bluuebunny/crossref_metadata_2025_split huggingface dataset:
Necrotic Death ofRhodococcus equi-Infected Macrophages Is Regulated by Virulence-Associated Plasmids
Authors: Lührmann Anja , Mauder Norman , Sydor Tobias , Fernandez-Mora Eugenia , Schulze-Luehrmann Jan , Takai Shinji , Haas Albert 
Published: January 2004

ABSTRACTRhodococcus equiis a gram-positive intracellular pathogen that can cause severe bronchopneumonia in foals and AIDS patients. It has been reported that advanced infection of foals is characterized by tissue necrosis, coinciding with the presence of degenerate bacteria-laden macrophages. Here, we report that the possession of the VapA-expressing plasmid, which has been previously correlated with a high level of virulence for foals and mice, strongly increases cytotoxicity ofR. equifor murine macrophage-like (J774E) cells. Isolates containing different, VapB-expressing plasmids are less virulent and also have a lower cytotoxic potential. Isogenic strains lacking either plasmid are avirulent and have a very low cytotoxic potential. We show, using fluorescence-activated cell sorter analysis (annexin V/7-amino-actinomycin D and sub-G1-analysis), Western blotting [poly(ADP-ribose) polymerase processing analysis], and electron microscopy (macrophage and nucleus morphologies) that the deaths of murine macrophages are the result of necrotic rather than apoptotic events. We demonstrate that the bacteria must be alive in order to act cytotoxic. Therefore, one effect of the virulence-associated plasmids during infection withR. equiis the promotion of necrotic damage to the host.
Caspase-2 and Caspase-7 Are Involved in Cytolethal Distending Toxin-Induced Apoptosis in Jurkat and MOLT-4 T-Cell Lines
Authors: Ohara Masaru , Hayashi Tomonori , Kusunoki Yoichiro , Miyauchi Mutsumi , Takata Takashi , Sugai Motoyuki 
Published: January 2004

ABSTRACTCytolethal distending toxin (CDT) fromActinobacillus actinomycetemcomitansis a G2/M cell-cycle-specific growth-inhibitory toxin that leads to target cell distension followed by cell death. To determine the mechanisms by whichA. actinomycetemcomitansCDT acts as an immunosuppressive factor, we examined the effects of highly purified CDT holotoxin on human T lymphocytes. Purified CDT was cytolethal toward normal peripheral T lymphocytes that were activated by in vitro stimulation with phytohemagglutinin. In addition, purified CDT showed cytolethal activity against Jurkat and MOLT-4 cells, which are known to be sensitive and resistant, respectively, to Fas-mediated apoptosis. Death in these cell lines was accompanied by the biochemical features of apoptosis, including membrane conformational changes, intranucleosomal DNA cleavage, and an increase in caspase activity in the cells. Pretreatment of Jurkat cells with the general caspase inhibitor z-VAD-fmk mostly suppressed CDT-induced apoptosis. Furthermore, specific inhibitors of caspase-2 and -7 showed significant inhibitory effects on CDT-induced apoptosis in Jurkat cells, and these inhibitory effects were fully associated with reduced activity of caspase-2 or -7 in the CDT-treated Jurkat cells. These results strongly suggest that CDT possesses the ability to induce human T-cell apoptosis through activation of caspase-2 and -7.
Evaluation of the Association of NineHelicobacter pyloriVirulence Factors with Strains Involved in Low-Grade Gastric Mucosa-Associated Lymphoid Tissue Lymphoma
Authors: Lehours Philippe , Ménard Armelle , Dupouy Sandrine , Bergey Bernard , Richy Fréderique , Zerbib Frank , Ruskoné-Fourmestraux Agnès , Delchier Jean Charles , Mégraud Francis 
Published: January 2004

ABSTRACTHelicobacter pylorihas been associated with the development of two malignant diseases: gastric adenocarcinoma and gastric mucosa-associated lymphoid tissue (MALT) lymphoma. Although thecagpathogenicity island, especially thecagAgene, has been linked with adenocarcinoma, few data concerningH. pyloripathogenic factors involved in low-grade gastric MALT lymphoma are available. The goal of this study was to analyze the prevalence of and correlation between genes coding for sevenH. pylorivirulence factors (cagA,cagE,vacA,iceA,babA,hopQ, andoipA) and two novel adhesins (sabAandhopZ) by comparing a collection of 43H. pyloristrains isolated from patients with low-grade gastric MALT lymphoma to 39 strains isolated from age-matched patients with gastritis only. Our results show that taken individually, none of the nine genes tested can be considered associated with MALT strains and allow us to conclude that MALT pathogenesis is not linked with more proinflammatoryH. pyloristrains. We demonstrated that in patients infected with strains harboring theiceA1allele,sabAfunctional status, andhopZ“off” status, the odds of developing a MALT lymphoma were 10 times higher. However, the low prevalence of such strains (10 of 43 MALT strains) renders this triple association a low-sensitivity marker for MALT strains. Our data confirmed thatH. pylorivirulence factors are correlated with one another. If the involvement ofH. pyloriin MALT lymphoma is well established, the pathomechanism by which gastric lymphoma occurs remains to be identified.
Production of Secretory Immunoglobulin A against Shiga Toxin-Binding Subunits in Mice by Mucosal Immunization
Authors: Imai Yasuyuki , Nagai Rio , Ono Yousuke , Ishikawa Tomoyuki , Nakagami Hiroki , Tanikawa Takashi , Kurohane Kohta 
Published: January 2004

ABSTRACTThe toxicity of Shiga toxins (Stx) depends on the binding of their B subunits to carbohydrate ligands on host cells. The production of antibodies against B subunits, especially immunoglobulin A (IgA) secreted on the mucosal surface, should contribute to host defense. One of the major problems in attempts to produce IgA against Stx was the poor immunogenicity of B subunits. We were able to produce serum IgA as well as IgG against Stx1B in mice of theH-2dhaplotype by means of intranasal immunization with recombinant B subunits of Stx (Stx1B) together with cholera toxin as a mucosal adjuvant. Secretory IgA (S-IgA) was detected in nasal washes but not in feces. We prepared chemically cross-linked Stx1B for use as an immunogen, and the formation of stable oligomers was revealed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and mass spectrometry. When the cross-linked Stx1B was used together with cholera toxin for the intranasal immunization of BALB/c mice, strong enhancement of the immune response was observed. The S-IgA titers in nasal washes were 16- to more than 64-fold higher than those in mice immunized with native Stx1B plus cholera toxin. Furthermore, fecal IgA was detectable when the cross-linked Stx1B was used. The use of cholera toxin was necessary for the induction of high titers of S-IgA in the nasal washes. However, the effect of cross-linking was dependent on the major histocompatibility complex haplotype; that is, no enhancement of IgA production was observed in C57BL/6 mice. The present results provide a practical means of producing IgA against Stx1B in BALB/c mice.
RhuR, an Extracytoplasmic Function Sigma Factor Activator, Is Essential for Heme-Dependent Expression of the Outer Membrane Heme and Hemoprotein Receptor of
Bordetella avium
Authors: Kirby Amy E. , King Natalie D. , Connell Terry D. 
Published: January 2004

ABSTRACT

Genes involved in iron (Fe) acquisition often are regulated in response to the local availability of Fe. In many bacteria, Fe-dependent responsiveness is mediated by Fur, a global Fe-dependent transcriptional repressor. Tighter regulatory control of Fur-responsive genes is afforded by incorporating additional regulators into Fur-dependent regulatory cascades. RhuI, a Fur-dependent extracytoplasmic function sigma factor of
Bordetella avium
, in response to the dual stimulation of Fe starvation and the presence of heme (or hemoproteins), regulates P

bhuR

, a heme-responsive promoter which directs expression of the
bhuRSTUV
heme utilization operon. While BhuR, the outer membrane heme receptor, and RhuI have been shown to be indispensable for heme-dependent activation of P

bhuR

, collateral components of the regulatory cascade have not been described. In this investigation, RhuR, an integral cytoplasmic membrane protein with homology to anti-sigma factors, is shown to be an essential activator of P

bhuR

expression. The functional domain of RhuR required for heme-dependent activation of P

bhuR

expression was mapped to the N-terminal 97 amino acids of the protein by use of a chimeric RhuR-BlaM fusion. Expression of the chimera in a
rhuR
mutant rendered P

bhuR

constitutive, thereby decoupling the promoter from heme dependency. Growth studies confirmed that
B. avium
requires RhuR for optimal utilization of hemoglobin, but not hemin, as a sole source of nutrient Fe. These data imply that
B. avium
expresses, in addition to the BhuR heme/hemoprotein utilization system, an alternative RhuR-independent heme utilization mechanism. A model is proposed in which RhuR is the functional bridge between BhuR and RhuI in a heme-dependent regulatory cascade.
Generation ofYersinia pestisAttenuated Strains by Signature-Tagged Mutagenesis in Search of Novel Vaccine Candidates
Authors: Flashner Yehuda , Mamroud Emanuelle , Tidhar Avital , Ber Raphael , Aftalion Moshe , Gur David , Lazar Shirley , Zvi Anat , Bino Tamar , Ariel Naomi , Velan Baruch , Shafferman Avigdor , Cohen Sara 
Published: January 2004

ABSTRACTIn a search for novel attenuated vaccine candidates for use againstYersinia pestis, the causative agent of plague, a signature-tagged mutagenesis strategy was used and optimized for a subcutaneously infected mouse model. A library of tagged mutants of the virulentY. pestisKimberley53 strain was generated. Screening of 300 mutants through two consecutive cycles resulted in selection of 16 mutant strains that were undetectable in spleens 48 h postinfection. Each of these mutants was evaluated in vivo by assays for competition against the wild-type strain and for virulence following inoculation of 100 CFU (equivalent to 100 50% lethal doses [LD50] of the wild type). A wide spectrum of attenuation was obtained, ranging from avirulent mutants exhibiting competition indices of 10−5to 10−7to virulent mutants exhibiting a delay in the mean time to death or mutants indistinguishable from the wild type in the two assays. Characterization of the phenotypes and genotypes of the selected mutants led to identification of virulence-associated genes coding for factors involved in global bacterial physiology (e.g.,purH,purK,dnaE, andgreA) or for hypothetical polypeptides, as well as for the virulence regulator genelcrF. One of the avirulent mutant strains (LD50, >107CFU) was found to be disrupted in thepcmlocus, which is presumably involved in the bacterial response to environmental stress. This Kimberley53pcmmutant was superior to the EV76 live vaccine strain because it induced 10- to 100-fold-higher antibody titers to the protective V and F1 antigens and because it conferred efficacious protective immunity.
In Vivo Phase Variation and Serologic Response to Lipooligosaccharide ofCampylobacter jejuniin Experimental Human Infection
Authors: Prendergast Martina M. , Tribble David R. , Baqar Shahida , Scott Daniel A. , Ferris John A. , Walker Richard I. , Moran Anthony P. 
Published: January 2004

ABSTRACTSomeCampylobacter jejunistrains which exhibit mimicry of gangliosides in their lipooligosaccharides (LOSs) are associated with development of Guillain-Barré syndrome, which complicates the selection of a suitableC. jejunistrain in a live-attenuated vaccine.C. jejuni81-176 is the most well characterized strain available, but structurally, LOS ofC. jejuni81-176 exhibits mimicry of predominantly GM2and GM3gangliosides. We compared the antiganglioside human serologic responses of 22 volunteers post-oral vaccination (two-dose series, 14 days apart) with a killed whole-cellC. jejunivaccine, those of volunteers (22 following initial challenge and 5 upon rechallenge) experimentally infected with the homologousC. jejunivaccine strain 81-176, and those of 12 volunteers used as controls (placebo recipients). All volunteers were evaluated using thin-layer chromatography immuno-overlay and a panel of nine gangliosides at days 0, 21, and 28 either postvaccination or postinoculation. Antiganglioside antibodies were identified at baseline in 6 of the 61 volunteers (9.8%). There were no antiganglioside antibodies observed following vaccination or experimental infection rechallenge. Evidence of seroconversion was observed in 2 of 22 (9.1%) in the initial infection challenge group, comparable to 1 of 12 (8.3%) in the placebo recipients. Additional testing of seven selected volunteers in the initial challenge group at days 0, 3, 7, 10, 21, 28, and 60 showed that when antiganglioside antibodies occurred (mostly anti-GM1and -GM2), responses were weak and transient. Furthermore, evidence from serologic probing of LOSs of isolates recovered from stools of six volunteers indicated that the isolates had undergone antigenic phase variation in ganglioside mimicry during passage in vivo. Collectively, with the exception of one volunteer with anti-GM2antibodies at day 60, the results show an absence of persistent antiganglioside antibodies after experimental infection withC. jejunior following administration of a killedC. jejuniwhole-cell oral vaccine, although LOS phase variation occurred.
Two Studies Evaluating the Safety and Immunogenicity of a Live, Attenuated
Shigella flexneri
2a Vaccine (SC602) and Excretion of Vaccine Organisms in North American Volunteers
Authors: Katz David E. , Coster Trinka S. , Wolf Marcia K. , Trespalacios Fernando C. , Cohen Dani , Robins Guy , Hartman Antoinette B. , Venkatesan Malabi M. , Taylor David N. , Hale Thomas L. 
Published: January 2004

ABSTRACT

We report the first community-based evaluation of
Shigella flexneri
2a strain SC602, a live, oral vaccine strain attenuated by deletion of the
icsA
(
virG
) plasmid virulence gene, given at 10
4
CFU. The primary objectives of this trial were to determine the safety and immunogenicity of the vaccine and to determine the duration of colonization. Four of 34 volunteers experienced transient fevers, and three reported diarrhea during the first 3 days of the study. Half of the volunteers mounted a positive serum immunoglobulin A (IgA) response to
S. flexneri
lipopolysaccharide. All but one of the volunteers excreted the vaccine in their stools for 1 to 33 days, and this excretion was often intermittent. Data from the community-based study were supplemented with an inpatient trial in which three volunteers received 10
3
and nine received 10
4
CFU. All volunteers who received 10
3
CFU excreted SC602 and had an IgA antibody-secreting cell response. Two of these had a serum IgA response. Six of the nine volunteers who received 10
4
CFU excreted SC602. One vaccinee had a transient fever and two met the definition of diarrhea. Six volunteers that received 10
4
CFU had an antibody-secreting cell response, and four had a serum IgA response. SC602 has now been tested at 10
4
CFU in a total of 58 volunteers. The cumulative results of these clinical trials, reported here and previously (Coster et al., Infect. Immun.
67:
3437-3443, 1999), have demonstrated that SC602 is a substantially attenuated candidate vaccine that can evoke protection against the most severe symptoms of shigellosis in a stringent human challenge model of disease.
Heat Shock Protein 60 Acts as a Receptor for theListeriaAdhesion Protein in Caco-2 Cells
Authors: Wampler Jennifer L. , Kim Kwang-Pyo , Jaradat Ziad , Bhunia Arun K. 
Published: January 2004

ABSTRACTThe 104-kDaListeriaadhesion protein (LAP) inListeria monocytogenesis involved in binding to various mammalian cell lines. However, the receptor that interacts with LAP in eukaryotic cells is unknown. In this study, scanning immunoelectron microscopy qualitatively demonstrated greater binding capacity of wild-type (WT)L. monocytogenesstrain (F4244) than a LAP-deficient mutant strain (KB208) to Caco-2 cells. The goal of this study was identification of the host cell receptor for LAP. Using a Western blot ligand overlay assay, we identified a protein of 58 kDa to be the putative receptor for LAP from Caco-2 cells. N-terminal sequencing and subsequent database search identified this protein as heat shock protein 60 (Hsp60). Modified immunoseparation with protein A-Sepharose beads bound to the LAP-specific monoclonal antibody H7 (MAb-H7) and a sequential incubation with LAP preparation and Caco-2 lysate confirmed the receptor to be the same 58-kDa protein. Western blot analysis with anti-Hsp60 MAb of whole-cell adhesion between Caco-2 and WT also revealed the receptor protein to be a 58-kDa protein, thus corroborating the identification of Hsp60 as a host cell receptor for LAP. Furthermore, the anti-Hsp60 antibody also caused approximately 74% reduction in binding ofL. monocytogenesWT to Caco-2 cells, whereas a control antibody, C11E9, had no effect on binding. The adhesion mechanism ofL. monocytogenesto eukaryotic cells is a complex process, and identification of Hsp60 as a receptor for LAP adds to the list of previously discovered ligand-receptor modules that are essential to achieve successful adhesion.
Mycobacterium bovisBCG Cell Wall-Specific Differentially Expressed Genes Identified by Differential Display and cDNA Subtraction in Human Macrophages
Authors: Begum Nasim A. , Ishii Kazuo , Kurita-Taniguchi Mitsue , Tanabe Masako , Kobayashi Mika , Moriwaki Yasuhiro , Matsumoto Misako , Fukumori Yasuo , Azuma Ichiro , Toyoshima Kumao , Seya Tsukasa 
Published: January 2004

ABSTRACTWe have analyzed the gene expression profile of monocytes in response to a highly purified cell wall fraction ofMycobacterium bovisBCG, a clinically approved adjuvant known as BCG cell wall skeleton (BCG-CWS). It is composed of mycolic acid, arabinogalactan, and peptidoglycan and confers Toll-like receptor 2 (TLR2)- and TLR4-dependent signaling that induces monocytes to differentiate into antigen-presenting cells (APCs). Here we report differential gene expression analysis with BCG-CWS-stimulated versus nonstimulated monocytes. BCG-CWS exerted massive induction of genes regulated by TLR signaling. Marked gene regulatory characteristics in BCG-CWS-stimulated cells compared to lipopolysaccharide (LPS)-stimulated cells follow. (i) Spliced mRNAs encoding soluble forms of TREM-1 and TREM-2 (recently discovered inflammatory-signal-amplifying receptors) were regulated by BCG-CWS, resulting in their differential expression. (ii) The genes for zinc-iron transporter protein (ZIP)-like family proteins HKE-1 and LIV-1 were induced exclusively by BCG-CWS. (iii) Interleukin-23 (IL-23), rather than IL-12p70, was induced by BCG-CWS, while interferon-inducible genes were induced only by LPS. By Northern and reverse transcription-PCR analyses, we confirmed the differential expression of more than 30 BCG-CWS regulatory genes, and their expression was compared with that of LPS and other known TLR ligands. A battery of genes responded rapidly and for a short time to LPS but for a long time to BCG-CWS. Structural analysis of the identified novel or hypothetical proteins revealed that some are potential candidates as signaling mediators or transcriptional regulators. Hence, BCG-CWS may profoundly modulate APC responses in a way distinct from that of LPS, leading to possible advantages for its adjuvant-active therapeutic potential.
Mechanisms of Immunity toEhrlichia muris: a Model of Monocytotropic Ehrlichiosis
Authors: Feng Hui-Min , Walker David H. 
Published: January 2004

ABSTRACTEhrlichiaspecies can cause life-threatening infections or chronic persistent infections. Mechanisms of protective immunity were examined in anEhrlichia murismouse model of monocytotropic ehrlichiosis. C57BL/6 mice possessed strong genetic resistance toE. murisof an undetermined mechanism. CD8 T lymphocytes were particularly important, as revealed by 81% fatalities forE. muris-infected, major histocompatibility complex class I gene knockout mice compared with no deaths for wild-type C3H mice. Moreover, 80% of C3H mice depleted of CD8 and CD4 cells died ofE. murisinfection compared with only 44% of CD4 cell-depleted mice. CD8 T lymphocytes were demonstrated for the first time in anEhrlichiainfection to exhibit cytotoxic T-lymphocyte activity againstEhrlichia-infected target cells. Both gamma interferon and tumor necrosis factor were shown to play synergistic roles in protective immunity in vivo for the first time, as demonstrated by 75% fatalities when both cytokines were neutralized compared with minimal mortality when they were depleted separately. Passive transfer of antibodies, but not Fab fragments, toE. murisprotected C3H/SCID mice against lethal infection. The mechanism of increased susceptibility (22% lethality) of C57BL/6 major histocompatibility complex class II gene knockout mice and CD4 cell-depleted C3H mice (i.e., through a gamma interferon or antibody mechanism), as well as the more important role of CD8 T lymphocytes (in the form of cytotoxic T-lymphocyte activity and/or gamma interferon production), remains to be elucidated. Protective immunity against monocytotropicE. murisis mediated by a combination of CD8 and CD4 T lymphocytes, gamma interferon, tumor necrosis factor alpha, and antibodies.
The Staphylococcal Ferritins Are Differentially Regulated in Response to Iron and Manganese and via PerR and Fur
Authors: Morrissey Julie A. , Cockayne Alan , Brummell Kirsty , Williams Paul 
Published: January 2004

ABSTRACT

Staphylococcus aureus
and
Staphylococcus epidermidis
ferritin (FtnA and SefA, respectively) homologues are antigenic and highly conserved. A previous study showed that
ftnA
is a component of the
S. aureus
PerR regulon with its transcription induced by elevated iron and repressed by PerR, which functions as a manganese-dependent transcriptional repressor. We have further investigated the role of iron and Fur in the regulation of PerR regulon genes
ftnA
(ferritin),
ahpC
(alkyl-hydroperoxidase), and
mrgA
(Dps homologue) and shown that iron has a major role in the regulation of the PerR regulon and hence the oxidative stress response, since in the presence of both iron and manganese, transcription of PerR regulon genes is induced above the repressed levels observed with manganese alone. Furthermore the PerR regulon genes are differentially regulated by metal availability and Fur. First, there is an additional level of PerR-independent regulation of
ftnA
under low-iron conditions which is not observed with
ahpC
and
mrgA.
Second, there is a differential response of these genes to Fur as
ftnA
expression is constitutive in a
fur
mutant, while
ahpC
expression is constitutive under low-Fe/Mn conditions but some repression of
ahpC
still occurs in the presence of manganese, whereas
mrgA
expression is still repressed in the
fur
mutant as in wild-type
S. aureus
, although there is a decrease in the overall level of
mrgA
transcription. These studies have also shown that FtnA expression is regulated by growth phase, but maximal transcription of
ftnA
differs dependent on the growth medium. Moreover, there are significant regulatory differences between the
S. aureus
and
S. epidermidis
ferritins, as
sefA
expression in contrast to that of
ftnA
is derepressed under low-Fe/Mn ion conditions.