bluuebunny/crossref_metadata_2025_split huggingface dataset:
Profiling of Temperature-Induced Changes inBorrelia burgdorferiGene Expression by Using Whole Genome Arrays
Authors: Ojaimi Caroline , Brooks Chad , Casjens Sherwood , Rosa Patricia , Elias Abdallah , Barbour Alan , Jasinskas Algis , Benach Jorge , Katona Laura , Radolf Justin , Caimano Melissa , Skare Jon , Swingle Kristen , Akins Darrin , Schwartz Ira 
Published: March 2003

ABSTRACTBorrelia burgdorferiis the etiologic agent of Lyme disease, the most prevalent arthropod-borne disease in the United States. The genome of the type strain, B31, consists of a 910,725-bp linear chromosome and 21 linear and circular plasmids comprising 610,694 bp. During its life cycle, the spirochete exists in distinctly different environments, cycling between a tick vector and a mammalian host. Temperature is one environmental factor known to affectB. burgdorferigene expression. To identify temperature-responsive genes, genome arrays containing 1,662 putativeB. burgdorferiopen reading frames (ORFs) were prepared on nylon membranes and employed to assess gene expression inB. burgdorferiB31 grown at 23 and 35°C. Differences in expression of more than 3.5 orders of magnitude could be readily discerned and quantitated. At least minimal expression from 91% of the arrayed ORFs could be detected. A total of 215 ORFs were differentially expressed at the two temperatures; 133 were expressed at significantly greater levels at 35°C, and 82 were more significantly expressed at 23°C. Of these 215 ORFs, 134 are characterized as genes of unknown function. One hundred thirty-six (63%) of the differentially expressed genes are plasmid encoded. Of particular interest is plasmid lp54 which contains 76 annotated putative genes; 31 of these exhibit temperature-regulated expression. These findings underscore the important role plasmid-encoded genes may play in adjustment ofB. burgdorferito growth under diverse environmental conditions.
Expression of Multiple Outer Membrane Protein Sequence Variants from a Single Genomic Locus of
Anaplasma phagocytophilum
Authors: Barbet A. F. , Meeus P. F. M. , Bélanger M. , Bowie M. V. , Yi J. , Lundgren A. M. , Alleman A. R. , Wong S. J. , Chu F. K. , Munderloh U. G. , Jauron S. D. 
Published: March 2003

ABSTRACT

Anaplasma phagocytophilum
is the causative agent of an emerging tick-borne zoonosis in the United States and Europe. The organism causes a febrile illness accompanied by other nonspecific symptoms and can be fatal, especially if treatment is delayed. Persistence of
A. phagocytophilum
within mammalian reservoir hosts is important for ensuring continued disease transmission. In the related organism
Anaplasma marginale
, persistence is associated with antigenic variation of the immunoprotective outer membrane protein MSP2. Extensive diversity of MSP2 is achieved by combinatorial gene conversion of a genomic expression site by truncated pseudogenes. The major outer membrane protein of
A. phagocytophilum
, MSP2(P44), is homologous to MSP2 of
A. marginale
, has a similar organization of conserved and variable regions, and is also encoded by a multigene family containing some truncated gene copies. This suggests that the two organisms could use similar mechanisms to generate diversity in outer membrane proteins from their small genomes. We define here a genomic expression site for MSP2(P44) in
A. phagocytophilum
. As in
A. marginale
, the
msp2
(
p44
) gene in this expression site is polymorphic in all populations of organisms we have examined, whether organisms are obtained from in vitro culture in human HL-60 cells, from culture in the tick cell line ISE6, or from infected human blood. Changes in culture conditions were found to favor the growth and predominance of certain
msp2
(
p44
) variants. Insertions, deletions, and substitutions in the region of the genomic expression site encoding the central hypervariable region matched sequence polymorphisms in
msp2
(
p44
) mRNA. These data suggest that, similarly to
A. marginale
,
A. phagocytophilum
uses combinatorial mechanisms to generate a large array of outer membrane protein variants. Such gene polymorphism has profound implications for the design of vaccines, diagnostic tests, and therapy.
Role of Antibodies in Immunity to
Bordetella
Infections
Authors: Kirimanjeswara Girish S. , Mann Paul B. , Harvill Eric T. 
Published: March 2003

ABSTRACT

The persistence of
Bordetella
pertussis
and
B
.
parapertussis
within vaccinated populations and the reemergence of associated disease highlight the need to better understand protective immunity. The present study examined host immunity to bordetellae and addressed potential concerns about the mouse model by using a comparative approach including the closely related mouse pathogen
B
.
bronchiseptica
. As previously observed with
B
.
pertussis
, all three organisms persisted throughout the respiratory tracts of B-cell-deficient mice, indicating that B cells are required for bacterial clearance. However, adoptively transferred antibodies rapidly cleared
B
.
bronchiseptica
but not human pathogens. These results obtained with the mouse model are consistent with human clinical observations, including the lack of correlation between antibody titers and protection, as well as the limited efficacy of intravenous immunoglobulin treatments against human disease. Together, this evidence suggests that the mouse model accurately reflects substantial differences between immunities to these organisms. Although both
B
.
pertussis
and
B
.
parapertussis
are more closely related to
B
.
bronchiseptica
than they are to each other, they share the ability to resist rapid clearance from the lower respiratory tract by adoptively transferred antibodies, an adaptation that correlates with their emergence as human pathogens that circulate within vaccinated populations.
Differential Modulation by Ca
2+
of Type III Secretion of Diffusely Adhering Enteropathogenic
Escherichia coli
Authors: Ide Tina , Michgehl Silke , Knappstein Sabine , Heusipp Gerhard , Schmidt M. Alexander 
Published: March 2003

ABSTRACT

Enteropathogenic
Escherichia coli
(EPEC) strains are a common cause of persistent diarrhea among infants, primarily in developing countries. The pathogenicity of EPEC is associated with the expression and secretion of bacterial proteins encoded by the chromosomal locus of enterocyte effacement (LEE). The LEE-encoded type III-secreted proteins EspA, EspB, and EspD are part of a molecular syringe, which is used by EPEC to translocate effector proteins directly into the cytoplasm of host cells. The type III-secreted translocated intimin receptor (Tir) protein is thought to be delivered by an Esp-dependent mechanism into the host cell, and this is followed by insertion into the host plasma membrane, where the protein serves as the receptor for intimin, an afimbrial bacterial adhesin. Type III secretion is subject to environmental regulation, and secretion can be induced in vitro by growing bacteria in cell culture medium. In this study we found that Ca
2+
is involved in the regulation of type III secretion both in classical locally adherent EPEC and in atypical diffusely adherent EPEC. Interestingly, we observed contrasting secretion of Esp proteins and Tir in response to Ca
2+
. While the secretion of Tir is clearly enhanced and the protein is integrated into HeLa membranes under calcium chelation conditions, Esp secretion is strongly reduced under these conditions. These data suggest that under Ca
2+
-depleted conditions Tir might be secreted into the medium and integrated into host membranes by an Esp-independent mechanism, without the need for a functional type III translocation machinery.
Modification in the
ppk
Gene of
Helicobacter
pylori
during Single and Multiple Experimental Murine Infections
Authors: Ayraud Sarah , Janvier Blandine , Salaun Laurence , Fauchère Jean-Louis 
Published: March 2003

ABSTRACT

The bacterial pathogen
Helicobacter
pylori
is highly adapted to the human stomach, and a high level of polymorphism is observed among clinical isolates. This polymorphism may be the consequence of adaptive changes during colonization, making a strain better able to survive, to evade the immune system, and to provoke a chronic infection. To investigate the mechanisms involved in the acquisition of diversity in
H
.
pylori
, mouse models of single infections, coinfections, and superinfections were developed. These experimental infections were conducted with strain SS1, well known to be mouse adapted, and with two strains freshly isolated from infected patients: Hp141 and Hp145. Genetic modifications occurring in these strains were studied over time by comparing randomly selected colonies of the emerging strains to those of the infecting strains by using randomly amplified polymorphic DNA fingerprinting with six different primers and by using PCR to amplify the
vacA
and
cagA
genes. We showed that, regardless of the number of infecting strains, only one emerged from the animals and that the establishment of a first strain thwarted the implantation of a second strain. During both a single infection and a coinfection with SS1, Hp141 was replaced by a genetic variant (Hp141v) that overcame SS1 in coinfection experiments. Hp141v exhibited a deletion of a 102-bp repeated sequence within the
ppk
gene, which encodes polyphosphate kinase (PPK), an enzyme involved in the physiological adaptation of the microbial cell to nutritional and environmental stresses. The deletion led to higher enzymatic activity of PPK, and the variant exhibited a better capacity to colonize mice. Considering that the modified gene is known to be involved in adaptation to a new environment, our results are consistent with an adaptive change in strain Hp141 and suggest that PPK is an important virulence factor in
H
.
pylori
.
Cholera Toxin and Its B Subunit Promote Dendritic Cell Vaccination with Different Influences on Th1 and Th2 Development
Authors: Eriksson Kristina , Fredriksson Margareta , Nordström Inger , Holmgren Jan 
Published: March 2003

ABSTRACTCholera toxin (CT) is a strong mucosal adjuvant for codelivered antigens, whereas its nontoxic B subunit (CTB) is an efficient mucosal carrier molecule for the generation of immune responses to linked antigens. We investigated the effects of CT and CTB on the immunogenicity of in vitro-treated antigen-pulsed dendritic cells (DC) following intravenous injection into mice. Prior to infusion, DC were pulsed for 90 min with either free ovalbumin (OVA), OVA mixed with CT or CTB, or chemical conjugates of OVA with CT and CTB (OVA-CT and OVA-CTB). DC pulsed with OVA or with OVA and CTB gave rise to modest antibody and T-cell responses. Conjugation of OVA with CTB enhanced both the subsequent B-cell and T-cell responses to OVA and preferentially induced Th2 responses. CT was shown to be a strong adjuvant when it was coadministered to DC with OVA and was even stronger when it was coadministered with OVA-CTB and primed for a mixed Th1-Th2 response. The antibody and T-cell responses were further enhanced if OVA was coupled to CT, implying that CT can utilize a combined carrier and adjuvant function vis-a-vis linked antigens for DC vaccination. The immunopotentiating capacity of CT- and CTB-linked antigen was associated with both upregulated secretion of interleukin-1β by the pulsed DC and increased expression of CD80 and CD86 on the DC surface. These results imply that CT and CTB can be used to both markedly increase and partially direct the DC vaccine-induced immune response with respect to Th1 and Th2 responses, which has obvious implications for DC-based vaccine development.
Induction of Protective Immunity toListeria monocytogeneswith Dendritic Cells Retrovirally Transduced with a Cytotoxic T Lymphocyte Epitope Minigene
Authors: Nakamura Yutaro , Suda Takafumi , Nagata Toshi , Aoshi Taiki , Uchijima Masato , Yoshida Atsushi , Chida Kingo , Koide Yukio , Nakamura Hirotoshi 
Published: March 2003

ABSTRACTIn the present study, we developed a cytotoxic T lymphocyte (CTL) epitope minigene-transduced dendritic cell (DC)-based vaccine againstListeria monocytogenes. Murine bone marrow-derived DCs were retrovirally transduced with a minigene for listeriolysin O (LLO) 91-99, a dominant CTL epitope ofL. monocytogenes, and were injected into BALB/c mice intravenously. We found that the DC vaccine was capable of generating peptide-specific CD8+T cells exhibiting LLO 91-99-specific cytotoxic activity and gamma interferon production, leading to induction of protective immunity to the bacterium. Furthermore, we demonstrated that the retrovirally transduced DC vaccine was more effective than a CTL epitope peptide-pulsed DC vaccine and a minigene DNA vaccine for eliciting antilisterial immunity. These results provide an alternative strategy in which retrovirally transduced DCs are used to design vaccines against intracellular pathogens.
Helicobacter
pylori
-
Specific CD4
+
CD25
high
Regulatory T Cells Suppress Memory T-Cell Responses to
H
.
pylori
in Infected Individuals
Authors: Lundgren Anna , Suri-Payer Elisabeth , Enarsson Karin , Svennerholm Ann-Mari , Lundin B. Samuel 
Published: March 2003

ABSTRACT

Helicobacter
pylori
colonizes the gastric and duodenal mucosa. The infection normally persists for life and causes peptic ulcers and gastric cancer in a subset of infected individuals. We hypothesized that the inability to clear the infection may be a consequence of
H
.
pylori
-specific regulatory T cells that actively suppress T-cell responses. Therefore, we characterized the T-cell responses to
H
.
pylori
in
H
.
pylori
-infected individuals without any subjective symptoms and in uninfected control subjects and investigated the role of regulatory CD4
+
CD25
high
T cells during infection. The stimulation of CD4
+
peripheral blood T cells with monocyte-derived dendritic cells pulsed with a membrane preparation of
H
.
pylori
resulted in proliferation and gamma interferon production in both infected and uninfected individuals. Sorted memory cells from infected individuals responded less than cells from uninfected subjects, and the unresponsiveness could be abolished by depletion of CD4
+
CD25
high
regulatory T cells or the addition of interleukin 2. Furthermore, CD4
+
CD25
high
T cells suppressed
H
.
pylori
-induced responses in cocultures with CD25
low/−
cells. Tetanus toxoid induced comparable responses in memory cells from infected and uninfected individuals in both the presence and the absence of regulatory T cells, suggesting that the suppression was
H
.
pylori
specific. In conclusion, we have shown that
H
.
pylori
-infected individuals have impaired memory CD4
+
T-cell responses to
H
.
pylori
that are linked to the presence of
H
.
pylori
-specific regulatory T cells that actively suppress the responses.
Differential Effects of Control and Antigen-Specific T Cells on Intracellular Mycobacterial Growth
Authors: Worku S. , Hoft D. F. 
Published: March 2003

ABSTRACTWe investigated the effects of peripheral blood mononuclear cells expanded with irrelevant control and mycobacterial antigens on the intracellular growth ofMycobacterium bovisbacillus Calmette-Guérin (BCG) in human macrophages. More than 90% of the cells present after 1 week of in vitro expansion were CD3+. T cells were expanded from purified protein derivative-negative controls, persons with latent tuberculosis, and BCG-vaccinated individuals. T cells expanded with nonmycobacterial antigens enhanced the intracellular growth of BCG in suboptimal cultures of macrophages. T cells expanded with live BCG or lysates ofMycobacterium tuberculosisdirectly inhibited intracellular BCG. Recent intradermal BCG vaccination significantly enhanced the inhibitory activity of T cells expanded with mycobacterial antigens (P< 0.02), consistent with the induction of memory-immune inhibitory T-cell responses. Selected mycobacterial antigens (Mtb41 > lipoarabinomannan > 38kd > Ag85B > Mtb39) expanded inhibitory T cells, demonstrating the involvement of antigen-specific T cells in intracellular BCG inhibition. We studied the T-cell subsets and molecular mechanisms involved in the memory-immune inhibition of intracellular BCG. Mycobacteria-specific γδ T cells were the most potent inhibitors of intracellular BCG growth. Direct contact between T cells and macrophages was necessary for the BCG growth-enhancing and inhibitory activities mediated by control and mycobacteria-specific T cells, respectively. Increases in tumor necrosis factor alpha, interleukin-6, transforming growth factor β, and vascular endothelial growth factor mRNA expression were associated with the enhancement of intracellular BCG growth. Increases in gamma interferon, FAS, FAS ligand, perforin, granzyme, and granulysin mRNA expression were associated with intracellular BCG inhibition. These culture systems provide in vitro models for studying the opposing T-cell mechanisms involved in mycobacterial survival and protective host immunity.
Afa/Dr Diffusely AdheringEscherichia coliInfection in T84 Cell Monolayers Induces Increased Neutrophil Transepithelial Migration, Which in Turn Promotes Cytokine-Dependent Upregulation of Decay-Accelerating Factor (CD55), the Receptor for Afa/Dr Adhesins
Authors: Bétis Fréderic , Brest Patrick , Hofman Véronique , Guignot Julie , Kansau Imad , Rossi Bernard , Servin Alain , Hofman Paul 
Published: March 2003

ABSTRACTUlcerative colitis and Crohn's disease are inflammatory bowel diseases thought to involve strains ofEscherichia coli. We report here that two wild-type Afa/Dr diffusely adheringE. coli(DAEC) strains, C1845 and IH11128, which harbor the fimbrial F1845 adhesin and the Dr hemagglutinin, respectively, and theE. colilaboratory strain HB101, transformed with the pSSS1 plasmid to produce Afa/Dr F1845 adhesin, all induced interleukin-8 (IL-8) production and transepithelial migration of polymorphonuclear leukocytes (PMNL) in polarized monolayers of the human intestinal cell line T84 grown on semipermeable filters. We observed that after PMNL migration, expression of decay-accelerating factor (DAF, or CD55), the brush border-associated receptor for Afa/Dr adhesins, was strongly enhanced, increasing the adhesion of Afa/Dr DAEC bacteria. When examining the mechanism by which DAF expression was enhanced, we observed that the PMNL transepithelial migration induced epithelial synthesis of tumor necrosis factor alpha and IL-1β, which in turn promoted the upregulation of DAF.
Expression of
Clostridium difficile
Toxins A and B and Their Sigma Factor TcdD Is Controlled by Temperature
Authors: Karlsson Sture , Dupuy Bruno , Mukherjee Kakoli , Norin Elisabeth , Burman Lars G. , Åkerlund Thomas 
Published: March 2003

ABSTRACT

Growth temperature was found to control the expression of toxins A and B in
Clostridium difficile
VPI 10463
,
with a maximum at 37°C and low levels at 22 and 42°C in both peptone yeast (PY) and defined media. The up-regulation of toxin A and B mRNA and protein levels upon temperature upshift from 22 to 37°C followed the same kinetics, showing that temperature control occurred at the level of transcription. Experiments with
Clostridium perfringens
using
gusA
as a reporter gene demonstrated that both toxin gene promoters were temperature controlled and that their high activity at 37°C was dependent on the alternative sigma factor TcdD. Furthermore,
tcdD
was found to be autoinduced at 37°C. Glucose down-regulated all these responses in the
C. perfringens
constructs, similar to its impact on toxin production in
C. difficile
PY broth cultures.
C. difficile
proteins induced at 37°C and thus coregulated with the toxins by temperature were demonstrated by two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis and identified as enzymes involved in butyric acid production and as electron carriers in oxidation-reduction reactions. The regulation of toxin production in
C. difficile
by temperature is a novel finding apparently reflecting an adaptation of the expression of its virulence to mammalian hosts.
Genetic Organization and Iron-Responsive Regulation of theBrucella abortus2,3-Dihydroxybenzoic Acid Biosynthesis Operon, a Cluster of Genes Required for Wild-Type Virulence in Pregnant Cattle
Authors: Bellaire Bryan H. , Elzer Philip H. , Hagius Sue , Walker Joel , Baldwin Cynthia L. , Roop R. Martin 
Published: March 2003

ABSTRACTBrucella abortusreportedly produces the monocatechol siderophore 2,3-dihydroxybenzoic acid (2,3-DHBA) in response to iron limitation. Nucleotide sequence analysis of the cloned DHBA biosynthesis locus from virulentB. abortus2308 and genetic complementation of definedEscherichia colimutants were used to identify theB. abortusgenes (designateddhbC, -B, and -A) responsible for synthesis of this siderophore. Reverse transcriptase PCR analysis of total RNA withdhb-specific primers demonstrated thatdhbC, -B, and -Aare transcribed as components of an operon, together withdhbE, a functional homolog of theEscherichia coli entEgene. Homologs of theE. coli entDandVibrio cholerae vibHgenes were also detected in the flanking regions immediately adjacent to theB. abortus dhbCEBAoperon, suggesting thatB. abortushas the genetic capacity to produce a more complex 2,3-DHBA-based siderophore. Slot blot hybridization experiments and primer extension analysis showed that transcription of theB. abortus dhbCEBAoperon originates from two iron-regulated promoters located upstream ofdhbC. Consistent with their iron-dependent regulation, both of thedhbCEBApromoter sequences contain typical consensus Fur-binding motifs. Although previously published studies have shown that 2,3-DHBA production is not required for the establishment and maintenance of chronic spleen infection byB. abortusin mice, experimental infection of pregnant cattle with theB. abortus dhbCmutant BHB1 clearly showed that production of this siderophore is essential for wild-type virulence in the natural ruminant host.
AttenuatedYersiniaenterocoliticaMutant Strains Exhibit Differential Virulence in Cytokine-Deficient Mice: Implications for the Development of Novel Live Carrier Vaccines
Authors: Di Genaro María S. , Waidmann Marc , Kramer Uwe , Hitziger Niclas , Bohn Erwin , Autenrieth Ingo B. 
Published: March 2003

ABSTRACTYersiniaenterocoliticamutant strains, including mutants deficient in the chaperone SycH resulting in a functional deficiency in tyrosine phosphatase (YopH), Mn-cofactored superoxide dismutase (SodA), iron-repressive protein 1 (IRP-1), andYersiniaadhesin A (YadA), were demonstrated to be highly attenuated in wild-type C57BL/6 mice. TNFRp55−/−, IL-12p40−/−, and IL-18−/−mutant mice, in which theYersiniawild-type strain causes severe systemic infections, were used to investigate whether theseYersiniamutant strains would be attenuated in immunodeficient hosts. A plasmid-curedYersiniamutant strain was unable to colonize any of the mutant mice tested. A SycH-deficient mutant strain colonized intestinal tissues of these mice but was attenuated for systemic infection in all of the mutant mice. Both YadA- and Irp-1-deficientYersiniamutants were still attenuated in IL-12−/−and IL-18−/−mice but were pathogenic in TNFRp55−/−mice. By contrast, aYersiniasodAmutant was highly pathogenic for TNFRp55−/−and IL-12p40−/−mice while interleukin-18 (IL-18) was dispensable. This finding demonstrates that certain virulence factors enable yersiniae to compete with distinct cytokine-dependent host defense mechanisms. Moreover, while gamma interferon mRNA expression did not reflect protective host responses in cytokine-deficient mice, IL-10 expression coincided with a heavy splenic bacterial load and was associated with progressive infection courses. We can thus segregate minor (SodA), intermediate (YadA and IRP-1), and major (YopH) virulence factors ofY.enterocolitica. Finally, we demonstrate that, even in immunocompromised hosts,YersiniasycHand, with some restrictions,irp-1mutants may be suitable for use as live carrier vaccines.