bluuebunny/crossref_metadata_2025_split huggingface dataset:
Demonstration of the Genetic Stability and Temporal Expression of Select Members of the Lyme Disease Spirochete OspF Protein Family during Infection in Mice
Authors: McDowell John V. , Sung Shian Ying , Price Gregory , Marconi Richard T. 
Published: July 2002

ABSTRACT

Infection with Lyme disease spirochetes can be chronic. This suggests that the spirochetes are capable of immune evasion. In a previous study we demonstrated that the
ospE
gene family, which is one of three gene families whose members are flanked at their 5′ end by the highly conserved upstream homology box (UHB) element, undergoes mutation and rearrangement during infection. This results in the generation of antigenically distinct variants that may contribute to immune evasion. In this study we have assessed the genetic stability of the UHB-flanked
ospF
gene family during infection in mice. Using postinfection clonal populations of
Borrelia burgdorferi
B31MI, PCR amplicons were generated for three members of the
ospF
gene family after a 3-month infection time frame. The amplicons were analyzed by single-nucleotide polymorphism pattern analysis and DNA sequencing. Members of the
ospF
gene family were found to be stable during infection, as no mutations or rearrangements were detected. An analysis of the humoral immune response to these proteins during infection revealed that the immune response to each is specific and that there is a delayed humoral immune response to some OspF protein family members. These analyses suggest that there is a temporal component to the expression of these genes during infection. In addition to a possible contribution to immune evasion, members of the OspF protein family may play specific roles at different stages of infection.
Epithelial Intestinal Cell Apoptosis Induced byHelicobacter pyloriDepends on Expression of thecagPathogenicity Island Phenotype
Authors: Le'Negrate Gaëlle , Ricci Vittorio , Hofman Véronique , Mograbi Baharia , Hofman Paul , Rossi Bernard 
Published: July 2002

ABSTRACTHelicobacter pylorihas been shown to induce chronic active gastritis and peptic ulcer and may contribute to the development of duodenal ulcer. Previous studies have shown thatH. pylorimediates apoptosis of gastric epithelial cells via a Fas-dependent pathway. However, evidence for the induction of such a mechanism in intestinal epithelial cells (IEC) byH. pyloriinfection has not been demonstrated yet. This study was performed (i) to ascertain thatH. pylorican induce IEC apoptosis; (ii) to delineate the role of thecagpathogenicity island (PAI),cagE, andvacAgene products in this process; and (iii) to verify whether the Fas-dependent pathway is involved in this phenomenon. When T84 cells were exposed to VacA+/cagPAI+H. pyloristrains (CCUG 17874 and 60190), they exhibited apoptosis hallmarks as assessed by morphological studies, as well as annexin V and 3,3′-dihexyloxacarbocyanine iodide staining. In contrast, few or no apoptotic features could be detected after incubation with an isogenic mutant of strain 60190 in which thecagEgene was disrupted (60190:C−strain) or with a VacA−/cagPAI−H. pyloristrain (G21). In addition, activation of caspase-3 during infection with VacA+/cagPAI+H. pyloristrains was inhibited by pretreatment of IEC with an antagonistic anti-Fas antibody (ZB4). Taken together, these findings indicate thatH. pyloritriggers apoptosis in IEC via a Fas-dependent pathway following a process that depends on the expression of thecagPAI.
Escherichia coli
Hemoglobin Protease Autotransporter Contributes to Synergistic Abscess Formation and Heme-Dependent Growth of
Bacteroides fragilis
Authors: Otto Ben R. , van Dooren Silvy J. M. , Dozois Charles M. , Luirink Joen , Oudega Bauke 
Published: July 2002

ABSTRACT

Intra-abdominal infections (IAI) continue to be a serious clinical problem. Bacterial synergism is an important factor that influences the shift from contamination to IAI, leading to the development of lesions and abscess formation.
Escherichia coli
and
Bacteroides fragilis
are particularly abundant in IAI. The underlying molecular mechanisms of this pathogenic synergy are still unclear. The role of the hemoglobin protease (Hbp) autotransporter protein from
E. coli
in the synergy of IAI was investigated. Hbp is identical to Tsh, a temperature-sensitive hemagglutinin associated with avian pathogenic
E. coli
. Clinical isolates from miscellaneous extraintestinal infections were phenotypically and genotypically screened for Hbp. The presence of Hbp was significantly associated with
E. coli
isolated from IAI and other extraintestinal infections. In a murine infection model, Hbp was shown to contribute to the pathogenic synergy of abscess development. Mice immunized with Hbp were protected against mixed infections and did not develop abscess lesions. Furthermore, an
E. coli
wild-type strain that did not induce abscess formation in the synergy model was transformed with a plasmid encoding the
hbp
gene, and mixed infections with this strain lead to increased growth of
B. fragilis
and induction of abscess lesions. Growth-promoting studies showed that purified Hbp is able to deliver heme to
B. fragilis
strain BE1. In conclusion, results suggest the synergy of abscess formation by
E. coli
and
B. fragilis
can be partly explained by the capacity of
B. fragilis
to intercept Hbp and iron from heme to overcome the iron restrictions imposed by the host.
Expression of Major Surface Protein 2 Variants with Conserved T-Cell Epitopes in
Anaplasma centrale
Vaccinates
Authors: Shkap Varda , Molad Thea , Brayton Kelly A. , Brown Wendy C. , Palmer Guy H. 
Published: July 2002

ABSTRACT

Major surface protein 2 (MSP-2), identified as a protection-inducing immunogen against
Anaplasma marginale
challenge, is an immunodominant outer membrane protein with orthologues in all examined
Anaplasma
species. Although immunization with live
Anaplasma centrale
has long been used to induce protection against acute disease upon challenge with virulent
A. marginale
, its MSP-2 structure and whether MSP-2 variants are generated during persistence of the vaccine strain was unknown. In this study, we showed that the
A. centrale
vaccine strain persisted for a minimum of 4 years postvaccination and generated sequential MSP-2 variants. Comparison of amino acid sequences encoded by
A. centrale msp-2
transcripts from the initial postimmunization period and from sequential time points during persistence of the vaccine strain revealed a central hypervariable domain flanked by conserved amino and carboxy-terminal regions. This structure corresponded to that shown in
A. marginale
MSP-2, where the central hypervariable region encodes variant B-cell epitopes in the extracellular domain and the flanking transmembrane domains are rich in CD4
+
-T-cell epitopes. Importantly, at least four CD4
+
-T-cell epitopes are conserved between the two species, a finding consistent with
A. marginale
challenge triggering a recall response of CD4
+
T cells induced by
A. centrale
vaccination. The genomic arrangement is conserved between
A. centrale
and
A. marginale
with multiple
msp-2
pseudogenes and a single operon-linked expression site for the full-length
msp-2
. This conservation of both genomic structure for generating MSP-2 variants and the CD4
+
-T-cell epitopes between these two genetically distinct
Anaplasma
species indicates that they present a similar repertoire of MSP-2 epitopes to the immune system and that this similarity may be responsible for all or part of the
A. centrale
vaccine efficacy.
Inactivation of the
Moraxella catarrhalis
Superoxide Dismutase SodA Induces Constitutive Expression of Iron-Repressible Outer Membrane Proteins
Authors: Luke Nicole R. , Karalus Richard J. , Campagnari Anthony A. 
Published: July 2002

ABSTRACT

Many pathogens produce one or more superoxide dismutases (SODs), enzymes involved in the detoxification of endogenous and exogenous reactive oxygen species that are encountered during the infection process. One detectable cytoplasmic SOD was identified in the human mucosal pathogen
Moraxella catarrhalis
, and the gene responsible for the SOD activity,
sodA
, was isolated from a recent pediatric clinical isolate (strain 7169). Sequence analysis of the cloned
M. catarrhalis
7169 DNA fragment revealed an open reading frame of 618 bp encoding a polypeptide of 205 amino acids with 48 to 67% identity to known bacterial manganese-cofactored SODs. An isogenic
M. catarrhalis sodA
mutant was constructed in strain 7169 by allelic exchange. In contrast to the wild-type 7169, the 7169::sodK20 mutant was severely attenuated for aerobic growth, even in rich medium containing supplemental amino acids, and exhibited extreme sensitivity to the redox-active agent methyl viologen. The ability of recombinant SodA to rescue the aerobic growth defects of
E. coli
QC774, a
sodA sodB
-deficient mutant, demonstrated the functional expression of SOD activity by cloned
M. catarrhalis sodA
. Indirect SOD detection assays were used to visualize both native and recombinant SodA activity in bacterial lysates. This study demonstrates that
M. catarrhalis
SodA plays a critical role in the detoxification of endogenous, metabolically produced oxygen radicals. In addition, the outer membrane protein (OMP) profile of 7169::sodK20 was consistent with iron starvation in spite of growth under iron-replete conditions. This novel observation indicates that
M. catarrhalis
strains lacking SodA constitutively express immunogenic OMPs previously described as iron repressible, and this potentially attenuated mutant strain may be an attractive vaccine candidate.
Cortactin Is Necessary for F-Actin Accumulation in Pedestal Structures Induced by Enteropathogenic
Escherichia coli
Infection
Authors: Cantarelli Vlademir V. , Takahashi Akira , Yanagihara Itaru , Akeda Yukihiro , Imura Kinichi , Kodama Toshio , Kono Gengo , Sato Yoshihisa , Iida Tetsuya , Honda Takeshi 
Published: July 2002

ABSTRACT

Cortactin and the translocated intimin receptor, Tir, interacted with each other in pedestal formation in HeLa cells infected with enteropathogenic
Escherichia coli
(EPEC). Cortactin is shown to be necessary for organizing actin pedestals in response to EPEC, based on the expression of green fluorescent protein-fused cortactin derivatives in HeLa cells.
Gel Shift Assay of Nuclear Extracts from
Histoplasma capsulatum
Demonstrates the Presence of Several DNA Binding Proteins
Authors: Ignatov Atanas , Keath Elizabeth J. 
Published: July 2002

ABSTRACT

A gel shift assay was optimized to detect several general DNA binding proteins from
Histoplasma capsulatum
strain G217B. The electrophoretic mobility shift assay (EMSA) technique also detected protein(s) recognizing a pyrimidine-rich motif found in several
Histoplasma
promoters. Establishment of EMSA conditions provides an important framework to evaluate regulation of homeostatic or phase-specific genes that may influence virulence in
Histoplasma
and other dimorphic fungal pathogens.
A DNA Vaccine Encoding Lumazine Synthase fromBrucella abortusInduces Protective Immunity in BALB/c Mice
Authors: Velikovsky Carlos A. , Cassataro Juliana , Giambartolomei Guillermo H. , Goldbaum Fernando A. , Estein Silvia , Bowden Raul A. , Bruno Laura , Fossati Carlos A. , Spitz Moisés 
Published: July 2002

ABSTRACTThis study was conducted to evaluate the immunogenicity of theBrucella abortuslumazine synthase (BLS) gene cloned into the pcDNA3 plasmid, which is driven by the cytomegalovirus promoter. Injection of plasmid DNA carrying the BLS gene (pcDNA-BLS) into BALB/c mice elicited both humoral and cellular immune responses. Antibodies to the encoded BLS included immunoglobulin G1 (IgG1) IgG2a, IgG2b, IgG3, and IgM isotypes. Animals injected with pcDNA-BLS exhibited a dominance of IgG2a over IgG1. In addition, spleen cells from vaccinated animals produced interleukin-2 and gamma interferon but not IL-10 or IL-4 after in vitro stimulation with recombinant BLS (rBLS), suggesting the induction of a Th1 response. Protection was evaluated by comparing the levels of infection in the spleens of vaccinated mice challenged withB. abortus544. Immunization with pcDNA-BLS- reduced the bacterial burden relative to those in the control groups. Mice immunized with rBLS produced a significant humoral response but did not show a specific cellular response or any protection from challenge. Altogether, these data suggest that pcDNA-BLS is a good immunogen for the production of humoral and cell-mediated responses in mice and is a candidate for use in future studies of vaccination against brucellosis.
Differential Persistence among Genomovars of theBurkholderia cepaciaComplex in a Murine Model of Pulmonary Infection
Authors: Chu Karen K. , Davidson Donald J. , Halsey T. Keith , Chung Jacqueline W. , Speert David P. 
Published: July 2002

ABSTRACTCystic fibrosis patients infected with strains from different genomovars of theBurkholderia cepaciacomplex can experience diverse clinical outcomes. To identify genomovar-specific determinants that might be responsible for these differences, we developed a pulmonary model of infection in BALB/c mice. Mice were rendered leukopenic by administration of cyclophosphamide prior to intranasal challenge with 1.6 × 104bacteria. Five of six genomovar II strains persisted at stable numbers in the lungs until day 16 with minimal toxicity, whereas zero of seven genomovar III strains persisted but resulted in variable toxicity. We have developed a chronic pulmonary model ofB. cepaciainfection which reveals differences among genomovars in terms of clinical infection outcome.
Borrelia burgdorferi
Population Kinetics and Selected Gene Expression at the Host-Vector Interface
Authors: Hodzic Emir , Feng Sunlian , Freet Kimberly J. , Borjesson Dori L. , Barthold Stephen W. 
Published: July 2002

ABSTRACT

By using real-time quantitative PCR, the population dynamics and gene transcription of
Borrelia burgdorferi
were examined in ticks and skin of mice during acquisition of the infection from mice by ticks and during transmission of the infection from ticks to mice. Population dynamics were determined by using a
flaB
DNA target. A quantitative analysis of
flaB
,
ospA
,
ospC
,
dbpA
, and
arp
transcription was also performed. The results revealed that both uninfected larval and nymphal
Ixodes scapularis
ticks acquired
B. burgdorferi
as early as 1 day after attachment and that the sizes of spirochete populations within ticks increased during feeding. In addition, all gene targets revealed that there was RNA transcription during feeding. Similar events occurred within infected nymphal ticks feeding on uninfected hosts. Transmission from infected nymphal ticks to mice could be detected within 1 day after attachment. Analysis of skin during the first 3 days after attachment of infected ticks revealed rising numbers of spirochetes but minimal gene transcription. In contrast, the skin of mice with established infections revealed static populations of spirochetes and active but stable transcription of
flaB
,
ospC
,
dbpA
, and
arp
. There were consistent reductions in the number of spirochetes in the skin at the tick attachment sites compared to the number of spirochetes in the skin at nontick sites, but there were no differences in gene expression between tick and nontick skin sites. Evidence of
ospA
transcription in skin could be found 1 day after tick attachment but not thereafter.
Characterization of
Salmonella enterica
Derivatives Harboring Defined
aroC
and
Salmonella
Pathogenicity Island 2 Type III Secretion System (
ssaV
) Mutations by Immunization of Healthy Volunteers
Authors: Hindle Zoë , Chatfield Steven N. , Phillimore Jo , Bentley Matthew , Johnson Julie , Cosgrove Catherine A. , Ghaem-Maghami Marjan , Sexton Amy , Khan Mohammad , Brennan Frank R. , Everest Paul , Wu Tao , Pickard Derek , Holden David W. , Dougan Gordon , Griffin George E. , House Deborah , Santangelo Joseph D. , Khan Shahid A. , Shea Jaqueline E. , Feldman Robert G. , Lewis David J. M. 
Published: July 2002

ABSTRACT

The attenuation and immunogenicity of two novel
Salmonella
vaccine strains,
Salmonella enterica
serovar Typhi (Ty2 Δ
aroC
Δ
ssaV
, designated ZH9) and
S. enterica
serovar Typhimurium (TML Δ
aroC
Δ
ssaV
, designated WT05), were evaluated after their oral administration to volunteers as single escalating doses of 10
7
, 10
8
, or 10
9
CFU. ZH9 was well tolerated, not detected in blood, nor persistently excreted in stool. Six of nine volunteers elicited anti-serovar Typhi lipopolysaccharide (LPS) immunoglobulin A (IgA) antibody-secreting cell (ASC) responses, with three of three vaccinees receiving 10
8
and two of three receiving 10
9
CFU which elicited high-titer LPS-specific serum IgG. WT05 was also well tolerated with no diarrhea, although the administration of 10
8
and 10
9
CFU resulted in shedding in stools for up to 23 days. Only volunteers immunized with 10
9
CFU of WT05 mounted detectable serovar Typhimurium LPS-specific ASC responses and serum antibody responses were variable. These data indicate that mutations in type III secretion systems may provide a route to the development of live vaccines in humans and highlight significant differences in the potential use of serovars Typhimurium and Typhi.
Color-Sensitive Motility and Methanol Release Responses in
Rhodobacter sphaeroides
Authors: Kort Remco , Crielaard Wim , Spudich John L. , Hellingwerf Klaas J. 
Published: July 2002

ABSTRACT

Blue-light-induced repellent and demethylation responses, characteristic of behavioral adaptation, were observed in
Rhodobacter sphaeroides
. They were analyzed by computer-assisted motion analysis and through the release of volatile tritiated compounds from [
methyl
-
3
H]methionine-labeled cells, respectively. Increases in the stop frequency and the rate of methanol release were induced by exposure of cells to repellent light signals, such as an increase in blue- and a decrease in infrared-light intensity. At a λ of >500 nm the amplitude of the methanol release response followed the absorbance spectrum of the photosynthetic pigments, suggesting that they function as photosensors for this response. In contrast to the previously reported motility response to a decrease in infrared light, the blue-light response reported here does not depend on the number of photosynthetic pigments per cell, suggesting that it is mediated by a separate sensor. Therefore, color discrimination in taxis responses in
R. sphaeroides
involves two photosensing systems: the photosynthetic pigments and an additional photosensor, responding to blue light. The signal generated by the former system could result in the migration of cells to a light climate beneficial for photosynthesis, while the blue-light system could allow cells to avoid too-high intensities of (harmful) blue light.
Vibrio vulnificus
Has the Transmembrane Transcription Activator ToxRS Stimulating the Expression of the Hemolysin Gene
vvhA
Authors: Lee Shee Eun , Shin Sung Heui , Kim Soo Young , Kim Young Ran , Shin Dong Hyeon , Chung Sun Sik , Lee Zang Hee , Lee Jee Yeon , Jeong Kwang Choel , Choi Sang Ho , Rhee Joon Haeng 
Published: July 2002

ABSTRACT

In an attempt to dissect the virulence regulatory mechanism in
Vibrio vulnificus
, we tried to identify the
V. cholerae
transmembrane virulence regulator
toxRS
(
toxRS
Vc
) homologs in
V. vulnificus
. By comparing the sequences of
toxRS
of
V. cholerae
and
V. parahaemolyticus
(
toxRS
Vp
), we designed a degenerate primer set targeting well-conserved sequences. Using the PCR product as an authentic probe for Southern blot hybridization, a 1.6-kb
Bgl
II-
Hin
dIII fragment and a 1.2-kb
Hin
dIII fragment containing two complete open reading frames and one partial open reading frame attributable to
toxR
Vv
,
toxS
Vv
, and
htpG
Vv
were cloned. ToxR
Vv
shared 55.0 and 63.0% sequence homology with ToxR
Vc
and ToxR
Vp
, respectively. ToxS
Vv
was 71.5 and 65.7% homologous to ToxS
Vc
and ToxS
Vp
, respectively. The amino acid sequences of ToxRS
Vv
showed transmembrane and activity domains similar to those observed in ToxRS
Vc
and ToxRS
Vp
. Western blot analysis proved the expression of ToxR
Vv
in
V. vulnificus
. ToxRS
Vv
enhanced, in an
Escherichia coli
background, the expression of the
V. vulnificus
hemolysin gene (
vvhA
) fivefold. ToxRS
Vv
also activated the ToxR
Vc
-regulated
ctx
promoter incorporated into an
E. coli
chromosome. A
toxR
Vv
null mutation decreased hemolysin production. The defect in hemolysin production could be complemented by a plasmid harboring the wild-type gene. The
toxR
Vv
mutation also showed a reversed outer membrane protein expression profile in comparison to the isogenic wild-type strain. These results demonstrate that ToxR
Vv
may regulate the virulence expression of
V. vulnificus
.
Alfalfa Root Nodule Invasion Efficiency Is Dependent on
Sinorhizobium meliloti
Polysaccharides
Authors: Pellock Brett J. , Cheng Hai-Ping , Walker Graham C. 
Published: July 2002

ABSTRACT

The soil bacterium
Sinorhizobium meliloti
is capable of entering into a nitrogen-fixing symbiosis with
Medicago sativa
(alfalfa). Particular low-molecular-weight forms of certain polysaccharides produced by
S. meliloti
are crucial for establishing this symbiosis. Alfalfa nodule invasion by
S. meliloti
can be mediated by any one of three symbiotically important polysaccharides: succinoglycan, EPS II, or K antigen (also referred to as KPS). Using green fluorescent protein-labeled
S. meliloti
cells, we have shown that there are significant differences in the details and efficiencies of nodule invasion mediated by these polysaccharides. Succinoglycan is highly efficient in mediating both infection thread initiation and extension. However, EPS II is significantly less efficient than succinoglycan at mediating both invasion steps, and K antigen is significantly less efficient than succinoglycan at mediating infection thread extension. In the case of EPS II-mediated symbioses, the reduction in invasion efficiency results in stunted host plant growth relative to plants inoculated with succinoglycan or K-antigen-producing strains. Additionally, EPS II- and K-antigen-mediated infection threads are 8 to 10 times more likely to have aberrant morphologies than those mediated by succinoglycan. These data have important implications for understanding how
S. meliloti
polysaccharides are functioning in the plant-bacterium interaction, and models are discussed.
Global Gene Expression Profiles of
Bacillus subtilis
Grown under Anaerobic Conditions
Authors: Ye Rick W. , Tao Wang , Bedzyk Laura , Young Thomas , Chen Mario , Li Liao 
Published: July 2002

ABSTRACT

Bacillus subtilis
can grow under anaerobic conditions, either with nitrate or nitrite as the electron acceptor or by fermentation. A DNA microarray containing 4,020 genes from this organism was constructed to explore anaerobic gene expression patterns on a genomic scale. When mRNA levels of aerobic and anaerobic cultures during exponential growth were compared, several hundred genes were observed to be induced or repressed under anaerobic conditions. These genes are involved in a variety of cell functions, including carbon metabolism, electron transport, iron uptake, antibiotic production, and stress response. Among the highly induced genes are not only those responsible for nitrate respiration and fermentation but also those of unknown function. Certain groups of genes were specifically regulated during anaerobic growth on nitrite, while others were primarily affected during fermentative growth, indicating a complex regulatory circuitry of anaerobic metabolism.