

To better understand mechanisms of persistent rotavirus infections of cultured cells, we established independent, persistently infected cultures of MA104 cells, using rotavirus strain SA11. The cultures were either passaged when the cells reached confluence or supplemented with fresh medium every 7 days. Viral titers in culture lysates varied from 10
4
to 10
7
PFU per ml during 350 days of culture maintenance. Trypan blue staining indicated that 72 to 100% of cells in the cultures were viable, and immunocytochemical staining using a monoclonal antibody directed against viral protein VP6 demonstrated that 38 to 63% of the cells contained rotavirus antigen. We tested the capacity of rotaviruses isolated from the persistently infected cultures (PI viruses) to infect cells cured of persistent infection. Although wild-type (wt) and PI viruses produced equivalent yields in parental MA104 cells, PI viruses produced greater yields than wt virus in cured cells, which indicates that viruses and cells coevolve during persistent rotavirus infections of MA104 cells. To determine whether mutations in viruses and cells selected during these persistent infections affect viral entry, we tested the effect of trypsin treatment of the viral inoculum on growth of wt and PI viruses. Trypsin pretreatment is required for postattachment penetration of rotavirus virions into cells. In contrast to the case with wt virus, PI viruses produced equivalent yields with and without trypsin pretreatment in parental MA104 cells. However, PI viruses required trypsin pretreatment for efficient growth in cured cells. These results indicate that mutant viruses and cells are selected during maintenance of persistent rotavirus infections of MA104 cells and suggest that mutations in each affect trypsin-dependent steps in rotavirus entry.
CBF, Myb, and Ets Binding Sites Are Important for Activity of the Core I Element of the Murine Retrovirus SL3-3 in T Lymphocytes
Authors: Zaiman Ari L. , Nieves Angel , Lenz Jack 
Published: December 2019

ABSTRACTTranscriptional enhancers within the long terminal repeats of murine leukemia viruses are major determinants of the pathogenic properties of these viruses. Mutations were introduced into the adjacent binding sites for three transcription factors within the enhancer of the T-cell-lymphomagenic virus SL3-3. The sites that were tested were, in 5′-to-3′ order, a binding site for core binding factor (CBF) called core II, a binding site for c-Myb, a site that binds members of the Ets family of factors, and a second CBF binding site called core I. Mutation of each site individually reduced transcriptional activity in T lymphocytes. However, mutation of the Myb and core I binding sites had larger effects than mutation of the Ets or core II site. The relative effects on transcription in T cells paralleled the effects of the same mutations on viral lymphomagenicity, consistent with the idea that the role of these sequences in viral lymphomagenicity is indeed to regulate transcription in T cells. Mutations were also introduced simultaneously into multiple sites in the SL3-3 enhancer. The inhibitory effects of these mutations indicated that the transcription factor in T cells that recognizes the core I element of SL3-3, presumably CBF, needed to synergize with one or more factors bound at the upstream sites to function. This was tested further by generating a multimer construct that contained five tandem core I elements linked to a basal long terminal repeat promoter. This construct was inactive in T cells. However, transcriptional activity was detected with a multimer construct in which the transcription factor binding sites upstream of the core were also present. These results are consistent with the hypothesis that CBF requires heterologous transcription factors bound at nearby sites to function in T cells.
Progression to the G1b Phase of the Cell Cycle Is Required for Completion of Human Immunodeficiency Virus Type 1 Reverse Transcription in T Cells
Authors: Korin Yael D. , Zack Jerome A. 
Published: December 2019

ABSTRACTSuccessful infection by human immunodeficiency virus type 1 (HIV-1) requires the activation of target cells. Infection of quiescent peripheral CD4 lymphocytes by HIV-1 results in incomplete, labile, reverse transcripts. In the present study, we isolated highly purified quiescent T cells and utilized the CD3/CD28 activation pathways as well as cell cycle inhibitors to further define the role of costimulation and cell cycle progression in HIV-1 reverse transcription. Activation with αCD3 alone resulted in cell cycle progression into only G1a and incomplete HIV-1 reverse transcription. Costimulation through the CD28 receptor and transition into G1b was required to efficiently complete the reverse transcription process. These findings have relevance to immune activation in vivo, since lymphocytes rendered anergic by a single activation signal would be nonpermissive for productive infection with HIV-1. Importantly, these data also suggest that HIV vector-based genetic transduction strategies might be successful only in target cells that transition into the G1b phase of the cell cycle.
Loss of Viral Fitness Associated with Multiple Gag and Gag-Pol Processing Defects in Human Immunodeficiency Virus Type 1 Variants Selected for Resistance to Protease Inhibitors In Vivo
Authors: Zennou Véronique , Mammano Fabrizio , Paulous Sylvie , Mathez Dominique , Clavel François 
Published: December 2019

ABSTRACT
We examined the viral replicative capacity and protease-mediated processing of Gag and Gag-Pol precursors of human immunodeficiency virus (HIV) variants selected for resistance to protease inhibitors. We compared recombinant viruses carrying plasma HIV RNA protease sequences obtained from five patients before protease inhibitor therapy and after virus escape from the treatment. Paired pretherapy-postresistance reconstructed viruses were evaluated for HIV infectivity in a quantitative single-cycle titration assay and in a lymphoid cell propagation assay. We found that all reconstructed resistant viruses had a reproducible decrease in their replicative capacity relative to their parental pretherapy counterparts. The extent of this loss of infectivity was pronounced for some viruses and more limited for others, irrespective of the inhibitor used and of the level of resistance. In resistant viruses, the efficiency of Gag and Gag-Pol precursor cleavage by the protease was impaired to different extents, as shown by the accumulation of several cleavage intermediates in purified particle preparations. We conclude that protease inhibitor-resistant HIV variants selected during therapy have an impaired replicative capacity related to multiple defects in the processing of Gag and Gag-Pol polyprotein precursors by the protease.
Efficient Expression and Rapid Purification of Human T-Cell Leukemia Virus Type 1 Protease
Authors: Ding Y. Shirley , Owen Sherry M. , Lal Renu B. , Ikeda Richard A. 
Published: December 2019

ABSTRACT

Human T-cell leukemia virus type 1 (HTLV-1) is an oncovirus that is clinically associated with adult T-cell leukemia. We report here the construction of a pET19-based expression clone containing HTLV-1 protease fused to a decahistidine-containing leader peptide. The recombinant protein is efficiently expressed in
Escherichia coli
, and the fusion protein can be easily purified by affinity chromatography. Active mature protease in yields in excess of 3 mg/liter of culture can then be obtained by a novel two-step refolding and autoprocessing procedure. The purified enzyme exhibited

K
m

and
K
cat
values of 0.3 mM and 0.143 sec
−1
at pH 5.3 and was inhibited by pepstatin A.