bluuebunny/crossref_metadata_2025_split huggingface dataset:
Roles of Cellular Activation and Sulfated Glycans inHaemophilus somnusAdherence to Bovine Brain Microvascular Endothelial Cells
Authors: Behling-Kelly E. , Vonderheid H. , Kim Kwang Sik , Corbeil L. B. , Czuprynski C. J. 
Published: August 2006

ABSTRACTHaemophilus somnuscan cause a devastating fibrinopurulent meningitis with thrombotic vasculitis and encephalitis in cattle. The mechanisms used byH. somnusto migrate from the bloodstream into the central nervous system (CNS) are unknown. In this study, we demonstrate thatH. somnusadheres to, but does not invade, bovine brain endothelial cells (BBEC) in vitro. The number of adherentH. somnuswas significantly increased by prior activation of the BBEC with tumor necrosis factor alpha (TNF-α). Addition of exogenous glycosaminoglycans significantly reducedH. somnusadherence to resting and TNF-α-activated BBEC. Heparinase digestion of the endothelial cell's glycocalyx or sodium chlorate inhibition of endothelial cell sulfated glycan synthesis significantly reduced the number of adherentH. somnus. In contrast, addition of hyaluronic acid, a nonsulfated glycosaminoglycan, had no inhibitory effect. These findings suggest a critical role for both cellular activation and sulfated glycosaminoglycans in adherence ofH. somnusto BBEC. Using heparin-labeled agarose beads, we demonstrated a high-molecular-weight heparin-binding protein expressed byH. somnus. Heparin was also shown to bindH. somnusin a 4°C binding assay. These data suggest that heparin-binding proteins onH. somnuscould serve as initial adhesins to sulfated proteoglycans on the endothelial cell surface, thus contributing to the ability ofH. somnusto infect the bovine CNS.
Autocrine Role for Interleukin-8 in
Bartonella henselae
-Induced Angiogenesis
Authors: McCord Amy M. , Resto-Ruiz Sandra I. , Anderson Burt E. 
Published: August 2006

ABSTRACT

The gram-negative bacterium
Bartonella henselae
is capable of causing angiogenic lesions as a result of infection. Previously, it has been shown that
B. henselae
infection can result in production of the chemokine interleukin-8 (IL-8). In this study, we demonstrated that monocytes, endothelial cells, and hepatocytes produce IL-8 in response to
B. henselae
infection. We also investigated the role of IL-8 in
B. henselae
-induced endothelial cell proliferation and capillary tube formation. Both in vitro angiogenesis assays were IL-8 dependent.
B. henselae
-mediated inhibition of apoptosis, as indicated by gene expression of
Bax
and
Bcl-2
, was also shown to be IL-8 dependent in endothelial cells. Furthermore, infection of endothelial cells with
B. henselae
stimulated upregulation of the IL-8 chemokine receptor CXCR2. Infection of human endothelial cells by
B. henselae
resulting in IL-8 production likely plays a central role in the ability of this organism to cause angiogenesis during infection.
Role of Capsule and Interleukin-6 in Long-Term Immune Control ofCryptococcus neoformansInfection by Specifically Activated Human Peripheral Blood Mononuclear Cells
Authors: Siddiqui Asna A. , Shattock Robin J. , Harrison Thomas S. 
Published: August 2006

ABSTRACTCryptococcus neoformansis a frequent cause of meningoencephalitis in immunosuppressed individuals. To better understand the mechanisms of a protective immune response toC. neoformans, a long-term in vitro model of human immune control of cryptococcal infection was developed. Peripheral blood mononuclear cells (PBMC) prestimulated with heat-killedC. neoformanssignificantly restricted the growth ofC. neoformansafter a subsequent live infection compared to that with unstimulated PBMC. Live infection with encapsulatedC. neoformanswas controlled for as long as 10 days, while infection with acapsular organisms could sometimes be eradicated. During immune control, fungal cells were both intracellular and extracellular within aggregates of mononuclear phagocytes and lymphocytes. Optimal immune control depended on the presence of both CD4+and CD8+T cells. Immune control of cryptococcal growth was more effective following prestimulation with acapsular compared with encapsulated organisms. Prestimulation with acapsular organisms was associated with a significant and prolonged increase in interleukin-6 (IL-6) production compared with prestimulation with encapsulatedC. neoformans. Addition of IL-6 and depletion of CD25+T cells prior to prestimulation and infection with encapsulated organisms resulted in reductions in cryptococcal growth that reached borderline statistical significance. Depletion of CD25+T cells significantly reduced cryptococcal growth in wells with unstimulated PBMC. The results demonstrate an association between high levels of IL-6 and resistance to infection and, through suppression of IL-6 release, an additional mechanism whereby the cryptococcal capsule subverts a protective immune response. Further work is required to clarify the mechanism of action of IL-6 in this setting and any interaction with regulatory T cells.
Innate Immune Responses to Lung-Stage Helminth Infection Induce Alternatively Activated Alveolar Macrophages
Authors: Reece Joshua J. , Siracusa Mark C. , Scott Alan L. 
Published: August 2006

ABSTRACTWhile it is well established that infection with the rodent hookwormNippostrongylus brasiliensisinduces a strongly polarized Th2 immune response, little is known about the innate host-parasite interactions that lead to the development of this robust Th2 immunity. We exploited the transient pulmonary phase ofN. brasiliensisdevelopment to study the innate immune responses induced by this helminth parasite in wild-type (WT) and severe-combined immune deficient (SCID) BALB/c mice. Histological analysis demonstrated that the cellular infiltrates caused byN. brasiliensistransit through the lungs were quickly resolved in WT mice but not in SCID mice. Microarray-based gene expression analysis demonstrated that there was a rapid induction of genes encoding molecules that participate in innate immunity and in repair/remodeling during days 2 to 4 postinfection in the lungs of WT and SCID mice. Of particular note was the rapid upregulation in both WT and SCID mice of the genes encoding YM1, FIZZ1, and Arg1, indicating a role for alternatively activated macrophages (AAMs) in pulmonary innate immunity. Immunohistochemistry revealed that nearly all alveolar macrophages became YM1-producing AAMs as early as day 2 postinfection. While the innate responses induced during the lung phase ofN. brasiliensisinfection were similar in complexity and magnitude in WT and SCID mice, only mice with functional T cells were capable of maintaining elevated levels of gene expression beyond the innate window of reactivity. The induction of alternatively activated alveolar macrophages could be important for dampening the level of inflammation in the lungs and contribute to the long-term decrease in pulmonary inflammation that has been associated with helminth infections.
Construction of a Mutant and Characterization of the Role of the Vaccine Antigen P6 in Outer Membrane Integrity of NontypeableHaemophilus influenzae
Authors: Murphy Timothy F. , Kirkham Charmaine , Lesse Alan J. 
Published: August 2006

ABSTRACTOuter membrane protein P6 is the subject of investigation as a vaccine antigen to prevent infections caused by nontypeableHaemophilus influenzae, which causes otitis media in children and respiratory tract infections in adults with chronic lung disease. P6 induces protective immune responses in animal models and is the target of potentially protective immune responses in humans. P6 is a 16-kDa lipoprotein that shares homology with the peptidoglycan-associated lipoproteins of gram-negative bacteria and is highly conserved among strains ofH. influenzae. To characterize the function of P6, an isogenic mutant was constructed by replacing the P6 gene with a chloramphenicol resistance cassette. The P6 mutant showed altered colony morphology and slower growth in vitro than that of the parent strain. By electron microscopy, the P6 mutant cells demonstrated increased size, variability in size, vesicle formation, and fragility compared to the parent cells. The P6 mutant showed hypersensitivity to selected antibiotics with different mechanisms of action, indicating increased accessibility of the agents to their targets. The P6 mutant was more sensitive to complement-mediated killing by normal human serum. Complementation of the mutation intranscompletely or partially restored the phenotypes. We concluded that P6 plays a structural role in maintaining the integrity of the outer membrane by anchoring the outer membrane to the cell wall. The observation that the absence of expression of P6 is detrimental to the cell is a highly desirable feature for a vaccine antigen, supporting further investigation of P6 as a vaccine candidate forH. influenzae.
Role of Intrachain Disulfides in the Activities of the CdtA and CdtC Subunits of the Cytolethal Distending Toxin ofActinobacillus actinomycetemcomitans
Authors: Cao Linsen , Volgina Alla , Korostoff Jonathan , DiRienzo Joseph M. 
Published: August 2006

ABSTRACTThe cytolethal distending toxin (Cdt) ofActinobacillus actinomycetemcomitansis an atypical A-B-type toxin consisting of a heterotrimer composed of thecdtA,cdtB, andcdtCgene products. The CdtA and CdtC subunits form two heterogeneous ricin-like lectin domains which bind the holotoxin to the target cell. Point mutations were used to study CdtC structure and function. One (mutC216F97C) of eight single-amino-acid replacement mutants identified yielded a gene product that failed to form biologically active holotoxin. Based on the possibility that the F97C mutation destabilized a predicted disulfide, targeted mutagenesis was used to examine the contribution of each of four cysteine residues, in two predicted disulfides (C96/C107 and C135/C149), to CdtC activities. Cysteine replacement mutations in two predicted disulfides (C136/C149 and C178/C197) in CdtA were also characterized. Flow cytometry and CHO cell proliferation assays showed that changing either C96 or C149 in CdtC to alanine abolished the biological activity of holotoxin complexes. However, replacing C107 or C135 in CdtC and any of the four cysteines in CdtA with alanine or serine resulted in only partial or no loss of holotoxin activity. Changes in the biological activities of the mutant holotoxins correlated with altered subunit binding. In contrast to elimination of the B chain of ricin, the elimination of intrachain disulfides in CdtC and CdtA by genetic replacement of cysteines destabilizes these subunit proteins but not to the extent that cytotoxicity is lost. Reduction of the wild-type holotoxin did not affect cytotoxicity, and the reduced form of wild-type CdtA exhibited a statistically significant increase in binding to ligand. A diminished role for intrachain disulfides in stabilizing CdtA and CdtC may have clinical relevance for theA. actinomycetemcomitansCdt. Thecdtgene products secreted by this pathogen assemble and bind to target cells in periodontally involved sites, which are decidedly reduced environments in the human oral cavity.
Biochemical Activities of Three Pairs of
Ehrlichia chaffeensis
Two-Component Regulatory System Proteins Involved in Inhibition of Lysosomal Fusion
Authors: Kumagai Yumi , Cheng Zhihui , Lin Mingqun , Rikihisa Yasuko 
Published: August 2006

ABSTRACT

Ehrlichia chaffeensis
, the etiologic agent of human monocytic ehrlichiosis, replicates in early endosomes by avoiding lysosomal fusion in monocytes and macrophages. In
E. chaffeensis
we predicted three pairs of putative two-component regulatory systems (TCSs) designated PleC-PleD, NtrY-NtrX, and CckA-CtrA based on amino acid sequence homology. In the present study to determine biochemical pairs and specificities of the TCSs, the recombinant proteins of the three putative histidine kinase (HK) kinase domains (rPleCHKD, rNtrYHKD, and MBP-rCckAHKD) and the full-length forms of three putative response regulators (RRs) (rPleD, rNtrX, and rCtrA) as well as the respective mutant recombinant proteins (rPleCHKDH244A, rNtrYHKDH498A, MBP-rCckAHKDH449A, rPleDD53A, rNtrXD59A, and rCtrAD53A) were expressed and purified as soluble proteins. The in vitro HK activity, the specific His residue-dependent autophosphorylation of the kinase domain, was demonstrated in the three HKs. The specific Asp residue-dependent in vitro phosphotransfer from the kinase domain to the putative cognate RR was demonstrated in each of the three RRs. Western blot analysis of
E. chaffeensis
membrane and soluble fractions using antibodies specific for each recombinant protein detected PleC and CckA in the membrane fraction, whereas it detected NtrY, NtrX, and PleD in the soluble fraction. CtrA was found in the two fractions at similar levels.
E. chaffeensis
was sensitive to closantel, an HK inhibitor. Closantel treatment induced lysosomal fusion of the
E. chaffeensis
inclusion in a human monocytic leukemia cell line, THP-1 cells, implying that functional TCSs are essential in preventing lysosomal fusion of the
E. chaffeensis
inclusion compartment.
N
-Acetyllactosamine Conjugated to Gold Nanoparticles Inhibits Enteropathogenic
Escherichia coli
Colonization of the Epithelium in Human Intestinal Biopsy Specimens
Authors: Hyland Romney M. , Beck Paul , Mulvey George L. , Kitov Pavel I. , Armstrong Glen D. 
Published: August 2006

ABSTRACT

We previously reported that the bundle-forming pilus-mediated localized adherence of enteropathogenic
Escherichia coli
to HEp-2, T84, and Caco-2 cells is inhibited by
N
-acetyllactosamine neoglycoconjugates. The results presented here extend this observation to the epithelium of biopsy specimens obtained from the human adult duodenum, terminal ileum, and colon.
Different Consequences of
ACE2
and
SWI5
Gene Disruptions for Virulence of Pathogenic and Nonpathogenic Yeasts
Authors: MacCallum Donna M. , Findon Helen , Kenny Claire C. , Butler Geraldine , Haynes Ken , Odds Frank C. 
Published: August 2006

ABSTRACT

Mutants of
Candida albicans
,
Candida glabrata
, and
Saccharomyces cerevisiae
with disruptions in the
ACE2
gene and
C. glabrata
and
S. cerevisiae swi5
disruption mutants were tested for virulence in a murine challenge model of disseminated yeast infection. All mutants showed a clumping phenotype, but clumping was minimized in challenge inocula by inclusion of chitinase in the growth medium. In animals rendered temporarily neutropenic by cyclophosphamide treatment, the
C. glabrata ace2
null mutant was confirmed as hypervirulent: it led to early terminal illness and kidney, brain, and lung fungal burdens substantially and significantly larger than those in controls. The
C. glabrata swi5
null mutant did not lead to terminal illness but generated significantly larger brain and lung burdens than those in controls. The
C. albicans ace2
null mutant was very slightly attenuated and the
S. cerevisiae ace2
and
swi5
null mutants were substantially attenuated relative to their parental control strains. The phenotype of aggressive hypervirulence, unique to disruption of the
C. glabrata ACE2
gene among the strains tested, was not seen when the
C. glabrata ace2
strain was tested in immunologically intact mice. The different effects seen with these mutants rule out the clumping phenotype as the explanation for hypervirulence in the
C. glabrata ace2
mutant. The absence of
C. glabrata ace2
hypervirulence in healthy mice may be a tool for definitive future study of host-parasite cross talk in microbial opportunism.
Acquisition of Hemozoin by Monocytes Down-Regulates Interleukin-12 p40 (IL-12p40) Transcripts and Circulating IL-12p70 through an IL-10-Dependent Mechanism: In Vivo and In Vitro Findings in Severe Malarial Anemia
Authors: Keller Christopher C. , Yamo Ouma , Ouma Collins , Ong'echa John Michael , Ounah David , Hittner James B. , Vulule John M. , Perkins Douglas J. 
Published: August 2006

ABSTRACTSevere malarial anemia (SMA) is a primary cause of morbidity and mortality in immune-naïve infants and young children residing in areas of holoendemicPlasmodium falciparumtransmission. Although the immunopathogenesis of SMA is largely undefined, we have previously shown that systemic interleukin-12 (IL-12) production is suppressed during childhood blood-stage malaria. Since IL-10 and tumor necrosis factor alpha (TNF-α) are known to decrease IL-12 synthesis in a number of infectious diseases, altered transcriptional regulation of these inflammatory mediators was investigated as a potential mechanism for IL-12 down-regulation. Ingestion of naturally acquired malarial pigment (hemozoin [PfHz]) by monocytes promoted the overproduction of IL-10 and TNF-α relative to the production of IL-12, which correlated with an enhanced severity of malarial anemia. Experiments with cultured peripheral blood mononuclear cells (PBMC) and CD14+cells from malaria-naïve donors revealed that physiological concentrations of PfHz suppressed IL-12 and augmented IL-10 and TNF-α by altering the transcriptional kinetics of IL-12p40, IL-10, and TNF-α, respectively. IL-10 neutralizing antibodies, but not TNF-α antibodies, restored PfHz-induced suppression of IL-12. Blockade of IL-10 and the addition of recombinant IL-10 to cultured PBMC from children with SMA confirmed that IL-10 was responsible for malaria-induced suppression of IL-12. Taken together, these results demonstrate that PfHz-induced up-regulation of IL-10 is responsible for the suppression of IL-12 during malaria.
In Vivo Bioluminescence Imaging of the Murine Pathogen
Citrobacter rodentium
Authors: Wiles Siouxsie , Pickard Karen M. , Peng Katian , MacDonald Thomas T. , Frankel Gad 
Published: August 2006

ABSTRACT

Citrobacter rodentium
is a natural mouse pathogen related to enteropathogenic and enterohemorrhagic
Escherichia coli
. We have previously utilized bioluminescence imaging (BLI) to determine the in vivo colonization dynamics of
C. rodentium
. However, due to the oxygen requirement of the bioluminescence system and the colonic localization of
C. rodentium
, in vivo localization studies were performed using harvested organs. Here, we report the detection of bioluminescent
C. rodentium
and commensal
E. coli
during colonization of the gastrointestinal tract in intact living animals. Bioluminescence was dependent on intact blood circulation, suggesting that the colonic environment is not anaerobic but nanaerobic. In addition, BLI revealed that
C. rodentium
colonizes the rectum, a site previously unreported for this pathogen.
Nucleotide Sequence Analysis of the Enteropathogenic
Escherichia coli
Adherence Factor Plasmid pMAR7
Authors: Brinkley Carl , Burland Valerie , Keller Rogéria , Rose Debra J. , Boutin Adam T. , Klink Sara A. , Blattner Frederick R. , Kaper James B. 
Published: August 2006

ABSTRACT

The complete nucleotide sequence was determined for pMAR7, an enteropathogenic
Escherichia coli
(EPEC) adherence factor (EAF) plasmid that contains genes encoding a type IV attachment pilus (Bfp) and the global virulence regulator
per
. Prototypic EAF plasmid pMAR7 is self-transmissible, unlike the smaller EAF plasmid pB171, which has no genes encoding conjugative functions. The
tra
locus, a highly conserved 33-kb segment found in pMAR7, is similar to the
tra
(conjugation) region of the F plasmid. IS
Ec13
copies flanking the pMAR7
tra
region could potentially mobilize or delete the
tra
genes. Hybridization of 134 EPEC strains showed that a complete
tra
region is present only in strains of the EPEC1 clonal group. This study confirms EPEC's potential for dissemination of virulence attributes by horizontal transfer of the EAF plasmid.
Interplay of Pneumococcal Hydrogen Peroxide and Host-Derived Nitric Oxide
Authors: Hoffmann Olaf , Zweigner Janine , Smith Shannon H. , Freyer Dorette , Mahrhofer Cordula , Dagand Emilie , Tuomanen Elaine I. , Weber Joerg R. 
Published: August 2006

ABSTRACTReactive oxygen and nitrogen species are released by immune-competent cells and contribute to cellular damage. On the other hand, certain pathogens, includingStreptococcus pneumoniae, are known to produce hydrogen peroxide (H2O2), while production of nitrogen radicals by bacteria presumably occurs but has been poorly studied. We determined the relative contributions of bacterial versus host-derived oxygen and nitrogen radicals to cellular damage in pneumococcal infection. A special focus was placed on peroxynitrite as a hypothetical common product formed by the reaction of H2O2and NO. In microglial cultures, reduction of the formation of 3-nitrotyrosine and cellular damage required H2O2-deficient (ΔspxBor ΔcarB) pneumococci and inhibition of host NO synthesis with aminoguanidine. In infected C57BL/6 mice, neuronal loss and immunopositivity for nitrotyrosine in the dentate gyrus were markedly reduced with ΔspxBor ΔcarBbacterial mutants and in inducible nitric oxide synthase knockout mice. We conclude that although host and bacteria both produce oxygen and nitrogen radicals, the interplay of prokaryotic H2O2and eukaryotic NO is a major contributor to cellular damage in pneumococcal meningitis.
Brucella melitensisTriggers Time-Dependent Modulation of Apoptosis and Down-Regulation of Mitochondrion-Associated Gene Expression in Mouse Macrophages
Authors: He Yongqun , Reichow Sherry , Ramamoorthy Sheela , Ding Xicheng , Lathigra Raju , Craig Johanna C. , Sobral Bruno W. S. , Schurig Gerhardt G. , Sriranganathan Nammalwar , Boyle Stephen M. 
Published: August 2006

ABSTRACTBrucellaspp. are facultative intracellular bacteria that cause brucellosis in humans and other animals.Brucellaspp. are taken up by macrophages, and the outcome of the macrophage-Brucellainteraction is a basis for establishment of a chronicBrucellainfection. Microarrays were used to analyze the transcriptional response of the murine macrophage-like J774.A1 cell line to infection with virulentBrucella melitensisstrain 16M. It was found that most significant changes in macrophage gene transcription happened early following infection, and global macrophage gene expression profiles returned to normal between 24 and 48 h postinfection. These findings support the observation that macrophages kill the majority ofBrucellacells at the early infection stage, but the survivingBrucellacells are able to avoid macrophage brucellacidal activity inside replicative phagosomes at the later infection stage. At 4 h postinfection, macrophage genes involved in cell growth, metabolism, and responses to endogenous stimuli were down-regulated, while the inflammatory response (e.g., tumor necrosis factor alpha and Toll-like receptor 2), the complement system, the responses to external stimuli, and other immune responses were up-regulated. It is likely that the most active brucellacidal activity happened between 0 and 4 h postinfection. Mitochondrion-associated gene expression, which is involved in protein synthesis and transport, electron transfer, and small-molecule transfer, and many other mitochondrial functions were significantly down-regulated at 4 h postinfection. Although there were both pro- and antiapoptosis effects,B. melitensis16M appears to inhibit apoptosis of macrophages by blocking release of cytochromecand production of reactive oxygen species in the mitochondria, thus preventing activation of caspase cascades.