bluuebunny/crossref_metadata_2025_split huggingface dataset:
Aggregation Substance Promotes Adherence, Phagocytosis, and Intracellular Survival ofEnterococcus faecaliswithin Human Macrophages and Suppresses Respiratory Burst
Authors: Süßmuth Sigurd D. , Muscholl-Silberhorn Albrecht , Wirth Reinhard , Susa Milorad , Marre Reinhard , Rozdzinski Eva 
Published: July 2002

ABSTRACTThe aggregation substance (AS) ofEnterococcus faecalis, encoded on sex pheromone plasmids, is a surface-bound glycoprotein that mediates aggregation between bacteria thereby facilitating plasmid transfer. Sequencing of the pAD1-encoded Asa1 revealed that this surface protein contains two RGD motifs which are known to ligate integrins. Therefore, we investigated the influence of AS on the interaction ofE. faecaliswith human monocyte-derived macrophages which constitutively express β2integrins (e.g., CD18). AS was found to cause a greater-than-fivefold increase in enterococcal adherence to macrophages and a greater-than-sevenfold increase in phagocytosis. Adherence was mediated by an interaction between the RGD motif and the integrin CD11b/CD18 (complement receptor type 3) as demonstrated by inhibition studies with monoclonal antibodies and RGD peptide. AS-bearing enterococci were significantly more resistant to macrophage killing during the first 3 h postinfection, probably due to inhibition of the respiratory burst as indicated by reduced concentrations of superoxide anion.
Role of Ribosomal Protein L12 in Gonococcal Invasion of Hec1B Cells
Authors: Spence Janice M. , Clark Virginia L. 
Published: July 2002

ABSTRACT

Previous studies led to the development of a model of contact-induced enhanced gonococcal invasion of human reproductive cells that utilizes the lutropin receptor (LHr) as both the induction signal for conversion to this enhanced-gonococcal-invasion phenotype (Inv
+
GC) and as the specific Inv
+
GC uptake mechanism. This model proposes that gonococci express a surface feature that mimics human chorionic gonadotropin (hCG), the cognate ligand for LHr, and that this structure is responsible for the specific and productive interaction of GC with LHr. In this report, we identify a 13-kDa gonococcal protein with immunological similarities to hCG. The antiserum reactivity is specific since interaction with the 13-kDa gonococcal protein can be blocked by the addition of highly purified hCG. This gonococcal “hCG-like” protein, purified from two-dimensional gels and by immunoprecipitation, was determined by N-terminal sequencing to be the ribosomal protein L12. We present evidence that gonococcal L12 is membrane associated and surface exposed in gonococci, as shown by immunoblot analysis of soluble and insoluble gonococcal protein and antibody adsorption studies with fixed GC. Using highly purified recombinant gonococcal L12, we show that preincubation of Inv
−
GC with micromolar amounts of rL12 leads to a subsequent five- to eightfold increase in invasion of the human endometrial cell line, Hec1B. In addition, nanomolar concentrations of exogenous L12 inhibits gonococcal invasion to approximately 70% of the level in controls. Thus, we propose a novel cellular location for the gonococcal ribosomal protein L12 and concomitant function in LHr-mediated gonococcal invasion of human reproductive cells.
Enhancement of Neonatal Innate Defense: Effects of Adding an N-Terminal Recombinant Fragment of Bactericidal/Permeability-Increasing Protein on Growth and Tumor Necrosis Factor-Inducing Activity of Gram-Negative Bacteria Tested in Neonatal Cord Blood Ex Vivo
Authors: Levy Ofer , Sisson Richard B. , Kenyon Jonathan , Eichenwald Eric , Macone Ann B. , Goldmann Donald 
Published: July 2002

ABSTRACT

Innate defense against microbial infection requires the action of neutrophils, which have cytoplasmic granules replete with antibiotic proteins and peptides. Bactericidal/permeability-increasing protein (BPI) is found in the primary granules of adult neutrophils, has a high affinity for lipopolysaccharides (or “endotoxins”), and exerts selective cytotoxic, antiendotoxic, and opsonic activity against gram-negative bacteria. We have previously reported that neutrophils derived from newborn cord blood are deficient in BPI (O. Levy et al., Pediatrics 104:1327–1333, 1999). The relative deficiency in BPI of newborns raised the possibility that supplementing the levels of BPI in plasma might enhance newborn antibacterial defense. Here we determined the effects of addition of recombinant 21-kDa N-terminal BPI fragment (rBPI
21
) on the growth and tumor necrosis factor (TNF)-inducing activity of representative gram-negative clinical isolates. Bacteria were tested in citrated newborn cord blood or adult peripheral blood. Bacterial viability was assessed by plating assay, and TNF-α release was measured by enzyme-linked immunosorbent assay. Whereas adult blood limited the growth of all isolates except
Klebsiella pneumoniae
, cord blood also allowed logarithmic growth of
Escherichia coli
K1/r and
Citrobacter koseri
. Bacteria varied in their susceptibility to rBPI
21
's bactericidal action:
E. coli
K1/r was relatively susceptible (50% inhibitory concentration [IC
50
], ∼10 nM),
C. koseri
was intermediate (IC
50
, ∼1,000 nM),
Klebsiella pneumoniae
was resistant (IC
50
, ∼10,000 nM), and
Enterobacter cloacae
and
Serratia marcescens
were highly resistant (IC
50
, >10,000 nM). All isolates were potent inducers of TNF-α activity in both adult and newborn cord blood. In contrast to its variable antibacterial activity, rBPI
21
consistently inhibited the TNF-inducing activity of all strains tested (IC
50
, 1 to 1,000 nM). The antibacterial effects of rBPI
21
were additive with those of a combination of conventional antibiotics typically used to treat bacteremic newborns (ampicillin and gentamicin). Whereas ampicillin and gentamicin demonstrated little inhibition of bacterially induced TNF release, addition of rBPI
21
either alone or together with ampicillin and gentamicin profoundly inhibited release of this cytokine. Thus, supplementing newborn cord blood with rBPI
21
potently inhibited the TNF-inducing activity of a variety of gram-negative bacterial clinical pathogens and, in some cases, enhanced bactericidal activity. These results suggest that administration of rBPI
21
may be of clinical benefit to neonates suffering from gram-negative bacterial infection and/or endotoxemia.
Effect ofHelicobacter pylorion Polymorphonuclear Leukocyte Migration across Polarized T84 Epithelial Cell Monolayers: Role of Vacuolating Toxin VacA andcagPathogenicity Island
Authors: Hofman Véronique , Ricci Vittorio , Galmiche Antoine , Brest Patrick , Auberger Patrick , Rossi Bernard , Boquet Patrice , Hofman Paul 
Published: July 2002

ABSTRACTHelicobacter pyloriinfection can induce polymorphonuclear leukocyte (PMNL) infiltration of the gastric mucosa, which characterizes acute chronic gastritis. The mechanisms underlying this process are poorly documented. The lack of an in vitro model has considerably impaired the study of transepithelial migration of PMNL induced byH. pylori. In the present work, we used confluent polarized monolayers of the human intestinal cell line T84 grown on permeable filters to analyze the epithelial PMNL response induced by broth culture filtrates (BCFs) and bacterial suspensions from different strains ofH. pylori. We have evaluated the role of the vacuolating cytotoxin VacA and of thecagpathogenicity island (PAI) ofH. pyloriin PMNL migration via their effects on T84 epithelial cells. We noted no difference in the rates of PMNL transepithelial migration after epithelial preincubation with bacterial suspensions or with BCFs of VacA-negative or VacA-positiveH. pyloristrains. In contrast, PMNL transepithelial migration was induced after incubation of the T84 cells withcagPAI-positive andcagE-positiveH. pyloristrains. Finally, PMNL migration was correlated with a basolateral secretion of interleukin-8 by T84 cells, thus creating a subepithelial chemotactic gradient for PMNL. These data provide evidence that the vacuolating cytotoxin VacA is not involved in PMNL transepithelial migration and that thecagPAI, with a pivotal role for thecagEgene, provokes a transcellular signal across T84 monolayers, inducing a subepithelial PMNL response.
Evidence for Contribution of Tripartite Hemolysin BL, Phosphatidylcholine-Preferring Phospholipase C, and Collagenase to Virulence of
Bacillus cereus
Endophthalmitis
Authors: Beecher Douglas J. , Olsen Timothy W. , Somers Eileen B. , Wong Amy C. L. 
Published: July 2002

ABSTRACT

Bacillus cereus
causes a highly fulminant endophthalmitis which usually results in blindness. We previously concluded that hemolysin BL (HBL), a tripartite necrotizing pore-forming toxin, is a probable endophthalmitis virulence factor because it is highly toxic to retinal tissue in vitro and in vivo. We also determined that
B. cereus
produces additional retinal toxins that might contribute to virulence. Here we fractionated crude
B. cereus
culture supernatant by anion-exchange chromatography and found that in vitro retinal toxicity was also associated with phosphatidylcholine-preferring phospholipase C (PC-PLC). The pure enzyme also caused retinal necrosis in vivo. We showed that phosphatidylinositol-specific PLC and sphingomyelinase were nontoxic and that two hemolysins, cereolysin O and a novel hemolysin designated hemolysin IV, were marginally toxic in vitro. The histopathology of experimental septic endophthalmitis in rabbits mimicked the pathology produced by pure HBL, and both HBL and PC-PLC were detected at toxic concentrations in infected vitreous fluid. Bacterial cells were first seen associated with the posterior margin of the lens and eventually were located throughout the lens cortex. Detection of collagenase in the vitreous humor suggested that infiltration was facilitated by the breakdown of the protective collagen lens capsule by that enzyme. This work supports our conclusion that HBL contributes to
B. cereus
virulence and implicates PC-PLC and collagenase as additional virulence factors.
Locus of Enterocyte Effacement from
Citrobacter rodentium
: Sequence Analysis and Evidence for Horizontal Transfer among Attaching and Effacing Pathogens
Authors: Deng Wanyin , Li Yuling , Vallance Bruce A. , Finlay B. Brett 
Published: July 2002

ABSTRACT

The family of attaching and effacing (A/E) bacterial pathogens, which includes diarrheagenic enteropathogenic
Escherichia coli
(EPEC) and enterohemorrhagic
E
.
coli
(EHEC), remains a significant threat to human and animal health. These bacteria intimately attach to host intestinal cells, causing the effacement of brush border microvilli. The genes responsible for this phenotype are encoded in a pathogenicity island called the locus of enterocyte effacement (LEE).
Citrobacter rodentium
is the only known murine A/E pathogen and serves as a small animal model for EPEC and EHEC infections. Here we report the full DNA sequence of
C
.
rodentium
LEE and provide a comparative analysis with the published LEEs from EPEC, EHEC, and the rabbit diarrheagenic
E
.
coli
strain RDEC-1. Although
C
.
rodentium
LEE shows high similarities throughout the entire sequence and shares all 41 open reading frames with the LEE from EPEC, EHEC, and RDEC-1, it is unique in its location of the
rorf1
and
rorf2/espG
genes and the presence of several insertion sequences (IS) and IS remnants. The LEE of EPEC and EHEC is inserted into the
selC
tRNA gene. In contrast, the
Citrobacter
LEE is flanked on one side by an operon encoding an ABC transport system, and an IS element and sequences homologous to
Shigella
plasmid R100 and EHEC pO157 flank the other. The presence of plasmid sequences next to
C
.
rodentium
LEE suggests that the prototype LEE resided on a horizontally transferable plasmid. Additional sequence analysis reveals that the 3-kb plasmid in
C
.
rodentium
is nearly identical to p9705 in EHEC O157:H7, suggesting that horizontal plasmid transfer among A/E pathogens has occurred. Our results indicate that the LEE has been acquired by
C
.
rodentium
and A/E
E
.
coli
strains independently during evolution.
Patterns of Chemokine Expression in Models ofSchistosoma mansoniInflammation and Infection Reveal Relationships between Type 1 and Type 2 Responses and Chemokines In Vivo
Authors: Park Matthew K. , Hoffmann Karl F. , Cheever Allen W. , Amichay Doron , Wynn Thomas A. , Farber Joshua M. 
Published: July 2002

ABSTRACTTo explore the roles of chemokines in type 1 and type 2 responses in vivo, we examined mRNA expression for a panel of up to 17 chemokines in experimental mouse models usingSchistosoma mansoni. These studies revealed that Mig (monokine induced by gamma interferon), cytokine-responsive gene 2/10-kDa interferon-inducible protein, RANTES, lymphotactin, macrophage inflammatory protein 1β (MIP-1β), JE/monocyte chemoattractant protein 1, and MIP-2 are associated with type 1 egg-induced responses and that thymus-derived chemotactic agent 3 (TCA3), eotaxin, MIP-1α, and MIP-1γ are associated with type 2 egg-induced responses. After cercarial infection, both type 1-associated and type 2-associated chemokines were elevated in the livers of infected mice presensitized with eggs and recombinant interleukin-12 (rIL-12), a regimen that diminishes pathology. Neutralization of IL-12 or gamma interferon during egg deposition reversed the effects of prior treatment with rIL-12, leading to a return to larger granulomas; persistently elevated expression of TCA3, eotaxin, and MIP-1α; and a marked reduction in the expression of type 1-associated chemokines despite the maintenance of a dominant type 1 cytokine response in the draining lymph nodes. Our findings suggest that there are patterns of coordinate chemokine expression characteristic of type 1 and type 2 responses in vivo; that the cells recruited by a given pattern of chemokines may differ, depending on the composition of peripheral populations; and that patterns of tissue expression of chemokines may determine the character of an inflammatory response independently of the dominant pattern of differentiation of antigen-specific T cells. Our data reveal new relationships between chemokines and polarized immune responses and suggest that end organ inflammation might be altered by chemokine blockade without necessitating reversal of the phenotype of the majority of differentiated T cells.
Different Type 1 Fimbrial Genes and Tropisms of Commensal and Potentially Pathogenic
Actinomyces
spp. with Different Salivary Acidic Proline-Rich Protein and Statherin Ligand Specificities
Authors: Li Tong , Khah Massoud Kheir , Slavnic Snjezana , Johansson Ingegerd , Strömberg Nicklas 
Published: July 2002

ABSTRACT

Actinomyces
spp. exhibit type 1 fimbria-mediated adhesion to salivary acidic proline-rich proteins (PRPs) and statherin ligands.
Actinomyces
spp. with different animal and tissue origins belong to three major adhesion types as relates to ligand specificity and type 1 fimbria genes. (i) In preferential acidic-PRP binding, strains of
Actinomyces naeslundii
genospecies 1 and 2 from human and monkey mouths displayed at least three ligand specificities characterized by preferential acidic-PRP binding. Slot blot DNA hybridization showed seven highly conserved type 1 fimbria genes (
orf1
- to -
6
and
fimP
) in genospecies 1 and 2 strains, except that
orf5
and
orf3
were divergent in genospecies 1. (ii) In preferential statherin binding, oral
Actinomyces viscosus
strains of rat and hamster origin (and strain 19246 from a human case of actinomycosis) bound statherin preferentially. DNA hybridization and characterization of the type 1 fimbria genes from strain 19246 revealed a homologous gene cluster of four open reading frames (
orfA
to -
C
and
fimP
). Bioinformatics suggested sortase (
orfB
,
orf4
, and part of
orf5
), prepilin peptidase (
orfC
and
orf6
), fimbria subunit (
fimP
), and usher- and autotransporter-like (
orfA
and
orf1
to -
3
) functions. Those gene regions corresponding to
orf3
and
orf5
were divergent, those corresponding to
orf2
,
orf1
, and
fimP
were moderately conserved, and those corresponding to
orf4
and
orf6
were highly conserved. Restriction fragment length polymorphism analyses using a
fimP
probe separated human and monkey and rat and hamster strains into phylogenetically different groups. (iii) In statherin-specific binding, strains of
A. naeslundii
genospecies 1 from septic and other human infections displayed a low-avidity binding to statherin. Only the
orf4
and
orf6
gene regions were highly conserved. Finally, rat saliva devoid of statherin bound bacterial strains avidly irrespective of ligand specificity, and specific antisera detected either type 1, type 2, or both types of fimbria on the investigated
Actinomyces
strains.
Bacterial Fimbriae and Their Peptides Activate Human Gingival Epithelial Cells through Toll-Like Receptor 2
Authors: Asai Yasuyuki , Ohyama Yoshinori , Gen Keika , Ogawa Tomohiko 
Published: July 2002

ABSTRACTGingival epithelial cells are a central component of the barrier between oral microflora and internal tissues. Host responses to periodontopathic bacteria and surface components containing fimbriae are thought to be important in the development and progression of periodontal diseases. To elucidate this mechanism, we established immortalized human gingival epithelial cells (HGEC) that were transfected with human papillomavirus. HGEC predominantly expressed Toll-like receptor (TLR) 2, but not TLR4 or CD14. They also induced interleukin-8 (IL-8) production when stimulated withPorphyromonas gingivalisfimbriae andStaphylococcus aureuspeptidoglycan, but notEscherichia coli-type synthetic lipid A. Furthermore, an active synthetic peptide composed of residues 69 to 73 (ALTTE) of the fimbrial subunit protein, derived fromP. gingivalisand similar to a common component of cell wall peptidoglycans in parasitic bacteria,N-acetylmuramyl-l-alanyl-d-isoglutamine (MDP), significantly induced IL-8 production and NF-κB activation in HGEC, and these cytokine-producing activities were augmented by a complex of soluble CD14 and lipopolysaccharide-binding protein (LBP). IL-8 production in HGEC stimulated with these bacterial components was clearly inhibited by mouse monoclonal antibody to human TLR2. These findings suggest thatP. gingivalisfimbrial protein and its active peptide are capable of activating HGEC through TLR2.
NovelSalmonella entericaSerovar Typhimurium Protein That Is Indispensable for Virulence and Intracellular Replication
Authors: van der Straaten Tahar , van Diepen Angela , Kwappenberg Kitty , van Voorden Sjaak , Franken Kees , Janssen Riny , Kusters Johannes G. , Granger Donald L. , van Dissel Jaap T. 
Published: July 2002

ABSTRACTUpon contact with host cells, the intracellular pathogenSalmonella entericaserovar Typhimurium promotes its uptake, targeting, and survival in intracellular niches. In this process, the bacterium evades the microbicidal effector mechanisms of the macrophage, including oxygen intermediates. This study reports the phenotypic and genotypic characterization of anS. entericaserovar Typhimurium mutant that is hypersusceptible to superoxide. The susceptible phenotype is due to a MudJ insertion-inactivation of a previously undescribedSalmonellagene designatedsspJthat is located between 54.4 and 64 min of theSalmonellachromosome and encodes a 392-amino-acid protein. In vivo, upon intraperitoneal injection of 104to 107bacteria in C3H/HeN and 101to 104bacteria in BALB/c mice, the mutant strain was less virulent than the wild type. Consistent with this finding, during the first hour after ingestion by macrophage-like J774 and RAW264.7 cells in vitro, the intracellular killing of the strain carryingsspJ::MudJ is enhanced fivefold over that of wild-type microorganisms. Wild-type salmonellae displayed significant intracellular replication during the first 24 h after uptake, butsspJ::MudJ mutants failed to do so. This phenotype could be restored to that of the wild type bysspJcomplementation. The SspJ protein is found in the cytoplasmic membrane and periplasmic space. Amino acid sequence homology analysis did reveal a leader sequence and putative pyrroloquinoline quinone-binding domains, but no putative protein function. We excluded the possibility that SspJ is a scavenger of superoxide or has superoxide dismutase activity.
Enteropathogenic
Escherichia coli
(EPEC) Tir Receptor Molecule Does Not Undergo Full Modification When Introduced into Host Cells by EPEC-Independent Mechanisms
Authors: Kenny Brendan , Warawa Jonathan 
Published: July 2002

ABSTRACT

Enteropathogenic
Escherichia coli
(EPEC), like many other gram-negative pathogens, encodes a type III secretion apparatus dedicated to the release of virulence-associated proteins. One such protein, Tir, is translocated into host cells, where it is modified by the addition of phosphate groups, resulting in a number of species with distinct molecular mass. One phosphorylation event, on tyrosine residue 474 of Tir, does not contribute to shifts in molecular mass but is essential for its actin-nucleating function. The role of the nonphosphotyrosine related modifications is unknown. In this paper, we demonstrate, using three different approaches, that Tir does not encode sufficient information to facilitate its complete modification when introduced into host cells in EPEC-independent mechanisms. Each system revealed that Tir is a substrate for a host kinase whose action results in its partial modification to a form similar to one evident in EPEC-infected host cells. Further Tir modification could not be induced by infecting cells with EPEC, suggesting that Tir must be coexpressed with other EPEC factors to enable its full modification within host cells. One approach used
Yersinia
spp. to deliver Tir into host cells, and this system revealed that Tir secretion and translocation can occur in the absence of the Tir chaperone molecule, CesT (formerly known as OrfU). CesT was found to be an efficiency factor which was not required, unlike in EPEC, for Tir stability, indicating that it may function to guide Tir to the translocation apparatus or maintain it in a secretion-competent form.