bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mutagenesis of a Novel Gene in the
prcA-prtP
Protease Locus Affects Expression of
Treponema denticola
Membrane Complexes
Authors: Bian Xue-lin , Wang Hong-tao , Ning Yu , Lee Si Young , Fenno J. Christopher 
Published: January 2005

ABSTRACT

A novel gene was identified in the
Treponema denticola prcA-prtP
protease operon. Strains with mutations in either the
prcA-prtP
or the
msp
region showed altered expression of a product(s) of the other locus. Together, these results provide information on the assembly of outer membrane complexes involved in
T. denticola
interaction with host cells and tissue.
Characterization of an Extracellular Dipeptidase from
Streptococcus gordonii
FSS2
Authors: Goldstein J. M. , Kordula T. , Moon J. L. , Mayo J. A. , Travis J. 
Published: January 2005

ABSTRACT

PepV, a dipeptidase found in culture fluids of
Streptococcus gordonii
FSS2, was purified and characterized, and its gene was cloned. PepV is a monomeric metalloenzyme of approximately 55 kDa that preferentially degrades hydrophobic dipeptides. The gene encodes a polypeptide of 467 amino acids, with a theoretical molecular mass of 51,114 Da and a calculated pI of 4.8. The
S. gordonii
PepV gene is homologous to the PepV gene family from
Lactobacillus
and
Lactococcus
spp.
A Type IV Pilin, PilA, Contributes to Adherence ofBurkholderia pseudomalleiand Virulence In Vivo
Authors: Essex-Lopresti Angela E. , Boddey Justin A. , Thomas Richard , Smith Martin P. , Hartley M. Gill , Atkins Timothy , Brown Nat F. , Tsang Chuk Hai , Peak Ian R. A. , Hill Jim , Beacham Ifor R. , Titball Richard W. 
Published: January 2005

ABSTRACTTheBurkholderia pseudomalleiK96243 genome contains multiple type IV pilin-associated loci, including one encoding a putative pilus structural protein (pilA). ApilAdeletion mutant has reduced adherence to human epithelial cells and is less virulent in the nematode model of virulence and the murine model of melioidosis, suggesting a role for type IV pili inB. pseudomalleivirulence.
Oral Mucosal Endotoxin Tolerance Induction in Chronic Periodontitis
Authors: Muthukuru Manoj , Jotwani Ravi , Cutler Christopher W. 
Published: January 2005

ABSTRACTThe oral mucosa is exposed to a high density and diversity of gram-positive and gram-negative bacteria, but very little is known about how immune homeostasis is maintained in this environment, particularly in the inflammatory disease chronic periodontitis (CP). The cells of the innate immune response recognize bacterial structures via the Toll-like receptors (TLR). This activates intracellular signaling and transcription of proteins essential for the induction of an adaptive immune response; however, if unregulated, it can lead to destructive inflammatory responses. Using single-immunoenzyme labeling, we show that the human oral mucosa (gingiva) is infiltrated by large numbers of TLR2+and TLR4+cells and that their numbers increase significantly in CP, relative to health (P< 0.05, Student'sttest). We also show that the numbers of TLR2+but not TLR4+cells increase linearly with inflammation (r2= 0.33,P< 0.05). Double-immunofluorescence analysis confirms that TLR2 is coexpressed by monocytes (MC)/macrophages (mφ) in situ. Further analysis of gingival tissues by quantitative real-time PCR, however, indicates that despite a threefold increase in the expression of interleukin-1β (IL-1β) mRNA during CP, there is significant (30-fold) downregulation of TLR2 mRNA (P< 0.05, Student'sttest). Also showing similar trends are the levels of TLR4 (ninefold reduction), TLR5 (twofold reduction), and MD-2 (sevenfold reduction) mRNA in CP patients compared to healthy persons, while the level of CD14 was unchanged. In vitro studies with human MC indicate that MC respond to an initial stimulus of lipopolysaccharide (LPS) fromPorphyromonas gingivalis(PgLPS) orEscherichia coli(EcLPS) by upregulation of TLR2 and TLR4 mRNA and protein; moreover, IL-1β mRNA is induced and tumor necrosis factor alpha (TNF-α), IL-10, IL-6, and IL-8 proteins are secreted. However, restimulation of MC with either PgLPS or EcLPS downregulates TLR2 and TLR4 mRNA and protein and IL-1β mRNA and induces a ca. 10-fold reduction in TNF-α secretion, suggesting the induction of endotoxin tolerance by either LPS. Less susceptible to tolerance than TNF-α were IL-6, IL-10, and IL-8. These studies suggest that certain components of the innate oral mucosal immune response, most notably TLRs and inflammatory cytokines, may become tolerized during sustained exposure to bacterial structures such as LPS and that this may be one mechanism used in the oral mucosa to attempt to regulate local immune responses.
Bioluminescence Imaging of
Toxoplasma gondii
Infection in Living Mice Reveals Dramatic Differences between Strains
Authors: Saeij Jeroen P. J. , Boyle Jon P. , Grigg Michael E. , Arrizabalaga Gustavo , Boothroyd John C. 
Published: January 2005

ABSTRACT

We examined the in vivo growth, dissemination, and reactivation of strains of the protozoan parasite
Toxoplasma gondii
using a bioluminescence-based imaging system. Two
T. gondii
strains, one with a highly virulent disease phenotype in mice (S23) and the other with a 1,000-fold-lower virulence phenotype (S22), were engineered to stably express the light-emitting protein luciferase. One clone of each wild-type strain was isolated, and the two clones (S23-luc7 and S22-luc2) were found to express similar levels of luciferase. Mice were infected intraperitoneally with S23-luc7 (50 or 5 parasites) or S22-luc2 (500, 50, or 5 parasites), and the progress of the infections was examined noninvasively following injection of the substrate for luciferase,
d
-luciferin. In mice infected with 50 S23-luc7 parasites, the parasites grew exponentially within the peritoneal cavity (as measured by light emitted from luciferase-expressing parasites) during days 1 to 10 p.i., and this proliferation continued until there was severe disease. In mice infected with 500 S22-luc2 parasites, the parasites proliferated in a fashion similar to the S23-luc7 proliferation during days 1 to 6, but this was followed by a precipitous drop in the signal to levels below the limit of detection. Using this technique, we were also able to observe the process of reactivation of
T. gondii
in chronically infected mice. After treatment with dexamethasone, we detected reactivation of toxoplasmosis in mice infected with S23-luc7 and S22-luc2. During reactivation, growth of S23-luc7 was initially detected primarily in the head and neck area, while in S22-luc2-infected mice the parasites were detected primarily in the abdomen. This method has great potential for identifying important differences in the dissemination and growth of different
T. gondii
strains, especially strains with dramatically different disease outcomes.
Class I Major Histocompatibility Complex Presentation of Antigens That Escape from the Parasitophorous Vacuole ofToxoplasma gondii
Authors: Gubbels Marc-Jan , Striepen Boris , Shastri Nilabh , Turkoz Mustafa , Robey Ellen A. 
Published: January 2005

ABSTRACTThe intracellular parasiteToxoplasma gondii, the causative agent of toxoplasmosis, induces a protective CD8 T-cell response in its host; however, the mechanisms by whichT. gondiiproteins are presented by the class I major histocompatibility complex remain largely unexplored.T. gondiiresides within a specialized compartment, the parasitophorous vacuole, that sequesters the parasite and its secreted proteins from the host cell cytoplasm, suggesting that an alternative cross-priming pathway might be necessary for class I presentation ofT. gondiiantigens. Here we used a strain ofT. gondiiexpressing yellow fluorescent protein and a secreted version of the model antigen ovalbumin to investigate this question. We found that presentation of ovalbumin secreted by the parasite requires the peptide transporter TAP (transporter associated with antigen processing) and occurs primarily in actively infected cells rather than bystander cells. We also found that dendritic cells are a major target ofT. gondiiinfection in vivo and account for much of the antigen-presenting activity in the spleen. Finally, we obtained evidence that Cre protein secreted byT. gondiican mediate recombination in the nucleus of the host cell. Together, these results indicate thatToxoplasmaproteins can escape from the parasitophorous vacuole into the host cytoplasm and be presented by the endogenous class I pathway, leading to direct recognition of infected cells by CD8 T cells.
HtrA Stress Protein Is Involved in Intramacrophagic Replication of Adherent and Invasive
Escherichia coli
Strain LF82 Isolated from a Patient with Crohn's Disease
Authors: Bringer Marie-Agnès , Barnich Nicolas , Glasser Anne-Lise , Bardot Olivier , Darfeuille-Michaud Arlette 
Published: January 2005

ABSTRACT

Adherent and invasive
Escherichia coli
(AIEC) bacteria isolated from Crohn's disease patients are able to greatly replicate within macrophages without escaping from the phagosome and without inducing macrophage death. In the present study, evidence is provided that in AIEC strain LF82 the
htrA
gene encoding the stress protein HtrA is essential for intracellular replication within J774-A1 macrophages. Deletion of the
htrA
gene in strain LF82 induced increased sensitivity of the isogenic mutant to oxidative stress caused by hydrogen peroxide and a reduced rate of growth in an acid and nutrient-poor medium partly reproducing the microenvironment of the phagosome. In vitro experiments using an LF82
htrA
gene promoter fusion with the
lacZ
gene revealed a 38-fold activation of the promoter in AIEC LF82 intramacrophagic bacteria. The CpxRA two-component signaling pathway was not involved in this activation. In addition, the activation of the LF82
htrA
gene promoter was not observed in the nonpathogenic
E. coli
K-12 intramacrophagic bacteria, indicating that the AIEC LF82 genetic background is crucial for induction of
htrA
gene transcription during phagocytosis.
Contribution of the ATP-Dependent Protease ClpCP to the Autolysis and Virulence of
Streptococcus pneumoniae
Authors: Ibrahim Yasser Musa , Kerr Alison R. , Silva Nuno A. , Mitchell Tim J. 
Published: January 2005

ABSTRACT

The ATP-dependent caseinolytic proteases (Clp) are fundamental for stress tolerance and virulence in many pathogenic bacteria. The role of ClpC in the autolysis and virulence of
Streptococcus pneumoniae
is controversial. In this study, we tested the role of ClpC in a number of
S. pneumoniae
strains and found that the contribution of ClpC to autolysis is strain dependent. ClpC is required for the release of autolysin A and pneumolysin in serotype 2
S. pneumoniae
strain D39. In vivo, ClpC is required for the growth of the pneumococcus in the lungs and blood in a murine model of disease, but it does not affect the overall outcome of pneumococcal disease. We also report the requirement of ClpP for the growth at elevated temperature and virulence of serotype 4 strain TIGR4 and confirm its contribution to the thermotolerance, oxidative stress resistance, and virulence of D39.
Evaluation of the Role of the Bvg Intermediate Phase in
Bordetella pertussis
during Experimental Respiratory Infection
Authors: Vergara-Irigaray Nuria , Chávarri-Martínez Alberto , Rodríguez-Cuesta Juan , Miller Jeff F. , Cotter Peggy A. , Martínez de Tejada Guillermo 
Published: January 2005

ABSTRACT

The BvgAS system of
Bordetella pertussis
was traditionally considered to mediate a transition between two phenotypic phases (Bvg
+
and Bvg
−
) in response to environmental signals. We characterized a third state, the intermediate (Bvg
i
) phase, which can be induced by introducing a 1-bp substitution into
bvgS
(the
bvgS
-I1 mutation) or by growing
B. pertussis
under conditions intermediate between those leading to the Bvg
+
and Bvg
−
phases. Like
B. bronchiseptica
,
B. pertussis
displays in its Bvg
i
phase a characteristic colony morphology and hemolytic activity and expresses a Bvg
i
-phase-specific polypeptide called BipA, whose synthesis is regulated by
bvgAS
at the transcriptional level. Based on our results, we hypothesize that the Bvg
i
phase of
B. pertussis
may be involved in facilitating transmission between hosts. Thus, a
B. pertussis
mutant carrying the
bvgS
-I1 mutation (GMT1i) persisted at wild-type levels only in the upper murine respiratory tract. Interestingly, a
bipA
deletion derivative of GMT1i displayed a reduced ability to colonize the nasal cavity of mice compared with GMT1i. However, in experimental mixed infections GMT1i expressing the Bvg
i
phase could establish an initial colonization in the nose and trachea of mice as efficiently as GMT1, but the wild-type strain outcompeted GMT1i at a later time point at all sites of the respiratory tract, suggesting that the Bvg
i
phase does not serve as a phenotypic phase specialized in colonization. Finally, even though
B. pertussis
expresses in vitro the Bvg
i
phase at the human nasal temperature, anti-BipA antibodies were undetectable in a large collection of sera from pertussis patients.
Helicobacter pyloriInduces Transendothelial Migration of Activated Memory T Cells
Authors: Enarsson Karin , Brisslert Mikael , Backert Steffen , Quiding-Järbrink Marianne 
Published: January 2005

ABSTRACTHelicobacter pyloriinfection is associated with pronounced infiltration of granulocytes and lymphocytes into the gastric mucosa, resulting in active chronic gastritis that may develop into duodenal ulcer disease or gastric adenocarcinoma. Infiltrating T cells play a major role in the pathology of these diseases, but the signals involved in recruitment of T cells from blood toH. pylori-infected tissues are not well understood. We therefore examinedH. pylori-induced T-cell transendothelial migration (TEM). The Transwell system, employing a monolayer of human umbilical vein endothelial cells, was used as a model to study TEM.H. pyloriinduced a significant T-cell migration, compared to spontaneous migration. CD4+and CD8+T cells migrated to the same extent in response toH. pylori, whereas there was significantly larger transmigration of memory T cells compared to naive T cells. BothH. pyloriculture filtrate and urease induced migration, and the presence of theH. pylori cagpathogenicity island increased TEM. T-cell TEM was mediated by LFA-1-ICAM-1 interactions in accordance with an increased ICAM-1 expression on the endothelial cells after contact withH. pylori. Migrating T cells had increased expression of activation marker CD69 and chemokine receptors CXCR3, CCR4, and CCR9. Furthermore, T cells migrating in response toH. pylorisecreted Th1 but not Th2 cytokines upon stimulation. In conclusion, our data indicate that liveH. pyloriand its secreted products contribute to T-cell recruitment to the gastric mucosa and that the responding T cells have an activated memory Th1 phenotype.
Enhanced Killing ofCandida albicansby Human Macrophages Adherent to Type 1 Collagen Matrices via Induction of Phagolysosomal Fusion
Authors: Newman Simon L. , Bhugra Bindu , Holly Angela , Morris Randal E. 
Published: January 2005

ABSTRACTCandida albicans, a component of the normal flora of the alimentary tract and mucocutaneous membranes, is the leading cause of invasive fungal disease in premature infants, diabetics, and surgical patients and of oropharyngeal disease in AIDS patients. As little is known about the regulation of monocyte/macrophage anti-Candidaactivity, we sought to determine if fungicidal activity might be regulated by extracellular matrix proteins to which monocytes/macrophages are adherent in vivo. Compared to monocyte/macrophages that adhered to plastic, human monocytes and monocyte-derived macrophages that adhered to type 1 collagen matrices, but not to fibronectin, vitronectin, or laminin, demonstrated a significant increase in candidacidal activity. The enhancement of monocyte fungicidal activity was maintained over a 4-h period, whereas macrophage fungicidal activity was maximum at 1 h. Although adherence of monocytes and macrophages to collagen matrices concomitantly enhanced the production of superoxide anion, only the fungicidal activity of collagen-adherent monocytes was partially blocked by superoxide dismutase and catalase. Remarkably, we found that only 10% of the phagosomes inC. albicans-infected macrophages that adhered to plastic fused with lysosomes. In contrast, 80% of yeast-containing phagosomes of collagen-adherent macrophages fused with lysosomes. These data suggest that nonoxidative mechanisms are critical for human macrophage anti-Candidaactivity and thatC. albicanspathogenicity is mediated, in part, by its ability to inhibit phagolysosomal fusion in macrophages.
Rhizopus oryzae
Adheres to, Is Phagocytosed by, and Damages Endothelial Cells In Vitro
Authors: Ibrahim Ashraf S. , Spellberg Brad , Avanessian Valentina , Fu Yue , Edwards John E. 
Published: January 2005

ABSTRACT

Rhizopus oryzae
is the most common cause of zygomycosis, a life-threatening infection that usually occurs in immunocompromised patients. A characteristic hallmark of zygomycosis is angioinvasion by the fungus, resulting in thrombosis and subsequent tissue necrosis. Interactions between
R. oryzae
and vascular endothelial cells are therefore likely of central importance to the organism's pathogenetic strategy. We studied the ability of
R. oryzae
to adhere to and damage human umbilical vein endothelial cells (HUVECs) in vitro. We report that
R. oryzae
spores and germ tubes adhere to HUVECs, whereas only spores adhere to subendothelial matrix proteins. Additionally,
R. oryzae
damages endothelial cells. This endothelial cell damage requires direct contact and subsequent phagocytosis of the fungus. Surprisingly,
R. oryzae
viability was not required for damage, but phagocytosis was required for dead
R. oryzae
to cause damage. These results elucidate the nature of
R. oryzae
-endothelial cell interactions, which are likely central to the angioinvasion and tissue necrosis seen during zygomycotic infections. The fact that dead
R. oryzae
damage human endothelial cells may, in part, explain the lack of efficacy of fungicidal agents during clinical disease.
Closely Related Mycobacterial Strains Demonstrate Contrasting Levels of Efficacy as Antitumor Vaccines and Are Processed for Major Histocompatibility Complex Class I Presentation by Multiple Routes in Dendritic Cells
Authors: Cheadle Eleanor J. , O'Donnell Dearbhaile , Selby Peter J. , Jackson Andrew M. 
Published: January 2005

ABSTRACTMycobacteria expressing recombinant antigens are already being developed as vaccines against both infections and tumors. Little is known about how dendritic cells might process such antigens. Two different mycobacterial species, the fast-growingMycobacterium smegmatisand the slow-growingM. bovis M. bovisBCG, were engineered to express a model tumor antigen, the Kb-restricted dominant cytotoxic T-lymphocyte epitope OVA257-264. RecombinantM. bovisBCG but not recombinantM. smegmatisconferred protection to mice challenged with the B16-OVA tumor cell line. We went on to investigate whether the contrast in antitumor efficacy could be due to differences in how dendritic cells process antigen from the two mycobacterial strains for class I presentation. Both strains of mycobacteria caused phenotypic maturation of dendritic cells, but recombinantM. smegmatisinfection led to a greater degree of dendritic cell maturation than recombinantM. bovisBCG infection. Antigen from recombinantM. smegmatiswas processed and presented as OVA257-264on Kbmolecules by the dendritic cell line DC2.4 but not by bone marrow-derived dendritic cells (BMDC) or splenic dendritic cells. In contrast, antigen from recombinantM. bovisBCG was presented by all three dendritic cell types as long as the mycobacteria were viable. Such presentation was dependent on proteasome function and nascent major histocompatibility complex (MHC) class I molecules in DC2.4 cells but independent of the proteasome and transporter associated with antigen processings (TAP) in BMDC and splenic dendritic cells. These data demonstrate for the first time that antigen vectored by the slow-growingM. bovisBCG but not that vectored by fast-growing, readily destroyedM. smegmatisis processed and presented on MHC class I by in vitro-generated dendritic cells, which has implications for recombinant microbial vaccine development.
A High-Affinity Monoclonal Antibody to Anthrax Protective Antigen Passively Protects Rabbits before and after Aerosolized
Bacillus anthracis
Spore Challenge
Authors: Mohamed Nehal , Clagett Michelle , Li Juan , Jones Steven , Pincus Steven , D'Alia Giovanni , Nardone Linda , Babin Michael , Spitalny George , Casey Leslie 
Published: January 2005

ABSTRACT

We have developed a therapeutic for the treatment of anthrax using an affinity-enhanced monoclonal antibody (ETI-204) to protective antigen (PA), which is the central cell-binding component of the anthrax exotoxins. ETI-204 administered preexposure by a single intravenous injection of a dose of between 2.5 and 10 mg per animal significantly protected rabbits from a lethal aerosolized anthrax spore challenge (∼60 to 450 times the 50% lethal dose of
Bacillus anthracis
Ames). Against a similar challenge, ETI-204 administered intramuscularly at a 20-mg dose per animal completely protected rabbits from death (100% survival). In the postexposure setting, intravenous administration of ETI-204 provided protection 24 h (8 of 10) and 36 h (5 of 10) after spore challenge. Administration at 48 h postchallenge, when 3 of 10 animals had already succumbed to anthrax infection, resulted in the survival of 3 of 7 animals (43%) for the duration of the study (28 days). Importantly, surviving ETI-204-treated animals were free of bacteremia by day 10 and remained so until the end of the studies. Only 11 of 51 ETI-204-treated rabbits had positive lung cultures at the end of the studies. Also, rabbits that were protected from inhalational anthrax by administration of ETI-204 developed significant titers of PA-specific antibodies. Presently, the sole therapeutic regimen available to treat infection by inhalation of
B. anthracis
spores is a 60-day course of antibiotics that is effective only if administered prior to or shortly after exposure. Based upon results reported here, ETI-204 is an effective therapy for prevention and treatment of inhalational anthrax.
Chemotaxis Plays Multiple Roles during
Helicobacter pylori
Animal Infection
Authors: Terry Karianne , Williams Susan M. , Connolly Lynn , Ottemann Karen M. 
Published: January 2005

ABSTRACT

Helicobacter pylori
is a human gastric pathogen associated with gastric and duodenal ulcers as well as specific gastric cancers.
H. pylori
infects approximately 50% of the world's population, and infections can persist throughout the lifetime of the host. Motility and chemotaxis have been shown to be important in the infection process of
H. pylori
. We sought to address the specific roles of chemotaxis in infection of a mouse model system. We found that mutants lacking
cheW
,
cheA
, or
cheY
are all nonchemotactic and infect FVB/N mice with an attenuated phenotype after 2 weeks of infection. If infections proceeded for 6 months, however, this attenuation disappeared. Histological and culture analysis revealed that nonchemotactic mutants were found only in the corpus of the stomach, while the wild type occupied both the corpus and the antrum. Further analysis showed that nonchemotactic
H. pylori
isolates had an increased 50% infectious dose and were greatly outcompeted when coinfected with the wild type. If nonchemotactic mutants were allowed to establish an infection, subsequent infection with the wild type partially displaced the nonchemotactic mutants, indicating a role for chemotaxis in maintenance of infection. The data presented here support four roles for chemotaxis in
H. pylori
mouse infections: (i) establishing infection, (ii) achieving high-level infection, (iii) maintaining an infection when there are competing
H. pylori
present, and (iv) colonizing all regions of the stomach.