bluuebunny/crossref_metadata_2025 huggingface dataset:
Cryptococcus neoformans
Capsule Structure Evolution In Vitro and during Murine Infection
Authors: Garcia-Hermoso Dea , Dromer Françoise , Janbon Guilhem
Published: May 2004

Cryptococcus neoformans
capsule structure modifications after prolonged in vitro growth or in vivo passaging have been reported previously. However, nothing is known about the dynamics of these modifications or about their environmental specificities. In this study, capsule structure modifications after mouse passaging and prolonged in vitro culturing were analyzed by flow cytometry using the glucuronoxylomannan-specific monoclonal antibody E1. The capsule structures of strains recovered after 0, 1, 8, and 35 days were compared by using the level of E1-specific epitope expression and its cell-to-cell heterogeneity within a given cell population. In vitro, according to these parameters, the diversity of the strains was higher on day 35 than it was initially, suggesting the absence of selection during in vitro culturing. In contrast, the diversity of the strains recovered from the brain tended to decrease over time, suggesting that selection of more adapted strains had occurred. The strains recovered on day 35 from the spleen and the lungs had different phenotypes than the strains isolated from the brain of the same mouse on the same day, thus strongly suggesting that there is organ specificity for
C. neoformans
strain selection. Fingerprinting of the strains recovered in vitro and in vivo over time confirmed that genotypes evolved very differently in vitro and in vivo, depending on the environment. Overall, our results suggest that organ-specific selection can occur during cryptococcosis.
Clostridium sordelliiLethal Toxin Is Maintained in a Multimeric Protein Complex
Authors: Voth Daniel E. , Qa'Dan Maen , Hamm Elaine E. , Pelfrey Joy M. , Ballard Jimmy D.
Published: May 2004

Clostridium sordelliilethal toxin (TcsL) is distinct among large clostridial toxins (LCTs), as it is markedly reduced in its rate of intoxication at pH 8.0 yet is cytotoxic at pH 4.0. Results from the present study suggest that TcsL's slow rate of intoxication at pH 8.0 is linked to formation of a high-molecular-weight complex containing dissociable pH 4.0-sensitive polypeptides. The cytosolic delivery of TcsL's enzymatic domain by using a surrogate cell entry system resulted in cytopathic effect rates similar to those of other LCTs at pH 8.0, further indicating that rate-limiting steps occurred at the point of cell entry. Since these rate-limiting steps could be overcome at pH 4.0, TcsL was examined across a range of pH values and was found to dissociate into distinct 45- to 55-kDa polypeptides between pH 4.0 and pH 5.0. The polypeptides reassociated when shifted back to pH 8.0. At pH 8.0, this complex was resistant to sodium dodecyl sulfate (SDS) and multiple proteases; however, following dissociation, the polypeptides became protease sensitive. Dissociation of TcsL, and cytotoxicity, could be blocked by preincubation with ethylene glycol bis(sulfosuccinimidylsuccinate), resulting in cross-linking of the polypeptides. TcsL was also examined at pH 8.0 by using SDS-agarose gel electrophoresis and transmission electron microscopy and was found to exist in a higher-molecular-weight complex which resolved at a size exceeding 750 kDa and also dissociated at pH 4.0. However, this complex did not reassemble following a shift back to pH 8.0. Collectively, these data suggest that TcsL is maintained in a protease-resistant, high-molecular-weight complex, which dissociates at pH 4.0, leading to cytotoxicity.
Fungal Metabolite Gliotoxin Inhibits Assembly of the Human Respiratory Burst NADPH Oxidase
Authors: Tsunawaki Shohko , Yoshida Lucia S. , Nishida Satoshi , Kobayashi Toshihiro , Shimoyama Takashi
Published: May 2004

Reactive oxygen species are a critical weapon in the killing ofAspergillus fumigatusby polymorphonuclear leukocytes (PMN), as demonstrated by severe aspergillosis in chronic granulomatous disease. In the present study,A. fumigatus-produced mycotoxins (fumagillin, gliotoxin [GT], and helvolic acid) are examined for their effects on the NADPH oxidase activity in human PMN. Of these mycotoxins, only GT significantly and stoichiometrically inhibits phorbol myristate acetate (PMA)-stimulated O2−generation, while the other two toxins are ineffective. The inhibition is dependent on the disulfide bridge of GT, which interferes with oxidase activation but not catalysis of the activated oxidase. Specifically, GT inhibits PMA-stimulated events: p47phoxphosphorylation, its incorporation into the cytoskeleton, and the membrane translocation of p67phox, p47phox, and p40phox, which are crucial steps in the assembly of the active NADPH oxidase. Thus, damage to p47phoxphosphorylation is likely a key to inhibiting NADPH oxidase activation. GT does not inhibit the membrane translocation of Rac2. The inhibition of p47phoxphosphorylation is due to the defective membrane translocation of protein kinase C (PKC) βII rather than an effect of GT on PKC βII activity, suggesting a failure of PKC βII to associate with the substrate, p47phox, on the membrane. These results suggest thatA. fumigatusmay confront PMN by inhibiting the assembly of the NADPH oxidase with its hyphal product, GT.
Mitogenicity of the Recombinant Mycobacterial 27-Kilodalton Lipoprotein Is Not Connected to Its Antiprotective Effect
Authors: Hovav Avi-Hai , Davidovitch Liuba , Nussbaum Gabriel , Mullerad Jacob , Fishman Yolanta , Bercovier Herve
Published: May 2004

We reported previously that even though immunization with the recombinant mycobacterial 27-kDa lipoprotein (r27) induced a Th1-type response in mice, the vaccinated mice became more susceptible to challenge withMycobacterium tuberculosis. In this study we show that r27 stimulates naive splenocytes to proliferate. Acylation of r27 was crucial for this effect, since a nonacylated mutant of r27, termed r27ΔSP, failed to stimulate splenocytes either in vitro or in vivo. Depletion experiments indicated that only B cells were proliferating in a T-cell-independent manner. We also found that r27 is recognized by TLR2, which is involved in mitogenic stimulation. Interestingly, r27 but not r27ΔSP induced high gamma interferon levels in splenocyte supernatants, whereas no significant interleukin-2 levels were detected. Since B-cell polyclonal activation might aggravate pathogen infection, we asked whether the antiprotective effect of the r27 lipoprotein is associated with its mitogenicity. We showed that, as in the case of r27, immunization of mice with the nonmitogenic r27ΔSP lipoprotein resulted in increasedM. tuberculosismultiplication. We conclude that the antiprotective effect of the r27 lipoprotein must be linked to properties of the polypeptide portion of the lipoprotein rather than to its lipid moiety and its mitogenicity.
Association of Type 2 Cytokines with Hepatic Fibrosis in HumanSchistosoma mansoniInfection
Authors: Ribeiro de Jesus Amélia , Magalhães Andréa , Gonzalez Miranda Delfin , Gonzalez Miranda Roberval , Araújo Maria Ilma , Almeida de Jesus Adriana , Silva Angela , Santana Luciana B. , Pearce Edward , Carvalho Edgar M.
Published: May 2004

The objective of this study was to evaluate the role of cytokines in hepatic fibrosis in the prehepatosplenic and early hepatosplenic stages of schistosomiasis mansoni. Hepatic fibrosis was classified by ultrasonography of 94 patients. Immunological evaluation was performed by the measurement of secreted cytokines (interleukin-5 [IL-5], IL-10, IL-13, gamma interferon, tumor necrosis factor alpha, and transforming growth factor β) in peripheral blood mononuclear cells (PBMC) stimulated bySchistosoma mansoniantigens. Significantly, higher levels of IL-5, IL-10, and IL-13 were found in supernatants of soluble egg antigen-stimulated PBMC from subjects with degree III hepatic fibrosis compared to patients with degree I or II fibrosis. Significant increases in IL-5 and IL-13 levels were also observed in some of the subjects who remained untreated for 1 year following initial assessment and developed more serious fibrosis during this period. The data suggest a role for type 2 cytokines in hepatic fibrosis in human schistosomiasis mansoni.
Characterization of theicmHandicmFGenes Required forLegionella pneumophilaIntracellular Growth, Genes That Are Present in Many Bacteria Associated with Eukaryotic Cells
Authors: Zusman Tal , Feldman Michal , Halperin Einat , Segal Gil
Published: May 2004

Legionella pneumophila, the causative agent of Legionnaires' disease, replicates intracellularly within a specialized phagosome of mammalian and protozoan host cells, and the Icm/Dot type IV secretion system has been shown to be essential for this process. Unlike all the other known Icm/Dot proteins, the IcmF protein, which was described before, and the IcmH protein, which is characterized here, have homologous proteins in many bacteria (such asYersinia pestis,Salmonella enterica,Rhizobium leguminosarum, andVibrio cholerae), all of which associate with eukaryotic cells. Here, we have characterized theL. pneumophila icmHandicmFgenes and found that both genes are present in 16 differentLegionellaspecies examined. TheicmHandicmFgenes were found to be absolutely required for intracellular multiplication inAcanthamoeba castellaniiand partially required for intracellular growth in HL-60-derived human macrophages, for immediate cytotoxicity, and for salt sensitivity. Mutagenesis of the predicted ATP/GTP binding site of IcmF revealed that the site is partially required for intracellular growth inA. castellanii. Analysis of the regulatory region of theicmHandicmFgenes, which were found to be cotranscribed, revealed that it contains at least two regulatory elements. In addition, anicmH::lacZfusion was shown to be activated during stationary phase in a LetA- and RelA-dependent manner. Our results indicate that although theicmHandicmFgenes probably have a different evolutionary origin than the rest of theicm/dotgenes, they are part of theicm/dotsystem and are required forL. pneumophilapathogenesis.
A Cardiac Myosin-Specific Autoimmune Response Is Induced by Immunization withTrypanosoma cruziProteins
Authors: Leon Juan S. , Daniels Melvin D. , Toriello Krista M. , Wang Kegiang , Engman David M.
Published: May 2004

Trypanosoma cruziis the protozoan parasite that causes Chagas' heart disease, a potentially fatal cardiomyopathy prevalent in Central and South America. Infection withT. cruziinduces cardiac myosin autoimmunity in susceptible humans and mice, and this autoimmunity has been suggested to contribute to cardiac inflammation. To address howT. cruziinduces cardiac myosin autoimmunity, we investigated whether immunity toT. cruziantigens could induce cardiac myosin-specific autoimmunity in the absence of live parasites. We immunized A/J mice with aT. cruziBrazil-derived protein extract emulsified in complete Freund's adjuvant and found that these mice developed cardiac myosin-specific delayed-type hypersensitivity (DTH) and autoantibodies in the absence of detectable cardiac damage. The induction of autoimmunity was specific since immunization with extracts of the related protozoan parasiteLeishmania amazonensisdid not induce myosin autoimmunity. The immunogenetic makeup of the host was important for this response, since C57BL/6 mice did not develop cardiac myosin DTH upon immunization withT. cruziextract. Perhaps more interesting, mice immunized with cardiac myosin developedT. cruzi-specific DTH and antibodies. This DTH was also antigen specific, since immunization with skeletal myosin and myoglobin did not induceT. cruzi-specific immunity. These results suggest that immunization with cardiac myosin orT. cruziantigen can induce specific, bidirectionally cross-reactive immune responses in the absence of detectable cardiac damage.
A Novel Lectin, DltA, Is Required for Expression of a Full Serum Resistance Phenotype inHaemophilus ducreyi
Authors: Leduc Isabelle , Richards Patricia , Davis Crystal , Schilling Birgit , Elkins Christopher
Published: May 2004

Haemophilus ducreyi, the causative agent of chancroid, is highly resistant to the complement-mediated bactericidal activity of normal human serum (NHS). Previously, we identified DsrA (for ducreyi serum resistance A), a major factor required for expression of the serum resistance phenotype inH. ducreyi. We describe here a second outer membrane protein, DltA (for ducreyi lectin A), which also contributes to serum resistance inH. ducreyi. IsogenicdltAmutants, constructed in 35000HP wild-type and FX517dsrAbackgrounds, were more susceptible to the bactericidal effects of NHS than each respective parent, demonstrating the additive effect of the mutations. Furthermore, expression ofdltAinH. influenzaestrain Rd rendered this highly susceptible strain partially resistant to 5% NHS compared to a vector-control strain. Although primary basic local alignment search tool analysis of thedltAopen reading frame revealed no close bacterial homologue, similarity to the β-chain of the eukaryotic lectin ricin was noted. DltA shares highly conserved structural motifs with the ricin β chain, such as cysteines and lectin-binding domains. To determine whetherdltAwas a lectin, ligand blots and affinity chromatography experiments were performed. DltA was affinity purified on immobilized lactose andN-acetylgalactosamine, and N-glycosylated but not glycosidase-treated model glycoproteins bound DltA. These data indicate that DltA is a lectin with specificity for lactose-related carbohydrates (CHO) and is important forH. ducreyiserum resistance.
Heterogeneity amongHelicobacter pyloriStrains in Expression of the Outer Membrane Protein BabA
Authors: Hennig Ewa E. , Mernaugh Ray , Edl Jennifer , Cao Ping , Cover Timothy L.
Published: May 2004

The BabA adhesin ofHelicobacter pyloriis an outer membrane protein that binds to the fucosylated Lewis b histo-blood group antigen on the surface of gastric epithelial cells. We screened a phage-displayed ScFv (single-chain fragment variable) recombinant antibody library for antibodies reactive with a recombinant BabA fragment and identified two such antibodies. Each antibody recognized an ∼75-kDa protein present in wild-typeH. pyloristrain J99 but absent from an isogenicbabAmutant strain. An immunoreactive BabA protein was detected by at least one of the antibodies in 18 (46%) of 39 different wild-typeH. pyloristrains and was detected more commonly incagA-positive strains than incagA-negative strains. Numerous amino acid polymorphisms were detected among BabA proteins expressed by different strains, with the greatest diversity occurring in the middle region of the proteins. Among the 18 strains that expressed a detectable BabA protein, there was considerable variation in the level of binding to Lewis b in vitro. Heterogeneity amongH. pyloristrains in expression of the BabA protein may be a factor that contributes to differing clinical outcomes amongH. pylori-infected humans.
A Heptosyltransferase Mutant of
Pasteurella multocida
Produces a Truncated Lipopolysaccharide Structure and Is Attenuated in Virulence
Authors: Harper Marina , Cox Andrew D. , St. Michael Frank , Wilkie Ian W. , Boyce John D. , Adler Ben
Published: May 2004

Pasteurella multocida
is the causative agent of fowl cholera in birds. In a previous study using signature-tagged mutagenesis, we identified a mutant, AL251, which was attenuated for virulence in mice and in the natural chicken host. Sequence analysis indicated that AL251 had an insertional inactivation of the gene

waaQ
PM

, encoding a putative heptosyl transferase, required for the addition of heptose to lipopolysaccharide (LPS) (M. Harper, J. D. Boyce, I. W. Wilkie, and B. Adler, Infect. Immun. 71:5440-5446, 2003). In the present study, using mass spectrometry and nuclear magnetic resonance, we have confirmed the identity of the enzyme encoded by

waaQ
PM

as a heptosyl transferase III and demonstrated that the predominant LPS glycoforms isolated from this mutant are severely truncated. Complementation experiments demonstrated that providing a functional

waaQ
PM

gene in
trans
can restore both the LPS to its full length and growth in mice to wild-type levels. Furthermore, we have shown that mutant AL251 is unable to cause fowl cholera in chickens and that the attenuation observed is not due to increased serum sensitivity.
Interaction ofBlastomyces dermatitidis,Sporothrix schenckii, andHistoplasma capsulatumwithAcanthamoeba castellanii
Authors: Steenbergen Judith N. , Nosanchuk Joshua D. , Malliaris Stephanie D. , Casadevall Arturo
Published: May 2004

Several dimorphic fungi are important human pathogens, but the origin and maintenance of virulence in these organisms is enigmatic, since an interaction with a mammalian host is not a requisite for fungal survival. Recently,Cryptococcus neoformanswas shown to interact with macrophages, slime molds, and amoebae in a similar manner, suggesting that fungal pathogenic strategies may arise from environmental interactions with phagocytic microorganisms. In this study, we examined the interactions of three dimorphic fungi with the soil amoebaAcanthameobae castellanii. Yeast forms ofBlastomyces dermatitidis,Sporothrix schenckii, andHistoplasma capsulatumwere each ingested by amoebae and macrophages, and phagocytosis of yeast cells resulted in amoeba death and fungal growth.H. capsulatumconidia were also cytotoxic to amoebae. For each fungal species, exposure of yeast cells to amoebae resulted in an increase in hyphal cells. Exposure of an avirulent laboratory strain ofH. capsulatumtoA. castellaniiselected for, or induced, a phenotype ofH. capsulatumthat caused a persistent murine lung infection. These results are consistent with the view that soil amoebae may contribute to the selection and maintenance of certain traits in pathogenic dimorphic fungi that confer on these microbes the capacity for virulence in mammals.
Somatic Hypermutation and Diverse Immunoglobulin Gene Usage in the Human Antibody Response to the Capsular Polysaccharide of Streptococcus pneumoniaeType 6B
Authors: Zhou Jianhui , Lottenbach Kathleen R. , Barenkamp Stephen J. , Reason Donald C.
Published: May 2004

Combinatorial cloning and expression library analysis were used to determine the expressed human antibody repertoire specific for the capsular polysaccharide (PS) ofStreptococcus pneumoniaeserotype 6B. Sequence analysis of 55 6B-specific antibody Fab fragments isolated from six vaccinated donors reveal that different individuals used a variety of heavy and light chain germ line variable (V) region genes to form pneumococcal capsular PS (PPS) 6B-specific paratopes. Within each donor, however, the response was more restricted, with five of the six donors using at most one or two gene pairs to form combining sites. Analysis also indicated that although the response in each donor was oligoclonal in terms of variable gene usage, the combination of extensive somatic hypermutation, deletion of germ line-encoded residues, insertion of non-germ line-encoded residues, and intraclonal isotype switching generated a surprising degree of paratope diversity within the individuals analyzed. In contrast to previously studied PS-specific responses, we find that the PPS 6B repertoire makes use of a diverse collection of heavy-chain and light-chain V region gene products to form specific paratopes, with no apparent tendency for conservation of immunoglobulin gene usage between individuals.
Specific In Vivo Deletion of B-Cell Subpopulations Expressing Human Immunoglobulins by the B-Cell Superantigen Protein L
Authors: Viau Muriel , Longo Nancy S. , Lipsky Peter E. , Björck Lars , Zouali Moncef
Published: May 2004

Some pathogens have evolved to produce proteins, called B-cell superantigens, that can interact with human immunoglobulin variable regions, independently of the combining site, and activate B lymphocytes that express the target immunoglobulins. However, the in vivo consequences of these interactions on human B-cell numbers and function are largely unknown. Using transgenic mice expressing fully human immunoglobulins, we studied the consequences of in vivo exposure of protein L ofPeptostreptococcus magnuswith human immunoglobulins. In the mature pool of B cells, protein L exposure resulted in a specific reduction of splenic marginal-zone B cells and peritoneal B-1 cells. Splenic B cells exhibited a skewed light-chain repertoire consistent with the capacity of protein L to bind specific kappa gene products. Remarkably, these two B-cell subsets are implicated in innate B-cell immunity, allowing rapid clearance of pathogens. Thus, the present study reveals a novel mechanism that may be used by some infectious agents to subvert a first line of the host's immune defense.
Role of CD8
+
and CD4
+
T Lymphocytes in Jejunal Mucosal Injury during Murine Giardiasis
Authors: Scott Kevin G.-E. , Yu Linda C. H. , Buret André G.
Published: May 2004

T-cell-mediated pathogenesis has been documented in various idiopathic and microbially induced intestinal disorders. Diffuse microvillous shortening seen in giardiasis is responsible for disaccharidase insufficiencies and malabsorption of electrolytes, nutrients, and water. Other mucosal changes include crypt hyperplasia and increased numbers of intraepithelial lymphocytes (IEL). A recent report using an athymic mouse model of infection showed that these epithelial injuries were dependent on T cells. The aim of the present study was to identify which subset of superior mesenteric lymph node (SMLN) T cells were responsible for mucosal alterations in giardiasis. CD4
+
and CD8
+
T cells, as well as whole lymphocyte populations, were isolated from SMLN of
Giardia muris
-infected mice for adoptive transfer. Jejunal segments of recipient mice were assessed for brush border ultrastructure, sucrase activity, crypt/villus ratio, and IEL numbers. Mice that received enriched CD8
+
and whole SMLN lymphocytes, but not CD4
+
T cells, from infected donors showed diffuse shortening of microvilli, loss of brush border surface area, impaired sucrase activity, and increased crypt/villus ratios compared to respective controls. Transfer of whole SMLN lymphocytes, as well as enriched CD4
+
or CD8
+
T cells, from infected donors led to increased IEL numbers in the recipient jejunum. The findings indicate that loss of intestinal brush border surface area, reduced disaccharidase activities, and increased crypt/villus ratios in giardiasis are mediated by CD8
+
T cells, whereas both CD8
+
and CD4
+
SMLN T cells regulate the influx of IEL.
Helicobacter pyloriActivates the Early Growth Response 1 Protein in Gastric Epithelial Cells
Authors: Abdel-Latif M. M. M. , Windle H. J. , Fitzgerald K. A. , Ang Y. S. , Eidhin D. Ní , Li-Weber M. , Sabra K. , Kelleher D.
Published: May 2004

The early growth response 1 (Egr-1) transcription factor is rapidly induced by various stimuli and is implicated in the regulation of cell growth, differentiation, and gene expression. The aim of this study was to examine the effect ofHelicobacter pylorion the expression of Egr-1 and Egr-1-regulated genes in gastric epithelial AGS cells. Egr-1 expression was assayed by immunoblotting and electrophoretic mobility shift assays usingH. pylori-stimulated AGS cells. Transient transfection experiments with promoter-reporter constructs of CD44, ICAM-1, and CD95L were used for expression studies.H. pyloriinduced the expression of Egr-1 in gastric epithelial cell lines in a dose-dependent manner, with the rapid kinetics that are typical of this class of transcription factors. Immunohistochemical studies of biopsies revealed that Egr-1 expression is more abundant inH. pylori-positive patients than in uninfected individuals. Reporter-promoter transfection studies indicated that Egr-1 binding is required for theH. pylori-induced transcriptional promoter activity of the CD44, ICAM-1, and CD95L (APO-1/Fas) constructs. The blocking ofegr-1with an antisense sequence preventedH. pylori-induced Egr-1 and CD44 protein expression. The MEK1/2 signaling cascade participates inH. pylori-mediated Egr-1 expression, but the p38 pathway does not. The data indicate thatH. pyloriinduces Egr-1 expression in AGS cells in vitro and that the Egr-1 protein is readily detectable in biopsies fromH. pylori-positive subjects. These observations suggest thatH. pylori-associated Egr-1 expression may play a role, in part, inH. pylori-induced pathology.
Protective Role of Interleukin-6 duringYersinia enterocoliticaInfection Is Mediated through the Modulation of Inflammatory Cytokines
Authors: Dube Peter H. , Handley Scott A. , Lewis James , Miller Virginia L.
Published: May 2004

Yersinia enterocoliticais a gram-negative enteric pathogen responsible for a number of gastrointestinal disorders. A striking feature of the pathology of aY. enterocoliticainfection is inflammation. Recently, we demonstrated a role for interleukin-1α (IL-1α) in the establishment of intestinal inflammation in response to aY. enterocoliticainfection. A cytokine directly affected by IL-1 levels is IL-6. A previous report suggested that IL-6 plays an anti-inflammatory role duringY. enterocoliticainfection, and in other systems IL-6 has been shown to be proinflammatory. Therefore, a closer examination of the roles of IL-6 and inflammatory cytokines in the control ofY. enterocoliticainfection in IL-6−/−mice was undertaken.Y. enterocoliticaorganisms were more virulent in the IL-6−/−mice (60-fold decreased 50% lethal dose) and colonized systemic tissues more rapidly and to a higher level than in the wild-type mice. One role of IL-6 during aY. enterocoliticainfection may be the downmodulation of the inflammatory response. The IL-6−/−mice have a more robust TH1 T-cell response, as well as hyperinflammatory pathologies. These phenotypes appear to be due to the misregulation of tumor necrosis factor alpha, monocyte chemotactic protein 1, IL-10, transforming growth factor β1, and gamma interferon in the IL-6−/−mouse. These data provide further insight into the intricate cytokine signaling pathways involved in the regulation of inflammatory responses and the control of bacterial infections.
Infection withToxoplasma gondiiIncreases Atherosclerotic Lesion in ApoE-Deficient Mice
Authors: Portugal Luciane R. , Fernandes Luciana R. , Cesar Giovana C. , Santiago Helton C. , Oliveira Dirce R. , Silva Neide M. , Silva Andrea A. , Lannes-Vieira Joseli , Arantes Rosa M. E. , Gazzinelli Ricardo T. , Alvarez-Leite Jacqueline I.
Published: May 2004

Toxoplasma gondiiis an intracellular protozoan that elicits a potent inflammatory response during the acute phase of infection. Herein, we evaluate whetherT. gondiiinfection alters the natural course of aortic lesions. ApoE knockout mice were infected withT. gondii, and at 5 weeks of infection, serum, feces, and liver cholesterol; aortic lesion size, cellularity, and inflammatory cytokines; and levels of serum nitrite and gamma interferon (IFN-γ) were analyzed. Our results showed that serum cholesterol and atherogenic lipoproteins were reduced afterT. gondiiinfection. The reduction of serum levels of total cholesterol and atherogenic lipoproteins was associated with increases in the aortic lesion area, numbers of inflammatory cells, and expression of monocyte chemoattractant protein 1 and inducible nitric oxide synthase mRNA in the site of lesions as well as elevated concentrations of IFN-γ and nitrite in sera ofT. gondii-infected animals. These results suggest that infection withT. gondiiaccelerates atherosclerotic development by stimulating the proinflammatory response and oxidative stress, thereby increasing the area of aortic lesion.
TheVibrio choleraeToxR-Regulated Porin OmpU Confers Resistance to Antimicrobial Peptides
Authors: Mathur Jyoti , Waldor Matthew K.
Published: May 2004

BPI (bactericidal/permeability-increasing) is a potent antimicrobial protein that was recently reported to be expressed as a surface protein on human gastrointestinal tract epithelial cells. In this study, we investigated the resistance ofVibrio cholerae, a small-bowel pathogen that causes cholera, to a BPI-derived peptide, P2. Unlike inEscherichia coliandSalmonella entericaserovar Typhimurium, resistance to P2 inV. choleraewas not dependent on the BipA GTPase. Instead, we found that ToxR, the master regulator ofV. choleraepathogenicity, controlled resistance to P2 by regulating the production of the outer membrane protein OmpU. BothtoxRandompUmutants were at least 100-fold more sensitive to P2 than were wild-type cells. OmpU also conferred resistance to polymyxin B sulfate, suggesting that this porin may impart resistance to cationic antibacterial proteins via a common mechanism. Studies of stationary-phase cells revealed that the ToxR-repressed porin OmpT may also contribute to P2 resistance. Finally, although the mechanism of porin-mediated resistance to antimicrobial peptides remains elusive, our data suggest that the BPI peptide sensitivity of OmpU-deficientV. choleraeis not attributable to a generally defective outer membrane.
Role of HtrA in the Virulence and Competence of
Streptococcus pneumoniae
Authors: Ibrahim Yasser Musa , Kerr Alison R. , McCluskey Jackie , Mitchell Tim J.
Published: May 2004

HtrA is a major virulence factor of
Streptococcus pneumoniae
(the pneumococcus). Deletion of the gene for HtrA from strain D39 of the pneumococcus completely abolished its virulence in mouse models of pneumonia and bacteremia, while the virulence of a second strain (TIGR4) was dramatically reduced. HtrA-negative mutants induced much less inflammation in the lungs during pneumonia than the wild type. HtrA is involved in the ability of the pneumococcus to grow at high temperatures, to resist oxidative stress, and to undergo genetic transformation. The expression and cellular location of several known virulence factors of the pneumococcus were not affected by the lack of HtrA.
Legionella dumoffiiDjlA, a Member of the DnaJ Family, Is Required for Intracellular Growth
Authors: Ohnishi Hiroko , Mizunoe Yoshimitsu , Takade Akemi , Tanaka Yoshitaka , Miyamoto Hiroshi , Harada Mine , Yoshida Shin-ichi
Published: May 2004

Legionella dumoffiiis one of the common causes of Legionnaires' disease and is capable of replicating in macrophages. To understand the mechanism of survival within macrophages, transposon mutagenesis was employed to isolate the genes necessary for intracellular growth. We identified four defective mutants after screening 790 transposon insertion mutants. Two transposon insertions were in genes homologous toicmBordotC, withindot/icmloci, required for intracellular multiplication ofL. pneumophila. The third was in a gene whose product is homologous to the 17-kDa antigen forming part of the VirB/VirD4 type IV secretion system ofBartonella henselae. The fourth was in thedjlA(for “dnaj-likeA”) gene. DjlA is a member of the DnaJ/Hsp40 family. Transcomplementation of thedjlAmutant restored the parental phenotype in J774 macrophages, A549 human alveolar epithelial cells, and the amoebaAcanthamoeba culbertsoni. Using confocal laser-scanning microscopy and transmission electron microscopy, we revealed that in contrast to the wild-type strain,L. dumoffii djlAmutant-containing phagosomes were unable to inhibit phagosome-lysosome fusion. Transmission electron microscopy also showed that in contrast to the virulent parental strain, thedjlAmutant was not able to recruit host cell rough endoplasmic reticulum. Furthermore, the stationary-phaseL. dumoffii djlAmutants were more susceptible to H2O2, high osmolarity, high temperature, and low pH than was their parental strain. These results indicate that DjlA is required for intracellular growth and organelle trafficking, as well as bacterial resistance to environmental stress. This is the first report demonstrating that a single DjlA-deficient mutant exhibits a distinct phenotype.
Identification of a Compensatory Mutant (
lpg2
−
REV
) of
Leishmania major
Able To Survive as Amastigotes within Macrophages without
LPG2
-Dependent Glycoconjugates and Its Significance to Virulence and Immunization Strategies
Authors: Späth Gerald F. , Lye Lon-Fye , Segawa Hiroaki , Turco Salvatore J. , Beverley Stephen M.
Published: May 2004

Different
Leishmania
species rely to different extents on abundant glycoconjugates, such as lipophosphoglycan (LPG) and related molecules, in mammalian infections. Previously, we showed that
Leishmania major
deletion mutants lacking the Golgi GDP-mannose transporter
LPG2
, which is required for assembly of the dominant phosphoglycan (PG) repeats of LPG, were unable to survive in macrophages. These
lpg2
−
mutants, however, retained the ability to generate asymptomatic, persistent infections in mice. In contrast, Ilg and colleagues showed that
Leishmania mexicana LPG2
mutants retained virulence for mice. Here we identified a partial revertant population of the
L. major lpg2
−
mutants (designated
lpg2
−
REV
) that had regained the ability to replicate in macrophages and induce disease pathology through a compensatory change. Like the
lpg2
parent, the
lpg2
−
REV
revertant was unable to synthesize
LPG2
-dependent PGs in the promastigote stage and thus remained highly attenuated in the ability to induce infection. However, after considerable delay
lpg2
−
REV
revertant-infected mice exhibited lesions, and amastigotes isolated from these lesions were able to replicate within macrophages despite the fact that they were unable to synthesize PGs. Thus, in some respects, the
lpg2
−
REV
amastigotes resemble
L. mexicana
amastigotes. Future studies of the gene(s) responsible may shed light on the mechanisms employed by
L. major
to survive in the absence of
LPG2
-dependent glycoconjugates and may also improve the potential of the
lpg2
−
L. major
line to serve as a live parasite vaccine by overcoming its tendency to revert toward virulence.
Contribution of Gelatinase, Serine Protease, and
fsr
to the Pathogenesis of
Enterococcus faecalis
Endophthalmitis
Authors: Engelbert Michael , Mylonakis Eleftherios , Ausubel Frederick M. , Calderwood Stephen B. , Gilmore Michael S.
Published: May 2004

Gelatinase and serine protease were found to contribute in concert to pathogenesis in a rabbit model of endophthalmitis. However, a mutant defective in the
fsr
regulator was observed to be more attenuated than a mutant rendered defective in the expression of gelatinase and serine protease as the result of a polar transposon insertion into the former. This increased attenuation suggests that there are possible additional pleiotropic effects of the defect in
fsr
on expression of traits contributing to the pathogenesis of enterococcal infection.
Induction of De Novo Subcortical Actin Filament Assembly by
Treponema denticola
Major Outer Sheath Protein
Authors: Amin Mohsen , Ho Andy C. S. , Lin Jenny Y. , Batista da Silva Andre Paes , Glogauer Michael , Ellen Richard P.
Published: May 2004

Treponema denticola
and its major outer sheath protein (Msp) induce actin reorganization in fibroblasts. We adapted a barbed-end labeling/imaging assay to monitor Msp-induced subcortical actin filament assembly in neutrophils and fibroblasts. Msp, at an actin-reorganizing concentration, inhibited migration of these dissimilar cell types, whose cytoskeletal functions in locomotion and phagocytosis are crucial for immunity and healing of peripheral infections.
Porphyromonas gingivalis
RgpA and Kgp Proteinases and Adhesins Are C Terminally Processed by the Carboxypeptidase CPG70
Authors: Veith Paul D. , Chen Yu-Yen , Reynolds Eric C.
Published: May 2004

Porphyromonas gingivalis
is a bacterial pathogen that produces the polyproteins RgpA and Kgp, which are proteolytically processed into proteinases and adhesins. We have demonstrated that the RgpA and Kgp proteinases and adhesins are C terminally processed by carboxypeptidase CPG70 by sequencing C-terminal peptides from both the wild type and an isogenic CPG70 mutant, using ion trap mass spectrometry.
Influence of Origin of Isolates, Especially Endocarditis Isolates, and Various Genes on Biofilm Formation by
Enterococcus faecalis
Authors: Mohamed Jamal A. , Huang Wenxiang , Nallapareddy Sreedhar R. , Teng Fang , Murray Barbara E.
Published: May 2004

Endocarditis isolates of
Enterococcus faecalis
produced biofilm significantly more often than nonendocarditis isolates, and 39% of 79 versus 6% of 84 isolates produced strong biofilm (
P
< 0.0001).
esp
was not required, but its presence was associated with higher amounts of biofilm (
P
< 0.001). Mutants disrupted in
dltA
,
efaA
,
ace
,
lsa
, and six two-component regulatory systems were largely unaltered, while disruptions in
epa
,
atn
,
gelE
, and
fsr
resulted in fewer attached bacteria, as determined using phase-contrast microscopy, and less biofilm (
P
< 0.0001).
Biological Properties of Staphylococcal Enterotoxin-Like Toxin Type R
Authors: Omoe Katsuhiko , Imanishi Ken'ichi , Hu Dong-Liang , Kato Hidehito , Takahashi-Omoe Hiromi , Nakane Akio , Uchiyama Takehiko , Shinagawa Kunihiro
Published: May 2004

We investigated the biological properties of a novel staphylococcal enterotoxin-like putative toxin, staphylococcal enterotoxin-like toxin type R (SElR). Major histocompatibility complex class II molecules were required for T-cell stimulation by SElR. SElR stimulated T cells bearing receptors Vβ 3, 11, 12, 13.2, and 14. These results suggested that SElR acts as a superantigen.
Role of
Streptococcus pyogenes
Two-Component Response Regulators in the Temporal Control of Mga and the Mga-Regulated Virulence Gene
emm
Authors: Ribardo Deborah A. , Lambert Thomas J. , McIver Kevin S.
Published: May 2004

We examined the role of
Streptococcus pyogenes
two-component response regulators (SptR) in expression of Mga and the Mga-regulated gene
emm
. Both serotype M6 and serotype M1 mutants in 12 of the 13 identified
sptR
genes exhibited levels of
emm
transcripts and Mga protein comparable to those of the wild type during exponential and stationary phases of growth. Thus, temporal control of these virulence genes does not require Spt response regulators.
Anaplasma phagocytophilumInfection Induces Protracted Neutrophil Degranulation
Authors: Choi Kyoung-seong , Grab Dennis J. , Dumler J. Stephen
Published: May 2004

Anaplasma phagocytophilum-infected neutrophil degranulation could exacerbate inflammation. Thus, the degranulation of infected neutrophils was assayed. Infected neutrophils expressed CD11b and CD66b, and supernatants of infected neutrophils showed more proMMP-9 and MMP-9 activity than controls and continued to do so for ≥18 h. Degranulation-related inflammatory tissue injury may account for some clinical manifestations in human granulocytic anaplasmosis.
Growth of
Piscirickettsia salmonis
to High Titers in Insect Tissue Culture Cells
Authors: Birkbeck T. Harry , Griffen Angela A. , Reid Helen I. , Laidler L. Anthony , Wadsworth Simon
Published: May 2004

Piscirickettsia salmonis
was grown in established insect, frog, and fish tissue culture cells. The yield of
P. salmonis
in Sf21 cells was up to 100 times that obtained in CHSE-214 cells, and virulence for Atlantic salmon was retained. The ceiling temperature for growth of
P. salmonis
in Sf21 cells was 24°C.
Travelling wave solutions to some PDEs of mathematical physics
Authors: Nozari Kourosh , Afrouzi Ghasem Alizadeh
Published: May 2004

Nonlinear operations such as multiplication of distributions are
not allowed in the classical theory of distributions. As a result,
some ambiguities arise when we want to solve nonlinear partial
differential equations such as differential equations of
elasticity and multifluid flows, or some new cosmological models
such as signature changing space‐times. Colombeau′s new theory of
generalized functions can be used to remove these ambiguities. In
this paper, we first consider a simplified model of elasticity and
multifluid flows in the framework of Colombeau′s theory and show
how one can handle such problems, investigate their jump conditions, and resolve their ambiguities. Then we consider as a
new proposal the case of cosmological models with signature
change and use Colombeau′s theory to solve Einstein equation for
the beginning of the Universe.
Reflection curves—new computation and rendering techniques
Authors: Ulmet Dan-Eugen
Published: May 2004

Reflection curves on surfaces are important tools for free‐form
surface interrogation. They are essential for industrial 3D
CAD/CAM systems and for rendering purposes. In this note, new
approaches regarding the computation and rendering of reflection
curves on surfaces are introduced. These approaches are designed
to take the advantage of the graphics libraries of recent releases of
commercial systems such as the OpenInventor toolkit (developed by
Silicon Graphics) or Matlab (developed by The Math Works). A new
relation between reflection curves and contour curves is derived;
this theoretical result is used for a straightforward Matlab
implementation of reflection curves. A new type of reflection
curves is also generated using the OpenInventor texture and
environment mapping implementations. This allows the computation,
rendering, and animation of reflection curves at interactive
rates, which makes it particularly useful for industrial
applications.
Derivations of quasi *‐algebras
Authors: Bagarello F. , Inoue A. , Trapani C.
Published: May 2004

The spatiality of derivations of quasi *‐algebras is
investigated by means of representation theory. Moreover, in view
of physical applications, the spatiality of the limit of a family
of spatial derivations is considered.
Optimal guaranteed cost filtering for Markovian jump discrete‐time systems
Authors: Mahmoud Magdi S. , Shi Peng
Published: May 2004

This paper develops a result on the design of robust steady‐state estimator for a class of uncertain discrete‐time systems with Markovian jump parameters. This result extends the steady‐state Kalman filter to the case of norm‐bounded time‐varying uncertainties in the state and measurement equations as well as jumping parameters. We derive a linear state estimator such that the estimation‐error covariance is guaranteed to lie within a certain bound for all admissible uncertainties. The solution is given in terms of a family of linear matrix inequalities (LMIs). A numerical example is included to illustrate the theory.
Maximizing the determinant for a special class of block‐partitioned matrices
Authors: Popescu Otilia , Rose Christopher , Popescu Dimitrie C.
Published: May 2004

An analytical solution is found for the maximum determinant of a
block‐partitioned class of matrices with constant trace for each
block. As an immediate application of this result, the maximum
determinant of a sum of Kronecker products is derived.
Sliding mode observers and observability singularity in chaotic synchronization
Authors: Boutat-Baddas L. , Barbot J. P. , Boutat D. , Tauleigne R.
Published: May 2004

We present a new secured data transmission based on a chaotic
synchronization and observability singularity. For this, we adopt
an approach based on an inclusion of the message in
the system structure and we use a sliding mode observer for system
with unknown input in order to recover the information. We end the
paper with an example of chaotic system with an observability
bifurcation. Moreover, this example highlights some benefits of the so‐called step‐by‐step sliding mode observer.
Stability analysis of periodically switched linear systems using Floquet theory
Authors: Gökçek Cevat
Published: May 2004

Stability of a switched system that consists of a set of linear
time invariant subsystems and a periodic switching rule is
investigated. Based on the Floquet theory, necessary and
sufficient conditions are given for exponential stability. It is
shown that there exists a slow switching rule that achieves
exponential stability if at least one of these subsystems is
asymptotically stable. It is also shown that there exists a fast
switching rule that achieves exponential stability if the average
of these subsystems is asymptotically stable. The results are
illustrated by examples.
Symmetries, variational principles, and quantum dynamics
Authors: Manjavidze J. , Sissakian A.
Published: May 2004

We describe the role of symmetries in formation of quantum dynamics.
A quantum version of d′Alembert′s principle is
proposed to take into account the symmetry constrains more exact.
It is argued that the time reversibility of quantum process, as
the quantum analogy of d′Alembert′s principle, makes the
measure of the corresponding path integral δ‐like. The
argument of this δ‐function is the sum of all classical
forces of the problem under consideration plus the random force
of quantum excitations. Such measure establishes the one‐to‐one
correspondence with classical mechanics and, for this reason,
allows a free choice of the useful dynamical variables. The
analysis shows that choosing the action‐angle variables, one may
get to the free‐from‐divergences quantum field theory. Moreover,
one can try to get an independence from necessity to extract the
degrees of freedom constrained by the symmetry. These properties
of new quantization scheme are vitally essential for such
theories as the non‐Abelian Yang‐Mills gauge theory and quantum
gravity.
Microscopic irreversibility
Authors: Gustafson Karl
Published: May 2004

First, I will recount the substance of several important
conversations I had with Ilya Prigogine over the years. There is
no doubt in my mind that Professor Prigogine firmly believed in
the underlying stochasticity of the universe. Second, I will
summarize my curiosity about the principle of detailed balance.
In my opinion, so far it has always been put in by hand. Third, I
will advance my own theory of microscopic irreversibility, that
is, irreversibility at the quantum level. This involves new
concepts of probability preference and probability violation. A
manifestation of this irreversibility may be seen during emission
of bound‐free photons during field‐matter interactions. Entropy
increase is tied to radiation increase, and the notion of heat
bath becomes light bath.
Generalized fermionic discrete Toda hierarchy
Authors: Gribanov V. V. , Kadyshevsky V. G. , Sorin A. S.
Published: May 2004

We describe bi‐Hamiltonian structure and Lax‐pair formulation with the
spectral parameter of the generalized fermionic Toda lattice
hierarchy as well as its bosonic and fermionic symmetries for
different (including periodic) boundary conditions.
Its two reductions N = 4 and N = 2 supersymmetric Toda lattice
hierarchies in different (including canonical) bases are
investigated. Its r‐matrix description, monodromy matrix, and
spectral curves are discussed.
On a kinetic model of the internet traffic
Authors: Antoniou I. , Ivanov Victor V. , Ivanov Valery V. , Kalinovsky Yu. L. , Zrelov P. V.
Published: May 2004

We present the modification of the Prigogine‐Herman kinetic
equation related to the network traffic. We discuss a solution of
this equation for homogeneous time‐independent situations and for
the lognormal desired speed distribution function, obtained from
the traffic measurements. This solution clearly shows two modes
corresponding to individual flow patterns (low
concentration mode) and to collective flow patterns
(traffic jam mode). For situations with low concentration, there
is almost a linear dependence of the information flow versus the
concentration and the higher the average speed the lower the
concentration at which the optimum flow takes place. When
approaching the critical concentration, there are no essential
differences in the flow for different average speeds, whereas for
the individual flow regions there are dramatic differences.
Relativity and irreversibility
Authors: Antoniou I. , Karpov E. , Prigogine I. , Pronko G.
Published: May 2004

The Lorentz transformation is extended to the decaying states in
a relativistic model of interacting fields. The nonlocal action
is defined beyond the Hilbert space. This shows that irreversible
extensions of dynamics of Poincaré nonintegrable systems are
compatible with relativity.
Spectral analysis for a class of integral‐difference operators:known facts, new results, and open problems
Authors: Melnikov Yuri B.
Published: May 2004

We present state of the art, the new results, and discuss open
problems in the field of spectral analysis for a class of
integral‐difference operators appearing in some nonequilibrium
statistical physics models as collision operators. The author
dedicates this work to the memory of Professor Ilya Prigogine,
who initiated this activity in 1997 and whose
interesting and most enlightening advices had gudided the author during all these years.