bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modulation of the Lung Inflammatory Response to Serotype 8 Pneumococcal Infection by a Human Immunoglobulin M Monoclonal Antibody to Serotype 8 Capsular Polysaccharide
Authors: Burns Tamika , Abadi Maria , Pirofski Liise-anne 
Published: July 2005

ABSTRACTThe human monoclonal antibody to serotype 8 pneumococcal capsular polysaccharide D11 [immunoglobulin M(κ)] protects wild-type and complement component 4 knockout (C4 KO) mice against lethal intratracheal challenge with serotype 8 pneumococcus, but it does not promote polymorphonuclear leukocyte (PMN)-mediated pneumococcal killing in vitro. In this study, we investigated the effect of D11 on the blood and lung bacterial burdens and the serum and lung expression of inflammatory chemokines and cytokines in an intratracheal challenge model with serotype 8 pneumococcus in C4 KO mice. Pneumococcus was not detected in the blood of D11-treated mice, whereas control mice had high-grade bacteremia with >107CFU. Control mice had a >5-log increase in lung CFU and D11-treated mice manifested a nearly 3-log increase in lung CFU compared to the original inoculum 24 h after infection. Serum and lung levels of soluble macrophage inflammatory protein 2 (MIP-2) and interleulin-6 (IL-6) as measured by an enzyme-linked immunosorbent assay were lower in D11-treated mice than in control mice 24 h after infection. Real-time PCR was performed to examine lung mRNA chemokine and cytokine expression. The results showed that D11-treated mice had significantly less gamma interferon, MIP-2, IL-12, monocyte chemoattractant protein 1/JE, and tumor necrosis factor alpha expression than control mice 24 h after infection. Histopathology and immunohistochemical staining of lung tissues revealed that D11-treated mice had less inflammation, fewer PMNs, and less myeloperoxidase staining than control mice 24 h after infection. These findings suggest that the efficacy of certain serotype-specific antibodies against pneumococcal pneumonia could be associated with modulation of the lung inflammatory response and a reduction in host damage.
Stimulation of gp91 Phagocytic Oxidase and Reactive Oxygen Species in Neutrophils by an AvirulentSalmonella entericaSerovar Infantis Strain Protects Gnotobiotic Piglets from Lethal Challenge with Serovar Typhimurium Strain F98 without Inducing Intestinal Pathology
Authors: Foster Neil , Hulme Scott , Lovell Margaret , Reed Katharine , Barrow Paul 
Published: July 2005

ABSTRACTPreinoculation of susceptible 5-day-old gnotobiotic piglets withSalmonella entericaserovar Infantis strain 1326/28Φrstimulates neutrophil migration into the intestine, which rapidly protects the pigs against a subsequent (normally lethal) challenge withS. entericaserovar Typhimurium strain F98. Here we show that inoculation with either 1326/28Φror F98 activated reactive oxygen species (ROS) in neutrophils via NADPH pathways in vivo and in vitro and that the survival of bothSalmonellastrains was increased if neutrophils were cocultured with the ROS inhibitorN-acetylcysteine (captopril). Neither F98 nor 1326/28Φrsignificantly increased reactive nitrogen species (RNS) levels in neutrophils isolated from uninfected pigs. Our results indicate the following: (i) rapid protection of highly susceptible gnotobiotic piglets against F98-induced gastroenteritis by preinoculation with 1326/28Φris likely to be due to stimulation of ROS-producing neutrophils in the intestinal epithelium prior to challenge with the lethal strain; (ii) pathological lesions of the intestine during severe gastroenteritis are not necessarily induced by neutrophil migration per se; and (iii) if neutrophil migration into the intestine is responsible for pathology, then neither increased production of ROS or RNS (in pigs inoculated with the lethal strain) nor reduced production (in protected pigs in which pathological lesions are ameliorated by preinoculation with 1326/28Φr) can account for this phenomenon.
Aspergillus
Cyclooxygenase-Like Enzymes Are Associated with Prostaglandin Production and Virulence
Authors: Tsitsigiannis Dimitrios I. , Bok Jin-Woo , Andes David , Nielsen Kristian Fog , Frisvad Jens C. , Keller Nancy P. 
Published: July 2005

ABSTRACT

Oxylipins comprise a family of oxygenated fatty acid-derived signaling molecules that initiate critical biological activities in animals, plants, and fungi. Mammalian oxylipins, including the prostaglandins (PGs), mediate many immune and inflammation responses in animals. PG production by pathogenic microbes is theorized to play a role in pathogenesis. We have genetically characterized three
Aspergillus
genes,
ppoA
,
ppoB
, and
ppoC
, encoding fatty acid oxygenases similar in sequence to specific mammalian prostaglandin synthases, the cyclooxygenases. Enzyme-linked immunosorbent assay analysis showed that production of PG species is decreased in both
Aspergillus nidulans
and
A. fumigatus ppo
mutants, implicating Ppo activity in generating PGs. The
A. fumigatus
triple-
ppo
-silenced mutant was hypervirulent in the invasive pulmonary aspergillosis murine model system and showed increased tolerance to H
2
O
2
stress relative to that of the wild type. We propose that Ppo products, PG, and/or other oxylipins may serve as activators of mammalian immune responses contributing to enhanced resistance to opportunistic fungi and as factors that modulate fungal development contributing to resistance to host defenses.
Degradation ofChlamydia pneumoniaeby Peripheral Blood Monocytic Cells
Authors: Wolf Katerina , Fischer Elizabeth , Hackstadt Ted 
Published: July 2005

ABSTRACTChlamydia pneumoniaeis a common human respiratory pathogen that has been associated with a variety of chronic diseases, including atherosclerosis. The role of this organism in the pathogenesis of atherosclerosis remains unknown. A key question is howC. pneumoniaeis transferred from the site of primary infection to a developing atherosclerotic plaque. It has been suggested that circulating monocytes could be vehicles for dissemination ofC. pneumoniaesince the organism has been detected in peripheral blood monocytic cells (PBMCs). In this study we focused on survival ofC. pneumoniaewithin PBMCs isolated from the blood of healthy human donors. We found thatC. pneumoniaedoes not grow and multiply in cultured primary monocytes. InC. pneumoniae-infected monocyte-derived macrophages, growth of the organism was very limited, and the majority of the bacteria were eradicated. We also found that the destruction ofC. pneumoniaewithin infected macrophages resulted in a gradual diminution of chlamydial antigens, although some of these antigens could be detected for days after the initial infection. The detected antigens present in infected monocytes and monocyte-derived macrophages represented neither chlamydial inclusions nor intact organisms. The use of {N-[7-(4-nitrobenzo-2-oxa-1,3-diazole)]}-6-aminocaproyl-d-erythro-sphingosine as a vital stain for chlamydiae proved to be a sensitive method for identifying rareC. pneumoniaeinclusions and was useful in the detection of even aberrant developmental forms.
Virulence of the Fungal Pathogen
Candida albicans
Requires the Five Isoforms of Protein Mannosyltransferases
Authors: Rouabhia Mahmoud , Schaller Martin , Corbucci Cristina , Vecchiarelli Anna , Prill Stephan K.-H. , Giasson Luc , Ernst Joachim F. 
Published: July 2005

ABSTRACT

The
PMT
gene family in
Candida albicans
encodes five isoforms of protein mannosyltransferases (Pmt proteins Pmt1p, Pmt2p, Pmt4p, Pmt5p, and Pmt6p) that initiate O mannosylation of secretory proteins. We compared virulence characteristics of
pmt
mutants in two complex, three-dimensional models of localized candidiasis, using reconstituted human epithelium (RHE) and engineered human oral mucosa (EHOM); in addition, mutants were tested in a mouse model of hematogenously disseminated candidiasis (HDC). All
pmt
mutants showed attenuated virulence in the HDC model and at least one model of localized candidiasis. The
pmt5
mutant, which lacks in vitro growth phenotypes, was less virulent in the EHOM and HDC assays but had no consistent phenotype in the RHE assay. In contrast, the
pmt4
and
pmt6
mutants were less virulent in the RHE and HDC assays but not in the EHOM assay. The results stress the contribution of all Pmt isoforms to the virulence of
C. albicans
and suggest that the importance of individual Pmt isoforms may differ in specific host niches. We propose that Pmt proteins may be suitable targets for future novel classes of antifungal agents.
Role for Nucleotide Excision Repair in Virulence of
Mycobacterium tuberculosis
Authors: Darwin K. Heran , Nathan Carl F. 
Published: July 2005

ABSTRACT

Mutations in
Mycobacterium tuberculosis uvrB
result in severe sensitivity to acidified nitrite, a source of nitric oxide (6). In this study, we show that a
uvrB
mutant is exquisitely sensitive to UV light but not to several sources of reactive oxygen species in vitro. Furthermore, a
uvrB
mutant was attenuated in mice as judged by an extension of life span. Attenuation in mice was partially reversed by genetic inactivation of nitric oxide synthase 2 (iNOS) and almost completely reversed in mice lacking both iNOS and phagocyte oxidase. Thus, a gene predicted to encode a key element of DNA repair is required for resistance of
M. tuberculosis
to both reactive nitrogen and reactive oxygen species in mice.
Invasive Phenotype ofCandida albicansAffects the Host Proinflammatory Response to Infection
Authors: Villar C. C. , Kashleva H. , Mitchell A. P. , Dongari-Bagtzoglou A. 
Published: July 2005

ABSTRACTCandida albicansis a major opportunistic pathogen in immunocompromised patients. Production of proinflammatory cytokines by host cells in response toC. albicansplays a critical role in the activation of immune cells and final clearance of the organism. Invasion of host cells and tissues is considered one of the virulence attributes of this organism. The purpose of this study was to investigate whether the ability ofC. albicansto invade host cells and tissues affects the proinflammatory cytokine responses by epithelial and endothelial cells. In this study we used the invasion-deficientRIM101gene knockout strain DAY25, the highly invasive strain SC5314, and highly invasiveRIM101-complemented strain DAY44 to compare the proinflammatory cytokine responses by oral epithelial or endothelial cells. Using a high-throughput approach, we found both qualitative and quantitative differences in the overall inflammatory responses toC. albicansstrains with different invasive potentials. Overall, the highly invasive strains triggered higher levels of proinflammatory cytokines in host cells than the invasion-deficient mutant triggered. Significant differences compared to the attenuated mutant were noted in interleukin-1α (IL-1α), IL-6, IL-8, and tumor necrosis factor alpha in epithelial cells and in IL-6, growth-related oncogene, IL-8, monocyte chemoattractant protein 1 (MCP-1), MCP-2, and granulocyte colony-stimulating factor in endothelial cells. Our results indicate that invasion of host cells and tissues byC. albicansenhances the host proinflammatory response to infection.
Heparin Stimulates
Staphylococcus aureus
Biofilm Formation
Authors: Shanks Robert M. Q. , Donegan Niles P. , Graber Martha L. , Buckingham Sarah E. , Zegans Michael E. , Cheung Ambrose L. , O'Toole George A. 
Published: July 2005

ABSTRACT

Heparin, known for its anticoagulant activity, is commonly used in catheter locks.
Staphylococcus aureus
, a versatile human and animal pathogen, is commonly associated with catheter-related bloodstream infections and has evolved a number of mechanisms through which it adheres to biotic and abiotic surfaces. We demonstrate that heparin increased biofilm formation by several
S. aureus
strains. Surface coverage and the kinetics of biofilm formation were stimulated, but primary attachment to the surface was not affected. Heparin increased
S. aureus
cell-cell interactions in a protein synthesis-dependent manner. The addition of heparin rescued biofilm formation of
hla
,
ica
, and
sarA
mutants. Our data further suggest that heparin stimulation of biofilm formation occurs neither through an increase in
sigB
activity nor through an increase in polysaccharide intracellular adhesin levels. These finding suggests that heparin stimulates
S. aureus
biofilm formation via a novel pathway.
Human Antibody against Shiga Toxin 2 Administered to Piglets after the Onset of Diarrhea Due to
Escherichia coli
O157:H7 Prevents Fatal Systemic Complications
Authors: Sheoran Abhineet S. , Chapman-Bonofiglio Susan , Harvey Barrett R. , Mukherjee Jean , Georgiou George , Donohue-Rolfe Arthur , Tzipori Saul 
Published: July 2005

ABSTRACT

Infection of children with Shiga toxin (Stx)-producing
Escherichia coli
(STEC) can lead to hemolytic-uremic syndrome (HUS) in 5 to 10% of patients. Stx2, one of two toxins liberated by the bacterium, is directly linked with HUS. We have previously shown that Stx-specific human monoclonal antibodies protect STEC-infected animals from fatal systemic complications. The present study defines the protective antibody dose in relation to the time of treatment after the onset of diarrhea in infected gnotobiotic piglets. Using the mouse toxicity model, we selected 5C12, an antibody specific for the A subunit, as the most effective Stx2 antibody for further characterization in the piglet model in which piglets developed diarrhea 16 to 40 h after bacterial challenge, followed by fatal neurological symptoms at 48 to 96 h. Seven groups of piglets received doses of 5C12 ranging from 6.0 mg/kg to 0.05 mg/kg of body weight, administered parenterally 48 h after bacterial challenge. The minimum fully protective antibody dose was 0.4 mg/kg, and the corresponding serum antibody concentration in these piglets was 0.7 μg (±0.5)/ml, measured 7 to 14 days after administration. Of 40 infected animals which received Stx2 antibody treatment of ≥0.4 mg/kg, 34 (85%) survived, while only 1 (2.5%) of 39 placebo-treated animals survived. We conclude that the administration of the Stx2-specific antibody was protective against fatal systemic complications even when it was administered well after the onset of diarrhea. These findings suggest that children treated with this antibody, even after the onset of bloody diarrhea, may be equally protected against the risk of developing HUS.
Deletion of the Anaerobic Regulator HlyX Causes Reduced Colonization and Persistence ofActinobacillus pleuropneumoniaein the Porcine Respiratory Tract
Authors: Baltes Nina , N′diaye Mohamed , Jacobsen Ilse D. , Maas Alexander , Buettner Falk F. R. , Gerlach Gerald-F. 
Published: July 2005

ABSTRACTActinobacillus pleuropneumoniae, the etiological agent of porcine pleuropneumonia, is able to persist on respiratory epithelia, in tonsils, and in the anaerobic environment of encapsulated lung sequesters. We have demonstrated previously that putative HlyX-regulated genes, coding for dimethyl sulfoxide (DMSO) reductase and aspartate ammonia lyase, are upregulated during infection and that deletions in these genes result in attenuation of the organism. The study presented here investigates the role of HlyX, the fumarate nitrate reductase regulator (FNR) homologue ofA. pleuropneumoniae. By constructing an isogenicA. pleuropneumoniae hlyXmutant, the HlyX protein is shown to be responsible for upregulated expression of both DMSO reductase and aspartate ammonia lyase (AspA) under anaerobic conditions. In a challenge experiment theA. pleuropneumoniae hlyXmutant is shown to be highly attenuated, unable to persist in healthy lung epithelium and tonsils, and impaired in survival inside sequestered lung tissue. Further, using anA. pleuropneumoniaestrain carrying theluxABgenes as transcriptional fusion toaspAon the chromosome, the airway antioxidant glutathione was identified as one factor potentially responsible for inducing HlyX-dependent gene expression ofA. pleuropneumoniaein epithelial lining fluid.
Chlamydia pneumoniae
Uses the Mannose 6-Phosphate/Insulin-Like Growth Factor 2 Receptor for Infection of Endothelial Cells
Authors: Puolakkainen Mirja , Kuo Cho-Chou , Campbell Lee Ann 
Published: July 2005

ABSTRACT

Several mechanisms for attachment and entry of
Chlamydia
have been proposed. We previously determined that the major outer membrane protein of
Chlamydia trachomatis
is glycosylated with a high-mannose oligosaccharide, and a similar structure inhibited the attachment and infectivity of
C. trachomatis
in epithelial cells. Because insulin-like growth factor 2 (IGF2) was shown to enhance the infectivity of
Chlamydia pneumoniae
but not
C. trachomatis
in endothelial cells, a hapten inhibition assay was used to analyze whether the mannose 6-phosphate (M6P)/IGF2 receptor that also binds M6P could be involved in infection of endothelial cells (HMEC-1) by
Chlamydia
. M6P and mannose 6-phosphate-poly[
N
-(2-hydroxyethyl)-acrylamide] (M6P-PAA) inhibited the infectivity of
C. pneumonia
e AR-39, but not
C. trachomatis
serovar UW5 or L2, while mannan inhibited the growth of
C. trachomatis
, but not
C. pneumoniae
. Using metabolically labeled organisms incubated with cells at 4°C (organisms attach but do not enter) or at 37°C (organisms attach and are internalized), M6P-PAA was shown to inhibit attachment and internalization of
C. pneumoniae
in endothelial cells but did not inhibit attachment or internalization of
C. trachomatis
serovar E or L2. These findings indicate that
C. pneumoniae
can utilize the M6P/IGF2 receptor and that the use of this receptor for attachment and entry differs between
C. pneumoniae
and
C. trachomatis
.
Toll-Like Receptor 4 Mediates Tolerance in Macrophages Stimulated withToxoplasma gondii-Derived Heat Shock Protein 70
Authors: Mun Hye-Seong , Aosai Fumie , Norose Kazumi , Piao Lian-Xun , Fang Hao , Akira Shizuo , Yano Akihiko 
Published: July 2005

ABSTRACTPeritoneal macrophages (PMs) from toll-like receptor 4 (TLR4)-deficient and wild-type (WT) mice were responsive to recombinantToxoplasma gondii-derived heat shock protein 70 (rTgHSP70) and natural TgHSP70 (nTgHSP70) in NO release, but those from TLR2-, myeloid differentiation factor 88 (MyD88)-, and interleukin-1R-associated kinase 4 (IRAK4)-deficient mice were not. Polymyxin B did not inhibit PM activation by TgHSP70 and nTgHSP70 from WT and TLR4-deficient mice, while it inhibited PM activation by lipopolysaccharide. Pretreatment of PMs from WT but not from TLR4-deficient mice with rTgHSP70 resulted in suppression of NO release on restimulation with rTgHSP70. Similarly, pretreatment of PMs from WT but not TLR4-deficient mice with nTgHSP70 resulted in suppression of NO release on restimulation with nTgHSP70. Polymyxin B did not inhibit rTgHSP70- and nTgHSP70-induced tolerance of PMs from TLR4-deficient mice. Furthermore, PMs from WT mice increased suppressor of cytokine-signaling-1 (SOCS-1) expression after restimulation with rTgHSP70, while those from TLR4-deficient mice did not. Phosphorylation of JNK and I-κBα occurred in rTgHSP70-induced tolerance of PMs from TLR4-deficient mice, but not in that from WT mice. These data indicated that TgHSP70 signaling mechanisms were mediated by TLR2, MyD88, and IRAK4, but not by TLR4. On the other hand, signaling of TgHSP70-induced tolerance was mediated by TLR4, and the expression of SOCS-1 suppressed the TLR2 signaling pathway.
Analysis of Cell Type-Specific Responses Mediated by the Type IV Secretion System of
Helicobacter pylori
Authors: Bauer Bianca , Moese Stefan , Bartfeld Sina , Meyer Thomas F. , Selbach Matthias 
Published: July 2005

ABSTRACT

Helicobacter pylori
persistently infects the human stomach and can cause gastritis, gastric ulceration, and gastric cancer. The type IV secretion system (TFSS) of virulent
H. pylori
strains translocates the CagA protein, inducing the dephosphorylation of host cell proteins and leading to changes in the morphology or shape of AGS gastric epithelial cells. Furthermore, the TFSS is involved in the induction of proinflammatory cytokines. While the
H. pylori
genes required for TFSS function have been investigated systematically, little is known about possible host cell factors involved. We infected 19 different mammalian cell lines individually with
H. pylori
and analyzed CagA translocation, dephosphorylation of host cell proteins, chemokine secretion (interleukin-8 and macrophage inflammatory protein 2), and changes in cellular phenotypes. Our results demonstrate that not only bacterial but also host cell factors determine the cellular response to infection. The identification of such unknown host cell factors will add to our understanding of host-pathogen interactions and might help in the development of new therapeutic strategies.
Illustration of Pneumococcal Polysaccharide Capsule during Adherence and Invasion of Epithelial Cells
Authors: Hammerschmidt Sven , Wolff Sonja , Hocke Andreas , Rosseau Simone , Müller Ellruth , Rohde Manfred 
Published: July 2005

ABSTRACT

The capsular polysaccharide of
Streptococcus pneumoniae
represents an important virulence factor and protects against phagocytosis. In this study the amount of capsular polysaccharide present on the bacterial surface during the infection process was illustrated by electron microscopic studies. After infection of A549 cells (type II pneumocytes) and HEp-2 epithelial cells a modified fixation method was used that allowed visualization of the state of capsule expression. This modified fixation procedure did not require the use of capsule-specific antibodies. Visualization of pneumococci in intimate contact and invading cells demonstrated that pneumococci were devoid of capsular polysaccharide. Pneumococci not in contact with the cells did not show alterations in capsular polysaccharide. After infection of the cells, invasive pneumococci of different strains and serotypes were recovered. Single colonies of these recovered pneumococci exhibited an up-to-10
5
-fold-enhanced capacity to adhere and an up-to-10
4
-fold-enhanced capacity to invade epithelial cells. Electron microscopic studies using a lysine-ruthenium red (LRR) fixation procedure or cryo-field emission scanning electron microscopy revealed a reduction in capsular material, as determined in detail for a serotype 3 pneumococcal strain. The amount of polysaccharide in the serotype 3 capsule was also determined after intranasal infection of mice. This study illustrates for the first time the phenotypic variation of the polysaccharide capsule in the initial phase of pneumococcal infections. The modified LRR fixation allowed monitoring of the state of capsule expression of pathogens during the infectious process.
Exposure to Rumen Protozoa Leads to Enhancement of Pathogenicity of and Invasion by Multiple-Antibiotic-ResistantSalmonella entericaBearing SGI1
Authors: Rasmussen Mark A. , Carlson Steve A. , Franklin Sharon K. , McCuddin Zoe P. , Wu Max T. , Sharma Vijay K. 
Published: July 2005

ABSTRACTMultiple-antibiotic-resistantSalmonella entericaserotype Typhimurium is a food-borne pathogen that has been purported to be more virulent than antibiotic-sensitive counterparts. The paradigm for this multiresistant/hyperpathogenic phenotype isSalmonella entericaserotype Typhimurium phage type DT104 (DT104). The basis for the multiresistance in DT104 is related to an integron structure designated SGI1, but factors underlying hyperpathogenicity have not been completely identified. Since protozoa have been implicated in the alteration of virulence inLegionellaandMycobacteriumspp., we attempted to assess the possibility that protozoa may contribute to the putative hypervirulence of DT104. Our study reveals that DT104 can be more invasive, as determined by a tissue culture invasion assay, after surviving within protozoa originating from the bovine rumen. The enhancement of invasion was correlated with hypervirulence in a bovine infection model in which we observed a more rapid progression of disease and a greater recovery rate for the pathogen. Fewer DT104 cells were recovered from tissues of infected animals when protozoa were lysed by preinfection chemical defaunation of the bovine or ovine rumen. The protozoan-mediated hypervirulence phenotype was observed only in DT104 and otherSalmonellastrains, including serovars Agona and Infantis, possessing SGI1.