bluuebunny/crossref_metadata_2025 huggingface dataset:
Microwave Dielectric Properties of Hexagonal 12R‐Ba3LaNb3O12 Ceramics
Authors: Rawal Ritesh , Feteira Antonio , Hyatt Neil C. , Sinclair Derek C. , Sarma Kumaravinothan , Alford Neil McN.
Published: September 2005

The dielectric properties of dense ceramics of the n=0 member of a newly identified homologous series Ba3+nLaNb3TinO12+3n, where n=0, 1, and 2, are reported. Single‐phase powders can be obtained from the mixed‐oxide route at 1350°C and dense ceramics (>97% of the theoretical X‐ray density) with uniform microstructures (3–5 μm) can be obtained by sintering in air at 1500°C. The ceramics are excellent dc insulators with a band gap >2.6 eV that resonate at microwave frequencies with a relative permittivity, ɛr∼44, a quality factor, Q×fr, of ∼9000 at fr∼5.5 GHz and a temperature coefficient of resonant frequency, TCf,∼−100 ppm/K.
Cellular Molybdenum Silicide/Silicon Carbide Composites from Stems of Maize
Authors: Bhattacharya Anup K. , Heinrich Juergen G.
Published: September 2005

Biomimicking of woods has been conducted extensively in the past. In this work, the unique microstructural feature of maize stems has been explored. These stems appear to be promising precursor materials for producing fiber‐reinforced composites with unique anisotropic properties. A unique melt infiltration technique has been adopted to mineralize this structure into ceramic composites. The cellular morphology of the precursor stem was retained in the final composite. SiC–Si and MoSi2–SiC cellular composites were obtained by infiltration with Si and Si–MoSi2–Al mixture, respectively. It has been found that a small (2 wt%) addition of aluminum in the infiltrating mixture can help in attaining a homogeneous distribution of MoSi2 in the SiC cellular matrix.
Characterization of Ion Distributions Near the Surface of Sodium‐Containing and Sodium‐Depleted Calcium Aluminosilicate Melts
Authors: Corrales L. René , Du Jincheng
Published: September 2005

The distribution of cation and anion components of sodium calcium aluminosilicate was studied by classical molecular dynamics simulations in a high‐temperature melt in the bulk and at the vacuum–melt interface. A significant redistribution of the sodium and non‐bridging oxygen (NBO) ions was observed. Subsequently, a sodium depleted calcium aluminosilicate melt was simulated to determine the sensitivity of the redistribution of ions near the vacuum–melt interface to the presence of sodium ions. It is found that the thermodynamic equilibrium condition near the melt surface favors the enrichment of NBO ions that is closely associated with enrichment of the sodium ions.
TheSalmonella entericaSerovar TyphitsxGene, Encoding a Nucleoside-Specific Porin, Is Essential for Prototrophic Growth in the Absence of Nucleosides
Authors: Bucarey Sergio A. , Villagra Nicolás A. , Martinic Mara P. , Trombert A. Nicole , Santiviago Carlos A. , Maulén Nancy P. , Youderian Philip , Mora Guido C.
Published: September 2005

TheSalmonella entericaserovar Typhitsxgene encodes a porin that facilitates the import of nucleosides. When serovar Typhi is grown under anaerobic conditions, Tsx is among the outer membrane proteins whose expression increases dramatically. This increase in expression is due, at least in part, to increased transcription and is dependent on Fnr but not on ArcA. A mutant derivative of serovar Typhi strain STH2370 with a deletion of thetsxgene is an auxotroph that requires either adenosine or thymidine for growth on minimal medium. In contrast, an otherwise isogenicnupG nupCdouble mutant, defective in the inner membrane nucleoside permeases, is a prototroph. Because anaerobic growth enhances the virulence of serovar Typhi in vitro, we assessed the role that thetsxgene plays in pathogenicity and found that the serovar Typhi STH2370 Δtsxmutant is defective in survival within human macrophage-like U937 cells. To understand why the Δtsxmutant is an auxotroph, we selected for insertions of minitransposon T-POP in the Δtsxgenetic background that restored prototrophy. One T-POP insertion that suppressed the Δtsxmutation in the presence of the inducer tetracycline was located upstream of thepyrDgene. The results of reverse transcription-PCR analysis showed that addition of the inducer decreased the rate ofpyrDtranscription. These results suggest that the Tsx porin and the balance of products of thetsxandpyrDgenes play critical roles in membrane assembly and integrity and thus in the virulence of serovar Typhi.
Major Histocompatibility Complex Class II Inhibits Fas Antigen-Mediated Gastric Mucosal Cell Apoptosis through Actin-Dependent Inhibition of Receptor Aggregation
Authors: Stoicov Calin , Cai Xun , Li Hanchen , Klucevsek Kristine , Carlson Jane , Saffari Reza , Houghton JeanMarie
Published: September 2005

Escape from normal apoptotic controls is thought to be essential for the development of cancer. DuringHelicobacter pyloriinfection, the leading cause of gastric cancer, activation of the Fas antigen (Fas Ag) apoptotic pathway is responsible for early atrophy and tissue loss. As disease progresses, metaplastic and dysplastic glands arise which express Fas Ag but are resistant to apoptosis and are believed to be the precursor cells for adenocarcinoma. In this report, we show that one mechanism of acquired Fas resistance is inhibition of receptor aggregation via a major histocompatibility complex class II (MHCII)-mediated, actin-dependent mechanism. For these studies we used the well-described C57BL/6 mouse model ofHelicobacter pyloriandHelicobacter felisinfection. Under normal conditions, Fas Ag is expressed at low levels, and MHCII expression on gastric mucosal cells is negligible. With infection and inflammation, both receptors are upregulated, and 6.1% of gastric mucosal cells express MHCII in combination with Fas Ag. Using the rat gastric mucosal cell line RGM-1 transfected with murine Fas Ag and MHCIIαβ chains, we demonstrate that MHCII prevents Fas receptor aggregation and inhibits Fas-mediated signaling through its effects on the actin cytoskeleton. Depolymerization of actin with cytochalasin D allows receptors to aggregate and restores Fas sensitivity. These findings offer one mechanism by which gastric mucosal cells acquire Fas resistance.
Conserved Structure and Function in the Granulysin and NK-Lysin Peptide Family
Authors: Linde Charlotte M. A. , Grundström Susanna , Nordling Erik , Refai Essam , Brennan Patrick J. , Andersson Mats
Published: September 2005

Granulysin and NK-lysin are homologous bactericidal proteins with a moderate residue identity (35%), both of which have antimycobacterial activity. Short loop peptides derived from the antimycobacterial domains of granulysin, NK-lysin, and a putative chicken NK-lysin were examined and shown to have comparable antimycobacterial but variableEscherichia coliactivities. The known structure of the NK-lysin loop peptide was used to predict the structure of the equivalent peptides of granulysin and chicken NK-lysin by homology modeling. The last two adopted a secondary structure almost identical to that of NK-lysin. All three peptides form very similar three-dimensional (3-D) architectures in which the important basic residues assume the same positions in space. The basic residues in granulysin are arginine, while those in NK-lysin and chicken NK-lysin are a mixture of arginine and lysine. We altered the ratio of arginine to lysine in the granulysin fragment to examine the importance of basic residues for antimycobacterial activity. The alteration of the amino acids reduced the activity againstE. colito a larger extent than that againstMycobacterium smegmatis. In granulysin, the arginines in the loop structure are not crucial for antimycobacterial activity but are important for cytotoxicity. We suggest that the antibacterial domains of the related proteins granulysin, NK-lysin, and chicken NK-lysin have conserved their 3-D structure and their function against mycobacteria.
Specific Antibody Can Prevent Fungal Biofilm Formation and This Effect Correlates with Protective Efficacy
Authors: Martinez Luis R. , Casadevall Arturo
Published: September 2005

One of the most troublesome medical problems today is infection of prosthetic devices with organisms that form polysaccharide biofilms. This combined with increasing antimicrobial drug resistance is making many infectious diseases incurable.
Cryptococcus neoformans
is a human-pathogenic fungus that has a polysaccharide capsule and can form biofilms in prosthetic medical devices. We developed a system to study cryptococcal biofilm formation in vitro and studied the effect of antibody to the
C. neoformans
capsular polysaccharide on this process.
C. neoformans
biofilm formation was dependent on the presence of a polysaccharide capsule and correlated with the ability of capsular polysaccharide to bind the polystyrene solid support. Protective antibodies prevented biofilm formation whereas nonprotective antibodies were not effective. The mechanism of antibody action involved interference with capsular polysaccharide release from the fungal cell. In contrast, lactoferrin, an effector molecule of innate immune mechanisms, was unable to prevent fungal biofilm formation despite its efficacy against bacterial biofilms. Our results suggest a new role of adaptive humoral immunity whereby some antibodies can inhibit biofilm formation by encapsulated organisms. Vaccines that elicit antibody responses to capsular antigens and/or passive transfer of antibodies to microbial polysaccharides may be useful in preventing biofilm formation.
The Type III Secretion System and Cytotoxic Enterotoxin Alter the Virulence of
Aeromonas hydrophila
Authors: Sha Jian , Pillai Lakshmi , Fadl Amin A. , Galindo Cristi L. , Erova Tatiana E. , Chopra Ashok K.
Published: September 2005

Many gram-negative bacteria use a type III secretion system (TTSS) to deliver effector proteins into host cells. Here we report the characterization of a TTSS chromosomal operon from the diarrheal isolate SSU of
Aeromonas hydrophila
. We deleted the gene encoding
Aeromonas
outer membrane protein B (AopB), which is predicted to be involved in the formation of the TTSS translocon, from wild-type (WT)
A. hydrophila
as well as from a previously characterized cytotoxic enterotoxin gene (
act
)-minus strain of
A. hydrophila
, thus generating
aopB
and
act/aopB
isogenic mutants. The
act
gene encodes a type II-secreted cytotoxic enterotoxin (Act) that has hemolytic, cytotoxic, and enterotoxic activities and induces lethality in a mouse model. These isogenic mutants (
aopB
,
act
, and
act/aopB
) were highly attenuated in their ability to induce cytotoxicity in RAW 264.7 murine macrophages and HT-29 human colonic epithelial cells. The
act/aopB
mutant demonstrated the greatest reduction in cytotoxicity to cultured cells after 4 h of infection, as measured by the release of lactate dehydrogenase enzyme, and was avirulent in mice, with a 90% survival rate compared to that of animals infected with Act and AopB mutants, which caused 50 to 60% of the animals to die at a dose of three 50% lethal doses. In contrast, WT
A. hydrophila
killed 100% of the mice within 48 h. The effects of these mutations on cytotoxicity could be complemented with the native genes. Our studies further revealed that the production of lactones, which are involved in quorum sensing (QS), was decreased in the
act
(32%) and
aopB
(64%) mutants and was minimal (only 8%) in the
act/aopB
mutant, compared to that of WT
A. hydrophila
SSU. The effects of
act
and
aopB
gene deletions on lactone production could also be complemented with the native genes, indicating specific effects of Act and the TTSS on lactone production. Although recent studies with other bacteria have indicated TTSS regulation by QS, this is the first report describing a correlation between the TTSS and Act of
A. hydrophila
and the production of lactones.
Effects of RepeatedChlamydia pneumoniaeInoculations on Aortic Lipid Accumulation and Inflammatory Response in C57BL/6J Mice
Authors: Törmäkangas Liisa , Erkkilä Leena , Korhonen Taina , Tiirola Terttu , Bloigu Aini , Saikku Pekka , Leinonen Maija
Published: September 2005

Chlamydia pneumoniaeis a common respiratory tract pathogen, and persistent infections have been associated with atherosclerosis. We studied the effects of repeated chlamydial inoculations on the inflammatory response and on aortic lipid accumulation in C57BL/6J mice. Mice fed a diet supplemented with 0.2% cholesterol were infected three or six times withC. pneumoniaeevery fourth week. Sera and lungs were analyzed for inflammatory responses, lung tissues were tested for the presence ofC. pneumoniaeDNA and RNA, and intimal lipid accumulation in the aortic sinus was quantified. High levels of chlamydial heat shock protein 60 (Hsp60) immunoglobulin G2c subclass antibodies were detected in all of the infected mice, and a positive and statistically significant correlation was found between these antibodies and autoantibodies against mouse Hsp60. Both Hsp60 antibody levels correlated with the severity of lung tissue inflammation. The cholesterol supplement in the diet had no effect on serum cholesterol levels. Significantly larger intimal lipid lesions were seen in the mouse group infected six times (6,542 μm2) than in the control group (1,376 μm2;P= 0.034). In conclusion, repeated inoculations increased aortic sinus lipid accumulation in normocholesterolemic mice. The correlation between the antibodies to mouse and chlamydial Hsp60 proteins and their association with lung inflammation further support the theory of the development of an autoimmune response against heat shock proteins after repeated chlamydial infections.
The Apoptotic Response to Pneumolysin Is Toll-Like Receptor 4 Dependent and Protects against Pneumococcal Disease
Authors: Srivastava Amit , Henneke Philipp , Visintin Alberto , Morse Sarah C. , Martin Victoria , Watkins Claire , Paton James C. , Wessels Michael R. , Golenbock Douglas T. , Malley Richard
Published: September 2005

Pneumolysin, the cholesterol-dependent cytolysin ofStreptococcus pneumoniae, induces inflammatory and apoptotic events in mammalian cells. Toll-like receptor 4 (TLR4) confers resistance to pneumococcal infection via its interaction with pneumolysin, but the underlying mechanisms remain to be identified. In the present study, we found that pneumolysin-induced apoptosis is also mediated by TLR4 and confers protection against invasive disease. The interaction between TLR4 and pneumolysin is direct and specific; ligand-binding studies demonstrated that pneumolysin binds to TLR4 but not to TLR2. Involvement of TLR4 in pneumolysin-induced apoptosis was demonstrated in several complementary experiments. First, macrophages from wild-type mice were significantly more prone to pneumolysin-induced apoptosis than cells from TLR4-defective mice. In gain-of-function experiments, we found that epithelial cells expressing TLR4 and stimulated with pneumolysin were more likely to undergo apoptosis than cells expressing TLR2. A specific TLR4 antagonist, B1287, reduced pneumolysin-mediated apoptosis in wild-type cells. This apoptotic response was also partially caspase dependent as preincubation of cells with the pan-caspase inhibitor zVAD-fmk reduced pneumolysin-induced apoptosis. Finally, in a mouse model of pneumococcal infection, pneumolysin-producing pneumococci elicited significantly more upper respiratory tract cell apoptosis in wild-type mice than in TLR4-defective mice, and blocking apoptosis by administration of zVAD-fmk to wild-type mice resulted in a significant increase in mortality following nasopharyngeal pneumococcal exposure. Overall, our results strongly suggest that protection against pneumococcal disease is dependent on the TLR4-mediated enhancement of pneumolysin-induced apoptosis.
Clearance ofBordetella parapertussisfrom the Lower Respiratory Tract Requires Humoral and Cellular Immunity
Authors: Wolfe Daniel N. , Kirimanjeswara Girish S. , Harvill Eric T.
Published: September 2005

Bordetella parapertussisandBordetella pertussisare closely related species that cause whooping cough, an acute, immunizing disease. Their coexistence in the same host populations at the same time and vaccine studies showing thatB. pertussisvaccines have little effect onB. parapertussisinfection or disease suggest that the protective immunity induced by each does not efficiently cross protect against the other. Although the mechanisms of protective immunity toB. pertussishave been well studied, those ofB. parapertussishave not. The present study explores the mechanism by whichB. parapertussisis cleared from the lower respiratory tract by anamnestic immunity. Serum antibodies are necessary and sufficient for elimination of this bacterium, and CD4+T cells, complement, and neutrophils are required for serum antibody-mediated clearance. Mice lacking immunoglobulin A had no defect in their ability to control or clear infection. Interestingly, serum antibody-mediated clearance ofB. parapertussisdid not require Fc receptors that are required for antibody-mediated clearance ofB. pertussis. Together these data support a model for the mechanism of protective immunity toB. parapertussisthat is similar but distinct from that ofB. pertussis.
Recombinant Shiga Toxin B-Subunit-Keyhole Limpet Hemocyanin Conjugate Vaccine Protects Mice from Shigatoxemia
Authors: Marcato Paola , Griener Thomas P. , Mulvey George L. , Armstrong Glen D.
Published: September 2005

Enterohemorrhagic
Escherichia coli
(EHEC) causes hemorrhagic colitis in humans and, in a subgroup of infected subjects, a more serious condition called hemolytic-uremic syndrome (HUS). These conditions arise because EHEC produces two antigenically distinct forms of Shiga toxin (Stx), called Stx1 and Stx2. Despite this, the production of Stx2 by virtually all EHEC serotypes and the documented role this toxin plays in HUS make it an attractive vaccine candidate. Previously, we assessed the potential of a purified recombinant Stx2 B-subunit preparation to prevent Shigatoxemia in rabbits. This study revealed that effective immunization could be achieved only if endotoxin was included with the vaccine antigen. Since the presence of endotoxin would be unacceptable in a human vaccine, the object of the studies described herein was to investigate ways to safely augment, in mice, the immunogenicity of the recombinant Stx2 B subunit containing <1 endotoxin unit per ml. The study revealed that sera from mice immunized with such a preparation, conjugated to keyhole limpet hemocyanin and administered with the Ribi adjuvant system, displayed the highest Shiga toxin 2 B-subunit-specific immunoglobulin G1 (IgG1) and IgG2a enzyme-linked immunosorbent assay titers and cytotoxicity-neutralizing activities in Ramos B cells. As well, 100% of the mice vaccinated with this preparation were subsequently protected from a lethal dose of Stx2 holotoxin. These results support further evaluation of a Stx2 B-subunit-based human EHEC vaccine.
A DNA Vaccine Coding for theBrucellaOuter Membrane Protein 31 Confers Protection againstB. melitensisandB. ovisInfection by Eliciting a Specific Cytotoxic Response
Authors: Cassataro Juliana , Velikovsky Carlos A. , de la Barrera Silvia , Estein Silvia M. , Bruno Laura , Bowden Raúl , Pasquevich Karina A. , Fossati Carlos A. , Giambartolomei Guillermo H.
Published: September 2005

The development of an effective subunit vaccine against brucellosis is a research area of intense interest. The outer membrane proteins (Omps) ofBrucellaspp. have been extensively characterized as potential immunogenic and protective antigens. This study was conducted to evaluate the immunogenicity and protective efficacy of theB. melitensisOmp31 gene cloned in the pCI plasmid (pCIOmp31). Immunization of BALB/c mice with pCIOmp31 conferred protection againstB. ovisandB. melitensisinfection. Mice vaccinated with pCIOmp31 developed a very weak humoral response, and in vitro stimulation of their splenocytes with recombinant Omp31 did not induced the secretion of gamma interferon. Splenocytes from Omp31-vaccinated animals induced a specific cytotoxic-T-lymphocyte activity, which leads to the in vitro lysis ofBrucella-infected macrophages. pCIOmp31 immunization elicited mainly CD8+T cells, which mediate cytotoxicity via perforins, but also CD4+T cells, which mediate lysis via the Fas-FasL pathway. In vivo depletion of T-cell subsets showed that the pCIOmp31-induced protection againstBrucellainfection is mediated predominantly by CD8+T cells, although CD4+T cells also contribute. Our results demonstrate that the Omp31 DNA vaccine induces cytotoxic responses that have the potential to contribute to protection againstBrucellainfection. The protective response could be related to the induction of CD8+T cells that eliminateBrucella-infected cells via the perforin pathway.
Reduction in Capsular Content and Enhanced Bacterial Susceptibility to Serum Killing of
Vibrio cholerae
O139 Associated with the 2002 Cholera Epidemic in Bangladesh
Authors: Qadri Firdausi , Svennerholm Ann-Mari , Shamsuzzaman Sohel , Bhuiyan Taufiqur Rahman , Harris Jason B. , Ghosh A. N. , Nair G. Balakrish , Weintraub Andrej , Faruque Shah M. , Ryan Edward T. , Sack David A. , Calderwood Stephen B.
Published: September 2005

Vibrio cholerae
O139 emerged in 1992 as a major cause of epidemic cholera. However, the incidence of disease due to this new serogroup subsequently decreased for almost a decade. In April 2002, there was a dramatic resurgence of
V. cholerae
O139 in Bangladesh. We compared the phenotypic properties of the bacterial isolates and the immunological responses in patients with disease due to
V. cholerae
O139 during the 2002 epidemic with those dating to the emergence of this disease in 1993 to 1995. Strains isolated from patients in the two time periods were compared with respect to capsular polysaccharide, their resistance to the bactericidal effect of serum, and their capacity to be used as target strains in complement-mediated vibriocidal assays. Phase-contrast microscopy showed that strains isolated in 2002 had less capsular material than those isolated from 1993 to 1995 (
P
= <0.001), a finding confirmed by electron microscopic studies. Strains isolated in 2002 were more susceptible to the bactericidal activity of serum compared to strains from 1993 to 1995 (
P
= 0.013). Compared to results using a standard O139 strain, a modified vibriocidal assay utilizing a 2002 strain, CIRS 134, as the target organism detected higher vibriocidal responses in both O139-infected cholera patients as well as O139 vaccine recipients. The vibriocidal assay utilizing the less encapsulated 2002 strain, CIRS 134, is a more sensitive indicator of adaptive immune responses to recent infection with
V. cholerae
O139. Consequently, this assay may be useful in studies of both O139-infected patients and recipients of O139 vaccines.
Characterization ofListeria monocytogenesExpressing Anthrolysin O and Phosphatidylinositol-Specific Phospholipase C fromBacillus anthracis
Authors: Wei Zhengyu , Schnupf Pamela , Poussin Mathilde A. , Zenewicz Lauren A. , Shen Hao , Goldfine Howard
Published: September 2005

Two virulence factors ofListeria monocytogenes, listeriolysin O (LLO) and phosphatidylinositol-specific phospholipase C (PI-PLC), mediate escape of this pathogen from the phagocytic vacuole of macrophages, thereby allowing the bacterium access to the host cell cytosol for growth and spread to neighboring cells. We characterized their orthologs fromBacillus anthracisby expressing them inL. monocytogenesand characterizing their contribution to bacterial intracellular growth and cell-to-cell spread. We generated a series ofL. monocytogenesstrains expressingB. anthracisanthrolysin O (ALO) and PI-PLC in place of LLO andL. monocytogenesPI-PLC, respectively. We found that ALO was active at both acidic and neutral pH and could functionally replace LLO in mediating escape from a primary vacuole; however, ALO exerted a toxic effect on the host cell by damaging the plasma membrane.B. anthracisPI-PLC, unlike theL. monocytogenesortholog, had high activity on glycosylphosphatidylinositol-anchored proteins.L. monocytogenesexpressingB. anthracisPI-PLC showed significantly decreased efficiencies of escape from a phagosome and in cell-to-cell spread. We further compared the level of cytotoxicity to host cells by using mutant strains expressing ALO in combination either withL. monocytogenesPI-PLC or withB. anthracisPI-PLC. The results demonstrated that the mutant strain expressing the combination of ALO andB. anthracisPI-PLC caused less damage to host cells than the strain expressing ALO andL. monocytogenesPI-PLC. The present study indicates that LLO andL. monocytogenesPI-PLC has adapted forL. monocytogenesintracellular growth and virulence and suggests that ALO andB. anthracisPI-PLC may have a role inB. anthracispathogenesis.
Variable Tick Protein in Two Genomic Groups of the Relapsing Fever Spirochete
Borrelia hermsii
in Western North America
Authors: Porcella Stephen F. , Raffel Sandra J. , Anderson Donald E. , Gilk Stacey D. , Bono James L. , Schrumpf Merry E. , Schwan Tom G.
Published: September 2005

Borrelia hermsii
is the primary cause of tick-borne relapsing fever in North America. When its tick vector,
Ornithodoros hermsi
, acquires these spirochetes from the blood of an infected mammal, the bacteria switch their outer surface from one of many bloodstream variable major proteins (Vmps) to a unique protein, Vtp (Vsp33). Vtp may be critical for successful tick transmission of
B. hermsii
; however, the gene encoding this protein has been described previously in only one isolate. Here we identified and sequenced the
vtp
gene in 31 isolates of
B. hermsii
collected over 40 years from localities throughout much of its known geographic distribution. Seven major Vtp types were found. Little or no sequence variation existed within types, but between them significant variation was observed, similar to the pattern of diversity described for the outer surface protein C (OspC) gene in Lyme disease spirochetes. The pattern of sequence relatedness among the Vtp types was incongruent in two branches compared to two genomic groups identified among the isolates by multilocus sequence typing of the
16S rRNA
,
flaB
,
gyrB
, and
glpQ
genes. Therefore, both horizontal transfer and recombination within and between the two genomic groups were responsible for some of the variation observed in the
vtp
gene.
O. hermsi
ticks were capable of transmitting spirochetes in the newly identified genomic group. Therefore, given the longevity of the tick vector and persistent infection of spirochetes in ticks, these arthropods rather than mammals may be the likely host where the exchange of spirochetal DNA occurs.
Plasmodium bergheiResists Killing by Reactive Oxygen Species
Authors: Sobolewski Peter , Gramaglia Irene , Frangos John A. , Intaglietta Marcos , van der Heyde Henri
Published: September 2005

Reactive oxygen species (ROS) are widely believed to kill malarial parasites. C57BL/6 mice injected withP. bergheiinocula incubated with supraphysiological doses of NO (≤150 μM) or with peroxynitrite (220 μM), however, exhibited parasitemia similar to that seen with those given control inocula, and there was no difference in disease development. Only treatment of inocula with NO doses nearing saturation (≥1.2 mM) resulted in no detectable parasitemia in the recipients; flow cytometric analysis with a vital dye (hydroethidine) indicated that 1.5 mM NO lysed the erythrocytes rather than killing the parasites. The hemoglobin level in the inocula was about 8 μM; the hemoglobin was mainly oxyhemoglobin (oxyHb) (96%), which was converted to methemoglobin (>95%) after treatment with 150 μM NO. The concentrations of 150 μM of NO and 220 μM of peroxynitrite were far in excess of the hemoglobin concentration (∼8 μM), and yet no parasite killing was detected. We therefore conclude that hemoglobin protectsPlasmodiumparasites from ROS, but the parasite likely possesses intrinsic defense mechanisms against ROS.
Isocitrate Lyase Activity Is Required for Virulence of the Intracellular Pathogen
Rhodococcus equi
Authors: Wall Daniel M. , Duffy Pamela S. , DuPont Chris , Prescott John F. , Meijer Wim G.
Published: September 2005

Rhodococcus equi
is an important pathogen of foals, causing severe pyogranulomatous pneumonia. Virulent
R. equi
strains grow within macrophages, a process which remains poorly characterized. A potential source of carbon for intramacrophage
R. equi
is membrane lipid-derived fatty acids, which following β oxidation are assimilated via the glyoxylate bypass. To assess the importance of isocitrate lyase, the first enzyme of the glyoxylate bypass, in virulence of a foal isolate of
R. equi
, a mutant was constructed by a strategy of single homologous recombination using a suicide plasmid containing an internal fragment of the
R. equi aceA
gene encoding isocitrate lyase. Complementation of the resulting mutant with
aceA
showed that the mutant was specific for this gene. Assessment of virulence in a mouse macrophage cell line showed that the mutant was killed, in contrast to the parent strain. Studies in the liver of intravenously infected mice showed enhanced clearance of the mutant. When four 3-week-old foals were infected intrabronchially, the
aceA
mutant was completely attenuated, in contrast to the parent strain. In conclusion, the
aceA
gene was shown to be essential for virulence of
R. equi
, suggesting that membrane lipids may be an important source of carbon for phagocytosed
R. equi.
Keratinocyte Production of Cathelicidin Provides Direct Activity against Bacterial Skin Pathogens
Authors: Braff Marissa H. , Zaiou Mohamed , Fierer Joshua , Nizet Victor , Gallo Richard L.
Published: September 2005

Immune defense at an interface with the external environment reflects the functions of physical and chemical barriers provided by epithelial and immune cells. Resident epithelial cells, such as keratinocytes, produce numerous peptides with direct antimicrobial activity but also provide a physical barrier against invading pathogens and signal the recruitment of circulating immune cells, such as neutrophils. Antimicrobial peptides such as cathelicidin are produced constitutively by neutrophils and are inducible in keratinocytes in response to infection. The multiplicity of antimicrobial peptides and their cellular sources has resulted in an incomplete understanding of the role of cathelicidin production by epithelial cells in cutaneous immune defense. Therefore, this study sought to evaluate keratinocyte antimicrobial activity and the potential contribution of keratinocyte cathelicidin to host protection against two leading human skin pathogens. Wild-type mice and those with a targeted deletion of the cathelicidin gene,
Cnlp
, were rendered neutropenic prior to cutaneous infection. Interestingly,
Cnlp
-deficient mice remained more susceptible to group A streptococcus infection than mice with
Cnlp
intact, suggesting the involvement of epithelial cell-derived cathelicidin in host immune defense. Keratinocytes were then isolated in culture and found to inhibit the growth of
Staphylococcus aureus
, an effect that was partially dependent on their ability to synthesize and activate cathelicidin. Further, lentivirus-mediated delivery of activated human cathelicidin enhanced keratinocyte antimicrobial activity. Combined, these data illustrate the potential contribution of keratinocyte cathelicidin to the innate immune defense of skin against bacterial pathogens and highlight the need to consider epithelial antimicrobial function in the diagnosis and therapy of skin infection.
Effect of Deletion or Overexpression of the 19-Kilodalton Lipoprotein Rv3763 on the Innate Response to
Mycobacterium tuberculosis
Authors: Stewart Graham R. , Wilkinson Katalin A. , Newton Sandra M. , Sullivan Susan M. , Neyrolles Olivier , Wain John R. , Patel Janisha , Pool Kara-Lee , Young Douglas B. , Wilkinson Robert J.
Published: September 2005

The 19-kDa lipoprotein of
Mycobacterium tuberculosis
is an important target of the innate immune response. To investigate the immune biology of this antigen in the context of the whole bacillus, we derived a recombinant
M. tuberculosis
H37Rv that lacked the 19-kDa-lipoprotein gene (Δ19) and complemented this strain by reintroduction of the 19-kDa-lipoprotein gene on a multicopy vector to produce Δ19::pSMT181. The Δ19 strain multiplied less well than Δ19::pSMT181 in human monocyte-derived macrophages (MDM) (
P
= 0.039). Surface expression of major histocompatibility complex class II molecules was reduced in phagocytes infected with
M. tuberculosis
; this effect was not seen in cells infected with Δ19. Δ19 induced lower interleukin 1β (IL-1β) secretion from monocytes and MDM. Overexpression of the 19-kDa protein increased IL-1β, IL-12p40, and tumor necrosis factor alpha secretion irrespective of phagocyte maturity. These data support reports that the 19-kDa lipoprotein has pleiotropic effects on the interaction of
M. tuberculosis
with phagocytes. However, this analysis indicates that in the context of the whole bacillus, the 19-kDa lipoprotein is only one of a number of molecules that mediate the innate response to
M. tuberculosis
.
Antibody Profiles Characteristic ofMycobacterium tuberculosisInfection State
Authors: Davidow Amy , Kanaujia Ganga V. , Shi Lanbo , Kaviar Justin , Guo XuDong , Sung Nackmoon , Kaplan Gilla , Menzies Dick , Gennaro Maria L.
Published: September 2005

The relationship between specific antibody profiles and tuberculosis (TB) state was investigated by measuring serum antibody levels to sixMycobacterium tuberculosisantigens in human subjects grouped into four diagnostic categories: active disease, inactive (past) tuberculosis, latent infection without radiographic chest abnormalities, and infection free. Statistical data analyses showed that the latter two groups were serologically indistinguishable and that active tuberculosis and inactive tuberculosis were characterized by different antibody profiles. Antibodies to the 38-kDa antigen, alanine dehydrogenase, and Rv2626c were associated with active TB, while antibodies to the 16-kDa antigen, ferredoxin A, and ESAT-6 were associated with inactive TB. Thus, the targets of the immune response vary with tuberculosis state. The correlation between bacterial antigen production and infection stage was investigated in mice infected withM. tuberculosisby bacterial transcription profiling. It was found that levels of transcripts encoding the sixM. tuberculosisantigens varied during infection. Together, the data indicate that antigen composition of tubercle bacilli varies with stage of infection and that immunoprofiling can distinguish between tuberculosis states.
Colonization of the Cecal Mucosa by
Helicobacter hepaticus
Impacts the Diversity of the Indigenous Microbiota
Authors: Kuehl Carole J. , Wood Heather D. , Marsh Terence L. , Schmidt Thomas M. , Young Vincent B.
Published: September 2005

Establishment of mucosal and/or luminal colonization is the first step in the pathogenesis of many gastrointestinal bacterial pathogens. The pathogen must be able to establish itself in the face of competition from the complex microbial community that is already in place. We used culture-independent methods to monitor the colonization of the cecal mucosa of
Helicobacter
-free mice following experimental infection with the pathogen
Helicobacter hepaticus
. Two days after infection,
H. hepaticus
comprised a minor component of the mucosa-associated microbiota, but within 14 days, it became the dominant member of the community. Colonization of the mucosa by
H. hepaticus
was associated with a decrease in the overall diversity of the microbial community, in large part due to changes in evenness resulting from the relative dominance of
H. hepaticus
as a member of the community. Our results demonstrate that invasion of the complex gastrointestinal microbial community by a pathogenic microorganism causes reproducible and significant disturbances in the community structure. The use of non-culture-based methods to monitor these changes should lead to a greater understanding of the ecological principles that govern pathogen invasion and may lead to novel methods for the prevention and control of gastrointestinal pathogens.
Poly-
N
-Acetylglucosamine Production in
Staphylococcus aureus
Is Essential for Virulence in Murine Models of Systemic Infection
Authors: Kropec Andrea , Maira-Litran Tomas , Jefferson Kimberly K. , Grout Martha , Cramton Sarah E. , Götz Friedrich , Goldmann Donald A. , Pier Gerald B.
Published: September 2005

The contribution of the
Staphylococcus aureus
surface polysaccharide poly-
N
-acetylglucosamine (PNAG) to virulence was evaluated in three mouse models of systemic infection: bacteremia, renal abscess formation, and lethality following high-dose intraperitoneal (i.p.) infection. Deletion of the intercellular adhesin (
ica
) locus that encodes the biosynthetic enzymes for PNAG production in
S. aureus
strains Mn8, Newman, and NCTC 10833 resulted in mutant strains with significantly reduced abilities to maintain bacterial levels in blood following intravenous or i.p. injection, to spread systemically to the kidneys following i.p. injection, or to induce a moribund/lethal state following i.p. infection. In the bacteremia model, neither growth phase nor growth medium used to prepare the
S. aureus
inoculum affected the conclusion that PNAG production was needed for full virulence. As the SarA regulatory protein has been shown to affect
ica
transcription, PNAG synthesis, and biofilm formation, we also evaluated
S. aureus
strains Mn8 and 10833 deleted for the
sarA
gene in the renal infection model. A decrease in PNAG production was seen in
sarA
mutants using immunoblots of cell surface extracts but was insufficient to reduce the virulence of
sarA
-deleted strains in this model.
S. aureus
strains deleted for the
ica
genes were much more susceptible to antibody-independent opsonic killing involving human peripheral blood leukocytes and rabbit complement. Thus, PNAG confers on
S. aureus
resistance to killing mediated by these innate host immune mediators. Overall, PNAG production by
S. aureus
appears to be a critical virulence factor as assessed in murine models of systemic infection.
Expression Library Immunization Confers Protection against
Mycobacterium avium
subsp.
paratuberculosis
Infection
Authors: Huntley J. F. , Stabel J. R. , Paustian M. L. , Reinhardt T. A. , Bannantine J. P.
Published: September 2005

Currently, paratuberculosis vaccines are comprised of crude whole-cell preparations of
Mycobacterium avium
subsp.
paratuberculosis
. Although effective in reducing clinical disease and fecal shedding, these vaccines have severe disadvantages as well, including seroconversion of vaccinated animals and granulomatous lesions at the site of vaccination. DNA vaccines can offer an alternative approach that may be safer and elicit more protective responses. In an effort to identify protective
M. avium
subsp.
paratuberculosis
sequences, a genomic DNA expression library was generated and subdivided into pools of clones (∼1,500 clones/pool). The clone pools were evaluated to determine DNA vaccine efficacy by immunizing mice via gene gun delivery and challenging them with live, virulent
M. avium
subsp.
paratuberculosis
. Four clone pools resulted in a significant reduction in the amount of
M. avium
subsp.
paratuberculosis
recovered from mouse tissues compared to mice immunized with other clone pools and nonvaccinated, infected control mice. One of the protective clone pools was further partitioned into 10 clone arrays of 108 clones each, and four clone arrays provided significant protection from both spleen and mesenteric lymph node colonization by
M. avium
subsp.
paratuberculosis
. The nucleotide sequence of each clone present in the protective pools was determined, and coding region functions were predicted by computer analysis. Comparison of the protective clone array sequences implicated 26 antigens that may be responsible for protection in mice. This study is the first study to demonstrate protection against
M. avium
subsp.
paratuberculosis
infection with expression library immunization.
LPXTG Protein InlJ, a Newly Identified Internalin Involved in
Listeria monocytogenes
Virulence
Authors: Sabet Christophe , Lecuit Marc , Cabanes Didier , Cossart Pascale , Bierne Hélène
Published: September 2005

Listeria monocytogenes
expresses surface proteins covalently anchored to the peptidoglycan by sortase enzymes. Inactivation of
srtA
attenuates
Listeria
virulence in mice (H. Bierne, S. K. Mazmanian, M. Trost, M. G. Pucciarelli, G. Liu, P. Dehoux, L. Jansch, F. Garcia-del Portillo, O. Schneewind, and P. Cossart, Mol. Microbiol.
43:
869-881, 2002). We show here that an
srtA
mutant is more attenuated than an internalin mutant in orally infected guinea pigs and transgenic mice expressing human E-cadherin (hEcad mice), indicating the involvement of other SrtA substrates, LPXTG proteins, in food-borne listeriosis. Data recently generated with a listerial DNA macroarray identified two LPXTG protein-encoding genes present in the genomes of
L. monocytogenes
strains and absent from all other
Listeria
species,
inlI
(lmo0333) and
inlJ
(lmo2821). They also revealed two other LPXTG protein-encoding genes, ORF29 and ORF2568, present only in a subclass of
L. monocytogenes
serovars, including the epidemic serovar 4b. We report here that an
inlJ
deletion mutant, in contrast to
inlI
and ORF29 mutants, is significantly attenuated in virulence after intravenous infection of mice or oral inoculation of hEcad mice. Interestingly, a ΔORF2568 strain showed a slight increase in virulence.
inlJ
encodes a leucine-rich repeat (LRR) protein that is structurally related to the listerial invasion factor internalin. However, the consensus sequence of the InlJ LRR defines a novel subfamily of cysteine-containing LRRs in bacteria. In conclusion, this postgenomic approach identified InlJ as a new virulence factor among the proteins belonging to the internalin family in
L. monocytogenes
.
Role of B Cells in Vaccine-Induced Immunity against Coccidioidomycosis
Authors: Magee D. Mitchell , Friedberg Rhonda L. , Woitaske Melanie D. , Johnston Stephen Albert , Cox Rebecca A.
Published: September 2005

We investigated secondary immunity against coccidioidomycosis by using gene expression microarrays. Surprisingly, a high percentage of B-cell-related genes were associated with protective immunity. A functional confirmation of the importance of B cells against coccidioidomycosis was achieved by demonstrating that vaccination was not fully protective in B-cell-deficient MuMT mice.
Lethal Infection of C3H/HeJ and C3H/SCID Mice with an Isolate of
Leptospira interrogans
Serovar Copenhageni
Authors: Nally Jarlath E. , Fishbein Michael C. , Blanco David R. , Lovett Michael A.
Published: September 2005

Leptospira interrogans
serovar Copenhageni strain RJ16441, a blood isolate from humans with the severe pulmonary form of leptospirosis, has previously been shown to cause fatal pulmonary hemorrhage in guinea pigs and asymptomatic chronic renal tubular colonization with urinary shedding in rats. In this study, RJ16441 caused lethal infection of both C3H/HeJ and C3H/SCID mice, but no hemorrhagic phenomena were observed.
Induction of
SAP7
Correlates with Virulence in an Intravenous Infection Model of Candidiasis but Not in a Vaginal Infection Model in Mice
Authors: Taylor Brad N. , Hannemann Holger , Sehnal Miriam , Biesemeier Antje , Schweizer Anja , Röllinghoff Martin , Schröppel Klaus
Published: September 2005

SAP7
of
Candida albicans
is induced after vaginal infection of mice. Conversely, virulence during vaginal infection was not affected in a Δ
sap7/
Δ
sap7
mutant strain. Only a partial virulence phenotype was detectable after intravenous injection. In conclusion,
SAP7
expression does not correlate with
C. albicans
virulence in mice.
TRACING THE GAUGE ORIGIN OF YUKAWA AND HIGGS PARAMETERS BEYOND THE STANDARD MODEL
Authors: LORENZO DÍAZ-CRUZ J.
Published: September 2005

We discuss possible realizations of the hypothesis that all the fundamental interactions of the elementary particles should be of gauge type, including the Yukawa and Higgs ones. In the minimal SUSY extension of the standard model, where the quartic Higgs couplings are "gauged" through the D-terms, it is also possible to generate radiatively the Yukawa matrices for the light generations, thus expressing them as functions of gauge couplings. The program can also be applied to the SUSY LR model, where the possibility to induce radiatively the mixing angles, can help to make viable the parity solution to the strong CP problem. The superpotential of the model still includes some non-gauge couplings, namely, the Yukawa constants for the third generation and the trilinear terms λχ L Φχ R and [Formula: see text], involving the Higgs bi-doublet (Φ) and two pairs of doublets (χ L , χ R and their conjugates). Additional progress to relate these parameters to gauge couplings, can be made by embedding the LR model within a SUSY model SU (4)W× U (1)B-L in five dimensions, where the Higgs bi-doublet is identified as the extra component of the 5D gauge field.
LACK OF TRINIFICATION IN Z3 ORBIFOLDS OF THE SO(32) HETEROTIC STRING
Authors: GIEDT JOEL
Published: September 2005

We report results relating to the trinification scenario in some explicit string constructions that contain SU (3)3 as a gauge symmetry. These models are obtained from symmetric Z3 orbifolds of the SO (32) heterotic string with one discrete Wilson line. We highlight the obstacles that were encountered: the absence of the usual Higgs sector that would break SU (3)3→ SU (3)c× SU (2)L× U (1)Y; the presence of exotics that would generically befoul gauge coupling unification and lead to fractionally-charged states in the low energy spectrum.
GLOBAL DEFECTS IN FIELD THEORY WITH APPLICATIONS TO CONDENSED MATTER
Authors: BAZEIA D. , MENEZES J. , MENEZES R.
Published: September 2005

We review investigations on defects in systems described by real scalar fields in (D, 1) space-time dimensions. We first work in one spatial dimension, with models described by one and two real scalar fields, and in higher dimensions. We show that when the potential assumes specific form, there are models which support stable global defects for D arbitrary. We also show how to find first-order differential equations that solve the equations of motion, and how to solve models in D dimensions via soluble problems in D = 1. We illustrate the procedure examining specific models and showing how they may be used in applications in different contexts in condensed matter physics, and in other areas.
SCALE-FREE CHARACTERISTICS OF SUPPLY CHAIN DISTRIBUTION NETWORKS
Authors: SUN HUIJUN , WU JIANJUN
Published: September 2005

This paper is the first step to a study of supply chain distribution networks based on the scale-free theory, and we attempt to analyze the growth of supply chain distribution networks. We construct the supply chain distribution network and divide it into two groups. Through empirical theory and numerical study, it is found that supply chain networks have scale-free characteristics. Additionally, other three features of supply chain distribution network are proposed in this paper. Finally, the exponent of degree distribution is given.
COMPOSITION DEPENDENCE OF THE POSITRON ANNIHILATION INZn1-xBexSe
Authors: BENKABOU F.
Published: September 2005

In order to clarify the electronic and optical properties of wide-energy gap zinc-blende structure ZnSe , BeSe and their alloys, a simple pseudo-potential scheme (EPM), within an affective potential the virtual crystal approximation (VCA) which incorporates compositional disorder as an effective potential are presented.

Angular correlation of positron annihilation radiation (ACPAR) along different crystallographic directions in Zn1-xBexSe are calculated. We observe that the electron-positron momentum density increases rapidly with increasing Beryllium content.
BOSE–EINSTEIN QUASICONDENSATION IN 2D SYSTEMS
Authors: CRISAN M. , GROSU I.
Published: September 2005

We calculate the finite temperature correlation function, the coherence length and the critical temperature for a two-dimensional (2D) bosonic system, which presents the quasicondensation (a finite number of occupied states with p0≠0 momentum) effect at very low temperatures. This state, discovered experimentally, appear below a critical temperature for a finite number of particles.