bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gamma Interferon Production by Hepatic NK T Cells duringEscherichia coliInfection Is Resistant to the Inhibitory Effects of Oxidative Stress
Authors: Zhang Guochi , Nichols Robert Dru , Taniguchi Masaru , Nakayama Toshinori , Parmely Michael J. 
Published: April 2003

ABSTRACTThe reductive-oxidative status of tissues regulates the expression of many inflammatory genes that are induced during gram-negative bacterial infections. The cytokine gamma interferon (IFN-γ) is a potent stimulus for host inflammatory gene expression, and oxidative stress has been shown to inhibit its production in mice challenged withEscherichia colibacteria. The objective of the present study was to characterize the cells that produced IFN-γ in a mouse bacterial peritonitis model and determine the effects of oxidative stress on their activation. The liver contained large numbers of IFN-γ-expressing lymphocytes following challenge with viableE. colibacteria. The surface phenotypes of IFN-γ-expressing hepatic lymphocytes were those of natural killer (NK) cells (NK1.1+CD3−), conventional T cells (NK1.1−CD3+), and NK T cells (NK1.1+CD3+). Treating mice with diethyl maleate to deplete tissue thiols significantly impaired IFN-γ production by NK cells, conventional T cells, and CD1d-restricted NK T cells in response toE. colichallenge. However, IFN-γ expression by a subset of NK T cells, which did not bind α-galactosylceramide-CD1d tetramers, was resistant to the inhibitory effects of tissue oxidative stress. Stress-resistant IFN-γ-expressing cells were also predominantly CD8+and bore γδ T-cell antigen receptors. The residual IFN-γ response by NK T cells may explain previous reports of hepatic gene expression following gram-negative bacterial challenge in thiol-depleted mice. The finding also demonstrates that innate immune cells differ significantly in their responses to altered tissue redox status.
Mutations in thelspA1andlspA2Genes ofHaemophilus ducreyiAffect the Virulence of This Pathogen in an Animal Model System
Authors: Ward Christine K. , Latimer Jo L. , Nika Joseph , Vakevainen Merja , Mock Jason R. , Deng Kaiping , Blick Robert J. , Hansen Eric J. 
Published: April 2003

ABSTRACTHaemophilus ducreyi35000HP contains two genes,lspA1andlspA2, whose predicted protein products have molecular weights of 456,000 and 543,000, respectively (C. K. Ward, S. R. Lumbley, J. L. Latimer, L. D. Cope, and E. J. Hansen, J. Bacteriol. 180:6013-6022, 1998). We have constructed threeH. ducreyi35000HP mutants containing antibiotic resistance cartridges in one or both of thelspA1andlspA2open reading frames. Western blot analysis using LspA1- and LspA2-specific monoclonal antibodies indicated that the wild-type parent strain 35000HP expressed LspA1 protein that was readily detectable in culture supernatant fluid together with a barely detectable amount of LspA2 protein. ThelspA2mutant 35000HP.2 expressed LspA1 protein that was detectable in culture supernatant fluid and no LspA2 protein. In contrast, theH. ducreyi lspA1mutant 35000HP.1, which did not express the LspA1 protein, expressed a greater quantity of the LspA2 protein than did the wild-type parent strain. ThelspA1 lspA2double mutant 35000HP.12 expressed neither LspA1 nor LspA2. The three mutant strains adhered to human foreskin fibroblasts and to a human keratinocyte cell line in vitro at a level that was not significantly different from that of the wild-type strain 35000HP. Lack of expression of the LspA1 protein by both thelspA1mutant and thelspA1 lspA2double mutant was associated with an increased tendency to autoagglutinate. When evaluated in the temperature-dependent rabbit model for chancroid, thelspA1 lspA2double mutant was substantially less virulent than the wild-type strain 35000HP. The results of these studies indicated thatH. ducreyirequires both the LspA1 and LspA2 proteins to be fully virulent in this animal model for experimental chancroid.
Epitope-Specific Humoral Immunity to
Plasmodium vivax
Duffy Binding Protein
Authors: Xainli Jia , Cole-Tobian Jennifer L. , Baisor Moses , Kastens Will , Bockarie Moses , Yazdani Syed Shams , Chitnis Chetan E. , Adams John H. , King Christopher L. 
Published: April 2003

ABSTRACT

Erythrocyte invasion by
Plasmodium vivax
is completely dependent on binding to the Duffy blood group antigen by the parasite Duffy binding protein (DBP). The receptor-binding domain of this protein lies within a cysteine-rich region referred to as region II (DBPII). To examine whether antibody responses to DBP correlate with age-acquired immunity to
P. vivax
, antibodies to recombinant DBP (rDBP) were measured in 551 individuals residing in a village endemic for
P. vivax
in Papua New Guinea, and linear epitopes mapped in the critical binding region of DBPII. Antibody levels to rDBP
II
increased with age. Four dominant linear epitopes were identified, and the number of linear epitopes recognized by semiimmune individuals increased with age, suggesting greater recognition with repeated infection. Some individuals had antibodies to rDBP
II
but not to the linear epitopes, indicating the presence of conformational epitopes. This occurred in younger individuals or subjects acutely infected for the first time with
P. vivax
, indicating that repeated infection is required for recognition of linear epitopes. All four dominant B-cell epitopes contained polymorphic residues, three of which showed variant-specific serologic responses in over 10% of subjects examined. In conclusion, these results demonstrate age-dependent and variant-specific antibody responses to DBPII and implicate this molecule in partial acquired immunity to
P. vivax
in populations in endemic areas.
Kinetics of Antibody Response toEhrlichia canisImmunoreactive Proteins
Authors: McBride Jere W. , Corstvet Richard E. , Gaunt Steven D. , Boudreaux Charles , Guedry Thaya , Walker David H. 
Published: April 2003

ABSTRACTImmunoreactive proteins ofEhrlichia canisandEhrlichia chaffeensisthat have been characterized include a family of 28-kDa major outer membrane proteins (p28) and two large antigenically divergent surface glycoprotein orthologs. We previously demonstrated that recombinantE. canisp28 and the 140- and 200-kDa glycoproteins gp140 and gp200, respectively, react strongly with serum antibodies from suspect canine ehrlichiosis cases that were positive forE. canisby immunofluorescent antibody test and in various phases of acute or chronic infection (J. Clin. Microbiol. 39:315-322, 2001). The kinetics of the antibody response to these potentially important vaccine and immunodiagnostic candidates is not known. Acute-phase serum antibody responses to whole-cellE. canislysates and recombinant p28, gp140, and gp200 were monitored for 6 weeks in dogs experimentally infected withE. canis. Irrespective of the inoculation route, a T-helper 1-type response was elicited toE. canisantigens consisting of immunoglobulin G2 antibodies exclusively in both acute and convalescent phases in most dogs. Analysis of immuoreactive antigens for peak intensity and relative quantity identified major immunoreactiveE. canisantigens recognized early in the infection as the 19-, 37-, 75-, and 140-kDa proteins. Later in infection, additional major immunoreactiveE. canisproteins were identified, including the 28-, 47-, and 95-kDa proteins and the recently identified 200-kDa glycoprotein. All dogs had developed antibody against the recombinant gp140, gp200, and p28 in the convalescent phase. Immunoreactivity and antibody response kinetics suggest that major immunoreactive proteins identified are immunodominant, but early recognition suggests increased dominance by some antigens.
Identification of aTreponema pallidumLaminin-Binding Protein
Authors: Cameron Caroline E. 
Published: April 2003

ABSTRACTHost extracellular matrix (ECM) components represent ideal microbial adhesion targets that many pathogens use for colonization of tissues and initiation of infection. This study investigated the interaction of the spirocheteTreponema pallidumwith the ECM component laminin. To identify candidate laminin-binding adhesins, theT. pallidumgenome was analyzed to predict open reading frames that encode putative outer membrane proteins, as these proteins interact directly with host ECM components. Subsequent recombinant expression of these proteins and analysis of their laminin-binding potential identified one protein, Tp0751, that demonstrated specific attachment to laminin. Tp0751 attached to laminin in a dose-dependent, saturable manner but did not attach to the ECM component collagen type I or IV or to the negative control proteins fetuin or bovine serum albumin. Sodium metaperiodate treatment of laminin reduced the Tp0751-laminin interaction in a concentration-dependent manner, suggesting that oligosaccharides play a role in this interaction. In addition, Tp0751-specific antibodies were detected in serum samples collected from both experimental and natural syphilis infections, indicating that Tp0751 is expressed in vivo during the course of infection. Collectively, these experiments identified Tp0751 as a laminin-binding protein that is expressed during infection and may be involved in attachment ofT. pallidumto host tissues.
Development of an Interleukin-12-Deficient Mouse Model That Is Permissive for Colonization by a Motile KE26695 Strain of
Helicobacter pylori
Authors: Hoffman Paul S. , Vats Neeraj , Hutchison Donna , Butler Jared , Chisholm Kenneth , Sisson Gary , Raudonikiene Ausra , Marshall Jean S. , Veldhuyzen van Zanten Sander J. O. 
Published: April 2003

ABSTRACT

The identification of genes associated with colonization and persistence of
Helicobacter pylori
in the gastric mucosa has been limited by the lack of robust animal models that support infection by strains whose genomes have been completely sequenced. Here we report that an interleukin-12 (IL-12)-deficient mouse (IL-12
−/−
p40 subunit knockout in C57BL/6 mouse) is permissive for infection by a motile variant (KE88-3887) of The Institute For Genomic Research-sequenced strain (KE26695) of
H. pylori
. The IL-12-deficient mouse was also more permissive for colonization by the mouse-colonizing Sydney 1 strain of
H. pylori
than were wild-type C57BL/6 mice. Differences in colonization efficiency were demonstrated by mouse challenge with SS1 strains containing loss-of-function mutations in two genes (
hspR
and
hrcA
), whose products negatively regulate several heat shock genes. At 5 weeks postinfection, double-knockout mutants (SS1
hspR hrcA
) efficiently colonized IL-12-deficient mice (5 of 5 animals compared to 4 of 10 for C57BL6 mice) and bacterial counts were higher in stomachs of IL-12-deficient mice (10
6
versus 10
5
CFU/g of stomach, respectively). IL-12-deficient mice were efficiently colonized by KE88-3887 (29 of 30), but not by nonmotile KE26695, and bacterial numbers (10
4
to 10
5
CFU/g of stomach) were unchanged over an 8-week period postinfection. In contrast, C57BL/6 mice were inefficiently colonized by KE88-3887 (8 of 20 animals with bacterial loads at the limit of detection, ∼10
3
CFU/g), and infection did not persist much beyond 5 weeks. Cytokine responses (tumor necrosis factor alpha and gamma interferon), pathology, and antral-predominant infection were indistinguishable between IL-12-deficient and C57BL/6 mice. The increased permissiveness of the IL-12-deficient mouse for infection with
H. pylori
should facilitate whole-genome-based strategies to study genes associated with virulence and immune modulation.
A Constitutively Active Variant of the Quorum-Sensing Regulator LuxO Affects Protease Production and Biofilm Formation in
Vibrio cholerae
Authors: Vance Russell E. , Zhu Jun , Mekalanos John J. 
Published: April 2003

ABSTRACT

Vibrio cholerae
normally inhabits aquatic habitats but can cause a severe diarrheal illness in humans. Its arsenal of virulence factors includes a secreted hemagglutinin (HA) protease. An HA protease-deficient mutant of
V. cholerae
was isolated and designated E7946
mpc.
E7946
mpc
was found to contain a point mutation in the
luxO
quorum-sensing regulator. In accordance with this finding, E7946
mpc
exhibits a defect in quorum sensing. The mutant
luxO
allele [
luxO
(Con)] produces a protein with a leucine-to-glutamine substitution at amino acid 104. Transfer of the
luxO
(Con) allele to an otherwise wild-type background was sufficient to eliminate HA protease expression; conversely, deletion of
luxO
(Con) from E7946
mpc
restored protease activity. We demonstrate that LuxO(Con) constitutively represses the transcription of
hapR
, an essential positive regulator of HA protease. Interestingly, strains harboring
luxO
(Con) form enhanced biofilms, and enhanced biofilm formation does not appear to be dependent on reduced HA protease expression. Taken together, the results confirm the role of LuxO as a central “switch” that coordinately regulates virulence-related phenotypes such as protease production and biofilm formation.
Characterization of the Role of the Divalent Metal Ion-Dependent Transcriptional Repressor MntR in the Virulence of
Staphylococcus aureus
Authors: Ando Masaru , Manabe Yukari C. , Converse Paul J. , Miyazaki Eishi , Harrison Robert , Murphy John R. , Bishai William R. 
Published: April 2003

ABSTRACT

DtxR-type metal ion-dependent repressors, present in many bacterial pathogens, may regulate expression of virulence genes such as that encoding diphtheria toxin. SirR, a DtxR homologue initially identified in
Staphylococcus epidermidis
, governs the expression of the adjacent
sitABC
operon encoding a putative metal ion ABC transporter system. We identified a
sirR
homologue,
mntR
, in
Staphylococcus aureus
and demonstrated by gel shift assay that the corynebacterial repressor DtxR binds to the
S. aureus mntABC
operator in the presence of Fe
2+
or Mn
2+
. Since a mutant DtxR, DtxR(E175K), functions as an iron-independent hyperrepressor in certain settings, we constructed a heterodiploid
S. aureus
strain expressing
dtxR
(
E175K
) from the native
mntR
promoter. Transcription of the
S. aureus mntABC
operon was repressed in the presence of Fe
2+
or Mn
2+
in wild-type and heterodiploid
S. aureus
strains. Under metal ion-limiting conditions,
mntABC
transcription was reduced but not abolished in
S. aureus
isolates expressing
dtxR
(
E175K
) compared with an isogenic control, suggesting that DtxR(E175K) binds the
S. aureus
MntR box in vivo. Under all conditions tested,
mntABC
transcription in the
dtxR
(
E175K
)-expressing strain was reduced relative to the isogenic control, indicating that DtxR(E175K) function was constitutively active. In the mouse skin abscess model,
dtxR
(
E175K
)-expressing
S. aureus
recombinants showed significantly reduced CFU levels compared with the isogenic wild-type control. We conclude that the
S. aureus
MntR box is recognized by corynebacterial DtxR proteins and thus belongs to the DtxR family of metal-dependent operator sites. Moreover, constitutive repression by DtxR(E175K) reduces the virulence of
S. aureus
in the mouse skin abscess model.
Increased Adherence to Caco-2 Cells Caused by Disruption of the
yhiE
and
yhiF
Genes in Enterohemorrhagic
Escherichia coli
O157:H7
Authors: Tatsuno Ichiro , Nagano Keiji , Taguchi Kazuki , Rong Li , Mori Hiroshi , Sasakawa Chihiro 
Published: April 2003

ABSTRACT

Adherence of enterohemorrhagic
Escherichia coli
(EHEC) to intestinal epithelium is essential for initiation of infections, including diarrhea, and expression of the genes of the locus of enterocyte effacement (LEE) is thought to be crucial for adherence. To identify genes involved in modulating the adherent capacity, bacteria collected from an EHEC O157:H7 strain (O157Sakai) mutagenized by mini-Tn
5
Km2 were screened for their ability to increase the number of microcolonies (MC) on Caco-2 cells and eight mutants with increased adherence were isolated. Analysis of the mini-Tn
5
Km2-flanked DNA sequences indicated that one possessed the insertion within an O157 antigen gene cluster, another possessed the insertion within the
yhiF
gene, and the remaining six mutants had their insertions in the
yhiE
gene.
yhiE
and
yhiF
products share amino acid homology (23% identity) to each other and with members of the LuxR family, which are known as transcriptional regulatory proteins. The mutant having the insertion within the O157 antigen gene cluster did not express the O157 side chain (as determined by agglutination test and immunoblotting with polyclonal O157-specific antiserum), unlike the other seven mutants. Importantly, the other mutants showed enhanced type III secretion. Levels of the related mRNAs of genes of the LEE, but not that of
ler
mRNA, were also increased compared with those in the wild type. Indeed, when we introduced an in-frame deletion into the
yhiE
or
yhiF
gene in O157Sakai, the capacity of the resultant mutants to adhere to Caco-2 cells was greatly increased. When one of the
yhiE
insertion mutants was orally inoculated into ICR mice, the number of bacteria shed into feces by day 14 was greater than that for the wild type. These results suggest that
yhiE
and
yhiF
are involved in the adherence of O157Sakai to epithelial cells as negative regulators for the expression of the genes required for the type III secretion system.
Induction of Proinflammatory Responses in the Human Monocytic Cell Line THP-1 byCampylobacter jejuni
Authors: Jones Michael A. , Tötemeyer Sabine , Maskell Duncan J. , Bryant Clare E. , Barrow Paul A. 
Published: April 2003

ABSTRACTCampylobacter jejunican cause an enteritis that is associated with an acute inflammatory response at the gut epithelial surface. The signals inducing inflammation are unknown.C. jejunican penetrate the intestinal epithelial barrier and may then interact with leucocytes, potentially inducing proinflammatory responses. To investigate this, we studied the interaction ofC. jejuniwith the human monocytic cell line THP-1 and show that a range of proinflammatory cytokines and chemokines is induced. These include interleukin-1α (IL-1α), IL-1β, IL-6, IL-8, and tumor necrosis factor alpha. Responses can be induced by killedCampylobacteras well as live bacteria and do not depend on the cytolethal distending toxin.C. jejuniinfection of THP-1 cells triggers both nuclear translocation of functional NF-κB and stimulation of IL-1α, indicating that NF-κB-dependent and -independent stimulation is occurring. The extent of proinflammatory cytokine stimulation suggests that monocytes might significantly contribute to intestinal inflammation and disease pathology.
CC Chemokines Mediate Leukocyte Trafficking into the Central Nervous System during Murine Neurocysticercosis: Role of γδ T Cells in Amplification of the Host Immune Response
Authors: Cardona Astrid E. , Gonzalez Paula A. , Teale Judy M. 
Published: April 2003

ABSTRACTAccording to a previous report, the degree of the host immune response highly correlates with severity of the disease in the murine model for neurocysticercosis. In wild-type mice,Mesocestoides cortiinfection induced a rapid and extensive accumulation of γδ T cells and macrophages in the brain. NK cells, dendritic cells, αβ T cells, and B cells were also recruited to the brain but at lower levels. In contrast, γδ T-cell-deficient mice exhibited decreased cellular infiltration and reduced central nervous system (CNS) pathology. To understand the mechanisms of leukocyte recruitment into the CNS, chemokine expression was analyzed in infected brains in the present study. MCP-1 (CCL2), MIP-1α (CCL3), and MIP-1β (CCL4) were up-regulated within 2 days afterM. cortiinfection. Protein expression of RANTES (CCL5), eotaxin (CCL11), and MIP-2 was detected later, at 1 week postinfection. Correlating with the decreased cellular infiltration, delta chain T-cell receptor-deficient (TCRδ−/−) mice exhibited substantially reduced levels of most of the chemokines analyzed (with the exception of eotaxin). The results suggest that γδ T cells play an important role in the CNS immune response by producing chemokines such as MCP-1 and MIP-1α, enhancing leukocyte trafficking into the brain during murine neurocysticercosis.
Persistence of Mucosal Mast Cells and Eosinophils inShigella-Infected Children
Authors: Raqib Rubhana , Moly Pricila Khan , Sarker Protim , Qadri Firdausi , Alam Nurul Haque , Mathan Minnie , Andersson Jan 
Published: April 2003

ABSTRACTCells of the innate immune system and their mediators were studied at the single-cell level in the rectums of pediatric and adult patients withShigellainfection to better understand why children are at higher risk for severe infection. Adult patients had increased infiltration of mucosal mast cells (MMC) at the acute stage (3 to 5 days after the onset of diarrhea) and eosinophils in early convalescence (14 to 16 days after onset). Increased expression of stem cell factor and prostaglandin H synthase-1 (PGHS-1) was associated with increased tryptase-Ki67-double-positive MMC in the acute stage and increased apoptosis of MMC, which led to a rapid decline in early convalescence. The eosinophils demonstrated increased expression of major basic protein (MBP), eotaxin, and CCR3, as well as increased necrotic death. The neutrophils showed enhanced α-defensin and lactoferrin expression in the acute phase. In contrast to adults, the pediatric patients demonstrated delayed accumulation of mast cells and eosinophils, while α-defensin expression persisted during convalescence. In contrast, neutrophil counts and lactoferrin expression were reduced in children compared to adults. The results suggest that children with shigellosis have a persistent activation of the innate immune response in the convalescent phase, indicating delayed elimination ofShigellaantigens compared to adults.
Rapid Apoptosis Induced by Shiga Toxin in HeLa Cells
Authors: Fujii Jun , Matsui Takashi , Heatherly Daniel P. , Schlegel Kailo H. , Lobo Peter I. , Yutsudo Takashi , Ciraolo Georgianne M. , Morris Randal E. , Obrig Tom 
Published: April 2003

ABSTRACTApoptosis was induced rapidly in HeLa cells after exposure to bacterial Shiga toxin (Stx1 and Stx2; 10 ng/ml). Approximately 60% of HeLa cells became apoptotic within 4 h as detected by DNA fragmentation, terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling (TUNEL) assay, and electron microscopy. Stx1-induced apoptosis required enzymatic activity of the Stx1A subunit, and apoptosis was not induced by the Stx2B subunit alone or by the anti-globotriaosylceramide antibody. This activity was also inhibited by brefeldin A, indicating the need for toxin processing through the Golgi apparatus. The intracellular pathway leading to apoptosis was further defined. Exposure of HeLa cells to Stx1 activated caspases 3, 6, 8, and 9, as measured both by an enzymatic assay with synthetic substrates and by detection of proteolytically activated forms of these caspases by Western immunoblotting. Preincubation of HeLa cells with substrate inhibitors of caspases 3, 6, and 8 protected the cells against Stx1-dependent apoptosis. These results led to a more detailed examination of the mitochondrial pathway of apoptosis. Apoptosis induced by Stx1 was accompanied by damage to mitochondrial membranes, measured as a reduced mitochondrial membrane potential, and increased release of cytochromecfrom mitochondria at 3 to 4 h. Bid, an endogenous protein known to permeabilize mitochondrial membranes, was activated in a Stx1-dependent manner. Caspase-8 is known to activate Bid, and a specific inhibitor of caspase-8 prevented the mitochondrial damage. Although these data suggested that caspase-8-mediated cleavage of Bid with release of cytochromecfrom mitochondria and activation of caspase-9 were responsible for the apoptosis, preincubation of HeLa cells with a specific inhibitor of caspase-9 did not protect against apoptosis. These results were explained by the discovery of a simultaneous Stx1-dependent increase in endogenous XIAP, a direct inhibitor of caspase-9. We conclude that the primary pathway of Stx1-induced apoptosis and DNA fragmentation in HeLa cells is unique and includes caspases 8, 6, and 3 but is independent of events in the mitochondrial pathway.