bluuebunny/crossref_metadata_2025_split huggingface dataset:
Identification of Novel Virulence Determinants inMycobacterium paratuberculosisby Screening a Library of Insertional Mutants
Authors: Shin Sung Jae , Wu Chia-wei , Steinberg Howard , Talaat Adel M. 
Published: June 2006

ABSTRACTJohne's disease, caused byMycobacterium paratuberculosisinfection, is a worldwide problem for the dairy industry and has a possible involvement in Crohn's disease in humans. To identify virulence determinants of this economically important pathogen, a library of 5,060 transposon mutants was constructed using Tn5367insertion mutagenesis, followed by large-scale sequencing to identify disrupted genes. In this report, 1,150 mutants were analyzed and 970 unique insertion sites were identified. Sequence analysis of the disrupted genes indicated that the insertion of Tn5367was more prevalent in genomic regions with G+C content (50.5 to 60.5%) lower than the average G+C content (69.3%) of the rest of the genome. Phenotypic screening of the library identified disruptions of genes involved in iron, tryptophan, or mycolic acid metabolic pathways that displayed unique growth characteristics. Bioinformatic analysis of disrupted genes identified a list of potential virulence determinants for further testing with animals. Mouse infection studies showed a significant decrease in tissue colonization by mutants with a disruption in thegcpE,pstA,kdpC,papA2,impA,umaA1, orfabG2_2gene. Attenuation phenotypes were tissue specific (e.g., for theumaA1mutant) as well as time specific (e.g., for theimpAmutant), suggesting that those genes may be involved in different virulence mechanisms. The identified potential virulence determinants represent novel functional classes that could be necessary for mycobacterial survival during infection and could provide suitable targets for vaccine and drug development against Johne's and Crohn's diseases.
CD8 T Cells Require Bcl-3 for Maximal Gamma Interferon Production upon Secondary Exposure to Antigen
Authors: Chilton Paula M. , Mitchell Thomas C. 
Published: June 2006

ABSTRACTAdjuvant-induced survival of T cells after antigen activation correlates with increased expression of Bcl-3. Bcl-3 is an NF-κB/IκB family member and has been implicated in transcriptional regulation in several cell types. We tested the ability of mice deficient in Bcl-3 (Bcl-3 KO) to exhibit T-cell adjuvant-induced survival after challenge with the superantigen staphylococcal enterotoxin B (SEB), using lipopolysaccharide (LPS) as a natural adjuvant. These studies showed that Bcl-3 is required for secondary gamma interferon (IFN-γ) production by CD8 T cells but not for adjuvant-induced survival effects. Specifically, wild-type and Bcl-3 KO mice exhibited comparable long-term increases in the Vβ8+T-cell populations, indicating no lack of survival in response to adjuvant stimulation in the Bcl-3 KO activated T cells. Ectopic expression of the Bcl-3-related molecules IκBα, IκBβ, and IκBε in SEB-activated T cells increased survival during in vitro culture in the absence of adjuvant, suggesting that these IκB molecules could exert a survival function in antigen-activated T cells in place of Bcl-3. However, Vβ8+CD8 T cells from SEB- plus LPS-treated Bcl-3 KO mice produced less IFN-γ upon in vitro restimulation than Vβ8+CD8 T cells from wild-type mice. Therefore, Bcl-3 plays a unique role in the regulation of IFN-γ production in this model system.
Invasion of Epithelial Cells and Proteolysis of Cellular Focal Adhesion Components by Distinct Types ofPorphyromonas gingivalisFimbriae
Authors: Nakagawa Ichiro , Inaba Hiroaki , Yamamura Taihei , Kato Takahiro , Kawai Shinji , Ooshima Takashi , Amano Atsuo 
Published: June 2006

ABSTRACTPorphyromonas gingivalisfimbriae are classified into six types (types I to V and Ib) based on thefimAgenes encoding FimA (a subunit of fimbriae), and they play a critical role in bacterial interactions with host tissues. In this study, we compared the efficiencies ofP. gingivalisstrains with distinct types of fimbriae for invasion of epithelial cells and for degradation of cellular focal adhesion components, paxillin, and focal adhesion kinase (FAK). Six representative strains with the different types of fimbriae were tested, andP. gingivaliswith type II fimbriae (type IIP. gingivalis) adhered to and invaded epithelial cells at significantly greater levels than the other strains. There were negligible differences in gingipain activities among the six strains; however, type IIP. gingivalisapparently degraded intracellular paxillin in association with a loss of phosphorylation 30 min after infection. Degradation was blocked with cytochalasin D or in mutants withfimAdisrupted. Paxillin was degraded by the mutant with Lys-gingipain disrupted, and this degradation was prevented by inhibition of Arg-gingipain activity byNα-p-tosyl-l-lysine chloromethyl ketone. FAK was also degraded by type IIP. gingivalis. Cellular focal adhesions with green fluorescent protein-paxillin macroaggregates were clearly destroyed, and this was associated with cellular morphological changes and microtubule disassembly. In an in vitro wound closure assay, type IIP. gingivalissignificantly inhibited cellular migration and proliferation compared to the cellular migration and proliferation observed with the other types. These results suggest that type IIP. gingivalisefficiently invades epithelial cells and degrades focal adhesion components with Arg-gingipain, which results in cellular impairment during wound healing and periodontal tissue regeneration.
Glycoprotein 340 in Normal Human Ocular Surface Tissues and Tear Film
Authors: Jumblatt Marcia M. , Imbert Yoannis , Young William W. , Foulks Gary N. , Steele Pamela S. , Demuth Donald R. 
Published: June 2006

ABSTRACT

The tear film is a complex mixture of secreted fluid, ions, proteins, glycoproteins, and lipids that lubricates and protects the ocular surface. Recently, several antimicrobial peptides have been described in the tear fluid. In this study, we describe the presence of the large secreted glycoprotein gp340 in the tear film. Western blot analysis showed that gp340 is abundant in secreted tears and in the lacrimal glands. Lesser amounts of gp340 were detected in the cornea and conjunctiva. Consistent with Western blot data, reverse transcription-PCR and real-time quantitative PCR showed that gp340 transcripts were abundant in lacrimal gland tissue and were also present in the cornea and conjunctiva. Immunohistochemistry localized gp340 to the acinar cells of the lacrimal gland and the deeper layers of the conjunctival epithelium. gp340 was not detected in conjunctival goblet cells. In the cornea, gp340 was present only in a peripheral band of basal epithelial cells, suggesting that gp340 may play a role in the cycle of corneal epithelial renewal. To determine if tear film gp340 may function as a bacterial agglutinin as it does in saliva, tears were incubated with streptococcal cells and the formation of bacterial aggregates was monitored. Addition of tears to late-exponential-phase
Streptococcus mutans
cells resulted in time- and dose-dependent aggregation of the bacteria. Furthermore, Western blot analysis confirmed the presence of cell-associated gp340 in isolated bacterial aggregates. The ocular pathogen
Staphylococcus aureus
, but not
Pseudomonas aeruginosa
, also aggregated when incubated with tears. These results suggest that gp340 is a normal component of the tear film and that the glycoprotein may function as a bacterial agglutinin.
Deletion of
znuA
Virulence Factor Attenuates
Brucella abortus
and Confers Protection against Wild-Type Challenge
Authors: Yang Xinghong , Becker Todd , Walters Nancy , Pascual David W. 
Published: June 2006

ABSTRACT

znuA
is known to be an important factor for survival and normal growth under low Zn
2+
concentrations for
Escherichia coli
,
Haemophilus
spp.,
Neisseria gonorrhoeae
, and
Pasteurella multocida
. We hypothesized that the
znuA
gene present in
Brucella melitensis
16 M would be similar to
znuA
in
B. abortus
and questioned whether it may also be an important factor for growth and virulence of
Brucella abortus
. Using the
B. melitensis
16 M genome sequence, primers were designed to construct a
B. abortus
deletion mutant. A
znuA
knockout mutation in
B. abortus
2308 (
ΔznuA
) was constructed and found to be lethal in low-Zn
2+
medium. When used to infect macrophages,
ΔznuA B. abortus
showed minimal growth. Further study with
ΔznuA B. abortus
showed that its virulence in BALB/c mice was attenuated, and most of the bacteria were cleared from the spleen within 8 weeks. Protection studies confirmed the
ΔznuA
mutant as a potential live vaccine, since protection against wild-type
B. abortus
2308 challenge was as effective as that obtained with the RB51 or S19 vaccine strain.
Identification of
Pseudomonas aeruginosa
Genes Involved in Virulence and Anaerobic Growth
Authors: Filiatrault Melanie J. , Picardo Kristin F. , Ngai Helen , Passador Luciano , Iglewski Barbara H. 
Published: June 2006

ABSTRACT

Pseudomonas aeruginosa
is a gram-negative, opportunistic pathogen and a significant cause of acute and chronic infections in patients with compromised host defenses. Evidence suggests that within infections
P. aeruginosa
encounters oxygen limitation and exists in microbial aggregates known as biofilms. However, there is little information that describes genes involved in anaerobic growth of
P. aeruginosa
and their association with virulence of this pathogen. To identify genes required for anaerobic growth, random transposon (Tn) mutagenesis was used to screen for mutants that demonstrated the inability to grow anaerobically using nitrate as a terminal electron acceptor. Of approximately 35,000 mutants screened, 57 mutants were found to exhibit no growth anaerobically using nitrate. Identification of the genes disrupted by the Tn revealed 24 distinct loci required for anaerobic growth on nitrate, including several genes not previously associated with anaerobic growth of
P. aeruginosa
. Several of these mutants were capable of growing anaerobically using nitrite and/or arginine, while five mutants were unable to grow anaerobically under any of the conditions tested. Three mutants were markedly attenuated in virulence in the lettuce model of
P. aeruginosa
infection. These studies have identified novel genes important for anaerobic growth and demonstrate that anaerobic metabolism influences virulence of
P. aeruginosa
.
The Type III Pseudomonal Exotoxin U Activates the c-Jun NH2-Terminal Kinase Pathway and Increases Human Epithelial Interleukin-8 Production
Authors: Cuzick Alayne , Stirling Fiona R. , Lindsay Susan L. , Evans Thomas J. 
Published: June 2006

ABSTRACTMicrobial interactions with host cell signaling pathways are key determinants of the host cell response to infection. Many toxins secreted by bacterial type III secretion systems either stimulate or inhibit the host inflammatory response. We investigated the role of type III secreted toxins of the lung pathogenPseudomonas aeruginosain the inflammatory response of human respiratory epithelial cells to infection. Using bacteria with specific gene deletions, we found that interleukin-8 production by these cells was almost entirely dependent on bacterial type III secretion of exotoxin U (ExoU), a phospholipase, although other bacterial factors are involved. ExoU activated the c-Jun NH2-terminal kinase pathway, stimulating the phosphorylation and activation of mitogen-activated kinase kinase 4, c-Jun NH2-terminal kinase, and c-Jun. This in turn increased levels of transcriptionally competent activator protein-1. Although this pathway was dependent on the lipase activity of ExoU, it was independent of cell death. Activation of mitogen-activated kinase signaling by ExoU in this fashion is a novel mechanism by which a bacterial product can initiate a host inflammatory response, and it may result in increased epithelial permeability and bacterial spread.
HbiF Regulates Type 1 Fimbriation Independently of FimB and FimE
Authors: Xie Yi , Yao Yufeng , Kolisnychenko Vitaliy , Teng Ching-Hao , Kim Kwang Sik 
Published: June 2006

ABSTRACT

Type 1 fimbriae have been suggested to play a role in the pathogenesis of extraintestinal
Escherichia coli
infection. Type 1 fimbriation in
E. coli
is phase variable and known to be dependent upon FimB and FimE, the two recombinases that invert the molecular switch
fimS
and control the expression of the downstream
fim
operon. Here we showed that HbiF, a novel site-specific recombinase, inverted
fimS
independently of FimB and FimE. HbiF-mediated
fimS
inversion appeared to be predominantly switching from “off” (termed OFF) to “on” (termed ON) orientation. This is different from the
fimS
inversion mediated by either FimB (bidirectional ON to OFF and OFF to ON) or FimE (unidirectional ON to OFF). Constitutive expression of the
hbiF
gene in
E. coli
resulted in a
fimS
-locked-ON phenotype, which resulted in the pathogenic
E. coli
K1 strain being incapable of inducing a high degree of bacteremia in neonatal rats. Discovery of HbiF-mediated OFF-to-ON
fimS
switching provides a new opportunity to develop a strategy for the prevention and therapy of extraintestinal
E. coli
infection including bacteremia and meningitis.
Differential Expression of
var
Gene Groups Is Associated with Morbidity Caused by
Plasmodium falciparum
Infection in Tanzanian Children
Authors: Rottmann Matthias , Lavstsen Thomas , Mugasa Joseph Paschal , Kaestli Mirjam , Jensen Anja T. R. , Müller Dania , Theander Thor , Beck Hans-Peter 
Published: June 2006

ABSTRACT

The
var
gene family of
Plasmodium falciparum
encodes the variant surface antigen
Plasmodium falciparum
erythrocyte membrane protein 1 (PfEMP1). PfEMP1 is considered an important pathogenicity factor in
P. falciparum
infection because it mediates cytoadherence to host cell endothelial receptors.
var
genes can be grouped into three major groups, A, B, and C, and the conserved
var
genes,
var1-4
, according to sequence similarities in coding and noncoding upstream regions. Using real-time quantitative PCR in a study conducted in Tanzania, the
var
transcript abundances of the different
var
gene groups were compared among patients with severe, uncomplicated, and asymptomatic malaria. Transcripts of
var
group A and B genes were more abundant in patients with severe malaria than in patients with uncomplicated malaria. In general, the transcript abundances of
var
group A and B genes were higher for children with clinical malaria than for children with asymptomatic infections. The
var
group C and
var1
-like transcript abundances were similar between the three sample groups. A transcript abundance pattern similar to that for
var
group A was observed for
var2csa
and
var3
-like genes. These results suggest that substantial and systematic differences in
var
gene expression exist between different clinical presentations.
Effects of Derivatives on Bank Risk
Authors: Yang Dong-Hoon , Song Inman , Yi Junesuh , Yoon Young-Hyeon 
Published: June 2006

This study investigates the empirical relationship between the use of derivatives by Korean banks and risk. In doing so, we employ two alternative measures of proxy for firm risk: systematic risk and ex ante earnings volatility. Contrary to the general concerns about the risk-increasing role of the use of derivative products, our results indicate that banks' derivatives are, on average, associated with two measures of risk in negative ways. The evidence is consistent with the conjectures that derivative use reduces noise related to exogenous factors and hence decreases firm risk. This suggests that equity market participants, on average, perceive derivative activities by banks as a sign of banks' efforts to reduce risk.
Acquisition and Elimination of Bacterial Vaginosis During Pregnancy: A Danish Population‐Based Study
Authors: Vogel Ida , Thorsen Poul , Jeune Bernard , Jacobsson Bo , Ebbesen Niels , Arpi Magnus , Bremmelgaard Annie , Møller Birger R. 
Published: June 2006

Objectives: the aim was to examine factors associated with acquisition and elimination of bacterial vaginosis in pregnancy. Methods: a group of 229 pregnant women were randomly selected from a population‐based prospective cohort study of 2927. They were examined at enrollment (mean gestational weeks 16w + 0d) and again in mid‐third trimester (mean gestational age 32w + 3d). Measures: BV (Amsel′s clinical criteria), microbiological cultures of the genital tract and questionnaire data. Results: BV prevalence decreased from 17% in early second trimester to 14% in mid‐third trimester due to a tenfold higher elimination rate (39%) than incidence rate (4%). Heavy smokers (>10/d) in early pregnancy were at increased risk (5.3 [1.1 − 25]) for the acquisition of BV during pregnancy, as were women receiving public benefits (4.8 [1.0 − 22]), having a vaginal pH above 4.5 (6.3 [1.4 − 29]) or vaginal anaerobe bacteria (18 [2.7 − 122]) at enrollment. A previous use of combined oral contraceptives was preventive for the acquisition of BV (0.2 [0.03 − 0.96]). Elimination of BV in pregnancy tended to be associated with a heavy growth of Lactobacillus
(3.2 [0.8 − 13]) at enrollment. Conclusions: acquisition of BV during pregnancy is rare and is associated with smoking, while the presence of anaerobe bacteria and a vaginal pH > 4.5 are interpreted as steps on a gradual change towards BV. In the same way heavy growth of Lactobacillus spp in early pregnancy may be an indicator of women on the way to eliminate BV.
Secession as a Human Right
Authors: Tideman Nicolaus 
Published: June 2006

AbstractIf people are to have rights to themselves, then they must have the right to affiliate in sovereign entities composed of people who mutually agree to affiliate with one another. This requires that any individual or group has a right to secede from any sovereign entity. The article develops the idea that a right of secession is natural when rights to territory and other gifts of nature are regarded as belonging equally to all persons, and all persons have rights to themselves. The article also argues that a world that recognizes a right of secession is feasible.
The metastasis-associated 67-kDa laminin receptor is involved in G-CSF–induced hematopoietic stem cell mobilization
Authors: Selleri Carmine , Ragno Pia , Ricci Patrizia , Visconte Valeria , Scarpato Nicola , Carriero Maria Vincenza , Rotoli Bruno , Rossi Guido , Montuori Nunzia 
Published: June 2006

AbstractThe 67-kDa laminin receptor (67LR) is a nonintegrin cell-surface receptor with high affinity for laminin, which plays a key role in tumor invasion and metastasis. We investigated the role of 67LR in granulocyte colony-stimulating factor (G-CSF)–induced mobilization of CD34+ hematopoietic stem cells (HSCs) from 35 healthy donors. G-CSF–mobilized HSCs, including CD34+/CD38– cells, showed increased 67LR expression as compared with unstimulated marrow HSCs; noteworthy, also, is the fact that the level of 67LR expression in G-CSF–mobilized HSCs correlated significantly with mobilization efficiency. During G-CSF–induced HSC mobilization, the expression of laminin receptors switched from α6 integrins, which mediated laminin-dependent adhesion of steady-state human marrow HSCs, to 67LR, responsible for G-CSF–mobilized HSC adhesion and migration toward laminin. In vitro G-CSF treatment, alone or combined with exposure to marrow-derived endothelial cells, induced 67LR up-regulation in marrow HSCs; moreover, anti-67LR antibodies significantly inhibited transendothelial migration of G-CSF–stimulated marrow HSCs. Finally, G-CSF–induced mobilization in mice was associated with 67LR up-regulation both in circulating and marrow CD34+ cells, and anti-67LR antibodies significantly reduced HSC mobilization, providing the first in vivo evidence for 67LR involvement in stem-cell egress from bone marrow after G-CSF administration. In conclusion, 67LR up-regulation in G-CSF–mobilized HSCs correlates with their successful mobilization and reflects its increase in marrow HSCs, which contributes to the egress from bone marrow by mediating laminin-dependent cell adhesion and transendothelial migration.
CCAAT/enhancer binding proteins alpha and epsilon cooperate with all-trans retinoic acid in therapy but differ in their antileukemic activities
Authors: Lee Young-Jin , Jones Letetia C. , Timchenko Nikolai A. , Perrotti Danilo , Tenen Daniel G. , Kogan Scott C. 
Published: June 2006

Abstract
CCAAT/enhancer binding proteins (C/EBPs) play critical roles in myelopoiesis. Dysregulation of these proteins likely contributes to the pathogenesis of myeloid disorders characterized by a block in granulopoiesis. In one such disease, acute promyelocytic leukemia (APL), a promyelocytic leukemia–retinoic acid receptor α (PML-RARα) fusion protein is expressed as a result of a t(15;17) chromosomal translocation. Treatment of PML-RARα leukemic cells with all-trans retinoic acid (ATRA) causes them to differentiate into mature neutrophils, an effect thought to be mediated by C/EBPs. In this study, we assess the potential for cooperativity between increased C/EBP activity and ATRA therapy. We demonstrate that although both C/EBPα and C/EBPϵ can significantly prolong survival in a mouse model of APL, they are not functionally equivalent in this capacity. We also show that forced expression of C/EBPα or C/EBPϵ in combination with ATRA treatment has a synergistic effect on survival of leukemic mice compared with either therapy alone.
Host B cells produce IL-10 following TBI and attenuate acute GVHD after allogeneic bone marrow transplantation
Authors: Rowe Vanessa , Banovic Tatjana , MacDonald Kelli P. , Kuns Rachel , Don Alistair L. , Morris Edward S. , Burman Angela C. , Bofinger Helen M. , Clouston Andrew D. , Hill Geoffrey R. 
Published: June 2006

AbstractHost antigen-presenting cells (APCs) are known to be critical for the induction of graft-versus-host disease (GVHD) after allogeneic bone marrow transplantation (BMT), but the relative contribution of specific APC subsets remains unclear. We have studied the role of host B cells in GVHD by using B-cell–deficient μMT mice as BMT recipients in a model of CD4-dependent GVHD to major histocompatibility complex antigens. We demonstrate that acute GVHD is initially augmented in μMT recipients relative to wild-type recipients (mortality: 85% vs 44%, P < .01), and this is the result of an increase in donor T-cell proliferation, expansion, and inflammatory cytokine production early after BMT. Recipient B cells were depleted 28-fold at the time of BMT by total body irradiation (TBI) administered 24 hours earlier, and we demonstrate that TBI rapidly induces sustained interleukin-10 (IL-10) generation from B cells but not dendritic cells (DCs) or other cellular populations within the spleen. Finally, recipient mice in which B cells are unable to produce IL-10 due to homologous gene deletion develop more severe acute GVHD than recipient mice in which B cells are wild type. Thus, the induction of IL-10 in host B cells during conditioning attenuates experimental acute GVHD.