bluuebunny/crossref_metadata_2025_split huggingface dataset:
OspF and OspC1 AreShigella flexneriType III Secretion System Effectors That Are Required for Postinvasion Aspects of Virulence
Authors: Zurawski Daniel V. , Mitsuhata Chieko , Mumy Karen L. , McCormick Beth A. , Maurelli Anthony T. 
Published: September 2006

ABSTRACTShigella flexneriis the causative agent of dysentery, and its pathogenesis is mediated by a type III secretion system (T3SS).S. flexnerisecretes effector proteins into the eukaryotic cell via the T3SS, and these proteins usurp host cellular functions to the benefit of the bacteria. OspF and OspC1 are known to be secreted byS. flexneri, but their functions are unknown. We transformedS. flexneriwith a plasmid that expresses a two-hemagglutinin tag (2HA) in frame with OspF or OspC1 and verified that these proteins are secreted in a T3SS-dependent manner. Immunofluorescence of HeLa cells infected withS. flexneriexpressing OspF-2HA or OspC1-2HA revealed that both proteins localize in the nucleus and cytoplasm of host cells. To elucidate the function of these T3SS effectors, we constructed ΔospFand ΔospC1deletion mutants by allelic exchange. We found that ΔospFand ΔospC1mutants invade host cells and form plaques in confluent monolayers similar to wild-typeS. flexneri. However, in the polymorphonuclear (PMN) cell migration assay, a decrease in neutrophil migration was observed for both mutants in comparison to the migration of wild-type bacteria. Moreover, infection of polarized T84 intestinal cells infected with ΔospFand ΔospC1mutants resulted in decreased phosphorylation of extracellular signal-regulated kinase 1/2 in comparison to that of T84 cells infected with wild-typeS. flexneri. To date, these are the first examples of T3SS effectors implicated in mitogen-activated protein kinase kinase/extracellular signal-regulated kinase pathway activation. Ultimately, OspF and OspC1 are essential for PMN transepithelial migration, a phenotype associated with increased inflammation and bacterial access to the submucosa, which are fundamental aspects ofS. flexneripathogenesis.
Control ofBorrelia burgdorferi-Specific CD4+-T-Cell Effector Function by Interleukin-12- and T-Cell Receptor-Induced p38 Mitogen-Activated Protein Kinase Activity
Authors: Hedrick Michael N. , Olson Chris M. , Conze Dietrich B. , Bates Tonya C. , Rincón Mercedes , Anguita Juan 
Published: September 2006

ABSTRACTInfection withBorrelia burgdorferi, the causative agent of Lyme disease, results in a Th1 response and proinflammatory cytokine production. Mice deficient for MKK3, an upstream activator of p38 mitogen-activated protein (MAP) kinase, develop a lower Th1 response and exhibit an impaired ability to produce proinflammatory cytokines upon infection with the spirochete. We investigated the contribution of p38 MAP kinase activity in gamma interferon (IFN-γ) production in CD4+T cells in response to specific antigen through T-cell receptor (TCR)- and interleukin-12 (IL-12)-mediated signals. The specific inhibition of p38 MAP kinase in T cells and the administration of a pharmacological inhibitor of the kinase during the course of infection with the spirochete resulted in reduced levels of IFN-γ in the sera of infected mice. Our results also demonstrate that although p38 MAP kinase activity is not required for the differentiation ofB. burgdorferi-specific CD4+T cells, the production of IFN-γ by Th1 effector cells is regulated by the kinase. Both TCR engagement and IL-12 induced the production of the Th1 cytokine through the activation of the p38 MAP kinase pathway. Thus, the inhibition of this pathway in vitro resulted in decreased levels of IFN-γ during restimulation ofB. burgdorferi-specific T cells in response to anti-CD3 and IL-12 stimulation. These results clarify the specific contribution of the p38 MAP kinase in the overall immune response to the spirochete and its role in the effector function ofB. burgdorferi-specific T cells.
Trichomonas vaginalisLipophosphoglycan Triggers a Selective Upregulation of Cytokines by Human Female Reproductive Tract Epithelial Cells
Authors: Fichorova Raina N. , Trifonova Radiana T. , Gilbert Robert O. , Costello Catherine E. , Hayes Gary R. , Lucas John J. , Singh Bibhuti N. 
Published: September 2006

ABSTRACTTrichomonas vaginalisis one of the most common nonviral sexually transmitted human infections and, worldwide, has been linked to increased incidence of human immunodeficiency virus type 1 transmission, preterm delivery, low birth weight, cervical cancer, and vaginitis. The molecular pathways that are important in initiating host inflammatory and immune responses toT. vaginalisare poorly understood. Here we report interactions of human cervicovaginal epithelial cells with the most abundant cell surface glycoconjugate of the parasite, theT. vaginalislipophosphoglycan (LPG). Purified LPG mediated the adhesion of parasites to human vaginal epithelial cells in a dose-dependent manner. Furthermore,T. vaginalisLPG (but not LPG fromTritrichomonas foetus, the causative agent of bovine trichomoniasis) induced a selective upregulation of chemotactic cytokines by human endocervical, ectocervical, and vaginal epithelial cells, which do not express Toll-like receptor 4/MD2. TheT. vaginalisLPG triggered interleukin 8 (IL-8), which promotes the adhesion and transmigration of neutrophils across the endothelium, and macrophage inflammatory protein 3α, which is a chemoattractant for immune cells and is essential for dendritic cell maturation. These effects were dose dependent and sustained in the absence of cytotoxicity and IL-1β release and utilized, at least in part, a signaling pathway independent from the Toll-like/IL-1 receptor adaptor protein MyD88.
The Transcriptional Regulator RovS Controls the Attachment of
Streptococcus agalactiae
to Human Epithelial Cells and the Expression of Virulence Genes
Authors: Samen Ulrike M. , Eikmanns Bernhard J. , Reinscheid Dieter J. 
Published: September 2006

ABSTRACT

Streptococcus agalactiae
is part of the normal flora of the human gastrointestinal tract and also the leading cause of bacterial infections in human newborns and immunocompromised adults. The colonization and infection of different regions within the human host require a regulatory network in
S. agalactiae
that senses environmental stimuli and controls the formation of specific virulence factors. In the present study, we characterized an Rgg-like transcriptional regulator, designated RovS (
r
egulator
o
f
v
irulence in
Streptococcus agalactiae
). Deletion of the
rovS
gene in the genome of
S. agalactiae
resulted in strain 6313 Δ
rovS
, which exhibited an increased attachment to immobilized fibrinogen and a significant increase in adherence to the eukaryotic lung epithelial cell line A549. Quantification of expression levels of known and putative
S. agalactiae
virulence genes by real-time PCR revealed that RovS influences the expression of
fbsA
, gbs0230,
sodA
,
rogB
, and the
cyl
operon. The altered gene expression in mutant 6313 Δ
rovS
was restored by plasmid-mediated expression of
rovS
, confirming the RovS deficiency as the cause for the observed changes in virulence gene expression in
S. agalactiae
. DNA electrophoretic mobility shift assays showed that RovS specifically binds to the promoter regions of
fbsA
, gbs0230,
sodA
, and the
cyl
operon, indicating that RovS directly regulates their expression. Deletion and mutation studies in the promoter region of
fbsA
, encoding the main fibrinogen receptor in
S. agalactiae
, identified a RovS DNA motif. Similar motifs were also found in the promoter regions of gbs0230,
sodA
, and the
cyl
operon, and alignments allowed us to propose a consensus sequence for the DNA-binding site of RovS.
Acute Systemic Immune Activation following Conjunctival Exposure to Staphylococcal Enterotoxin B
Authors: Rajagopalan Govindarajan , Smart Michele K. , Patel Robin , David Chella S. 
Published: September 2006

ABSTRACT

Conjunctival exposure to the
Staphylococcus aureus
superantigen staphylococcal enterotoxin B (SEB) may occur accidentally, as a result of bioterrorism, or during colonization or infection of the external eye. Using human leukocyte antigen class II transgenic mice, we show for the first time that conjunctival exposure to SEB can cause robust systemic immune activation.
Prophylaxis and Therapy of Inhalational Anthrax by a Novel Monoclonal Antibody to Protective Antigen That Mimics Vaccine-Induced Immunity
Authors: Vitale Laura , Blanset Diann , Lowy Israel , O'Neill Thomas , Goldstein Joel , Little Stephen F. , Andrews Gerard P. , Dorough Gary , Taylor Ronald K. , Keler Tibor 
Published: September 2006

ABSTRACT
The neutralizing antibody response to the protective antigen (PA) component of anthrax toxin elicited by approved anthrax vaccines is an accepted correlate for vaccine-mediated protection against anthrax. We reasoned that a human anti-PA monoclonal antibody (MAb) selected on the basis of superior toxin neutralization activity might provide potent protection against anthrax. The fully human MAb (also referred to as MDX-1303 or Valortim) was chosen from a large panel of anti-PA human MAbs generated using transgenic mice immunized with recombinant PA solely on the basis of in vitro anthrax toxin neutralization. This MAb was effective in prophylactic and postsymptomatic treatment of rabbits exposed to aerosolized anthrax spores, and a single intramuscular injection of 1 mg/kg of body weight fully protected cynomolgus monkeys challenged with aerosolized anthrax spores. Importantly, MAb 1303 defines a novel neutralizing epitope that requires Fc receptor engagement for maximal activity. F(ab′)2 fragments of MAb 1303, which retain equivalent affinity for PA, are 10- to 100-fold less potent in neutralizing anthrax toxin in vitro. Addition of Fc receptor-blocking antibodies also greatly reduced the activity of MAb 1303. Moreover, we found that the neutralizing activity of mouse, rabbit, and human antisera elicited by PA vaccines was effectively abrogated by blocking Fc receptors. Selection of an anti-PA MAb by using a functional assay that is a surrogate for protection has resulted in the identification of a fully human MAb with potent activity in vivo and uncovered a previously unrecognized mechanism of antibody-mediated toxin neutralization that is important for currently used anthrax vaccines.
Genome-Wide Expression Analysis of
Burkholderia pseudomallei
Infection ina Hamster Model of Acute Melioidosis
Authors: Tuanyok Apichai , Tom Marina , Dunbar John , Woods Donald E. 
Published: September 2006

ABSTRACT

Burkholderia pseudomallei
is the causative agent of melioidosis and represents
a potential bioterrorism threat. In the current studies we have examined gene expression in
B. pseudomallei
in an animal model of acute melioidosis using whole-genome microarrays. Gene expression
profiles were generated by comparing transcriptional levels of
B. pseudomallei
-expressed genes in infected hamster organs including liver, lung, and spleen following intraperitoneal and intranasal routes
of infection to those from bacteria grown in vitro. Differentially expressed genes were similar in infected livers irrespective of the route of infection. Reduced expression of a number of housekeeping genes suggested a lower bacterial growth rate during infection. Energy production during growth in vivo involved specific biochemical pathways such as isomerization of 3-phosphoglycerate, catabolism of
d
-glucosamine and inositol, and biosynthesis of particular amino acids. In addition, the induction of genes known to be involved in oxidative phosphorylation including ubiquinol oxidase, ferredoxin oxidoreductase, and formate dehydrogenase enzymes suggested the use of alternative pathways for energy production, while the expression of genes coding for ATP-synthase and NADH-dehydrogenase enzymes was reduced. Our studies have identified differentially expressed genes which include potential virulence genes such as those for a putative phospholipase C and a putative two-component regulatory system, and they have also provided a better understanding of bacterial metabolism in response to the host environment during acute melioidosis.
Porphyromonas gingivalisFimbriae Proactively Modulate β2Integrin Adhesive Activity and Promote Binding to and Internalization by Macrophages
Authors: Hajishengallis George , Wang Min , Harokopakis Evlambia , Triantafilou Martha , Triantafilou Kathy 
Published: September 2006

ABSTRACTIn monocytes, the fimbriae of the oral pathogenPorphyromonas gingivalisactivate cross talk signaling from Toll-like receptor 2 (TLR2) to the β2integrin CD11b/CD18, leading to the induction of the high-affinity state of the latter receptor. CD14 plays an important role in this “inside-out” proadhesive pathway by binding fimbriae and facilitating the activation of TLR2 and phosphatidylinositol 3-kinase signaling. In its high-affinity state, CD11b/CD18 mediates monocyte adhesion to endothelial cells and transmigration to sites of infection. We have now shown thatP. gingivalisfimbriae function as both an activator and a ligand of CD11b/CD18; thus, fimbriae proactively promote their own binding to monocytes. Indeed, treatments that interfered with fimbria-induced activation of CD11b/CD18 (i.e., blockade of CD14, TLR2, or phosphatidylinositol 3-kinase signaling) also suppressed the cell binding activity of fimbriae, which was largely inducible and CD11b/CD18 dependent. Development of a recombinant inside-out signaling system in Chinese hamster ovary cells confirmed the ability of fimbriae to activate CD14/TLR2 signaling and induce their own CD11b/CD18-dependent binding. Induction of this proadhesive pathway byP. gingivalisfimbriae appeared to take place in lipid rafts. Indeed, methyl-β-cyclodextrin, a cholesterol-sequestering agent that disrupts lipid raft organization, was found to inhibit the fimbria-induced assembly of CD14/TLR2 signaling complexes and the activation of the high-affinity state of CD11b/CD18. Experiments using macrophages from mice deficient in various pattern recognition receptors indicated that the receptors involved in the inside-out proadhesive pathway (CD14, TLR2, and CD11b/CD18) are important for mediatingP. gingivalisinternalization within macrophages. It therefore appears thatP. gingivalisproactively modulates β2integrin adhesive activity for intracellular uptake.
Effects of ConcomitantSchistosoma haematobiumInfection on the Serum Cytokine Levels Elicited by AcutePlasmodium falciparumMalaria Infection in Malian Children
Authors: Lyke Kirsten E. , Dabo Abdoulaye , Sangare Lansana , Arama Charles , Daou Modibo , Diarra Issa , Plowe Christopher V. , Doumbo Ogobara K. , Sztein Marcelo B. 
Published: September 2006

ABSTRACTPolyparasitism is common in the developing world, and interactions that alter disease severity may occur. We previously demonstrated that infection withSchistosoma hematobiumwas associated with protection againstPlasmodium falciparuminfection in children who were 4 to 8 years old. In this study, we determined whether underlying helminth infections affected the cytokine responses to acute falciparum malaria. A total of 338 schistosomiasis-positive [Sch(+)] children who were 4 to 14 years old were matched by age, residence, and sex with 338 schistosomiasis-negative [Sch(−)] children and monitored for a malaria transmission season (25 weeks). Serologic cytokine levels were measured at the time of the first clinical malaria episode and in children who did not contract malaria. Elevated background levels of interleukin-6 (IL-6) (37.1 pg/ml versus 10.9 pg/ml [P= 0.04]), IL-4 (27.7 pg/ml versus 6.9 pg/ml [P= 0.02]), IL-10 (18.2 pg/ml versus 7.2 pg/ml [P< 0.001]), and gamma interferon (18.2 pg/ml versus 4.7 pg/ml [P= 0.006]) were noted in Sch(+) children compared to Sch(−) children without malaria. IL-6 and IL-10 levels were elevated in association with acute malaria, but the levels appeared to be blunted in Sch(+) children compared to Sch(−) children who were 4 to 8 years old (for IL-6, 96.2 pg/ml versus 137.2 pg/ml [P= 0.08]; for IL-10, 195.9 pg/ml versus 282.2 pg/ml [P= 0.06]). The level of IL-10 was similarly lower in Sch(+) children than in Sch(−) children who were 9 to 14 years old (91.2 pg/ml versus 141.2 pg/ml [P= 0.03]). IL-4 levels were inversely correlated with the time until the first malaria infection in both the Sch(+) children (P< 0.001) and the Sch(−) children (P< 0.001) who were 4 to 8 years old. We postulate that the Th2-enriched environment induced by schistosomiasis protects against malaria and alters the cytokine milieu during an actual infection.
Fatty Acids fromPlasmodium falciparumDown-Regulate the Toxic Activity of Malaria Glycosylphosphatidylinositols
Authors: Debierre-Grockiego Françoise , Schofield Louis , Azzouz Nahid , Schmidt Jörg , Santos de Macedo Cristiana , Ferguson Michael A. J. , Schwarz Ralph T. 
Published: September 2006

ABSTRACTPlasmodium falciparummalaria kills roughly 2.5 million people, mainly children, annually. Much of this mortality is thought to arise from the actions of a malarial toxin. This toxin, identified as glycosylphosphatidylinositol (GPI), is a major pathogenicity determinant in malaria. A malarial molecule, Pfj, labeled by [3H]glucosamine like the GPIs, was identified as a non-GPI molecule. Here we show that Pfj is able to down-regulate tumor necrosis factor alpha (TNF-α) production induced by the GPI ofP. falciparum. Mass spectrometry analysis showed that Pfj was not a single molecule but represented a number of molecules. Separation methods, such as cation-exchange chromatography and thin-layer chromatography, were used to isolate and identify the following four main fatty acids responsible for the inhibitory effect on TNF-α production: myristic, pentadecanoic, palmitic, and palmitoleic acids. This regulatory effect on cytokine production suggests that there is balanced bioactivity for the different categories of malarial lipids.
Role of Eosinophils and Neutrophils in Innate and Adaptive Protective Immunity to LarvalStrongyloides stercoralisin Mice
Authors: Galioto Ann Marie , Hess Jessica A. , Nolan Thomas J. , Schad Gerhard A. , Lee James J. , Abraham David 
Published: September 2006

ABSTRACTThe goal of this study was to determine the roles of eosinophils and neutrophils in innate and adaptive protective immunity to larvalStrongyloides stercoralisin mice. The experimental approach used was to treat mice with an anti-CCR3 monoclonal antibody to eliminate eosinophils or to use CXCR2−/−mice, which have a severe neutrophil recruitment defect, and then determine the effect of the reduction or elimination of the particular cell type on larval killing. It was determined that eosinophils killed theS. stercoralislarvae in naïve mice, whereas these cells were not required for the accelerated killing of larvae in immunized mice. Experiments using CXCR2−/−mice demonstrated that the reduction in recruitment of neutrophils resulted in significantly reduced innate and adaptive protective immunity. Protective antibody developed in the immunized CXCR2−/−mice, thereby demonstrating that neutrophils were not required for the induction of the adaptive protective immune response. Moreover, transfer of neutrophil-enriched cell populations recovered from either wild-type or CXCR2−/−mice into diffusion chambers containing larvae demonstrated that larval killing occurred with both cell populations when the diffusion chambers were implanted in immunized wild-type mice. Thus, the defect in the CXCR2−/−mice was a defect in the recruitment of the neutrophils and not a defect in the ability of these cells to kill larvae. This study therefore demonstrated that both eosinophils and neutrophils are required in the protective innate immune response, whereas only neutrophils are necessary for the protective adaptive immune response to larvalS. stercoralisin mice.
Prevention of home-related injuries of preschoolers: Safety measures taken by mothers
Authors: Al-Khameesa Nedaa A 
Published: September 2006

Objective The aim of this study was to find out the extent of safety measures taken by mothers to prevent serious injuries to their pre-school children in the home, and the factors that influence mothers' behaviour in taking these safety measures. Design A self-completion questionnaire based on a Five Level Likert Scale was used in the study. Setting Respondents were mothers with pre-school children througout the state of Kuwait. Methods 550 questionnaires were personally distributed to, and colected from, a random sampling of college students and their families, employees in selected ministries and companies, and to attendees at selected gatherings. Results 510 fully completed questionnaires were returned. Mothers were most safety conscious in the bathroom and in preventing children from falling, least aware of hazards in the living room, and had modeate use of safety measures in respect of hazards in the child's bedroom and prevention of burns and poisoning. Correlation of these results with demographic data showed the mother's educational level, number of children, age, marital status, residential status and occupational status all influenced the degree of use of safety measures. Conclusion Emphasis should be given to the several safety measures found to be not used by a significant number of mothers, and each such measure should be advocated separately. Mothers with lesser education, student mothers, mothers with larger families, and widowed or divorced mothers should be especially targeted.
Barriers to uptake of eye care services by the Indian population living in Ealing, west London
Authors: Patel Daksha , Baker Helen , Murdoch Ian 
Published: September 2006

Background Despite a relatively high prevalence of eye disease, the Indian population in London does not fully utilize the available eye care services. This study in Ealing, London was aimed at determining the reasons for poor utilization of eye care services. Methods Qualitative research methods were used. These included: focus group discussions with community members and religious leaders; semi-structured interviews with general practitioners and Indian patients attending the eye unit for the first time at Ealing hospital, and non-participatory observation methods. Results Attitudinal barriers showing visual health is not a priority and the elderly are resigned to a ‘fate’ of poor vision in old age. Difficulties in the patient-doctor relationship at the primary care level that cause delays in gaining access to specialist care. Dissatisfaction at hospital level due to long waiting lists and poor communication with specialists and staff. Although the community does not perceive language as a major barrier, the majority of patients receiving health care in the hospital system still need interpreters often resulting in dissatisfaction and misconceptions. Conclusion The social attitudes towards visual health issues, along with the perceived difficulties with their general practitioners result in delays in seeking help for their visual impairment. These are the principal barriers that would have to be addressed if uptake of services is to be improved.