bluuebunny/crossref_metadata_2025_split huggingface dataset:
Inactivation of the Pst System Reduces the Virulence of an Avian Pathogenic
Escherichia coli
O78 Strain
Authors: Lamarche Martin G. , Dozois Charles M. , Daigle France , Caza Mélissa , Curtiss Roy , Dubreuil J. Daniel , Harel Josée 
Published: June 2005

ABSTRACT

Escherichia coli
O78 strains are frequently associated with extraintestinal diseases, such as airsacculitis and septicemia, in poultry, livestock, and humans. To understand the influence of the
pst
operon in the virulence of
E. coli
, we introduced mutations into the
pst
genes of the avian pathogenic
E. coli
(APEC) O78:K80 strain χ7122 by allelic exchange. The mutation of
pst
genes led to the constitutive expression of the Pho regulon. Furthermore, the virulence of APEC strain χ7122 in a chicken infection model was attenuated by inactivation of the Pst system. The
pst
mutant caused significantly fewer extraintestinal lesions in infected chickens, and bacterial numbers isolated from different tissues after infection were significantly lower for the mutant than for the wild-type strain. Moreover, resistance to the bactericidal effects of rabbit serum and acid shock was impaired in the
pst
mutant, in contrast to the wild-type strain. In addition, the MIC of polymyxin was twofold lower for the mutant than for the wild-type strain. Although the
pst
mutant demonstrated an increased susceptibility to rabbit serum, this strain was not killed by chicken serum, suggesting the presence of differences in host innate immune defenses and complement-mediated killing. In APEC O78 strain χ7122, a functional Pst system is required for full virulence and resistance to acid shock and polymyxin. Our results suggest that the mutation of
pst
genes induces a deregulation of phosphate sensing and changes in the cell surface composition that lead to decreased virulence, indicating the importance of the Pst system for the virulence of pathogenic
E. coli
strains from different hosts.
Impact of
Helicobacter pylori
Virulence Factors and Compounds on Activation and Maturation of Human Dendritic Cells
Authors: Kranzer Katharina , Söllner Liane , Aigner Michael , Lehn Norbert , Deml Ludwig , Rehli Michael , Schneider-Brachert Wulf 
Published: June 2005

ABSTRACT

Recently, we and others have shown that
Helicobacter pylori
induces dendritic cell (DC) activation and maturation. However, the impact of virulence factors on the interplay between DCs and
H. pylori
remains elusive. Therefore, we investigated the contribution of
cag
pathogenicity island (PAI) and VacA status on cytokine release and up-regulation of costimulatory molecules in
H. pylori
-treated DCs. In addition, to characterize the stimulatory capacity of
H. pylori
compounds in more detail, we studied the effect of formalin-inactivated and sonicated
H. pylori
, as well as secreted
H. pylori
molecules, on DCs. Incubation of DCs with viable or formalin-inactivated
H. pylori
induced comparable secretion of interleukin-6 (IL-6), IL-8, IL-10, IL-12, IL-1β, and tumor necrosis factor (TNF). In contrast, IL-12 and IL-1β release was significantly reduced in DCs treated with sonicated bacteria and secreted bacterial molecules. Treatment of sonicated
H. pylori
preparations with polymyxin B resulted in a significant reduction of IL-8 and IL-6 secretion, suggesting that
H. pylori
-derived lipopolysaccharide at least partially contributes to activation of immature DCs. In addition, the capacity of
H. pylori
-pulsed DCs to activate allogeneic T cells was not affected by
cag
PAI and VacA. Pretreatment of DC with cytochalasin D significantly inhibited secretion of IL-12, IL-1β, and TNF, indicating that phagocytosis of
H. pylori
contributes to maximal activation of DCs. Taken together, our results suggest that DC activation and maturation, as well as DC-mediated T-cell activation, are independent of the
cag
PAI and VacA status of
H. pylori
.
Identification of
Mycobacterium avium
Genes That Affect Invasion of the Intestinal Epithelium
Authors: Miltner Elizabeth , Daroogheh Koorosh , Mehta Parmod K. , Cirillo Suat L. G. , Cirillo Jeffrey D. , Bermudez Luiz E. 
Published: June 2005

ABSTRACT

Invasion of intestinal mucosa of the host by
Mycobacterium avium
is a critical step in pathogenesis and likely involves several different bacterial proteins, lipids, glycoproteins, and/or glycolipids. Through the screening of an
M. avium
genomic library in
Mycobacterium smegmatis
, we have identified a number of
M. avium
genes that are associated with increased invasion of mucosal epithelial cells. In order to further investigate these genes, we cloned six of them into a plasmid downstream of a strong mycobacterial promoter (L5 mycobacterial phage promoter), resulting in constitutive expression. Bacteria were then evaluated for increased expression and examined for invasion of HT-29 intestinal epithelial cells. The genes identified encode proteins that are similar to (i)
M. tuberculosis
coenzyme A carboxylase, (ii)
M. tuberculosis
membrane proteins of unknown function, (iii)
M. tuberculosis
FadE20, (iv) a
Mycobacterium paratuberculosis
surface protein, and (v)
M. tuberculosis
cyclopropane fatty acyl-phopholipid synthase. The constitutive expression of these genes confers to
M. avium
the ability to invade HT-29 intestinal epithelial cells with a severalfold increase in efficiency compared to both the wild-type
M. avium
and
M. avium
containing the vector alone. Using the murine intestinal ligated loop model, it was observed that the constitutive expression of
M. avium
proteins has a modest impact on the ability to enter the intestinal mucosa when compared with the wild-type control, suggesting that under in vivo conditions these genes are expressed at higher levels. Evaluation of the expression of these invasion-related genes indicated that under conditions similar to the intestinal lumen environment, the genes identified are upregulated. These data suggest that invasion of the intestinal mucosa is an event that requires the participation of several bacterial factors and the expression of the genes that encode them is less observed under standard laboratory growth conditions.
Effects of Estradiol on Lipopolysaccharide and Pam
3
Cys Stimulation of CCL20/Macrophage Inflammatory Protein 3 Alpha and Tumor Necrosis Factor Alpha Production by Uterine Epithelial Cells in Culture
Authors: Crane-Godreau Mardi A. , Wira Charles R. 
Published: June 2005

ABSTRACT

We have previously demonstrated that rat uterine epithelial cells (UEC) produce CCL20/macrophage inflammatory protein 3 alpha (MIP3α) and tumor necrosis factor alpha (TNF-α) in response to live and heat-killed
Escherichia coli
and to the pathogen-associated molecular patterns (PAMP) lipopolysaccharide (LPS) and Pam
3
Cys. To determine whether estradiol (E
2
) modulates PAMP-induced CCL20/MIP3α and TNF-α secretion, primary cultures of rat UEC were incubated with E
2
for 24 h and then treated with LPS or Pam
3
Cys or not treated for an additional 12 h. E
2
inhibited the constitutive secretion of TNF-α and CCL20/MIP3α into culture media. Interestingly, E
2
pretreatment enhanced CCL20/MIP3α secretion due to LPS and Pam
3
Cys administration. In contrast, and at the same time, E
2
lowered the TNF-α response to both PAMP. To determine whether estrogen receptors (ER) mediated the effects of E
2
, epithelial cells were incubated with E
2
and/or ICI 182,780, a known ER antagonist. ICI 182,780 had no effect on E
2
inhibition of constitutive TNF-α and CCL20/MIP3α secretion. In contrast, ICI 182,780 reversed the stimulatory effect of E
2
on LPS- and/or Pam
3
Cys-induced CCL20/MIP3α secretion as well as partially reversed the inhibitory effect of E
2
on TNF-α production by epithelial cells. Overall, these results indicate that E
2
regulates the production of TNF-α and CCL20/MIP3α by UEC in the absence as well as presence of PAMP. Since CCL20/MIP3α has antimicrobial activity and is chemotactic for immune cells, these studies suggest that regulation of CCL20/MIP3α and TNF-α by E
2
and PAMP may have profound effects on innate and adaptive immune responses to microbial challenge in the female reproductive tract.
Endocrine Perturbation Increases Susceptibility of Mice to Anthrax Lethal Toxin
Authors: Moayeri Mahtab , Webster Jeanette I. , Wiggins Jason F. , Leppla Stephen H. , Sternberg Esther M. 
Published: June 2005

ABSTRACTBacillus anthracislethal toxin (LT) causes vascular collapse and high lethality in BALB/cJ mice, intermediate lethality in C57BL/6J mice, and no lethality in DBA/2J mice. We found that adrenalectomized (ADX) mice of all three strains had increased susceptibility to LT. The increased susceptibility of ADX-DBA/2J mice was not accompanied by changes in their macrophage sensitivity or cytokine response to LT. DBA/2J mice showed no change in serum corticosteroid levels in response to LT injection, while BALB/cJ mice showed a fivefold increase in serum corticosterone. However, LT inhibited dexamethasone (DEX)-induced glucocorticoid receptor gene activation to similar extents in all three strains. DEX treatment did not rescue ADX mice from LT-mediated mortality. Surprisingly, oral DEX treatment also sensitized adrenally intact DBA/2J mice to LT lethality at all doses tested and also exacerbated LT-mediated pathogenesis and mortality in BALB/cJ mice. Aldosterone did not protect ADX mice from toxin challenge. These results indicate that susceptibility to anthrax LT in mice depends on a fine but easily perturbed balance of endocrine functions. Thus, the potentially detrimental consequences of steroid therapy for anthrax must be considered in treatment protocols for this disease.
Innate Immune Defense against Pneumococcal Pneumonia Requires Pulmonary Complement Component C3
Authors: Kerr Alison R. , Paterson Gavin K. , Riboldi-Tunnicliffe Alan , Mitchell Tim J. 
Published: June 2005

ABSTRACTComplement is known to be involved in protection against systemic infection withStreptococcus pneumoniae. However, less is known about effects of complement within the lungs during pneumococcal pneumonia. By intranasally infecting transgenic mice unable to express complement C3, we investigated the role of complement in pulmonary defenses againstS. pneumoniae. It was demonstrated that within the lungs, there is a requirement for C3 during the initial hours of infection. It was found that within 1 h of infection, bacterial loads decreased within lung airways of control mice as C3 protein increased. The lack of C3 resulted in the inability to control growth of wild-type or attenuated pneumococci within the lungs and bloodstream, resulting in an overwhelming inflammatory response and shorter survival times. Our results show that during the initial hours of infection withS. pneumoniae, C3 is protective within the lungs and subsequently plays an important role systemically.
Alveolar Response toPseudomonas aeruginosa: Role of the Type III Secretion System
Authors: Ader F. , Le Berre R. , Faure K. , Gosset P. , Epaulard O. , Toussaint B. , Polack B. , Nowak E. , Viget N. B. , Kipnis E. , Guery B. P. 
Published: June 2005

ABSTRACTThe type III secretion system (TTSS) is a specialized cytotoxin-translocating apparatus of gram-negative bacteria which is involved in lung injury, septic shock, and a poor patient outcome. Recent studies have attributed these effects mainly to the ExoU effector protein. However, few studies have focused on the ExoU-independent pathogenicity of the TTSS. For the present study, we compared the pathogenicities of two strains ofPseudomonas aeruginosain a murine model of acute lung injury. We compared the CHA strain, which has a functional TTSS producing ExoS and ExoT but not ExoU, to an isogenic mutant with an inactivatedexsAgene, CHA-D1, which does not express the TTSS at all. Rats challenged with CHA had significantly increased lung injury, as assessed by the wet/dry weight ratio for the lungs and the protein level in bronchoalveolar lavage fluid (BALF) at 12 h, compared to those challenged with CHA-D1. Consistent with these findings, the CHA strain was associated with increased in vitro cytotoxicity on A549 cells, as assessed by the release of lactate dehydrogenase. CHA was also associated at 12 h with a major decrease in polymorphonuclear neutrophils in BALF, with a proinflammatory response, as assessed by the amounts of tumor necrosis factor alpha and interleukin-1β, and with decreased bacterial clearance from the lungs, ultimately leading to an increased mortality rate. These results demonstrate that the TTSS has a major role inP. aeruginosapathogenicity independent of the role of ExoU. This report underscores the crucial roles of ExoS and ExoT or other TTSS-related virulence factors in addition to ExoU.
Identification of a Novel Adhesion Molecule Involved in the Virulence ofLegionella pneumophila
Authors: Chang Bin , Kura Fumiaki , Amemura-Maekawa Junko , Koizumi Nobuo , Watanabe Haruo 
Published: June 2005

ABSTRACTLegionella pneumophilais an intracellular bacterium, and its successful parasitism in host cells involves two reciprocal phases: transmission and intracellular replication. In this study, we sought genes that are involved in virulence by screening a genomic DNA library of anL. pneumophilastrain, 80-045, with convalescent-phase sera of Legionnaires' disease patients. Three antigens that reacted exclusively with the convalescent-phase sera were isolated. One of them, which shared homology with an integrin analogue ofSaccharomyces cerevisiae, was namedL. pneumophilaadhesion molecule homologous with integrin analogue ofS. cerevisiae(LaiA). ThelaiAgene product was involved inL. pneumophilaadhesion to and invasion of the human lung alveolar epithelial cell line A549 during in vitro coculture. However, its presence did not affect multiplication ofL. pneumophilawithin a U937 human macrophage cell line. Furthermore, after intranasal infection of A/J mice, thelaiAmutant was eliminated from lungs and caused reduced mortality compared to the wild isolate. Thus, we conclude that thelaiAgene encodes a virulence factor that is involved in transmission ofL. pneumophila80-045 and may play a role in Legionnaires' disease in humans.
Production of Nontypeable
Haemophilus influenzae
HtrA by Recombinant
Bordetella pertussis
with the Use of Filamentous Hemagglutinin as a Carrier
Authors: Alonso Sylvie , Willery Eve , Renauld-Mongénie Genevieve , Locht Camille 
Published: June 2005

ABSTRACT

Bordetella pertussis
, the etiologic agent of whooping cough, is a highly infectious human pathogen capable of inducing mucosal and systemic immune responses upon a single intranasal administration. In an attenuated, pertussis toxin (PTX)-deficient recombinant form, it may therefore constitute an efficient bacterial vector that is particularly well adapted for the delivery of heterologous antigens to the respiratory mucosa. Filamentous hemagglutinin (FHA) has been used as a carrier to present foreign antigens at the bacterial surface, thereby inducing local, systemic, and protective immune responses to these antigens in mice. Both full-length and truncated (Fha44) forms of FHA have been used for antigen presentation. To investigate the effect of the carrier (FHA or Fha44) on antibody responses to passenger antigens, we genetically fused the HtrA protein of nontypeable
Haemophilus influenzae
to either FHA form. The
fha-htrA
and Fha44 gene
-htrA
hybrids were expressed as single copies inserted into the chromosome of PTX-deficient
B. pertussis
. Both chimeras were secreted into the culture supernatants of the recombinant strains and were recognized by anti-FHA and anti-HtrA antibodies. Intranasal infection with the strain producing the FHA-HtrA hybrid led to significantly higher anti-HtrA and anti-FHA antibody titers than those obtained in mice infected with the Fha44-HtrA-producing strain. Interestingly, the
B. pertussis
strain producing the Fha44-HtrA chimera colonized the mouse lungs more efficiently than the parental, Fha44-producing strain and gave rise to higher anti-FHA antibody titers than those induced by the parental strain.
Virulence Attenuation and Live Vaccine Potential of
aroA
,
crp cdt cya
, and Plasmid-Cured Mutants of
Salmonella enterica
Serovar Abortusovis in Mice and Sheep
Authors: Uzzau Sergio , Marogna Gavino , Leori Guido Sisinnio , Curtiss Roy , Schianchi Giuseppe , Stocker Bruce A. D. , Rubino Salvatore 
Published: June 2005

ABSTRACT

Three live vaccine candidates of
Salmonella enterica
subspecies I serotype Abortusovis (
aroA
,
cya crp cdt
, and plasmid-cured strains) have been developed, and their efficacies in inducing humoral antibodies and protecting against abortion after challenge with wild-type strain SS44 were evaluated in sheep. Following estrus synchronization, animals were immunized 3 weeks after fertilization and boosted once 3 weeks later. Following challenge with wild-type SS44, pregnancy failure of vaccinated ewes was reduced compared to that of nonimmunized controls. Attenuation of each vaccine was also assessed in challenge experiments with nonimmunized pregnant ewes and in BALB/c mice. All three vaccine candidates appear to be safe for use in sheep and provide a model for the development of live vaccine candidates against naturally occurring ovine salmonellosis.
Bovine Intestinal Alkaline Phosphatase Attenuates the Inflammatory Response in Secondary Peritonitis in Mice
Authors: van Veen Suzanne Q. , van Vliet Arlène K. , Wulferink Marty , Brands Ruud , Boermeester Marja A. , van Gulik Thomas M. 
Published: June 2005

ABSTRACTLipopolysaccharide (LPS) contributes importantly to morbidity and mortality in sepsis. Bovine intestinal alkaline phosphatase (BIAP) was demonstrated to detoxify LPS through dephosphorylation. LPS injection combined with BIAP reduced inflammation and improved survival in various experimental settings. In this study, single-dose intravenous administration of BIAP (0.15 IU/g) was applied in a murine cecal ligation and puncture (CLP) model of polymicrobial sepsis. Saline was given as control (S group). Treatment with BIAP prior to CLP (prophylaxis; BIAP-P group) or shortly after (early treatment; BIAP-ET group) reduced cytokine concentrations in plasma and peritoneal lavage fluid (PLF). Tumor necrosis factor-alpha peak levels decreased from 170 pg/ml (S) to 57.5 (BIAP-P) and 82.5 (BIAP-ET) in plasma and in PLF from 57.5 pg/ml (S) to 35.3 (BIAP-P) and 16.8 (BIAP-ET) (all,P< 0.05). Peak interleukin-6 levels in plasma decreased from 19.3 ng/ml (S) to 3.4 (BIAP-P) and 11.5 (BIAP-ET) and in PLF from 32.6 ng/ml (S) to 13.4 (BIAP-P) and 10.9 (BIAP-ET) (all,P< 0.05). Macrophage chemoattractant protein 1 peak levels in plasma decreased from 2.0 ng/ml (S) to 1.0 (BIAP-P) and 0.7 (BIAP-ET) and in PLF from 6.4 (S) to 2.3 (BIAP-P) and 1.3 ng/ml (BIAP-ET) (all,P< 0.05). BIAP-treated groups showed decreased transaminase activity in plasma and decreased myeloperoxidase activity in the lung, indicating reduced associated hepatocellular and pulmonary damage. Survival was not significantly altered by BIAP in this single-dose regimen. In polymicrobial secondary peritonitis, both prophylactic and early BIAP treatment attenuates the inflammatory response both locally and systemically and reduces associated liver and lung damage.
Effect of
Chlamydia pneumoniae
on Cellular ATP Content in Mouse Macrophages: Role of Toll-Like Receptor 2
Authors: Yaraei Kambiz , Campbell Lee Ann , Zhu Xiaodong , Liles W. Conrad , Kuo Cho-chou , Rosenfeld Michael E. 
Published: June 2005

ABSTRACT

Chlamydiae are obligate intracellular gram-negative bacteria and are dependent on the host cell for ATP. Thus, chlamydial infection may alter the intracellular levels of ATP and affect all energy-dependent processes within the cell. We have shown that both live
C. pneumoniae
and inactivated
C. pneumoniae
induce markers of cell death prior to completion of the bacterial growth cycle. As depletion of ATP could account for the observed increase in cell death, the effects of
C. pneumoniae
on ATP concentrations within mouse macrophages were investigated. Live, heat-killed, and UV-inactivated
C. pneumoniae
cultures (at multiplicities of infection [MOIs] of 0.01, 0.1, and 1.0) were incubated with mouse bone marrow macrophages isolated from C57BL/6J mice and mice deficient in Toll-like receptors. Treatment of the macrophages with both live and inactivated
C. pneumoniae
increased the ATP content of the cells. In cells infected with live
C. pneumoniae
, the increase was inversely proportional to the MOI. In cells treated with inactivated
C. pneumoniae
, the increase in ATP content was smaller than that induced by infection with live organisms and was proportional to the MOI. The increase in ATP content early in the developmental cycle was independent of the growth of
C. pneumoniae
, while sustained induction required live organisms. The capacity of
C. pneumoniae
to increase the ATP content was ablated in macrophages deficient in expression of either Toll-like receptor 2 or the Toll-like receptor accessory protein MyD88. In contrast, no effect was observed in macrophages lacking expression of Toll-like receptor 4.
sciS
, an
icmF
Homolog in
Salmonella enterica
Serovar Typhimurium, Limits Intracellular Replication and Decreases Virulence
Authors: Parsons Duncan A. , Heffron Fred 
Published: June 2005

ABSTRACT

Salmonella enterica
serovar Typhimurium utilizes macrophages to disseminate from the intestine to deeper tissues within the body. While
S. enterica
serovar Typhimurium has been shown to kill its host macrophage, it can persist intracellularly beyond 18 h postinfection. To identify factors involved in late stages of infection, we screened a transposon library made in
S. enterica
serovar Typhimurium for the ability to persist in J774 macrophages at 24 h postinfection. Through this screen, we identified a gene,
sciS
, found to be homologous to
icmF
in
Legionella pneumophila. icmF
, which is required for intracellular multiplication, is conserved in several gram-negative pathogens, and its homolog appears to have been acquired horizontally in
S. enterica
serovar Typhimurium. We found that an
sciS
mutant displayed increased intracellular numbers in J774 macrophages when compared to the wild-type strain at 24 h postinfection.
sciS
was maximally transcribed at 27 h postinfection and is repressed by SsrB, an activator of genes required for promoting intracellular survival. Finally, we demonstrate that an
sciS
mutant is hypervirulent in mice when administered intragastrically. Taken together, these data indicate a role for SciS in controlling intracellular bacterial levels at later stages of infection and attenuating virulence in a murine host
Quantitative Dynamics of
Plasmodium yoelii
Sporozoite Transmission by Infected Anopheline Mosquitoes
Authors: Medica Darcy L. , Sinnis Photini 
Published: June 2005

ABSTRACT

Malaria transmission begins with the injection of
Plasmodium
sporozoites into the skin of a vertebrate host by infected anopheline mosquitoes. Although the size of the sporozoite inoculum likely affects the course of the disease, the number of sporozoites injected by infected mosquitoes has not been determined in vivo. Using a quantitative PCR assay, we determined the number of sporozoites injected into mice by single mosquitoes. Analysis of 59 mosquito feedings showed that a single infected mosquito injected between 0 and 1,297 sporozoites, with a mean of 123 and a median of 18. Twenty-two percent of infected mosquitoes injected no sporozoites. The number of sporozoites injected was only weakly correlated to the salivary gland load. To better understand the large variability in sporozoite injection among mosquitoes, we quantified the sporozoites injected by individual mosquitoes on three different days. Approximately 20% of moderately to heavily infected mosquitoes injected few to no sporozoites on all 3 days, suggesting that some mosquitoes are poor transmitters of sporozoites. Other mosquitoes injected high numbers of sporozoites on at least one of the days observed and minimal numbers on the other day(s), supporting the hypothesis that sporozoite injection is discontinuous, a pattern that may aid in the establishment of malaria infection.