bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Major Secreted Elastase Is Essential for Pathogenicity of
Aeromonas hydrophila
Authors: Cascón Alberto , Yugueros Javier , Temprano Alejandro , Sánchez María , Hernanz Carmen , Luengo José María , Naharro Germán 
Published: July 2002

ABSTRACT

Aeromonas hydrophila
is an opportunistic pathogen and the leading cause of fatal hemorrhagic septicemia in rainbow trout. A gene encoding an elastolytic activity,
ahyB
, was cloned from
Aeromonas hydrophila
AG2 into pUC18 and expressed in
Escherichia coli
and in the nonproteolytic species
Aeromonas salmonicida
subsp.
masoucida
. Nucleotide sequence analysis of the
ahyB
gene revealed an open reading frame of 1,764 nucleotides with coding capacity for a 588-amino-acid protein with a molecular weight of 62,728. The first 13 N-terminal amino acids of the purified protease completely match those deduced from DNA sequence starting at AAG (Lys-184). This finding indicated that AhyB is synthesized as a preproprotein with a 19-amino-acid signal peptide, a 164-amino-acid N-terminal propeptide, and a 405-amino-acid intermediate which is further processed into a mature protease and a C-terminal propeptide. The protease hydrolyzed casein and elastin and showed a high sequence similarity to other metalloproteases, especially with the mature form of the
Pseudomonas aeruginosa
elastase (52% identity),
Helicobacter pylori
zinc metalloprotease (61% identity), or proteases from several species of
Vibrio
(52 to 53% identity). The gene
ahyB
was insertionally inactivated, and the construct was used to create an isogenic
ahyB
mutant of
A. hydrophila
. These first reports of a defined mutation in an extracellular protease of
A. hydrophila
demonstrate an important role in pathogenesis.
A Model for Sequestration of the Transmission Stages ofPlasmodium falciparum: Adhesion of Gametocyte-Infected Erythrocytes to Human Bone Marrow Cells
Authors: Rogers Nicola J. , Hall Belinda S. , Obiero Jacktone , Targett Geoffrey A. T. , Sutherland Colin J. 
Published: July 2002

ABSTRACTWith the aim of developing an appropriate in vitro model of the sequestration of developingPlasmodium falciparumsexual-stage parasites, we have investigated the cytoadherence of gametocytes to human bone marrow cells of stromal and endothelial origin. Developing stage III and IV gametocytes, but not mature stage V gametocytes, adhere to bone marrow cells in significantly higher densities than do asexual-stage parasites, although these adhesion densities are severalfold lower than those encountered in classical CD36-dependent assays ofP. falciparumcytoadherence. This implies that developing gametocytes undergo a transition from high-avidity, CD36-mediated adhesion during stages I and II to a lower-avidity adhesion during stages III and IV. We show that this adhesion is CD36 independent, fixation sensitive, stimulated by tumor necrosis factor alpha, and dependent on divalent cations and serum components. These data suggest that gametocytes and asexual parasites utilize distinct sets of receptors for adhesion during development in their respective sequestered niches. To identify receptors for gametocyte-specific adhesion of infected erythrocytes to bone marrow cells, we tested a large panel of antibodies for the ability to inhibit cytoadherence. Our results implicate ICAM-1, CD49c, CD166, and CD164 as candidate bone marrow cell receptors for gametocyte adhesion.
Construction and Phenotypic Evaluation of aVibrio vulnificus vvpEMutant for Elastolytic Protease
Authors: Jeong Kwang Cheol , Jeong Hye Sook , Rhee Joon Haeng , Lee Shee Eun , Chung Sun Sik , Starks Angela M. , Escudero Gloria M. , Gulig Paul A. , Choi Sang Ho 
Published: July 2002

ABSTRACTVibrio vulnificusis an opportunistic gram-negative pathogen that commonly contaminates oysters. Predisposed individuals who consume raw oysters can die within days from sepsis, and even otherwise healthy people are susceptible to serious wound infection after contact with contaminated seafood or seawater. Numerous secreted and cell-associated virulence factors have been proposed to account for the fulminating and destructive nature ofV. vulnificusinfections. Among the putative virulence factors is an elastolytic metalloprotease. We cloned and sequenced thevvpEgene encoding an elastase ofV. vulnificusATCC 29307. The functions of the elastase were assessed by constructingvvpEinsertional knockout mutants and evaluating phenotypic changes in vitro and in mice. Although other types of protease activity were still observed invvpEmutants, elastase activity was completely absent in the mutants and was restored by reintroducing the recombinantvvpEgene. In contrast to previous characterization of elastase as a potential virulence factor, which was demonstrated by injecting the purified protein into animals, inactivation of theV. vulnificus vvpEgene did not affect the ability of the bacteria to infect mice and cause damage, either locally in subcutaneous tissues or systemically in the liver, in both iron-treated and normal mice. Furthermore, avvpEmutant was not affected with regard to cytolytic activity toward INT407 epithelial cells or detachment of INT407 cells from culture dishes in vitro. Therefore, it appears that elastase is less important in the pathogenesis ofV. vulnificusthan would have been predicted by examining the effects of administering purified proteins to animals. However,V. vulnificusutilizes a variety of virulence factors; hence, the effects of inactivation of elastase alone could be masked by other compensatory virulence factors.
Induction of Interleukin-4 (IL-4) byLegionella pneumophilaInfection in BALB/c Mice and Regulation of Tumor Necrosis Factor Alpha, IL-6, and IL-1β
Authors: Newton Catherine , McHugh Shannon , Widen Ray , Nakachi Noriya , Klein Thomas , Friedman Herman 
Published: July 2002

ABSTRACTInfection of BALB/c mice with a sublethal concentration ofLegionella pneumophilacauses an acute disease that is resolved by innate immune responses. The infection also initiates the development of adaptive Th1 responses that protect the mice from challenge infections. To study the early responses, cytokines induced during the first 24 h after infection were examined. In the serum, interleukin-12 (IL-12) was detectable by 3 h and peaked at 10 h, while gamma interferon was discernible by 5 h and peaked at 8 h. Similar patterns were observed in ex vivo cultures of splenocytes. A transient IL-4 response was also detected by 3 h postinfection in ex vivo cultures. BALB/c IL-4-deficient mice were more susceptible toL. pneumophilainfection than were wild-type mice. The infection induced higher serum levels of acute-phase cytokines (tumor necrosis factor alpha [TNF-α], IL-1β, and IL-6), and reducing TNF-α levels with antibodies protected the mice from death. Moreover, the addition of IL-4 toL. pneumophila-infected macrophage cultures suppressed the production of these cytokines. Thus, the lack of IL-4 in the deficient mice resulted in unchecked TNF-α production, which appeared to cause the mortality. Monocyte chemoattractant protein-1 (MCP-1), a chemokine that is induced by IL-4 duringListeria monocytogenesinfection, was detected at between 2 and 30 h after infection. However, MCP-1 did not appear to be induced by IL-4 or to be required for the TNF-α regulation by IL-4. The data suggest that the early increase in IL-4 serves to regulate the mobilization of acute phase cytokines and thus controls the potential harmful effects of these cytokines.
Restriction ofToxoplasma gondiiGrowth in Human Brain Microvascular Endothelial Cells by Activation of Indoleamine 2,3-Dioxygenase
Authors: Däubener Walter , Spors Birgit , Hucke Christian , Adam Rüdiger , Stins Monique , Kim Kwang Sik , Schroten Horst 
Published: July 2002

ABSTRACTOne of the first steps in the development of cerebral toxoplasmosis is the penetration of the blood-brain barrier, which is comprised of microvascular endothelial cells. We examined the capacity of human brain microvascular endothelial cells (HBMEC) to interact withToxoplasma gondii. We found that stimulation of HBMEC with gamma interferon (IFN-γ) resulted in the induction of toxoplasmostasis. The capacity of HBMEC to restrictToxoplasmagrowth after IFN-γ stimulation was enhanced in the presence of tumor necrosis factor alpha (TNF-α). In addition, we found that IFN-γ induced a strong induction of indoleamine 2,3-dioxygenase (IDO) activity in HBMEC, and this enzyme activity was enhanced by costimulation with TNF-α. The addition of excess amounts of tryptophan to the HBMEC cultures resulted in a complete abrogation of the IFN-γ–TNF-α-mediated toxoplasmostasis. We therefore conclude that IDO induction contributed to the antiparasitic effector mechanism inducible in HBMEC by IFN-γ and TNF-α.
Enteropathogenic
Escherichia
coli
Virulence Factor Bundle-Forming Pilus Has a Binding Specificity for Phosphatidylethanolamine
Authors: Khursigara C. , Abul-Milh M. , Lau B. , Girón J. A. , Lingwood C. A. , Foster D. E. Barnett 
Published: July 2002

ABSTRACT

The bundle-forming pilus (BFP) of enteropathogenic
Escherichia
coli
(EPEC), an established virulence factor encoded on the EPEC adherence factor (EAF) plasmid, has been implicated in the formation of bacterial autoaggregates and in the localized adherence of EPEC to cultured epithelial cells. While understanding of the pathogenic mechanism of this organism is rapidly improving, a receptor ligand for BFP has not yet been identified. We now report, using both solid-phase and liposome binding assays, that BFP expression correlates with phosphatidylethanolamine (PE) binding. In a thin-layer chromatogram overlay assay, specific recognition of PE was documented for BFP-expressing strains, including E2348/69, a wild-type EPEC clinical isolate, as well as a laboratory strain, HB101, transformed with a
bfp
-carrying plasmid. Strains which did not express BFP did not bind PE, including a
bfpA
disruptional mutant of E2348/69, EAF plasmid-cured E2348/69, and HB101. E2348/69 also aggregated PE-containing liposomes but not phosphatidylcholine- or phosphatidylserine-containing liposomes, while BFP
-
negative strains did not produce aggregates with any tested liposomes. Purified BFP preparations bound commercial PE standards as well as a PE-containing band within lipid extracts from human epithelial cells and from E2348/69. Our results therefore indicate a specific interaction between BFP and PE and suggest that PE may serve as a BFP receptor for bacterial autoaggregation and may promote localized adherence to host cells, both of which contribute to bacterial pathogenesis.
Analysis of Cytokines in the Early Development of Gastric Secondary Lymphoid Follicles inHelicobacter pylori-Infected BALB/c Mice with Neonatal Thymectomy
Authors: Uchida Kazushige , Okazaki Kazuichi , Debrecceni Andras , Nishi Toshiki , Iwano Hirosi , Inai Maki , Uose Suguru , Nakase Hiroshi , Ohana Masaya , Oshima Chikashi , Matsushima Yumi , Kawanami Chiharu , Hiai Hiroshi , Masuda Toru , Chiba Tsutomu 
Published: July 2002

ABSTRACTImmunological interaction between the host andHelicobacter pyloriseems to play a critical role in follicular formation in gastric mucosa. We reportedH. pylori-induced follicular gastritis model using neonatally thymectomized mice. In this study, we investigated the involvement of various cytokines in this model. BALB/c mice were thymectomized on the third day after birth (nTx). At 6 weeks old, these mice were orally infected withH. pylori. Histological studies showed that follicular formation occurred from 8 weeks after the infection and that most of the infiltrating lymphocytes were CD4+and B cells. Neutrophils increased transiently at 1 week after the infection. Gamma interferon, interleukin-7 (IL-7), and IL-7 receptor were expressed in the stomach of the nTx mice irrespective of the infection. In contrast, expressions of the tumor necrosis factor alpha, IL-4 and lymphotoxin-α genes were remarkably upregulated by the infection. Our findings suggest that follicular formation may require cooperative involvement of a Th2-type immune response, tumor necrosis factor alpha and lymphotoxin-α in addition to the Th1-type immune response inH. pylori-induced gastritis in nTx mice.
Role for Inducible Nitric Oxide Synthase in Protection from ChronicChlamydia trachomatisUrogenital Disease in Mice and Its Regulation by Oxygen Free Radicals
Authors: Ramsey K. H. , Sigar I. M. , Rana S. V. , Gupta J. , Holland S. M. , Byrne G. I. 
Published: July 2002

ABSTRACTIt has been previously reported that although inducible nitric oxide synthase (iNOS) gene knockout (NOS2−/−) mice resolveChlamydia trachomatisgenital infection, the production of reactive nitrogen species (RNS) via iNOS protects a significant proportion of mice from hydrosalpinx formation and infertility. We now report that higher in vivo RNS production correlates with mouse strain-related innate resistance to hydrosalpinx formation. We also show that mice with a deletion of a key component of phagocyte NADPH oxidase (p47phox−/−) resolve infection, produce greater amounts of RNS in vivo, and sustain lower rates of hydrosalpinx formation than both wild-type (WT)NOS2+/+andNOS2−/−controls. When we induced an in vivo chemical block in iNOS activity in p47phox−/−mice usingNG-monomethyl-l-arginine (L-NMMA), a large proportion of these mice eventually succumbed to opportunistic infections, but not before they resolved their chlamydial infections. Interestingly, when compared to WT and untreated p47phox−/−controls, L-NMMA-treated p47phox−/−mice resolved their infections more rapidly. However, L-NMMA-treated p47phox−/−mice lost resistance to chronic chlamydial disease, as evidenced by an increased rate of hydrosalpinx formation that was comparable to that forNOS2−/−mice. We conclude that phagocyte oxidase-derived reactive oxygen species (ROS) regulate RNS during chlamydial urogenital infection in the mouse. We further conclude that while neither phagocyte oxidase-derived ROS nor iNOS-derived RNS are essential for resolution of infection, RNS protect from chronic chlamydial disease in this model.
Complete Nucleotide Sequence of a
Staphylococcus aureus
Exfoliative Toxin B Plasmid and Identification of a Novel ADP-Ribosyltransferase, EDIN-C
Authors: Yamaguchi Takayuki , Hayashi Tetsuya , Takami Hideto , Ohnishi Makoto , Murata Takahiro , Nakayama Keisuke , Asakawa Kayo , Ohara Masaru , Komatsuzawa Hitoshi , Sugai Motoyuki 
Published: July 2002

ABSTRACT

The complete nucleotide sequence of pETB, a 38.2-kb
Staphylococcus aureus
plasmid encoding the exfoliative toxin B (ETB), was determined. A total of 50 open reading frames were identified on the plasmid genome and, among these, 32 showed sequence similarity to known proteins. pETB contains three copies of IS
257
, which divide the pETB genome into three regions: (i) a cadmium resistance operon-containing region, (ii) a lantibiotic production gene-containing region, and (iii) the remaining part where genes for plasmid replication and/or maintenance are dispersed. In the third region, genes of various kinds of functions are present among the replication- and maintenance-related genes. They include two virulence-related genes, the
etb
gene and a gene encoding a novel ADP-ribosyltransferase closely related to EDIN, which belongs to the C3 family of ADP-ribosyltransferases modifying Rho GTPases. They also include genes for a cell wall-anchoring surface protein and a phage resistance protein. Based on the determined sequence of pETB, the genome structures of
etb
-bearing plasmids (ETB plasmids) from various clinical isolates were analyzed by the PCR scanning method. The data indicate that, although the ETB plasmids are highly heterogeneous in genome size, the fundamental genome organization is well conserved. The size variation of the plasmid is mainly attributed to defined regions which may be hot spots for gene shuffling.
Blockade of Caspases Inhibits Amebic Liver Abscess Formation in a Mouse Model of Disease
Authors: Yan Le , Stanley Samuel L. 
Published: July 2002

ABSTRACT

We looked at the effect of inhibiting caspases on amebic liver abscess in the mouse model of infection. A dose of the pan-caspase inhibitor benzyloxycarbonyl-V-A-D-O-methyl fluoromethyl ketone (Z-VAD-FMK; R & D Systems) given to SCID mice 2 h prior to direct hepatic inoculation with
Entamoeba histolytica
trophozoites, and 12 h after amebic inoculation, reduced the mean liver abscess size by 70% at 24 h compared to a control group. These data indicate that apoptosis plays a significant but not an exclusive role in amebic liver abscess formation in the mouse model.
Biofilm Formation in a Hydrodynamic Environment by Novel FimH Variants and Ramifications for Virulence
Authors: Schembri Mark A. , Klemm Per 
Published: July 2002

ABSTRACT

Type 1 fimbriae are surface-located adhesion organelles of
Escherichia coli
that are directly associated with virulence of the urinary tract. They mediate
d
-mannose-sensitive binding to different host surfaces by way of the minor fimbrial component FimH. Naturally occurring variants of FimH that bind strongly to terminally exposed monomannose residues have been associated with a pathogenicity-adaptive phenotype that enhances
E. coli
colonization of extraintestinal locations such as the urinary tract. The FimH adhesin also promotes biofilm formation in a mannose-inhibitable manner on abiotic surfaces under static growth conditions. In this study, we used random mutagenesis combined with a novel selection-enrichment technique to specifically identify mutations in the FimH adhesin that confer on
E. coli
the ability to form biofilms under hydrodynamic flow (HDF) conditions. We identified three FimH variants from our mutant library that could mediate an HDF biofilm formation phenotype to various degrees. This phenotype was induced by the cumulative effect of multiple changes throughout the receptor-binding region of the protein. Two of the HDF biofilm-forming FimH variants were insensitive to mannose inhibition and represent novel phenotypes not previously identified in naturally occurring isolates. Characterization of our enriched clones revealed some similarities to amino acid alterations that occur in urinary tract infection (UTI) strains. Subsequent screening of a selection of UTI FimH variants demonstrated that they too could promote biofilm formation on abiotic surfaces under HDF conditions. Interestingly, the same correlation was not observed for commensal FimH variants. FimH is a multifaceted protein prone to rapid microevolution. In addition to its previously documented roles in adherence and invasion, we have now demonstrated its function in biofilm formation on abiotic surfaces subjected to HDF conditions. The study indicates that UTI FimH variants possess adaptations that enhance biofilm formation and suggests a novel role for FimH in UTIs associated with medical implants such as catheters.
Marrow-Derived CD40-Positive Cells Are Required for Mice To ClearCryptosporidium parvumInfection
Authors: Hayward Anthony R. , Cosyns Mary , Jones Michelle , Ponnuraj Esther M. 
Published: July 2002

ABSTRACTTo clear aCryptosporidium parvuminfection, mice need CD4+T cells, major histocompatibility complex class II, and an intact CD40-CD154 signaling pathway. CD40 is constitutively expressed on marrow-derived cells such as dendritic cells and B lymphocytes and is induced by gamma interferon (IFN-γ) on most somatic cells. To determine whether the CD40 needed to clear aC. parvuminfection has to be on marrow-derived mononuclear cells or on the epithelial cells that normally harbor the parasite, we transplanted CD40−/−mice with CD40+/−bone marrow and then infected them withC. parvum. These chimeras cleared theC. parvuminfection, while CD40+/−controls transplanted with CD40−/−marrow cells remained infected. CD40 expression on marrow-derived cells therefore suffices for aC. parvuminfection to be cleared, while CD40 expression on intestinal epithelial cells is not sufficient. There was no difference between the acquisition of CD69 and CD154 by mesenteric lymph node T cells ofC. parvum-infected animals with intact or disrupted CD40-CD154 pathways. CD4 T cells entered the intestinal laminae propriae ofC. parvum-infected animals whether or not the CD40 genes of these recipients were intact. These results suggest that, for aC. parvuminfection to be cleared, CD40 is not necessary for T-cell activation but may instead contribute to an effector pathway of marrow-derived cells.
Lactoferrin Peptide Increases the Survival of
Candida albicans
- Inoculated Mice by Upregulating Neutrophil and Macrophage Functions, Especially in Combination with Amphotericin B and Granulocyte-Macrophage Colony-Stimulating Factor
Authors: Tanida Toyohiro , Rao Fu , Hamada Toshihiro , Ueta Eisaku , Osaki Tokio 
Published: July 2002

ABSTRACT

To develop a new strategy to control candidiasis, we examined in vivo the anticandidal effects of a synthetic lactoferrin peptide, FKCRRWQWRM (peptide 2) and the peptide that mimics it, FKARRWQWRM (peptide 2′). Although all mice that underwent intraperitoneal injection of 5 × 10
8
Candida
cells with or without peptide 2′ died within 8 or 7 days, respectively, the survival times of mice treated with 5 to 100 μg of intravenous peptide 2 per day for 5 days after the candidal inoculation were prolonged between 8.4 ± 2.9 and 22.4 ± 3.6 days, depending on the dose of peptide 2. The prolongation of survival by peptide 2 was also observed in mice that were infected with 1.0 × 10
9
Candida albicans
cells (3.2 ± 1.3 days in control mice versus 8.2 ± 2.4 days in the mice injected with 10 μg of peptide 2 per day). In the high-dose inoculation, a combination of peptide 2 (10 μg/day) with amphotericin B (0.1 μg/day) and granulocyte-macrophage colony-stimulating factor (GM-CSF) (0.1 μg/day) brought prolonged survival. With a combination of these agents, 60% of the mice were alive for more than 22 days. Correspondingly, peptide 2 activated phagocytes inducing inducible NO synthase and the expression of p47
phox
and p67
phox
, and peptide 2 increased phagocyte
Candida
-killing activities up to 1.5-fold of the control levels upregulating the generation of superoxide, lactoferrin, and defensin from neutrophils and macrophages. These findings indicated that the anticandidal effects of peptide 2 depend not only on the direct
Candida
cell growth-inhibitory activity, but also on the phagocytes' upregulatory activity, and that combinations of peptide 2 with GM-CSF and antifungal drugs will help in the development of new strategies for control of candidiasis.