bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Response Regulator PhoP of
Yersinia pseudotuberculosis
Is Important for Replication in Macrophages and for Virulence
Authors: Grabenstein Jens P. , Marceau Michael , Pujol Céline , Simonet Michel , Bliska James B. 
Published: August 2004

ABSTRACT

Yersinia pestis
and
Yersinia pseudotuberculosis
are closely related facultative intracellular pathogens. The response regulator PhoP was previously shown to be important for
Y. pestis
survival in macrophages and for virulence in a murine bubonic plague infection assay. Here the importance of PhoP for
Y. pseudotuberculosis
pathogenesis was investigated.
Y. pseudotuberculosis phoP
mutants were unable to replicate in low-Mg
2+
medium or in macrophages.

phoP
+
Y. pseudotuberculosis

strains initiated replication in macrophages after a lag period of ∼5 h, as shown by fluorescence microscopy and viable count assays.
Y. pseudotuberculosis phoP
mutants died at a low rate in macrophages; there was no decrease in viability over the first 5 h of infection, and there was a 10-fold decrease in viability between 5 and 24 h of infection. Trafficking of phagosomes containing

phoP
+

or
phoP
mutant
Y. pseudotuberculosis
was studied by using immunofluorescence microscopy and cathepsin D as a marker for lysosomes. Phagosomes containing
phoP
mutant
Y. pseudotuberculosis
acquired cathepsin D at a higher rate than phagosomes containing

phoP
+

bacteria. However, the increased rate of marker acquisition for phagosomes containing mutant bacteria was only evident ∼5 h after infection, suggesting that
phoP
mutants are able to retard phagosome maturation during the lag phase of intracellular growth. The results obtained with a
Y. pestis phoP
mutant were similar to those described above, except that the rates of intracellular killing and trafficking to cathepsin D-positive vacuoles were significantly higher. A
Y. pseudotuberculosis phoP
mutant was 100-fold less virulent than the wild-type strain in a murine intestinal infection model, suggesting that survival and replication in macrophages are important for
Y. pseudotuberculosis
pathogenesis.
Cryptococcal Yeast Cells Invade the Central Nervous System via Transcellular Penetration of the Blood-Brain Barrier
Authors: Chang Yun C. , Stins Monique F. , McCaffery Michael J. , Miller Georgina F. , Pare Dan R. , Dam Tapen , Paul-Satyasee Maneesh , Kim Kwang Sik , Kwon-Chung Kyung J. 
Published: August 2004

ABSTRACT

Cryptococcal meningoencephalitis develops as a result of hematogenous dissemination of inhaled
Cryptococcus neoformans
from the lung to the brain. The mechanism(s) by which
C. neoformans
crosses the blood-brain barrier (BBB) is a key unresolved issue in cryptococcosis. We used both an in vivo mouse model and an in vitro model of the human BBB to investigate the cryptococcal association with and traversal of the BBB. Exposure of human brain microvascular endothelial cells (HBMEC) to
C. neoformans
triggered the formation of microvillus-like membrane protrusions within 15 to 30 min. Yeast cells of
C. neoformans
adhered to and were internalized by the HBMEC, and they crossed the HBMEC monolayers via a transcellular pathway without affecting the monolayer integrity. The histopathology of mouse brains obtained after intravenous injection of
C. neoformans
showed that the yeast cells either were associated with endothelial cells or escaped from the brain capillary vessels into the neuropil by 3 h.
C. neoformans
was found in the brain parenchyma away from the vessels by 22 h. Association of
C. neoformans
with the choroid plexus, however, was not detected during up to 10 days of observation. Our findings indicate that
C. neoformans
cells invade the central nervous system by transcellular crossing of the endothelium of the BBB.
Role of Antibiotics and Fungal Microbiota in Driving Pulmonary Allergic Responses
Authors: Noverr Mairi C. , Noggle Rachael M. , Toews Galen B. , Huffnagle Gary B. 
Published: August 2004

ABSTRACTOver the past four decades, there has been a significant increase in allergy and asthma in westernized countries, which correlates with alterations in fecal microbiota (microflora) and widespread use of antibiotics (the “hygiene hypothesis”). Antibiotics also lead to overgrowth of the yeastCandida albicans, which can secrete potent prostaglandin-like immune response modulators. We have developed a mouse model of antibiotic-induced microbiota disruption that includes stable increases in gastrointestinal (GI) enteric bacteria and GICandidalevels with no introduction of microbes into the lungs. Mice are treated for 5 days with cefoperazone in the drinking water, followed by a single oral gavage ofC. albicans. This results in alterations of GI bacterial populations and increased yeast numbers in the GI microbiota for at least 2 to 3 weeks and can drive the development of a CD4 T-cell-mediated allergic airway response to subsequent mold spore (Aspergillus fumigatus) exposure in immunocompetent mice without previous systemic antigen priming. The allergic response in the lungs is characterized by increased levels of eosinophils, mast cells, interleukin-5 (IL-5), IL-13, gamma interferon, immunoglobulin E, and mucus-secreting cells. In the absence of antibiotics, mice exposed toAspergillusspores do not develop an allergic response in the airways. This study provides the first experimental evidence to support a role for antibiotics and fungal microbiota in promoting the development of allergic airway disease. In addition, these studies also highlight the concept that events in distal mucosal sites such as the GI tract can play an important role in regulating immune responses in the lungs.
Mycoplasma fermentans
Binds to and Invades HeLa Cells: Involvement of Plasminogen and Urokinase
Authors: Yavlovich Amichai , Katzenell Avigail , Tarshis Mark , Higazi Abd A.-R. , Rottem Shlomo 
Published: August 2004

ABSTRACT

Adherence of
Mycoplasma fermentans
to HeLa cells followed saturation kinetics, required a divalent cation, and was enhanced by preincubation of the organism at 37°C for 1 h in a low-osmolarity solution. Proteolytic digestion, choline phosphate, or anti-choline phosphate antibodies partially inhibited the adherence, supporting the notion that
M. fermentans
utilizes at least two surface components for adhesion, a protease-sensitive surface protein and a phosphocholine-containing glycolipid. Plasminogen binding to
M. fermentans
greatly increased the maximal adherence of the organism to HeLa cells. Anti-plasminogen antibodies and free plasminogen inhibited this increase. These observations suggest that in the presence of plasminogen the organism adheres to novel sites on the HeLa cell surface, which are apparently plasminogen receptors. Plasminogen-bound
M. fermentans
was detected exclusively on the cell surface of the infected HeLa cells. Nevertheless, plasminogen binding in the presence of the urokinase-type plasminogen activator (uPA) promoted the invasion of HeLa cells by
M. fermentans
. The latter finding indicates that the invasiveness of
M. fermentans
does not result from binding plasminogen but from activation of the bound plasminogen to plasmin. Cholesterol depletion and sequestration with β-cyclodextrin and filipin, respectively, did not affect the capacity of
M. fermentans
to adhere, but invasion of HeLa cells by uPA-activated plasminogen-bound
M. fermentans
was impaired, suggesting that lipid rafts are implicated in
M. fermentans
entry.
Microarray Analysis Reveals Induction of Lipoprotein Genes in MucoidPseudomonas aeruginosa: Implications for Inflammation in Cystic Fibrosis
Authors: Firoved Aaron M. , Ornatowski Wojciech , Deretic Vojo 
Published: August 2004

ABSTRACTThe main cause of the high morbidity and mortality of cystic fibrosis (CF) is the progressive lung inflammation associated withPseudomonas aeruginosacolonization. During the course of chronic CF infections,P. aeruginosaundergoes a conversion to a mucoid phenotype. The emergence of mucoidP. aeruginosain CF is associated with increased inflammation, respiratory decline, and a poor prognosis. Here we show, by the use of microarray analysis, that uponP. aeruginosaconversion to mucoidy, there is a massive and preferential induction of genes encoding bacterial lipoproteins. Bacterial lipoproteins are potent agonists of Toll-like receptor 2 (TLR2) signaling. The expression of TLR2 in human respiratory epithelial cells was ascertained by Western blot analysis. Human respiratory epithelial cells responded in a TLR2-dependent manner to bacterial lipopeptides derived fromPseudomonaslipoproteins induced in mucoid strains. The TLR2 proinflammatory response was further augmented in CF cells. Thus, the excessive inflammation in CF is the result of a global induction in mucoidP. aeruginosaof lipoproteins that act as proinflammatory toxins (here termed lipotoxins) superimposed on the hyperexcitability of CF cells. Blocking the signaling cascade responding to bacterial lipotoxins may provide therapeutic benefits for CF patients.
Extracellular Signal-Regulated Protein Kinase Mediates Interleukin 17 (IL-17)-Induced IL-8 Secretion inHelicobacter pylori-Infected Human Gastric Epithelial Cells
Authors: Sebkova Ladislava , Pellicanò Antonia , Monteleone Giovanni , Grazioli Barbara , Guarnieri Giovanni , Imeneo Maria , Pallone Francesco , Luzza Francesco 
Published: August 2004

ABSTRACTHelicobacter pylori-induced mucosal inflammation results in high production of interleukin 17 (IL-17), a potent inducer of IL-8 in gastric epithelial cells. The aim of this study was to investigate signaling pathways by which IL-17 regulates IL-8 production in human gastric epithelial cells. Activation of mitogen-activated protein (MAP) kinases in both IL-17-stimulated MKN28 cells and epithelial cells isolated fromH. pylori-colonized gastric mucosa was assessed by Western blotting. In IL-17-stimulated MKN28 cells the activation of activatior protein 1 (AP-1), nuclear factor (NF)-IL-6, and NF-κB was also assessed by electrophoretic mobility shift assay. IL-8 production was evaluated by reverse transcription-PCR and enzyme-linked immunosorbent assay (ELISA) both for IL-17-stimulated MKN28 cells treated with specific MAP kinase inhibitors and gastric biopsy cultures treated with a neutralizing IL-17 antibody. Serum fromH. pylori-infected patients was tested for immunoglobulin G response to CagA by ELISA. Treatment of MKN28 cells with IL-17 caused activation of extracellular signal-regulated protein kinase 1/2 (ERK 1/2) but not other MAP kinases and had the downstream effects of AP-1 and NF-κB activation and IL-8 synthesis. Blocking ERK 1/2 activity inhibited AP-1-mediated, but not NF-κB-mediated, IL-8 induction. Enhanced activation of ERK 1/2 was seen in gastric epithelial cells isolated fromH. pylori-infected patients in comparison to uninfected controls, and this was associated with high IL-8. These effects were even more pronounced in patients seropositive for CagA than in seronegative ones. In gastric biopsy cultures, the addition of a neutralizing IL-17 antibody decreased ERK 1/2 activation, thus resulting in a significant inhibition of IL-8. InH. pylori-colonized gastric epithelial cells, IL-17-induced IL-8 synthesis is associated with and depends at least in part on the activation of ERK 1/2 MAP kinase.
Intermittent Preventive Sulfadoxine-Pyrimethamine Treatment of Primigravidae Reduces Levels of Plasma Immunoglobulin G, Which Protects against Pregnancy-Associated
Plasmodium falciparum
Malaria
Authors: Staalsoe Trine , Shulman Caroline E , Dorman Edgar K. , Kawuondo Ken , Marsh Kevin , Hviid Lars 
Published: August 2004

ABSTRACT

Pregnancy-associated malaria (PAM) is an important cause of maternal and neonatal suffering. It is caused by
Plasmodium falciparum
capable of inhabiting the placenta through expression of particular variant surface antigens (VSA) with affinity for proteoglycans such as chondroitin sulfate A. Protective immunity to PAM develops following exposure to parasites inhabiting the placenta, and primigravidae are therefore particularly susceptible to PAM. The adverse consequences of PAM in primigravidae are preventable by intermittent preventive treatment (IPTp), where women are given antimalarials at specified intervals during pregnancy, but this may interfere with acquisition of protective PAM immunity. We found that Kenyan primigravidae receiving sulfadoxine-pyrimethamine IPTp had significantly lower levels of immunoglobulin G (IgG) with specificity for the type of parasite-encoded VSA—called VSA
PAM
—that specifically mediate protection against PAM than did women receiving a placebo. VSA
PAM
-specific IgG levels depended on the number of IPTp doses received and were sufficiently low to be of clinical concern among multidose recipients. Our data suggest that IPTp should be extended to women of all parities, in line with current World Health Organization recommendations.
PspA Protects
Streptococcus pneumoniae
from Killing by Apolactoferrin, and Antibody to PspA Enhances Killing of Pneumococci by Apolactoferrin
Authors: Shaper Mirza , Hollingshead Susan K. , Benjamin William H. , Briles David E. 
Published: August 2004

ABSTRACT

Lactoferrin is an important component of innate immunity through its sequestration of iron, bactericidal activity, and immune modulatory activity. Apolactoferrin (ALF) is the iron-depleted form of lactoferrin and is bactericidal against pneumococci and several other species of bacteria. We observed that lactoferricin (LFN), an 11-amino-acid peptide from the N terminus of lactoferrin, is bactericidal for
Streptococcus pneumoniae
. Strains of
S. pneumoniae
varied in their susceptibility to ALF. Lactoferrin is bound to the pneumococcal surface by pneumococcal surface protein A (PspA). Using mutant PspA
−
pneumococci of four different strains, we observed that PspA offers significant protection against killing by ALF. Knockout mutations in genes for two other choline-binding proteins (PspC and PcpA) did not affect killing by ALF. PspA did not have to be attached to the bacterial surface to inhibit killing, because the soluble recombinant N-terminal half of PspA could prevent killing by both ALF and LFN. An 11-amino-acid fragment of PspA was also able to reduce the killing by LFN. Antibody to PspA enhanced killing by lactoferrin. These findings suggested that the binding of ALF to PspA probably blocks the active site(s) of ALF that is responsible for killing.
Porphyromonas gingivalis
Lipopolysaccharide Contains Multiple Lipid A Species That Functionally Interact with Both Toll-Like Receptors 2 and 4
Authors: Darveau Richard P. , Pham Thu-Thao T. , Lemley Kayde , Reife Robert A. , Bainbridge Brian W. , Coats Stephen R. , Howald William N. , Way Sing Sing , Hajjar Adeline M. 
Published: August 2004

ABSTRACT

The innate host response to lipopolysaccharide (LPS) obtained from
Porphyromonas gingivalis
is unusual in that different studies have reported that it can be an agonist for Toll-like receptor 2 (TLR2) as well as an antagonist or agonist for TLR4. In this report it is shown that
P. gingivalis
LPS is highly heterogeneous, containing more lipid A species than previously described. In addition, purification of LPS can preferentially fractionate these lipid A species. It is shown that an LPS preparation enriched for lipid A species at
m/z
1,435 and 1,450 activates human and mouse TLR2, TLR2 plus TLR1, and TLR4 in transiently transfected HEK 293 cells coexpressing membrane-associated CD14. The HEK cell experiments further demonstrated that cofactor MD-2 was required for functional engagement of TLR4 but not of TLR2 nor TLR2 plus TLR1. In addition, serum-soluble CD14 effectively transferred
P. gingivalis
LPS to TLR2 plus TLR1, but poorly to TLR4. Importantly, bone marrow cells obtained from TLR2
−/−
and TLR4
−/−
mice also responded to
P. gingivalis
LPS in a manor consistent with the HEK results, demonstrating that
P. gingivalis
LPS can utilize both TLR2 and TLR4. No response was observed from bone marrow cells obtained from TLR2 and TLR4 double-knockout mice, demonstrating that
P. gingivalis
LPS activation occurred exclusively through either TLR2 or TLR4. Although the biological significance of the different lipid A species found in
P. gingivalis
LPS preparations is not currently understood, it is proposed that the presence of multiple lipid A species contributes to cell activation through both TLR2 and TLR4.
Cooperative Interactions between Flagellin and SopE2 in the Epithelial Interleukin-8 Response toSalmonella entericaSerovar Typhimurium Infection
Authors: Huang Fu-Chen , Werne Adam , Li Qian , Galyov Edouard E. , Walker W. Allan , Cherayil Bobby J. 
Published: August 2004

ABSTRACTFlagellin is an important stimulus for epithelial interleukin-8 (IL-8) secretion because of its ability to activate Toll-like receptor 5 (TLR5). SopE2, aSalmonellaguanine nucleotide exchange factor (GEF), is also involved in intestinal inflammation. To clarify the proinflammatory mechanisms of these proteins, we examined their effects on IL-8 secretion and intracellular signaling in T84 epithelial cells. ASalmonellastrain lacking SopE2 (and its homolog SopE) induced lower levels of IL-8 than the wild type and exhibited reduced activation of mitogen-activated protein kinases (MAPKs). Overexpression of wild-type SopE2 in this strain restored MAPK activation and augmented IL-8 production, whereas a mutant lacking GEF activity failed to increase IL-8 expression. Additional effects on signaling were demonstrated in transient transfection experiments, in which SopE2 enhanced the ability of TRAF6, a signal transducer downstream of TLR5, to activate the NF-κB transcription factor in 293 cells. Flagellin was also found to be required for IL-8 induction in T84 cells. In its absence, the ability of SopE2 overexpression to increase IL-8 secretion was impaired. Part of this impairment was related to the decreased motility of the flagellin-deficient strain, but lack of flagellin also affected translocation of SopE2 into the infected cells. Our results indicate that flagellin and SopE2 interact functionally at multiple levels to increase IL-8 secretion by epithelial cells—flagellin facilitating the translocation of SopE2, and SopE2 enhancing signaling pathways activated by flagellin. These observations offer a mechanistic explanation for the involvement of these proteins in the pathogenesis ofSalmonella-induced gastroenteritis.
Temporal Analysis of the Antigenic Composition of
Borrelia burgdorferi
during Infection in Rabbit Skin
Authors: Crother Timothy R. , Champion Cheryl I. , Whitelegge Julian P. , Aguilera Rodrigo , Wu Xiao-Yang , Blanco David R. , Miller James N. , Lovett Michael A. 
Published: August 2004

ABSTRACT

The numbers of host-adapted
Borrelia burgdorferi
(HAB) organisms in rabbit skin were assessed by real-time PCR over the first 3 weeks of infection. Maximal numbers were found at day 11, while spirochete numbers decreased by more than 30-fold by day 21. The antigenic composition of HAB in skin biopsy samples was determined by use of a procedure termed hydrophobic antigen tissue Triton extraction. Immune sera from rabbits, sera from chronically infected mice, and monospecific antiserum to the antigenic variation protein, VlsE, were used to probe parallel two-dimensional immunoblots representing each time point. Individual proteins were identified using either specific antisera or by matching protein spots to mass spectrometry-identified protein spots from in vitro-cultivated
Borrelia
. There were significant changes in the relative expression of a variety of known and previously unrecognized HAB antigens during the 21-day period. OspC and the outer membrane proteins OspA and OspB were prominent at the earliest time point, day 5, when the antigenic variation protein VlsE was barely detected. OspA and OspB were not detected after day 5. OspC was not detected after day 9. VlsE was the most prominent antigen from day 7 through day 21. BmpA, ErpN, ErpP, LA7, OppA-2, DbpA, and an unidentified 15-kDa protein were also detected from day 7 through day 21. Immunoblot analysis using monospecific anti-VlsE revealed the presence of prominent distinct VlsE lower forms in HAB at days 9, 11, and 14; however, these lower forms were no longer detected at day 21. This marked diminution in VlsE lower forms paralleled the clearance of the spirochete from skin.
Impaired Host Defense against
Sporothrix schenckii
in Mice with Chronic Granulomatous Disease
Authors: Kajiwara Hideko , Saito Mitsumasa , Ohga Shouichi , Uenotsuchi Takeshi , Yoshida Shin-ichi 
Published: August 2004

ABSTRACT

We compared the immune defense of mice with chronic granulomatous disease (CGD mice) with that of wild-type C57BL/6 mice for their response to
Sporothrix schenckii
. A subcutaneous injection of 5 × 10
4
CFU
S. schenckii
strain IFM41598 into CGD mice resulted in systemic infection and death within 84 days. In contrast, injected C57BL/6 mice did not develop systemic infection and were able to survive through 100 days of observation. Differences in host resistance were analyzed in vitro. Neutrophils and macrophages obtained from CGD mice were found to allow greater growth of this organism than did those obtained from C57BL/6 mice. Moreover, macrophages obtained from immunized CGD mice were able to simply inhibit the growth of this fungus whereas macrophages obtained from immunized C57BL/6 mice killed the fungus within 48 h after phagocytosis. These results suggest that (i) the lack of NADPH oxidase function is a risk factor for lethal
S. schenckii
infection and (ii) superoxide anion and its reactive oxidative metabolites produced by neutrophils and macrophages are involved in fungistatic and fungicidal activities.
Molecular Evolutionary Relationships of Enteroinvasive
Escherichia coli
and
Shigella
spp
Authors: Lan Ruiting , Alles M. Chehani , Donohoe Kathy , Martinez Marina B. , Reeves Peter R. 
Published: August 2004

ABSTRACT

Enteroinvasive
Escherichia coli
(EIEC), a distinctive pathogenic form of
E. coli
causing dysentery, is similar in many properties to bacteria placed in the four species of
Shigella. Shigella
has been separated as a genus but in fact comprises several clones of
E. coli
. The evolutionary relationships of 32 EIEC strains of 12 serotypes have been determined by sequencing of four housekeeping genes and two plasmid genes which were used previously to determine the relationships of
Shigella
strains. The EIEC strains were grouped in four clusters with one outlier strain, indicating independent derivation of EIEC several times. Three of the four clusters contain more than one O antigen type. One EIEC strain (an O112ac:H− strain) was found in
Shigella
cluster 3 but is not identical to the
Shigella
cluster 3 D2 and B15 strains with the same O antigen. Two forms of the virulence plasmid pINV have been identified in
Shigella
strains by using the sequences of
ipgD
and
mxiA
genes, and all but two of our EIEC strains have pINV A. The EIEC strains were grouped in two subclusters with a very low level of variation, generally not intermingled with
Shigella
pINV A strains. The EIEC clusters based on housekeeping genes were reflected in the plasmid gene sequences, with some exceptions. Two strains were found in the pINV B form by using the
ipgD
sequence, with one strain having an
mxiA
sequence similar to the divergent sequence of D1. Clearly, EIEC and
Shigella
spp. form a pathovar of
E. coli
.