bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polymorphism of Repeated Regions of Pertactin in
Bordetella pertussis
,
Bordetella parapertussis
, and
Bordetella bronchiseptica
Authors: Boursaux-Eude Caroline , Guiso Nicole 
Published: July 2002

ABSTRACT

Pertactin is an outer membrane protein expressed by
Bordetella pertussis
,
Bordetella parapertussis
, and
Bordetella bronchiseptica
that induces protective immunity to
Bordetella
infections. The immunodominant and immunoprotective epitopes of pertactin include two repeated regions, I and II. Comparison of these two repeated regions showed that
B. parapertussis
pertactin is invariant, whereas
B. pertussis
pertactin varies mostly in region I and
B. bronchiseptica
pertactin varies in both repeated regions I and II, but mostly in region II. These differences may result from specific characteristics of these
Bordetella
species.
Inhibition of Bacterial Superantigens by Peptides and Antibodies
Authors: Visvanathan Kumar , Charles Alain , Bannan Jason , Pugach Pavel , Kashfi Khosrow , Zabriskie John B. 
Published: July 2002

ABSTRACTThe pyrogenic exotoxins of group A streptococci and staphylococcal enterotoxins are a family of structurally related superantigens with similar biological activity. Two distinct areas have been identified which have a highly conserved amino acid homology in all of the toxin families. A number of peptides were constructed from these regions, some of which were concatenated and polymerized to enhance their immunogenicity in animals. Antibodies prepared against these polymerized peptides were used to serologically identify the majority of the superantigen toxins, block the biological activities of the superantigens, and protect an experimental animal model against shock. In addition certain peptides were able per se to block up to 90% of the proliferative responses induced by the toxins. The peptide also proved protective in a septic shock model in mice. Binding experiments indicate that the peptide binds tightly to the major histocompatibility complex class II molecule, thus preventing binding and hence activation of the superantigen. The selective and rapid binding of the peptide to the major histocompatibility complex class II molecule may lead to a novel therapeutic modality in treatment of superantigen-mediated diseases.
Mosaic Genes and Mosaic Chromosomes: Intra- and Interspecies Genomic Variation of
Streptococcus pneumoniae
Authors: Hakenbeck Regine , Balmelle Nadège , Weber Beate , Gardès Christophe , Keck Wolfgang , de Saizieu Antoine 
Published: July 2002

ABSTRACT

Streptococcus pneumoniae
remains a major causative agent of serious human diseases. The worldwide increase of antibiotic resistant strains revealed the importance of horizontal gene transfer in this pathogen, a scenario that results in the modulation of the species-specific gene pool. We investigated genomic variation in 20
S. pneumoniae
isolates representing major antibiotic-resistant clones and 10 different capsular serotypes. Variation was scored as decreased hybridization signals visualized on a high-density oligonucleotide array representing 1,968 genes of the type 4 reference strain KNR.7/87. Up to 10% of the genes appeared altered between individual isolates and the reference strain; variability within clones was below 2.1%. Ten gene clusters covering 160 kb account for half of the variable genes. Most of them are associated with transposases and are assumed to be part of a flexible gene pool within the bacterial population; other variable loci include mosaic genes encoding antibiotic resistance determinants and gene clusters related to bacteriocin production. Genomic comparison between
S. pneumoniae
and commensal
Streptococcus mitis
and
Streptococcus oralis
strains indicates distinct antigenic profiles and suggests a smooth transition between these species, supporting the validity of the microarray system as an epidemiological and diagnostic tool.
Antibodies to a Surface-Exposed, N-terminal Domain of Aggregation Substance Are Not Protective in the Rabbit Model of
Enterococcus faecalis
Infective Endocarditis
Authors: McCormick John K. , Hirt Helmut , Waters Christopher M. , Tripp Timothy J. , Dunny Gary M. , Schlievert Patrick M. 
Published: July 2002

ABSTRACT

The aggregation substance (AS) surface protein from
Enterococcus faecalis
has been implicated as an important virulence factor for the development of infective endocarditis. To evaluate the role of antibodies specific for Asc10 (the AS protein from the conjugative plasmid pCF10) in protective immunity to infective endocarditis, an N-terminal region of Asc10 lacking the signal peptide and predicted to be surface exposed (amino acids 44 to 331; AS
44–331
) was cloned with a C-terminal histidine tag translational fusion and expressed from
Escherichia coli
. N-terminal amino acid sequencing of the purified protein revealed the correct sequence, and rabbit polyclonal antisera raised against AS
44–331
reacted specifically to Asc10 expressed from
E. faecalis
OG1SSp, but not to other proteins as judged by Western blot analysis. Using these antisera, flow cytometry analysis demonstrated that antibodies to AS
44–331
bound to a surface-exposed region of Asc10. Furthermore, antibodies specific for AS
44–331
were opsonic for
E. faecalis
expressing Asc10 in vitro but not for cells that did not express Asc10. New Zealand White rabbits immunized with AS
44–331
were challenged intravenously with
E. faecalis
cells constitutively expressing Asc10 in the rabbit model of experimental endocarditis. Highly immune animals did not show significant differences in clearance of organisms from the blood or spleen or in formation of vegetations on the aortic valve, in comparison with nonimmune animals. Although in vivo expression of Asc10 was demonstrated by immunohistochemistry, these experiments provide evidence that immunity to Asc10 does not play a role in protection from experimental infective endocarditis due to
E. faecalis
and may have important implications for the development of immunological approaches to combat enterococcal endocarditis.
Human Peripheral Blood T Cells, Monocytes, and Macrophages Secrete Macrophage Inflammatory Proteins 1α and 1β following Stimulation with Heat-InactivatedBrucella abortus
Authors: Zaitseva Marina , King Lisa R. , Manischewitz Jody , Dougan Michael , Stevan Lee , Golding Hana , Golding Basil 
Published: July 2002

ABSTRACTHeat-killedBrucella abortus(HBa) has been proposed as a carrier for therapeutic vaccines for individuals with immunodeficiency, due to its abilities to induce interleukin-2 (IL-2) and gamma interferon (IFN-γ) in both CD4+and CD8+T cells and to upregulate antigen-presenting cell functions (including IL-12 production). In the current study, we investigated the ability of HBa or lipopolysaccharide isolated from HBa (LPS-Ba) to elicit β-chemokines, known to bind to the human immunodeficiency virus type 1 (HIV-1) coreceptor CCR5 and to block viral cell entry. It was found that human peripheral blood mononuclear cells secreted β-chemokines following stimulation with HBa, and this effect could not be blocked by anti-IFN-γ neutralizing antibodies. Among purified T cells, macrophage inflammatory protein 1α and 1β (MIP-1α and MIP-1β, respectively) secretion was observed primarily in human CD8+T cells. The kinetics of β-chemokine induction in T cells were slow (3 to 4 days). The majority of β-chemokine-producing CD8+T cells also produced IFN-γ following HBa stimulation, as determined by triple-color intracellular staining. A significant number of CD8+T cells contained stored MIP-1β that was released after HBa stimulation. Both HBa and LPS-Ba stimulated high levels of MIP-1α and MIP-1β production in elutriated monocytes and even higher levels in macrophages. In these cells, β-chemokine mRNA was upregulated within 30 min and proteins were secreted within 4 h of stimulation. The monocyte- and macrophage-derived β-chemokines were sufficient to block CCR5-dependent HIV-1 envelope-mediated cell fusion. These data suggest that, in addition to the ability of HBa to elicit antigen-specific humoral and cellular immune responses, HBa-conjugated HIV-1 proteins or peptides would also generate innate chemokines with antiviral activity that could limit local viral spread during vaccination in vivo.
Intracellular Survival ofBrucellaspp. in Human Monocytes Involves Conventional Uptake but Special Phagosomes
Authors: Rittig Michael G. , Alvarez-Martinez Maria-Teresa , Porte Françoise , Liautard Jean-Pierre , Rouot Bruno 
Published: July 2002

ABSTRACTBrucellaspp. are facultative intracellular parasites of various mammals, including humans, typically infecting lymphoid as well as reproductive organs. We have investigated howB. suisandB. melitensisenter human monocytes and in which compartment they survive. Peripheral blood monocytes readily internalized nonopsonized brucellae and killed most of them within 12 to 18 h. The presence ofBrucella-specific antibodies (but not complement) increased the uptake of bacteria without increasing their intracellular survival, whereas adherence of the monocytes or incubation in Ca2+- and Mg2+-free medium reduced the uptake. Engulfment of allBrucellaorganisms (regardless of bacterial viability or virulence) initially resulted in phagosomes with tightly apposed walls (TP). Most TP were fully fusiogenic and matured to spacious phagolysosomes containing degraded bacteria, whereas some TP (more in monocyte-derived macrophages, HeLa cells, and CHO cells than in monocytes) remained tightly apposed to intact bacteria. Immediate treatment of infected host cells with the lysosomotropic base ammonium chloride caused a swelling of all phagosomes and a rise in the intraphagosomal pH, abolishing the intracellular survival ofBrucella. These results indicate that (i) human monocytes readily internalizeBrucellain a conventional way using various phagocytosis-promoting receptors, (ii) the maturation of someBrucellaphagosomes is passively arrested between the steps of acidification and phagosome-lysosome fusion, (iii) brucellae are killed in maturing but not in arrested phagosomes, and (iv) survival of internalizedBrucelladepends on an acidic intraphagosomal pH and/or close contact with the phagosomal wall.
Porphyromonas gingivalis
Traffics to Autophagosomes in Human Coronary Artery Endothelial Cells
Authors: Dorn Brian R. , Dunn William A. , Progulske-Fox Ann 
Published: July 2002

ABSTRACT

Porphyromonas gingivalis
is a periodontal pathogen that also localizes to atherosclerotic plaques. Our previous studies demonstrated that
P. gingivalis
is capable of invading endothelial cells and that intracellular bacteria are contained in vacuoles that resemble autophagosomes. In this study, we have examined the trafficking of
P. gingivalis
381 to the autophagic pathway.
P. gingivalis
381 internalized by human coronary artery endothelial (HCAE) cells is located within vacuoles morphologically identical to autophagosomes. The progression of
P. gingivalis
381 through intracellular vacuoles was analyzed by immunofluorescence microscopy. Vacuoles containing
P. gingivalis
colocalize with Rab5 and HsGsa7p early after internalization. At later times,
P. gingivalis
colocalizes with BiP and then progresses to a vacuole that contains BiP and lysosomal glycoprotein 120. Late endosomal markers and the lysosomal cathepsin L do not colocalize with
P. gingivalis
381. The intracellular survival of
P. gingivalis
381 decreases over 8 h in HCAE cells pretreated with the autophagy inhibitors 3-methyladenine and wortmannin. In addition, the vacuole containing
P. gingivalis
381 lacks BiP but contains cathepsin L in the presence of wortmannin. These results suggest that
P. gingivalis
381 evades the endocytic pathway to lysosomes and instead traffics to the autophagosome.
Chlamydia pneumoniaeSecretion of a Protease-Like Activity Factor for Degrading Host Cell Transcription Factors Is Required for Major Histocompatibility Complex Antigen Expression
Authors: Fan Peiyi , Dong Feng , Huang Yanqing , Zhong Guangming 
Published: July 2002

ABSTRACTChlamydia pneumoniaeis a causative agent for many respiratory infections and has been associated with cardiovascular diseases in humans. The pathogenicity ofC. pneumoniaeis thought to depend on its ability to cause persistent infection and to evade host defense. Genome sequence analysis indicates thatC. pneumoniaeencodes a homologue of a chlamydial protease-like activity factor fromC. trachomatis(CPAFct). We designated theC. pneumoniaehomologue as CPAFcp. Recombinant CPAFcp was produced and found to degrade RFX5, a host transcription factor required for major histocompatibility complex (MHC) antigen expression. The degradation was inhibitable by lactacystin, an irreversible proteasome inhibitor. Furthermore, CPAFcp was secreted into host cytosol byC. pneumoniaeorganisms. Depletion of theC. pneumoniae-secreted CPAFcp with specific antibodies completely ablated the RFX5 degradation activity in the infected cells, suggesting that CPAFcp is necessary for the degradation of host transcription factors required for MHC antigen expression duringC. pneumoniaeinfection. These observations have revealed a unique molecular mechanism forC. pneumoniaeto evade host adaptive immunity that may aid in its persistence.
The Group B Streptococcal C5a Peptidase Is Both a Specific Protease and an Invasin
Authors: Cheng Qi , Stafslien Deborah , Purushothaman Sai Sudha , Cleary Patrick 
Published: July 2002

ABSTRACTThe group B streptococcus (GBS) is a major cause of pneumonia, sepsis, and meningitis in neonates and a serious cause of mortality or morbidity in immunocompromised adults. Although these streptococci adhere efficiently and invade a variety of tissue-specific epithelial and endothelial cells, adhesins and invasins are still unknown. All serotypes of GBS studied to date express C5a peptidase (SCPB) on their surface. This investigation addresses the possibility that this relatively large surface protein has additional activities. Rabbit anti-SCPB serum inhibited invasion of lung epithelial A549 cells by the serotype Ia strain O90R, suggesting that SCPB is an invasin. This was confirmed by inserting an in-frame 25-amino-acid deletion into thescpBgene. Invasion of HEp2 and A549 human cell lines was significantly reduced by the mutation. Enzyme-linked immunosorbent assays were used to demonstrate that purified SCPB protein binds directly to HEp2 and A549 cells and also binds the extracellular matrix protein fibronectin. Binding was dose dependent and saturable. These results suggested that SCPB is one of several potential invasins essential for GBS colonization of damaged epithelium.
The LTR72 Mutant of Heat-Labile Enterotoxin ofEscherichia coliEnhances the Ability of Peptide Antigens To Elicit CD4+T Cells and Secrete Gamma Interferon after Coapplication onto Bare Skin
Authors: Beignon A.-S. , Briand J.-P. , Rappuoli R. , Muller S. , Partidos C. D. 
Published: July 2002

ABSTRACTApplication of antigens with an adjuvant onto bare skin is a needle-free and pain-free immunization procedure that delivers antigens to the immunocompetent cells of the epidermis. We tested here the immunogenicity and adjuvanticity of two mutants of heat-labile enterotoxin (LT) ofEscherichia coli, LTK63 and LTR72. Both mutants were shown to be immunogenic, inducing serum and mucosal antibody responses. The application of LTK63 and LTR72 to bare skin induced significant protection against intraperitoneal challenge with a lethal dose of LT. In addition, both LT mutants enhanced the capacity of peptides TT:830-843 and HA:307-319 (representing T-helper epitopes from tetanus toxin and influenza virus hemagglutinin, respectively) to elicit antigen-specific CD4+T cells after coapplication onto bare skin. However, only mutant LTR72 was capable of stimulating the secretion of high levels of gamma interferon. These findings demonstrate that successful skin immunization protocols require the selection of the right adjuvant in order to induce the appropriate type of antigen-specific immune responses in a selective and reliable way. Moreover, the use of adjuvants such the LTK63 and LTR72 mutants, with no or low residual toxicity, holds a lot of promise for the future application of vaccines to the bare skin of humans.
H-NS-Dependent Regulation of Flagellar Synthesis Is Mediated by a LysR Family Protein
Authors: Ko Minsu , Park Chankyu 
Published: July 2002

ABSTRACT

H-NS regulates the flagellar master operon (
flhDC
) and thus is necessary for flagellation of
Escherichia coli
. However, the molecular mechanism of its regulation has remained unknown. Genetic screening of a transposon insertion abolishing the H-NS effect revealed a previously unidentified gene, named
hdfR
, encoding a LysR family protein. Binding of purified HdfR to the
flhDC
promoter was demonstrated by a DNA mobility shift assay, indicating that HdfR is a transcriptional regulator for the flagellar master operon. Furthermore, the expression of the
hdfR
gene was shown to be negatively regulated by H-NS.
Novel Insertion Sequence Elements Associated with Genetic Heterogeneity and Phenotype Conversion in
Ralstonia solanacearum
Authors: Jeong Eun-Lee , Timmis Jeremy N. 
Published: July 2002

ABSTRACT

Three insertion sequences (IS) elements were isolated from the phytopathogen
Ralstonia solanacearum
. Southern hybridization using these IS elements as probes revealed hybridization profiles that varied greatly between different strains of the pathogen. During a spontaneous phenotype conversion event, the promoter of the
phcA
gene was interrupted by one of these IS elements.
Two Novel Genes Induced by Hard-Surface Contact of
Colletotrichum gloeosporioides
Conidia
Authors: Kim Yeon-Ki , Liu Zhi-Mei , Li Daoxin , Kolattukudy Pappachan E. 
Published: July 2002

ABSTRACT

Germinating conidia of many phytopathogenic fungi must differentiate into an infection structure called the appressorium in order to penetrate into their hosts. This differentiation is known to require contact with a hard surface. However, the molecular basis for this requirement is not known. Induction of this differentiation in the avocado pathogen,
Colletotrichum gloeosporioides
, by chemical signals such as the host's surface wax or the fruit-ripening hormone, ethylene, requires contact of the conidia with a hard surface for about 2 h. To study molecular events triggered by hard-surface contact, we isolated several genes expressed during the early stage of hard-surface treatment by a differential-display method. The genes that encode
Colletotrichum
hard-surface induced proteins are designated
chip
genes. In this study, we report the characterization of
CHIP2
and
CHIP3
genes that would encode proteins with molecular masses of 65 and 64 kDa, respectively, that have no homology to any known proteins. The
CHIP2
product would contain a putative nuclear localization signal, a leucine zipper motif, and a heptad repeat region which might dimerize into coiled-coil structure. The
CHIP3
product would be a nine-transmembrane-domain-containing protein. RNA blots showed that
CHIP2
and
CHIP3
are induced by a 2-h hard-surface contact. However, disruption of these genes did not affect the appressorium-forming ability and did not cause a significant decrease in virulence on avocado or tomato fruits suggesting that
C. gloeosporioides
might have genes functionally redundant to
CHIP2
and
CHIP3
or that these genes induced by hard-surface contact control processes not directly involved in pathogenesis.
ς
70
Is the Principal Sigma Factor Responsible for Transcription of
acs
, Which Encodes Acetyl Coenzyme A Synthetase in
Escherichia coli
Authors: Kumari Suman , Simel Erica J. , Wolfe Alan J. 
Published: July 2002

ABSTRACT

Cells of
Escherichia coli
undergo a metabolic switch associated with the production and utilization of acetate. During exponential growth on tryptone broth, these cells excrete acetate via the phosphotransacetylase-acetate kinase (Pta-AckA) pathway. As they begin the transition to stationary phase, they instead resorb acetate, activate it to acetyl coenzyme A (acetyl-CoA) by means of the enzyme acetyl-CoA synthetase (Acs) and utilize it to generate energy and biosynthetic components via the tricarboxylic acid cycle and the glyoxylate shunt, respectively. This metabolic switch depends upon the induction of Acs. As part of our effort to dissect the mechanism(s) underlying induction and to identify the signal(s) that triggers that induction, we sought the sigma factor most responsible for
acs
expression. Using isogenic strains that carry a temperature sensitivity allele of the gene that encodes ς
70
and either a wild-type or null allele of the gene that encodes ς
S
, we determined by immunoblotting, reverse transcriptase PCR, and
acs
::
lacZ
transcriptional fusion analyses that ς
70
is the sigma factor primarily responsible for the
acs
transcription that cells induce during mid-exponential phase. In contrast, ς
S
partially inhibits that transcription as cells enter stationary phase.
RNA Polymerases from
Bacillus subtilis
and
Escherichia coli
Differ in Recognition of Regulatory Signals In Vitro
Authors: Artsimovitch Irina , Svetlov Vladimir , Anthony Larry , Burgess Richard R. , Landick Robert 
Published: July 2002

ABSTRACT

Adaptation of bacterial cells to diverse habitats relies on the ability of RNA polymerase to respond to various regulatory signals. Some of these signals are conserved throughout evolution, whereas others are species specific. In this study we present a comprehensive comparative analysis of RNA polymerases from two distantly related bacterial species,
Escherichia coli
and
Bacillus subtilis
, using a panel of in vitro transcription assays. We found substantial species-specific differences in the ability of these enzymes to escape from the promoter and to recognize certain types of elongation signals. Both enzymes responded similarly to other pause and termination signals and to the general
E. coli
elongation factors NusA and GreA. We also demonstrate that, although promoter recognition depends largely on the ς subunit, promoter discrimination exhibited in species-specific fashion by both RNA polymerases resides in the core enzyme. We hypothesize that differences in signal recognition are due to the changes in contacts made between the β and β′ subunits and the downstream DNA duplex.
Distribution of the Mosaic Structured
murM
Genes among Natural Populations of
Streptococcus pneumoniae
Authors: Filipe Sergio R. , Severina Elena , Tomasz Alexander 
Published: July 2002

ABSTRACT

The presence and sequence variation of the
murM
gene were studied in a large collection (814 strains) of genetically diverse
Streptococcus pneumoniae
isolates, which included 27 different serogroups and both penicillin-resistant (423 isolates, 67 pulsed-field gel electrophoretic [PFGE] types) and intermediately penicillin-resistant (165 isolates, 66 PFGE types) and penicillin-susceptible (226 isolates, 135 PFGE types) strains. Diversity of the
murM
sequences was tested by hybridization with mainly two kinds of probes: one derived from the amplification of the nucleotide sequence between nucleotides 201 and 624 in the penicillin-susceptible laboratory strain R36A (
murMA
probe) and a second probe that amplified the comparable, highly divergent sequence in the penicillin-resistant strain Pen6 (
murMB
probe). The great majority of the strains (761 of 814), including both penicillin-susceptible and penicillin-resistant isolates, reacted exclusively with the
murMA
probe. A smaller group of penicillin-resistant strains (48 of 814 isolates) reacted only with the
murMB
DNA probe, and an additional 5 isolates reacted with both probes. High-pressure liquid chromatography analysis of the peptidoglycan of strains hybridizing with
murMB
showed that they invariably contained an increased proportion of branched peptides. Complete sequencing of
murM
from a group of penicillin-resistant isolates allowed the identification of a number of different
murMB
alleles that differed in the length and exact position of the divergent (Pen6 type) sequences within the particular
murM
. The close similarity of these divergent sequences in the various
murM
alleles suggests a possible common heterologous origin.