bluuebunny/crossref_metadata_2025_split huggingface dataset:
Global Effects of Virulence Gene Regulators in aBacillus anthracisStrain with Both Virulence Plasmids
Authors: Bourgogne Agathe , Drysdale Melissa , Hilsenbeck Susan G. , Peterson Scott N. , Koehler Theresa M. 
Published: April 2003

ABSTRACTControl of anthrax toxin and capsule synthesis, the two major virulence factors ofBacillus anthracis, has been associated with two regulatory genes,atxAandacpA, located on virulence plasmids pXO1 and pXO2, respectively. We used transcriptional profiling to determine whetheratxAand/oracpAcontrol genes other than those already described and to investigate functional similarities of the regulators. Transcription was assessed in a pXO1+pXO2+parent strain and in isogenic mutants in which one or both regulatory genes were deleted. We determined that in addition to the toxin and capsule genes,atxAcontrols expression of numerous other genes on both plasmids and the chromosome. Generally, plasmid-encoded genes were more highly regulated than chromosomal genes, and both positive and negative effects were observed. CertainatxA-regulated genes were affected synergistically in anatxA acpAmutant. Yet overall,acpAappears to be a minor regulator with fewer targets thanatxA. In contrast to previous reports ofacpAfunction in attenuated strains,acpAhad a minimal influence on capsule gene transcription and capsule synthesis in a genetically complete strain. Surprisingly,acpAexpression was positively affected byatxA,althoughatxA-activated capsule gene transcription is notacpAdependent. The newly discoveredatxA-regulated targets include genes predicted to encode secreted proteins and proteins with roles in transcriptional regulation and signaling. Regulation of chromosomal genes byatxAis particularly intriguing, given that many of the target genes have homologues in otherBacillusspecies that lackatxAhomologues. Given the global effect ofatxAon gene expression inB. anthracis, previous assumptions regarding reduced virulence of strains harboring single plasmids must be reassessed and the potential roles of newly identifiedatxA-regulated genes should be investigated.
Inactivation of thesrtAGene Affects Localization of Surface Proteins and Decreases Adhesion ofStreptococcus pneumoniaeto Human Pharyngeal Cells In Vitro
Authors: Kharat Arun S. , Tomasz Alexander 
Published: April 2003

ABSTRACTInactivation of sortase genesrtAinStreptococcus pneumoniaestrain R6 caused the release of β-galactosidase and neuraminidase A (NanA) from the cell wall into the surrounding medium. Both of these surface proteins contain the LPXTG motif in the C-terminal domain. Complementation with plasmid-bornesrtAreversed protein release. Deletion ofmurM, a gene involved in the branching of pneumococcal peptidoglycan, also caused partial release of β-galactosidase, suggesting preferential attachment of the protein to branched muropeptides in the cell wall. Inactivation ofsrtAcaused decreased adherence to human pharyngeal cells in vitro but had no effect on the virulence of a capsular type III strain ofS. pneumoniaein the mouse intraperitoneal model. The observations suggest that—as in other gram-positive bacteria—sortase-dependent display of proteins occurs inS. pneumoniaeand that some of these proteins may be involved in colonization of the human host.
Modulation of Myosin Light-Chain Phosphorylation by p21-Activated Kinase 1 in
Escherichia coli
Invasion of Human Brain Microvascular Endothelial Cells
Authors: Rudrabhatla Rajyalakshmi S. , Sukumaran Sunil K. , Bokoch Gary M. , Prasadarao Nemani V. 
Published: April 2003

ABSTRACT

Cytoskeletal dynamics, modulated by actin-myosin interactions, play an important role in
Escherichia coli
K1 invasion of human brain microvascular endothelial cells (HBMEC). Herein, we show that inhibitors of myosin function, butanedione monoxide and ML-7, significantly blocked the
E. coli
invasion of HBMEC. The invasive
E. coli
induces myosin light-chain (MLC) phosphorylation during the invasion process, which gets recruited to the site of actin condensation beneath the bacteria. We also show that invading
E. coli
downregulates the activity of p21-activated kinase 1 (PAK1), which is an upstream regulator of MLC kinase (MLCK). Overexpression of wild-type PAK1 and constitutively active PAK1 in HBMEC inhibits
E. coli
invasion significantly with a concomitant decrease in MLC phosphorylation. The inhibition of
E. coli
invasion by these PAK1 mutants is due to the absence of phospho-MLC at the actin condensation points. In contrast, the dominant-negative PAK1 shows no effect either on the invasion or on MLC phosphorylation or phospho-MLC recruitment to the actin focal points, suggesting that activated PAK1 inactivates MLCK. Taken together, these results suggest that
E. coli
invasion of HBMEC induces MLC phosphorylation by inhibiting the activity of PAK1 and the recruitment of phosphorylated MLC to the site of actin condensation beneath the bacteria for efficient internalization of
E. coli
into HBMEC.
Deletion of the
Aspergillus fumigatus
Gene Encoding the Ras-Related Protein RhbA Reduces Virulence in a Model of Invasive Pulmonary Aspergillosis
Authors: Panepinto John C. , Oliver Brian G. , Fortwendel Jarrod R. , Smith Darcey L. H. , Askew David S. , Rhodes Judith C. 
Published: April 2003

ABSTRACT

Aspergillus fumigatus
is the predominant mold pathogen in patients who lack functional innate immunity. The
A. fumigatus rhbA
gene was first identified as a transcript that was upregulated when the organism was grown in the presence of mammalian cells. To gain insight into the function of
rhbA
in the growth and pathogenesis of
A. fumigatus
, we constructed a strain that lacks a functional
rhbA
gene. The Δ
rhbA
mutant showed a significant reduction in virulence compared to the virulence of the wild type in a mouse model of invasive aspergillosis. Complementation of the deletion with the wild-type gene restored full virulence. Although the Δ
rhbA
mutant grew as well as the wild type on solid medium containing the rich nitrogen source ammonium, the growth of the mutant was impaired on medium containing poor nitrogen sources. Like the
Saccharomyces cerevisiae rhb1
mutant, the Δ
rhbA
mutant exhibited increased uptake of arginine. In addition, the Δ
rhbA
strain underwent asexual development in submerged cultures, even under ammonium-excess conditions. Growth of the mutant with poor nitrogen sources eliminated both the arginine uptake and submerged asexual development phenotypes. The mutant showed enhanced sensitivity to the TOR kinase inhibitor rapamycin. These findings establish the importance of
rhbA
for
A. fumigatus
virulence and suggest a role for
rhbA
in nutrient sensing.
Pretreatment of Mice with Streptomycin Provides aSalmonella entericaSerovar Typhimurium Colitis Model That Allows Analysis of Both Pathogen and Host
Authors: Barthel Manja , Hapfelmeier Siegfried , Quintanilla-Martínez Leticia , Kremer Marcus , Rohde Manfred , Hogardt Michael , Pfeffer Klaus , Rüssmann Holger , Hardt Wolf-Dietrich 
Published: April 2003

ABSTRACTSalmonella entericasubspecies 1 serovar Typhimurium is a principal cause of human enterocolitis. For unknown reasons, in mice serovar Typhimurium does not provoke intestinal inflammation but rather targets the gut-associated lymphatic tissues and causes a systemic typhoid-like infection. The lack of a suitable murine model has limited the analysis of the pathogenetic mechanisms of intestinal salmonellosis. We describe here how streptomycin-pretreated mice provide a mouse model for serovar Typhimurium colitis. Serovar Typhimurium colitis in streptomycin-pretreated mice resembles many aspects of the human infection, including epithelial ulceration, edema, induction of intercellular adhesion molecule 1, and massive infiltration of PMN/CD18+cells. This pathology is strongly dependent on protein translocation via the serovar Typhimurium SPI1 type III secretion system. Using a lymphotoxin β-receptor knockout mouse strain that lacks all lymph nodes and organized gut-associated lymphatic tissues, we demonstrate that Peyer's patches and mesenteric lymph nodes are dispensable for the initiation of murine serovar Typhimurium colitis. Our results demonstrate that streptomycin-pretreated mice offer a unique infection model that allows for the first time to use mutants of both the pathogen and the host to study the molecular mechanisms of enteric salmonellosis.
Activation of Transcription Factors AP-1 and NF-κB in Murine Chagasic Myocarditis
Authors: Huang Huan , Petkova Stefka B. , Cohen Alex W. , Bouzahzah Boumediene , Chan John , Zhou Jian-nian , Factor Stephen M. , Weiss Louis M. , Krishnamachary Mohan , Mukherjee Shankar , Wittner Murray , Kitsis Richard N. , Pestell Richard G. , Lisanti Michael P. , Albanese Chris , Tanowitz Herbert B. 
Published: April 2003

ABSTRACTThe myocardium of CD1 mice was examined for the activation of signal transduction pathways leading to cardiac inflammation and subsequent remodeling duringTrypanosoma cruziinfection (Brazil strain). The activity of three pathways of the mitogen-activated protein kinases (MAPKs) was determined. Immunoblotting revealed a persistent elevation of phosphorylated (activated) extracellular-signal-regulated kinase (ERK), which regulates cell proliferation. During infection there was a transient activation of p38 MAPK but no activation of Jun N-terminal kinase. Early targets of activated ERK, c-Jun and c-Fos, were elevated during infection, as demonstrated by semiquantitative reverse transcription-PCR. Immunostaining revealed that the endothelium and the interstitial cells were most intensely stained with antibodies to c-Jun and c-Fos. Soon after infection, AP-1 and NF-κB DNA binding activity was increased. Protein levels of cyclin D1, the downstream target of ERK and NF-κB, were induced during acute infection. Immunostaining demonstrated increased expression of cyclin D1 in the vascular and endocardial endothelium, inflammatory cells, and the interstitial areas. Increased expression of the cyclin D1-specific phosphorylated retinoblastoma protein (Ser780) was also evident. Immunoblotting and immunostaining also demonstrated increased expression of proliferating cellular nuclear antigen that was predominantly present in the inflammatory cells, interstitial areas (i.e., fibroblasts), and endothelium. These data demonstrate thatT. cruziinfection results in activation of the ERK-AP-1 pathway and NF-κB. Cyclin D1 expression was also increased. These observations provide a molecular basis for the activation of pathways involved in cardiac remodeling in chagasic cardiomyopathy.
Limited Role of Lipopolysaccharide Lewis Antigens in Adherence ofHelicobacter pylorito the Human Gastric Epithelium
Authors: Mahdavi Jafar , Borén Thomas , Vandenbroucke-Grauls Christina , Appelmelk Ben J. 
Published: April 2003

ABSTRACTIn vitro and in vivo studies from various groups have suggested thatHelicobacter pylorilipopolysaccharide (LPS) Lewis x (Lex) antigens mediate bacterial adhesion. We have now reevaluated this hypothesis by studying the adherence in situ ofH. pyloristrain 11637 and its corresponding Lex-negativerfbMmutant to human gastric mucosa from patients (n= 22) with various gastric pathologies. Significant binding of the parent strain was observed in only 8 out of 22 sections; in four out of eight patients, the Lex-negative mutant bound less well. One of these four patients displayed no gastric abnormalities, and the other three showed dysplasia, metaplasia, and adenocarcinoma, respectively; hence, we are unable to define the circumstances under which LPS-mediated adhesion takes place. We conclude thatH. pyloriLPS plays a distinct but minor role in adhesion.
Differential Expression of Genes That Harbor a Common Regulatory Element in
Neisseria meningitidis
upon Contact with Target Cells
Authors: Deghmane Ala-Eddine , Larribe Mireille , Giorgini Dario , Sabino Dora , Taha Muhamed-Kheir 
Published: April 2003

ABSTRACT

The expression of several genes in
Neisseria meningitidis
upon contact with epithelial cells was associated with the presence of the contact regulatory elements of
Neisseria
. These genes are involved in various aspects of meningococcal biology and could be coordinately regulated upon contact with target cells.
Influence of Lewis Antigen Expression byHelicobacter pylorion Bacterial Internalization by Gastric Epithelial Cells
Authors: Lozniewski Alain , Haristoy Xavier , Rasko David A. , Hatier Renée , Plénat François , Taylor Diane E. , Angioi-Duprez Karine 
Published: April 2003

ABSTRACTThe role ofHelicobacter pylorilipopolysaccharide (LPS) Lewis antigens in infection is still not well known. We investigated the influence of Lewis antigen expression byH. pylorion its internalization by AGS cells and the epithelium of human gastric xenografts in nude mice using isogenic mutants in LPS biosynthetic genes. In vivo, colonization rates were unaffected by the change inH. pyloriLewis antigen expression, whereas the number of viable intracellular bacteria was significantly higher with wild-typeH. pyloristrains expressing Lewis antigens when compared to the isogenic mutants in both models.H. pyloristrains expressing more Lewis X antigens (Lex) were internalized at a higher rate than those expressing less Lex, type II Lewis antigens (Leaor Leb) alone, or no Lewis antigens. Thus, Lewis antigens appear to be involved in the internalization ofH. pyloriby the gastric epithelium.
Characterization of
Staphylococcus aureus
Enterotoxin L
Authors: Orwin Paul M. , Fitzgerald J. Ross , Leung Donald Y. M. , Gutierrez Juan A. , Bohach Gregory A. , Schlievert Patrick M. 
Published: April 2003

ABSTRACT

Staphylococcus aureus
causes a wide variety of diseases. Major virulence factors of this organism include enterotoxins (SEs) that cause both food poisoning and toxic shock syndrome. Recently, a novel SE, tentatively designated SEL, was identified in a pathogenicity island from a bovine mastitis isolate. The toxin had a molecular weight of 26,000 and an isoelectric point of 8.5. Recombinant SEL shared many biological activities with SEs, including superantigenicity, pyrogenicity, enhancement of endotoxin shock, and lethality in rabbits when administered in subcutaneous miniosmotic pumps, but the protein lacked emetic activity. T cells bearing the T-cell receptor β chain variable regions 5.1, 5.2, 6.7, 16, and 22 were significantly stimulated by recombinant SEL.
The Entner-Doudoroff Pathway Has Little Effect on
Helicobacter pylori
Colonization of Mice
Authors: Wanken Amy E. , Conway Tyrrell , Eaton Kathryn A. 
Published: April 2003

ABSTRACT

Helicobacter pylori
mutants deficient in 6-phosphogluconate dehydratase (6PGD) were constructed. Colonization densities were lower and minimum infectious doses were higher for mutant strains than for wild-type strains. In spite of better colonization, however, wild-type strains did not displace the mutant in cocolonization experiments. Loss of 6PGD diminishes the fitness of
H. pylori
in vivo, but the pathway is nonessential for colonization.
Production of the Siderophore 2,3-Dihydroxybenzoic Acid Is Required for Wild-Type Growth of
Brucella abortus
in the Presence of Erythritol under Low-Iron Conditions In Vitro
Authors: Bellaire Bryan H. , Elzer Philip H. , Baldwin Cynthia L. , Roop R. Martin 
Published: April 2003

ABSTRACT

Production of the siderophore 2,3-dihyroxybenzoic acid (2,3-DHBA) is required for the wild-type virulence of
Brucella abortus
in cattle. A possible explanation for this requirement was uncovered when it was determined that a
B. abortus dhbC
mutant (BHB1) defective in 2,3-DHBA production displays marked growth restriction in comparison to its parent strain,
B. abortus
2308, when cultured in the presence of erythritol under low-iron conditions. This phenotype is not displayed when these strains are cultured under low-iron conditions in the presence of other readily utilizable carbon and energy sources. The addition of either exogenous 2,3-DHBA or FeCl
3
relieves this growth defect, suggesting that the inability of the
B. abortus dhbC
mutant to display wild-type growth in the presence of erythritol under iron-limiting conditions is due to a defect in iron acquisition. Restoring 2,3-DHBA production to the
B. abortus dhbC
mutant by genetic complementation abolished the erythritol-specific growth defect exhibited by this strain in low-iron medium, verifying the relationship between 2,3-DHBA production and efficient growth in the presence of erythritol under low-iron conditions. The positive correlation between 2,3-DHBA production and growth in the presence of erythritol was further substantiated by the observation that the addition of erythritol to low-iron cultures of
B. abortus
2308 stimulated the production of 2,3-DHBA by increasing the transcription of the
dhbCEBA
operon. Correspondingly, the level of exogenous iron needed to repress
dhbCEBA
expression in
B. abortus
2308 was also greater when this strain was cultured in the presence of erythritol than that required when it was cultured in the presence of any of the other readily utilizable carbon and energy sources tested. The tissues of the bovine reproductive tract are rich in erythritol during the latter stages of pregnancy, and the ability to metabolize erythritol is thought to be important to the virulence of
B. abortus
in pregnant ruminants. Consequently, the experimental findings presented here offer a plausible explanation for the attenuation of the
B. abortus
2,3-DHBA-deficient mutant BHB1 in pregnant ruminants.
Immune Response Induced by RecombinantMycobacterium bovisBCG Producing the Cholera Toxin B Subunit
Authors: Biet Franck , Kremer Laurent , Wolowczuk Isabelle , Delacre Myriam , Locht Camille 
Published: April 2003

ABSTRACTThe pentameric form of the cholera toxin B subunit (CTB) is known to be a strong mucosal adjuvant and stimulates antigen-specific secretory immunoglobulin A (IgA) and systemic antibody responses to antigens when given by mucosal routes. To deliver CTB for prolonged periods of time to the respiratory mucosa, we constructed aMycobacterium bovisbacillus Calmette-Guérin (BCG) strain that produces and secretes assembled pentameric CTB. Mice immunized intranasally (i.n.) with recombinant BCG (rBCG) developed a stronger anti-BCG IgA response in bronchoalveolar lavage fluids (BALF) than mice immunized with nonrecombinant BCG. The total IgA response in the BALF of mice immunized with rBCG was also stronger than that in BALF of mice immunized with the nonrecombinant strain. The induction of IgA was well correlated with an increased production of transforming growth factor β1. Simultaneous administration of intraperitoneally delivered ovalbumin and of i.n. delivered CTB-producing BCG induced a long-lasting ovalbumin-specific mucosal IgA response as well as a systemic IgG response, both of which were significantly higher than those in mice immunized with nonrecombinant BCG together with ovalbumin. These results suggest that the CTB-producing BCG may be a powerful adjuvant to be considered for future mucosal vaccine development.
Humoral Immunity Reflects Altered T Helper Cell Bias inBorrelia burgdorferi-Infected γδ T-Cell-Deficient Mice
Authors: Bockenstedt Linda K. , Shanafelt Marie-Claude , Belperron Alexia , Mao Jialing , Barthold Stephen W. 
Published: April 2003

ABSTRACTIn murine Lyme borreliosis, the absence of γδ T lymphocytes augments the T helper cell 2 type humoral response but does not alter disease susceptibility. Arthropod transmission ofBorrelia burgdorferispirochetes results in similar antibody isotypes when γδ T cells are present, suggesting that vector effects can negate γδ T-cell functions in vivo.
Expression of H
C
Subunits from
Clostridium botulinum
Types C and D and Their Evaluation as Candidate Vaccine Antigens in Mice
Authors: Woodward L. A. , Arimitsu H. , Hirst R. , Oguma K. 
Published: April 2003

ABSTRACT

Two proteins representing the heavy-chain subunits of botulinum neurotoxin types C and D were expressed in
Escherichia coli
, and their vaccine potential was evaluated. Mice were vaccinated with doses ranging from 0.5 to 10 μg and were challenged with 10 to 10
5
50% lethal doses of toxin. For the type C subunit protein, C50, two doses of 2 μg were required for full protection, while, for type D subunit protein, D50, two 1-μg doses were required. A bivalent vaccine consisting of a mixture of these two proteins also provided protection against both botulinum neurotoxin type C and type D challenge. Antibody levels in serum were determined by both enzyme-linked immunosorbent assays and serum neutralization assays
Coordinated Expression of Tracheal Antimicrobial Peptide and Inflammatory-Response Elements in the Lungs of Neonatal Calves with Acute Bacterial Pneumonia
Authors: Caverly Jessica M. , Diamond Gill , Gallup Jack M. , Brogden Kim A. , Dixon Richard A. , Ackermann Mark R. 
Published: April 2003

ABSTRACTLung tissue removed from neonatal calves with acuteMannheimia haemolyticapneumonia showed that rapid up-regulation of the basal mRNA expression of tracheal antimicrobial peptide (TAP), NF-κB, and intercellular adhesion molecule 1 occurred after infection; TAP and interleukin 8 expression were highly correlated. This work suggests that the coordinated expression of β-defensin and inflammatory elements occurs during bacterial pneumonia.
Pneumococcal Serotype 19F Conjugate Vaccine Induces Cross-Protective Immunity to Serotype 19A in a Murine Pneumococcal Pneumonia Model
Authors: Jakobsen Håvard , Sigurdsson Viktor D. , Sigurdardottir Sigurveig , Schulz Dominique , Jonsdottir Ingileif 
Published: April 2003

ABSTRACT
Immunization with a pneumococcal conjugate vaccine (PNC) containing serotype 19F induces cross-reactive antibodies to 19A in mice and human infants. Active immunization with PNC and passive immunization with serum samples from infants vaccinated with PNC containing serotype 19F, but not serotype 19A, protected against lung infection caused by both serotypes in a murine model.
Immunization with Genetic Toxoids of theArcanobacterium pyogenesCholesterol-Dependent Cytolysin, Pyolysin, Protects Mice against Infection
Authors: Jost B. Helen , Trinh Hien T. , Songer J. Glenn , Billington Stephen J. 
Published: April 2003

ABSTRACTPyolysin (PLO), a cholesterol-dependent cytolysin expressed byArcanobacterium pyogenes, is an important host-protective antigen. However, this molecule is toxic and requires inactivation prior to its use as a vaccine. Three genetically toxoided, nonhemolytic PLO molecules, HIS-PLO.F497, HIS-PLO.ΔP499, and HIS-PLO.A522, were found to be nontoxic, and vaccinated mice were protected from infection, indicating the potential of these toxoids as vaccines. Furthermore, in a mouse model of infection,A. pyogenescarrying the F497mutation was as attenuated as a PLO-deficient strain, indicating that the cytolytic activity of PLO is important in virulence.
Structural and Functional Cellular Changes Induced by
Burkholderia pseudomallei
Rhamnolipid
Authors: Häuβler S. , Rohde M. , von Neuhoff N. , Nimtz M. , Steinmetz I. 
Published: April 2003

ABSTRACT

In this study we report that extracellular
Burkholderia pseudomallei
rhamnolipid induced cytopathic changes characterized by retraction, rounding up, and, finally, detachment in phagocytic and nonphagocytic cell lines. These changes were due to a progressive reorganization of the F-actin network resulting in impaired cell cycle progression and a reduced phagocytic function of macrophages.