bluuebunny/crossref_metadata_2025_split huggingface dataset:
Antiprion Activity of Cholesterol Esterification Modulators: a Comparative Study Using Ex Vivo Sheep Fibroblasts and Lymphocytes and Mouse Neuroblastoma Cell Lines
Authors: Pani Alessandra , Norfo Claudia , Abete Claudia , Mulas Claudia , Putzolu Marirosa , Laconi Sergio , Orrù Christina Doriana , Cannas M. Dolores , Vascellari Sarah , La Colla Paolo , Dessì Sandra 
Published: August 2007

ABSTRACT

Our studies on the role of cholesterol homeostasis in the pathogenesis of scrapie revealed abnormal accumulation of cholesterol esters in ex vivo peripheral blood mononuclear cells (PBMCs) and skin fibroblasts from healthy and scrapie-affected sheep carrying a scrapie-susceptible genotype compared to sheep with a resistant genotype. Similar alterations were observed in mouse neuroblastoma N2a cell lines persistently infected with mouse-adapted 22L and RML strains of scrapie that showed up to threefold-higher cholesterol ester levels than parental N2a cells. We now report that proteinase K-resistant prion protein (PrPres)-producing cell populations of subclones from scrapie-infected cell lines were characterized by higher cholesterol ester levels than clone populations not producing PrPres. Treatments with a number of drugs known to interfere with different steps of cholesterol metabolism strongly reduced the accumulation of cholesterol esters in ex vivo PBMCs and skin fibroblasts from scrapie-affected sheep but had significantly less or no effect in their respective scrapie-resistant or uninfected counterparts. In scrapie-infected N2a cells, inhibition of cholesterol esters was associated with selective antiprion activity. Effective antiprion concentrations of cholesterol modulators (50% effective concentration [EC
50
] range, 1.4 to 40 μM) were comparable to those of antiprion reference compounds (EC
50
range, 0.6 to 10 μM). These data confirm our hypothesis that abnormal accumulation of cholesterol esters may represent a biological marker of susceptibility to prion infection/replication and a novel molecular target of potential clinical importance.
Functional Characterization of TcaA: Minimal Requirement for Teicoplanin Susceptibility and Role in
Caenorhabditis elegans
Virulence
Authors: McCallum Nadine , Brassinga Ann Karen C. , Sifri Costi D. , Berger-Bächi Brigitte 
Published: August 2007

ABSTRACT

The inactivation of TcaA contributes to intrinsic teicoplanin resistance in experimental and clinical isolates of glycopeptide-intermediate resistant
Staphylococcus aureus
. PhoA fusions confirmed that TcaA is a transmembrane protein with a short intracellular N-terminal domain containing a C-4 zinc finger binding motif, a single membrane-spanning domain, and a large extracellular C-terminal domain. The region conferring teicoplanin susceptibility was narrowed down to the transmembrane part and the first third of the extracellular domain of TcaA, suggesting that neither the C-4 zinc finger binding motif nor the C terminus contributed to teicoplanin susceptibility. TcaA belongs to the cell wall stress stimulon, which comprises a set of genes universally upregulated by cell wall damage. Induction of
tcaA
was shown to be fully dependent on the two-component regulatory system VraSR. A 66-bp region upstream of the transcriptional start site, which contained an inverted repeat partially covering the promoter box, was shown to be essential for VraSR-mediated induction by cell wall stress. Interestingly, the induction or overexpression of
tcaA
did not contribute further to teicoplanin susceptibility, suggesting that small amounts of TcaA, such as those present under normal uninduced conditions, were sufficient for TcaA-mediated teicoplanin susceptibility. The strong attenuation of
tcaA
deletion mutants in a
Caenorhabditis elegans
survival assay suggested that TcaA may, in addition to affecting glycopeptide susceptibility, also play a role in virulence.
Growth and Drug Resistance Phenotypes Resulting from Cytomegalovirus DNA Polymerase Region III Mutations Observed in Clinical Specimens
Authors: Chou Sunwen , Marousek Gail I. , Van Wechel Laura C. , Li Shaobing , Weinberg Adriana 
Published: August 2007

ABSTRACT

Recombinant phenotyping of cytomegalovirus (CMV)
pol
region III mutations from clinical specimens showed that T813S and G841A each conferred foscarnet resistance and approximately threefold increased ganciclovir resistance; adding the UL97 mutation C592G increased ganciclovir resistance to approximately sixfold. Bacterial artificial chromosome CMV clones containing
pol
mutation L845P were nonviable unless repaired with the wild-type sequence.
Composite Structure of
Streptococcus pneumoniae
Containing the Erythromycin Efflux Resistance Gene
mef
(I) and the Chloramphenicol Resistance Gene
catQ
Authors: Mingoia Marina , Vecchi Manuela , Cochetti Ileana , Tili Emily , Vitali Luca A. , Manzin Aldo , Varaldo Pietro E. , Montanari Maria Pia 
Published: August 2007

ABSTRACT

In recent years
mef
genes, encoding efflux pumps responsible for M-type macrolide resistance, have been investigated extensively for streptococci.
mef
(I) is a recently described
mef
variant detected in particular isolates of
Streptococcus pneumoniae
instead of the more common
mef
(E) and
mef
(A). This study shows that
mef
(I) is located in a new composite genetic element, whose sequence was completely analyzed and the left and right junctions determined, demonstrating a unique genetic organization. The new composite structure (30,505 bp), designated the 5216IQ complex, consists of two halves: a left one (15,316 bp) formed by parts of the known transposons Tn
5252
and Tn
916
, and a right one (15,115 bp) formed by a new fragment, designated the IQ element. While the defective Tn
916
contained a silent
tet
(M) gene, the IQ element, ending with identical transposase genes on both sides and containing the
mef
(I) gene with an adjacent new
msr
(D) gene variant and a
catQ
chloramphenicol acetyltransferase gene, was completely different from the genetic elements carrying other
mef
genes in pneumococci. This is the first report demonstrating
catQ
in
S. pneumoniae
and showing its linkage with a
mef
gene. Analysis of the chromosomal region beyond the left junction revealed an organization more similar to that of
S. pneumoniae
strain TIGR4 than to that of strain R6. The 5216IQ complex was apparently nonmobile, with no detectable transfer of erythromycin resistance being obtained in repeated transformation and conjugation assays.
Cyclic Tetrapyrrole Sulfonation, Metals, and Oligomerization in Antiprion Activity
Authors: Caughey Winslow S. , Priola Suzette A. , Kocisko David A. , Raymond Lynne D. , Ward Anne , Caughey Byron 
Published: August 2007

ABSTRACT
Cyclic tetrapyrroles are among the most potent compounds with activity against transmissible spongiform encephalopathies (TSEs; or prion diseases). Here the effects of differential sulfonation and metal binding to cyclic tetrapyrroles were investigated. Their potencies in inhibiting disease-associated protease-resistant prion protein were compared in several types of TSE-infected cell cultures. In addition, prophylactic antiscrapie activities were determined in scrapie-infected mice. The activity of phthalocyanine was relatively insensitive to the number of peripheral sulfonate groups but varied with the type of metal bound at the center of the molecule. The tendency of the various phthalocyanine sulfonates to oligomerize (i.e., stack) correlated with anti-TSE activity. Notably, aluminum(III) phthalocyanine tetrasulfonate was both the poorest anti-TSE compound and the least prone to oligomerization in aqueous media. Similar comparisons of iron- and manganese-bound porphyrin sulfonates confirmed that stacking ability correlates with anti-TSE activity among cyclic tetrapyrroles.
Two Domains of Cytotoxic Necrotizing Factor Type 1 Bind the Cellular Receptor, Laminin Receptor Precursor Protein
Authors: McNichol Beth A. , Rasmussen Susan B. , Carvalho Humberto M. , Meysick Karen C. , O'Brien Alison D. 
Published: August 2007

ABSTRACTCytotoxic necrotizing factor type 1 (CNF1) and CNF2 are highly homologous toxins that are produced by certain pathogenic strains ofEscherichia coli. These 1,014-amino-acid toxins catalyze the deamidation of a specific glutamine residue in RhoA, Rac1, and Cdc42 and consist of a putative N-terminal binding domain, a transmembrane region, and a C-terminal catalytic domain. To define the regions of CNF1 that are responsible for binding of the toxin to its cellular receptor, the laminin receptor precursor protein (LRP), a series of CNF1 truncated toxins were characterized and assessed for toxin binding. In particular, three truncated toxins, ΔN63, ΔN545, and ΔC469, retained conformational integrity and in vitro enzymatic activity and were immunologically reactive against a panel of anti-CNF1 monoclonal antibodies (MAbs). Based on a comparison of these truncated toxins with wild-type CNF1 and CNF2 in LRP and HEp-2 cell binding assays and in MAb and LRP competitive binding inhibition assays and based on the results of confocal microscopy, we concluded that CNF1 contains two major binding regions: one located within the N terminus, which contained amino acids 135 to 164, and one which resided in the C terminus and included amino acids 683 to 730. The data further indicate that CNF1 can bind to an additional receptor(s) on HEp-2 cells and that LRP can also serve as a cellular receptor for CNF2.
Expression of
Helicobacter pylori
Virulence Factors and Associated Expression Profiles of Inflammatory Genes in the Human Gastric Mucosa
Authors: Wen Sicheng , Velin Dominique , Felley Christian P. , Du Likun , Michetti Pierre , Pan-Hammarström Qiang 
Published: August 2007

ABSTRACT

Helicobacter pylori
virulence factors have been suggested to be important in determining the outcome of infection. The
H. pylori
adhesion protein BabA2 is thought to play a crucial role in bacterial colonization and in induction of severe gastric inflammation, particularly in combination with expression of CagA and VacA. However, the influence of these virulence factors on the pathogenesis of
H. pylori
infection is still poorly understood. To address this question, the inflammatory gene expression profiles for two groups of patients infected with triple-negative strains (lacking expression of
cagA
,
babA2
, and
vacAs1
but expressing
vacAs2
) and triple-positive strains (expressing
cagA
,
vacAs1
, and
babA2
but lacking expression of
vacAs2
) were investigated. The gene expression patterns in the antrum gastric mucosa from patients infected with different
H. pylori
strains were very similar, and no differentially expressed genes could be identified by pairwise comparisons. Our data thus suggest that there is a lack of correlation between the host inflammatory responses in the gastric mucosa and expression of the
babA2
,
cagA
, and
vacAs1
genes.
Brucella abortusRequires the Heme Transporter BhuA for Maintenance of Chronic Infection in BALB/c Mice
Authors: Paulley James T. , Anderson Eric S. , Roop R. Martin 
Published: August 2007

ABSTRACTThe gene annotated BAB2_1150 in theBrucella abortus2308 genome sequence is predicted to encode a homolog of the well-characterized heme transporter ShuA ofShigella dysenteriaeand accordingly has been given the designationbhuA(Brucellahemeutilization). Phenotypic analysis of an isogenicbhuAmutant derived fromB. abortus2308 verified that there is a link between BhuA and the ability of the parent strain to use heme as an iron source in in vitro assays. Maximum expression ofbhuAinB. abortus2308 is observed during stationary phase when this strain in cultivated in low-iron minimal medium, and a comparison of the growth characteristics of theB. abortus bhuAmutant and 2308 in this medium suggested that heme serves as an important iron source for the parent strain during stationary phase. TheB. abortus bhuAmutant HR1703 exhibits significant attenuation in cultured murine macrophages compared to strain 2308, and unlike its parent strain, theB. abortus bhuAmutant is unable to maintain a chronic spleen infection in experimentally infected BALB/c mice. These experimental findings suggest that heme and/or heme-containing proteins represent important iron sources forB. abortus2308 during its residence in the mammalian host and that BhuA is required for efficient utilization of these iron sources.
In Vitro and In Vivo Characterization of Anthrax Anti-Protective Antigen and Anti-Lethal Factor Monoclonal Antibodies after Passive Transfer in a Mouse Lethal Toxin Challenge Model To Define Correlates of Immunity
Authors: Staats Herman F. , Alam S. Munir , Scearce Richard M. , Kirwan Shaun M. , Zhang Julia Xianzhi , Gwinn William M. , Haynes Barton F. 
Published: August 2007

ABSTRACTPassive transfer of antibody may be useful for preexposure prophylaxis against biological agents used as weapons of terror, such asBacillus anthracis. Studies were performed to evaluate the ability of anthrax antiprotective antigen (anti-PA) and antilethal factor (anti-LF) neutralizing monoclonal antibodies (mAbs) to protect against an anthrax lethal toxin (LeTx) challenge in a mouse model and to identify correlates of immunity to LeTx challenge. Despite having similar affinities for their respective antigens, anti-PA (3F11) and anti-LF (9A11), passive transfer of up to 1.5 mg of anti-PA 3F11 mAb did not provide significant protection when transferred to mice 24 h before LeTx challenge, while passive transfer of as low as 0.375 mg of anti-LF 9A11 did provide significant protection. Serum collected 24 h after passive transfer had LeTx-neutralizing activity when tested using a standard LeTx neutralization assay, but neutralization titers measured using this assay did not correlate with protection against LeTx challenge. However, measurement of LeTx-neutralizing serum responses with an LeTx neutralization assay in vitro employing the addition of LeTx to J774A.1 cells 15 min before the addition of the serum did result in neutralization titers that correlated with protection against LeTx challenge. Our results demonstrate that only the LeTx neutralization titers measured utilizing the addition of LeTx to J774A.1 cells 15 min before the addition of sample correlated with protection in vivo. Thus, this LeTx neutralization assay may be a more biologically relevant neutralization assay to predict the in vivo protective capacity of LeTx-neutralizing antibodies.
Contribution of thestgFimbrial Operon ofSalmonella entericaSerovar Typhi during Interaction with Human Cells
Authors: Forest Chantal , Faucher Sébastien P. , Poirier Katherine , Houle Sébastien , Dozois Charles M. , Daigle France 
Published: August 2007

ABSTRACTSalmonellaserovars contain a wide variety of putative fimbrial systems that may contribute to colonization of specific niches.Salmonella entericaserovar Typhi is the etiologic agent of typhoid fever and is a pathogen specific to humans. In a previous study, we identified a gene, STY3920 (stgC), encoding the predicted usher of thestgfimbrial operon, that was expressed by serovar Typhi during infection of human macrophages. Thestggenes are located in theglmS-pstSintergenic region in serovar Typhi and certainEscherichia colistrains, but they are absent in otherS. entericaserovars. We cloned thestgfimbrial operon into a nonfimbriateE. coliK-12 strain and intoS. entericaserovar Typhimurium. We demonstrated that thestgfimbrial operon contributed to increased adherence to human epithelial cells. Transcriptional fusion assays with serovar Typhi suggested thatstgis preferentially expressed in minimal medium. Deletion ofstgreduced adherence of serovar Typhi to epithelial cells. However, deletion ofstgincreased uptake of serovar Typhi by human macrophages, and overexpression ofstgin serovar Typhi and serovar Typhimurium strains reduced phagocytosis by human macrophages. These strains survived inside macrophages as well as the wild-type parent. Although thestgCgene contains a premature stop codon that disrupts the expected open reading frame encoding the usher and is therefore considered a pseudogene, our results show that thestgoperon may encode a functional fimbria. Thus, this serovar Typhi-specific fimbrial operon contributes to interactions with host cells, and further characterization is important for understanding the role of thestgfimbrial cluster in typhoid fever pathogenesis.
Identification and Isolation of
Brucella suis
Virulence Genes Involved in Resistance to the Human Innate Immune System
Authors: Liautard Janny , Ouahrani-Bettache Safia , Jubier-Maurin Véronique , Lafont Virginie , Köhler Stephan , Liautard Jean-Pierre 
Published: August 2007

ABSTRACT

Brucella
strains are facultative intracellular pathogens that induce chronic diseases in humans and animals. This observation implies that
Brucella
subverts innate and specific immune responses of the host to develop its full virulence. Deciphering the genes involved in the subversion of the immune system is of primary importance for understanding the virulence of the bacteria, for understanding the pathogenic consequences of infection, and for designing an efficient vaccine. We have developed an in vitro system involving human macrophages infected by
Brucella suis
and activated syngeneic γ9δ2 T lymphocytes. Under these conditions, multiplication of
B. suis
inside macrophages is only slightly reduced. To identify the genes responsible for this reduced sensitivity, we screened a library of 2,000 clones of transposon-mutated
B. suis
. For rapid and quantitative analysis of the multiplication of the bacteria, we describe a simple method based on Alamar blue reduction, which is compatible with screening a large library. By comparing multiplication inside macrophages alone and multiplication inside macrophages with activated γ9δ2 T cells, we identified four genes of
B. suis
that were necessary to resist to the action of the γ9δ2 T cells. The putative functions of these genes are discussed in order to propose possible explanations for understanding their exact role in the subversion of innate immunity.
Chicken Cecum Immune Response toSalmonella entericaSerovars of Different Levels of Invasiveness
Authors: Berndt Angela , Wilhelm Anne , Jugert Christiane , Pieper Jana , Sachse Konrad , Methner Ulrich 
Published: August 2007

ABSTRACTDay-old chicks are very susceptible to infections withSalmonella entericasubspecies. The gut mucosa is the initial site of host invasion and provides the first line of defense against the bacteria. To study the potential of differentS. entericaserovars to invade the gut mucosa and trigger an immune response, day-old chicks were infected orally withSalmonella entericaserovar Enteritidis,S. entericaserovar Typhimurium,S. entericaserovar Hadar, orS. entericaserovar Infantis, respectively. The localization ofSalmonellaorganisms in gut mucosa and the number of immune cells in cecum were determined by immunohistochemistry in the period between 4 h and 9 days after infection. Using quantitative real-time reverse transcription (RT)-PCR, mRNA expression of various cytokines, chemokines, and inducible nitric oxide synthase (iNOS) was examined in cecum. As a result, allS. entericaserovars were able to infect epithelial cells and the lamina propria. Notably, serovar Enteritidis showed the highest invasiveness of lamina propria tissue, whereas serovars Typhimurium and Hadar displayed moderate invasiveness and serovar Infantis hardly any invasion capabilities. Only a limited number of bacteria of all serovars were found within intestinal macrophages. Elevated numbers of granulocytes, CD8+cells, and TCR1+cells and mRNA expression rates for interleukin 12 (IL-12), IL-18, tumor necrosis factor alpha factor, and iNOS in cecum correlated well with the invasiveness of serovars in the lamina propria. In contrast, changes in numbers of TCR2+and CD4+cells and IL-2 mRNA expression seemed to be more dependent on infection of epithelial cells. The data indicate that the capability ofSalmonellaserovars to enter the cecal mucosa and invade lower regions affects both the level and character of the immune response in tissue.
l-Fucose Stimulates Utilization ofd-Ribose byEscherichia coliMG1655 ΔfucAOandE. coliNissle 1917 ΔfucAOMutants in the Mouse Intestine and in M9 Minimal Medium
Authors: Autieri Steven M. , Lins Jeremy J. , Leatham Mary P. , Laux David C. , Conway Tyrrell , Cohen Paul S. 
Published: August 2007

ABSTRACTEscherichia coliMG1655 uses several sugars for growth in the mouse intestine. To determine the roles ofl-fucose andd-ribose, anE. coliMG1655 ΔfucAOmutant and anE. coliMG1655 ΔrbsKmutant were fed separately to mice along with wild-typeE. coliMG1655. TheE. coliMG1655 ΔfucAOmutant colonized the intestine at a level 2 orders of magnitude lower than that of the wild type, but theE. coliMG1655 ΔrbsKmutant and the wild type colonized at nearly identical levels. Surprisingly, anE. coliMG1655 ΔfucAOΔrbsKmutant was eliminated from the intestine by either wild-typeE. coliMG1655 orE. coliMG1655 ΔfucAO, suggesting that the ΔfucAOmutant switches to ribose in vivo. Indeed, in vitro growth experiments showed thatl-fucose stimulated utilization ofd-ribose by theE. coliMG1655 ΔfucAOmutant but not by anE. coliMG1655 ΔfucKmutant. Since the ΔfucKmutant cannot convertl-fuculose tol-fuculose-1-phosphate, whereas the ΔfucAOmutant accumulatesl-fuculose-1-phosphate, the data suggest thatl-fuculose-1-phosphate stimulates growth on ribose both in the intestine and in vitro. AnE. coliNissle 1917 ΔfucAOmutant, derived from a human probiotic commensal strain, acted in a manner identical to that ofE. coliMG1655 ΔfucAOin vivo and in vitro. Furthermore,l-fucose at a concentration too low to support growth stimulated the utilization of ribose by the wild-typeE. colistrains in vitro. Collectively, the data suggest thatl-fuculose-1-phosphate plays a role in the regulation of ribose usage as a carbon source byE. coliMG1655 andE. coliNissle 1917 in the mouse intestine.
Coxiella burnetiiInhibits Activation of Host Cell Apoptosis through a Mechanism That Involves Preventing CytochromecRelease from Mitochondria
Authors: Lührmann Anja , Roy Craig R. 
Published: August 2007

ABSTRACTCoxiella burnetiiis an obligate intracellular pathogen and the etiological agent of the human disease Q fever.C. burnetiiinfects mammalian cells and then remodels the membrane-bound compartment in which it resides into a unique lysosome-derived organelle that supports bacterial multiplication. To gain insight into the mechanisms by whichC. burnetiiis able to multiply intracellularly, we examined the ability of host cells to respond to signals that normally induce apoptosis. Our data show that mammalian cells infected withC. burnetiiare resistant to apoptosis induced by staurosporine and UV light.C. burnetiiinfection prevented caspase 3/7 activation and limited fragmentation of the host cell nucleus in response to agonists that induce apoptosis. Inhibition of bacterial protein synthesis reduced the antiapoptotic effect thatC. burnetiiexerted on infected host cells. Inhibition of apoptosis inC. burnetii-infected cells did not correlate with the degradation of proapoptotic BH3-only proteins involved in activation of the intrinsic cell death pathway; however, cytochromecrelease from mitochondria was diminished in cells infected withC. burnetiiupon induction of apoptosis. These data indicate thatC. burnetiican interfere with the intrinsic cell death pathway during infection by producing proteins that either directly or indirectly prevent release of cytochromecfrom mitochondria. It is likely that inhibition of apoptosis byC. burnetiirepresents an important virulence property that allows this obligate intracellular pathogen to maintain host cell viability despite inducing stress that would normally activate the intrinsic death pathway.