bluuebunny/crossref_metadata_2025_split huggingface dataset:
Differential Localization of Complement Component 3 within the Capsular Matrix ofCryptococcus neoformans
Authors: Gates Marcellene A. , Kozel Thomas R. 
Published: May 2006

ABSTRACTThe polysaccharide capsule ofCryptococcus neoformansis a powerful activator of the complement system. The goal of the present study was to assess serum and cellular variables that influence the sites for C3 binding within the capsular matrix. Confocal microscopy using fluorophore-labeled polyclonal anti-C3 and anticapsular monoclonal antibodies and rosetting of fluorescent microspheres coated with anti-C3 were used to identify sites of C3 binding relative to the capsular edge. The results showed that the source of serum was a major variable influencing localization of C3. C3 bound at or very near the capsular edge in the case of human serum. C3 deposition was further from the capsule edge with guinea pig and rat sera; in the case of mouse serum, there was no binding of C3 in the outer region of the capsule. Addition of human C3 to mouse serum led to deposition of the C3 at the capsular edge, indicating that distinct properties of mouse and human C3 account for the differential localization of C3. Finally, the density of the capsular matrix was an important variable in determining sites for C3 deposition. Yeast cells with a high concentration of polysaccharide near the capsule edge supported deposition of mouse C3 at or near the capsular edge, whereas cells with a low matrix density showed deposition well beneath the edge. Taken together, these results indicate that the spatial deposition of C3 within the capsular matrix is a complex process that is influenced by the serum source and the density of the capsular matrix.
Genetic Variation among Isolates of
Sarcocystis neurona
, the Agent of Protozoal Myeloencephalitis, as Revealed by Amplified Fragment Length Polymorphism Markers
Authors: Elsheikha H. M. , Schott H. C. , Mansfield L. S. 
Published: May 2006

ABSTRACT

Sarcocystis neurona
causes serious neurological disease in horses and other vertebrates in the Americas. Based on epidemiological data, this parasite has recently emerged. Here, the genetic diversity of
Sarcocystis neurona
was evaluated using the amplified fragment length polymorphism (AFLP) method. Fifteen
S. neurona
taxa from different regions collected over the last 10 years were used; six isolates were from clinically diseased horses, eight isolates were from wild-caught opossums (
Didelphis virginiana
), and one isolate was from a cowbird (
Molothrus ater
). Additionally, four outgroup taxa were also fingerprinted. Nine primer pairs were used to generate AFLP patterns, with a total number of amplified fragments ranging from 30 to 60, depending on the isolate and primers tested. Based on the presence/absence of amplified AFLP fragments and pairwise similarity values, all the
S. neurona
isolates tested were clustered in one monophyletic group. No significant correlation could be found between genomic similarity and host origin of the
S. neurona
isolates. AFLP revealed significant intraspecific genetic variations, and
S. neurona
appeared as a highly variable species. Furthermore, linkage disequilibrium analysis suggested that
S. neurona
populations within Michigan have an intermediate type of population structure that includes characteristics of both clonal and panamictic population structures. AFLP is a reliable molecular technique that has provided one of the most informative approaches to ascertain phylogenetic relationships in
S. neurona
and its closest relatives, allowing them to be clustered by relative similarity using band matching and unweighted pair group method with arithmetic mean analysis, which may be applicable to other related protozoal species.
CD4+CD25+Regulatory T Cells Modulate the T-Cell and Antibody Responses inHelicobacter-Infected BALB/c Mice
Authors: Kaparakis Maria , Laurie Karen L. , Wijburg Odilia , Pedersen John , Pearse Martin , van Driel Ian R. , Gleeson Paul A. , Strugnell Richard A. 
Published: May 2006

ABSTRACTGastricHelicobacterspp. induce chronic gastritis that may lead to ulceration and dysplasia. The host elicits a T helper 1 (Th1) response that is fundamental to the pathogenesis of these bacteria. We analyzed immune responses inHelicobacter-infected, normal mice depleted of CD4+CD25+T cells to investigate the in vivo role of regulatory T cells (Tregs) in the modulation ofHelicobacterimmunopathology. BALB/c and transgenic mice were depleted of CD4+CD25+T cells by administration of an anti-CD25 antibody either at the time of infection withHelicobacteror during chronic infection and gastritis. Depletion of CD25+Tregs prior to and during infection of mice withHelicobacterspp. did not affect either bacterial colonization or severity of gastritis. Depletion of CD25+Tregs was associated with increasedHelicobacter-specific antibody levels and an altered isotype distribution. Paragastric lymph node cells from CD25+Treg-depleted and control infected mice showed similar proliferation toHelicobacterantigens, but only cells from anti-CD25-treated animals secreted Th2 cytokines. CD25+Tregs do not control the level of gastritis induced by gastricHelicobacterspp. in normal, thymus-intact BALB/c mice. However, CD25+Tregs influence the cytokine and antibody responses induced by infection. Autoimmune gastritis is not induced inHelicobacter-infected mice depleted of CD25+Tregs but is induced in CD25+Treg-depleted mice, which have a higher frequency of autoreactive T cells.
Membrane Vesicles Shed byLegionella pneumophilaInhibit Fusion of Phagosomes with Lysosomes
Authors: Fernandez-Moreira Esteban , Helbig Juergen H. , Swanson Michele S. 
Published: May 2006

ABSTRACTWhen cultured in broth to the transmissive phase,Legionella pneumophilainfects macrophages by inhibiting phagosome maturation, whereas replicative-phase cells are transported to the lysosomes. Here we report that the ability ofL. pneumophilato inhibit phagosome-lysosome fusion correlated with developmentally regulated modifications of the pathogen's surface, as judged by its lipopolysaccharide profile and by its binding to a sialic acid-specific lectin and to the hydrocarbon hexadecane. Likewise, the composition of membrane vesicles shed byL. pneumophilawas developmentally regulated, based on binding to the lectin and to the lipopolysaccharide-specific monoclonal antibody 3/1. Membrane vesicles were sufficient to inhibit phagosome-lysosome fusion by a mechanism independent of type IV secretion, since only ∼25% of beads suspended with or coated by vesicles from transmissive phase wild type ordotAsecretion mutants colocalized with lysosomal probes, whereas ∼75% of beads were lysosomal when untreated or presented with vesicles from theL. pneumophila letAregulatory mutant orE. coli. As observed previously forL. pneumophilainfection of mouse macrophages, vesicles inhibited phagosome-lysosome fusion only temporarily; by 10 h after treatment with vesicles, macrophages delivered ∼72% of ingested beads to lysosomes. Accordingly, in the context of the epidemiology of the pneumonia Legionnaires' disease and virulence mechanisms ofLeishmaniaandMycobacteria, we discuss a model here in whichL. pneumophiladevelopmentally regulates its surface composition and releases vesicles into phagosomes that inhibit their fusion with lysosomes.
Attenuation and Persistence of and Ability To Induce Protective Immunity to a
Staphylococcus aureus aroA
Mutant in Mice
Authors: Buzzola Fernanda R. , Barbagelata María Sol , Caccuri Roberto L. , Sordelli Daniel O. 
Published: May 2006

ABSTRACT

Staphylococcus aureus
is the most important etiological agent of bovine mastitis, a disease that causes significant economic losses to the dairy industry. Several vaccines to prevent the disease have been tested, with limited success. The aim of this study was to obtain a suitable attenuated
aro
mutant of
S. aureus
by transposon mutagenesis and to demonstrate its efficacy as a live vaccine to induce protective immunity in a murine model of intramammary infection. To do this, we transformed
S. aureus
RN6390 with plasmid pTV1
ts
carrying Tn
917
. After screening of 3,493 erythromycin-resistant colonies, one mutant incapable of growing on plates lacking phenylalanine, tryptophan, and tyrosine was isolated and characterized. Molecular characterization of the mutant showed that the affected gene was
aroA
and that the insertion occurred 756 bp downstream of the
aroA
start codon. Complementation of the
aroA
mutant with a plasmid carrying
aroA
recovered the wild-type phenotype. The mutant exhibited a 50% lethal dose (1 × 10
6
CFU/mouse) higher than that of the parental strain (4.3 × 10
4
CFU/mouse). The
aroA
mutant showed decreased ability to persist in the lungs, spleens, and mammary glands of mice. Intramammary immunization with the
aroA
mutant stimulated both Th1 and Th2 responses in the mammary gland, as ascertained by reverse transcription-PCR, and induced significant protection from challenge with either the parental wild-type or a heterologous strain isolated from a cow with mastitis.
Development of Luminescent
Mycobacterium avium
subsp.
paratuberculosis
for Rapid Screening of Vaccine Candidates in Mice
Authors: Rosseels Valérie , Roupie Virginie , Zinniel Denise , Barletta Raúl G. , Huygen Kris 
Published: May 2006

ABSTRACT

Mycobacterium avium
subsp.
paratuberculosis
is a slowly growing mycobacterial species, requiring 6 to 8 weeks of culture before colonies can be counted visually. Here, we describe the development of luminescent
M. avium
subsp.
paratuberculosis
expressing
luxAB
genes of
Vibrio harveyi
and its use for vaccine testing in an experimental mouse model, replacing fastidious CFU counting by rapid luminometry.
Babesia microti
Primarily Invades Mature Erythrocytes in Mice
Authors: Borggraefe Ingo , Yuan Jie , Telford Sam R. , Menon Sanjay , Hunter Rouette , Shah Sohela , Spielman Andrew , Gelfand Jeffrey A. , Wortis Henry H. , Vannier Edouard 
Published: May 2006

ABSTRACT

Babesia microti
is a tick-borne red blood cell parasite that causes babesiosis in people. Its most common vertebrate reservoir is the white-footed mouse. To determine whether
B. microti
invades reticulocytes, as does the canine pathogen
B. gibsoni
, we infected the susceptible inbred mouse strains C.B-17.scid and DBA/2 with a clinical isolate of
B. microti
. Staining of fixed permeabilized red blood cells with 4′,6′-diamidino-2-phenylindole or YOYO-1, a sensitive nucleic acid stain, revealed parasite nuclei as large bright dots. Flow cytometric analysis indicated that parasite DNA is primarily found in mature erythrocytes that expressed
Babesia
antigens but not the transferrin receptor CD71. In contrast, CD71-positive reticulocytes rarely contained
Babesia
nuclei and failed to express
Babesia
antigens. Accordingly, the frequency of YOYO-1-positive, CD71-negative cells strongly correlated with parasitemia, defined as the frequency of infected red blood cells assessed on Giemsa-stained blood smears. Importantly, the absolute numbers generated by the two techniques were similar. Parasitemia was modest and transient in DBA/2 mice but intense and sustained in C.B-17.scid mice. In both strains, parasitemia preceded reticulocytosis, but reticulocytes remained refractory to
B. microti
. In immunocompetent C.B-17 mice, reticulocytosis developed early, despite a marginal and short-lived parasitemia. Likewise, an early reticulocytosis developed in resistant BALB/cBy and B10.D2 mice. These studies establish that
B. microti
has a tropism for mature erythrocytes. Although reticulocytes are rarely infected, the delayed reticulocytosis in susceptible strains may result from parasite or host activities to limit renewal of the mature erythrocyte pool, thereby preventing an overwhelming parasitemia.
Plasmodium falciparum-Infected Erythrocytes Increase Intercellular Adhesion Molecule 1 Expression on Brain Endothelium through NF-κB
Authors: Tripathi Abhai K. , Sullivan David J. , Stins Monique F. 
Published: May 2006

ABSTRACTSequestration ofPlasmodium falciparum-infected erythrocytes (Pf-IRBC) in postcapillary brain endothelium is a hallmark of cerebral malaria (CM) pathogenesis. There is a correlation between adherent Pf-IRBC and increased expression of intercellular cell adhesion molecule 1 (ICAM-1), which is also a receptor for Pf-IRBC on human brain microvascular endothelial cells (HBMEC). The underlying mechanism for the increased ICAM-1 expression has not been clearly defined. Therefore, we investigated the mechanisms of ICAM-1 expression on isolated HBMEC after exposure to Pf-IRBC. Ultrastructural characterization of the model confirmed that there was attachment through both Pf-IRBC knobs and HBMEC microvillus protrusions. Pf-IRBC induced a dose- and time-dependent increase in ICAM-1 expression on HBMEC that was specific for human brain endothelium and was not observed with human umbilical vein endothelium. Involvement of both membrane-associated Pf-IRBC proteins and parasite-derived soluble factors with the increase in ICAM-1 expression was demonstrated by surface trypsinization and fractionation. Pf-IRBC exposure induced nuclear translocation of NF-κB in HBMEC, which was linked to ICAM-1 expression, as shown by use of specific inhibitors of the transcription factor NF-κB and immunocytochemistry. In addition, inhibition of reactive oxygen species decreased Pf-IRBC-induced ICAM-1 expression on HBMEC. Parasite-induced ICAM-1 expression explains the localization of this molecule on brain endothelium in postmortem CM brain samples. By increasing ICAM-1 expression, Pf-IRBC may increase their sequestration, thereby perpetuating CM.
Organ-Specific Role of MyD88 for Gene Regulation during Polymicrobial Peritonitis
Authors: Weighardt Heike , Mages Jörg , Jusek Gabriela , Kaiser-Moore Simone , Lang Roland , Holzmann Bernhard 
Published: May 2006

ABSTRACT
Sepsis leads to the rapid induction of proinflammatory signaling cascades by activation of the innate immune system through Toll-like receptors (TLR). To characterize the role of TLR signaling through MyD88 for sepsis-induced transcriptional activation, we investigated gene expression during polymicrobial septic peritonitis by microarray analysis. Comparison of gene expression profiles for spleens and livers from septic wild-type and MyD88-deficient mice revealed striking organ-specific differences. Whereas MyD88 deficiency strongly reduced sepsis-induced gene expression in the liver, gene expression in the spleen was largely independent of MyD88, indicating organ-specific transcriptional regulation during polymicrobial sepsis. In addition to genes regulated by MyD88 in an organ-dependent manner, we also identified genes that exhibited an organ-independent influence of MyD88 and mostly encoded cytokines and chemokines. Notably, the expression of interferon (IFN)-regulated genes was markedly increased in septic MyD88-deficient mice compared to that in septic wild-type controls. Expression of IFN-regulated genes was dependent on the adapter protein TRIF. These results suggest that the influence of MyD88 on gene expression during sepsis strongly depends on the organ compartment affected by inflammation and that the lack of MyD88 may lead to disbalance of the expression of IFN-regulated genes.
Immunological and Molecular Characterization of Susceptibility in Relationship to Bacterial Strain Differences inMycobacterium aviumsubsp.paratuberculosisInfection in the Red Deer (Cervus elaphus)
Authors: O'Brien R. , Mackintosh C. G. , Bakker D. , Kopecna M. , Pavlik I. , Griffin J. F. T. 
Published: May 2006

ABSTRACTJohne's disease (JD) infection, caused byMycobacterium aviumsubsp.paratuberculosis, represents a major disease problem in farmed ruminants. Although JD has been well characterized in cattle and sheep, little is known of the infection dynamics or immunological response in deer. In this study, typing ofM. aviumsubsp.paratuberculosisisolates from intestinal lymphatic tissues from 74 JD-infected animals showed that clinical isolates ofM. aviumsubsp.paratuberculosisfrom New Zealand farmed red deer were exclusively of the bovine strain genotype. The susceptibility of deer toM. aviumsubsp.paratuberculosiswas further investigated by experimental oral-route infection studies using defined isolates of virulent bovine and ovineM. aviumsubsp.paratuberculosisstrains. Oral inoculation with high (109CFU/animal) or medium (107CFU/animal) doses of the bovine strain ofM. aviumsubsp.paratuberculosisestablished 100% infection rates, compared to 69% infection following inoculation with a medium dose of the ovine strain. The high susceptibility of deer to the bovine strain ofM. aviumsubsp.paratuberculosiswas confirmed by a 50% infection rate following experimental inoculation with a low dose of bacteria (103CFU/animal). This study is the first to report experimentalM. aviumsubsp.paratuberculosisinfection in red deer, and it outlines the strong infectivity of bovine-strainM. aviumsubsp.paratuberculosisisolates for cervines.
Staphylococcus aureus
Enterotoxin D Is Secreted in Milk and Stimulates Specific Antibody Responses in Cows in the Course of Experimental Intramammary Infection
Authors: Tollersrud Tore , Kampen Annette H. , Kenny Kevin 
Published: May 2006

ABSTRACT

An enterotoxin D (SED)-producing strain of
Staphylococcus aureus
was used to infect one mammary gland of each of 17 lactating dairy cows. All glands became infected and shed bacteria over a sampling period of 3 weeks. Serum and milk antibodies specific for SED were monitored by an enzyme-linked immunosorbent assay for 12 weeks. Elevated anti-SED antibodies were detected in all cows after infection, and immunoglobulin of the G2 subclass comprised most of the specific serum response. SED was detected in mastitic milk samples from two cows at levels of 5 to 10 ng/ml. An in vitro lymphocyte proliferation assay showed that SED at levels below 10 pg/ml induced proliferation of bovine lymphocytes and that sheep antiserum specific for SED neutralized this proliferative response. Sera obtained from the cows pre- and postinfection inhibited lymphocyte proliferation at SED concentrations of 10 and 50 ng/ml, respectively. The addition of SED to whole blood or to isolated neutrophils had no significant effect on neutrophil function in vitro. The results show that SED is secreted during mammary gland infection, is mitogenic for bovine lymphocytes, and stimulates the production of specific antibodies.
Isolation of a Human Monoclonal Antibody with Strong Neutralizing Activity against Diphtheria Toxin
Authors: Kakita Mai , Takahashi Tsuyoshi , Komiya Takako , Iba Yoshitaka , Tsuji Takao , Kurosawa Yoshikazu , Takahashi Motohide 
Published: May 2006

ABSTRACT

We isolated a human monoclonal antibody against diphtheria toxin (DT). It bound to fragment B with a binding activity (

K
d

) of 3.01 nM. The neutralizing activity assayed by the rabbit skin test was estimated to be 73,600 IU/g. This could be used as a therapeutic drug against DT in place of the traditional equine sera.
Flagellin-Independent Regulation of Chemokine Host Defense inCampylobacter jejuni-Infected Intestinal Epithelium
Authors: Johanesen Priscilla A. , Dwinell Michael B. 
Published: May 2006

ABSTRACTCampylobacter jejuniis a leading cause of bacterial food-borne diarrheal disease throughout the world and the most frequent antecedent of autoimmune neuropathy Guillain-Barré syndrome. While infection is associated with immune memory, little is known regarding the role of the epithelium in targeting dendritic cells (DC) for initiating the appropriate adaptive immune response toC. jejuni. The objective of this study was to define the role for the intestinal epithelium in the induction of the adaptive immune response inC. jejuniinfection by assessing the production of DC and T-cell chemoattractants. Human T84 epithelial cells were used as model intestinal epithelia. Infection of T84 cells withC. jejunidose- and time-dependently up-regulated DC and T-cell chemokine gene transcription and secretion. Induction required live bacteria and was in the physiologically relevant direction for attraction of mucosal immunocytes.C. jejuni-activated NF-κB signaling was shown to be essential for proinflammatory chemokine secretion. Notably,C. jejunisecretion occurred independently of flagellin identification by Toll-like receptor 5. Secretion of a DC chemoattractant by differing clinicalC. jejuniisolates suggested adherence/invasion were key virulence determinants of epithelial chemokine secretion. The regulated epithelial expression of DC and T-cell chemoattractants suggests a mechanism for the directed trafficking of immune cells required for the initiation of adaptive immunity in campylobacteriosis. Chemokine secretion occurs despiteCampylobacterevasion of the flagellin pattern recognition receptor, suggesting that alternate host defense strategies limit disease pathogenesis.
Differential Expression and Sequence Conservation of theAnaplasma marginale msp2Gene Superfamily Outer Membrane Proteins
Authors: Noh Susan M. , Brayton Kelly A. , Knowles Donald P. , Agnes Joseph T. , Dark Michael J. , Brown Wendy C. , Baszler Timothy V. , Palmer Guy H. 
Published: May 2006

ABSTRACTBacterial pathogens in the generaAnaplasmaandEhrlichiaencode a protein superfamily, pfam01617, which includes the predominant outer membrane proteins (OMPs) of each species, major surface protein 2 (MSP2) and MSP3 ofAnaplasma marginaleandAnaplasma ovis,Anaplasma phagocytophilumMSP2 (p44),Ehrlichia chaffeensisp28-OMP,Ehrlichia canisp30, andEhrlichia ruminantiumMAP1, and has been shown to be involved in both antigenic variation within the mammalian host and differential expression between the mammalian and arthropod hosts. Recently, complete sequencing of theA. marginalegenome has identified an expanded set of genes, designatedomp1-14, encoding new members of this superfamily. Transcriptional analysis indicated that, with the exception of the three smallest open reading frames,omp2,omp3, andomp6, these superfamily genes are transcribed inA. marginale-infected erythrocytes, tick midgut and salivary glands, and the IDE8 tick cell line. OMPs 1, 4, 7 to 9, and 11 were confirmed to be expressed as proteins byA. marginalewithin infected erythrocytes, with expression being either markedly lower (OMPs 1, 4, and 7 to 9) or absent (OMP11) in infected tick cells, which reflected regulation at the transcript level. Although the pfam01617 superfamily includes the antigenically variable MSP2 and MSP3 surface proteins, analysis of theomp1-14sequences throughout a cycle of acute and persistent infection in the mammalian host and tick transmission reveals a high degree of conservation, an observation supported by sequence comparisons between the St. Maries strain and Florida strain genomes.