bluuebunny/crossref_metadata_2025_split huggingface dataset:
Listeriosis in the Pregnant Guinea Pig: a Model of Vertical Transmission
Authors: Bakardjiev Anna I. , Stacy Brian A. , Fisher Susan J. , Portnoy Daniel A. 
Published: December 2003

ABSTRACTFeto-placental infections represent a major cause of pregnancy complications, and yet the underlying molecular and cellular mechanisms of vertical transmission are poorly understood.Listeria monocytogenes, a facultative intracellular pathogen, is one of a group of pathogens that are known to cause feto-placental infections in humans and other mammals. The purpose of this study was to evaluate possible mechanisms of vertical transmission ofL. monocytogenes. Humans and guinea pigs have a hemochorial placenta, where a single layer of fetally derived trophoblasts separates maternal from fetal circulation. We characterizedL. monocytogenesinfection of the feto-placental unit in a pregnant guinea pig model and in primary human trophoblasts and trophoblast-derived cell lines. The clinical manifestations of listeriosis in the pregnant guinea pigs and the tropism ofL. monocytogenesto the guinea pig placenta resembled those in humans. Trophoblast cell culture systems were permissive for listerial growth and cell-to-cell spread and revealed thatL. monocytogenesdeficient in internalin A, a virulence factor that mediates invasion of nonphagocytic cells, was 100-fold defective in invasion. However, crossing of the feto-placental barrier in the guinea pig model was independent of internalin A, suggesting a negligible role for internalin-mediated direct invasion of trophoblasts in vivo. Further understanding of vertical transmission ofL. monocytogeneswill help in designing more effective means of treatment and disease prevention.
Survival Strategy of Obligately IntracellularEhrlichia chaffeensis: Novel Modulation of Immune Response andHost CellCycles
Authors: Zhang Jian-zhi , Sinha Mala , Luxon Bruce A. , Yu Xue-jie 
Published: December 2003

ABSTRACTEhrlichia chaffeensisis an obligatory intracellular bacterium which resides in an early endosome in monocytes.E. chaffeensisinfection in a human monocyte cell line (THP1) significantly altered the transcriptional levels of 4.5% of host genes, including those coding for apoptosis inhibitors, proteins regulating cell differentiation, signal transduction, proinflammatory cytokines, biosynthetic and metabolic proteins, and membrane trafficking proteins. The transcriptional profile of the host cell revealed key themes in the pathogenesis ofEhrlichia. First,E. chaffeensisavoided stimulation of or repressed the transcription of cytokines involved in the early innate immune response and cell-mediated immune response to intracellular microbes, such as the interleukin-12 (IL-12), IL-15, and IL-18 genes, which might makeEhrlichiaa stealth organism for the macrophage. Second,E. chaffeensisup-regulated NF-κB and apoptosis inhibitors and differentially regulated cell cyclins and CDK expression, which may enhance host cell survival. Third,E. chaffeensisalso inhibited the gene transcription of RAB5A, SNAP23, and STX16, which are involved in membrane trafficking. By comparing the transcriptional response of macrophages infected with other bacteria and that of macrophages infected withE. chaffeensis, we have identified few genes that are commonly induced and no commonly repressed genes. These results illustrate the stereotyped macrophage response to other pathogens, in contrast with the novel host response to obligate intracellularEhrlichia, whose survival depends entirely on a long evolutionary process of outmaneuvering macrophages.
MulticlonalLeishmania braziliensisPopulation Structure and Its Clinical Implication in a Region of Endemicity for American Tegumentary Leishmaniasis
Authors: Schriefer A. , Schriefer A. L. F. , Góes-Neto A. , Guimarães L. H. , Carvalho L. P. , Almeida R. P. , Machado P. R. , Lessa H. A. , de Jesus A. Ribeiro , Riley L. W. , Carvalho E. M. 
Published: December 2003

ABSTRACTIn Corte de Pedra (CP), northeastern Brazil,Leishmania braziliensiscauses three distinct forms of American tegumentary leishmaniasis (ATL). To test the hypothesis that strain polymorphism may be involved in this disease spectrum and accurately characterize the parasite population structure in CP, we compared oneL. major, two non-CPL. braziliensis, one CPL. amazonensis, and 45 CPL. braziliensisisolates, obtained over a 10-year period from localized cutaneous, mucosal, and disseminated leishmaniasis patients, with randomly amplified polymorphic DNA (RAPD). Electrophoretic profiles were mostly unique across species. All typing protocols revealed polymorphism among the 45 CPL. braziliensisisolates, which displayed eight different RAPD patterns and greater than 80% overall fingerprint identity, attesting to the adequacy of the tools to assess strain variability in CP's geographically limited population of parasites. The dendrogram based on the sum of RAPD profiles of each isolate unveiled nine discrete typing units clustered into five clades. Global positioning showed extensive overlap of these clades in CP, precluding geographic sequestration as the mechanism of the observed structuralization. Finally, all forms of ATL presented a statistically significant difference in their frequencies among the clades, suggesting thatL. braziliensisgenotypes may be accompanied by specific disease manifestation after infection.
IndividualMycobacterium tuberculosisResuscitation-Promoting Factor Homologues Are Dispensable for Growth In Vitro and In Vivo
Authors: Tufariello JoAnn M. , Jacobs, William R. , Chan John 
Published: December 2003

ABSTRACTMycobacterium tuberculosispossesses five genes with significant homology to the resuscitation-promoting factor (Rpf) ofMicrococcus luteus. TheM. luteusRpf is a secreted ∼16-kDa protein which restores active growth to cultures ofM. luteusrendered dormant by prolonged incubation in stationary phase. More recently, the Rpf-like proteins ofM. tuberculosishave been shown to stimulate the growth of extended-stationary-phase cultures ofMycobacterium bovisBCG. These data suggest that the Rpf proteins can influence the growth of mycobacteria; however, the studies do not demonstrate specific functions for the various members of this protein family, nor do they assess the function ofM. tuberculosisRpf homologues in vivo. To address these questions, we have disrupted each of the fiverpf-like genes inM. tuberculosisErdman, and analyzed the mutants for their growth in vitro and in vivo. In contrast toM. luteus, for whichrpfis an essential gene, we find that all of theM. tuberculosis rpfdeletion mutant strains are viable; in addition, all show growth kinetics similar to Erdman wild type both in vitro and in mouse organs following aerosol infection. Analysis ofrpfexpression inM. tuberculosiscultures from early log phase through late stationary phase indicates that expression of therpf-like genes is growth phase-dependent, and that the expression patterns of the fiveM. tuberculosis rpfgenes, while overlapping to various degrees, are not uniform. We also provide evidence that mycobacterialrpfgenes are expressed in vivo in the lungs of mice acutely infected with virulentM. tuberculosis.
Isolation and Characterization of a Secretory Component ofEchinococcus multilocularisMetacestodes Potentially Involved in Modulating the Host-Parasite Interface
Authors: Walker Mirjam , Baz Adriana , Dematteis Sylvia , Stettler Marianne , Gottstein Bruno , Schaller Johann , Hemphill Andrew 
Published: December 2003

ABSTRACTEchinococcus multilocularismetacestodes are fluid-filled, vesicle-like organisms, which are characterized by continuous asexual proliferation via external budding of daughter vesicles, predominantly in the livers of infected individuals. Tumor-like growth eventually leads to the disease alveolar echinococcosis (AE). We employed the monoclonal antibody (MAb) E492/G1, previously shown to be directed against a carbohydrate-rich, immunomodulatory fraction ofEchinococcus granulosus, to characterize potentially related components inE. multilocularis. Immunofluorescence studies demonstrated that MAb E492/G1-reactive epitopes were found predominantly on the laminated layer and in the periphery of developing brood capsules. The respective molecules were continuously released into the exterior medium and were also found in the parasite vesicle fluid. The MAb E492/G1-reactive fraction inE. multilocularis, named Em492 antigen, was isolated by immunoaffinity chromatography. Em492 antigen had a protein/carbohydrate ratio of 0.25, reacted with a series of lectins, and is related to the laminated layer-associated Em2(G11) antigen. The epitope recognized by MAb E492/G1 was sensitive to sodium periodate but was not affected by protease treatment. Anti-Em492 immunoglobulin G1 (IgG1) and IgG2 and, at lower levels, IgG3 were found in sera of mice suffering from experimentally induced secondary, but not primary, AE. However, with regard to cellular immunity, a suppressive effect on concanavalin A- or crude parasite extract-induced splenocyte proliferation in these mice was observed upon addition of Em492 antigen, but trypan blue exclusion tests and transmission electron microscopy failed to reveal any cytotoxic effect in Em492 antigen-treated spleen cells. This indicated that Em492 antigen could be modulating the periparasitic cellular environment duringE. multilocularisinfection through as yet unidentified mechanisms and could be one of the factors contributing to immunosuppressive events that occur at the host-parasite interface.
Helicobacter pyloriDisrupts STAT1-Mediated Gamma Interferon-Induced Signal Transduction in Epithelial Cells
Authors: Mitchell David J. , Huynh Hien Q. , Ceponis Peter J. M. , Jones Nicola L. , Sherman Philip M. 
Published: December 2003

ABSTRACTInfection withHelicobacter pyloriis chronic despite a vigorous mucosal immune response characterized by gastric T-helper type 1 cell expansion and gamma interferon (IFN-γ) production. IFN-γ signals by activation and nuclear translocation of signal transducer and activator of transcription 1 (STAT1); however, the effect ofH. pyloriinfection on IFN-γ-STAT1 signaling is unknown. We infected human gastric (MKN45 and AGS) and laryngeal (HEp-2) epithelial cell lines with type 1 and type 2H. pyloristrains and then stimulated them with IFN-γ. Western blotting of whole-cell protein extracts revealed that infection with live, but not heat-killed,H. pyloritime-dependently decreased IFN-γ-induced STAT1 tyrosine phosphorylation. Electrophoretic mobility shift assay of nuclear protein extracts demonstrated thatH. pyloriinfection reduced IFN-γ-induced STAT1 DNA binding. STAT1 was unable to translocate from the cytoplasm to the nucleus inH. pylori-infected HEp-2 cells examined by immunofluorescence, and reverse transcription-PCR showed that IFN-γ-induced interferon regulatory factor 1 expression was inhibited. These effects were independent of thecagA,cagE, and VacA status of the infectingH. pyloristrain. Furthermore, neitherH. pyloriculture supernatants nor conditioned medium fromH. pylori-infected MKN45 cells inhibited IFN-γ-induced STAT1 tyrosine phosphorylation, suggesting that inhibition is independent of a soluble epithelial or bacterial factor but is dependent on bacterial contact with epithelial cells.H. pyloridisruption of IFN-γ-STAT1 signaling in epithelial cells may represent a mechanism by which the bacterium modifies mucosal immune responses to promote its survival in the human host.
A Gene,
uge
, Is Essential for
Klebsiella pneumoniae
Virulence
Authors: Regué Miguel , Hita Beatriz , Piqué Nuria , Izquierdo Luis , Merino Susana , Fresno Sandra , Benedí Vicente Javier , Tomás Juan M. 
Published: December 2003

ABSTRACT

Klebsiella pneumoniae
strains typically express both smooth lipopolysaccharide (LPS) with O antigen molecules and capsule polysaccharide (K antigen) on the surface. A single mutation in a gene that codes for a UDP galacturonate 4-epimerase (
uge
) renders a strain with the O
−
:K
−
phenotype (lack of capsule and LPS without O antigen molecules and outer core oligosaccharide). The
uge
gene was present in all the
K. pneumoniae
strains tested. The
K. pneumoniae uge
mutants were unable to produce experimental urinary tract infections in rats and were completely avirulent in two different animal models (septicemia and pneumonia). Reintroduction of the single
uge
wild-type gene in the corresponding mutants completely restored the wild-type phenotype (presence of capsule and smooth LPS) independently of the O or K serotype of the wild type. Furthermore, complemented
uge
mutants recovered the ability to produce experimental urinary tract infections in rats and virulence in the septicemia and pneumonia animal models.
The ADP Ribosyltransferase Domain of
Pseudomonas aeruginosa
ExoT Contributes to Its Biological Activities
Authors: Garrity-Ryan L. , Shafikhani S. , Balachandran P. , Nguyen L. , Oza J. , Jakobsen T. , Sargent J. , Fang X. , Cordwell S. , Matthay M. A. , Engel J. N. 
Published: December 2003

ABSTRACT

ExoT is a type III secreted effector protein found in almost all strains of
Pseudomonas aeruginosa
and is required for full virulence in an animal model of acute pneumonia. It is comprised of an N-terminal domain with GTPase activating protein (GAP) activity towards Rho family GTPases and a C-terminal ADP ribosyltransferase (ADPRT) domain with minimal activity towards a synthetic substrate in vitro. Consistent with its activity as a Rho family GTPase, ExoT has been shown to inhibit
P. aeruginosa
internalization into epithelial cells and macrophages, disrupt the actin cytoskeleton through a Rho-dependent pathway, and inhibit wound repair in a scrape model of injured epithelium. We have previously shown that mutation of the invariant arginine of the GAP domain to lysine (R149K) results in complete loss of GAP activity in vitro but only partially inhibits ExoT anti-internalization and cell rounding activity. We have constructed in-frame deletions and point mutations within the ADPRT domain in order to test whether this domain might account for the residual activity observed in ExoT GAP mutants. Deletion of a majority of the ADPRT domain (residues 234 to 438) or point mutations of the ADPRT catalytic site (residues 383 to 385) led to distinct changes in host cell morphology and substantially reduced the ability of ExoT to inhibit in vitro epithelial wound healing over a 24-h period. In contrast, only subtle effects on the efficiency of ExoT-induced bacterial internalization were observed in the ADPRT mutant forms. Expression of each domain individually in
Saccharomyces cerevisiae
was toxic, whereas expression of each of the catalytically inactive mutant domains was not. Collectively, these data demonstrate that the ADPRT domain of ExoT is active in vivo and contributes to the pathogenesis of
P. aeruginosa
infections.
Development, Characterization, and Functional Activity of a Panel of Specific Monoclonal Antibodies to Inner Core Lipopolysaccharide Epitopes inNeisseria meningitidis
Authors: Gidney Margaret Anne J. , Plested Joyce S. , Lacelle Suzanne , Coull Philip A. , Wright J. Claire , Makepeace Katherine , Brisson Jean-Robert , Cox Andrew D. , Moxon E. Richard , Richards James C. 
Published: December 2003

ABSTRACTA panel of six murine monoclonal antibodies (MAbs) recognizing inner core lipopolysaccharide (LPS) epitopes ofNeisseria meningitidiswas prepared and characterized in order to determine the diversity of inner core LPS glycoforms among disease and carrier isolates. Two of these MAbs, L2-16 (immunoglobulin G2b [IgG2b]) and LPT3-1 (IgG2a), together with a third, previously described MAb, L3B5 (IgG3), showed reactivity, either individually or in combination, with all except 3 of 143 disease and carriage isolates (125 of 126 strains from blood, cerebrospinal fluid, or skin biopsy samples and 15 of 17 from nasopharyngeal cultures). MAbs L3B5, L2-16, and LPT3-1 were further characterized in an indirect immunofluorescence assay. All three MAbs bound to the bacterial cell surface, findings that correlated strongly with whole-cell enzyme-linked immunosorbent assay and immunodot blots. However, in contrast to our findings with L3B5, cell surface binding of L2-16 or LPT 3-1 did not correlate with functional activity as determined by bactericidal or infant rat passive protection assays against wild-typeN. meningitidisstrains. These findings are provocative with respect to the requirements for protective activity of antibodies and the development of inner core LPS vaccines against invasive meningococcal disease.
Stable T-Cell Population Expressing an Effector Cell Surface Phenotype in the Lungs of Mice Chronically Infected with
Mycobacterium tuberculosis
Authors: Junqueira-Kipnis Ana Paula , Turner Joanne , Gonzalez-Juarrero Mercedes , Turner Oliver C. , Orme Ian M. 
Published: December 2003

ABSTRACT

Analysis of T-cell subsets accumulating in the lungs of C57BL/6 mice chronically infected with
Mycobacterium tuberculosis
revealed that both CD4 and CD8 T-cell populations expressed a cell surface phenotype consistent with that of effector T cells and that a significant proportion of these cells were in the process of secreting gamma interferon.
In Vitro Induction of
Neospora caninum
Bradyzoites in Vero Cells Reveals Differential Antigen Expression, Localization, and Host-Cell Recognition of Tachyzoites and Bradyzoites
Authors: Vonlaufen Nathalie , Guetg Nicole , Naguleswaran Arunasalam , Müller Norbert , Björkman Camilla , Schares Gereon , von Blumroeder Daniela , Ellis John , Hemphill Andrew 
Published: December 2003

ABSTRACT

We report on an optimized method for the in vitro culture of tissue cyst-forming
Neospora caninum
bradyzoites in Vero cells and the separation of viable parasites from host cells. Treatment of tachyzoite-infected Vero cell cultures with 17 μM sodium nitroprusside for 8 days severely scaled down parasite proliferation, led to reduced expression of tachyzoite surface antigens, and induced the expression of the bradyzoite marker NcBAG1 and the cyst wall antigen recognized by the monoclonal antibody MAbCC2. Transmission electron microscopy demonstrated that intracellular parasites were located within parasitophorous vacuoles that were surrounded by a cyst wall-like structure, and the dense granule antigens NcGRA1, NcGRA2, and NcGRA7 were incorporated into the cyst wall. Adhesion-invasion assays employing purified tachyzoites and bradyzoites showed that tachyzoites adhered to, and invaded, Vero cells with higher efficiency than bradyzoites. However, removal of terminal sialic acid residues from either the host cell or the parasite surface increased the invasion of Vero cells by bradyzoites, but not tachyzoites.
Effect of CpG Oligodeoxynucleotides on the Immunogenicity of Pfs25, aPlasmodium falciparumTransmission-Blocking Vaccine Antigen
Authors: Coban Cevayir , Ishii Ken J. , Stowers Anthony W. , Keister David B. , Klinman Dennis M. , Kumar Nirbhay 
Published: December 2003

ABSTRACTAntibodies directed against Pfs25, a protein present on the surface of zygotes and ookinetes ofPlasmodium falciparum, completely block pathogen transmission. We evaluated the immunomodulatory effect of CpG oligodeoxynucleotides (ODN) on the immunogenicity of recombinant Pfs25 (rPfs25) formulated in alum (Al). Immunization of mice with rPfs25 plus CpG ODN improved both the antibody titer (a 30-fold-higher antibody response than that with rPfs25-Al alone) and avidity. Coadministration of CpG ODN dramatically enhanced the titer of immunoglobulin G2A (IgG2a) compared to the titer of the IgG1-dominant response caused by rPfs25-Al alone, and the sera from the CpG ODN-coadministered group completely blocked the transmission ofP. falciparumparasites to mosquitoes, as determined by membrane feeding assays. However, transmission-blocking experiments revealed that blocking efficacy was dependent on high-titer antibody levels, independent of isotypes. These results suggest that CpG ODN can be used as an adjuvant to enhance the immunogenicity of rPfs25 as a malaria transmission-blocking vaccine.
Inhibition of CD1 Expression in Human Dendritic Cells during Intracellular Infection withLeishmania donovani
Authors: Amprey Joseph L. , Späth Gerald F. , Porcelli Steven A. 
Published: December 2003

ABSTRACTDendritic cells can initiate antimicrobial responses by CD1-mediated presentation of pathogen-derived glycolipids. We show that the protozoanLeishmania donovaniinhibits CD1 expression and prevents activation of CD1-restricted T cells by dendritic cells. Evasion of presentation by CD1 may represent aLeishmaniasurvival strategy to avoid recognition of abundant parasite glycolipids.
Autotransporter Genes
pic
and
tsh
Are Associated with
Escherichia coli
Strains That Cause Acute Pyelonephritis and Are Expressed during Urinary Tract Infection
Authors: Heimer Susan R. , Rasko David A. , Lockatell C. Virginia , Johnson David E. , Mobley Harry L. T. 
Published: December 2003

ABSTRACT

We have identified two chromosomal open reading frames in uropathogenic
Escherichia coli
(UPEC) strain CFT073 which are highly homologous to serine protease autotransporters Pic and Tsh. Both cloned determinants were correlated with the presence of 105- to 110-kDa proteins in the culture supernatants. Furthermore, in cellular fractionation experiments, 30-kDa polypeptides were identified in the outer membrane; we speculated that these proteins are the β-barrel portions of the autotransporter homologues. Furthermore, Pic-containing culture supernatants have serine protease activity. In reverse transcription-PCR analyses, the expression of the
pic
and
tsh
genes in
E. coli
CFT073 was higher in broth cultures grown at 37°C than at 25°C. Moreover,
pic
and
tsh
were expressed by bacteria isolated from urine of transurethrally infected mice. The
tsh
determinant was identified in 63% of our clinical UPEC strain isolates (
n
= 87) and in 33% of fecal strains (
n
= 27), whereas
pic
was present in 31% of the pyelonephritis (
n
= 67) and 7% of the fecal strains. There was no significant correlation between cystitis strains (
n
= 20) and the
pic
determinant.
Relationship between
Candida albicans
Virulence during Experimental Hematogenously Disseminated Infection and Endothelial Cell Damage In Vitro
Authors: Sanchez Angela A. , Johnston Douglas A. , Myers Carter , Edwards John E. , Mitchell Aaron P. , Filler Scott G. 
Published: December 2003

ABSTRACT

Candida albicans
must penetrate the endothelial cell lining of the vasculature to invade the deep tissues during a hematogenously disseminated infection. We compared 27
C. albicans
mutants with their wild-type parent for their capacity to damage endothelial cells in vitro and cause a lethal infection in mice following tail vein inoculation. Of 10 mutants with significantly impaired capacity to damage endothelial cells, all had attenuated virulence. Therefore, the endothelial cell damage assay can be used as a screen to identify some virulence factors relevant to hematogenously disseminated candidiasis.
Protection against Anthrax Toxemia by Hexa-
d
-Arginine In Vitro and In Vivo
Authors: Sarac Miroslav S. , Peinado Juan R. , Leppla Stephen H. , Lindberg Iris 
Published: December 2003

ABSTRACT

The anthrax toxin protective antigen precursor is activated by proteolytic cleavage by furin or a furin-like protease. We present here data demonstrating that the small stable furin inhibitor hexa-
d
-arginine amide delays anthrax toxin-induced toxemia both in cells and in live animals, suggesting that furin inhibition may represent a reasonable avenue for therapeutic intervention in anthrax.