bluuebunny/crossref_metadata_2025_split huggingface dataset:
Role of Phagosomes and Major Histocompatibility Complex Class II (MHC-II) Compartment in MHC-II Antigen Processing ofMycobacterium tuberculosisin Human Macrophages
Authors: Torres Martha , Ramachandra Lakshmi , Rojas Roxana E. , Bobadilla Karen , Thomas Jeremy , Canaday David H. , Harding Clifford V. , Boom W. Henry 
Published: February 2006

ABSTRACTMycobacterium tuberculosisresides in phagosomes inside macrophages. In this study, we analyzed the kinetics and location ofM. tuberculosispeptide-major histocompatibility complex class II (MHC-II) complexes inM. tuberculosis-infected human macrophages.M. tuberculosispeptide-MHC-II complexes were detected with polyclonal autologousM. tuberculosis-specific CD4+T cells or F9A6 T hybridoma cells specific forM. tuberculosisantigen (Ag) 85B (96-111). Macrophages processed heat-killedM. tuberculosismore rapidly and efficiently than liveM. tuberculosis. To determine whereM. tuberculosispeptide-MHC-II complexes were formed intracellularly, macrophages incubated with heat-killedM. tuberculosiswere homogenized, and subcellular compartments were separated on Percoll density gradients analyzed with T cells. In THP-1 cells,M. tuberculosisAg 85B (96- 111)-DR1 complexes appeared initially in phagosomes, followed by MHC class II compartment (MIIC) and the plasma membrane fractions. In monocyte-derived macrophages,M. tuberculosispeptide-MHC-II complexes appeared only in MIIC fractions and subsequently on the plasma membrane. Although phagosomes from both cell types acquired lysosome-associated membrane protein 1 (LAMP-1) and MHC-II, THP-1 phagosomes that support formation ofM. tuberculosispeptide-MHC-II complexes had increased levels of both LAMP-1 and MHC-II. Thus,M. tuberculosisphagosomes with high levels of MHC-II and LAMP-1 and MIIC both have the potential to form peptide-MHC-II complexes fromM. tuberculosisantigens in human macrophages.
Gingipains ofPorphyromonas gingivalisModulate Leukocyte Adhesion Molecule Expression Induced in Human Endothelial Cells by Ligation of CD99
Authors: Yun Peter L. W. , DeCarlo Arthur A. , Hunter Neil 
Published: February 2006

ABSTRACTPorphyromonas gingivalishas been implicated as a key etiologic agent in the pathogenesis of destructive chronic periodontitis. Among virulence factors of this organism are cysteine proteinases, or gingipains, that have the capacity to modulate host inflammatory defenses. Intercellular adhesion molecule expression by vascular endothelium represents a crucial process for leukocyte transendothelial migration into inflamed tissue. Ligation of CD99 on endothelial cells was shown to induce expression of endothelial leukocyte adhesion molecule 1, vascular cell adhesion molecule 1, intercellular adhesion molecule 1, and major histocompatibility complex class II molecules and to increase adhesion of leukocytes. CD99 ligation was also found to induce nuclear translocation of NF-κB. These results indicate that endothelial cell activation by CD99 ligation may lead to the up-regulation of adhesion molecule expression via NF-κB activation. However, pretreatment of endothelial cells with gingipains caused a dose-dependent reduction of adhesion molecule expression and leukocyte adhesion induced by ligation of CD99 on endothelial cells. The data provide evidence that the gingipains can reduce the functional expression of CD99 on endothelial cells, leading indirectly to the disruption of adhesion molecule expression and of leukocyte recruitment to inflammatory foci.
Identification of
Legionella pneumophila
-Specific Genes by Genomic Subtractive Hybridization with
Legionella micdadei
and Identification of
lpnE
, a Gene Required for Efficient Host Cell Entry
Authors: Newton Hayley J. , Sansom Fiona M. , Bennett-Wood Vicki , Hartland Elizabeth L. 
Published: February 2006

ABSTRACT

Legionella pneumophila
is a ubiquitous environmental organism and a facultative intracellular pathogen of humans. To identify genes that may contribute to the virulence of
L. pneumophila
, we performed genomic subtractive hybridization between
L. pneumophila
serogroup 1 strain 02/41 and
L. micdadei
strain 02/42. A total of 144
L. pneumophila
-specific clones were sequenced, revealing 151 genes that were absent in
L. micdadei
strain 02/42. Low-stringency Southern hybridization was used to determine the distribution of 41 sequences, representing 40 open reading frames (ORFs) with a range of putative functions among
L. pneumophila
isolates of various serogroups as well as strains of
Legionella longbeachae
,
L. micdadei
,
Legionella gormanii
, and
Legionella jordanis
. Twelve predicted ORFs were
L. pneumophila
specific, including the gene encoding the
dot/icm
effector,
lepB
, as well as several genes predicted to play a role in lipopolysaccharide biosynthesis and cell wall synthesis and several sequences with similarity to virulence-associated determinants. A further nine predicted ORFs were in all
L. pneumophila
serotypes tested and an isolate of
L. gormanii
. These included
icmD
, the 5′ end of a
pilMNOPQ
locus, and two genes known to be upregulated during growth within macrophages,
cadA2
and
ceaA
. Disruption of an
L. pneumophila
-specific gene (lpg2222 locus tag) encoding a putative protein with eight tetratricopeptide repeats resulted in reduced entry into the macrophage-like cell line, THP-1, and the type II alveolar epithelial cell line, A549. The gene was subsequently renamed
lpnE
, for “
L. pneumophila
entry.” In summary, this investigation has revealed important genetic differences between
L. pneumophila
and other
Legionella
species that may contribute to the phenotypic and clinical differences observed within this genus.
Induction of a Novel Chicken Toll-Like Receptor following
Salmonella enterica
Serovar Typhimurium Infection
Authors: Higgs Rowan , Cormican Paul , Cahalane Sarah , Allan Brenda , Lloyd Andrew T. , Meade Kieran , James Tharappel , Lynn David J. , Babiuk Lorne A. , O'Farrelly Cliona 
Published: February 2006

ABSTRACT

Toll-like receptors (TLRs) are a group of highly conserved molecules that initiate the innate immune response to pathogens by recognizing structural motifs expressed by microbes. We have identified a novel TLR, TLR15, by bioinformatic analysis of the chicken genome, which is distinct from any known vertebrate TLR and thus appears to be avian specific. The gene for TLR15 was sequenced and is found on chromosome 3, and it has archetypal TIR and transmembrane domains and a distinctive arrangement of extracellular leucine-rich regions. mRNA for TLR15 was detected in the spleen, bursa, and bone marrow of healthy chickens, suggesting a role for this novel receptor in constitutive host defense. Following in vivo
Salmonella enterica
serovar Typhimurium infection, quantitative real-time PCR demonstrated significant upregulation of TLR15 in the cecum of infected chickens. Interestingly, similar induction of TLR2 expression following infection was also observed. In vitro studies revealed TLR15 upregulation in chicken embryonic fibroblasts stimulated with heat-killed
S. enterica
serovar Typhimurium. Collectively, these results suggest a role for the TLR in avian defense against bacterial infection. We hypothesize that TLR15 may represent an avian-specific TLR that has been either retained in chicken and lost in other taxa or gained in the chicken.
CpG-Modified Plasmid DNA Encoding Flagellin Improves Immunogenicity and Provides Protection againstBurkholderia pseudomalleiInfection in BALB/c Mice
Authors: Chen Yao-Shen , Hsiao Yu-Shan , Lin Hsi-Hsun , Liu Yin , Chen Ya-Lei 
Published: February 2006

ABSTRACTThe plasmid DNA encoding thefliCgene ofBurkholderia pseudomalleicombined with CpG oligodeoxynucleotide (ODN) was injected intramuscularly into BALB/c mice, resulting in the increased production of certain humoral antibodies and flagellin-specific spleen cell clonal expansion. CpG ODN, as an immunoadjuvant, was added to the plasmid containing thefliCgene in order to obtain ongoing expression in muscle for a long period. Functional expression of flagellin from the constructed CpG-modified plasmid in transfected peritoneal exudate cells of BALB/c mice was shown by reverse transcription-PCR and Western blotting. Furthermore, BALB/c mice immunized with the modified plasmid had relatively higher resistance toB. pseudomalleiinfection in vivo than did mice immunized with unmodified plasmid DNA. The time course of restricted bacterial growth in spleen and liver and changes in the cytokine profiles of immunized mice suggested that the stimulated phagocytic cells would be able to kill the bacteria eventually, possibly as a consequence of the induction of Th-1-type immune polarization in vivo. Th-1-type immune polarization was detected in response to flagellin induction in mice immunized with CpG-modified plasmid DNA by the appearance of increased levels of immunoglobulin G2a antibodies and gamma interferon-secreting cells specific to flagellin. The exogenous CpG motifs added to thefliCgene would contribute to an adjuvant-like response that enhances the flagellin-specific immunogenicity and provides protection againstB. pseudomalleiinfection. This CpG-modified plasmid DNA vaccination is an important potential strategy that should be developed to protect against melioidosis.
Mycobacterium bovis
BCG Substrains Confer Different Levels of Protection against
Mycobacterium tuberculosis
Infection in a BALB/c Model of Progressive Pulmonary Tuberculosis
Authors: Castillo-Rodal Antonia Isabel , Castañón-Arreola Mauricio , Hernández-Pando Rogelio , Calva Juan José , Sada-Díaz Eduardo , López-Vidal Yolanda 
Published: February 2006

ABSTRACT

Mycobacterium bovis
BCG is the only available vaccine against tuberculosis. Reasons for why diverse BCG substrains induce different levels of protection in clinical trials remain unclear. The aim of this study was to compare the effectiveness of 10 BCG substrains in a mouse model of pulmonary tuberculosis. BALB/c mice were subcutaneously vaccinated and 2 months later were challenged with
Mycobacterium tuberculosis
H37Rv by intratracheal injection. Two and 4 months after challenge, delayed-type hypersensitivity (DTH) response, lung tissue affected by pneumonia, CFU, T-cell counts, and cytokine expression (interleukin-2 [IL-2], IL-4, IL-10, and gamma interferon) were determined. A differential protective effect of the diverse BCG substrains was found. BCG Phipps led to the largest and most persistent reduction of CFU counts and of the area of pneumonia at 2 and 4 months after challenge. This protection was accompanied by reduced IL-10-producing T cells. Contemporary BCG substrains induce a wide range of protection in this animal model. These data can help in the selection of the best vaccine for human immunization and for the development of novel recombinant BCG-based vaccine.
Heme Transport Contributes to In Vivo Fitness of
Bordetella pertussis
during Primary Infection in Mice
Authors: Brickman Timothy J. , Vanderpool Carin K. , Armstrong Sandra K. 
Published: February 2006

ABSTRACT

Bordetella pertussis
, the causative agent of whooping cough or pertussis, is an obligate human pathogen with multiple high-affinity iron transport systems. Maximal expression of the dedicated heme utilization functions encoded by the
hurIR bhuRSTUV
genes requires an iron starvation signal to relieve Fur repression at the
hurIR
promoter-operator and an inducing signal supplied by heme for HurI-mediated transcriptional activation at the
bhuRSTUV
promoter. The BhuR outer membrane receptor protein is required for heme uptake and for heme sensing for induction of
bhuRSTUV
transcription. It was hypothesized that heme utilization contributed to the success of
B. pertussis
as a pathogen. In this study, virulence attenuation resulting from inactivation of the
B. pertussis
heme system was assessed using mixed infection competition experiments in a mouse model. As a measure of in vivo fitness, the ability of a
B. pertussis
heme utilization mutant to colonize and persist was determined relative to that of an isogenic coinfecting wild-type strain. Relative fitness of the mutant strain declined significantly after 7 days postinfection and continued to decline throughout the remainder of the 28-day infection time course. In parallel infections using inocula supplemented with an inducing 2 μM concentration of hemin chloride, hemin coadministration augmented the competitive advantage of the wild-type strain over the mutant. The results confirm that heme utilization contributes to the pathogenesis of
B. pertussis
in the mouse infection model and indicate that heme utilization may be most important for adaptation to host conditions existing during the later stages of infection.
The Twin Arginine Translocation System Is Essential for Virulence ofYersinia pseudotuberculosis
Authors: Lavander Moa , Ericsson Solveig K. , Bröms Jeanette E. , Forsberg Åke 
Published: February 2006

ABSTRACTYersiniaspecies pathogenic to humans have been extensively characterized with respect to type III secretion and its essential role in virulence. This study concerns the twin arginine translocation (Tat) pathway utilized by gram-negative bacteria to secrete folded proteins across the bacterial inner membrane into the periplasmic compartment. We have shown that theYersiniaTat system is functional and required for motility and contributes to acid resistance. AYersinia pseudotuberculosismutant strain with a disrupted Tat system (tatC) was, however, not affected in in vitro growth or more susceptible to high osmolarity, oxidative stress, or high temperature, nor was it impaired in type III secretion. Interestingly, thetatCmutant was severely attenuated via both the oral and intraperitoneal routes in the systemic mouse infection model and highly impaired in colonization of lymphoid organs like Peyer's patches and the spleen. Our work highlights that Tat secretion plays a key role in the virulence ofY. pseudotuberculosis.
Identification of Fibronectin-Binding Proteins inMycoplasma gallisepticumStrain R
Authors: May Meghan , Papazisi Leka , Gorton Timothy S. , Geary Steven J. 
Published: February 2006

ABSTRACTWe have determined that virulentMycoplasma gallisepticumstrain Rlowis capable of binding the extracellular matrix protein fibronectin. Fibronectin was found to be present inM. gallisepticumRlowprotein extracts by Western blotting and peptide sequencing.Mycoplasma gallisepticumRhigh, the attenuated, high-passage derivative of Rlow, is deficient in this ability. MGA_1199, theM. gallisepticumhomologue of the cytadherence-associated protein P65 fromMycoplasma pneumoniae, and MGA_0928, theM. gallisepticumhomologue of theM. pneumoniaecytoskeletal protein HMW3, were identified as fibronectin-binding proteins. Peptides from the regions of MGA_1199 and MGA_0928 exhibiting the highest degree of homology with known fibronectin-binding proteins were shown to bind the gelatin/heparin-binding domain of fibronectin. MGA_1199 and MGA_0928 were shown to be absent and aberrant, respectively, in Rhigh, explaining its lack of fibronectin-binding capability. Consistent with itsM. pneumoniaecounterpart, MGA_1199 (renamed PlpA) was demonstrated to be surface exposed, despite a lack of classical membrane-spanning domains. Due to its demonstrated topology and the strength of interaction between its binding peptide and fibronectin, we propose that PlpA functions as a fibronectin-binding protein in vivo and may possess atypical transmembrane domains.
A
Helicobacter pylori
Vacuolating Toxin Mutant That Fails To Oligomerize Has a Dominant Negative Phenotype
Authors: Genisset Christophe , Galeotti Cesira L. , Lupetti Pietro , Mercati David , Skibinski David A. G. , Barone Silvia , Battistutta Roberto , de Bernard Marina , Telford John L. 
Published: February 2006

ABSTRACT

Most
Helicobacter pylori
strains secrete a toxin (VacA) that causes massive vacuolization of target cells and which is a major virulence factor of
H. pylori
. The VacA amino-terminal region is required for the induction of vacuolization. The aim of the present study was a deeper understanding of the critical role of the N-terminal regions that are protected from proteolysis when VacA interacts with artificial membranes. Using a counterselection system, we constructed an
H. pylori
strain, SPM 326-Δ49-57, that produces a mutant toxin with a deletion of eight amino acids in one of these protected regions. VacA Δ49-57 was correctly secreted by
H. pylori
but failed to oligomerize and did not have any detectable vacuolating cytotoxic activity. However, the mutant toxin was internalized normally and stained the perinuclear region of HeLa cells. Moreover, the mutant toxin exhibited a dominant negative effect, completely inhibiting the vacuolating activity of wild-type VacA. This loss of activity was correlated with the disappearance of oligomers in electron microscopy. These findings indicate that the deletion in VacA Δ49-57 disrupts the intermolecular interactions required for the oligomerization of the toxin.
Interaction of
Chlamydia trachomatis
with Mammalian Cells Is Independent of Host Cell Surface Heparan Sulfate Glycosaminoglycans
Authors: Stephens Richard S. , Poteralski Jesse M. , Olinger Lynn 
Published: February 2006

ABSTRACT

The hypothesis that host cell surface heparan sulfate is required to promote chlamydial infection was tested using a cell line (CHO-18.4) containing a single retroviral insertion and the concomitant loss of heparan sulfate biosynthesis. Tests of chlamydial infectivity of heparan sulfate-deficient CHO-18.4 cells and parental cells, CHO-22, demonstrated that both were equally sensitive to infection by
Chlamydia trachomatis
serovars L2 and D. These data do not support the hypothesis and demonstrate that host cell surface heparan sulfate does not serve an essential functional role in chlamydial infectivity.
Role for the CD28 Molecule in the Control ofCoxiella burnetiiInfection
Authors: Honstettre Amélie , Meghari Soraya , Nunès Jacques A. , Lepidi Hubert , Raoult Didier , Olive Daniel , Mege Jean-Louis 
Published: February 2006

ABSTRACTQ fever is an infectious disease caused byCoxiella burnetii, an obligate intracellular bacterium that replicates in macrophages. As cell-mediated immune response to microbial pathogens requires signals mediated by T-cell receptors and costimulatory molecules such as CD28, we wondered if CD28 is involved in protection againstC. burnetiiinfection. CD28-deficient (CD28−/−) mice were inoculated withC. burnetiiby intraperitoneal and intravenous routes. With both wild-type and CD28−/−mice,C. burnetiiorganisms were detected exclusively in spleen and liver. The antibody response againstC. burnetiiwas impaired in CD28−/−animals, but, surprisingly, the lack of CD28 decreasedC. burnetiiburden in the infected tissues, whatever the manner of inoculation of bacteria. The CD28 deficiency had no effect on either granuloma formation, which reflects cell-mediated immunity againstC. burnetii, or the production of gamma interferon and tumor necrosis factor, two cytokines known to be involved in granuloma formation. On the other hand, the production of interleukin-10 (IL-10) by peritoneal macrophages was highly impaired in CD28−/−mice. The results suggest that CD28 initiates a signal that favorsC. burnetiireplication through the modulation of the IL-10 pathway.
Conditioned Medium from EnterohemorrhagicEscherichia coli-Infected T84 Cells Inhibits Signal Transducer and Activator of Transcription 1 Activation by Gamma Interferon
Authors: Jandu Narveen , Ceponis Peter J. M. , Kato Seiichi , Riff Jason D. , McKay Derek M. , Sherman Philip M. 
Published: February 2006

ABSTRACTGamma interferon (IFN-γ) is a cytokine important to host defense which can signal through signal transducer and activator of transcription 1 (Stat1). EnterohemorrhagicEscherichia coli(EHEC) modulates host cell signal transduction to establish infection, and EHEC serotypes O113:H21 and O157:H7 both inhibit IFN-γ-induced Stat1 tyrosine phosphorylation in vitro. The aim of this study was to delineate both bacterial and host cell factors involved in the inhibition of Stat1 tyrosine phosphorylation. Human T84 colonic epithelial cells were challenged with direct infection, viable EHEC separated from T84 cells by a filter, sodium orthovanadate, isolated flagellin, bacterial culture supernatants, and conditioned medium treated with proteinase K, trypsin, or heat inactivation. Epithelial cells were then stimulated with IFN-γ and protein extracts were analyzed by immunoblotting. The data showed that IFN-γ-inducible Stat1 tyrosine phosphorylation was inhibited when EHEC adhered to T84 cells, but not by bacterial culture supernatants or bacteria separated from the epithelial monolayer. Conditioned medium from T84 cells infected with EHEC O157:H7 suppressed Stat1 activation, and this was not reversed by treatment with proteinases or heat inactivation. Use of pharmacological inhibitors showed that time-dependent bacterial, but not epithelial, protein synthesis was involved. Stat1 inhibition was also independent of bacterial flagellin, host proteasome activity, and protein tyrosine phosphatases. Infection led to altered IFN-γ receptor domain 1 subcellular distribution and decreased expression in cholesterol-enriched membrane microdomains. Thus, suppression of host cell IFN-γ signaling by production of a contact-dependent, soluble EHEC factor may represent a novel mechanism for this pathogen to evade the host immune system.
Induced Biliary Excretion ofListeria monocytogenes
Authors: Hardy Jonathan , Margolis Jeffrey J. , Contag Christopher H. 
Published: February 2006

ABSTRACTListeria monocytogenesis a ubiquitous gram-positive bacterium that can cause systemic and often life-threatening disease in immunocompromised hosts. This organism is largely an intracellular pathogen; however, we have determined that it can also grow extracellularly in animals, in the lumen of the gallbladder. The significance of growth in the gallbladder with respect to the pathogenesis and spread of listeriosis depends on the ability of the bacterium to leave this organ and be disseminated to other tissues and into the environment. Should this process be highly inefficient, growth in the gallbladder would have no impact on pathogenesis or spread, but if it occurs efficiently, bacterial growth in this organ may contribute to listeriosis and dissemination of this organism. Here, we use whole-body imaging to determine the efficacy and kinetics of food- and hormone-induced biliary excretion ofL. monocytogenesfrom the murine gallbladder, demonstrating that transit through the bile duct into the intestine can occur within 5 min of induction of gallbladder contraction by food or cholecystokinin and that movement of bacteria through the intestinal lumen can occur very rapidly in the absence of fecal material. These studies demonstrate thatL. monocytogenesbacteria replicating in the gallbladder can be expelled from the organ efficiently and that the released bacteria move into the intestinal tract, where they pass into the environment and may possibly reinfect the animal.