bluuebunny/crossref_metadata_2025_split huggingface dataset:
Eradication ofCryptosporidium parvumInfection by Mice with Ovalbumin-Specific T Cells
Authors: Lukin Kara , Cosyns Mary , Mitchell Tom , Saffry Milton , Hayward Anthony 
Published: July 2002

ABSTRACTCD154 is necessary for mice to clear aCryptosporidium parvuminfection, but whether this ligand has to be expressed on T cells with specificity forC. parvumhas not been determined. We infected DO11.10 (ovalbumin specific) T-cell receptor transgenic mice that had been bred to a RAG−/−background withC. parvumand found that the infection was cleared within 6 weeks, while RAG−/−controls were unable to clearC. parvuminfection. Recovery was accompanied by an increase in the number of splenic T cells with the CD44highphenotype that characterizes memory cells. To determine whether aC. parvum-infected environment sufficed to activate transgenic T cells, we reconstitutedC. parvum-infected BALB/c SCID mice with DO11.10 RAG−/−splenocytes. Fecal excretion ofC. parvumantigen ceased in the 12 weeks following the adoptive transfer, unless the mice were also injected with tolerizing doses of ovalbumin. DO11.10 T cells were found in the submucosa ofC. parvum-infected, but not uninfected, BALB/c SCID hosts within 48 h of injection. The transferred DO11.10 T cells divided and acquired a CD44highmemory phenotype inC. parvum-infected, but not uninfected, recipients. DO11.10 splenocytes from CD154 knockout donors failed to clear aC. parvuminfection, confirming a requirement for CD154 in recovery. In vitro, the DO11.10 cells did not proliferate in response toC. parvumantigen, and a tBlast GenBank search revealed no matches between the ovalbumin peptide andC. parvumDNA sequences.C. parvum-infected SCID mice given RAG−/−CD8+T cells with aListeria-specific transgene did not recover fromC. parvuminfection. Our data suggest that antigen-nonspecific CD4+T-cell effector mechanisms in combination with the innate arm of the immune system are sufficient for the eradication ofC. parvuminfection.
Investigation into the Mechanism of Gamma Interferon-Mediated Inhibition ofToxoplasma gondiiin Murine Astrocytes
Authors: Halonen Sandra K. , Weiss Louis M. 
Published: July 2002

ABSTRACTToxoplasma gondiiis an obligate intracellular parasite that is a common opportunistic pathogen of the central nervous system in AIDS patients. Gamma interferon (IFN-γ) alone or in combination with interleukin-1 (IL-1), IL-6, or tumor necrosis factor alpha significantly inhibits the growth ofT. gondiiin murine astrocytes, suggesting these are important nonimmune effector cells in the brain. Inhibition was found to be independent of a nitric oxide-mediated or tryptophan starvation mechanism. Both reactive oxygen intermediates and iron deprivation are IFN-γ-mediated mechanisms known to operate against intracellular parasites in other cell types. Astrocytes generated from mice genetically deficient in the production of reactive oxygen intermediates (phox−/−mice) were found to inhibit growth ofT. gondiiwhen stimulated with IFN-γ alone or in combination with other cytokines. The reactive oxygen inhibitor catalase and the reactive oxygen scavengers mannitol and thiourea failed to reverse the IFN-γ-induced inhibition ofT. gondiiin astrocytes. These data indicate that IFN-γ-induced inhibition in astrocytes is independent of reactive oxygen intermediates. IFN-γ-induced inhibition could not be reversed by the addition of iron salts, ferric citrate, ferric nitrate, or ferric transferrin. Pretreatment of astrocytes with desferrioxamine also did not induce the inhibition ofT. gondii. These data indicate that the mechanism of IFN-γ inhibition was not due to iron deprivation. IFN-γ had no effect onT. gondiiinvasion of astrocytes, but inhibition of growth and loss of tachyzoite vacuoles were evident in IFN-γ-treated astrocytes by 24 h after invasion. Overall, these data suggest that IFN-γ-activated astrocytes inhibitT. gondiiby an as-yet-unknown mechanism.
The
opdB
Locus Encodes the Trypsin-Like Peptidase Activity of
Treponema denticola
Authors: Fenno J. Christopher , Lee Si Young , Bayer Christopher H. , Ning Yu 
Published: July 2002

ABSTRACT

High levels of
Treponema denticola
in subgingival dental plaque are associated with severe periodontal disease.
T. denticola
, along with
Porphyromonas gingivalis
and
Bacteroides forsythus
, are the only cultivatable oral microorganisms that produce significant amounts of “trypsin-like” peptidase activity. The ability of subgingival plaque to hydrolyze
N
-α-benzoyl-
dl
-arginine-2-naphthylamide (BANA) is associated with high levels of one or more of these organisms. The purpose of this study was to identify the gene encoding trypsin-like activity in
T. denticola
and thus facilitate molecular-level studies of its potential role in disease. Using published peptide sequences of a
T. denticola
surface-associated oligopeptidase with BANA-hydrolyzing activity, we identified the gene, designated
opdB
, in an apparently noncoding region of the
T. denticola
genome unannotated contigs (11/2000;
http://www.tigr.org
). The
opdB
gene begins with a TTG start codon and encodes a 685-residue peptide with high homology to the oligopeptidase B family in prokaryotes and eukaryotes. An isogenic
T. denticola opdB
mutant was constructed by allelic replacement mutagenesis using an
ermF/AM
gene cassette. The mutant lacked BANA-hydrolyzing activity and had a slightly slower growth rate than the parent strain. This mutant will be used in future studies of interactions of
T. denticola
with host cells and tissue.
Attenuation of Virulence and Changes in Morphology in
Candida albicans
by Disruption of the
N
-Acetylglucosamine Catabolic Pathway
Authors: Singh Praveen , Ghosh Sharmistha , Datta Asis 
Published: July 2002

ABSTRACT

A
Candida albicans
mutant with mutations in the
N
-acetylglucosamine (GlcNAc) catabolic pathway gene cluster, including the GlcNAc-6-phosphate deacetylase (
DAC1
), glucosamine-6-phosphate deaminase (
NAG1
), and GlcNAc kinase (
HXK1
) genes, was not able to grow on amino sugars, exhibited highly attenuated virulence in a murine systemic candidiasis model, and was less adherent to human buccal epithelial cells in vitro. No germ tubes were formed by the mutant after induction with GlcNAc, but the mutant exhibited hyperfilamentation under stress-induced filamentation conditions. In addition, the GlcNAc catabolic pathway played a vital role in determining the colony phenotype. Our results imply that this pathway is very important because of its diverse links with pathways involved in virulence and morphogenesis of the organism.
Novel Molecular Variants of Allele I of the
Escherichia coli
P Fimbrial Adhesin Gene
papG
Authors: Johnson James R. , Stell Adam L. , Kaster Nicholas , Fasching Claudine , O'Bryan Timothy T. 
Published: July 2002

ABSTRACT

P fimbriae of extraintestinal pathogenic
Escherichia coli
mediate digalactoside-specific adherence via the tip adhesin molecule PapG, which occurs in three known variants (I to III), which are encoded by the corresponding three alleles of
papG
. In the present study, newly discovered variants of
papG
allele I and the respective wild-type source strains were characterized. One of the new
papG
allele I variants conferred a unique agglutination phenotype that combined the phenotypes associated with
papG
alleles I, II, and III. Comparative hydrophilicity analysis of predicted PapG peptides revealed regions that might explain the observed phenotypic similarities and differences between the PapG variants. The new
papG
allele I variants occurred either as the sole
papG
allele or together with both
papG
alleles II and III, rather than with only
papG
allele III, as in archetypal strains J96 and CP9. They also occurred in the absence of the usual F13
papA
allele. One of the new
papG
allele I variants occurred in a serogroup O6 strain that, according to random amplified polymorphic DNA analysis, was phylogenetically distant from the “J96-like” clonal group of
E. coli
O4:H5, which includes all previously identified examples of
papG
allele I. Cluster analysis of nucleotide and predicted peptide sequences suggested that
papG
allele I represents the earliest evolutionary branch from a common
papG
ancestor. These results demonstrate unexpected diversity within
papG
allele I and, together with previous findings, suggest that the J96-like clonal group of
E. coli
O4:H5 may represent the original source of
papG
within the species.
CD14 Is Expressed and Released as Soluble CD14 by Human Intestinal Epithelial Cells In Vitro: Lipopolysaccharide Activation of Epithelial Cells Revisited
Authors: Funda David P. , Tučková Ludmila , Farré Maria A. , Iwase Takashi , Moro Itaru , Tlaskalová-Hogenová Helena 
Published: July 2002

ABSTRACTHuman endothelial as well as epithelial cells were shown to respond to lipopolysaccharides (LPSs). However, the expression and release of CD14 by these so-called CD14-negative cells have not been studied in detail. We investigated three human intestinal epithelial cell lines (ECLs), SW-480, HT-29, and Caco-2, for their expression of CD14 and CD11c/CD18 as well as their responsiveness to endotoxins. Fluorescence-activated cell sorter analysis revealed no expression of CD11c/CD18, but there was low expression of membrane-bound CD14 on HT-29, Caco-2, and SW-480 ECLs. Both Western blotting and reverse transcription-PCR confirmed the CD14 positivity of all three intestinal ECLs. No substantial modulation of CD14 expression was achieved after 6, 8, 18, 24, and 48 h of cultivation with 10-fold serial dilutions of LPS ranging from 0.01 ng/ml to 100 μg/ml. Interestingly, soluble CD14 was found in the tissue culture supernatants of all three ECLs. Finally, only HT-29 and SW-480, and not Caco-2, cells responded to LPS exposure (range, 0.01 ng/ml to 100 μg/ml) by interleukin 8 release. Thus, we show that HT-29, SW-480, and Caco-2 human intestinal ECLs express membrane-bound CD14. As Caco-2 cells did not respond to LPS, these cell lines might be an interesting model for studying the receptor complex for LPS. The fact that human intestinal epithelial cells are capable not only of expression but also of release of soluble CD14 may have important implications in vivo, e.g., in shaping the interaction between the mucosal immune system and bacteria in the gut and/or in the pathogenesis of endotoxin shock.
Potent Stimulation of the Innate Immune System by aLeishmania brasiliensisRecombinant Protein
Authors: Borges Monamaris M. , Campos-Neto Antonio , Sleath Paul , Grabstein Keneth H. , Morrissey Philip J. , Skeiky Yasir A. W. , Reed Steven G. 
Published: July 2002

ABSTRACTThe interaction of the innate immune system with the microbial world involves primarily two sets of molecules generally known as microbial pattern recognition receptors and microbial pattern recognition molecules, respectively. Examples of the former are the Toll receptors present particularly in macrophages and dendritic cells. Conversely, the microbial pattern recognition molecules are conserved protist homopolymers, such as bacterial lipopolysaccharides, lipoteichoic acids, peptidoglycans, glucans, mannans, unmethylated bacterial DNA, and double-strand viral RNA. However, for protists that lack most of these molecules, such as protozoans, the innate immune system must have evolved receptors that recognize other groups of microbial molecules. Here we present evidence that a highly purified protein encoded by aLeishmania brasiliensisgene may be one such molecule. This recombinant leishmanial molecule, a homologue of eukaryotic ribosomal elongation and initiation factor 4a (LeIF), strongly stimulates spleen cells from severe combined immunodeficient (SCID) mice to produce interleukin-12 (IL-12), IL-18, and high levels of gamma interferon. In addition, LeIF potentiates the cytotoxic activity of the NK cells of these animals. Because LeIF is a conserved molecule and because SCID mice lack T and B lymphocytes but have a normal innate immune system (normal reticuloendothelial system and NK cells), these results suggest that proteins may also be included as microbial pattern recognition molecules. The nature of the receptor involved in this innate recognition is unknown. However, it is possible to exclude the Toll receptor Tlr4 as a putative LeIF receptor because the gene encoding this receptor is defective in C3H/HeJ mice, the mouse strain used in the present studies.
Ontogeny of Th1 Memory Responses against aBrucella abortusConjugate
Authors: Scharf Orit , Agranovich Inna , Lee Katherine , Eller Nancy L. , Levy Lily , Inman John , Scott Dorothy E. , Golding Basil 
Published: July 2002

ABSTRACTProtective immune responses to intracellular pathogens such asBrucella abortusare characteristically Th1-like. Recently we demonstrated that heat-killedB. abortus(HKBa), a strong Th1 stimulus, conjugated to ovalbumin (HKBA-OVA), but notB. abortusalone, can alter the antigen-specific cytokine profile from Th2- to Th1-like. In this report we study the ability of a single injection ofB. abortusto switch a Th2 to a Th1 response in immature mice. One-day- and 1-week-old mice were given a single injection ofB. abortusin the absence or presence of OVA, and at maturity mice were challenged with an allergenic preparation, OVA with alum (OVA-A).B. abortusgiven without OVA did not diminish the subsequent Th2 response in either age group. In contrast, mice receiving a single injection ofB. abortus-OVA at the age of 1 week, but not those injected at the age of 1 day, had reversal of the ratio of OVA-specific Th1 to Th2 cells and decreased immunoglobulin E levels after allergen challenge as adults. Within 6 h both 1-day- and 1-week-old mice expressed interleukin-12 p40 mRNA following eitherB. abortusorB. abortus-OVA administration. However, only the 1-week-old mice exhibited increased expression of gamma interferon (IFN-γ) mRNA. The absence of the early IFN-γ response in 1-day-old mice may explain their inability to generate a Th1 memory response. These results suggest that at early stages of immune development, responses to intracellular bacteria may be Th2- rather than Th1-like. Furthermore, they suggest that the first encounter with antigen evokes either a Th1- or a Th2-like response which becomes imprinted, so that subsequent memory responses conform to the original Th bias. This has implications for protection against infectious agents and development of allergic responses.
Human Gingival CD14+Fibroblasts Primed with Gamma Interferon Increase Production of Interleukin-8 in Response to Lipopolysaccharide through Up-Regulation of Membrane CD14 and MyD88 mRNA Expression
Authors: Tamai Riyoko , Sakuta Tetsuya , Matsushita Kenji , Torii Mitsuo , Takeuchi Osamu , Akira Shizuo , Akashi Sachiko , Espevik Terje , Sugawara Shunji , Takada Haruhiko 
Published: July 2002

ABSTRACTGamma interferon (IFN-γ)-primed human gingival fibroblasts (HGF) have been shown to produce higher levels of interleukin-8 (IL-8) upon stimulation with bacterial products and inflammatory cytokines than nonprimed controls. In this study, we examined whether priming of HGF with IFN-γ up-regulates IL-8 production by the cells in response to purified lipopolysaccharide (LPS). The priming effect of IFN-γ was clearly observed in the high-CD14-expressing (CD14high) HGF but not in the low-CD14-expressing (CD14low) HGF. The CD14highHGF were most effectively primed with IFN-γ (1,000 IU/ml) for 72 h. To elucidate the mechanism of the priming effects of IFN-γ for the LPS response by HGF, we examined whether IFN-γ regulated expression of CD14, Toll-like receptor 2 (TLR2), TLR4, MD-2, and MyD88, all of which are molecules suggested to be associated with LPS signaling. In CD14highHGF, IFN-γ markedly up-regulated CD14 and MyD88 but not TLR4 protein and MD-2 mRNA expression, while in CD14lowHGF, IFN-γ slightly increased MyD88 and scarcely affected CD14, TLR4 protein, and MD-2 mRNA levels. LPS-induced IL-8 production by IFN-γ-primed CD14highHGF was significantly inhibited by monoclonal antibodies (MAbs) against CD14 and TLR4, but not by an anti-TLR2 MAb. These findings suggested that IFN-γ primed CD14highHGF to enhance production of IL-8 in response to LPS through augmentation of the CD14-TLR system, where the presence of membrane CD14 was indispensable for the response of HGF to LPS.
Analysis of Genes Encoding an Alternative Nitrogenase in the Archaeon
Methanosarcina barkeri
227
Authors: Chien Yueh-Tyng , Auerbuch Victoria , Brabban Andrew D. , Zinder Stephen H. 
Published: July 2002

ABSTRACT

Methanosarcina barkeri
227 possesses two clusters of genes potentially encoding nitrogenases. We have previously demonstrated that one cluster, called
nif2
, is expressed under molybdenum (Mo)-sufficient conditions, and the deduced amino acid sequences for nitrogenase structural genes in that cluster most closely resemble those for the Mo nitrogenase of the gram-positive eubacterium
Clostridium pasteurianum
. The previously cloned
nifH1
from
M. barkeri
shows phylogenetic relationships with genes encoding components of eubacterial Mo-independent eubacterial alternative nitrogenases and other methanogen nitrogenases. In this study, we cloned and sequenced
nifD1
and part of
nifK1
from
M. barkeri
227. The deduced amino acid sequence encoded by
nifD1
from
M. barkeri
showed great similarity with
vnfD
gene products from vanadium (V) nitrogenases, with an 80% identity at the amino acid level with the
vnfD
gene product from
Anabaena variabilis
. Moreover, there was a small open reading frame located between
nifD1
and
nifK1
with clear homology to
vnfG
, a hallmark of eubacterial alternative nitrogenases. Stimulation of diazotrophic growth of
M. barkeri
227 by V in the absence of Mo was demonstrated. The unusual complement of
nif
genes in
M. barkeri
227, with one cluster resembling that from a gram-positive eubacterium and the other resembling a eubacterial V nitrogenase gene cluster, suggests horizontal genetic transfer of those genes.
Characterization of LrpC DNA-Binding Properties and Regulation of
Bacillus subtilis lrpC
Gene Expression
Authors: Beloin Christophe , Exley Rachel , Mahé Anne-Laure , Zouine Mohamed , Cubasch Stephanie , Le Hégarat Françoise 
Published: July 2002

ABSTRACT

The
lrpC
gene was identified during the
Bacillus subtilis
genome sequencing project. Previous experiments suggested that LrpC has a role in sporulation and in the regulation of amino acid metabolism and that it shares features with
Escherichia coli
Lrp, a transcription regulator (C. Beloin, S. Ayora, R. Exley, L. Hirschbein, N. Ogasawara, Y. Kasahara, J. C. Alonso, and F. Le Hégarat, Mol. Gen. Genet. 256:63–71, 1997). To characterize the interactions of LrpC with DNA, the protein was overproduced and purified. We show that LrpC binds to multiple sites in the upstream region of its own gene with a stronger affinity for a region encompassing
P1
, one of the putative promoters identified (
P1
and
P2
). By analyzing
lrpC-lacZ
transcriptional fusions, we demonstrated that
P1
is the major in vivo promoter and that, unlike many members of the
lrp/asnC
family,
lrpC
is not negatively autoregulated but rather slightly positively autoregulated. Production of LrpC in vivo is low in both rich and minimal media (50 to 300 LrpC molecules per cell). In rich medium, the cellular LrpC content is six- to sevenfold lower during the exponentional phase than during the stationary growth phase. Possible determinants and the biological significance of the regulation of
lrpC
expression are discussed.
Properties of Various
RHO1
Mutant Alleles of
Cryptococcus neoformans
Authors: Chang Yun C. , Penoyer Lisa A. 
Published: July 2002

ABSTRACT

The
RHO1
homologue of
Cryptococcus neoformans
complemented
Saccharomyces cerevisiae rho1
mutations. The results of overexpression and site-specific mutagenesis of
CnRHO1
in
C. neoformans
and
S. cerevisiae
indicated that although
CnRHO1
could functionally substitute for the
RHO1
gene of
S. cerevisiae
, mutants of
cnrho1
manifested unique features in certain aspects.
A Second Allele of
eppA
in
Borrelia burgdorferi
Strain B31 Is Located on the Previously Undetected Circular Plasmid cp9-2
Authors: Miller Jennifer C. , Bono James L. , Babb Kelly , El-Hage Nazira , Casjens Sherwood , Stevenson Brian 
Published: July 2002

ABSTRACT

Although sequence analysis of
Borrelia burgdorferi
isolate B31 was recently declared “complete,” we found that cultures of this strain can contain a novel 9-kb circular plasmid, cp9-2. The newly described plasmid contains both sequence similarities with and differences from the previously identified B31 plasmid cp9-1 (formerly cp9). cp9-1 and cp9-2 each encode a unique allele of EppA, a putative membrane protein synthesized by
B. burgdorferi
during mammalian infection.
Identification by Gene Deletion Analysis of a Regulator, VmsR, That Controls Virginiamycin Biosynthesis in
Streptomyces virginiae
Authors: Kawachi Ryu , Wangchaisoonthorn Usamas , Nihira Takuya , Yamada Yasuhiro 
Published: July 2002

ABSTRACT

Virginiae butanolide (VB)-BarA of
Streptomyces virginiae
is one of the newly discovered pairs of a butyrolactone autoregulator and a corresponding receptor protein of
Streptomyces
species and regulates the production of the antibiotic virginiamycin (VM) in
S. virginiae
. The gene
vmsR
was found to be situated 4.7 kbp upstream of the
barA
gene, which encodes the VB-specific receptor. The
vmsR
product was predicted to be a regulator of VM biosynthesis based on its high homology to some
Streptomyces
pathway-specific transcriptional regulators for the biosynthetic gene clusters of polyketide antibiotics, such as
Streptomyces peucetius
DnrI (47.5% identity, 84.3% similarity), which controls daunorubicin biosynthesis. A
vmsR
deletion mutant was created by homologous recombination. Neither virginiamycin M
1
nor virginiamycin S was produced in the
vmsR
mutant, while amounts of VB and BarA similar to those produced in the wild-type strain were detected. Reverse transcription-PCR analyses confirmed that the
vmsR
deletion had no deleterious effects on the transcription of the
vmsR
-surrounding genes, indicating that VmsR is a positive regulator of VM biosynthesis in
S. virginiae
.
The
Sinorhizobium meliloti
Lon Protease Is Involved in Regulating Exopolysaccharide Synthesis and Is Required for Nodulation of Alfalfa
Authors: Summers Michael L. , Botero Lina M. , Busse Scott C. , McDermott Timothy R. 
Published: July 2002

ABSTRACT

While screening for
Sinorhizobium meliloti
Pho regulatory mutants, a transposon mutant was isolated that constitutively expressed higher levels of acid and alkaline phosphatase enzymes. This mutant was also found to form pseudonodules on alfalfa that were delayed in appearance relative to those formed by the wild-type strain, it contained few bacteroids, and it did not fix nitrogen. Sequence analysis of the transposon insertion site revealed the affected gene to have high homology to Lon proteases from a number of organisms. In minimal succinate medium, the mutant strain was found to grow more slowly, reach lower maximal optical density, and produce more extracellular polysaccharide (EPS) than the wild-type strain. The mutant fluoresced brightly on minimal succinate agar containing calcofluor (which binds to EPSI, a constitutively expressed succinoglycan), and gas chromotographic analysis of purified total EPS showed that the glucose-to-galactose ratio in the
lon
mutant total EPS was 5.0 ± 0.2 (mean ± standard error), whereas the glucose-to-galactose ratio in the wild-type strain was 7.1 ± 0.5. These data suggested that in addition to EPSI, the
lon
mutant also constitutively synthesized EPSII, a galactoglucan which is the second major EPS known to be produced by
S. meliloti
, but typically is expressed only under conditions of phosphate limitation.
13
C nuclear magnetic resonance analysis showed no major differences between EPS purified from the mutant and wild-type strains. Normal growth, EPS production, and the symbiotic phenotype were restored in the mutant strain when the wild-type
lon
gene was present in
trans
. The results of this study suggest that the
S. meliloti
Lon protease is important for controlling turnover of a constitutively expressed protein(s) that, when unregulated, disrupts normal nodule formation and normal growth.