bluuebunny/crossref_metadata_2025_split huggingface dataset:
Salmonella entericaSerovar Typhimurium-Induced Maturation of Bone Marrow-Derived Dendritic Cells
Authors: Svensson Mattias , Johansson Cecilia , Wick Mary Jo 
Published: July 2002

ABSTRACTMurine bone marrow-derived dendritic cells (DC) can phagocytose and processSalmonella entericaserovar Typhimurium for peptide presentation on major histocompatibility complex class I (MHC-I) and MHC-II molecules. To investigate if a serovar Typhimurium encounter with DC induces maturation and downregulates their ability to present antigens from subsequently encountered bacteria, DC were pulsed with serovar Typhimurium 24 h prior to coincubating withEscherichia coliexpressing the model antigen Crl-OVA. Quantitating presentation of OVA epitopes contained within Crl-OVA showed thatSalmonella-pulsed DC had a reduced capacity to process Crl-OVA-expressingE. colifor OVA(257-264)/Kband OVA(265-277)/I-Abpresentation. In addition, time course studies of DC pulsed with Crl-OVA-expressing serovar Typhimurium showed that OVA(257-264)/Kbcomplexes could stimulate CD8OVA T-hybridoma cells for <24 h following a bacterial pulse, while OVA(265-277)/I-Abcomplexes could stimulate OT4H T-hybridoma cells for >24 but <48 h. ThephoP-phoQvirulence locus of serovar Typhimurium also influenced the ability of DC to process Crl-OVA-expressing serovar Typhimurium for OVA(265-277)/I-Abpresentation but not for OVA(257-264)/Kbpresentation. Furthermore, pulsing of DC with serovar Typhimurium followed by incubation for 24 or 48 h altered surface expression of MHC-I, MHC-II, CD40, CD54, CD80, and CD86, generating a DC population with a uniform, high expression level of these molecules. Finally, neither the serovar TyphimuriumphoP-phoQlocus nor lipopolysaccharides (LPS) containing lipid A modifications purified fromphoPmutant strains had a different effect on DC maturation from that of wild-type serovar Typhimurium or purified wild-type LPS. Thus, these data show thatSalmonellaorSalmonellaLPS induces maturation of DC and that this process is not altered by theSalmonella phoPvirulence locus. However,phoPdid influence OVA(265-277)/I-Abpresentation by DC infected with Crl-OVA-expressing serovar Typhimurium when quantitated after 2 h of bacterial infection.
SclA, a Novel Collagen-Like Surface Protein ofStreptococcus pyogenes
Authors: Rasmussen Magnus , Edén Arvid , Björck Lars 
Published: July 2002

ABSTRACTSurface proteins ofStreptococcus pyogenesare important virulence factors. Here we describe a novel collagen-like surface protein, designated SclA (streptococcal collagen-like surface protein). ThesclAgene was identified in silico using the Streptococcal Genome Sequencing Project with the recently identified protein GRAB as the probe. SclA has a signal sequence and a cell wall attachment region containing the prototypic LPXTGX motif. The surface-exposed part of SclA contains a unique NH2-terminal domain of 73 amino acids, followed by a collagen-like region. ThesclAgene was found to be positively regulated by Mga, a transcriptional activator of severalS. pyogenesvirulence determinants. A mutant lacking cell wall-associated SclA was constructed and was found to be as effective as wild-type bacteria in platelet aggregation, survival in fresh human blood, and adherence to pharyngeal cells. ThesclAgene was found in all 12S. pyogenesstrains that were investigated using PCR. Sequence analysis revealed that the signal sequence and the cell wall attachment region are highly conserved. The collagen-like domain is variable in its NH2-terminal region and has conserved repeated domains in its COOH-terminal part. SclA proteins from most strains have additional proline-rich repeats spacing the collagen-like domain and the cell wall attachment sequence. The unique NH2-terminal region is hypervariable, but computer predictions indicate a common secondary structure, with two alpha helices connected by a loop region. Immune selection may explain the hypervariability in the NH2-terminal region, whereas the preserved secondary structure implies that this region has a common function. These features and the Mga regulation are shared with the M protein ofS. pyogenes. Moreover, as with the gene encoding the M protein, phylogenetic analysis indicates that horizontal gene transfer has contributed to the evolution ofsclA.
Identification oftgh-2, a Filarial Nematode Homolog ofCaenorhabditis elegans daf-7and Human Transforming Growth Factor β, Expressed in Microfilarial and Adult Stages ofBrugia malayi
Authors: Gomez-Escobar Natalia , Gregory William F. , Maizels Rick M. 
Published: July 2002

ABSTRACTA novel member of the transforming growth factor β (TGF-β) family has been identified in the filarial nematode parasiteBrugia malayiby searching the recently developed Expressed Sequence Tag (EST) database produced by the Filarial Genome Project. Designatedtgh-2, this new gene shows most similarity to a key product regulating dauer larva formation inCaenorhabditis elegans(DAF-7) and to the human down-modulatory cytokine TGF-β. Homology to DAF-7 extends throughout the length of the 349-amino-acid (aa) protein, which is divided into an N-terminal 237 aa, including a putative signal sequence, a 4-aa basic cleavage site, and a 108-aa C-terminal active domain. Similarity to human TGF-β is restricted to the C-terminal domain, over which there is a 32% identity between TGH-2 and TGF-β1, including every cysteine residue. Expression oftgh-2mRNA has been measured over the filarial life cycle. It is maximal in the microfilarial stage, with lower levels of activity around the time of molting within the mammal, but continues to be expressed by mature adult male and female parasites. Expression in both the microfilaria, which is in a state of arrested development, and the adult, which is terminally differentiated, indicates thattgh-2may play a role other than purely developmental. This is consistent with our observation that TGH-2 is secreted by adult worms in vitro. Recombinant TGH-2 expressed in baculovirus shows a low level of binding to TGF-β-receptor bearing mink lung epithelial cells (MELCs), which is partially inhibited (16 to 39%) with human TGF-β, and activates plasminogen activator inhibitor-1 transcription in MELCs, a marker for TGF-β-mediated transduction. Further tests will be required to establish whether the major role ofB. malayiTGH-2 (Bm-TGH-2) is to modulate the host immune response via the TGF-β pathway.
Micronemal Transport ofPlasmodiumOokinete Chitinases to the Electron-Dense Area of the Apical Complex for Extracellular Secretion
Authors: Langer Rebecca C. , Hayward Rhian E. , Tsuboi Takafumi , Tachibana Mayumi , Torii Motomi , Vinetz Joseph M. 
Published: July 2002

ABSTRACTPlasmodiumookinetes secrete chitinases to penetrate the acellular, chitin-containing peritrophic matrix of the mosquito midgut en route to invasion of the epithelium. Chitinases are potentially targets that can be used to block malaria transmission. We demonstrate here that chitinases ofPlasmodium falciparumandP. gallinaceumare concentrated at the apical end of ookinetes. The chitinase PgCHT1 ofP. gallinaceumis present within ookinete micronemes and subsequently becomes localized in the electron-dense area of the apical complex. These observations suggest a pathway by which ookinetes secrete proteins extracellularly.
Inhibition of
Chlamydia pneumoniae
Replication in Human Aortic Smooth Muscle Cells by Gamma Interferon-Induced Indoleamine 2,3-Dioxygenase Activity
Authors: Pantoja Laura G. , Miller Richard D. , Ramirez Julio A. , Molestina Robert E. , Summersgill James T. 
Published: July 2002

ABSTRACT

Infection with
Chlamydia pneumoniae
, a human respiratory pathogen, has been implicated as a potential risk factor in atherosclerosis, possibly because the pathogen can exist in a persistent form similar to that described for
Chlamydia trachomatis
. The present study investigated whether gamma interferon (IFN-γ) can induce indoleamine 2,3-dioxygenase (IDO) activity in aortic smooth muscle cells, leading to a marked inhibition of
C. pneumoniae
growth. Our data indicate a stimulation of IDO mRNA expression and dose-dependent enzymatic activity following IFN-γ treatment. IDO-mediated increase in tryptophan catabolism resulted in a dose-dependent marked inhibition of
C. pneumoniae
replication.
The Sequence-Variable, Single-Copy
tprK
Gene of
Treponema pallidum
Nichols Strain UNC and Street Strain 14 Encodes Heterogeneous TprK Proteins
Authors: Stamm Lola V. , Bergen Heather L. 
Published: July 2002

ABSTRACT

Syphilis is a chronic infection with early relapses that are hypothesized to result from the emergence of phenotypic variants of
Treponema pallidum
. Recent studies demonstrated that TprK, a target of protective immunity, is heterogeneous in several
T. pallidum
strains, but not in Nichols strain Seattle (A. Centurion-Lara, C. Godornes, C. Castro, W. C. Van Voorhis, and S. A. Lukehart, Infect. Immun. 68:824–831, 2000). Analysis of PCR-amplified
tprK
from Nichols strain UNC and Street strain 14 treponemes showed that TprK has seven regions of intrastrain heterogeneity resulting from amino acid substitutions, insertions, and deletions. In contrast, analysis of PCR-amplified
tprJ
showed little intrastrain or interstrain heterogeneity. Reverse transcriptase PCR analysis demonstrated that mRNA transcripts representing unique polymorphic TprK proteins are present during syphilitic infection. Southern hybridization confirmed that Nichols strain UNC and Street strain 14 each contain a single copy of
tprK
, indicating that intrastrain heterogeneity is due to the presence of multiple treponemal subpopulations which contain a variant form of
tprK
.
Multiple Mechanisms of Phase Variation of PorA in
Neisseria meningitidis
Authors: van der Ende Arie , Hopman Carla T. P. , Dankert Jacob 
Published: July 2002

ABSTRACT

Previously, we reported that PorA expression in
Neisseria meningitidis
is modulated by variation in the length of the homopolymeric tract of guanidine residues between the −35 and −10 regions of the promoter or by deletion of
porA
. To reveal additional mechanisms of variation in PorA expression, the meningococcal isolates from 41 patients and 19 carriers were studied. In addition, at least 3 meningococcal isolates from different body parts of each of 11 patients were analyzed. Sequence analysis of the
porA
promoter showed that the spacer between the −35 and −10 regions varies in length between 14 and 24 bp. PorA expression was observed in strains with a
porA
promoter spacer of 16 to 24 bp. All but one strain with a
porA
promoter spacer of 16 to 20 bp and undetectable PorA expression have a homopolymeric tract of 8 or 6 instead of 7 adenine residues in the
porA
coding region. The other PorA-negative strain had a single-base-pair deletion in the coding region. The highest level of PorA expression was observed in strains with a promoter spacer of 17 or 18 bp. PorA expression was reduced twofold in strains with a
porA
promoter spacer of 16 or 19 bp. Strains with a 16-bp promoter spacer with substitutions in the polyguanidine tract displayed increased levels of PorA expression compared to strains with a homopolymeric tract of guanidine residues in the
porA
promoter. In conclusion, meningococci display multiple mechanisms for varying PorA expression.
Characterization of Allelic Variation in the
Babesia bovis
Merozoite Surface Antigen 1 (MSA-1) Locus and Identification of a Cross-Reactive Inhibition-Sensitive MSA-1 Epitope
Authors: Suarez Carlos E. , Florin-Christensen Monica , Hines Stephen A. , Palmer Guy H. , Brown Wendy C. , McElwain Terry F. 
Published: July 2002

ABSTRACT

The
Babesia bovis
merozoite surface antigen 1 (MSA-1), a member of the variable merozoite surface antigen (VMSA) family, is an immunodominant glycoprotein which elicits antibodies that inhibit erythrocyte invasion. While antigenic polymorphism is a general feature of
vmsa
genes, the molecular basis and extent of
msa-1
sequence polymorphism have not been well characterized. In this study we defined the
msa-1
locus in the biologically cloned Mexico Mo7 strain of
B. bovis
and identified the sequence differences between MSA-1 antigenically dissimilar strains. We then determined whether sequences conserved between distinct
msa-1
alleles would induce cross-reactive CD4
+
T lymphocytes or inhibitory antibodies. The
msa-1
locus in Mo7 contains a single
msa-1
gene flanked by transcribed genes with no sequence homology to members of the VMSA gene family. Argentina
B. bovis
strains R1A and S2P have
msa-1
genes with amino acid sequences that are 98.8% identical to each other, and antibodies against S2P MSA-1 cross-react with native R1A MSA-1. In contrast, identity between the Argentina and Mexico Mo7
msa-1
alleles is only 52%, with no continuous stretch of identity longer than 16 amino acids. Despite limited sequence conservation, antibodies against R1A MSA-1 were able to inhibit invasion of erythrocytes by Mo7 merozoites. The results indicate that inhibition-sensitive epitopes are conserved despite significant sequence divergence between Mexico and Argentina strain alleles and support a conserved functional role for polymorphic MSA-1 in erythrocyte invasion.
Identification of Genes Present Specifically in a Virulent Strain of
Klebsiella pneumoniae
Authors: Lai Yi-Chyi , Yang Shu-Li , Peng Hwei-Ling , Chang Hwan-You 
Published: July 2002

ABSTRACT

Klebsiella pneumoniae
is a common cause of septicemia and urinary tract infections. The PCR-supported genomic subtractive hybridization was employed to identify genes specifically present in a virulent strain of
K. pneumoniae
. Analysis of 25 subtracted DNA clones has revealed 19 distinct nucleotide sequences. Two of the sequences were found to be the genes encoding the transposase of Tn
3926
and a capsule polysaccharide exporting enzyme. Three sequences displayed moderate homology with
bvgAS
, which encodes a two-component signal transduction system in
Bordetella pertussis
. The rest of the sequences did not exhibit homology with any known genes. The distribution of these novel sequences varied greatly in
K. pneumoniae
clinical isolates, reflecting the heterogeneous nature of the
K. pneumoniae
population.
Identification of Immunodominant Antigens from
Helicobacter pylori
and Evaluation of Their Reactivities with Sera from Patients with Different Gastroduodenal Pathologies
Authors: Kimmel Brigitte , Bosserhoff Armin , Frank Rainer , Gross Roy , Goebel Werner , Beier Dagmar 
Published: July 2002

ABSTRACT

Colonization of the gastric mucosa by
Helicobacter pylori
is the major cause of gastroduodenal pathologies in humans. Studying the outcome of the humoral immune response directed against this gastric pathogen may contribute substantially to vaccine development and to the improvement of diagnostic techniques based on serology. By using two-dimensional gel electrophoresis, 29 proteins from
H. pylori
G27 were identified which strongly react with sera derived from
H. pylori
-infected patients suffering from different gastroduodenal pathologies. These antigens were characterized by mass spectrometry and proved to correspond to products of open reading frames predicted by the
H. pylori
genome sequence. The comparison of the antigenic patterns recognized by these sera revealed no association of specific
H. pylori
antigens with antibodies in patients with particular gastroduodenal pathologies.
Phagocytosed
Bordetella pertussis
Fails To Survive in Human Neutrophils
Authors: Lenz Derrick H. , Weingart Christine L. , Weiss Alison A. 
Published: July 2002

ABSTRACT

Previous studies have reported that phagocytosed
Bordetella pertussis
survives in human neutrophils. This issue has been reexamined. Opsonized or unopsonized bacteria expressing green fluorescent protein (GFP) were incubated with adherent human neutrophils. Phagocytosis was quantified by fluorescence microscopy, and the viability of phagocytosed bacteria was determined by colony counts following treatment with polymyxin B to kill extracellular bacteria. Only 1 to 2% of the phagocytosed bacteria remained viable. Opsonization with heat-inactivated immune serum reduced the amount of attachment and phagocytosis of the bacteria but did not alter survival rates. In contrast to previous reports, these data suggest that phagocytosed
B. pertussis
bacteria are killed by human neutrophils.
Intranasal Immunization withToxoplasma gondiiSAG1 Induces Protective Cells into Both NALT and GALT Compartments
Authors: Velge-Roussel F. , Marcelo P. , Lepage A. C. , Buzoni-Gatel D. , Bout D. T. 
Published: July 2002

ABSTRACTIntranasal (i.n.) immunization with the SAG1 protein ofToxoplasma gondiiplus cholera toxin (CT) provides protective immunity. The aim of this study was to analyze the cellular activation of several mucosal compartments after i.n. immunization. Cervical and mesenteric lymph node (CLN and MLN, respectively) lymphoid cell and intraepithelial lymphocyte (IEL) passive transfer experiments were performed with CBA/J mice immunized i.n. with SAG1 plus CT. CLN and MLN cells and IEL isolated 42 days after immunization conferred protective immunity on naive recipient mice challenged with strain 76KT. gondii, as assessed by the reduction in the number of brain cysts. There were proliferative specific responses in nose-associated lymphoid tissue and the CLN and MLN cells from mice immunized with SAG1 plus CT, but no cytokine was detectable. Thus, protective immunity is associated with a specific cellular response in the nasal and mesenteric compartments after i.n. immunization.
Comparison of the Roles of Calcineurin in Physiology and Virulence in Serotype D and Serotype A Strains of
Cryptococcus neoformans
Authors: Cruz M. Cristina , Sia Rey A. L. , Olson Michael , Cox Gary M. , Heitman Joseph 
Published: July 2002

ABSTRACT

The calcineurin gene was cloned and disrupted in serotype D strains of
Cryptococcus neoformans
. Serotype A and serotype D calcineurin mutants were inviable at 37°C and avirulent in mice, whereas only serotype A mutants were cation stress sensitive. Thus, calcineurin plays conserved and divergent roles in serotype A and serotype D strains.
Actinobacillus pleuropneumoniaeIron Transport: a Set ofexbBDGenes Is Transcriptionally Linked to thetbpBGene and Required for Utilization of Transferrin-Bound Iron
Authors: Tonpitak Walaiporn , Thiede Svenja , Oswald Winfried , Baltes Nina , Gerlach Gerald-F. 
Published: July 2002

ABSTRACTUpon iron restriction,Actinobacillus pleuropneumoniaehas been shown to express the transferrin-binding proteins TbpB and TbpA, both of which have been implied to be important virulence factors. In order to identify additional iron-regulated proteins, we cloned and analyzed the region upstream of the transferrin-binding protein genes in anA. pleuropneumoniaeserotype 7 strain. We located immediately upstream of thetbpBgene two open reading frames which were 43% homologous to the neisserial ExbBD protein genes. By raising specific antibodies, we showed that ExbB is expressed under iron-limiting growth conditions only, and RT-PCR analysis revealed that theexbBDgenes and thetbpBgene are transcribed on a single polycistronic mRNA. By constructing an isogenic and nonpolarexbBDmutant, we showed that theexbBDgenes are required byA. pleuropneumoniaefor utilization of transferrin-bound iron. Using PCR and Western blotting, we showed that the genetic organization found inA. pleuropneumoniaeserotype 7 is similar in all 12A. pleuropneumoniaeserotype reference strains.
Influence of theBcgLocus on Natural Resistance to Primary Infection with the Facultative Intracellular BacteriumFrancisella tularensisin Mice
Authors: Kovářová Hana , Hernychová Lenka , Hajdúch Marián , Šírová M. , Macela Aleš 
Published: July 2002

ABSTRACTThe implication of theBcglocus in the control of natural resistance to infection with a live vaccine strain (LVS) of the intracellular pathogenFrancisella tularensiswas studied. Analysis of phenotypic expression of natural resistance and susceptibility was performed using mouse strains congenic at theBcglocus. Comparison of the kinetics of bacterial colonization of spleen showed that B10.A.Bcg(r)mice were extremely susceptible during early phases of primary sublethal infection, while their congenic C57BL/10N [Bcg(s)] counterparts could be classified as resistant toF. tularensisLVS infection according to the 2-log-lower bacterial CFU within the tissue as long as 5 days after infection. Different phenotypes ofBcgcongenic mice were associated with differential expression of the cytokines tumor necrosis factor alpha, interleukin-10, and gamma interferon and production of reactive oxygen intermediates. These results strongly suggest that theBcglocus, which is close or identical to theNramp1gene, controls natural resistance to infection byF. tularensisand that its effect is the opposite of that observed for otherBcg-controlled pathogens.
Lipopolysaccharides ofBrucella abortusandBrucella melitensisInduce Nitric Oxide Synthesis in Rat Peritoneal Macrophages
Authors: López-Urrutia Luis , Alonso Andrés , Nieto Maria Luisa , Bayón Yolanda , Orduña Antonio , Sánchez Crespo Mariano 
Published: July 2002

ABSTRACTSmooth lipopolysaccharide (S-LPS) and lipid A ofBrucella abortusandBrucella melitensisinduced the production of nitric oxide (NO) by rat adherent peritoneal cells, but they induced lower levels of production of NO thanEscherichia coliLPS. The participation of the inducible isoform of NO synthase (iNOS) was confirmed by the finding of an increased expression of both iNOS mRNA and iNOS protein. These observations might help to explain (i) the acute outcome ofBrucellainfection in rodents, (ii) the low frequency of septic shock in human brucellosis, and (iii) the prolonged intracellular survival ofBrucellain humans.
Comparison of the Immune Profile of Nonhealing Cutaneous Leishmaniasis Patients with Those with Active Lesions and Those Who Have Recovered from Infection
Authors: Ajdary Soheila , Alimohammadian Mohammad H. , Eslami Mohammad B. , Kemp Kaare , Kharazmi Arsalan 
Published: July 2002

ABSTRACTTh1-type cellular immune responses play a critical role in protection against infection withLeishmaniaparasites, whereas activation of Th2-type cells results in progressive disease. Cutaneous leishmaniasis caused byLeishmania majoris often a self-healing disease; however, persistent nonhealing forms are also known. In the present study, we have described cell-mediated immune responses in nonhealing patients by measuring T-cell proliferation, cytokine production, and phenotypic characterization of these cells. The responses were compared with those of patients with active lesions, patients who had recovered from infection, and healthy controls. Peripheral blood mononuclear cells from patients with active lesions and recovered donors proliferated vigorously and produced Th1-type cytokine when stimulated withL. majorantigens, whereas in nonhealing patients the proliferative responses were significantly lower and showed a Th2-type response toLeishmaniaantigens. Interleukin-10 (IL-10) production was not a feature ofL. majorstimulation. Flow cytometric analysis revealed thatL. majorantigen induced proliferation of the CD4-positive population and that these cells were the major source of gamma interferon and IL-4. These results show a distinct dichotomy in the cytokine response toL. majorinfection.