bluuebunny/crossref_metadata_2025_split huggingface dataset:
Soluble Pilin of
Neisseria gonorrhoeae
Interacts with Human Target Cells and Tissue
Authors: Rytkönen Anne , Johansson Linda , Asp Vendela , Albiger Barbara , Jonsson Ann-Beth 
Published: July 2002

ABSTRACT

Pili of
Neisseria gonorrhoeae
are phase-variable surface structures that mediate adherence to host target cells. Each pilus is composed of thousands of major pilus subunits, pilins, pilus-associated protein PilC, and possibly other components. Piliated and nonpiliated gonococcal clones may secrete a soluble smaller pilin (S-pilin) that is cleaved after amino acid 39 of the mature pilin protein. Here, purified S-pilin was found to migrate as a 61- to 64-kDa double band on nondenaturing gels, suggesting the formation of tetrameric S-pilin proteins with two isomeric forms. In situ studies of binding to formalin-fixed tissue sections demonstrated the binding of S-pilin to human tissue but not to tissue from mouse or rat organs, showing the presence of a human-specific receptor-binding domain within the pilin polypeptide. Pretreatment of the target tissues with proteinase K decreased gonococcal binding dramatically, whereas pretreatment with neuraminidase and
meta
-periodate, which cleave carbon-carbon linkages between vicinal hydroxyl groups in carbohydrates, did not affect gonococcal binding. In overlay assays, purified S-pilin bound to a band with a migration pattern and size similar to those of CD46, a cellular pilus receptor. Further, binding of
N. gonorrhoeae
to target cells and tissues could be blocked by both CD46 antibodies and purified S-pilin. These data argue that S-pilin interacts with a protein domain(s) of the CD46 receptor on human cells.
Parameters Underlying Successful Protection with Live Attenuated Mutants in Experimental Shigellosis
Authors: Bernardini Maria Lina , Arondel Josette , Martini Irene , Aidara Awa , Sansonetti Philippe J. 
Published: July 2002

ABSTRACT

Because the use of live attenuated mutants of
Shigella
spp. represents a promising approach to protection against bacillary dysentery (M. E. Etherridge, A. T. M. Shamsul Hoque, and D. A. Sack, Lab. Anim. Sci. 46:61–66, 1996), it becomes essential to rationalize this approach in animal models in order to optimize attenuation of virulence in the vaccine candidates, as well as their route and mode of administration, and to define the correlates of protection. In this study, we have compared three strains of
Shigella flexneri
5—the wild-type M90T, an
aroC
mutant, and a double
purE aroC
mutant—for their pathogenicity, immunogenicity, and protective capacity. Protection against keratoconjunctivitis, induced by wild-type M90T, was used as the protection read out in guinea pigs that were inoculated either intranasally or intragastrically. Following intranasal immunization, the
aroC
mutant elicited weak nasal tissue destruction compared to M90T and achieved protection correlated with high levels of local anti-lipopolysaccharide immunoglobulin A (IgA), whereas the
purE aroC
double mutant, which also elicited weak tissue destruction, was not protective and elicited a low IgA response. Conversely, following intragastric immunization, only the M90T
purE aroC
double mutant elicited protection compared to both the
aroC
mutant and the wild-type strain. This mutant caused mild inflammatory destruction, particularly at the level of Peyer's patches, but it persisted much longer within the tissues. This could represent an essential parameter of the protective response that, in this case, did not clearly correlate with high anti-lipopolysaccharide IgA titers.
Expression, Extracellular Secretion, and Immunogenicity of thePlasmodium falciparumSporozoite Surface Protein 2 inSalmonellaVaccine Strains
Authors: Gómez-Duarte Oscar G. , Pasetti Marcela F. , Santiago Araceli , Sztein Marcelo B. , Hoffman Stephen L. , Levine Myron M. 
Published: July 2002

ABSTRACTDeleting transmembrane α-helix motifs fromPlasmodium falciparumsporozoite surface protein (SSP-2) allowed its secretion fromSalmonella entericaserovar Typhimurium SL3261 andS. entericaserovar Typhi CVD 908-htrAby the Hly type I secretion system. In mice immunized intranasally, serovar Typhimurium constructs secreting SSP-2 stimulated greater gamma interferon splenocyte responses than did nonsecreting constructs (P= 0.04).
Murine Model for Lymphocytic Tropism by
Borrelia burgdorferi
Authors: Dorward David W. , Larson Ralph S. 
Published: July 2002

ABSTRACT

In vitro studies have demonstrated direct interactions between
Borrelia burgdorferi
and human B and T cells. However, largely because disseminated infections typically occur at very low density, little is known about associations between spirochetes and mammalian host cells in vivo. To assess whether spirochetes interact directly with lymphocytes in mammals, we developed a mouse model for lymphotropism. By repeatedly coincubating spirochetes with primary mouse lymphocytes that were immobilized by adherence to immunomagnetic beads, we were able to preferentially enrich cultures for or against bacteria with constitutive affinity for murine B and T cells. Populations of lymphotropically enriched, stock infectious, and lymphotropically depleted spirochetes were injected intradermally into mice. Lymphocytes were then purified from the blood and spleens of challenged mice and placed into spirochetal culture medium. Cultures of
B. burgdorferi
were obtained from primary lymphocyte preparations from mice challenged with each of the three populations of spirochetes. Recovery of lymphocyte-associated bacteria occurred within 1 h of challenge with enriched bacteria. Lymphocyte preparations from mice challenged with stock infectious and lymphotropically depleted bacteria produced cultures after 1 day postchallenge. All lymphocyte preparations were culture negative after 1 week. These results demonstrate that lymphotropic
B. burgdorferi
is infectious in mice and suggest that associations between spirochetes and lymphocytes occur in vivo. The results also suggest that factors involved in lymphocytic binding may be inducible in vivo. Thus, this system provides a model for studying the role of such interactions in mammalian infections.
Sequence and Antigenic Variability of the
Helicobacter mustelae
Surface Ring Protein Hsr
Authors: Forester Natasha , Lumsden John S. , O'Croinin Tadhg , O'Toole Paul W. 
Published: July 2002

ABSTRACT

We have identified an array of more than 500 repetitive sequences flanking the
hsr
gene, which encodes the major surface protein of the ferret pathogen
Helicobacter mustelae
. The repeats show identity exclusively to the amino-terminal half of Hsr. Analysis of Hsr from three strains indicated variability of exposed epitopes. Characterization of an
hsr
mutant showed that Hsr is not an adhesin.
Chlamydia trachomatis
Infection Does Not Enhance Local Cellular Immunity against Concurrent
Candida
Vaginal Infection
Authors: Kelly Kathleen A. , Gray Heather L. , Walker Jennifer C. , Rank Roger G. , Wormley Floyd L. , Fidel Paul L. 
Published: July 2002

ABSTRACT

Although Th1-type cell-mediated immunity (CMI) is the predominant host defense mechanism against mucosal
Candida albicans
infection, CMI against a vaginal
C. albicans
infection in mice is limited at the vaginal mucosa despite a strong
Candida
-specific Th1-type response in the draining lymph nodes. In contrast, Th1-type CMI is highly effective against an experimental
Chlamydia trachomatis
genital tract infection. This study demonstrated through two independent designs that a concurrent
Candida
and
Chlamydia
infection could not accelerate or modulate the anti-
Candida
CMI response. Together, these results suggest that host responses to these genital tract infections are independent and not influenced by the presence of the other.
Trichinella spiralis
-Infected Muscle Cells: Abundant RNA Polymerase II in Nuclear Speckle Domains Colocalizes with Nuclear Antigens
Authors: Yao Chaoqun , Jasmer Douglas P. 
Published: July 2002

ABSTRACT

Infection of mammalian skeletal muscle cells by
Trichinella spiralis
causes host nuclei to become polyploid (ca. 4N) and abnormally enlarged. It has been postulated that this enlargement reflects an infection-induced elevation of host transcription. Anthelmintic treatment of
T. spiralis
-infected rodents with mebendazole (MBZ) causes a reduction in the size of infected cell nuclei and a significant reduction in the total RNA content of individual infected muscle cells. A monoclonal antibody to the large subunit of RNA polymerase II (Pol II) was used here to assess the effects of infection on Pol II levels in isolated infected cell nuclei. Pol II was localized to speckle domains in isolated infected cell nuclei. Similar domains have been previously localized to sites of RNA synthesis or processing. When compared to the levels in nuclei from other, uninfected host cells, speckle-localized Pol II (SL-Pol II) levels were significantly elevated in infected cell nuclei by a mean of 3.9- to 6.8-fold. Nuclear antigens (NA) recognized by antibodies against
T. spiralis
localized to infected cell nuclei. By use of confocal microscopy, a subpopulation of NA was found colocalized with most speckle domains defined by Pol II. MBZ treatment of chronically infected mice, which depletes NA from infected cell nuclei, caused a significant depletion of SL-Pol II from infected cell nuclei. Control nuclei had a mean of 70% more SL-Pol II than MBZ-treated nuclei. The mean residual level of Pol II in these polyploid nuclei remained elevated by 120% over the level in 2N control nuclei. These observations may indicate two distinct effects of infection on Pol II levels in host cells.
Protection against Pulmonary Infection withPseudomonas aeruginosafollowing Immunization withP. aeruginosa-Pulsed Dendritic Cells
Authors: Worgall Stefan , Kikuchi Toshiaki , Singh Ravi , Martushova Katherine , Lande Leah , Crystal Ronald G. 
Published: July 2002

ABSTRACTTo develop aPseudomonas aeruginosavaccine that allows the host immune system to select the antigens, we hypothesized that dendritic cells (DC) pulsed withP. aeruginosawould induce protective immunity against pulmonary infections withP. aeruginosa. Incubation of murine bone marrow-derived DC withP. aeruginosain vitro led to uptake ofP. aeruginosaand activation of the DC. Spleen-derived CD4+cells from mice immunized withP. aeruginosa-pulsed DC showed increased proliferation, demonstrating that DC pulsed withP. aeruginosawere capable of eliciting aP. aeruginosa-specific immune response. To evaluate ifP. aeruginosa-pulsed DC can induce protective immunity againstP. aeruginosapulmonary infection, DC incubated withP. aeruginosain vitro were administered systemically to syngeneic mice, and the mice were then challenged by intrapulmonary infection withP. aeruginosa(5 × 104CFU/mouse) 13 days later. Unimmunized control mice and mice who had previously received naive DC or DC stimulated with lipopolysaccharide orEscherichia colidied within 72 h. In contrast, 45% of mice receivingP. aeruginosa-pulsed DC demonstrated prolonged survival (>14 days). Finally, DC-pulsed with heat-inactivatedP. aeruginosaprotected CD8−/−but not CD4−/−mice, demonstrating that CD4+T cells were required for the DC pulsed withP. aeruginosato induce protective immunity.
Differential Roles of Interleukin-18 (IL-18) and IL-12 for Induction of Gamma Interferon by Staphylococcal Cell Wall Components and Superantigens
Authors: Stuyt Rogier J. L. , Netea Mihai G. , Kim Soo-Hyun , Novick Daniela , Rubinstein Menachem , Kullberg Bart-Jan , Van der Meer Jos W. M. , Dinarello Charles A. 
Published: July 2002

ABSTRACTThe roles of endogenous cytokines induced by either intact staphylococcal microorganisms or staphylococcal exotoxins were examined using human whole-blood cultures. To accomplish this, interleukin-18 binding protein (IL-18BP) and tumor necrosis factor binding protein (TNFbp) were used to neutralize IL-18 and TNF, respectively, whereas an anti-IL-12 monoclonal antibody was used to neutralize IL-12 and the IL-1 receptor antagonist (IL-1Ra) was used to block IL-1 receptors. Heat-killedStaphylococcus epidermidisandStaphylococcus aureus, as well as the staphylococcal superantigens toxic shock syndrome toxin-1 (TSST-1) and staphylococcus enterotoxin B (SEB) induced gamma interferon (IFN-γ) production.Staphylococcusspp.-induced production of IFN-γ required the presence of endogenous IL-18, IL-12, and TNF. In contrast, TSST-1-induced IFN-γ was not significantly reduced in the presence of IL-18BP, anti-IL-12 antibodies, IL-1Ra, or anti-TNFbp. SEB-induced IFN-γ was significantly inhibited only by anti-IL-12 antibodies, indicating that endogenous IL-18, IL-1, and TNF are not required for SEB-induced IFN-γ. In conclusion, the mechanisms of IFN-γ stimulation by intact staphylococcal microorganisms and by exotoxins differ, and this is likely due to the different receptors which are triggered on the cell membranes. In contrast to its role in the interactions between staphylococci and host cells, IL-18 does not appear to play a major role in superantigen-induced IFN-γ.
Biological Characterization of Lipopolysaccharide fromTreponema pectinovorum
Authors: Kesavalu Lakshmyya , Falk Clinton W. , Davis Kenneth J. , Steffen Michelle J. , Xu Xiaoping , Holt Stanley C. , Ebersole Jeffrey L. 
Published: July 2002

ABSTRACTThis study investigated the endotoxic and biological properties of purified lipopolysaccharide (LPS) isolated from an oral spirochete,Treponema pectinovorum. Endotoxicity, measured byLimulusamoebocyte lysate kinetic assay, showed that the LPS contained 1.28 endotoxin units per μg of purified LPS, which was approximately 4,000 times less thanEscherichia coliO55:B5 LPS. To determine in vivo endotoxicity, LPS responder mice were administered LPS following galactosamine (GalN) sensitization. The LPS induced neither endotoxic symptoms nor lethality for 96 h, suggesting negligible or very low endotoxicity. In contrast, infection with liveT. pectinovoruminduced 100% lethality within 12 h in GalN-sensitized LPS responder mice, indicating an endotoxin-like property of this treponeme. Heat-killed microorganisms exhibited no lethality in GalN-sensitized mice, suggesting that the endotoxicity was associated with heat-labile components. To determine cytokine and chemokine induction by LPS, human gingival fibroblasts were stimulated and secretion of interleukin 1β (IL-1β), granulocyte-macrophage colony-stimulating factor, gamma interferon, IL-6, IL-8, and monocyte chemoattractant protein 1 (MCP-1) was assessed. The purified LPS induced significant amounts of only IL-6, IL-8, and MCP-1, although they were substantially lower than levels after challenge with liveT. pectinovorum. After injection of LPS or live or heat-killedT. pectinovorum, serum was collected from mice and analyzed for proinflammatory cytokines IL-1β, tumor necrosis factor alpha (TNF-α), and IL-6. LPS induced only IL-6 consistently. Both live and heat-killedT. pectinovoruminduced serum IL-6, which was higher than the level detected following LPS administration. Importantly, live bacteria elicited systemic TNF-α and IL-1β levels similar to those induced by a lethal dose of liveE. coliO111. The results indicated thatT. pectinovorumLPS has very low or no endotoxicity, although it can elicit low levels of cytokines from host cells. In contrast to the LPS, liveT. pectinovorumdemonstrated in vivo toxicity, which was associated with serum IL-1β, TNF-α, and IL-6, suggesting an endotoxin-like property of a heat-labile molecule(s) of the spirochete.
RecombinantDirofilaria immitisPolyprotein That Stimulates Murine B Cells To Produce Nonspecific Polyclonal Immunoglobulin E Antibody
Authors: Tezuka Hiroyuki , Imai Shinjiro , Muto Riho , Furuhashi Yuko , Fujita Koichiro 
Published: July 2002

ABSTRACTNonspecific immunoglobulin E (IgE) production is an event characteristically observed in parasitic helminth infections, but its mechanisms are still unclear. To define these mechanisms, we prepared a recombinantDirofilaria immitisprotein (rDiAg) and assessed its effect on nonspecific IgE production. rDiAg preferentially induced nonspecific IgE production, without eliciting specific IgE production, as well as a Th2-type cytokine profile (high interleukin-4 [IL-4] and IL-10 production but low gamma interferon production) in BALB/c mice. rDiAg significantly elicited the proliferative response of naive B cells. This response was not abolished by polymyxin B, an inhibitor of lipopolysaccharide (LPS), and rDiAg normally expanded splenic B cells from LPS nonresponder C3H/HeJ mice. Thus, the mitogenic effect of rDiAg was not due to LPS contamination. rDiAg also enhanced levels of CD23 expression on splenic B cells. Splenic B cells produced marked levels of IgE when cultured with the combination of rDiAg and IL-4 (rDiAg-IL-4), whereas peritoneal B cells produced negligible levels of IgE. rDiAg-IL-4-induced IgE production by splenic B cells was synergistically increased by coculture with peritoneal B cells. rDiAg-driven IL-10 secretion was higher in peritoneal B cells than in splenic B cells. IgE production by splenic B cells cocultured with peritoneal B cells was decreased to a level comparable to that by splenic B cells in the presence of a neutralizing anti-IL-10 monoclonal antibody. Collectively, these results suggest that rDiAg-induced polyclonal expansion and IgE class switching of splenic B cells contribute to nonspecific IgE production and that these responses are enhanced by peritoneal B-cell-derived IL-10.
Regulation of Proinflammatory Cytokines in Human Lung Epithelial Cells Infected withMycoplasma pneumoniae
Authors: Yang Jun , Hooper W. Craig , Phillips Donald J. , Talkington Deborah F. 
Published: July 2002

ABSTRACTMycoplasma pneumoniaeis a small bacterium without a cell wall that causes tracheobronchitis and atypical pneumonia in humans. It has also been associated with chronic conditions, such as arthritis, and extrapulmonary complications, such as encephalitis. Although the interaction of mycoplasmas with respiratory epithelial cells is a critical early phase of pathogenesis, little is known about the cascade of events initiated by infection of respiratory epithelial cells by mycoplasmas. Previous studies have shown thatM. pneumoniaecan induce proinflammatory cytokines in several different study systems including cultured murine and human monocytes. In this study, we demonstrate thatM. pneumoniaeinfection also induces proinflammatory cytokine expression in A549 human lung carcinoma cells. Infection of A549 cells resulted in increased levels of interleukin-8 (IL-8) and tumor necrosis factor alpha mRNA, and both proteins were secreted into culture medium. IL-1β mRNA also increased after infection and IL-1β protein was synthesized, but it remained intracellular. In contrast, levels of IL-6 and gamma interferon mRNA and protein remained unchanged or undetectable. Using protease digestion and antibody blocking methods, we found thatM. pneumoniaecytadherence is important for the induction of cytokines. On the other hand, whileM. pneumoniaeprotein synthesis and DNA synthesis do not appear to be prerequisites for the induction of cytokine gene expression, A549 cellular de novo protein synthesis is responsible for the increased cytokine protein levels. These results suggest a novel role for lung epithelial cells in the pathogenesis ofM. pneumoniaeinfection and provide a better understanding ofM. pneumoniaepathology at the cellular level.
Overexpression of the RNA Polymerase Alpha Subunit Reduces Transcription of Bvg-Activated Virulence Genes in
Bordetella pertussis
Authors: Carbonetti Nicholas H. , Romashko Alla , Irish Teresa J. 
Published: July 2002

ABSTRACT

Overexpression of the RNA polymerase alpha subunit in
Bordetella pertussis
reduces expression of the virulence factor pertussis toxin. Here we show that this reduction is at the level of transcription, is reversed by overexpression of the transcriptional activator BvgA, and is dependent on the C-terminal domain of alpha.
A pAD1-Encoded Small RNA Molecule, mD, Negatively Regulates
Enterococcus faecalis
Pheromone Response by Enhancing Transcription Termination
Authors: Tomita Haruyoshi , Clewell Don B. 
Published: July 2002

ABSTRACT

pAD1 is a 60-kb hemolysin-bacteriocin plasmid in
Enterococcus faecalis
that encodes a conjugative mating response to a peptide sex pheromone, cAD1, secreted by plasmid-free bacteria. The pheromone response is regulated by two proteins: TraE1, which positively regulates all or most conjugative structural genes, and TraA, which negatively regulates
traE1
. TraA binds to pAD1 DNA at the
iad
(encoding the inhibitor peptide iAD1) promoter but is released upon binding to imported pheromone. This leads to enhanced transcription through two closely spaced downstream terminators (t1 and t2) into
traE1
. TraE1 is believed to then upregulate itself from a site located within t2; thus, a small amount of transcription through t1-t2 could lead to overall induction. It is important therefore that the t1-t2 terminators be tightly controlled to keep the response shut down in the absence of pheromone. A small (200-nucleotide) RNA molecule designated mD is encoded just upstream of t1 by a determinant (
traD
) oriented in the direction opposite to that of transcripts utilizing t1. mD is expressed at high levels in the uninduced state, but it decreases significantly upon induction. Here we present results of genetic studies relating to the activity of t1-t2 and show that mD strongly enhances transcriptional termination at t1. The mD activity is shown to influence transcription well downstream and can affect the determinant for aggregation substance
asa1
. The phenomenon is specific in that there is no effect of mD on the unrelated pheromone-responding plasmids pPD1 and pCF10.
Requirement for Homologous Recombination Functions for Expression of the
mutA
Mistranslator tRNA-Induced Mutator Phenotype in
Escherichia coli
Authors: Ren Li , Mamun Abu Amar M. Al , Humayun M. Zafri 
Published: July 2002

ABSTRACT

Expression of the
Escherichia coli mutA
mutator phenotype requires
recA
,
recB
,
recC
,
ruvA
, and
ruvC
gene, but not
recD
,
recF
,
recO
, or
recR
genes. Thus, the
recBCD
-dependent homologous recombination system is a component of the signal pathway that activates an error-prone DNA polymerase in
mutA
cells.
The
Yersinia enterocolitica
Phospholipase Gene
yplA
Is Part of the Flagellar Regulon
Authors: Schmiel Deborah H. , Young Glenn M. , Miller Virginia L. 
Published: July 2002

ABSTRACT

Yersinia enterocolitica yplA
encodes a phospholipase required for virulence. Virulence genes are often regulated in response to environmental signals; therefore,
yplA
expression was examined using a
yplA
::
lacZY
transcriptional fusion. Maximal
yplA
expression occurred between pH 6.5 and pH 7.5 and was induced in the mid-logarithmic growth phase. Potential Fnr, cyclic AMP (cAMP)-cAMP receptor protein (Crp), and ς
F
regulatory sites were identified in the nucleotide sequence. Reduction of
yplA
expression by aeration, addition of glucose and sucrose, and application of high temperature and salt is consistent with Fnr-, cAMP-Crp-, and ς
F
-mediated regulation, respectively. Expression of
yplA
was reduced in
flhDC
and
fliA
null strains, indicating that
yplA
is part of the flagellar regulon.