bluuebunny/crossref_metadata_2025_split huggingface dataset:
Involvement of Fractalkine/CX3CL1 Expression by Dendritic Cells in the Enhancement of Host Immunity against
Legionella pneumophila
Authors: Kikuchi Toshiaki , Andarini Sita , Xin Hong , Gomi Kazunori , Tokue Yutaka , Saijo Yasuo , Honjo Tasuku , Watanabe Akira , Nukiwa Toshihiro 
Published: August 2005

ABSTRACT

Legionnaires' disease is clinically manifested as severe pneumonia caused by
Legionella pneumophila
. However, the dendritic cell (DC)-centered immunological framework of the host defense against
L. pneumophila
has not been fully delineated. For this study, we focused on a potent chemoattractant for lymphocytes, fractalkine/CX3CL1, and observed that the fractalkine expression of DCs was somewhat up-regulated when they encountered
L. pneumophila
. We therefore hypothesized that fractalkine expressed by
Legionella
-capturing DCs is involved in the induction of T-cell-mediated immune responses against
Legionella
, which would be enhanced by a genetic modulation of DCs to overexpress fractalkine. In vivo immunization-challenge experiments demonstrated that DCs modified with a recombinant adenovirus vector to overexpress fractalkine (AdFKN) and pulsed with heat-killed
Legionella
protected immunized mice from a lethal
Legionella
infection and that the generation of in vivo protective immunity depended on the host lymphocyte subsets, including CD4
+
T cells, CD8
+
T cells, and B cells. Consistent with this, immunization with AdFKN/
Legionella
/DC induced significantly higher levels of serum anti-
Legionella
antibodies of several isotypes than those induced by control immunizations. Further analysis of spleen cells from the immunized mice indicated that the AdFKN/
Legionella
/DC immunization elicited Th1-dominated immune responses to
L. pneumophila
. These observations suggest that fractalkine may play an important role in the DC-mediated host defense against intracellular pathogens such as
L. pneumophila
.
Porphyromonas gingivalisFimbria-Dependent Activation of Inflammatory Genes in Human Aortic Endothelial Cells
Authors: Chou Hsin-Hua , Yumoto Hiromichi , Davey Michael , Takahashi Yusuke , Miyamoto Takanari , Gibson Frank C. , Genco Caroline A. 
Published: August 2005

ABSTRACTEpidemiological and pathological studies have suggested that infection with the oral pathogenPorphyromonas gingivaliscan potentiate atherosclerosis and human coronary heart disease. Furthermore, infection with invasive, but not noninvasiveP. gingivalishas been demonstrated to accelerate atherosclerosis in apolipoprotein E-deficient (ApoE−/−) mice and to accelerate local inflammatory responses in aortic tissue. In the present study, using high-density oligonucleotide microarrays, we have defined the gene expression profile of human aortic endothelial cells (HAEC) after infection with invasive and noninvasiveP. gingivalis. After infection of HAEC with invasiveP. gingivalisstrain 381, we observed the upregulation of 68 genes. Genes coding for the cytokines Gro2 and Gro3; the adhesion molecules intercellular adhesion molecule 1 (ICAM-1), vascular cell adhesion molecule (VCAM)-1, and ELAM-1 (E-selectin); the chemokine interleukin-8 (IL-8); and the proinflammatory molecules IL-6 and cyclooxygenase-2 were among the most highly upregulated genes inP. gingivalis381-infected HAEC compared to uninfected HAEC control. Increased mRNA levels for signaling molecules, transcriptional regulators, and cell surface receptors were also observed. Of note, only 4 of these 68 genes were also upregulated in HAEC infected with the noninvasiveP. gingivalis fimAmutant. Reverse transcription-PCR, enzyme-linked immunosorbent assay, and fluorescence-activated cell sorting analysis confirmed the expression of ICAM-1, VCAM-1, E-/P-selectins, IL-6, and IL-8 in HAEC infected with invasiveP. gingivalis. We also demonstrated that increased expression of ICAM-1 and VCAM-1 in aortic tissue of ApoE−/−mice orally challenged with invasiveP. gingivalisbut not with the noninvasiveP. gingivalis fimAmutant by immunohistochemical analysis. Taken together, these results demonstrate thatP. gingivalisfimbria-mediated invasion upregulates inflammatory gene expression in HAEC and in aortic tissue and indicates that invasiveP. gingivalisinfection accelerates inflammatory responses directly in the aorta.
Cable Pili and the 22-Kilodalton Adhesin Are Required for
Burkholderia cenocepacia
Binding to and Transmigration across the Squamous Epithelium
Authors: Urban Teresa A. , Goldberg Joanna B. , Forstner Janet F. , Sajjan Umadevi S. 
Published: August 2005

ABSTRACT

Burkholderia cenocepacia
strains expressing both cable (Cbl) pili and the 22-kDa adhesin bind to cytokeratin 13 (CK13) strongly and invade squamous epithelium efficiently. It has not been established, however, whether the gene encoding the adhesin is located in the
cbl
operon or what specific contribution the adhesin and Cbl pili lend to binding and transmigration or invasion capacity of
B. cenocepacia
. By immunoscreening an expression library of
B. cenocepacia
isolate BC7, we identified a large gene (
adhA
) that encodes the 22-kDa adhesin. Isogenic mutants lacking expression of either Cbl pili (
cblA
or
cblS
mutants) or the adhesin (
adhA
mutant) were constructed to assess the individual role of Cbl pili and the adhesin in mediating
B. cenocepacia
binding to and transmigration across squamous epithelium. Relative to the parent strain, mutants of Cbl pili showed reduced binding (50%) to isolated CK13, while the adhesin mutant showed almost no binding (0 to 8%). Mutants lacking either cable pili or the adhesin were compromised in their ability to bind to and transmigrate across the squamous epithelium compared to the wild-type strain, although this deficiency was most pronounced in the
adhA
mutant. These results indicate that both Cbl pili and the 22-kDa adhesin are necessary for the optimal binding to CK13 and transmigration properties of
B. cenocepacia
.
Iron Acquisition from Transferrin by
Candida albicans
Depends on the Reductive Pathway
Authors: Knight Simon A. B. , Vilaire Gaston , Lesuisse Emmanuel , Dancis Andrew 
Published: August 2005

ABSTRACT

Host-pathogen interactions that alter virulence are influenced by critical nutrients such as iron. In humans, free iron is unavailable, being present only in high-affinity iron binding proteins such as transferrin. The fungal pathogen
Candida albicans
grows as a saprophyte on mucosal surfaces. Occasionally it invades systemically, and in this circumstance it will encounter transferrin iron. Here we report that
C. albicans
is able to acquire iron from transferrin. Iron-loaded transferrin restored growth to cultures arrested by iron deprivation, whereas apotransferrin was unable to promote growth. By using congenic strains, we have been able to show that iron uptake by
C. albicans
from transferrin was mediated by the reductive pathway (via
FTR1
). The genetically separate siderophore and heme uptake systems were not involved.
FRE10
was required for a surface reductase activity and for efficient transferrin iron uptake activity in unbuffered medium. Other reductase genes were apparently up-regulated in medium buffered at pH 6.3 to 6.4, and the
fre10
−/−
mutant had no effect under these conditions. Experiments in which transferrin was sequestered in a dialysis bag demonstrated that cell contact with the substrate was required for iron reduction and release. The requirement of
FTR1
for virulence in a systemic infection model and its role in transferrin iron uptake raise the possibility that transferrin is a source of iron during systemic
C. albicans
infections.
The
Aspergillus fumigatus
Siderophore Biosynthetic Gene
sidA
, Encoding
l
-Ornithine
N
5
-Oxygenase, Is Required for Virulence
Authors: Hissen Anna H. T. , Wan Adrian N. C. , Warwas Mark L. , Pinto Linda J. , Moore Margo M. 
Published: August 2005

ABSTRACT

Aspergillus fumigatus
is the leading cause of invasive mold infection and is a serious problem in immunocompromised populations worldwide. We have previously shown that survival of
A. fumigatus
in serum may be related to secretion of siderophores. In this study, we identified and characterized the
sidA
gene of
A. fumigatus
, which encodes
l
-ornithine
N
5
-oxygenase, the first committed step in hydroxamate siderophore biosynthesis.
A. fumigatus sidA
codes for a protein of 501 amino acids with significant homology to other fungal
l
-ornithine
N
5
-oxygenases. A stable Δ
sidA
strain was created by deletion of
A. fumigatus sidA
. This strain was unable to synthesize the siderophores
N
′,
N
",
N
‴-triacetylfusarinine C (TAF) and ferricrocin. Growth of the Δ
sidA
strain was the same as that of the wild type in rich media; however, the Δ
sidA
strain was unable to grow in low-iron defined media or media containing 10% human serum unless supplemented with TAF or ferricrocin. No significant differences in ferric reduction activities were observed between the parental strain and the Δ
sidA
strain, indicating that blocking siderophore secretion did not result in upregulation of this pathway. Unlike the parental strain, the Δ
sidA
strain was unable to remove iron from human transferrin. A rescued strain (Δ
sidA + sidA
) was constructed; it produced siderophores and had the same growth as the wild type on iron-limited media. Unlike the wild-type and rescued strains, the Δ
sidA
strain was avirulent in a mouse model of invasive aspergillosis, indicating that
sidA
is necessary for
A. fumigatus
virulence.
Mannheimia haemolytica
Leukotoxin Induces Apoptosis of Bovine Lymphoblastoid Cells (BL-3) via a Caspase-9-Dependent Mitochondrial Pathway
Authors: Atapattu Dhammika N. , Czuprynski Charles J. 
Published: August 2005

ABSTRACT

Mannheimia haemolytica
is a key pathogen in the bovine respiratory disease complex. It produces a leukotoxin (LKT) that is an important virulence factor, causing cell death in bovine leukocytes. The LKT binds to the β
2
integrin CD11a/CD18, which usually activates signaling pathways that facilitate cell survival. In this study, we investigated mechanisms by which LKT induces death in bovine lymphoblastoid cells (BL-3). Incubation of BL-3 cells with a low concentration of LKT results in the activation of caspase-3 and caspase-9 but not caspase-8. Similarly, the proapoptotic proteins Bax and BAD were significantly elevated, while the antiapoptotic proteins Bcl-2, Bcl
XL
and Akt-1 were downregulated. Following exposure to LKT, we also observed a reduction in mitochondrial cytochrome
c
and corresponding elevation of cytosolic cytochrome
c
, suggesting translocation from the mitochondrial compartment to the cytosol. Consistent with this observation, tetramethylrhodamine ethyl ester perchlorate staining revealed that mitochondrial membrane potential was significantly reduced. These data suggest that LKT induces apoptosis of BL-3 cells via a caspase-9-dependent mitochondrial pathway. Furthermore, scanning electron micrographs of mitochondria from LKT-treated BL-3 cells revealed lesions in the outer mitochondrial membrane, which are larger than previous reports of the permeability transition pore through which cytochrome
c
is usually released.
Role of FliF and FliI of
Listeria monocytogenes
in Flagellar Assembly and Pathogenicity
Authors: Bigot Armelle , Pagniez Hélène , Botton Eléonore , Fréhel Claude , Dubail Iharilalao , Jacquet Christine , Charbit Alain , Raynaud Catherine 
Published: August 2005

ABSTRACT

Flagellar structures have been shown to participate in virulence in a variety of intestinal pathogens. Here, we have identified two potential flagellar genes of
Listeria monocytogenes
: lmo0713, encoding a protein similar to the flagellar basal body component FliF, and lmo0716, encoding a protein similar to FliI, the cognate ATPase energizing the flagellar export apparatus. Expression of
fliF
and
fliI
appears to be downregulated at 37°C, like that of
flaA
, encoding flagellin. By constructing two chromosomal deletion mutants, we show that inactivation of either
fliF
or
fliI
(i) abolishes bacterial motility and flagella production, (ii) impairs adhesion and entry into nonphagocytic epithelial cells, and (iii) also reduces uptake by bone marrow-derived macrophages. However, the Δ
fliF
and Δ
fliI
mutations have only a minor impact on bacterial virulence in the mouse model, indicating that the flagellar secretion apparatus itself is not essential for survival in this animal model. Finally, among 100 human clinical isolates of
L. monocytogenes
tested, we found 20 strains still motile at 37°C. Notably, all these strains adhered less efficiently than strain EGD-e to Caco-2 cells at 37°C but showed no defect of intracellular multiplication. These data suggest that expression of the flagella at 37°C might hinder optimal adhesion to epithelial cells but has no impact on intracytosolic survival of
L. monocytogenes
.
Characterization of Novel Staphylococcal Enterotoxin-Like Toxin Type P
Authors: Omoe Katsuhiko , Imanishi Ken'ichi , Hu Dong-Liang , Kato Hidehito , Fugane Yoshitaku , Abe Yohei , Hamaoka Shoji , Watanabe Yutaka , Nakane Akio , Uchiyama Takehiko , Shinagawa Kunihiro 
Published: August 2005

ABSTRACTWe investigated the biological properties of a novel staphylococcal enterotoxin (SE)-like toxin type P (SElP). SElP induced a substantial proliferative response and the production of cytokines interleukin-2, gamma interferon, tumor necrosis factor alpha, and interleukin-4 from human T cells when administered at a concentration of 0.4 pM (0.01 ng/ml) or more. The expression of major histocompatibility complex class II molecules on accessory cells was required for T-cell stimulation by SElP. SElP selectively stimulated a vast number of human T cells bearing receptors Vβ 5.1, 6, 8, 16, 18, and 21.3. These results indicated that SElP acts as a superantigen. SElP proved to be emetic in the house musk shrew emetic assay, although at a relatively high dose (50 to 150 μg/animal). A quantitative assay of SElP production with 30Staphylococcus aureusstrains harboringselpshowed that 60% of these strains produced significant amounts of SElP in vitro. All 10 strains carryingsebandselpproduced SEB but not SElP, suggesting the inactivation of theselplocus inS. aureusstrains with a particularsegene constitution.
Borrelia burgdorferiOrganisms Lacking Plasmids 25 and 28-1 Are Internalized by Human Blood Phagocytes at a Rate Identical to That of the Wild-Type Strain
Authors: Al-Robaiy Samiya , Knauer Jens , Straubinger Reinhard K. 
Published: August 2005

ABSTRACTLyme borreliosis caused byBorrelia burgdorferiis a persistent infection capable of withstanding the host's vigorous immune response. Several reports have shown that the spirochete's linear plasmids 25 and 28-1 are essential for its infectivity. In this context, it was proposed thatBorrelia burgdorferiorganisms control their uptake by macrophages and polymorphonuclear leukocytes (PMNs) through plasmid-encoded proteins and that this mechanism confers resistance to phagocytosis. To investigate this proposal, a precise flow-cytometry-based method with human blood was used to study the impact of the plasmids 25 and 28-1 onB. burgdorfericlearance over 150 min and to investigate whether low-passage organisms are more resistant to phagocytosis than high-passageB. burgdorferi. Exposure of human blood PMNs or blood monocytes to fluorescein isothiocyanate-labeledB. burgdorferiB31 organisms lacking the linear plasmids 25, 28-1, or both revealed that all spirochete populations were internalized at the same rate as the wild-type borrelia parent strain B31. Moreover, no differences in phagocytosis kinetics were detected when low- or high-passage wild-typeB. burgdorferiB31 or N40 were cocultured with blood cells. Plasmid loss and probable associated surface protein changes due to serial in vitro propagation ofB. burgdorferido not affect the resistance of these organisms to internalization by phagocytic cells. In particular, we found no evidence for a plasmid-controlled (lp25 and lp28-1) resistance ofB. burgdorferito phagocytosis by leukocytes of the host's innate immune system.
Cholera Toxin Induces a Transient Depletion of CD8+Intraepithelial Lymphocytes in the Rat Small Intestine as Detected by Microarray and Immunohistochemistry
Authors: Flach Carl-Fredrik , Lange Stefan , Jennische Eva , Lönnroth Ivar , Holmgren Jan 
Published: August 2005

ABSTRACTCholera toxin (CT), besides causing intestinal hypersecretion after intragastric administration or during cholera infection, affects a multitude of regulatory mechanisms within the gut mucosal network, including T cells. By use of microarray screening, real-time PCR, and immunohistochemistry, we demonstrate here a rapid depletion of jejunal CD8+intraepithelial lymphocytes (IEL) in rats after intragastric CT challenge. This depletion may depend on CT-induced migration of IEL, since it was associated with a progressive decrease of CD8+cells in the epithelium and a contemporary transient increase of such cells, preferentially at the base of the villi, in the lamina propria. A significant decrease in the total number of villous CD8+cells at 6 and 18 h after CT challenge was detected; this possibly reflects an efflux from the jejunal mucosa. The kinetics of the CD8+IEL demonstrate the return to normal intraepithelial position at original numbers already 72 h after the single CT dose. The induced migration seems to be dependent on the enzymatic A-subunit of CT, since challenge with neither sorbitol nor CT B-subunit did mimic the effects of CT on CD8+IEL. Furthermore, a decrease in the level of both RANTES transcript and protein was detected, most likely as a consequence of the CT-induced migration of CD8+IEL. These results point to a complex interaction between CT, epithelial cells, and IEL, resulting in a disturbance of the gut homeostasis, which might have relevance for the strong immunomodulatory effects of intragastrically administered CT.
Bacteroides fragilis-Derived Lipopolysaccharide Produces Cell Activation and Lethal Toxicity via Toll-Like Receptor 4
Authors: Mancuso Giuseppe , Midiri Angelina , Biondo Carmelo , Beninati Concetta , Gambuzza Maria , Macrì Daniele , Bellantoni Antonella , Weintraub Andrej , Espevik Terje , Teti Giuseppe 
Published: August 2005

ABSTRACTBacteroides fragilis, which is part of the normal intestinal flora, is a frequent cause of serious disease, especially in diabetic and surgical patients. In these conditions,B. fragilislipopolysaccharide (LPS) is likely to play a major pathophysiologic role.B. fragilisLPS is structurally different from classical enterobacterial LPS, whose biological activities are mediated by Toll-like receptor 4 (TLR4) activation. The ability ofB. fragilisLPS to activate TLR4 and TLR2 was investigated here, since evidence on this issue is scarce and controversial. Each of four different protein-freeB. fragilisLPS preparations could induce interleukin-8 responses in cells cotransfected with TLR4/CD14/MD2 but not TLR4/CD14 alone. Two of the preparations also induced cytokine production in cells cotransfected with TLR2/CD14 or in peritoneal macrophages from TLR4 mutant C3H/HeJ mice. Both of these activities, however, were lost after repurification with a modified phenol reextraction procedure. Importantly, all preparations could induce endotoxic shock in TLR2-deficient mice, but not in TLR4 mutant C3H/HeJ mice. Consistent with these findings, anti-TLR4 and anti-CD14, but not anti-TLR2, antibodies could inhibitB. fragilisLPS-induced cytokine production in human monocytes. Collectively, these results indicate thatB. fragilisLPS signals via a TLR4/CD14/MD2-dependent pathway, and it is unable to activate TLR2. Moreover, our data document the occurrence of TLR2-activating contaminants even in highly purifiedB. fragilisLPS preparations. This may explain earlier contradictory findings on the ability ofB. fragilisLPS to activate cells in the absence of functional TLR4. These data may be useful to devise strategies to prevent the pathophysiologic changes observed duringB. fragilissepsis and to better understand structure-activity relationships of LPS.
Mutations Affecting Peptidoglycan Acetylation in
Neisseria gonorrhoeae
and
Neisseria meningitidis
Authors: Dillard Joseph P. , Hackett Kathleen T. 
Published: August 2005

ABSTRACT

Neisseria gonorrhoeae
acetylates its cell wall peptidoglycan (PG) at the C-6 position on
N
-acetylmuramic acid. To understand the effects of PG acetylation on PG metabolism and release of PG fragments, we have made mutations in the genes responsible for PG acetylation. An insertion mutation in a putative PG acetylase gene (designated
pacA
) resulted in loss of PG acetylation as detected by a high-performance liquid chromatography-based assay. Sequence analysis of a naturally occurring nonacetylating strain revealed the presence of a 26-bp deletion in
pacA
. Introduction of the deletion mutation into wild-type gonococci resulted in lack of acetylation, and the phenotype was complemented by the addition of a wild-type copy of
pacA
at a distant location on the chromosome. Mutations were also introduced into three genes downstream of
pacA
. The gene directly downstream of
pacA
was required for acetylation and was designated
pacB
, whereas the next two genes were not required. Sequences highly similar to
pacA
and
pacB
were also found in
N. meningitidis
and
N. lactamica
strains, and an insertion in the meningococcal
pacA
eliminated PG acetylation. Phenotypic analyses of an
N. gonorrhoeae pacA
mutant did not show any decrease in lysozyme resistance or serum resistance, and the release of PG fragments during growth was unchanged. However, purified PG from the wild-type strain was significantly more resistant to the action of human lysozyme than was PG purified from the
pacA
mutant. Interestingly, the
pacA
mutant was more sensitive to EDTA, a compound known to trigger autolysis.
Interaction of
Bartonella henselae
with Endothelial Cells Promotes Monocyte/Macrophage Chemoattractant Protein 1 Gene Expression and Protein Production and Triggers Monocyte Migration
Authors: McCord Amy M. , Burgess Andrew W. O. , Whaley Melissa J. , Anderson Burt E. 
Published: August 2005

ABSTRACT

Bacillary angiomatosis (BA), one of the many clinical manifestations resulting from infection with the facultative intracellular bacterium
Bartonella henselae
, is characterized by angiogenic lesions. Macrophages have been identified as important effector cells contributing to the angiogenic process during
B. henselae
infection by infiltrating BA lesions and secreting vascular endothelial growth factor. Monocyte-macrophage chemoattractant protein 1 (MCP-1) recruits macrophages to sites of inflammation. In this study, we investigated the ability of
B. henselae
to upregulate MCP-1 gene expression and protein production in the human microvascular endothelial cell line HMEC-1. MCP-1 mRNA was induced at 6 and 24 h after treatment with bacteria, whereas protein production was elevated at 6, 24, and 48 h. This induction was not dependent on the presence of bacterial lipopolysaccharide or endothelial cell toll-like receptor 4. However, MCP-1 production was dependent on NF-κB activity. Outer membrane proteins of low molecular weight were able to upregulate MCP-1 production. Furthermore, supernatants from
B. henselae
-infected HMEC-1 were able to induce chemotaxis of THP-1 monocytes. These data suggest a mechanism by which the macrophage effector cell is recruited to the endothelium during
B. henselae
infection and then contributes to bacterial-induced angiogenesis.