bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental Pneumococcal Meningitis: Impaired Clearance of Bacteria from the Blood Due to Increased Apoptosis in the Spleen in Bcl-2-Deficient Mice
Authors: Wellmer Andreas , von Mering Matthias , Spreer Annette , Diem Ricarda , Eiffert Helmut , Noeske Christiane , Bunkowski Stefanie , Gold Ralf , Nau Roland 
Published: May 2004

ABSTRACTNecrotic and apoptotic neuronal cell death can be found in pneumococcal meningitis. We investigated the role of Bcl-2 as an antiapoptotic gene product in pneumococcal meningitis using Bcl-2 knockout (Bcl-2−/−) mice. By using a model of pneumococcal meningitis induced by intracerebral infection, Bcl-2-deficient mice and control littermates were assessed by clinical score and a tight rope test at 0, 12, 24, 32, and 36 h after infection. Then mice were sacrificed, the bacterial titers in blood, spleen, and cerebellar homogenates were determined, and the brain and spleen were evaluated histologically. The Bcl-2-deficient mice developed more severe clinical illness, and there were significant differences in the clinical score at 24, 32, and 36 h and in the tight rope test at 12 and 32 h. The bacterial titers in the blood were greater in Bcl-2-deficient mice than in the controls (7.46 ± 1.93 log CFU/ml versus 5.16 ± 0.96 log CFU/ml [mean ± standard deviation];P< 0.01). Neuronal damage was most prominent in the hippocampal formation, but there were no significant differences between groups. In situ tailing revealed only a few apoptotic neurons in the brain. In the spleen, however, there were significantly more apoptotic leukocytes in Bcl-2-deficient mice than in controls (5,148 ± 3,406 leukocytes/mm2versus 1,070 ± 395 leukocytes/mm2;P< 0.005). Bcl-2 appears to counteract sepsis-induced apoptosis of splenic lymphocytes, thereby enhancing clearance of bacteria from the blood.
Interleukin-10 Limits Local and Body Cavity Inflammation during Infection with Muscle-StageTrichinella spiralis
Authors: Beiting Daniel P. , Bliss Susan K. , Schlafer Donald H. , Roberts Victoria L. , Appleton Judith A. 
Published: May 2004

ABSTRACTThe aim of this study was to characterize cellular responses to muscle-stageTrichinella spiralis. From its intracellular habitat in muscle,T. spiralissecretes potent glycoprotein antigens that elicit a strong systemic host immune response. Despite the magnitude and prolonged nature of this response, nurse cells are rarely destroyed by infiltrating cells. We tested the hypothesis that the anti-inflammatory cytokine interleukin-10 (IL-10) moderates cellular responses to muscle-stage parasites.Trichinellalarvae colonize the diaphragm in large numbers, prompting us to evaluate regional responses in body cavities in addition to local responses in muscle. Mice deficient in IL-10 demonstrated an exaggerated inflammatory response around nurse cells and in the pleural cavity. The effect of IL-10 was most evident 20 days following muscle infection. The increased intensity of the response in IL-10-deficient mice did not affect parasite establishment or survival. Between 20 and 50 days postinfection, the inflammatory response was diminished in both wild-type and IL-10-deficient mice. Muscle infection also elicited an antibody response, characterized initially by mixed isotypes directed at somatic larval antigens and changing to an immunoglobulin G1-dominated response directed at tyvelose-bearing excreted or secreted antigens. We conclude that IL-10 limits local and regional inflammation during the early stages of muscle infection but that chronic inflammation is controlled by an IL-10-independent mechanism that is coincident with a Th2 response.
Borrelia burgdorferi
Binds to, Invades, and Colonizes Native Type I Collagen Lattices
Authors: Zambrano Maria C. , Beklemisheva Anastasia A. , Bryksin Anton V. , Newman Stuart A. , Cabello Felipe C. 
Published: May 2004

ABSTRACT

Borrelia burgdorferi
binds strongly to the extracellular matrix and cells of the connective tissue, a binding apparently mediated by specific proteins and proteoglycans. We investigated the interactions between
B. burgdorferi
cells and intact type I collagen using hydrated lattices that reproduce features of in vivo collagen matrices.
B. burgdorferi
cells of several strains adhered avidly to these acellular matrices by a mechanism that was not mediated by decorin or other proteoglycans. Moreover, following adhesion to these matrices,
B. burgdorferi
grew and formed microcolonies. The collagen used in these studies was confirmed to lack decorin by immunoblot analysis;
B. burgdorferi
cells lacking the decorin adhesin bound readily to intact collagen matrices.
B. burgdorferi
also bound to collagen lattices that incorporated enzymes that degraded glycosaminoglycan chains in any residual proteoglycans. Binding of the bacteria to intact collagen was nonetheless specific, as bacteria did not bind agar and showed only minimal binding to bovine serum albumin, gelatin, pepsinized type I collagen, and intact collagen that had been misassembled under nonphysiological pH and ionic-strength conditions. Proteinase K treatment of
B. burgdorferi
cells decreased the binding, as did a lack of flagella, suggesting that surface-exposed proteins and motility may be involved in the ability of
B. burgdorferi
to interact with intact collagen matrices. The high efficiency of binding of
B. burgdorferi
strains to intact collagen matrices permits replacement of the commonly used isotopic binding assay with visual fluorescent microscopic assays and will facilitate future studies of these interactions.
Comparative Analysis of B- and T-Cell Epitopes ofMycobacterium lepraeandMycobacterium tuberculosisCulture Filtrate Protein 10
Authors: Spencer John S. , Kim Hee Jin , Marques Angela M. , Gonzalez-Juarerro Mercedes , Lima Monica C. B. S. , Vissa Varalakshmi D. , Truman Richard W. , Gennaro Maria Laura , Cho Sang-Nae , Cole Stewart T. , Brennan Patrick J. 
Published: May 2004

ABSTRACTCulture filtrate protein 10 (CFP-10) fromMycobacterium tuberculosisis a well-characterized immunodominant 10-kDa protein antigen known to elicit a very potent early gamma interferon response in T cells fromM. tuberculosis-infected mice and humans. The sequence of theMycobacterium lepraehomologue of CFP-10 shows only 40% identity (60% homology) at the protein level withM. tuberculosisCFP-10 and thus has the potential for development as a T- or B-cell reactive antigen for specific diagnosis of leprosy. Antisera raised in mice or rabbits against recombinantM. lepraeandM. tuberculosisCFP-10 proteins reacted only with homologous peptides from arrays of overlapping synthetic peptides, indicating that there was no detectable cross-reactivity at the antibody level. Sera from leprosy and tuberculosis patients were also specific for the homologous protein or peptides and showed distinct patterns of recognition for eitherM. lepraeorM. tuberculosisCFP-10 peptides. At the cellular level, only 2 of 45 mouse T-cell hybridomas raised against eitherM. lepraeorM. tuberculosisCFP-10 displayed a cross-reactive response against the N-terminal heterologous CFP-10 peptide, the region that exhibits the highest level of identity in the two proteins; however, the majority of peptide epitopes recognized by mouse T-cell hybridomas specific for each protein did not cross-react with heterologous peptides. Coupled with the human serology data, these results raise the possibility that peptides that could be used to differentiate infections caused by these two related microorganisms could be developed. Immunohistochemical staining of sections ofM. leprae-infected nude mouse footpads resulted in strongly positive staining in macrophages and dendritic cells, as well as weaker staining in extracellular areas, suggesting thatM. lepraeCFP-10, like its homologue inM. tuberculosis, is a secreted protein.
Identification of Acyloxyacyl Hydrolase, a Lipopolysaccharide- Detoxifying Enzyme, in the Murine Urinary Tract
Authors: Feulner J. Amelia , Lu Mingfang , Shelton JohnM. , Zhang Mei , Richardson James A. , Munford Robert S. 
Published: May 2004

ABSTRACTAcyloxyacyl hydrolase (AOAH) is an unusual but highly conserved lipase, previously described only in myeloid cells, that removes secondary fatty acyl chains from bacterial lipopolysaccharides (LPS) and may also act on various glycero(phospho)lipids. Deacylation by AOAH greatly reduces the ability of LPS to stimulate cells via CD14-MD-2-Toll-like receptor 4. We report here that renal cortical tubule cells produce AOAH and secrete it into urine, where it can deacylate LPS. In vitro studies revealed that proximal tubule cells secrete pro-AOAH, which can be taken up by bladder cells and processed to the heterodimeric, more enzymatically active, mature form of AOAH. AOAH can then be used by the recipient cells to deacylate LPS. The enzyme produced by proximal tubule epithelium may thus be shared with downstream cells. In addition, mature AOAH is found in the urine. We suggest that cortical tubule cells may produce and secrete AOAH to limit inflammatory responses to gram-negative bacteria throughout the urinary tract.
Toll-Like Receptor 4 Expression and Cytokine Responses in the Human Urinary Tract Mucosa
Authors: Samuelsson Patrik , Hang Long , Wullt Björn , Irjala Heikki , Svanborg Catharina 
Published: May 2004

ABSTRACTMucosal pathogens trigger a local innate host response by activating epithelial cells. Bacterial adherence and Toll-like receptor 4 (TLR4) signaling have been implicated as key events in this process. This study addressed the molecular basis of the epithelial response to gram-negative infection in the human urinary tract. Mucosal biopsies were obtained from kidneys, ureters, and bladders of patients undergoing urinary tract surgery, and epithelial TLR4 and CD14 expression was examined by immunohistochemistry. TLR4 was detected in epithelial cells lining the entire urinary tract and in the renal tubular epithelium. CD14, in contrast, was completely absent from the epithelial tissue. The response of the epithelial cells to infection was studied by in vitro challenge of the biopsies with uropathogenicEscherichia colibacteria. A rapid cytokine response was observed, with production of interleukin-1β (IL-1β), IL-6, and IL-8 but not of IL-4 or gamma interferon. Adhering, P- or type 1-fimbriatedE. coliactivated IL-6 and IL-8 production more efficiently than the nonfimbriated control, as shown by cellular staining and analysis of secreted cytokines. The results demonstrate that human uroepithelial cells possess the molecular machinery needed to respond to uropathogenicE. coli. This includes recognition receptors for fimbriae and TLR4 for transmembrane signaling. We speculate that the lack of membrane-bound CD14 allows the epithelium to regulate its sensitivity to lipopolysaccharide and to discriminate between more-virulent and less-virulent strains.
Bacterial Superantigen-Treated Intestinal Epithelial Cells Upregulate Heat Shock Proteins 25 and 72 and Are Resistant to Oxidant Cytotoxicity
Authors: Musch Mark W. , Petrof Elaine O. , Kojima Keishi , Ren Hongyu , McKay Derek M. , Chang Eugene B. 
Published: May 2004

ABSTRACTWhile the pathological events evoked by infection are commonly described, effective host responses to bacteria and their products should primarily be protective. Heat shock protein (Hsp) expression is upregulated by many stimuli and serves to maintain intracellular protein integrity. The ability of the prototypic superantigen,Staphylococcus aureusenterotoxin B (SEB) to induce Hsps was investigated with BALB/c mice and by in vitro addition to the murine small intestinal epithelial cell line MSIE. SEB-treated (5 or 100 μg intraperitoneally) mice revealed increased Hsp25 and Hsp72, but not Hsc73, in jejunal lymphocytes and epithelial cells. A similar Hsp response to SEB occurred in MSIE cells and was preceded by activation of the ERK1/2 and p38 mitogen-activated protein kinases but not the SAPK/JNK pathway; pharmacological inhibition of ERK1/2, but not p38, significantly reduced SEB-induced Hsps. Moreover, SEB-treated MSIE cells were protected against oxidant-induced cytotoxicity (measured by51Cr release) and F-actin depolymerization. Thus, SEB exposure results in a rapid induction of the Hsp25 and Hsp72 in intestinal epithelial cells, both directly and through lymphocyte activation, and we suggest that this event is important in protecting the gut from damage byStaphylococcusinfection or in the reparatory process and may be a generalized response to lumen-derived bacterial toxins.
Comparative Analysis of EspF from Enteropathogenic and Enterohemorrhagic
Escherichia coli
in Alteration of Epithelial Barrier Function
Authors: Viswanathan V. K. , Koutsouris Athanasia , Lukic Sandra , Pilkinton Mark , Simonovic Ivana , Simonovic Miljan , Hecht Gail 
Published: May 2004

ABSTRACT

Enteropathogenic
Escherichia coli
(EPEC) and enterohemorrhagic
E. coli
(EHEC) are related intestinal pathogens that harbor highly similar pathogenicity islands known as the locus of enterocyte effacement (LEE). Despite their genetic similarity, these two pathogens disrupt epithelial tight junction barrier function with distinct kinetics. EHEC-induced reduction in transepithelial electrical resistance (TER), a measure of barrier function disruption, is significantly slower and more modest in comparison to that induced by EPEC. The variation in bacterial adherence only partially accounted for these differences. The LEE-encoded effector protein EspF has been shown to be critical for EPEC-induced alterations in TER. EspF from both EPEC and EHEC is expressed and secreted upon growth in tissue culture medium. The mutation of EHEC
cesF
suggested that the optimal expression and secretion of EHEC EspF required its chaperone CesF, as has been shown for EPEC. In contrast to EPEC
espF
and
cesF
, mutation of the corresponding EHEC homologs did not dramatically alter the decrease in TER. These differences could possibly be explained by the presence of additional
espF
-like sequences (designated U- and M-
espF
, where the letter designations refer to the specific cryptic prophage sequences on the EHEC chromosome closest to the respective genes) in EHEC. Reverse transcription-PCR analyses revealed coordinate regulation of EHEC U-
espF
and the LEE-encoded
espF
, with enhanced expression in bacteria grown in Dulbecco-Vogt modified Eagle’s medium compared to bacteria grown in Luria broth. Both EHEC
espF
and U-
espF
complemented an EPEC
espF
deletion strain for barrier function alteration. The overexpression of U-
espF
, but not
espF
, in wild-type EHEC potentiated the TER response. These studies reveal further similarities and differences in the pathogenesis of EPEC and EHEC.
Role of Flagellin and the Two-Component CheA/CheY System of
Listeria monocytogenes
in Host Cell Invasion and Virulence
Authors: Dons Lone , Eriksson Emma , Jin Yuxuan , Rottenberg Martin E. , Kristensson Krister , Larsen Charlotte N. , Bresciani José , Olsen John E. 
Published: May 2004

ABSTRACT

The flagellum protein flagellin of
Listeria monocytogenes
is encoded by the
flaA
gene. Immediately downstream of
flaA
, two genes,
cheY
and
cheA
, encoding products with homology to chemotaxis proteins of other bacteria, are located. In this study we constructed deletion mutants with mutations in
flaA. cheY
, and
cheA
to elucidate their role in the biology of infection with
L. monocytogenes
. The Δ
cheY
, Δ
cheA
, and double-mutant Δ
cheYA
mutants, but not Δ
flaA
mutant, were motile in liquid media. However, the Δ
cheA
mutant had impaired swarming and the Δ
cheY
and Δ
cheYA
mutants were unable to swarm on soft agar plates, suggesting that
cheY
and
cheA
genes encode proteins involved in chemotaxis. The Δ
flaA
, Δ
cheY
, Δ
cheA
, and Δ
cheYA
mutants (grown at 24°C) showed reduced association with and invasion of Caco-2 cells compared to the wild-type strain. However, spleens from intragastrically infected BALB/c and C57BL/6 mice showed larger and similar numbers of the Δ
flaA
and Δ
cheYA
mutants, respectively, compared to the wild-type controls. Such a discrepancy could be explained by the fact that tumor necrosis factor receptor p55 deficient mice showed dramatically exacerbated susceptibility to the wild-type but unchanged or only slightly increased levels of the Δ
flaA
or Δ
cheYA
mutant. In summary, we show that listerial
flaA. cheY
, and
cheA
gene products facilitate the initial contact with epithelial cells and contribute to effective invasion but that
flaA
could also be involved in the triggering of immune responses.
Lipopolysaccharide Protects Primary B Lymphocytes from Apoptosis by Preventing Mitochondrial Dysfunction and Bax Translocation to Mitochondria
Authors: Souvannavong Vongthip , Lemaire Christophe , Chaby Richard 
Published: May 2004

ABSTRACTMature B lymphocytes undergo apoptosis when they are cultured in the absence of survival factors. Gram-negative bacterial lipopolysaccharide (LPS) prevents this spontaneous apoptosis. This study aimed to better define the signaling pathway(s) involved in the antiapoptotic activity of this endotoxin. We report here that, in addition to its effects on spontaneous apoptosis, LPS protects B cells from apoptosis induced by the broad-spectrum protein kinase inhibitor staurosporine. LPS increased cell viability and concomitantly maintained the mitochondrial transmembrane potential (ΔΨm) and high glutathione levels. Moreover, LPS inhibited cytosolic cytochromecrelease and decreased caspase-9 activation. Unlike staurosporine, LPS induced the retention of Bax, a proapoptotic protein of the Bcl-2 family, in the cytosol by preventing its translocation to mitochondria. These results suggest that Bax relocalization from the cytosol to the mitochondria is an important step of mature B-cell apoptosis and that the antiapoptotic activity of LPS occurs upstream of mitochondrial events.
Enhancement of Anthrax Lethal Toxin Cytotoxicity: a Subset of Monoclonal Antibodies against Protective Antigen Increases Lethal Toxin-Mediated Killing of Murine Macrophages
Authors: Mohamed Nehal , Li Juan , Ferreira Claudia S. , Little Stephen F. , Friedlander Arthur M. , Spitalny George L. , Casey Leslie S. 
Published: May 2004

ABSTRACTWe investigated the ability of using monoclonal antibodies (MAbs) against anthrax protective antigen (PA), an anthrax exotoxin component, to modulate exotoxin cytotoxic activity on target macrophage cell lines. Anthrax PA plays a critical role in the pathogenesis ofBacillus anthracisinfection. PA is the cell-binding component of the two anthrax exotoxins: lethal toxin (LeTx) and edema toxin. Several MAbs that bind the PA component of LeTx are known to neutralize LeTx-mediated killing of target macrophages. Here we describe for the first time an overlooked population of anti-PA MAbs that, in contrast, function to increase the potency of LeTx against murine macrophage cell lines. The results support a possible mechanism of enhancement: binding of MAb to PA on the macrophage cell surface stabilizes the PA by interaction of MAb with macrophage Fcγ receptors. This results in an increase in the amount of PA bound to the cell surface, which in turn leads to an enhancement in cell killing, most likely due to increased internalization of LF. Blocking of PA-receptor binding eliminates enhancement by MAb, demonstrating the importance of this step for the observed enhancement. The additional significance of these results is that, at least in mice, immunization with PA appears to elicit a poly-clonal response that has a significant prevalence of MAbs that enhance LeTx-mediated killing in macrophages.
The LetE Protein Enhances Expression of Multiple LetA/LetS-Dependent Transmission Traits by
Legionella pneumophila
Authors: Bachman Michael A. , Swanson Michele S. 
Published: May 2004

ABSTRACT

Legionella pneumophila
colonizes freshwater amoebae and can also replicate within alveolar macrophages. When their nutrient supply is exhausted, replicating bacteria become cytotoxic, motile, and infectious, which is thought to promote transmission to a new amoeba. The differentiation of
L. pneumophila
is coordinated by the sigma factors RpoS and FliA and the two-component regulator LetA/LetS and is enhanced by the
letE
locus. Here we demonstrate that
letE
promotes motility by increasing expression of the flagellin gene
flaA
but has little impact on the transcription of
fliA
, the flagellar sigma factor gene. In addition to promoting motility,
letE
induces the characteristic shape, pigment, and heat resistance of stationary-phase
L. pneumophila
. To gain insight into how
letE
promotes the expression of the transmission phenotype, we designed molecular genetic experiments to discriminate between the following three models:
letE
mutations are polar on
milX
;
letE
encodes a small novel protein; or, by analogy to
csrB
,
letE
encodes a regulatory RNA that sequesters CsrA to relieve repression. We report that
letE
encodes an activator protein, as it does not complement an
Escherichia coli csrB
mutant, it directs the synthesis of an ∼12-kDa polypeptide, and a
letE
nonsense mutation eliminates function. A monocistronic
letE
RNA is abundant during the exponential phase, and its decay during the stationary phase requires RpoS and LetA/LetS. We also discuss how the LetE protein may interact with LetA/LetS and CsrA to enhance
L. pneumophila
differentiation to a transmissible form.
Cystathionine β-Lyase Is Important for Virulence ofSalmonella entericaSerovar Typhimurium
Authors: Ejim Linda J. , D'Costa Vanessa M. , Elowe Nadine H. , Loredo-Osti J. Concepción , Malo Danielle , Wright Gerard D. 
Published: May 2004

ABSTRACTThe biosynthesis of methionine in bacteria requires the mobilization of sulfur from Cys by the formation and degradation of cystathionine. Cystathionine β-lyase, encoded bymetCin bacteria andSTR3inSchizosaccharomyces pombe, catalyzes the breakdown of cystathionine to homocysteine, the penultimate step in methionine biosynthesis. This enzyme has been suggested to be the target for pyridinamine antimicrobial agents. We have demonstrated, by using purified enzymes from bacteria and yeast, that cystathionine β-lyase is not the likely target of these agents. Nonetheless, an insertional inactivation ofmetCinSalmonella entericaserovar Typhimurium resulted in the attenuation of virulence in a mouse model of systemic infection. This result confirms a previous chemical validation of the Met biosynthetic pathway as a target for the development of antibacterial agents and demonstrates that cystathionine β-lyase is important for bacterial virulence.