bluuebunny/crossref_metadata_2025_split huggingface dataset:
Intracellular Adhesion Molecule 1 Plays a Key Role in Acquired Immunity to Salmonellosis
Authors: Clare Simon , Goldin Robert , Hale Christine , Aspinall Richard , Simmons Cameron , Mastroeni Pietro , Dougan Gordon 
Published: September 2003

ABSTRACTThis study investigated the role of intracellular adhesion molecule 1 (ICAM-1) duringSalmonella entericaserovar Typhimurium infection of mice. We show that ICAM-1 is expressed in and around granulomas on day 4 of infection in wild-type mice. However, when naive ICAM-1−/−mice were challenged with a sublethal dose of serovar Typhimurium, there were no detectable differences in systemic bacterial burden over the first 9 days of infection compared to wild-type control mice. When mice were immunized with theS. entericaserovar Typhimurium vaccine strain SL2361 and then challenged with the virulentS. entericaserovar Typhimurium strain C5, 100% of the ICAM-1−/−mice succumbed to infection, compared to 30% of wild-type mice. T-cell responses, as measured by activation via interleukin-2 production, as well as antibody responses were comparable in the ICAM-1−/−and wild-type mice. Following challenge, counts in organs were significantly higher in the ICAM-1−/−mice, and histological examination of organs showed pathological differences. Strain SL3261-immunized wild-type mice had cellular infiltrate and normal granuloma formation in the liver and spleen on days 5 and 10 after challenge with strain C5. ICAM-1−/−mice had a similar infiltrate on day 5, whereas on day 10 the infiltrate was more widespread and there were fewer macrophages associated with the granulomas. High circulating levels of tumor necrosis factor alpha and gamma interferon, as well as a high burden of strain C5 in the blood, accompanied the differences in histopathology. In this study we show that ICAM-1 plays a critical role during rechallenge of immunized mice with virulentS. entericaserovar Typhimurium.
The Ability To Replicate in Macrophages Is Conserved between
Yersinia pestis
and
Yersinia pseudotuberculosis
Authors: Pujol Céline , Bliska James B. 
Published: September 2003

ABSTRACT

Yersinia pestis
, the agent of plague, has arisen from a less virulent pathogen,
Yersinia pseudotuberculosis
, by a rapid evolutionary process. Although
Y. pestis
displays a large number of virulence phenotypes, it is not yet clear which of these phenotypes descended from
Y. pseudotuberculosis
and which were acquired independently.
Y. pestis
is known to replicate in macrophages, but there is no consensus in the literature on whether
Y. pseudotuberculosis
shares this property. We investigated whether the ability to replicate in macrophages is common to
Y. pestis
and
Y. pseudotuberculosis
or is a unique phenotype of
Y. pestis
. We also examined whether a chromosomal type III secretion system (TTSS) found in
Y. pestis
is present in
Y. pseudotuberculosis
and whether this system is important for replication of
Yersinia
in macrophages. A number of
Y. pestis
and
Y. pseudotuberculosis
strains of different biovars and serogroups, respectively, were tested for the ability to replicate in primary murine macrophages. Two
Y. pestis
strains (EV766 and KIM10
+
) and three
Y. pseudotuberculosis
strains (IP2790c, IP2515c, and IP2666c) were able to replicate in macrophages with similar efficiencies. Only one of six strains tested, the
Y. pseudotuberculosis
YPIII(p
−
) strain, was defective for intracellular replication. Thus, the ability to replicate in macrophages is conserved in
Y. pestis
and
Y. pseudotuberculosis
. Our results also indicate that a homologous TTSS is present on the chromosomes of
Y. pestis
and
Y. pseudotuberculosis
and that this secretion system is not required for replication of these bacteria in macrophages.
Heterogeneous Surface Expression of EspA Translocon Filaments by
Escherichia coli
O157:H7 Is Controlled at the Posttranscriptional Level
Authors: Roe Andrew J. , Yull Helen , Naylor Stuart W. , Woodward Martin J. , Smith David G. E. , Gally David L. 
Published: September 2003

ABSTRACT

Type III secretion systems of enteric bacteria enable translocation of effector proteins into host cells. Secreted proteins of verotoxigenic
Escherichia coli
O157 strains include components of a translocation apparatus, EspA, -B, and -D, as well as “effectors” such as the translocated intimin receptor (Tir) and the mitochondrion-associated protein (Map). This research has investigated the regulation of
LEE4
translocon proteins, in particular EspA. EspA filaments could not be detected on the bacterial cell surface when
E. coli
O157:H7 was cultured in M9 minimal medium but were expressed from only a proportion of the bacterial population when cultured in minimal essential medium modified with 25 mM HEPES. The highest proportions of EspA-filamented bacteria were detected in late exponential phase, after which filaments were lost rapidly from the bacterial cell surface. Our previous research had shown that human and bovine
E. coli
O157:H7 strains exhibit marked differences in EspD secretion levels. Here it is demonstrated that the proportion of the bacterial population expressing EspA filaments was associated with the level of EspD secretion. The ability of individual bacteria to express EspA filaments was not controlled at the level of
LEE1
-
4
operon transcription, as demonstrated by using both β-galactosidase and green fluorescent protein (GFP) promoter fusions. All bacteria, whether expressing EspA filaments or not, showed equivalent levels of GFP expression when
LEE1-4
translational fusions were used. Despite this, the
LEE4
-
espADB
mRNA was more abundant from populations with a high proportion of nonsecreting bacteria (low secretors) than from populations with a high proportion of secreting and therefore filamented bacteria (high secretors). This research demonstrates that while specific environmental conditions are required to induce
LEE1-4
expression, a further checkpoint exists before EspA filaments are produced on the bacterial surface and secretion of effector proteins occurs. This checkpoint in
E. coli
O157:H7 translocon expression is controlled by a posttranscriptional mechanism acting on
LEE4
-
espADB
mRNA. The heterogeneity in EspA filamentation could arise from phase-variable expression of regulators that control this posttranscriptional mechanism.
Iron Superoxide Dismutases Targeted to the Glycosomes ofLeishmania chagasiAre Important for Survival
Authors: Plewes Katherine A. , Barr Stephen D. , Gedamu Lashitew 
Published: September 2003

ABSTRACTKinetoplastid glycosomes contain a variety of metabolic activities, such as glycolysis, β-oxidation of fatty acids, lipid biosynthesis, and purine salvage. One advantage of sequestering metabolic activities is the avoidance of cellular oxidative damage by reactive oxygen species produced as a by-product of metabolism. Little is known about how glycosomes themselves withstand these toxic metabolites. We previously isolated an iron superoxide dismutase fromLeishmania chagasithat is expressed at low levels in the early logarithmic promastigote stage and increases toward the stationary promastigote and amastigote stages. We have since identified a second highly homologousLcfesodbgene that is expressed at high levels in the early logarithmic promastigote stage and decreases toward the stationary promastigote and amastigote stages. Localization studies using green fluorescent protein fusions have revealed that LcFeSODB1 and LcFeSODB2 are localized within the glycosomes by the last three amino acids of their carboxyl termini. To better understand the specific role that FeSODB plays in parasite growth and survival, a single-allele knockout of theLcfesodb1gene was generated. The parasites with these genes exhibited a significant reduction in growth when endogenous superoxide levels were increased with paraquat in culture. Furthermore, the FeSODB1-deficient parasites exhibited a significant reduction in survival within human macrophages. Our results suggest that LcFeSODB plays an important role in parasite growth and survival by protecting glycosomes from superoxide toxicity.
Acid-Adaptive Genes of
Helicobacter pylori
Authors: Wen Yi , Marcus Elizabeth A. , Matrubutham Uday , Gleeson Martin A. , Scott David R. , Sachs George 
Published: September 2003

ABSTRACT

Helicobacter pylori
is the only neutralophile that has been able to colonize the human stomach by using a variety of acid-adaptive mechanisms. One of the adaptive mechanisms is increased buffering due to expression of an acid-activated inner membrane urea channel, UreI, and a neutral pH-optimum intrabacterial urease. To delineate other possible adaptive mechanisms, changes in gene expression in response to acid exposure were examined using genomic microarrays of
H. pylori
exposed to different levels of external pH (7.4, 6.2, 5.5, and 4.5) for 30 min in the absence and presence of 5 mM urea. Gene expression was correlated with intrabacterial pH measured using 2′,7′-bis-(2-carboxyethyl)-5-carboxyfluorescein and compared to that observed with exposure to 42°C for 30 min. Microarrays containing the 1,534 open reading frames of
H. pylori
strain 26695 were hybridized with cDNAs from control (pH 7.4; labeled with Cy3) and acidic (labeled with Cy5) conditions. The intrabacterial pH was 8.1 at pH 7.4, fell to 5.3 at pH 4.5, and rose to 6.2 with urea. About 200 genes were up-regulated and ∼100 genes were down-regulated at pH 4.5 in the absence of urea, and about half that number changed in the presence of urea. These genes included pH-homeostatic, transcriptional regulatory, motility, cell envelope, and pathogenicity genes. The up-regulation of some pH-homeostatic genes was confirmed by real-time PCR. There was little overlap with the genes induced by temperature stress. These results suggest that
H. pylori
has evolved multifaceted acid-adaptive mechanisms enabling it to colonize the stomach that may be novel targets for eliminating infection.
An Attenuated Strain of the Facultative Intracellular BacteriumFrancisella tularensisCan Escape the Phagosome of Monocytic Cells
Authors: Golovliov Igor , Baranov Vladimir , Krocova Zuzana , Kovarova Hana , Sjöstedt Anders 
Published: September 2003

ABSTRACTThe facultative intracellular bacteriumFrancisella tularensisis a highly virulent and contagious organism, and little is known about its intracellular survival mechanisms. We studied the intracellular localization of the attenuated human vaccine strain,F. tularensisLVS, in adherent mouse peritoneal cells, in mouse macrophage-like cell line J774A.1, and in human macrophage cell line THP-1. Confocal microscopy of infected J774A.1 cells indicated that during the first hour of infection the bacteria colocalized with the late endosomal-lysosomal glycoprotein LAMP-1, but within 3 h this colocalization decreased significantly from approximately 60% to 30%. Transmission electron microscopy revealed that >90% of bacteria were not enclosed by a phagosomal membrane after 2 h of infection, and some bacteria were in vacuoles that were only partially surrounded by a limiting membrane. Similar findings were obtained with all three host cell types. Immunoelectron microscopy performed with anF. tularensisLVS-specific polyclonal rabbit antiserum showed that the antiserum stained a thick, evenly distributed capsule-like material in bacteria grown in broth. In contrast, intracellularF. tularensisLVS cells were only marginally stained with this antiserum. Instead, most of the immunoreactive material was diffusely localized in the phagosomes or was associated with the phagosomal membrane. Our findings indicate thatF. tularensisLVS is able to escape from the phagosomes of macrophages via a mechanism that may involve degradation of the phagosomal membrane.
Entry and Intracellular Replication ofEscherichia coliK1 in Macrophages Require Expression of Outer Membrane Protein A
Authors: Sukumaran Sunil K. , Shimada Hiroyuki , Prasadarao Nemani V. 
Published: September 2003

ABSTRACTInteractions betweenEscherichia coliK1, which causes meningitis in neonates, and macrophages have not been explored well. In this study we found thatE. coliK1 was able to enter, survive, and replicate intracellularly in both murine and human macrophage cell lines, as well as in monocytes and macrophages of newborn rats. In addition, we demonstrated that OmpA+E. colialso enters and replicates in human peripheral blood monocytes in vitro. Outer membrane protein A (OmpA) expression onE. colicontributes to binding to macrophages, phagocytosis, and survival within macrophages. Opsonization with either complement proteins or antibody is not required for uptake and survival of the bacteria within the macrophages. Transmission electron microscopy and immunocytochemistry studies with the infected macrophages indicated that OmpA+E. colimultiplies enormously in a single phagosome and bursts the cell. Internalization of OmpA+E. coliby RAW 264.7 cells occurred by both actin- and microtubule-dependent processes, which are independent of RGD-mediated integrin receptors. Internalization and intracellular survival within phagocytic cells thus may play an important role in the development of bacteremia, which is crucial forE. colicrossing of the blood-brain barrier.
Identification and Characterization of HtsA, a Second Heme-Binding Protein Made byStreptococcus pyogenes
Authors: Lei Benfang , Liu Mengyao , Voyich Jovanka M. , Prater Christopher I. , Kala Subbarao V. , DeLeo Frank R. , Musser James M. 
Published: September 2003

ABSTRACTGroup A streptococci (GAS) can use heme and hemoproteins as sources of iron. However, the machinery for heme acquisition in GAS has not been firmly revealed. Recently, we identified a novel heme-associated cell surface protein (Shp) made by GAS. Theshpgene is cotranscribed with eight downstream genes, includingspy1795,spy1794, andspy1793encoding a putative ABC transporter (designated HtsABC). In this study,spy1795(designatedhtsA) was cloned from a serotype M1 strain, and recombinant HtsA was overexpressed inEscherichia coliand purified to homogeneity. HtsA binds 1 heme molecule per molecule of protein. HtsA was produced in vitro and localized to the bacterial cell surface. GAS up-regulated transcription ofhtsAin human blood compared with that in Todd-Hewitt broth supplemented with 0.2% yeast extract. The level of thehtsAtranscript dramatically increased under metal cation-restricted conditions compared with that under metal cation-replete conditions. The cation content, cell surface location, and gene transcription of HtsA were also compared with those of MtsA and Spy0385, the lipoprotein components of two other putative iron acquisition ABC transporters of GAS. Our results suggest that HtsABC is an ABC transporter that may participate in heme acquisition in GAS.
PneumocystisPneumonia Increases the Susceptibility of Mice to Sublethal Hyperoxia
Authors: Beck James M. , Preston Angela M. , Wilcoxen Steven E. , Morris Susan B. , White Eric S. , Paine Robert 
Published: September 2003

ABSTRACTPatients withPneumocystispneumonia often develop respiratory failure after entry into medical care, and one mechanism for this deterioration may be increased alveolar epithelial cell injury. In vitro, we previously demonstrated thatPneumocystisis not cytotoxic for alveolar epithelial cells. In vivo, however, infection withPneumocystiscould increase susceptibility to injury by stressors that, alone, would be sublethal. We examined transient exposure to hyperoxia as a prototypical stress that does cause mortality in normal mice. Mice were depleted of CD4+T cells and inoculated intratracheally withPneumocystis. Control mice were depleted of CD4+T cells but did not receivePneumocystis. After 4 weeks, mice were maintained in normoxia, were exposed to hyperoxia for 4 days, or were exposed to hyperoxia for 4 days followed by return to normoxia. CD4-depleted mice withPneumocystispneumonia demonstrated significant mortality after transient exposure to hyperoxia, while all uninfected control mice survived this stress. We determined that organism burdens were not different. However, infected mice exposed to hyperoxia and then returned to normoxia demonstrated significant increases in inflammatory cell accumulation and lung cell apoptosis. We conclude thatPneumocystispneumonia leads to increased mortality following a normally sublethal hyperoxic insult, accompanied by alveolar epithelial cell injury and increased pulmonary inflammation.
Parachlamydia acanthamoebaEnters and Multiplies within Human Macrophages and Induces Their Apoptosis
Authors: Greub Gilbert , Mege Jean-Louis , Raoult Didier 
Published: September 2003

ABSTRACTParachlamydia acanthamoebais an obligately intracellular bacterium that naturally infects free-living amoebae. It is a potential human pathogen and may survive in human macrophages. We studiedP. acanthamoebaentry into, and multiplication within, human monocyte-derived macrophages. After 8 h of incubation, 80% of macrophages were infected with a mean of 3.8P. acanthamoebaorganisms per cell. Electron microscopy demonstrated that parachlamydiae were in an intracellular vacuole. After infection with living organisms, the number of parachlamydiae per macrophage increased 4 times from day 0 to day 4, whereas heat-inactivated parachlamydiae were eliminated during the same period. Quantitative PCR confirmed thatP. acanthamoebareplicates within macrophages. Transcriptional activity ofP. acanthamoebawas detected by reverse transcription-PCR targeting the gene encoding ADP-ATP translocase (tlc).P. acanthamoebaexerted a cytopathic effect on macrophages. When macrophages were infected with living bacteria, their number decreased significantly from day 0 to day 4 due to apoptosis, as shown by annexin-V binding and electron microscopy. This study shows thatP. acanthamoebaenters and multiplies within human macrophages before inducing their apoptosis.
Host Resistance of CD18 Knockout Mice against Systemic Infection withListeria monocytogenes
Authors: Wu Huaizhu , Prince Joseph E. , Brayton Cory F. , Shah Chirayu , Zeve Daniel , Gregory Stephen H. , Smith C. Wayne , Ballantyne Christie M. 
Published: September 2003

ABSTRACTMice with targeted mutations of CD18, the common β2 subunit of CD11/CD18 integrins, have leukocytosis, impaired transendothelial neutrophil emigration, and reduced host defense toStreptococcus pneumoniae, a gram-positive extracellular bacterium. Previous studies using blocking monoclonal antibodies suggested roles for CD18 and CD11b in hepatic neutrophil recruitment and host innate response toListeria monocytogenes, a gram-positive intracellular bacterium. We induced systemic listeriosis in CD18 knockout (CD18-ko) and wild-type (WT) mice by tail vein injection withListeria. By 14 days postinjection (dpi), 8 of 10 WT mice died, compared with 2 of 10 CD18-ko mice (P< 0.01). Quantitative organ culture showed that numbers ofListeriaorganisms in livers and spleens were similar in both groups at 20 min postinfection. By 3, 5, and 7 dpi, however, numbers ofListeriaorganisms were significantly lower in livers and spleens of CD18-ko mice than in WT mice. Histopathology showed that followingListeriainfection, CD18-ko mice had milder inflammatory and necrotizing lesions in both spleens and livers than did WT mice. Cytokine assays indicated that baseline interleukin-1β and granulocyte colony-stimulating factor (G-CSF) levels were higher in CD18-ko mice than in WT mice and that CD18-ko splenocytes produced higher levels of interleukin-1β and G-CSF than WT splenocytes under the same amount ofListeriastimulation. These findings show that CD18 is not an absolute requirement for antilisterial innate immunity or hepatic neutrophil recruitment. We propose that the absence of CD18 in the mice results in the priming of innate immunity, as evidenced by elevated cytokine expression, and neutrophilic leukocytosis, which augments antilisterial defense.
Inhibition of Phagocytosis byHaemophilus ducreyiRequires Expression of the LspA1 and LspA2 Proteins
Authors: Vakevainen Merja , Greenberg Steven , Hansen Eric J. 
Published: September 2003

ABSTRACTHaemophilus ducreyipreviously has been shown to inhibit the phagocytosis of both secondary targets and itself by certain cells in vitro. Wild-typeH. ducreyistrain 35000HP contains two genes,lspA1andlspA2, whose encoded protein products are predicted to be 456 and 543 kDa, respectively. An isogenic mutant ofH. ducreyi35000HP with inactivatedlspA1andlspA2genes has been shown to exhibit substantially decreased virulence in the temperature-dependent rabbit model for chancroid. ThislspA1 lspA2mutant was tested for its ability to inhibit phagocytosis of immunoglobulin G-opsonized particles by differentiated HL-60 and U-937 cells and by J774A.1 cells. The wild-type strainH. ducreyi35000HP readily inhibited phagocytosis, whereas thelspA1 lspA2mutant was unable to inhibit phagocytosis. Similarly, the wild-type strain was resistant to phagocytosis, whereas thelspA1 lspA2mutant was readily engulfed by phagocytes. This inhibitory effect of wild-typeH. ducreyion phagocytic activity was primarily associated with live bacterial cells but could also be found, under certain conditions, in concentratedH. ducreyiculture supernatant fluids that lacked detectable outer membrane fragments. Both the wild-type strain and thelspA1 lspA2mutant attached to phagocytes at similar levels. These results indicate that the LspA1 and LspA2 proteins ofH. ducreyiare involved, directly or indirectly, in the antiphagocytic activity of this pathogen, and they provide a possible explanation for the greatly reduced virulence of thelspA1 lspA2mutant.
Different Strains ofMycobacterium tuberculosisCause Various Spectrums of Disease in the Rabbit Model of Tuberculosis
Authors: Manabe Yukari C. , Dannenberg Arthur M. , Tyagi Sandeep K. , Hatem Christine L. , Yoder Mark , Woolwine Samuel C. , Zook Bernard C. , Pitt M. Louise M. , Bishai William R. 
Published: September 2003

ABSTRACTThe rabbit model of tuberculosis has been used historically to differentiate betweenMycobacterium tuberculosisandMycobacterium bovisbased on their relative virulence in this animal host.M. tuberculosisinfection in market rabbits is cleared over time, whereas infection withM. bovisresults in chronic, progressive, cavitary disease leading to death. Because of the innate resistance of commercial rabbits toM. tuberculosis, 320 to 1,890 log-phase, actively growing inhaled bacilli were required to form one grossly visible pulmonary tubercle at 5 weeks. The range of inhaled doses required to make one tubercle allows us to determine the relative pathogenicities of different strains. Fewer inhaled organisms of theM. tuberculosisErdman strain were required than ofM. tuberculosisH37Rv to produce a visible lesion at 5 weeks. Furthermore, with the Erdman strain, only 7 of 15 rabbits had healed lesions at 16 to 18 weeks; among the other animals, two had chronic, progressive cavitary disease, a phenotype usually seen only withM. bovisinfection. Genotypic investigation of the Erdman strain with an H37Rv-based microarray identified gene differences in the RD6 region. Southern blot and PCR structural genetic analysis showed significant differences betweenM. tuberculosisstrains in this region. Correlation of the relative pathogenicity, including disease severity, in the rabbit model with the strain genotype may help identify stage-specificM. tuberculosisgenes important in human disease.