bluuebunny/crossref_metadata_2025_split huggingface dataset:
Helicobacter pylori
Mutants Defective in RuvC Holliday Junction Resolvase Display Reduced Macrophage Survival and Spontaneous Clearance from the Murine Gastric Mucosa
Authors: Loughlin Michael F. , Barnard Faye M. , Jenkins David , Sharples Gary J. , Jenks Peter J. 
Published: March 2003

ABSTRACT

Homologous recombination contributes to the extraordinary genetic diversity of
Helicobacter pylori
and may be critical for surface antigen expression and adaptation to environmental challenges within the stomach. We generated isogenic, nonpolar
H. pylori ruvC
mutants to investigate the function of RuvC, a Holliday junction endonuclease that resolves recombinant joints into nicked duplex products. Inactivation of
ruvC
reduced the frequency of homologous recombination of
H. pylori
between 17- and 45-fold and increased sensitivity to DNA-damaging agents and the antimicrobial agents levofloxacin and metronidazole. The
H. pylori ruvC
mutants were more susceptible to oxidative stress and exhibited reduced survival within macrophages. Experiments with the
H. pylori
SS1 mouse model revealed that the 50% infective dose of the
ruvC
mutant was approximately 100-fold higher than that of the wild-type SS1 strain. Although the
ruvC
mutant was able to establish colonization with bacterial loads that were initially similar to those of the parental SS1 strain, infection was spontaneously cleared from the murine gastric mucosa over periods that varied from 36 to 67 days. These results demonstrate that, in this infection model, RuvC is essential for continued survival of
H. pylori
in vivo and raises the possibility that inactivation of
ruvC
might be of value in an attenuated vaccine strain.
Induction of Mosquitocidal Activity in Mice Immunized withAnopheles gambiaeMidgut cDNA
Authors: Foy B. D. , Magalhaes T. , Injera W. E. , Sutherland I. , Devenport M. , Thanawastien A. , Ripley D. , Cárdenas-Freytag L. , Beier J. C. 
Published: March 2003

ABSTRACTVaccines that induce mosquito-killing (mosquitocidal) activity could substantially reduce the transmission of certain mosquito-borne diseases, especially vaccines against African malaria vectors, such as the mosquitoAnopheles gambiae. To generate and characterize antimosquito immunity we immunized groups of mice with two individualA. gambiaemidgut cDNAs,Ag-Aper1(a secreted peritrophic matrix protein) andAgMuc1(a midgut-bound mucin), and anA. gambiaemidgut cDNA library from blood-fed mosquitoes. We observed significantly increased mortality among mosquitoes that fed on either theAgMuc1- or the cDNA library-immunized mice compared to that of controls, but no differences were observed among those fed onAg-Aper1-immunized mice. Analysis of the humoral and cellular immune responses from mice showed that the induced mosquitocidal effect was associated with immune profiles characterized by elevated tumor necrosis factor alpha and gamma interferon cytokine levels and very low antibody titers. Furthermore, an additional immunization of cDNA library-immunized mice with midgut protein shifted immunity toward a Th2-type immune response, characterized by elevated antibody titers and high interleukin-5 and interleukin-10 cytokine levels; importantly, mosquitoes feeding on these mice exhibited no undo mortality. Finally, when immune sera was ingested by mosquitoes through a membrane feeder, no effect on mosquito mortality was observed, indicating that serum factors alone were not responsible for the mosquitocidal effect. Our results demonstrate that mosquitocidal immunity in mice can be consistently generated by midgut cDNA immunization and suggest this cDNA-induced mosquitocidal immunity is cell mediated.
Different Genetic Control of Cutaneous and Visceral Disease after
Leishmania major
Infection in Mice
Authors: Vladimirov Vladimir , Badalová Jana , Svobodová Milena , Havelková Helena , Hart Augustinus A. M. , Blažková Hana , Demant Peter , Lipoldová Marie 
Published: March 2003

ABSTRACT

The mouse strains BALB/cHeA (BALB/c) and STS/A (STS) are susceptible and resistant to
Leishmania major-
induced disease, respectively. We analyzed this difference using recombinant congenic (RC) BALB/c-c-STS/Dem (CcS/Dem) strains that carry different random subsets of 12.5% genes of the strain STS in a BALB/c background. Previously, testing the resistant strain CcS-5, we found five novel
Lmr
(
Leishmania major
response) loci, each associated with a different combination of pathological and immunological reactions. Here we analyze the response of RC strain CcS-16, which is even more susceptible to
L. major
than BALB/c. In the (CcS-16 × BALB/c)F
2
hybrids we mapped three novel loci that influence cutaneous or visceral pathology
. Lmr14
(chromosome 2) controls splenomegaly and hepatomegaly. On the other hand
Lmr15
(chromosome 11) determines hepatomegaly only, and
Lmr13
(chromosome 18) determines skin lesions only. These data confirm the complex control of
L. major-
induced pathology, where cutaneous and visceral pathology are controlled by different combinations of genes. It indicates organ-specific control of antiparasite responses. The definition of genes controlling these responses will permit a better understanding of pathways and genetic diversity underlying the different disease phenotypes.
Soluble Factors Released byToxoplasma gondii-Infected Astrocytes Down-Modulate Nitric Oxide Production by Gamma Interferon-Activated Microglia and Prevent Neuronal Degeneration
Authors: Rozenfeld Claudia , Martinez Rodrigo , Figueiredo Rodrigo T. , Bozza Marcelo T. , Lima Flávia R. S. , Pires Ana Lúcia , Silva Patrícia M. , Bonomo Adriana , Lannes-Vieira Joseli , De Souza Wanderley , Moura-Neto Vivaldo 
Published: March 2003

ABSTRACTThe maintenance of a benign chronicToxoplasma gondiiinfection is mainly dependent on the persistent presence of gamma interferon (IFN-γ) in the central nervous system (CNS). However, IFN-γ-activated microglia are paradoxically involved in parasitism control and in tissue damage during a broad range of CNS pathologies. In this way, nitric oxide (NO), the main toxic metabolite produced by IFN-γ-activated microglia, may cause neuronal injury duringT. gondiiinfection. Despite the potential NO toxicity, neurodegeneration is not a common finding during chronicT. gondiiinfection. In this work, we describe a significant down-modulation of NO production by IFN-γ-activated microglia in the presence of conditioned medium ofT. gondii-infected astrocytes (CMi). The inhibition of NO production was paralleled with recovery of neurite outgrowth when neurons were cocultured with IFN-γ-activated microglia in the presence of CMi. Moreover, the modulation of NO secretion and the neuroprotective effect were shown to be dependent on prostaglandin E2(PGE2) production byT. gondii-infected astrocytes and autocrine secretion of interleukin-10 (IL-10) by microglia. These events were partially eliminated when infected astrocytes were treated with aspirin and cocultures were treated with anti-IL-10 neutralizing antibodies and RP-8-Br cyclic AMP (cAMP), a protein kinase A inhibitor. Further, the modulatory effects of CMi were mimicked by the presence of exogenous PGE2and by forskolin, an adenylate cyclase activator. Altogether, these data point to aT. gondii-triggered regulatory mechanism involving PGE2secretion by astrocytes and cAMP-dependent IL-10 secretion by microglia. This may reduce host tissue inflammation, thus avoiding neuron damage during an established Th1 protective immune response.
Recombinant Gamma Interferon Stimulates Signal Transduction and Gene Expression in Alveolar Macrophages In Vitro and in Tuberculosis Patients
Authors: Condos Rany , Raju Bindu , Canova Antony , Zhao Ben-Yang , Weiden Michael , Rom William N. , Pine Richard 
Published: March 2003

ABSTRACTTuberculosis is the seventh leading cause of morbidity and mortality in the world, with eight million cases per year. Animal and human studies demonstrate an enrichment of CD4 cells at sites of disease, with a more favorable clinical course when there is a Th1 response with the presence of gamma interferon (IFN-γ). We previously treated patients who had multidrug-resistant tuberculosis with recombinant IFN-γ (rIFN-γ) in aerosol form and were able to convert smear-positive cases to smear negative with 12 treatments over 1 month. We hypothesized that rIFN-γ would induce signal transducer and activator of transcription (STAT) and interferon regulatory factor (IRF) binding activity in alveolar macrophages (AM). AM treated in vitro showed clear upregulation of STAT-1 and IRF-1 by rIFN-γ. STAT-1 was not activated and IRF-1 was only weakly induced after 1 day of infection byMycobacterium tuberculosisTN913. In bronchoalveolar lavage (BAL) cells obtained from 10 of 10 tuberculosis patients 10 ± 2 days post-antituberculosis treatment, there was no detectable STAT-1 or IRF-1 DNA-binding activity. After 4 weeks of treatment with rIFN-γ aerosol in addition to the antituberculosis drugs, 10 of 10 patients had increased STAT-1, IRF-1, and/or IRF-9 DNA-binding activity in BAL cells from lung segments shown radiographically to be involved and in those shown to be uninvolved. Symptoms and chest radiographs improved, and amounts of macrophage inflammatory cytokines and human immunodeficiency virus type 1 (HIV-1) viral loads (in five of five HIV-1-coinfected patients) declined in the second BAL specimens. rIFN-γaerosol induces signal transduction and gene expression in BAL cells and should be evaluated for efficacy in a randomized, controlled clinical trial.
Exposure of Immunocompetent Adult Mice to
Pneumocystis carinii
f. sp.
muris
by Cohousing: Growth of
P
.
carinii
f. sp.
muris
and Host Immune Response
Authors: An Chun Li , Gigliotti Francis , Harmsen Allen G. 
Published: March 2003

ABSTRACT

There has been emerging evidence that immunocompetent hosts can harbor
Pneumocystis
in their lungs. The purpose of this study was to determine the kinetics of
Pneumocystis carinii
f. sp.
muris
infection in adult immunocompetent mice and the host immune response to the organisms. To accomplish this, we exposed adult immunocompetent mice to SCID mice infected with
P
.
carinii
f. sp.
muris
by cohousing. We found that
P
.
carinii
f. sp.
muris
was detectable in the lungs of cohoused immunocompetent mice by PCR by 3 weeks after the beginning of cohousing. At about 4 weeks of cohousing,
P
.
carinii
f. sp.
muris
was readily detectable in the lungs of mice by microscopic techniques. Also at this time,
P
.
carinii
f. sp.
muris-
specific immunoglobulin G was found in the sera of the mice, and CD62
low
CD4- and CD8-positve T cells accumulated in the lungs. Shortly after this immune response, the
P
.
carinii
f. sp.
muris
organisms were cleared from the lungs. Adult mice cohoused for only 1 week also contained
P
.
carinii
f. sp.
muris
cysts detectable by silver staining at 5 and 6 weeks after the beginning of cohousing. We also found that the
P
.
carinii
f. sp.
muris
organisms grew to greater numbers in the lungs of BALB/c mice than in those of C57BL6 mice. This indicates that immunocompetent hosts develop a mild infection with
P
.
carinii
f. sp.
muris
which resolves in 5 to 6 weeks when there is a detectable immune response to the organism. Once an acquired immune response was initiated, the
P
.
carinii
f. sp.
muris
organisms were quickly eliminated without clinical signs of disease.
Transmission ofAnaplasma phagocytophilumtoIxodes ricinusTicks from Sheep in the Acute and Post-Acute Phases of Infection
Authors: Ogden N. H. , Casey A. N. J. , Woldehiwet Z. , French N. P. 
Published: March 2003

ABSTRACTA total of 60 sheep were exposed toAnaplasma phagocytophiluminfection on an enclosed area ofIxodes ricinus-infested pasture in North Wales, United Kingdom, and rapidly acquired acuteA. phagocytophiluminfections detectable by PCR and blood smear examination. Of the ticks that had engorged in the previous instar on infected sheep, 52% of adult ticks and 28% of nymphs were PCR positive; a significant, 10-fold increase in prevalence compared to that of ticks that engorged on sheep preinfection was observed (P= 0.015). The likelihood that ticks were PCR positive, after feeding on the sheep and molting to the next instar, increased marginally with increasing numbers of infected neutrophils per milliliter of blood of their sheep host (P= 0.068) and increased significantly when they were collected from sheep carrying higher numbers of adult female ticks (P= 0.017), but increasing numbers of feeding nymphs had a significant negative effect on transmission (P= 0.049). The numbers of circulating neutrophils and of infected neutrophils also varied significantly with the numbers of ticks feeding on the sheep when the blood was collected. Our study suggests that ruminants are efficient reservoirs ofA. phagocytophilumduring the acute and post-acute phases of infection. The risk of ruminant-derived infections may, however, be strongly affected by variations in tick densities, which may influence transmission from acutely infected animals via effects on the numbers of infected cells in the blood and possibly by within-skin modulation of infection.
Major Histocompatibility Complex Heterozygote Superiority during Coinfection
Authors: McClelland Erin E. , Penn Dustin J. , Potts Wayne K. 
Published: March 2003

ABSTRACTGenes of the major histocompatibility complex (MHC) play a critical role in immune recognition, and many alleles confer susceptibility to infectious and autoimmune diseases. How these deleterious alleles persist in populations is controversial. One hypothesis postulates that MHC heterozygote superiority emerges over multiple infections because MHC-mediated resistance is generally dominant and many allele-specific susceptibilities to pathogens will be masked by the resistant allele in heterozygotes. We tested this hypothesis by using experimental coinfections withSalmonella enterica(serovar Typhimurium C5TS) and Theiler's murine encephalomyelitis virus (TMEV) in MHC-congenic mouse strains where one haplotype was resistant toSalmonellaand the other was resistant to TMEV. MHC heterozygotes were superior to both homozygotes in 7 out of 8 comparisons (P= 0.0024), and the mean standardized pathogen load of heterozygotes was reduced by 41% over that of homozygotes (P= 0.01). In contrast, no heterozygote superiority was observed when the MHC haplotype combinations had similar susceptibility profiles to the two pathogens. This is the first experimental evidence for MHC heterozygote superiority against multiple pathogens, a mechanism that would contribute to the evolution of MHC diversity and explain the persistence of alleles conferring susceptibility to disease.
Pneumolysin-Dependent and -Independent Gene Expression Identified by cDNA Microarray Analysis of THP-1 Human Mononuclear Cells Stimulated byStreptococcus pneumoniae
Authors: Rogers P. David , Thornton Justin , Barker Katherine S. , McDaniel D. Olga , Sacks Gordon S. , Swiatlo Edwin , McDaniel Larry S. 
Published: March 2003

ABSTRACTPneumolysin is an important virulence factor ofStreptococcus pneumoniae, interacting with the membranes of host cells to elicit a multitude of inflammatory responses. We used cDNA microarrays to identify genes which are responsive toS.pneumoniaein a pneumolysin-dependent and -independent fashion. The THP-1 human monocytic cell line was coincubated for 3 h with medium alone, with the virulent type 2S.pneumoniaestrain D39, or with the isogenic strain PLN, which does not express pneumolysin. RNA was isolated from the monocytes and hybridized on cDNA microarrays. Of 4,133 genes evaluated, 142 were found to be responsive in a pneumolysin-dependent fashion, whereas 40 were found to be responsive independent of pneumolysin. Genes that were up-regulated in cells exposed to D39 relative to those exposed to PLN included genes encoding proteins such as mannose binding lectin 1, lysozyme, α-1 catenin, cadherin 17, caspases 4 and 6, macrophage inflammatory protein 1β (MIP-1β), interleukin 8 (IL-8), monocyte chemotactic protein 3 (MCP-3), IL-2 receptor β (IL-2Rβ), IL-15 receptor α (IL-15Rα), interferon receptor 2, and prostaglandin E synthase. Down-regulated genes included those encoding complement component receptor 2/CD21, platelet-activating factor acetylhydrolase, and oxidized low-density lipoprotein receptor 1 (OLR1). Pneumolysin-independent responses included down-regulation of the genes encoding CD68, CD53, CD24, transforming growth factor β2, and signal transducers and activators of transcription 1. These results demonstrate the striking effects of pneumolysin on the host cell upon exposure toS.pneumoniae.
Leishmania donovani-Induced Expression of Suppressor of Cytokine Signaling 3 in Human Macrophages: a Novel Mechanism for Intracellular Parasite Suppression of Activation
Authors: Bertholet Sylvie , Dickensheets Harold L. , Sheikh Faruk , Gam Albert A. , Donnelly Raymond P. , Kenney Richard T. 
Published: March 2003

ABSTRACTLeishmania donovaniprotozoan parasites, the causative agent of visceral leishmaniasis, establish an infection partly by interfering with cytokine signaling in the host macrophages. Therefore, we investigated the expression of the suppressor of cytokine signaling (SOCS) genes in human macrophages infected withL.donovani. The expression of SOCS3 mRNA was induced transiently after exposure to live or heat-killed parasites, but not purified lipophosphoglycan, while that of other SOCS genes remained unchanged. SOCS3 gene expression was not dependent on phagocytosis or on cytokines released byL.donovani-infected macrophages, such as interleukin-1β or tumor necrosis factor alpha. In addition,Leishmaniaused a different signaling pathway(s) than bacterial lipopolysaccharide to induce SOCS3 mRNA, as indicated by the kinetics of induction and sensitivity to polymyxin B inhibition. Finally, phosphorylation of the STAT1 transcription factor was significantly reduced inL.donovani-infected macrophages and required de novo transcription. The induction of SOCS3 provides a potent inhibitory mechanism by which intracellular microorganisms may suppress macrophage activation and interfere with the host immune response.
Salmonella
Infection Induces a Hypersecretory Phenotype in Human Intestinal Xenografts by Inducing Cyclooxygenase 2
Authors: Bertelsen Lone S. , Paesold Guenther , Eckmann Lars , Barrett Kim E. 
Published: March 2003

ABSTRACT

Enteric
Salmonella
infection is accompanied by inflammation and diarrhea, and yet little is known about its effects on intestinal epithelial physiology. Since species differences limit the utility of animal tissues and cell lines lack relevant cell-cell interactions, we have used a human model of fetal intestine grown as xenografts in SCID mice. We investigated here the effects of
Salmonella
enterica
serovar Typhimurium SL1344 on xenograft ion transport. Harvested xenografts were stripped of seromuscular layers by blunt dissection, infected with
Salmonella
, and mounted in Ussing chambers.
Salmonella
infection for 1 h increased baseline ion transport without altering tissue conductance or morphology. The increased transport was blocked by the cyclooxygenase inhibitor, indomethacin, or the specific Cox-2 inhibitor, NS-398. Further, xenografts infected for 2 h showed increased secretory responses to the calcium-dependent agonist, carbachol, and the cyclic AMP-dependent agonists prostaglandin E
2
(PGE
2
) and forskolin, which were blocked by indomethacin. Western blot experiments revealed that infection was accompanied by increased cyclooxygenase 2 (Cox-2) expression, with no change in Cox-1 levels. Immunoassay demonstrated basolateral PGE
2
release, which was inhibited by indomethacin. Histological examination of infected xenografts illustrated that upregulated Cox-2 expression was restricted to the epithelium and that little or no invasion of the tissue by
Salmonella
occurred for up to 2 h. In summary,
Salmonella
infection rapidly increases Cox-2 expression in human intestinal tissue, accounting for increased epithelial ion transport characteristic of infectious diarrhea.
Interactions betweenBrucella melitensisand Human Phagocytes: Bacterial Surface O-Polysaccharide Inhibits Phagocytosis, Bacterial Killing, and Subsequent Host Cell Apoptosis
Authors: Fernandez-Prada Carmen M. , Zelazowska Elzbieta B. , Nikolich Mikeljon , Hadfield Ted L. , Roop R. Martin , Robertson Gregory L. , Hoover David L. 
Published: March 2003

ABSTRACTBrucellae are gram-negative intracellular pathogens that survive and multiply within host phagocytic cells. Smooth organisms present O-polysaccharides (OPS) on their surface. ThewboAgene, which codes for the enzyme glycosyl transferase, is essential for the assembly of O-chain inBrucella. Deletion ofwboAin smooth, virulentB. melitensis16M results in a rough mutant designated WRR51. UnlikeB. abortus, both smooth and rough strains ofB. melitensisare resistant to complement-mediated killing. To determine the role of surface OPS in the interactions ofB. melitensiswith monocytes/macrophages (M/M), 16M and WRR51 were transformed with the plasmid pBBR1MCS-6y encoding green fluorescent protein, and the transformants were used to infect human mononuclear phagocytes with and without fresh human serum as a source of complement. Human monocytes were cultured in the presence of macrophage colony-stimulating factor to allow their differentiation into macrophages during the course of infection. Intracellular bacteria were easily visualized using fluorescence microscopy. Infection in M/M, identified by surface staining and fate of infected phagocytes, was quantitated by flow cytometry. Rough bacteria were internalized, with no requirement for opsonization by serum, at a higher rate than smooth organisms. SmoothB. melitensissurvived and multiplied for at least 6 days inside M/M, but rough organisms were eliminated by death of the infected cells. In human monocytes cultured for 1 day without serum in order to trigger the apoptotic pathway, infection by rough brucellae accelerated phagocyte death; smooth brucellae inhibited apoptosis. This study suggests that the presence of surface OPS on liveB. melitensisbenefits the bacterium by preventing the death of macrophages,Brucella's preferred target for intracellular replication.
Flagellin of EnteropathogenicEscherichia coliStimulates Interleukin-8 Production in T84 Cells
Authors: Zhou Xin , Girón Jorge A. , Torres Alfredo G. , Crawford J. Adam , Negrete Erasmo , Vogel Stefanie N. , Kaper James B. 
Published: March 2003

ABSTRACTThe type III secretion system (TTSS) of enteropathogenicEscherichia coli(EPEC) has been associated with the ability of these bacteria to induce secretion of proinflammatory cytokines, including interleukin-8 (IL-8), in cultured epithelial cells. However, the identity of the effector molecule directly involved in this event is unknown. In this study, we determined that the native flagellar filament and its flagellin monomer are activators of IL-8 release in T84 epithelial cells. Supernatants of wild-type EPEC strain E2348/69 and its isogenic mutants deficient in TTSS (escN) and in production of intimin (eae), grown in Luria-Bertani broth, elicited similar amounts of IL-8 secretion by T84 cells. In contrast, supernatants of EPECfliCmutants and of B171, a nonflagellated EPEC strain, were defective in inducing IL-8 release, a phenotype that was largely restored by complementation of thefliCgene in the mutant lacking flagella. Purified flagella fromE. coliK-12, EPEC serotypes H6 and H34, and enterohemorrhagicE. coliserotype H7 all induced IL-8 release in T84 cells. Induction of IL-8 by purified flagella or His-tagged FliC from EPEC strain E2348/69 was dose dependent and was blocked by a polyclonal anti-H6 antibody. Finally, the mitogen-activated protein kinases (Erk1 and -2 and Jnk) were phosphorylated in flagellin-treated T84 cells, and inhibition of the p38 and Erk pathways significantly decreased the IL-8 response induced by EPEC flagellin. Our data clearly indicate that FliC of EPEC is sufficient to induce IL-8 release in T84 cells and that activation of the Erk and p38 pathways is required for IL-8 induction.