bluuebunny/crossref_metadata_2025_split huggingface dataset:
Role of Interleukin-18 (IL-18) during Lethal Shock: Decreased Lipopolysaccharide Sensitivity but Normal Superantigen Reaction in IL-18-Deficient Mice
Authors: Hochholzer Peter , Lipford Grayson B. , Wagner Hermann , Pfeffer Klaus , Heeg Klaus 
Published: July 2002

ABSTRACTLethal shock can be associated with excessive secretion of cytokines such as tumor necrosis factor (TNF) and gamma interferon (IFN-γ). IFN-γ mediates macrophage activation and appears to be controlled by interleukin (IL)-12 and IL-18. To investigate the role of IL-18 in vivo, we generated IL-18-deficient mice by gene targeting. IL-18−/−mice showed decreased sensitivity towards lipopolysaccharide (LPS)-induced shock. LPS-induced IFN-γ production was abrogated, yet induction of IL-12 and TNF was not affected. Both wild-type and IL-18-deficient mice succumbed to LPS-induced lethal shock after sensitization withd-galactosamine. However, in marked contrast to LPS, the bacterial superantigenStaphylococcus aureusenterotoxin B (SEB) induced comparable serum levels of IFN-γ in IL-18+/+and IL-18−/−mice, accompanied by an upregulation of cell surface markers CD14, CD122 (IL-2Rβ), and CD132 (IL-2Rγ) on peritoneal macrophages. Moreover, SEB injection rendered IL-18-deficient mice sensitive for subsequent challenge with LPS. The degree of sensitization was comparable to that in wild-type controls with respect to lethality. However, LPS-induced TNF levels in serum were significantly reduced in SEB-sensitized IL-18-deficient mice. These results imply that IL-18 plays an important role in induction of IFN-γ and lethality in response to LPS.
A Recombinant Baculovirus-ExpressedPlasmodium falciparumReceptor-Binding Domain of Erythrocyte Binding Protein EBA-175 Biologically Mimics Native Protein
Authors: Liang Hong , Narum David L. , Fuhrmann Steven R. , Luu Tin , Sim B. Kim Lee 
Published: July 2002

ABSTRACTEBA-175 ofPlasmodium falciparumis a merozoite ligand that binds its receptor glycophorin A on erythrocytes during invasion. The ligand-receptor interaction is dependent on sialic acids as well as the protein backbone of glycophorin A. Region II (RII) of EBA-175 has been defined as the receptor-binding domain. RII is divided into regions F1 and F2, which contain duplicated cysteine motifs. We expressed RII in a baculovirus and show that RII binds erythrocytes with a specificity identical to that of the native protein. We found that, consistent with the binding of erythrocytes to COS cells expressing F2, recombinant baculovirus-expressed F2 bound erythrocytes. About 20% of all baculovirus-expressed RII is N-glycosylated, unlike nativeP. falciparumproteins that remain essentially unglycosylated. However, glycosylation of recombinant RII did not affect its immunogenicity. Antibodies raised against both glycosylated and unglycosylated baculovirus-expressed RII recognizedP. falciparumschizonts in immunofluorescence assays and also gave similar enzyme-linked immunosorbent assay titers. Furthermore, these antibodies have similar abilities to block native EBA-175 binding to erythrocytes. These results allow the development of RII as a vaccine candidate for preclinical assessment.
Identification of
ragAB
as a Temperature-Regulated Operon of
Porphyromonas gingivalis
W50 Using Differential Display of Randomly Primed RNA
Authors: Bonass William A. , Marsh Philip D. , Percival Rimondia S. , Aduse-Opoku Joseph , Hanley Shirley A. , Devine Deirdre A. , Curtis Michael A. 
Published: July 2002

ABSTRACT

Porphyromonas gingivalis
is a gram-negative, black-pigmented anaerobe that has been associated with advanced periodontal disease. The genome of
P. gingivalis
has the potential to produce a number of virulence determinants including proteases, hemagglutinins, hemolysin, invasion-associated proteins, and products of the pathogenicity island
ragAB
; however, little is known about how their expression is controlled. Periodontal pockets experience a higher temperature during inflammation, and this elevated temperature may influence the pathogenicity of
P. gingivalis
by changing its patterns of gene expression. In this study, RNA has been isolated from cells of
P. gingivalis
grown to steady state at temperatures of 37, 39, and 41°C under hemin excess conditions (pH 7.0) in a chemostat. The RNA was subjected to PCR amplification following reverse transcription, using various combinations of randomly selected oligonucleotide primers. Reproducible RNA fingerprints have been obtained; however, differences were demonstrated in the RNA profiles of cells grown at the three temperatures, indicating differences in gene expression. Several PCR fragments were isolated that appeared to represent temperature-regulated genes. The nucleotide sequence of one of these has been identified as part of the
ragAB
locus, which codes for both a 55-kDa immunodominant antigen (RagB) and a homologue of the family of TonB-linked outer membrane receptors (RagA). These data indicate that expression of
ragAB
may be modulated in response to changes in temperature and that this may suggest a mechanism of evading the host response in the inflamed periodontal pocket.
exl
, an Exchangeable Genetic Island in
Neisseria meningitidis
Authors: Kahler C. M. , Blum E. , Miller Y. K. , Ryan D. , Popovic T. , Stephens D. S. 
Published: July 2002

ABSTRACT

The genetic structure and evolution of a novel exchangeable meningococcal genomic island was defined for the important human pathogen
Neisseria meningitidis
. In 125 meningococcal strains tested, one of three unrelated nucleotide sequences, designated
exl
(exchangeable locus), was found between a gene required for heme utilization,
hemO
, and
col
, encoding a putative
Escherichia coli
collagenase homologue. The 5′ boundary of each
exl
cassette was the stop codon of
hemO
, whereas the 3′ boundary was delineated by a 33-bp repeat containing neisserial uptake sequences located downstream of
col
. One of the three alternative
exl
cassettes contained the meningococcal hemoglobin receptor gene,
hmbR
(
exl3
). In other meningococcal strains,
hmbR
was absent from the genome and was replaced by either a nucleotide sequence containing a novel open reading frame,
exl2
, or a cassette containing
exl3
. The proteins encoded by
exl2
and
exl3
had no significant amino acid homology to HmbR but contained six motifs that are also present in the lipoprotein components of the lactoferrin (LbpB), transferrin (TbpB), and hemoglobin-haptoglobin (HpuA) uptake systems. To determine the evolutionary relationships among meningococci carrying
hmbR
,
exl2
, or
exl3
, isolates representing 92 electrophoretic types were examined.
hmbR
was found throughout the population structure of
N. meningitidis
(genetic distance, >0.425), whereas
exl2
and
exl3
were found in clonal groups at genetic distances of <0.2. The commensal neisserial species were identified as reservoirs for all of the
exl
cassettes found in meningococci. The structure of these cassettes and their correlation with clonal groups emphasize the extensive gene pool and frequent horizontal DNA transfer events that contribute to the evolution and virulence of
N. meningitidis.
Tumor Necrosis Factor Alpha Increases Human Cerebral Endothelial Cell Gb
3
and Sensitivity to Shiga Toxin
Authors: Eisenhauer Patricia B. , Chaturvedi Prasoon , Fine Richard E. , Ritchie Andrew J. , Pober Jordan S. , Cleary Thomas G. , Newburg David S. 
Published: July 2002

ABSTRACT

Hemolytic uremic syndrome (HUS) is associated with intestinal infection by enterohemorrhagic
Escherichia coli
strains that produce Shiga toxins. Globotriaosylceramide (Gb
3
) is the functional receptor for Shiga toxin, and tumor necrosis factor alpha (TNF-α) upregulates Gb
3
in both human macrovascular umbilical vein endothelial cells and human microvascular brain endothelial cells. TNF-α treatment enhanced Shiga toxin binding and sensitivity to toxin. This upregulation was specific for Gb
3
species containing normal fatty acids (NFA). Central nervous system (CNS) pathology in HUS could involve cytokine-stimulated elevation of endothelial NFA-Gb
3
levels. Differential expression of Gb
3
species may be a critical determinant of Shiga toxin toxicity and of CNS involvement in HUS.
YopB of
Yersinia enterocolitica
Is Essential for YopE Translocation
Authors: Nordfelth Roland , Wolf-Watz Hans 
Published: July 2002

ABSTRACT

A previous study has shown that YopB of
Yersinia
spp. is essential for translocation of Yop effectors across the eucaryotic plasma membrane (M.-P. Sory and G. R. Cornelis, Mol. Microbiol. 14:583–594, 1994). However, this role was recently challenged (V. T. Lee and O. Schneewind, Mol. Microbiol. 31:1619–1629, 1999). Using protease protection and digitonin extraction, we reconfirm that YopB of
Yersinia enterocolitica
is essential for the translocation of YopE into HeLa cell monolayers.
Ascaris suum-Derived Products Induce Human Neutrophil Activation via a G Protein-Coupled Receptor That Interacts with the Interleukin-8 Receptor Pathway
Authors: Falcone Franco H. , Rossi Adriano G. , Sharkey Rose , Brown Alan P. , Pritchard David I. , Maizels Rick M. 
Published: July 2002

ABSTRACTInfection with tissue-migrating helminths is frequently associated with intense granulocyte infiltrations. Several host-derived factors are known to mediate granulocyte recruitment to the tissues, but less attention has been paid to how parasite-derived products trigger this process. Parasite-derived chemotactic factors which selectively recruit granulocytes have been described, but nothing is known about which cellular receptors respond to these agents. The effect of products from the nematodesAscaris suum, Toxocara canis, andAnisakis simplexon human neutrophils were studied. We monitored four parameters of activation: chemotaxis, cell polarization, intracellular Ca2+transients, and priming of superoxide anion production. Body fluids ofA. suum(ABF) andT. canis(TcBF) induced strong directional migration, shape change, and intracellular Ca2+transients. ABF also primed neutrophils for production of superoxide anions. Calcium mobilization in response toA. suum-derived products was completely abrogated by pretreatment with pertussis toxin, implicating a classical G protein-coupled receptor mechanism in the response to ABF. Moreover, pretreatment with interleukin-8 (IL-8) completely abrogated the response to ABF, demonstrating desensitization of a common pathway. However, ABF was unable to fully desensitize the response to IL-8, and binding to CXCR1 or CXCR2 was excluded in experiments using RBL-2H3 cells transfected with the two human IL-8 receptors. Our results provide the first evidence for a direct interaction between a parasite-derived chemotactic factor and the host's chemotactic network, via a novel G protein-coupled receptor which interacts with the IL-8 receptor pathway.
Identification and Cloning of a Cryptococcal Deacetylase That Produces Protective Immune Responses
Authors: Biondo Carmelo , Beninati Concetta , Delfino Demetrio , Oggioni Marco , Mancuso Giuseppe , Midiri Angelina , Bombaci Mauro , Tomaselli Giuseppe , Teti Giuseppe 
Published: July 2002

ABSTRACTCell-mediated immunity plays a crucial role in host defenses againstCryptococcus(Filobasidiella)neoformans. Therefore, the identification of cryptococcal antigens capable of producing T-cell-mediated responses, such as delayed-type hypersensitivity (DTH) reactions, may be useful in the development of immune-based strategies to control cryptococcosis. In order to characterize DTH-producing antigens, culture supernatants from the unencapsulated Cap-67 strain were separated by anion-exchange chromatography. After further fractionation by preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis, a purified protein with an apparent molecular mass of 25 kDa was found to produce DTH, as evidenced by increased footpad swelling in mice immunized with culture supernatants, relative to unimmunized mice. The 20-amino-acid N-terminal sequence of the 25-kDa protein was used to search data of theC. neoformansGenome Project. Based on the genomic DNA sequence, a DNA probe was used to screen a λ cDNA library prepared from strain B3501. Clones were isolated containing the full-length gene (d25), which showed homology with a number of polysaccharide deacetylases from fungi and bacteria. The recombinant d25 protein expressed inEscherichia coliwas similar to the natural one in DTH-producing activity. Moreover, immunization with either the natural or the recombinant protein prolonged survival and decreased fungal burden in mice challenged with the highly virulentC. neoformansstrain H99. In conclusion, we have described the first cryptococcal gene whose product, a 25-kDa extracellular polysaccharide deacetylase, has been shown to induce protective immunity responses.
Persistence of Protective Immunity to Malaria Induced by DNA Priming and Poxvirus Boosting: Characterization of Effector and Memory CD8+-T-Cell Populations
Authors: Sedegah Martha , Brice Gary T. , Rogers William O. , Doolan Denise L. , Charoenvit Yupin , Jones Trevor R. , Majam Victoria F. , Belmonte Arnel , Lu Minh , Belmonte Maria , Carucci Daniel J. , Hoffman Stephen L. 
Published: July 2002

ABSTRACTThe persistence of immunity to malaria induced in mice by a heterologous DNA priming and poxvirus boosting regimen was characterized. Mice were immunized by priming with DNA vaccine plasmids encoding thePlasmodium yoeliicircumsporozoite protein (PyCSP) and murine granulocyte-macrophage colony-stimulating factor and boosting with recombinant vaccinia encoding PyCSP. BALB/c mice immunized with either high-dose (100 μg of pPyCSP plus 30 μg of pGM-CSF) or low-dose (1 μg of pPyCSP plus 1 μg of pGM-CSF DNA) priming were protected against challenge with 50P. yoeliisporozoites. Protection 2 weeks after immunization was 70 to 100%, persisted at this level for at least 20 weeks, and declined to 30 to 40% by 28 weeks. Eight of eight mice protected at 20 weeks were still protected when rechallenged at 40 weeks. The antigen (Ag)-specific effector CD8+-T-cell population present 2 weeks after boosting had ex vivo Ag-specific cytolytic activity, expressed both gamma interferon (IFN-γ) and tumor necrosis factor alpha, and constituted 12 to 20% of splenic CD8+T cells. In contrast, the memory CD8+-Ag-specific-cell population at 28 weeks lacked cytolytic activity and constituted only 6% of splenic CD8+T cells, but at the single-cell level it produced significantly higher levels of IFN-γ than the effectors. High levels of Ag- or parasite-specific antibodies present 2 weeks after boosting had declined three- to sevenfold by 28 weeks. Low-dose priming was similarly immunogenic and as protective as high-dose priming against a 50-, but not a 250-, sporozoite challenge. These results demonstrate that a heterologous priming and boosting vaccination can provide lasting protection against malaria in this model system.
Use of Heme Compounds as Iron Sources by Pathogenic Neisseriae Requires the Product of the
hemO
Gene
Authors: Zhu Wenming , Hunt Desiree J. , Richardson Anthony R. , Stojiljkovic Igor 
Published: July 2002

ABSTRACT

Heme compounds are an important source of iron for neisseriae. We have identified a neisserial gene,
hemO
, that is essential for heme, hemoglobin (Hb), and haptoglobin-Hb utilization. The
hemO
gene is located 178 bp upstream of the
hmbR
Hb receptor gene in
Neisseria meningitidis
isolates. The product of the
hemO
gene is homologous to enzymes that degrade heme; 21% of its amino acid residues are identical, and 44% are similar, to those of the human heme oxygenase-1. DNA sequences homologous to
hemO
were ubiquitous in commensal and pathogenic neisseriae. HemO genetic knockout strains of
Neisseria gonorrhoeae
and
N. meningitidis
were unable to use any heme source, while the assimilation of transferrin-iron and iron-citrate complexes was unaffected. A phenotypic characterization of a conditional
hemO
mutant, constructed by inserting an isopropyl-β-
d
-thiogalactopyranoside (IPTG)-regulated promoter upstream of the ribosomal binding site of
hemO
, confirmed the indispensability of the HemO protein in heme utilization. The expression of HemO also protected
N. meningitidis
cells against heme toxicity.
hemO
mutants were still able to transport heme into the cell, since both heme and Hb could complement an
N. meningitidis hemA hemO
double mutant for growth. The expression of the HmbR receptor was reduced significantly by the inactivation of the
hemO
gene, suggesting that
hemO
and
hmbR
are transcriptionally linked. The expression of the unlinked Hb receptor, HpuAB, was not altered. Comparison of the polypeptide patterns of the wild type and the
hemO
mutant led to detection of six protein spots with an altered expression pattern, suggesting a more general role of HemO in the regulation of gene expression in
Neisseriae.
Characterization of
tpp1
+
as Encoding a Main Trehalose-6P Phosphatase in the Fission Yeast
Schizosaccharomyces pombe
Authors: Franco Alejandro , Soto Teresa , Vicente-Soler Jero , Guillen Pedro Valero , Cansado Jose , Gacto Mariano 
Published: July 2002

ABSTRACT

We have characterized an open reading frame of 2,454 bp on chromosome I of
Schizosaccharomyces pombe
as the gene encoding trehalose-6P phosphatase (
tpp1
+
). Disruption of
tpp1
+
caused in vivo accumulation of trehalose-6P upon heat shock and prevented cell growth at 37 to 40°C. Accumulation of trehalose-6P in cells bearing a chromosomal disruption of the
tpp1
+
gene and containing a plasmid with
tpp1
+
under the control of the thiamine-repressible promotor correlated with
tpp1
+
repression. The level of
tpp1
+
mRNA rose upon heat shock, osmostress, or oxidative stress and was negatively controlled by cyclic AMP-dependent protein kinase activity. Expression of
tpp1
+
during oxidative or osmotic stress, but not during heat shock, was under positive control by the
wis1-sty1
(equivalent to
phh1
and
spc1
) mitogen-activated protein kinase pathway. Analysis of Tpp1 protein levels suggests that the synthesis of trehalose-6P phosphatase may also be subjected to translational or posttranslational control.
Sinorhizobium meliloti putA
Gene Regulation: a New Model within the Family
Rhizobiaceae
Authors: Soto María José , Jiménez-Zurdo José Ignacio , van Dillewijn Pieter , Toro Nicolás 
Published: July 2002

ABSTRACT

Proline dehydrogenase (PutA) is a bifunctional enzyme that catalyzes the oxidation of proline to glutamate. In
Sinorhizobium meliloti
, as in other microorganisms, the
putA
gene is transcriptionally activated in response to proline. In
Rhodobacter capsulatus
,
Agrobacterium
, and most probably in
Bradyrhizobium
, this activation is dependent on an Lrp-like protein encoded by the
putR
gene, located immediately upstream of
putA
. Interestingly, sequence and genetic analysis of the region upstream of the
S. meliloti putA
gene did not reveal such a
putR
locus or any other encoded transcriptional activator of
putA
. Furthermore, results obtained with an
S. meliloti putA
null mutation indicate the absence of any proline-responsive transcriptional activator and that PutA serves as an autogenous repressor. Therefore, the model of
S. meliloti putA
regulation completely diverges from that of its
Rhizobiaceae
relatives and resembles more that of enteric bacteria. However, some differences have been found with the latter model: (i)
S. meliloti putA
gene is not catabolite repressed, and (ii) the gene encoding for the major proline permease (
putP
) does not form part of an operon with the
putA
gene.
Characterization of the
dnaK
Multigene Family in the Cyanobacterium
Synechococcus
sp. Strain PCC7942
Authors: Nimura Kaori , Takahashi Hideo , Yoshikawa Hirofumi 
Published: July 2002

ABSTRACT

The cyanobacterium
Synechococcus
sp. strain PCC7942 has three
dnaK
homologues (
dnaK1, dnaK2
, and
dnaK3
), and a gene disruption experiment was carried out for each
dnaK
gene by inserting an antibiotic resistance marker. Our findings revealed that DnaK1 was not essential for normal growth, whereas DnaK2 and DnaK3 were essential. We also examined the effect of heat shock on the levels of these three DnaK and GroEL proteins and found a varied response to heat shock, with levels depending on each protein. The DnaK2 and GroEL proteins exhibited a typical heat shock response, that is, their synthesis increased upon temperature upshift. In contrast, the synthesis of DnaK1 and DnaK3 did not respond to heat shock; in fact, the level of DnaK1 protein decreased. We also analyzed the effect of overproduction of each DnaK protein in
Escherichia coli
cells using an inducible expression system. Overproduction of DnaK1 or DnaK2 resulted in defects in cell septation and formation of cell filaments. On the other hand, overproduction of DnaK3 did not result in filamentous cells; rather a swollen and twisted cell morphology was observed. When expressed in an
E. coli dnaK756
mutant,
dnaK2
could suppress the growth deficiency at the nonpermissive temperature, while
dnaK1
and
dnaK3
could not suppress this phenotype. On the contrary, overproduction of DnaK1 or DnaK3 resulted in growth inhibition at the permissive temperature. These results suggest that different types of Hsp70 in the same cellular compartment have specific functions in the cell.
Expression of the
Moraxella catarrhalis
UspA1 Protein Undergoes Phase Variation and Is Regulated at the Transcriptional Level
Authors: Lafontaine Eric R. , Wagner Nikki J. , Hansen Eric J. 
Published: July 2002

ABSTRACT

The UspA1 protein of
Moraxella catarrhalis
has been shown to function as an adhesin that mediates adherence to human epithelial cell lines in vitro (E. R. Lafontaine, L. D. Cope, C. Aebi, J. L. Latimer, G. H. McCracken, Jr., and E. J. Hansen, J. Bacteriol. 182:1364–1373, 2000). In the present study, cell lysates prepared from individual colonies of several
M. catarrhalis
wild-type strains were analyzed by Western blot analysis using monoclonal antibodies (MAbs) specific for the UspA1 protein. Expression of UspA1 was shown to exhibit phase variation that was correlated with both adherence ability in vitro and the number of guanine (G) residues contained within a homopolymeric [poly(G)]tract located upstream of the
uspA1
open reading frame (ORF). Nucleotide sequence analysis revealed that isolates expressing relatively high levels of UspA1 had 10 G residues in their
uspA1
poly(G)tracts, whereas isolates that expressed much lower levels of UspA1 had 9 G residues. This poly(G) tract was located 30 nucleotides (nt) upstream of the
uspA1
ORF and 168 nt downstream of the
uspA1
transcriptional start site. Primer extension experiments, RNA slot blot analysis, and
cat
reporter constructs were used to demonstrate that
M. catarrhalis
isolates with 10 G residues in their
uspA1
poly(G) tracts expressed two-to threefold more
uspA1
mRNA than did isolates which had 9 G residues in their poly(G)tracts. Northern hybridization analysis revealed that an intact
uspA1
mRNA was readily detectable in RNA from
M. catarrhalis
isolates that had 10 G residues in their
uspA1
poly(G) tracts, whereas no full-length
uspA1
mRNA was observed in isolates whose poly(G)tracts contained 9 G residues.
M. catarrhalis
strain O35E
uspA1
genes that contained wild-type and mutated poly(G) tracts were expressed in
Haemophilus influenzae
to demonstrate that the length and composition of the poly(G)tract affected expression of UspA1.