bluuebunny/crossref_metadata_2025_split huggingface dataset:
Genotypic Profile of the Outer Membrane Proteins BabA and BabB in Clinical Isolates of
Helicobacter pylori
Authors: Colbeck Jeffrey C. , Hansen Lori M. , Fong Julie M. , Solnick Jay V. 
Published: June 2006

ABSTRACT

Helicobacter pylori
BabA is the ABO blood group antigen binding adhesin, which has a closely related paralogue (BabB) whose function is unknown. PCR and DNA sequence analysis showed extensive genotypic diversity in
babA
and
babB
across different strains, as well as within a strain colonizing an individual patient. We hypothesize that diverse profiles of
babA
and
babB
reflect selective pressures for adhesion, which may differ across different hosts and within an individual over time.
Identification and Characterization of an Antigen I/II Family Protein Produced by Group AStreptococcus
Authors: Zhang Shizhen , Green Nicole M. , Sitkiewicz Izabela , LeFebvre Rance B. , Musser James M. 
Published: June 2006

ABSTRACTGroup AStreptococcus(GAS) is a gram-positive human bacterial pathogen that causes infections ranging in severity from pharyngitis to life-threatening invasive disease, such as necrotizing fasciitis. Serotype M28 strains are consistently isolated from invasive infections, particularly puerperal sepsis, a severe infection that occurs during or after childbirth. We recently sequenced the genome of a serotype M28 GAS strain and discovered a novel 37.4-kb foreign genetic element designated region of difference 2 (RD2). RD2 is similar in gene content and organization to genomic islands found in group B streptococci (GBS), the major cause of neonatal infections. RD2 encodes seven proteins with conventional gram-positive secretion signal sequences, six of which have not been characterized. Herein, we report that one of these six proteins (M28_Spy1325; Spy1325) is a member of the antigen I/II family of cell surface-anchored molecules produced by oral streptococci. PCR and DNA sequence analysis found that Spy1325 is very well conserved in GAS strains of distinct M protein serotypes. As assessed by real-time TaqMan quantitative PCR, the Spy1325 gene was expressed in vitro, and Spy1325 protein was present in culture supernatants and on the GAS cell surface. Western immunoblotting and enzyme-linked immunosorbent assays indicated that Spy1325 was produced by GAS in infected mice and humans. Importantly, the immunization of mice with recombinant Spy1325 fragments conferred protection against GAS-mediated mortality. Similar to other antigen I/II proteins, recombinant Spy1325 bound purified human salivary agglutinin glycoprotein. Spy1325 may represent a shared virulence factor among GAS, GBS, and oral streptococci.
Pneumococcal Neuraminidases A and B Both Have Essential Roles during Infection of the Respiratory Tract and Sepsis
Authors: Manco Sonia , Hernon Fidelma , Yesilkaya Hasan , Paton James C. , Andrew Peter W. , Kadioglu Aras 
Published: June 2006

ABSTRACT

We examined the role of the neuraminidases NanA and NanB in colonization and infection in the upper and lower respiratory tract by
Streptococcus pneumoniae
, as well as the role of these neuraminidases in the onset and development of septicemia following both intranasal and intravenous infection. We demonstrated for the first time using outbred MF1 mouse models of infection that both NanA and NanB were essential for the successful colonization and infection of the upper and lower respiratory tract, respectively, as well as pneumococcal survival in nonmucosal sites, such as the blood. Our studies have shown that in vivo a neuraminidase A mutant is cleared from the nasopharynx, trachea, and lungs within 12 h postinfection, while a neuraminidase B mutant persists but does not increase in either the nasopharynx, trachea, or lungs. We also demonstrated both neuraminidase mutants were unable to cause sepsis following intranasal infections. When administered intravenously, however, both mutants survived initially but were unable to persist in the blood beyond 48 h postinfection and were progressively cleared. The work presented here demonstrates the importance of pneumococcal neuraminidase A and for the first time neuraminidase B in the development of upper and lower respiratory tract infection and sepsis.
Escherichia coli
Cytotoxic Necrotizing Factor 1 Blocks Cell Cycle G
2
/M Transition in Uroepithelial Cells
Authors: Falzano Loredana , Filippini Perla , Travaglione Sara , Miraglia Alessandro Giamboi , Fabbri Alessia , Fiorentini Carla 
Published: June 2006

ABSTRACT

Evidence is accumulating that a growing number of bacterial toxins act by modulating the eukaryotic cell cycle machinery. In this context, we provide evidence that a protein toxin named cytotoxic necrotizing factor 1 (CNF1) from uropathogenic
Escherichia coli
is able to block cell cycle G
2
/M transition in the uroepithelial cell line T24. CNF1 permanently activates the small GTP-binding proteins of the Rho family that, beside controlling the actin cytoskeleton organization, also play a pivotal role in a large number of other cellular processes, including cell cycle regulation. The results reported here show that CNF1 is able to induce the accumulation of cells in the G
2
/M phase by sequestering cyclin B1 in the cytoplasm and down-regulating its expression. The possible role played by the Rho GTPases in the toxin-induced cell cycle deregulation has been investigated and discussed. The activity of CNF1 on cell cycle progression can offer a novel view of
E. coli
pathogenicity.
Toxoplasma gondiiInhibits Toll-Like Receptor 4 Ligand-Induced Mobilization of Intracellular Tumor Necrosis Factor Alpha to the Surface of Mouse Peritoneal Neutrophils
Authors: Bennouna Soumaya , Sukhumavasi Woraporn , Denkers Eric Y. 
Published: June 2006

ABSTRACTNeutrophils are well-known to rapidly respond to infection through chemotactic infiltration at sites of inflammation, followed by rapid release of microbicidal molecules, chemokines, and proinflammatory cytokines. For tumor necrosis factor alpha (TNF-α), we recently found that neutrophils contain intracellular pools of the cytokine and display the capacity to upregulate transcriptional activity of the gene during lipopolysaccharide (LPS) stimulation. We now show that triggering of mouse peritoneal neutrophils with Toll-like receptor 2 (TLR2), TLR4, and TLR9 ligands, but not ligands of TLR3, induces upregulation of surface membrane TNF-α. However, neutrophils infected with the protozoanToxoplasma gondiidisplayed an inability to respond fully in terms of TLR ligand-induced increases in membrane TNF-α expression. Infected neutrophils failed to display decreased levels of intracellular TNF-α upon LPS exposure. In contrast to intermediate inhibitory effects in nontreated neutrophils,T. gondiiinduced a complete blockade in LPS-induced surface TNF-α expression in the presence of the protein synthesis inhibitor cycloheximide. Despite these inhibitory effects, the parasite did not affect LPS-induced upregulation of TNF-α gene transcription. Collectively, the results show thatToxoplasmaprevents TLR ligand-triggered mobilization of TNF-α to the neutrophil surface, revealing a novel immunosuppressive activity of the parasite.
Exploitation of the Endocytic Pathway by
Orientia tsutsugamushi
in Nonprofessional Phagocytes
Authors: Chu Hyuk , Lee Jung-Hee , Han Seung-Hoon , Kim Se-Yoon , Cho Nam-Hyuk , Kim Ik-Sang , Choi Myung-Sik 
Published: June 2006

ABSTRACT

Orientia tsutsugamushi
, a causative agent of scrub typhus, is an obligate intracellular bacterium that requires the exploitation of the endocytic pathway in the host cell. We observed the localization of
O. tsutsugamushi
with clathrin or adaptor protein 2 within 30 min after the infection of nonprofessional phagocytes. We have further confirmed that the infectivity of
O. tsutsugamushi
is significantly reduced by drugs that block clathrin-mediated endocytosis but not by filipin III, an inhibitor that blocks caveola-mediated endocytosis. In the present study, with a confocal microscope,
O. tsutsugamushi
was sequentially colocalized with the early and late endosomal markers EEA1 and LAMP2, respectively, within 1 h after infection. The colocalization of
O. tsutsugamushi
organisms with EEA1 and LAMP2 gradually disappeared until 2 h postinfection, and then free
O. tsutsugamushi
organisms were found in the cytoplasm. When the acidification of endocytic vesicles was blocked by treating the cells with NH
4
Cl or bafilomycin A, the escape of
O. tsutsugamushi
organisms from the endocytic pathway was severely impaired, and the infectivity of
O. tsutsugamushi
was drastically reduced. To our knowledge, this is the first report that the invasion of
O. tsutsugamushi
is dependent on the clathrin-dependent endocytic pathway and the acidification process of the endocytic vesicles in nonprofessional phagocytes.
TheActinobacillus actinomycetemcomitansRibose Binding Protein RbsB Interacts with Cognate and Heterologous Autoinducer 2 Signals
Authors: James DeAnna , Shao HanJuan , Lamont Richard J. , Demuth Donald R. 
Published: June 2006

ABSTRACTAutoinducer 2 (AI-2) produced by the oral pathogenActinobacillus actinomycetemcomitansinfluences growth of the organism under iron limitation and regulates the expression of iron uptake genes. However, the cellular components that mediate the response ofA. actinomycetemcomitansto AI-2 have not been fully characterized. Analysis of the complete genome sequence ofA. actinomycetemcomitans(www.oralgen.lanl.gov) indicated that the RbsB protein was related to LuxP, the AI-2 receptor ofVibrio harveyi. To determine if RbsB interacts with AI-2, the bioluminescence of the reporter strainV. harveyiBB170 (sensor 1−, sensor 2+) was determined after stimulation with partially purified AI-2 fromA. actinomycetemcomitansor conditioned medium fromV. harveyicultures in the presence and absence of purified six-His-tagged RbsB. RbsB efficiently inhibitedV. harveyibioluminescence induced by bothA. actinomycetemcomitansAI-2 andV. harveyiAI-2 in a dose-dependent manner, suggesting that RbsB competes with LuxP for AI-2. Fifty percent inhibition occurred with approximately 0.3 nM RbsB forA. actinomycetemcomitansAI-2 and 15 nM RbsB forV. harveyiAI-2. RbsB-mediated inhibition ofV. harveyibioluminescence was reversed by the addition of 50 mM ribose, suggesting thatA. actinomycetemcomitansAI-2 and ribose bind at the same site of RbsB. The RbsB/AI-2 complex was thermostable sinceA. actinomycetemcomitansAI-2 could not be recovered by heating. This was not due to heat inactivation ofA. actinomycetemcomitansAI-2 since signal activity was unaffected by heating in the absence of RbsB. Furthermore, an isogenicA. actinomycetemcomitansmutant that was unable to expressrbsBwas deficient in depletingA. actinomycetemcomitansAI-2 from solution relative to the wild-type organism. Inactivation ofrbsBalso influenced the ability of the organism to grow under iron-limiting conditions. The mutant strain attained a cell density of approximately 30% that of the wild-type organism under iron limitation. In addition, real-time PCR showed that the expression ofafuABC, encoding a major ferric ion transporter, was reduced by approximately eightfold in therbsBmutant. This phenotype was similar to that of a LuxS-deficient mutant ofA. actinomycetemcomitansthat is unable to produce AI-2. Together, our results suggest that RbsB may play a role in the response ofA. actinomycetemcomitansto AI-2.
Cell Activation by Ligands of the Toll-Like Receptor and Interleukin-1 Receptor Family Depends on the Function of the Large-Conductance Potassium Channel MaxiK in Human Macrophages
Authors: Scheel Olaf , Papavlassopoulos Martin , Blunck Rikard , Gebert Andreas , Hartung Thomas , Zähringer Ulrich , Seydel Ulrich , Schromm Andra B. 
Published: June 2006

ABSTRACT

Performing patch-clamp experiments on human macrophages, we show that the K
+
channel MaxiK is activated by lipopolysaccharide, peptidoglycan, and interleukin-1. Cytokine production initiated by several Toll-like receptor (TLR) ligands and by interleukin-1 is inhibited by MaxiK blockade. This provides evidence for functional association of the MaxiK channel and TLR signaling complexes.
Type III Secretion-Dependent Modulation of Innate Immunity as One of Multiple Factors Regulated byPseudomonas aeruginosaRetS
Authors: Zolfaghar Irandokht , Evans David J. , Ronaghi Reza , Fleiszig Suzanne M. J. 
Published: June 2006

ABSTRACTMutation ofretS(rtsM) ofPseudomonas aeruginosastrain PA103 reduces its virulence in both ocular and respiratory murine models of infection. In vitro,retSmutants exhibit loss of the ExsA-regulated type III secretion system (TTSS), reduced twitching motility, and a decrease in association with, invasion of, and survival within corneal epithelial cells. In addition, transcription of multiple other virulence genes is positively and negatively affected byretSmutation. Since our published data show that ExoU and ExoT, the two TTSS effectors encoded by strain PA103, each confer virulence in this corneal model, we hypothesized that loss of virulence ofretSmutants follows loss of type III secretion. Corneal pathology, bacterial colonization, and phagocyte infiltration were compared for wild-type PA103,retSmutants, and various TTSS mutants after infection with ∼106CFU bacteria. Results showed that either aretSor anexsA(TTSS) mutation delayed disease progression, as illustrated by reduced severity scores and colonization levels during the first 48 h postinfection. Surprisingly,retSmutant infections then became more severe than those involvingexsAmutants. By day 7, colonization levels ofretSmutants even surpassed those of wild-type bacteria (more than twofold,P = 0.028). AlthoughretSmutants caused more severe opacification of central corneas than both the wild type and theexsAmutants, neither mutant caused the peripheral ring opacity commonly associated with wild-type infection, suggesting that the TTSS was involved. Histological experiments withretSand various TTSS mutants showed that ring opacification required ExoU but not ExoT and that it consisted of dense polymorphonuclear phagocyte infiltration at the corneal periphery and the absence of any cell type in the central cornea. These data suggest that theseP. aeruginosaTTSS effectors have different effects on innate immunity and that RetS influences virulence beyond its effects on the TTSS.
The Animal Pathogen-Like Type III Secretion System Is Required for the Intracellular Survival of
Burkholderia mallei
within J774.2 Macrophages
Authors: Ribot Wilson J. , Ulrich Ricky L. 
Published: June 2006

ABSTRACT

Burkholderia mallei
is a highly infectious gram-negative pathogen and is the causative agent of human and animal glanders. By generating polar mutations (disruption of
bsaQ
and
bsaZ
) in the
B. mallei
ATCC 23344 animal pathogen-like type III secretion system (TTS), we demonstrate that this bacterial protein delivery system is required for intracellular growth of
B. mallei
in J774.2 cells, formation of macrophage membrane protrusions, actin polymerization, and phagosomal escape. These findings suggest that TTS plays a role in the intracellular trafficking of
B. mallei
and may facilitate cell-to-cell spread via actin-based motility.
Doxycycline Reduces Mortality and Injury to the Brain and Cochlea in Experimental Pneumococcal Meningitis
Authors: Meli Damian N. , Coimbra Roney S. , Erhart Dominik G. , Loquet Gerard , Bellac Caroline L. , Täuber Martin G. , Neumann Ulf , Leib Stephen L. 
Published: June 2006

ABSTRACTBacterial meningitis is characterized by an inflammatory reaction to the invading pathogens that can ultimately lead to sensorineural hearing loss, permanent brain injury, or death. The matrix metalloproteinases (MMPs) and tumor necrosis factor alpha-converting enzyme (TACE) are key mediators that promote inflammation, blood-brain barrier disruption, and brain injury in bacterial meningitis. Doxycycline is a clinically used antibiotic with anti-inflammatory effects that lead to reduced cytokine release and the inhibition of MMPs. Here, doxycycline inhibited TACE with a 50% inhibitory dose of 74 μM in vitro and reduced the amount of tumor necrosis factor alpha released into the cerebrospinal fluid by 90% in vivo. In an infant rat model of pneumococcal meningitis, a single dose of doxycycline (30 mg/kg) given as adjuvant therapy in addition to ceftriaxone 18 h after infection significantly reduced the mortality, the blood-brain barrier disruption, and the extent of cortical brain injury. Adjuvant doxycycline (30 mg/kg given subcutaneously once daily for 4 days) also attenuated hearing loss, as assessed by auditory brainstem response audiometry, and neuronal death in the cochlear spiral ganglion at 3 weeks after infection. Thus, doxycycline, probably as a result of its anti-inflammatory properties, had broad beneficial effects in the brain and the cochlea and improved survival in this model of pneumococcal meningitis in infant rats.
Identification of
Francisella tularensis
Genes Affected by Iron Limitation
Authors: Deng Kaiping , Blick Robert J. , Liu Wei , Hansen Eric J. 
Published: June 2006

ABSTRACT

Cells of an attenuated live vaccine strain (LVS) of
F. tularensis
grown under iron-restricted conditions were found to contain increased quantities of several proteins relative to cells of this same strain grown under iron-replete conditions. Mass spectrometric analysis identified two of these proteins as IglC and PdpB, both of which are encoded by genes located in a previously identified pathogenicity island in
F. tularensis
LVS. Regions with homology to the consensus Fur box sequence were located immediately in front of the
iglC
and
pdpB
open reading frames (ORFs), and in silico analysis of the
F. tularensis
Schu4 genome detected a number of predicted 5′ untranslated regions that contained putative Fur boxes. The putative Fur box preceding
Francisella
iron-regulated gene A (
figA
) had the highest degree of identity with the consensus Fur box sequence. DNA microarray analysis showed that nearly 80 of the genes in the
F. tularensis
LVS genome were up- or down-regulated at least twofold under iron-restricted growth conditions. When tested for possible siderophore production by means of the Chrome Azurol S assay, a wild-type
F. novicida
strain produced a large reaction zone whereas its
figA
mutant produced very little reactivity in this assay. In addition, a cross-feeding experiment demonstrated that this siderophore-like activity produced by the wild-type
F. novicida
strain could enhance the ability of the
F. novicida figA
mutant to grow under iron-restricted conditions. This study provides the first identification of iron-regulated genes in
F. tularensis
LVS and evidence for the production of a siderophore-like molecule by
F. novicida
.
Role of Sigma E-Regulated Genes in
Escherichia coli
Uropathogenesis
Authors: Redford Peter , Welch Rodney A. 
Published: June 2006

ABSTRACT

The sigma E regulon encodes proteins for maintenance and repair of the
Escherichia coli
cell envelope. Previously, we observed that an antirepressor of sigma E, DegS, is essential for uropathogenic
E. coli
virulence. Here we use a mouse urinary tract infection model to assay the virulence of mutants of
E. coli
genes described as sigma E dependent. Deletion mutants of candidate genes were made in the uropathogenic
E. coli
strain CFT073. Swiss Webster female mice were inoculated with a mixture of mutant and wild-type strains. Bladder and kidney homogenates were cultured 2 days after infection, and CFU of the wild type and mutant were compared. Eleven mutants were assayed, and two, CFT073
degP
and CFT073
skp
, showed significantly diminished survival compared to wild type. DegP is a chaperone and degradase active in the periplasm. Skp is also a periplasmic chaperone. The virulence of the
skp
deletion mutant could not be restored by complementation with
skp
. The virulence of the
degP
deletion mutant, in contrast, could be restored. However, complementation with a
degP
allele encoding a serine-to-alanine (S210A) mutation at the protease active site fails to restore virulence. Unlike
degP
mutants in other bacteria, the
E. coli degP
mutant is tolerant of oxidative stress. It disappears abruptly from bladder and kidney cultures between 6 and 12 hours after inoculation. A mutant of
degQ
, a close homolog of
degP
, was not attenuated in mice. This is the first report that the DegP degradase is an
E. coli
virulence factor in an animal infection model.
Mucosal Immunity to Asymptomatic
Entamoeba histolytica
and
Entamoeba dispar
Infection Is Associated with a Peak Intestinal Anti-Lectin Immunoglobulin A Antibody Response
Authors: Abd-Alla Mohamed D. , Jackson Terry F. G. H. , Rogers Tyson , Reddy Selvan , Ravdin Jonathan I. 
Published: June 2006

ABSTRACT

We monitored 93 subjects cured of amebic liver abscess (ALA) and 963 close associate controls in Durban, South Africa, and determined by enzyme-linked immunosorbent assay that the intestinal immunoglobulin A (IgA) antibody response to the
Entamoeba histolytica
galactose-inhibitable adherence lectin is most accurately represented by a complex pattern of transitory peaks. One or more intestinal anti-lectin IgA antibody peaks occurred in 85.9% of ALA subjects over 36 months compared to 41.6% of controls (
P
< 0.0001). ALA subjects exhibited a greater number of anti-lectin IgA antibody peaks (
P
< 0.0001) than controls. In addition, their peak optical density values were higher (peak numbers 1 to 3,
P
< 0.003), peaks were of longer duration (for peaks 1 and 2,
P
≤ 0.0054), and there was a shorter time interval between peaks (between 1 and 2 or 2 and 3,
P
≤ 0.0106) than observed for control subjects. A prior
E. histolytica
infection was associated with the occurrence of an anti-lectin IgA antibody peak (79.1%,
P
< 0.0001) more so than for
Entamoeba dispar
infection (57.2%,
P
< 0.001). The annual number of anti-lectin IgA antibody peaks in ALA subjects was 0.71 per year, compared to just 0.22 in controls (
P
<0.0001), indicating a higher rate of exposure to the parasite than previously appreciated. Anti-lectin IgA antibody peaks were of higher amplitude following a
E. histolytica
infection compared to
E. dispar
(
P
= 0.01) and, for either, were of greater height in ALA subjects than controls (
P
< 0.01). ALA subjects demonstrated greater clearance of amebic infection after an anti-lectin IgA antibody peak compared to controls, and only 14.3% remained with a positive culture after the peak, compared to 38.9% in controls (
P
= 0.035). In summary, this prospective controlled longitudinal study elucidated the dynamic nature of the human intestinal IgA antibody response to
E. histolytica
and
E. dispar
infection and revealed that ALA subjects exhibit heightened intestinal anti-lectin IgA antibody peaks that are associated with clearance of
E. histolytica
and
E. dispar
infection.