bluuebunny/crossref_metadata_2025_split huggingface dataset:
Altered Gene Expression inStaphylococcus aureusupon Interaction with Human Endothelial Cells
Authors: Vriesema Aldwin J. M. , Beekhuizen Henry , Hamdi Mohamed , Soufan Alexandre , Lammers Aart , Willekens Ben , Bakker Onno , Welten Angelique G. A. , Veltrop Marcel H. A. M. , van de Gevel Joke S. , Dankert Jacob , Zaat Sebastian A. J. 
Published: July 2002

ABSTRACTStaphylococcus aureusis isolated from a substantial number of patients with infective endocarditis who are not known to have predisposing heart abnormalities. It has been suggested that the infection is initiated by the direct binding ofS. aureusto human vascular endothelium. To determine the mutual response of the endothelial cells and the bacteria, we studied the interaction betweenS. aureusand human vascular endothelium. Scanning electron microscopic analyses showed that binding ofS. aureusto human umbilical vein endothelial cells (HUVEC) mainly occurred via thread-like protrusions extending from the cell surface. Bound bacteria appeared to be internalized via retraction of the protrusions into newly formed invaginations of the endothelial cell surface. The growth phase ofS. aureushad a major impact on the interaction with HUVEC. Logarithmically growing bacteria showed increased binding to, and were more readily internalized by, HUVEC compared to stationary-phase bacteria. To assess the bacterial response to the cellular environment, an expression library ofS. aureuswas used to identify genes whose expression was induced after 4 h of exposure to HUVEC. The identified genes could be divided into different categories based on the functions of the encoded proteins (transport, catabolism, biosynthesis, and DNA repair). Further analyses of five of theS. aureustransposon clones showed that HUVEC as well as human serum are stimuli for triggering gene expression inS. aureus.
Inactivation of the
srtA
Gene in
Streptococcus gordonii
Inhibits Cell Wall Anchoring of Surface Proteins and Decreases In Vitro and In Vivo Adhesion
Authors: Bolken Tové C. , Franke Christine A. , Jones Kevin F. , Zeller Gloria O. , Jones C. Hal , Dutton Emma K. , Hruby Dennis E. 
Published: July 2002

ABSTRACT

The
srtA
gene product, SrtA, has been shown to be required for cell wall anchoring of protein A as well as virulence in the pathogenic bacterium
Staphylococcus aureus
. There are five major mechanisms for displaying proteins at the surface of gram-positive bacteria (P. Cossart and R. Jonquieres, Proc. Natl. Acad. Sci. USA 97:5013–5015, 2000). However, since many of the known surface proteins of gram-positive bacteria are believed to be exported and anchored via the sortase pathway, it was of interest to determine if
srtA
plays a similar role in other gram-positive bacteria. To that end, the
srtA
gene in the human oral commensal organism
Streptococcus gordonii
was insertionally inactivated. The
srtA
mutant
S. gordonii
exhibited a marked reduction in quantity of a specific anchored surface protein. Furthermore, the
srtA
mutant had reduced binding to immobilized human fibronectin and had a decreased ability to colonize the oral mucosa of mice. Taken together, these results suggest that the activity of SrtA plays an important role in the biology of nonpathogenic as well as pathogenic gram-positive cocci.
Cytokine Networking in Lungs of Immunocompetent Mice in Response to InhaledAspergillus fumigatus
Authors: Brieland Joan K. , Jackson Craig , Menzel Fred , Loebenberg David , Cacciapuoti Anthony , Halpern Judy , Hurst Stephen , Muchamuel Tony , Debets Reno , Kastelein Rob , Churakova Tatyana , Abrams John , Hare Roberta , O'Garra Anne 
Published: July 2002

ABSTRACTCytokine networking in the lung in response to inhaledAspergillus fumigatuswas assessed using a murine model of primary pulmonary aspergillosis in immunocompetent Crl:CF-1 mice. Inhalation of virulentA. fumigatus(6 × 106CFU) resulted in the induction of interleukin 18 (IL-18), tumor necrosis factor alpha (TNF-α), IL-12, and gamma interferon (IFN-γ) protein in bronchoalveolar lavage fluid and/or lung tissue. Induction of immunoreactive IL-18 preceded induction of TNF-α protein, which preceded induction of immunoreactive IL-12 and IFN-γ. Real-time reverse transcriptase (RT) PCR analysis of infected lung tissue demonstrated that induction of IL-18 protein also preceded induction of pulmonary TNF-α, IL-12, and IFN-γ mRNAs. Mice were subsequently treated with cytokine-specific neutralizing monoclonal antibodies (MAbs) to the IL-18 receptor (anti-IL-18R MAb), TNF-α (anti-TNF-α MAb), IL-12 (anti-IL-12 MAb), and/or IFN-γ (anti-IFN-γ MAb), and effects on intrapulmonary cytokine activity and growth ofA. fumigatuswere assessed in infected lung homogenates. Simultaneous neutralization of IL-12 and IL-18 resulted in decreased levels of immunoreactive TNF-α, while neutralization of IL-18, TNF-α, or IL-12 alone or of IL-18 and IL-12 together resulted in decreased levels of immunoreactive IFN-γ. Simultaneous neutralization of IL-12 and IL-18 or neutralization of TNF-α alone or in combination with IL-12, IL-18, or IFN-γ also resulted in a significant increase inA. fumigatusCFU in lung tissue. Taken together, these results demonstrate that endogenous IL-18, IL-12, and TNF-α, through their modulatory effects on both intrapulmonary cytokine activity and growth ofA. fumigatus, play key roles in host defense against primary pulmonary aspergillosis.
Helicobacter pylori
Resists Phagocytosis by Macrophages: Quantitative Assessment by Confocal Microscopy and Fluorescence-Activated Cell Sorting
Authors: Ramarao Nalini , Meyer Thomas F. 
Published: July 2002

ABSTRACT

Helicobacter pylori
infection of the stomach epithelium is characterized by an infiltration of polymorphonuclear and mononuclear cells. These immune cells contribute to mucosal damage which may eventually lead to gastritis, peptic ulcer, gastric cancer, and/or MALT-associated gastric lymphoma. Here we show that
H. pylori
inhibits its own uptake, as well as in
trans
the phagocytosis of
Neisseria gonorrhoeae
, by human and murine macrophages. This antiphagocytic activity is dependent on the presence of the
cag
pathogenicity island in the
H. pylori
genome. We demonstrate that
H. pylori
also expresses its antiphagocytic activity towards the myelomonocytic cell line JOSKM, thus providing a potent model for the study of the interaction between
H. pylori
and phagocytes. Our data were obtained using laser confocal microscopy and flow cytometry after quenching the fluorescence of labeled extracellular bacteria. The antiphagocytic activity of
H. pylori
may explain the persistence of
H. pylori
and its pathological consequences. The use of cell lines and flow cytometry will hopefully facilitate progress in our understanding of the immune escape of these persistent bacteria.
Arg-Gingipain A DNA Vaccine Induces Protective Immunity against Infection by
Porphyromonas gingivalis
in a Murine Model
Authors: Yonezawa Hideo , Ishihara Kazuyuki , Okuda Katsuji 
Published: July 2002

ABSTRACT

Arginine-specific cysteine proteinases (RgpA and RgpB) produced by the periodontal pathogen
Porphyromonas gingivalis
are suspected virulence factors and are involved in interrupting host defense mechanisms as well as in penetrating and destroying periodontal connective tissues. To induce a protective immune response against
P. gingivalis
, we constructed an
rgpA
DNA vaccine. BALB/c mice were immunized intradermally by Gene Gun with plasmid DNA carrying
rgpA
. Antibody responses against
P. gingivalis
were determined by an enzyme-linked immunosorbent assay. The
rgpA
DNA vaccine induced high levels of serum antibodies against
P. gingivalis
. Sera from the
rgpA
DNA vaccine-immunized mice diminished the proteolytic activity of RgpA and RgpB and inhibited the binding of
P. gingivalis
to a type I collagen sponge. Moreover, the sera effectively reduced the hemagglutination of
P. gingivalis
, indicating that the hemagglutinin activity of the organism is associated with RgpA. We found with a murine abscess model that mice immunized with the
rgpA
DNA vaccine were resistant to an invasive
P. gingivalis
W50 challenge. These results suggest that the
rgpA
DNA vaccine induced specific antibodies against the enzyme and that this vaccine could confer protective immunity against
P. gingivalis
infection.
Exacerbation ofAcanthamoebaKeratitis in Animals Treated with Anti-Macrophage Inflammatory Protein 2 or Antineutrophil Antibodies
Authors: Hurt Michael , Apte Sherine , Leher Henry , Howard Kevin , Niederkorn Jerry , Alizadeh Hassan 
Published: July 2002

ABSTRACTNeutrophils are thought to be involved in many infectious diseases and have been found in high numbers in the corneas of patients withAcanthamoebakeratitis. Using a Chinese hamster model of keratitis, conjunctival neutrophil migration was manipulated to determine the importance of neutrophils in this disease. Inhibition of neutrophil recruitment was achieved by subconjunctival injection with an antibody against macrophage inflammatory protein 2 (MIP-2), a powerful chemotactic factor for neutrophils which is secreted by the cornea. In other experiments, neutrophils were depleted by intraperitoneal injection of anti-Chinese hamster neutrophil antibody. The inhibition of neutrophils to the cornea resulted in an earlier onset and more severe infection compared to controls. Anti-MIP-2 antibody treatment produced an almost 35% reduction of myeloperoxidase activity in the cornea 6 days postinfection, while levels of endogenous MIP-2 secretion increased significantly. Recruitment of neutrophils into the cornea via intrastromal injections of recombinant MIP-2 generated an initially intense inflammation that resulted in the rapid resolution of the corneal infection. The profound exacerbation ofAcanthamoebakeratitis seen when neutrophil migration was inhibited, combined with the rapid clearing of the disease in the presence of increased neutrophils, strongly suggests that neutrophils play an important role in combatingAcanthamoebainfections in the cornea.
Pneumolysin-Induced Complement Depletion during Experimental Pneumococcal Bacteremia
Authors: Alcantara Rosemarie B. , Preheim Laurel C. , Gentry-Nielsen Martha J. 
Published: July 2002

ABSTRACT

To quantify complement depletion by pneumolysin during
Streptococcus pneumoniae
bacteremia, cirrhotic and control rats were infected intravenously with one of three isogenic mutant strains of
S. pneumoniae
expressing different forms of pneumolysin. Outcome measures included clearance of the organisms from the bloodstream, alterations in 50% serum hemolytic complement (CH
50
) activity and complement C3 levels during infection, and serum opsonic capacity at 18 h postinfection. Cirrhotic rats had significantly lower CH
50
and C3 levels than control rats, both before and after infection. However, initial complement levels did not predict bacterial load after 18 h of infection. Changes in CH
50
and C3 levels over the 18-h period correlated with numbers of H+C+ but not H+C− or PLY− organisms in the bloodstream at 18 h postinfection. The sera of cirrhotic rats infected with the H+C+ strain had significantly decreased levels of C3 and showed significantly lower opsonizing activity for
S. pneumoniae
than sera from H+C+-infected control rats. These studies suggest that under limiting concentrations of complement, the expression of pneumolysin by pneumococci has a significant, negative effect on serum complement levels and reduces serum opsonic activity.
Relationship of Anti-Lewis x and Anti-Lewis y Antibodies in Serum Samples from Gastric Cancer and Chronic Gastritis Patients toHelicobacter pylori-Mediated Autoimmunity
Authors: Heneghan Michael A. , McCarthy Ciaran F. , Janulaityte Daiva , Moran Anthony P. 
Published: July 2002

ABSTRACTLewis (Le) antigens have been implicated in the pathogenesis of atrophic gastritis and gastric cancer in the setting ofHelicobacter pyloriinfection, andH. pylori-induced anti-Le antibodies have been described that cross-react with the gastric mucosa of both mice and humans. The aim of this study was to examine the presence of anti-Le antibodies in patients withH. pyloriinfection and gastric cancer and to examine the relationships between anti-Le antibody production, bacterial Le expression, gastric histopathology, and host Le erythrocyte phenotype. Anti-Le antibody production andH. pyloriLe expression were determined by enzyme-linked immunosorbent assay, erythrocyte Le phenotype was examined by agglutination assays, and histology was scored blindly. Significant levels of anti-Lexantibody (P< 0.0001, T = 76.4, DF = 5) and anti-Leyantibody (P< 0.0001, T = 73.05, DF = 5) were found in the sera of patients with gastric cancer and otherH. pylori-associated pathology compared withH. pylori-negative controls. Following incubation of patient sera with synthetic Le glycoconjugates, anti-Lexand -Leyautoantibody binding was abolished. The degree of the anti-Lexand -Leyantibody response was unrelated to the host Le phenotype but was significantly associated with the bacterial expression of Lex(r= 0.863,r2= 0.745,P< 0.0001) and Ley(r= 0.796,r2= 0.634,P< 0.0001), respectively. Collectively, these data suggest that anti-Le antibodies are present in most patients withH. pyloriinfection, including those with gastric cancer, that variability exists in the strength of the anti-Le response, and that this response is independent of the host Le phenotype but related to the bacterial Le phenotype.
Lymphocyte Adhesion toCandida albicans
Authors: Forsyth Christopher B. , Mathews Herbert L. 
Published: July 2002

ABSTRACTAdherence of lymphocytes to the fungus is the first step in the direct lymphocyte-mediated antifungal effect againstCandida albicans. In this study we identified macrophage-1 antigen (Mac-1) (CD11b/CD18, αM/β2) as the lymphocyte surface structure responsible for the adhesion of activated lymphocytes to the hyphal form of the fungus. Antibodies specific for epitopes of the α-subunit (CD11b) and the β2-subunit (CD18) of Mac-1 were shown to completely eliminate lymphocyte adhesion toC. albicanshyphae. Lymphocyte adhesion toC. albicanswas also inhibited significantly by known ligands of Mac-1, including the extracellular matrix proteins laminin and fibrinogen, as well as engineered peptides containing arginine-glycine-aspartic acid sequences and the disintegrin echistatin.N-Acetyl-d-glucosamine and β-glucan, which inhibit Mac-1-mediated adhesion to the yeast, blocked lymphocyte adhesion to hyphae. NIH 3T3 fibroblast transfectants expressing human CD11b/CD18 bound toC. albicans, and their binding was inhibited by antibodies specific for CD11b/CD18. Finally, antibodies specific for CD11b/CD18 effectively inhibited the capacity of activated lymphocytes to have an antifungal effect against hyphae. Our results clearly identify Mac-1 (CD11b/CD18) as the lymphocyte surface structure that mediates activated lymphocyte adhesion toC. albicansand the resultant antifungal effect of the lymphocytes.
The Yeast Model for Batten Disease: Mutations in
btn1
,
btn2
, and
hsp30
Alter pH Homeostasis
Authors: Chattopadhyay Subrata , Muzaffar Neda E. , Sherman Fred , Pearce David A. 
Published: July 2002

ABSTRACT

The
BTN1
gene product of the yeast
Saccharomyces cerevisiae
is 39% identical and 59% similar to human CLN3, which is associated with the neurodegenerative disorder Batten disease. Furthermore,
btn1
-Δ strains have an elevated activity of the plasma membrane H
+
-ATPase due to an abnormally high vacuolar acidity during the early phase of growth. Previously, DNA microarray analysis revealed that
btn1
-Δ strains compensate for the altered plasma membrane H
+
-ATPase activity and vacuolar pH by elevating the expression of the two genes
HSP30
and
BTN2
. We now show that deletion of either
HSP30
or
BTN2
in either
BTN1
+
or
btn1
-Δ strains does not alter vacuolar pH but does lead to an increased activity of the vacuolar H
+
-ATPase. Deletion of
BTN1
,
BTN2
, or
HSP30
does not alter cytosolic pH but diminishes pH buffering capacity and causes poor growth at low pH in a medium containing sorbic acid, a condition known to result in disturbed intracellular pH homeostasis. Btn2p was localized to the cytosol, suggesting a role in mediating pH homeostasis between the vacuole and plasma membrane H
+
-ATPase. Increased expression of
HSP30
and
BTN2
in
btn1
-Δ strains and diminished growth of
btn1
-Δ,
hsp30
-Δ, and
btn2
-Δ strains at low pH reinforce our view that altered pH homeostasis is the underlying cause of Batten disease.
CTXφ Infection of
Vibrio cholerae
Requires the
tolQRA
Gene Products
Authors: Heilpern Andrew J. , Waldor Matthew K. 
Published: July 2002

ABSTRACT

CTXφ is a lysogenic filamentous bacteriophage that encodes cholera toxin. Filamentous phages that infect
Escherichia coli
require both a pilus and the products of
tolQRA
in order to enter host cells. We have previously shown that toxin-coregulated pilus (TCP), a type IV pilus that is an essential
Vibrio cholerae
intestinal colonization factor, serves as a receptor for CTXφ. To test whether CTXφ also depends upon
tol
gene products to infect
V. cholerae
, we identified and inactivated the
V. cholerae tolQRAB
orthologues. The predicted amino acid sequences of
V. cholerae
TolQ, TolR, TolA, and TolB showed significant similarity to the corresponding
E. coli
sequences.
V. cholerae
strains with insertion mutations in
tolQ
,
tolR
, or
tolA
were reduced in their efficiency of CTXφ uptake by 4 orders of magnitude, whereas a strain with an insertion mutation in
tolB
showed no reduction in CTXφ entry. We could detect CTXφ infection of TCP
−
V. cholerae
, albeit at very low frequencies. However, strains with mutations in both
tcpA
and either
tolQ
,
tolR
, or
tolA
were completely resistant to CTXφ infection. Thus, CTXφ, like the
E. coli
filamentous phages, uses both a pilus and TolQRA to enter its host. This suggests that the pathway for filamentous phage entry into cells is conserved between host bacterial species.
The Autolytic Enzyme LytA of
Streptococcus pneumoniae
Is Not Responsible for Releasing Pneumolysin
Authors: Balachandran Priya , Hollingshead Susan K. , Paton James C. , Briles David E. 
Published: July 2002

ABSTRACT

It was previously proposed that autolysin's primary role in the virulence of pneumococci was to release pneumolysin to an extracellular location. This interpretation came into question when pneumolysin was observed to be released in significant amounts from some pneumococci during log-phase growth, because autolysis was not believed to occur at this time. We have reexamined this phenomenon in detail for one such strain, WU2. This study found that the extracellular release of pneumolysin from WU2 was not dependent on autolysin action. A mutant lacking autolysin showed the same pattern of pneumolysin release as the wild-type strain. Addition of mitomycin C to a growing WU2 culture did not induce lysis, indicating the absence of resident bacteriophages that could potentially harbor
lytA
-like genes. Furthermore, release of pneumolysin was unaltered by growth in 2% choline, a condition which is reported to inactivate autolysin, as well as most known pneumococcal phage lysins. Profiles of total proteins in the cytoplasm and in the supernatant media supported the hypothesis that release of pneumolysin is independent of pneumococcal lysis. Finally, under some infection conditions, mutations in pneumolysin and autolysin had different effects on virulence.
Identification of the UDP-MurNAc-Pentapeptide:
l
-Alanine Ligase for Synthesis of Branched Peptidoglycan Precursors in
Enterococcus faecalis
Authors: Bouhss Ahmed , Josseaume Nathalie , Allanic David , Crouvoisier Muriel , Gutmann Laurent , Mainardi Jean-Luc , Mengin-Lecreulx Dominique , van Heijenoort Jean , Arthur Michel 
Published: July 2002

ABSTRACT

Many species of gram-positive bacteria produce branched peptidoglycan precursors resulting from the transfer of various
l
-amino acids or glycine from amino acyl-tRNA to the ɛ-amino group of
l
-lysine. The UDP-MurNAc-pentapeptide:
l
-alanine ligase and alanyl-tRNA synthetase genes from
Enterococcus faecalis
were identified, cloned, and overexpressed in
Escherichia coli
. The purified enzymes were necessary and sufficient for tRNA-dependent addition of
l
-alanine to UDP-MurNAc-pentapeptide in vitro. The ligase belonged to the Fem family of proteins, which were initially identified genetically as factors essential for methicillin resistance in
Staphylococcus aureus
.
Membrane Interaction ofEscherichia coliHemolysin: Flotation and Insertion-Dependent Labeling by Phospholipid Vesicles
Authors: Hyland Caroline , Vuillard Laurent , Hughes Colin , Koronakis Vassilis 
Published: July 2002

ABSTRACTThe 1,024-amino-acid acylated hemolysin ofEscherichia colisubverts host cell functions and causes cell lysis. Both activities require insertion of the toxin into target mammalian cell membranes. To identify directly the principal toxin sequences dictating membrane binding and insertion, we assayed the lipid bilayer interaction of native protoxin, stably active toxin, and recombinant peptides. Binding was assessed by flotation of protein-liposome mixtures through density gradients, and insertion was assessed by labeling with a photoactivatable probe incorporated into the target lipid bilayer. Both the active acylated hemolysin and the inactive unacylated protoxin were able to bind and also insert. Ca2+binding, which is required for toxin activity, did not influence the in vitro interaction with liposomes. Three overlapping large peptides were expressed separately. A C-terminal peptide including residues 601 to 1024 did not interact in either assay. An internal peptide spanning residues 496 to 831, including the two acylation sites, bound to phospholipid vesicles and showed a low level of insertion-dependent labeling. In vitro acylation had no effect on the bilayer interaction of either this peptide or the full-length protoxin. An N-terminal peptide comprising residues 1 to 520 also bound to phospholipid vesicles and showed strong insertion-dependent labeling, ca. 5- to 25-fold that of the internal peptide. Generation of five smaller peptides from the N-terminal region identified the principal determinant of lipid insertion as the hydrophobic sequence encompassing residues 177 to 411, which is conserved among hemolysin-related toxins.
Intervening Sequences in
rrl
Genes and Fragmentation of 23S rRNA in Genera of the Family
Enterobacteriaceae
Authors: Pronk Loes M. , Sanderson Kenneth E. 
Published: July 2002

ABSTRACT

Intervening sequences (IVSs) in the
rrl
genes for 23S rRNA are transcribed but later removed by RNase III without religation during RNA processing, leading to fragmented rRNA. We examined about 240 strains of the family
Enterobacteriaceae
for presence of IVSs using PCR. No IVSs were detected in strains belonging to
Escherichia
,
Shigella
,
Enterobacter
,
Erwinia
,
Ewingella
,
Hafnia
,
Kluyvera
,
Morganella
,
Pantoea
, or
Serratia
. Previously unreported IVSs were detected in
Klebsiella oxytoca
,
Citrobacter amalonaticus
, and
Providencia stuartii
; previously reported IVSs are in species of
Salmonella
,
Proteus
,
Providencia
, and
Yersinia
. The sporadic distribution of IVSs indicates lateral genetic transfer of IVSs.