bluuebunny/crossref_metadata_2025_split huggingface dataset:
Survival ofChlamydia pneumoniae-Infected Mono Mac 6 Cells Is Dependent on NF-κB Binding Activity
Authors: Wahl Christian , Oswald Franz , Simnacher Ulrike , Weiss Sonja , Marre Reinhard , Essig Andreas 
Published: July 2002

ABSTRACTThe respiratory tract pathogenChlamydia pneumoniaehas been associated with atherosclerosis. Monocytes are supposed to serve as a vehicle for systemic dissemination of intracellularC. pneumoniaefrom the lung to the artery vessel wall. We were therefore interested in pathogen-induced cellular events associated with NF-κB, a crucial transcription factor for both inflammatory cytokines and antiapoptotic molecules. In this study we demonstrate by electrophoretic mobility shift assay thatC. pneumoniaeinfection of the human monocytic cell line Mono Mac 6 induces activation of NF-κB over 48 h, with a maximum level at 1 h postinfection. As shown by supershift assay, the activated NF-κB complex consists of the subunits RelA (p65) and NF-κB1 (p50). Apoptotic host cells were not detected during the early stages of the infection when maximal activation of NF-κB was detected. Pretreatment of Mono Mac 6 with the antioxidant and NF-κB inhibitor PDTC (pyrrolidine dithiocarbamate) induced activation of caspase-3 and led to apoptotic cell death. TheC. pneumoniae-induced activation of the NF-κB complex was reduced by PDTC, which in parallel resulted in an increased apoptosis, as quantified by annexin V labeling and terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling reaction. In the complete absence of activated NF-κB, when Mono Mac 6 cells were pretreated with the more potent NF-κB inhibitors MG-132 and parthenolide aC. pneumoniae-mediated rescue of cells from induced apoptosis could not be achieved. Our results indicate that activation of NF-κB inC. pneumoniae-infected Mono Mac 6 cells is associated with protection of Mono Mac 6 cells against apoptosis and might thereby contribute to systemic spread of the pathogen.
Group A Streptococci Bind to Mucin and Human Pharyngeal Cells through Sialic Acid-Containing Receptors
Authors: Ryan Patricia A. , Pancholi Vijaykumar , Fischetti Vincent A. 
Published: July 2002

ABSTRACT

The first step in the colonization of group A streptococci (
Streptococcus pyogenes
) is adherence to pharyngeal epithelial cells. Prior to adherence to their target tissue, the first barrier that the streptococci encounter is the mucous layer of the respiratory tract. The present study was undertaken to characterize the interaction between mucin, the major glycoprotein component of mucus, and streptococci. We report here that
S. pyogenes
is able to bind to bovine submaxillary mucin in solid-phase microtiter plate assays. Western blots probed with
125
I-labeled mucin and a panel of monoclonal antibodies revealed that the streptococcal M protein is one of two cell wall-associated proteins responsible for this binding. The binding was further localized to the N-terminal portion of the M molecule. Further analysis revealed that the M protein binds to the sialic acid moieties on mucin, and this interaction seems to be based on M-protein conformation rather than specific amino acid sequences. We found that sialic acid also plays a critical role in the adherence of an M6 streptococcal strain to the Detroit 562 human pharyngeal cell line and have identified α2-6-linked sialic acid as an important sialylated linkage for M-protein recognition. Western blot analysis of extracted pharyngeal cell membrane proteins identified three potential sialic acid-containing receptors for the M protein. The results are the first to show that sialic acid not only is involved in the binding of the streptococci to mucin but also plays an important role in adherence of group A streptococci to the pharyngeal cell surface.
Genetics of Surface Antigen Expression inPneumocystis carinii
Authors: Stringer James R. , Keely Scott P. 
Published: July 2002

ABSTRACTThis article reviews the molecular genetic data pertaining to the major surface glycoprotein (MSG) gene family ofPneumocystis cariniiand its role in surface variation and compares this fungal system to antigenic variation systems in the protozoanTrypanosoma bruceiand the bacteriaBorreliaspp.
Identification of Rgg-Regulated Exoproteins of
Streptococcus pyogenes
Authors: Chaussee Michael S. , Watson Robert O. , Smoot James C. , Musser James M. 
Published: July 2002

ABSTRACT

Streptococcus pyogenes
secretes many proteins that influence host-pathogen interactions. Despite their importance, relatively little is known about the regulation of these proteins. The
rgg
gene (also known as
ropB
) is required for the expression of streptococcal erythrogenic toxin B (SPE B), an extracellular cysteine protease that contributes to virulence. Proteomics was used to determine if
rgg
regulates the expression of additional exoproteins. Exponential- and stationary-phase culture supernatant proteins made by
S. pyogenes
NZ131
rgg
and NZ131
speB
were separated by two-dimensional electrophoresis. Differences were identified in supernatant proteins from both exponential- and stationary-phase cultures, although considerably more differences were detected among stationary-phase supernatant proteins. Forty-two proteins were identified by peptide fingerprinting with matrix-assisted laser desorption mass spectrometry. Mitogenic factor, DNA entry nuclease (open reading frame [ORF 226]), and ORF 953, which has no known function, were more abundant in the culture supernatants of the
rgg
mutant compared to the
speB
mutant. ClpB, lysozyme, and autolysin were detected in the culture supernatant of the
speB
mutant but not the
rgg
mutant. To determine if Rgg affected protein expression at the transcriptional level, real-time (TaqMan) reverse transcription (RT)-PCR was used to quantitate Rgg-regulated transcripts from NZ131 wild-type and
speB
and
rgg
mutant strains. The results obtained with RT-PCR correlated with the proteomic data. We conclude that Rgg regulates the transcription of several genes expressed primarily during the stationary phase of growth.
Fas (CD95)-Fas Ligand Interactions Are Responsible for Monocyte Apoptosis Occurring as a Result of Phagocytosis and Killing ofStaphylococcus aureus
Authors: Baran J. , Weglarczyk K. , Mysiak M. , Guzik K. , Ernst M. , Flad H.-D. , Pryjma J. 
Published: July 2002

ABSTRACTHuman peripheral blood monocytes become apoptotic following phagocytosis ofStaphylococcus aureus. In this study, we investigated the mechanisms involved in this phenomenon. Cells exposed to bacteria were examined for the surface expression of Fas and Fas ligand (FasL). The level of soluble form of FasL was also measured in the culture supernatants. As Fas-mediated apoptosis involves the activation of caspases, the activities of caspase-8 and caspase-3 were determined. Finally, the involvement of oxidative stress in apoptosis of infected monocytes was investigated. The data indicated that as a consequence of phagocytosis ofS. aureus, FasL is released from the monocyte surface and induces apoptosis of phagocytic monocytes and to some extent the bystander cells. The importance of this mechanism was confirmed by demonstrating that blockage of CD95 preventsS. aureus-induced apoptosis of monocytes. Cell death occurring after phagocytosis ofS. aureusinvolves the activation of caspase-3-like proteases, as the specific caspase-3 inhibitor suppressed apoptosis of infected cells. The generation of reactive oxygen intermediates by phagocytic monocytes by itself is not sufficient as a death signal but rather acts in up-regulating FasL shedding and possibly in modulating caspase activity.
Pheromone Cross-Inhibition between
Staphylococcus aureus
and
Staphylococcus epidermidis
Authors: Otto Michael , Echner Hartmut , Voelter Wolfgang , Götz Friedrich 
Published: July 2002

ABSTRACT

Cross-inhibition by quorum-sensing pheromones between
Staphylococcus aureus
and
Staphylococcus epidermidis
was investigated using all known
S. aureus agr
pheromone subgroups. All
S. aureus
subgroups were sensitive towards the
S. epidermidis
pheromone, with the exception of the recently identified subgroup 4. The subgroup 4 pheromone was also the only
S. aureus
pheromone able to inhibit the
S. epidermidis agr
response. The close relation of subgroup 4 to subgroup 1 suggests that subgroup 4 might have evolved from subgroup 1 by mutation under the selective pressure of competition with
S. epidermidis
. The competition between
S. aureus
and
S. epidermidis
by means of quorum-sensing cross talk seems to be generally in favor of
S. epidermidis
, which might explain the predominance of
S. epidermidis
on the skin and in infections on indwelling medical devices.
Virulence of a Phosphoribosylaminoimidazole Carboxylase-Deficient
Candida
albicans
Strain in an Immunosuppressed Murine Model of Systemic Candidiasis
Authors: Donovan Matthew , Schumuke Jon J. , Fonzi William A. , Bonar Sheri L. , Gheesling-Mullis Karen , Jacob Gary S. , Davisson Vincent Jo , Dotson Stanton B. 
Published: July 2002

ABSTRACT

The relative pathogenicities of three
Candida albicans
strains differing in the function of
ADE2
(the gene encoding phosphoribosylaminoimidazole carboxylase) were evaluated in a murine candidiasis model.
C. albicans
strain CAI7 (
ade2/ade2
), previously constructed by site-specific recombination, was avirulent in immunosuppressed mice compared to the parent strain, CAF2-1, and a heterozygous
ADE2
/
ade2
strain obtained by transforming CAI7 with a wild-type allele. The reduced virulence of CAI7 was correlated with the inability to proliferate in either synthetic medium or serum without the exogenous addition of >10 μg of adenine/ml. The loss of virulence upon site-specific disruption of the
ade2
locus, and the restoration of wild-type virulence with the repair of just one
ade2
allele, confirmed that the
ADE2
gene and de novo purine biosynthesis were required for
Candida
pathogenicity. The potential of the phosphoribosylaminoimidazole carboxylase enzyme as a novel target for antifungal drug discovery is discussed.
Intracellular Crystal Formation as a Mechanism of Cytotoxicity in Murine PulmonaryCryptococcus neoformansInfection
Authors: Feldmesser Marta , Kress Yvonne , Casadevall Arturo 
Published: July 2002

ABSTRACTRod-like crystalline structures formed during eosinophilicCryptococcus neoformanspneumonia in C57BL/6 mice. Crystals were found associated with yeast cells and free in host cell cytoplasm. The crystals apparently formed because of the interaction of a host protein with the cryptococcal polysaccharide. Crystal formation likely contributes to pathogenesis by causing cellular damage.
Gamma Interferon and Lipopolysaccharide Interact at the Level of Transcription To Induce Tumor Necrosis Factor Alpha Expression
Authors: Lee Julia Y. , Sullivan Kathleen E. 
Published: July 2002

ABSTRACTLipopolysaccharide (LPS) is a very potent inducer of tumor necrosis factor alpha (TNF-α) expression from monocytes and macrophages. Another inflammatory cytokine, gamma interferon (IFN-γ), can potentiate the effects of LPS, but the mechanism is not thoroughly understood. Previous reports emphasized the ability of IFN-γ to upregulate CD14 expression (the receptor for LPS), and nearly all studies have utilized sequential stimulation with IFN-γ followed by LPS to exploit this phenomenon. This study demonstrates that IFN-γ can upregulate the effect of LPS at the level of transcription. Human monoblastic Mono-Mac-6 cells produced up to threefold-greater levels of TNF-α when simultaneously stimulated with LPS and IFN-γ compared to treatment with LPS alone. RNase protection studies showed a similar increase in RNA beginning as early as within 30 min. The synthesis of TNF-α mRNA in IFN-γ- and LPS-treated Mono-Mac-6 cells was also temporally prolonged even though the message turnover rate was identical to that seen in LPS stimulated cells. The modulatory effect of IFN-γ may be mediated by Jak2.
Spa Contributes to the Virulence of Type 18 Group A Streptococci
Authors: McLellan Duncan G. J. , Chiang Edna Y. , Courtney Harry S. , Hasty David L. , Wei Shirley C. , Hu Mary C. , Walls Michael A. , Bloom Jackie J. , Dale James B. 
Published: July 2002

ABSTRACTStreptococcal protective antigen (Spa) is a newly described surface protein of group A streptococci that was recently shown to evoke protective antibodies (J. B. Dale, E. Y. Chiang, S. Liu, H. S. Courtney, and D. L. Hasty, J. Clin. Investig. 103:1261–1268, 1999). In this study, we have determined the complete sequence of thespagene from type 18 streptococci. Purified, recombinant Spa protein evoked antibodies that were bactericidal against type 18 streptococci, confirming the presence of protective epitopes. Sera from patients with acute rheumatic fever contained antibodies against recombinant Spa, indicating that the Spa protein is expressed in vivo and is immunogenic in humans. To determine the role of Spa in the virulence of group A streptococci, we created a series of insertional mutants that were (i) Spa negative and M18 positive, (ii) Spa positive and M18 negative, and (iii) Spa negative and M18 negative. The mutants and the parent M18 strain (18-282) were used in assays to determine resistance to phagocytosis, growth in human blood, and mouse virulence. The results show that Spa is a virulence determinant of group A streptococci and that expression of both Spa and M18 is required for optimal virulence of type 18 streptococci.
Staphylococcus aureus
Induces Release of Bradykinin in Human Plasma
Authors: Mattsson Eva , Herwald Heiko , Cramer Henning , Persson Kristin , Sjöbring Ulf , Björck Lars 
Published: July 2002

ABSTRACT

Staphylococcus aureus
is a prominent human pathogen. Here we report that intact
S. aureus
bacteria activate the contact system in human plasma in vitro, resulting in a massive release of the potent proinflammatory and vasoactive peptide bradykinin. In contrast, no such effect was recorded with
Streptococcus pneumoniae.
In the activation of the contact system, blood coagulation factor XII and plasma kallikrein play central roles, and a specific inhibitor of these serine proteinases inhibited the release of bradykinin by
S. aureus
in human plasma. Furthermore, fragments of the cofactor H-kininogen of the contact system efficiently blocked bradykinin release. The results suggest that activation of the contact system at the surface of
S. aureus
and the subsequent release of bradykinin could contribute to the hypovolemic hypotension seen in patients with severe
S. aureus
sepsis. The data also suggest that the contact system could be used as a target in the treatment of
S. aureus
infections.
Differential Gene Expression from Two Transcriptional Units in the
cag
Pathogenicity Island of
Helicobacter pylori
Authors: Joyce Elizabeth A. , Gilbert Joanne V. , Eaton Kathryn A. , Plaut Andrew , Wright Andrew 
Published: July 2002

ABSTRACT

Infection with
Helicobacter pylori
strains containing the
cag
Pathogenicity Island (
cag
PAI) is strongly correlated with the development of severe gastric disease, including gastric and duodenal ulceration, mucosa-associated lymphoid tissue lymphoma, and gastric carcinoma. Although in vitro studies have demonstrated that the expression of genes within the
cag
PAI leads to the activation of a strong host inflammatory response, the functions of most
cag
gene products and how they work in concert to promote an immunological response are unknown. We developed a transcriptional reporter that utilizes urease activity and in which nine putative regulatory sequences from the
cag
PAI were fused to the
H. pylori ureB
gene. These fusions were introduced in single copies onto the
H. pylori
chromosome without disruption of the
cag
PAI. Our analysis indicated that while each regulatory region confers a reproducible amount of promoter activity under laboratory conditions, they differ widely in levels of expression. Transcription initiating upstream of
cag15
and upstream of
cag21
is induced when the respective fusion strains are cocultured with an epithelial cell monolayer. Results of mouse colonization experiments with an
H. pylori
strain carrying the
cag15-ureB
fusion suggested that this putative regulatory region appears to be induced in vivo, demonstrating the importance of the urease reporter as a significant development toward identifying in vivo-induced gene expression in
H. pylori
.
Tapeworm Infection Reduces Epithelial Ion Transport Abnormalities in Murine Dextran Sulfate Sodium-Induced Colitis
Authors: Reardon Colin , Sanchez Ana , Hogaboam Cory M. , McKay Derek M. 
Published: July 2002

ABSTRACTThe rat tapewormHymenolepis diminutawas used to test the hypothesis that helminth infection could modulate murine colitis. Mice were infected with fiveH. diminutacysticercoids, and colitis was evoked via free access to 4% (wt/vol) dextran sulfate sodium (DSS)-containing drinking water for 5 days. BALB/c mice were either infected withH. diminutaand 7 days later exposed to DSS (prophylactic strategy) or started on DSS and infected withH. diminuta48 h later (treatment strategy). Naive andH. diminuta-only-infected mice served as controls. On autopsy, colonic segments were processed for histological examination and myeloperoxidase (MPO) measurement or mounted in Ussing chambers for assessment of epithelial ion transport. Cytokines (gamma interferon [IFN-γ], interleukin 12 [IL-12], and IL-10) were measured in serum and colonic tissue homogenates. DSS treatment resulted in reduced ion responses (indicated by short-circuit current [Isc]) to electrical nerve stimulation, the cholinergic agonist carbachol, and the adenylate cyclase activator forskolin compared to controls.H. diminutainfection, either prophylactic or therapeutic, caused a significant (P< 0.05) amelioration of these DSS-induced irregularities in stimulated ion transport. In contrast, the histopathology (i.e., mixed immune cell infiltrate, edema, and ulcerative damage) and elevated MPO levels that accompany DSS colitis were unaffected by concomitantH. diminutainfection. Similarly, there were no significant differences in levels of IFN-γ, IL-12, or IL-10 in serum or tissue from any of the treatment groups at the time of autopsy. We suggest that abolishment of colitis-induced epithelial ion transport abnormalities byH. diminutainfection provides proof-of-principle data and speculate that helminth therapy may provide relief of disease symptoms in colitis.
Interleukin-6 Deficiency Influences Cytokine Expression in Susceptible BALB Mice Infected withLeishmania majorbut Does Not Alter the Outcome of Disease
Authors: Titus Richard G. , DeKrey Gregory K. , Morris Robin V. , Soares Milena B. P. 
Published: July 2002

ABSTRACTSince interleukin-6 (IL-6) may promote Th2 responses, we infected BALB IL-6-deficient (IL-6−/−) mice withLeishmania major. There was not a significant difference between the courses of infection (lesion size and parasite burden) in IL-6−/−and wild-type mice, but IL-6−/−mice expressed lower levels of Th2- and Th1-associated cytokines.
Involvement of Mitogen-Activated Protein Kinase Pathways inStaphylococcus aureusInvasion of Normal Osteoblasts
Authors: Ellington John K. , Elhofy Adam , Bost Kenneth L. , Hudson Michael C. 
Published: July 2002

ABSTRACTStaphylococcus aureusinvades osteoblasts and can persist in the intracellular environment. The present study examined the role of osteoblast mitogen-activated protein kinase (MAPK) pathways in bacterial invasion.S. aureusinfection of normal human and mouse osteoblasts resulted in an increase in the phosphorylation of the extracellular signal-regulated protein kinases (ERK 1 and 2). This stimulation of ERK 1 and 2 correlated with the time course ofS. aureusinvasion, and bacterial adherence induced the MAPK pathway. ERK 1 and 2 phosphorylation was time and dose dependent and required activeS. aureusgene expression for maximal induction. The nonpathogenicStaphylococcus carnosuswas also able to induce ERK 1 and 2 phosphorylation, albeit at lower levels thanS. aureus. Phosphorylation of the stress-activated protein kinases was increased in both infected human and mouse osteoblasts; however, the p38 MAPK pathway was not activated in response toS. aureus. Finally, the transcription factor c-Jun, but not Elk-1 or ATF-2, was phosphorylated in response toS. aureusinfection.
DNA Sequences Encoding CD4+and CD8+T-Cell Epitopes Are Important for Efficient Protective Immunity Induced by DNA Vaccination with aTrypanosoma cruziGene
Authors: Fujimura Adriana E. , Kinoshita Sheila S. , Pereira-Chioccola Vera L. , Rodrigues Mauricio M. 
Published: July 2002

ABSTRACTImmunization of BALB/c mice with a plasmid containing the gene forTrypanosoma cruzi trans-sialidase (TS) induced antibodies that inhibited TS enzymatic activity, CD4+Th1 and CD8+Tc1 cells, and protective immunity against infection. We used this model to obtain basic information on the requirement of CD4 or CD8 or B-cell epitopes for an effective DNA-induced immunity againstT. cruziinfection. For that purpose, mice were immunized with plasmids containing DNA sequences encoding (i) the entire TS protein, (ii) the TS enzymatic domain, (iii) the TS CD4+T-cell epitopes, (iv) the TS CD8+T-cell epitope, or (v) TS CD4+and CD8+T-cell epitopes. Plasmids expressing the entire TS or its enzymatic domain elicited similar levels of TS-inhibitory antibodies, γ interferon (IFN-γ)-producing T cells, and protective immunity against infection. Although the plasmid expressing TS CD4 epitopes was immunogenic, its protective efficacy against experimental infection was limited. The plasmid expressing the CD8 epitope was poorly immunogenic and provided little protective immunity. The reason for the limited priming of CD8+T cells was due to a requirement for CD4+T cells. To circumvent this problem, a plasmid expressing both CD4+and CD8+T-cell epitopes was produced. This plasmid generated levels of IFN-γ-producing T cells and protective immunity comparable to that of the plasmid expressing the entire catalytic domain of TS. Our observations suggest that plasmids expressing epitopes recognized by CD4+and CD8+T cells may have a better protective potential against infection withT. cruzi.
Cardiac Myosin Autoimmunity in Acute Chagas' Heart Disease
Authors: Leon Juan S. , Godsel Lisa M. , Wang Kegiang , Engman David M. 
Published: July 2002

ABSTRACTInfection withTrypanosoma cruzi, the agent of Chagas' disease, may induce antibodies and T cells reactive with self antigens (autoimmunity). Because autoimmunity is generally thought to develop during the chronic phase of infection, one hypothesis is that autoimmunity develops only after long-term, low-level stimulation of self-reactive cells. However, preliminary reports suggest that autoimmunity may begin during acuteT. cruziinfection. The goal of the present study was to investigate whether cardiac autoimmunity could be observed during acuteT. cruziinfection. A/J mice infected with the Brazil strain ofT. cruzifor 21 days developed severe myocarditis, accompanied by humoral and cellular autoimmunity. Specifically,T. cruziinfection induced immunoglobulin G (IgG) autoantibodies and delayed type hypersensitivity (DTH) to cardiac myosin. This autoimmunity resembles that which develops in A/J mice immunized with myosin in complete Freund's adjuvant in that myosin-specific antibodies and DTH responses both develop by 21 days postinfection or postimmunization. While the levels of myosin IgG inT. cruzi-infected mice were slightly lower than those in myosin-immunized mice, the magnitude of myosin DTH in the two groups was statistically equivalent. In contrast, C57BL/6 mice, which are resistant to myosin-induced myocarditis and its associated autoimmunity, developed undetectable or low levels of myosin IgG and did not exhibit myosin DTH or myocarditis uponT. cruziinfection. Therefore, humoral and cellular cardiac autoimmunity can develop during acuteT. cruziinfection in the genetically susceptible host.