bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of
Brucella abortus
O-Polysaccharide and Core Lipopolysaccharide Mutants and Demonstration that a Complete Core Is Required for Rough Vaccines To Be Efficient against
Brucella abortus
and
Brucella ovis
in the Mouse Model
Authors: Monreal D. , Grilló M. J. , González D. , Marín C. M. , De Miguel M. J. , López-Goñi I. , Blasco J. M. , Cloeckaert A , Moriyón I. 
Published: May 2003

ABSTRACT

Brucella abortus
rough lipopolysaccharide (LPS) mutants were obtained by transposon insertion into two
wbk
genes (
wbkA
[putative glycosyltransferase; formerly
rfbU
] and
per
[perosamine synthetase]), into
manB
(
pmm
[phosphomannomutase; formerly
rfbK
]), and into an unassigned gene. Consistent with gene-predicted roles, electrophoretic analysis, 2-keto-3-
manno
-d-
octulosonate measurements, and immunoblots with monoclonal antibodies to O-polysaccharide, outer and inner core epitopes showed no O-polysaccharide expression and no LPS core defects in the
wbk
mutants. The rough LPS of
manB
mutant lacked the outer core epitope and the gene was designated

manB
core

to distinguish it from the

wbk manB
O-Ag

. The fourth gene (provisionally designated
wa**
) coded for a putative glycosyltransferase involved in inner core synthesis, but the mutant kept the outer core epitope. Differences in phage and polymyxin sensitivity, exposure or expression of outer membrane protein, core and lipid A epitopes, and lipid A acylation demonstrated that small changes in LPS core caused significant differences in
B. abortus
outer membrane topology. In mice, the mutants showed different degrees of attenuation and induced antibodies to rough LPS and outer membrane proteins. Core-defective mutants and strain RB51 were ineffective vaccines against
B. abortus
in mice. The mutants
per
and
wbkA
induced protection but less than the standard smooth vaccine S19, and controls suggested that anti O-polysaccharide antibodies accounted largely for the difference. Whereas no core-defective mutant was effective against
B. ovis
, S19, RB51, and the
wbkA
and
per
mutants afforded similar levels of protection. These results suggest that rough
Brucella
vaccines should carry a complete core for maximal effectiveness.
Neospora caninum-Infected Cattle Develop Parasite-Specific CD4+Cytotoxic T Lymphocytes
Authors: Staska Lauren M. , McGuire Travis C. , Davies Christopher J. , Lewin Harris A. , Baszler Timothy V. 
Published: May 2003

ABSTRACTCattle infected withNeospora caninumreadily experience transplacental parasite transmission, presumably after maternal parasitemia, leading to abortion or birth of congenitally infected calves. Cytotoxic T lymphocytes (CTL) are important mediators of protective immunity againstToxoplasma gondii, an intracellular apicomplexan protozoan closely related toN. caninum. In this study,N. caninum-specific CTL expanded from peripheral blood mononuclear cells of two major histocompatibility complex-mismatched, experimentally infected cattle were identified by using a51Cr release cytotoxicity assay. Enrichment and blocking of CD4+- and CD8+-T-lymphocyte effector subsets indicated that CD4+CTL killedN. caninum-infected, autologous target cells and that killing was mediated through a perforin/granzyme pathway. Detection and characterization of CTL responses toN. caninumin the natural, outbred, bovine host will facilitate identification of immunogens and design of immunization strategies to induce parasite-specific CTL against transplacentalN. caninumtransmission in cattle.
Distribution and Kinetics of Lipoprotein-Bound Lipoteichoic Acid
Authors: Levels Johannes H. M. , Abraham Philip R. , van Barreveld Erik P. , Meijers Joost C. M. , van Deventer Sander J. H. 
Published: May 2003

ABSTRACTLipoteichoic acid (LTA), a major cell wall component of gram-positive bacteria, is an amphipathic anionic glycolipid with structural similarities to lipopolysaccharide (LPS) from gram-negative bacteria. LTA has been implicated as one of the primary immunostimulatory components that may trigger the systemic inflammatory response syndrome. Plasma lipoproteins have been shown to sequester LPS, which results in attenuation of the host response to infection, but little is known about the LTA binding characteristics of plasma lipid particles. In this study, we have examined the LTA binding capacities and association kinetics of the major lipoprotein classes under simulated physiological conditions in human whole blood (ex vivo) by using biologically active, fluorescently labeled LTA and high-performance gel permeation chromatography. The average distribution of an LTA preparation fromStaphylococcus aureusin whole blood from 10 human volunteers revealed that >95% of the LTA was associated with total plasma lipoproteins in the following proportions: high-density lipoprotein (HDL), 68% ± 10%; low-density lipoprotein (LDL), 28% ± 8%; and very low density lipoprotein (VLDL), 4% ± 5%. The saturation capacity of lipoproteins for LTA was in excess of 150 μg/ml. The LTA distribution was temperature dependent, with an optimal binding between 22 and 37°C. The binding of LTA by lipoproteins was essentially complete within 10 min and was followed by a subsequent redistribution from HDL and VLDL to LDL. We conclude that HDL has the highest binding capacity for LTA and propose that the loading and redistribution of LTA among plasma lipoproteins is a specific process that closely resembles that previously described for LPS (J. H. M. Levels, P. R. Abraham, A. van den Ende, and S. J. H. van Deventer, Infect. Immun.68:2821-2828, 2001).
Characterization of an
iroBCDEN
Gene Cluster on a Transmissible Plasmid of Uropathogenic
Escherichia coli
: Evidence for Horizontal Transfer of a Chromosomal Virulence Factor
Authors: Sorsa Liisa Johanna , Dufke Severin , Heesemann Jürgen , Schubert Sören 
Published: May 2003

ABSTRACT

The chromosomal
iroBCDEN
gene cluster first described for
Salmonella enterica
is involved in the uptake of catecholate-type siderophore compounds. An orthologous gene cluster has recently been detected in
Escherichia coli
strains which cause extraintestinal disease. This
E. coli iroBCDEN
gene cluster has an impact on virulence and has been reported to be located in a pathogenicity island on the chromosome. In this study we characterized an
iro
gene cluster of a uropathogenic
E. coli
isolate which is located on a transmissible plasmid related to the R64 plasmid of
S. enterica
. This cluster is highly homologous to the chromosomal
iro
cluster of
E. coli
. When introduced into an
E. coli fepA cir fiu aroB
mutant, IroN, but not IroBCDE, mediated the utilization of structurally related catecholate siderophores, including 2,3-dihydroxybenzoyl-
l
-serine, 2,3-dihydroxybenzoyl-
d
-ornithine, 2,3-dihydroxybenzoic acid, and enterochelin. This study supports the idea of an ongoing horizontal transfer of putative virulence factors and the mobilization of single virulence gene clusters, which lead to a modular assembly of virulence determinants such as pathogenicity islands.
Mutational Analysis of the Enzymatic Domain ofClostridium difficileToxin B Reveals Novel Inhibitors of the Wild-Type Toxin
Authors: Spyres Lea M. , Daniel Jeremy , Hensley Amy , Qa'Dan Maen , Ortiz-Leduc William , Ballard Jimmy D. 
Published: May 2003

ABSTRACTToxin B (TcdB), a majorClostridium difficilevirulence factor, glucosylates and inactivates the small GTP-binding proteins Rho, Rac, and Cdc42. In the present study we provide evidence that enzymatically inactive fragments of the TcdB enzymatic domain are effective intracellular inhibitors of native TcdB. Site-directed and deletion mutants of the TcdB enzymatic region (residues 1 to 556), lacking receptor binding and cell entry domains, were analyzed for attenuation of glucosyltransferase and glucosylhydrolase activity. Five of six derivatives from TcdB1-556were found to be devoid of enzymatic activity. In order to facilitate cell entry, mutants were genetically fused tolfn, which encodes the protective antigen binding region of anthrax toxin lethal factor and mediates the cell entry of heterologous proteins. In line with reduced enzymatic activity, the mutants also lacked cytotoxicity. Remarkably, pretreatment or cotreatment of cells with four of the mutants provided protection against the cytotoxic effects of native TcdB. Furthermore, a CHO cell line expressing enzymatically active TcdB1-556was also protected by the mutant-derived inhibitors, suggesting that inhibition occurred at an intracellular location. Protection also was afforded by the inhibitor to cells treated withClostridium sordelliilethal toxin (TcsL), which uses the same cosubstrate as TcdB but shares Rac only as a common substrate target. Finally, the inhibitor did not provide protection againstClostridium novyialpha-toxin (Τcnα), which shares similar substrates with TcdB yet uses a different cosubstrate. This is the first report to demonstrate that the potential exists to inhibit toxins at their intracellular site of action by using inactive mutants.
The Immunoglobulin D-Binding Protein MID fromMoraxella catarrhalisIs Also an Adhesin
Authors: Forsgren Arne , Brant Marta , Karamehmedovic Mirela , Riesbeck Kristian 
Published: May 2003

ABSTRACTTheMoraxella catarrhalisimmunoglobulin D (IgD)-binding protein (MID) is a 200-kDa outer membrane protein displaying a unique and specific affinity for human IgD. MID is found in the majority ofM. catarrhalisstrains. In the present paper, we show that MID-expressingM. catarrhalisstrains agglutinate human erythrocytes and bind to type II alveolar epithelial cells. In contrast,M. catarrhalisisolates with low MID expression levels and two mutants deficient in MID, but with readily detectable UspA1 expression, do not agglutinate erythrocytes and have a 50% lower adhesive capacity. To examine the adhesive part of MID, the protein was dissected into nine fragments covering the entire molecule. The truncated MID proteins were expressed inEscherichia coli, purified, and used for raising polyclonal antibodies in rabbits. Interestingly, by using recombinant fragments, we show that the hemagglutinating and adhesive part of MID is localized within the 150-amino-acid fragment MID764-913. In addition, antibodies against full-length MID, MID764-913, or a 30-amino-acid consensus sequence (MID775-804) inhibited adhesion to alveolar epithelial cells. Antibodies against UspA1, an outer membrane protein expressed in essentially allM. catarrhalisstrains, also inhibited adhesion, suggesting that both MID and UspA1 are needed for optimal attachment to epithelial cells. Taken together, in addition to MID-dependent IgD binding, we have demonstrated that the outer membrane protein MID is a novel adhesin that would be a suitable target for a future vaccine againstM. catarrhalis.
Secretin of the EnteropathogenicEscherichia coliType III Secretion System Requires Components of the Type III Apparatus for Assembly and Localization
Authors: Gauthier Annick , Puente Jose Luis , Finlay B. Brett 
Published: May 2003

ABSTRACTAt least 16 proteins are thought to be involved in forming the enteropathogenicEscherichia coli(EPEC) type III translocation apparatus which delivers virulence factors into host cells, yet their function and location have not been determined. A biochemical analysis was performed on three components: EscN, a predicted cytoplasmic ATPase; EscV, a predicted inner membrane protein; and EscC, a predicted outer membrane secretin. Wild-type EPEC and mutants constructed in these genes were fractionated by lysozyme treatment, ultracentrifugation, and selective detergent extraction. Fractionation revealed that the type III effectors Tir and EspB required a complete type III apparatus for any degree of export by EPEC, suggesting a continuous channel. Epitope-tagged EscC, EscV, and EscN were localized by fractionation, confirming computer modeling predictions for their location. Transcomplementation experiments revealed that localization of EscV and EscN was unaffected by mutations in other examined type III components. Remarkably, localization of EscC was altered inescVorescNmutants, where EscC accumulated in the periplasm. EscC was correctly localized in theescFneedle component mutant, indicating that secretin localization is independent of needle formation. These data indicate that, contrary to previous indications, correct insertion and function of EscC secretin in the outer membrane depends not only on thesec-dependent secretion pathway but also on other type III apparatus components.
Association ofActinobacillus pleuropneumoniaeCapsular Polysaccharide with Virulence in Pigs
Authors: Bandara Aloka B. , Lawrence Mark L. , Veit Hugo P. , Inzana Thomas J. 
Published: May 2003

ABSTRACTThe capsular polysaccharide (CP) ofActinobacillus pleuropneumoniaeis required for virulence of the bacteria in swine. However, a molecular investigation of whether the type or quantity of CP affectsA. pleuropneumoniaevirulence has not been reported. To initiate this investigation, a DNA region downstream of conserved genes required for CP export inA. pleuropneumoniaeserotype 1 was cloned and sequenced. Three open reading frames, designatedcps1A, cps1B,andcps1C, were identified that had amino acid homology to bacterial carbohydrate biosynthesis genes. A kanamycin resistance cassette (Kanr) was inserted into a 750-bp deletion spanningcps1ABor into a 512-bp deletion incps1Bonly, and the constructs were cloned in a suicide vector. The Kanrgene was then transferred into the chromosome of strain 4074 by homologous recombination to produce strain 4074Δcps1N and strain 4074Δcps1B, respectively. Strain 4074Δcps1N produced no detectable CP, but strain 4074Δcps1B made 15% of the serotype 1 CP made by the parent strain, 4074, as determined by enzyme-linked immunosorbent assay and precipitation of free CP. Thecps1ABCgenes of strain 4074 and thecps5ABCandcps5ABCDEgenes of serotype 5a strain J45 were cloned into the shuttle vector pLS88 and electroporated into 4074Δcps1N to produce 4074Δcps1N(pABcps101), 4074Δcps1N(pJMLcps53), and 4074Δcps1N(pABcps55), respectively. Strain 4074Δcps1N(pABcps101) produced about 33% of the serotype 1 CP produced by strain 4074. Strains 4074Δcps1N(pJMLcps53) and 4074Δcps1N(pABcps55) produced serotype 5a CP in similar quantity or in fourfold excess, respectively, to that produced by strain 4074. With intratracheal challenge in pigs at similar dosages, the order of virulence of strains producing serotype 1 CP (assessed by mortality, lung consolidation, hemorrhage, and fibrinous pleuritis) was the following: strain 4074 > strain 4074Δcps1N(pABcps101) ≥ strain 4074Δcps1N > strain 4074Δcps1B. Strain 4074Δcps1N(pJMLcps53) was less virulent than strain 4074Δcps1N(pABcps55). However, both strains produced serotype 5a CP in similar or greater quantities than was observed for production of serotype 1 CP by the parent strain, 4074, but were less virulent than the parent strain. Therefore, the amount of serotype 1 or 5a CP produced by isogenic strains ofA. pleuropneumoniaecorrelated with the virulence of the bacteria in pigs. However, virulence was also influenced by the type of CP produced or by its mechanism of expression.
Study of Capsular Polysaccharide from
Vibrio
parahaemolyticus
Authors: Hsieh Yu-Chi , Liang Shu-Mei , Tsai Wan-Ling , Chen Yee-Hsiung , Liu Teh-Yung , Liang Chi-Ming 
Published: May 2003

ABSTRACT

The leading cause of food poisoning in both Taiwan and Japan is
Vibrio
parahaemolyticus
infection, whose mechanism of enteropathogenesis is still unclear. To evaluate whether surface components are responsible for the intestinal adhesion of
V
.
parahaemolyticus
, we have developed a novel method for isolating the capsular polysaccharide (CPS) from
V
.
parahaemolyticus
(serotype O4:K8). We found that culturing of
V
.
parahaemolyticus
in broth for 1 week or more changed the colony form of the bacteria on an agar plate from opaque to translucent. The translucent colonies of
V
.
parahaemolyticus
contained little CPS and exhibited a much lower level of adherence to epithelial cells (Int-407) than the opaque colonies of the bacteria. Incubation of
V
.
parahaemolyticus
in medium supplemented with bile increased the levels of CPS and adherence. Treatment of
V
.
parahaemolyticus
with anti-CPS but not anti-LPS serum decreased the level of bacterial adherence. In addition, purified CPS bound to epithelial cells in a dose-dependent manner. Intranasal administration of CPS to mice in the presence of adjuvants such as immunostimulatory sequence oligodeoxynucleotides or cholera toxin elicited CPS-specific mucosal and systemic immune responses. These results indicate that CPS plays an important role in the adherence of
V
.
parahaemolyticus
to its target cells and may be considered a potential target for the development of a vaccine against this pathogen.
Differential Induction of Interleukin-10 and Interleukin-12 in Dendritic Cells by Microbial Toll-Like Receptor Activators and Skewing of T-Cell Cytokine Profiles
Authors: Qi Hai , Denning Timothy L. , Soong Lynn 
Published: May 2003

ABSTRACTDendritic cells (DCs) discriminate different microbial pathogens and induce T-cell responses of appropriate effector phenotypes accordingly. Microbial recognition and differentiation are mediated in part by pattern recognition receptors such as Toll-like receptors (TLRs), whereas the development of T-cell effector functions is critically dependent on DC-derived cytokines such as interleukin-12 (IL-12) and IL-10. However, it is not entirely clear to what extent various microbial TLR activators could induce different functional states of DCs that favor different T-cell effector phenotypes. Toward a better understanding of this issue, we examined IL-10 and IL-12 production and T-cell-polarizing potentials of murine bone marrow-derived DCs after stimulation by three microbial TLR activators, namely, lipopolysaccharide (LPS), peptidoglycan (PGN), and zymosan. We found that the three stimuli induced drastically different profiles of IL-10 and IL-12 production in DCs. Further, these stimuli differentially conditioned CD40-dependent IL-10 and IL-12 production by DCs. Finally, LPS-, PGN-, and zymosan-stimulated DCs primed distinct T-cell cytokine profiles. Our results support the notion that microbe-specific information sensed through different TLRs by DCs is linked to differential Th priming through DC-derived cytokines.
A Mosaic Pathogenicity Island Made Up of the Locus of Enterocyte Effacement and a Pathogenicity Island of
Escherichia
coli
O157:H7 Is Frequently Present in Attaching and Effacing
E
.
coli
Authors: Morabito Stefano , Tozzoli Rosangela , Oswald Eric , Caprioli Alfredo 
Published: May 2003

ABSTRACT

Enteropathogenic
Escherichia
coli
(EPEC) and enterohemorragic
E
.
coli
(EHEC) possess a pathogenicity island (PAI), termed the locus of enterocyte effacement (LEE), which confers the capability to cause the characteristic attaching and effacing lesions of the brush border. Due to this common property, these organisms are also termed attaching and effacing
E
.
coli
(AEEC). Sequencing of the EHEC O157 genome recently revealed the presence of other putative PAIs in the chromosome of this organism. In this article, we report on the presence of four of those PAIs in a panel of 133
E
.
coli
strains belonging to different pathogroups and serotypes. One of these PAIs, termed O122 in strain EDL 933 and SpLE3 in strain Sakai, was observed in most of the AEEC strains examined but not in the other groups of
E
.
coli
. It was also found to contain the virulence-associated gene
efa1
/
lifA
. In EHEC O157, PAI O122 is located 0.7 Mb away from the LEE. Conversely, we demonstrated that in many EHEC non-O157 strains and EPEC strains belonging to eight serogroups, PAI O122 and the LEE are physically linked to form a cointegrated structure. This structure can be considered a mosaic PAI that could have been acquired originally by AEEC. In some clones, such as EHEC O157, the LEE-O122 mosaic PAI might have undergone recombinational events, resulting in the insertion of the portion referred to as PAI O122 in a different location.
Structural and Functional Consequences of Cleavage of Human Secretory and Human Serum Immunoglobulin A1 by Proteinases from
Proteus
mirabilis
and
Neisseria
meningitidis
Authors: Almogren Adel , Senior Bernard W. , Loomes Lesley M. , Kerr Michael A. 
Published: May 2003

ABSTRACT

The cleavage of human serum monomeric immunoglobulin A1 (IgA1) and human secretory IgA1 (S-IgA1) by IgA1 proteinase of
Neisseria
meningitidis
and cleavage by the proteinase from
Proteus
mirabilis
have been compared. For serum IgA1, both proteinases cleaved only the α chain.
N
.
meningitidis
proteinase cleaved only in the hinge.
P
.
mirabilis
proteinase sequentially removed the tailpiece, the CH3 domain, and the CH2 domain. The cleavage of S-IgA1 by
N
.
meningitidis
proteinase occurred only in the hinge and was as rapid as that of serum IgA1.
P
.
mirabilis
proteinase predominantly cleaved the secretory component (SC) of S-IgA1. The SC of S-IgA1, whether cleaved or not, appeared to protect the α1 chain. Purified Fc fragment derived from the cleavage of serum IgA1 by
N
.
meningitidis
proteinase stimulated a respiratory burst in neutrophils through Fcα receptors, whereas the (Fcα1)
2
-SC fragment from digested S-IgA1 did not. The loss of the tailpiece from serum IgA1 treated with
P
.
mirabilis
proteinase had little effect, but the loss of the CH3 domain was concurrent with a rapid loss in the ability to bind to Fcα receptors. S-IgA1 treated with
P
.
mirabilis
proteinase under the same conditions retained the ability to bind to Fcα receptors. The results are consistent with the Fcα receptor binding site being at the CH2-CH3 interface. These data shed further light on the structure of S-IgA1 and indicate that the binding site for the Fcα receptor in S-IgA is protected by SC, thus prolonging its ability to activate phagocytic cells at the mucosal surface.
Helicobacter pylori
Infection Induces Interleukin-8 Receptor Expression in the Human Gastric Epithelium
Authors: Bäckhed Fredrik , Torstensson Elisabeth , Seguin Delphine , Richter-Dahlfors Agneta , Rokbi Bachra 
Published: May 2003

ABSTRACT

The gastric pathogen
Helicobacter pylori
is known to activate multiple proinflammatory signaling pathways in epithelial cells. In this study, we addressed the question of whether expression of the interleukin-8 receptors IL-8RA (CXCR1) and IL-8RB (CXCR2) is upregulated in
H. pylori
-infected human gastric biopsy samples. Biopsy samples from patients infected with
H. pylori
strains harboring the
cag
pathogenicity island (PAI) expressed larger amounts of both receptors. In addition, IL-8RB expression was induced in the gastric epithelial cell line AGS upon infection with a clinical isolate containing the
cag
PAI, while a strain lacking the
cag
PAI did not. Our finding suggests that gastric epithelial cells express IL-8R in response to
H. pylori
infection.