bluuebunny/crossref_metadata_2025_split huggingface dataset:
Role of
Mycobacterium tuberculosis
Copper-Zinc Superoxide Dismutase
Authors: Dussurget Olivier , Stewart Graham , Neyrolles Olivier , Pescher Pascale , Young Douglas , Marchal Gilles 
Published: July 2002

ABSTRACT

Superoxide dismutases (SODs) play an important role in protection against oxidative stress and have been shown to contribute to the pathogenicity of many bacterial species. To determine the function of the mycobacterial copper and zinc-cofactored SOD (CuZnSOD), we constructed and characterized
Mycobacterium tuberculosis
and
Mycobacterium bovis
BCG CuZnSOD null mutants. Both strains were more sensitive to superoxides and hydrogen peroxide than were their respective parental strains. The survival of
M. bovis
BCG in unstimulated as well as activated mouse bone marrow-derived macrophages was not affected by the loss of CuZnSOD. The survival of CuZnSOD deficient-
M. tuberculosis
in guinea pig tissues was comparable to that of its parental strain. These results indicate that the mycobacterial CuZnSOD is not essential for intracellular growth within macrophages and does not detectably contribute to the pathogenicity of
M. tuberculosis
.
Proteins PblA and PblB of
Streptococcus mitis
, Which Promote Binding to Human Platelets, Are Encoded within a Lysogenic Bacteriophage
Authors: Bensing Barbara A. , Siboo Ian R. , Sullam Paul M. 
Published: July 2002

ABSTRACT

The binding of platelets by bacteria is a proposed central mechanism in the pathogenesis of infective endocarditis. Platelet binding by
Streptococcus mitis
strain SF100 (an endocarditis isolate) was recently shown to be mediated in part by the surface proteins PblA and PblB. The genes encoding PblA and PblB are clustered with genes nearly identical to those of streptococcal phages r1t, 01205, and Dp-1, suggesting that
pblA
and
pblB
might reside within a prophage. To address this possibility, cultures of SF100 were exposed to either mitomycin C or UV light, both of which are known to induce the lytic cycle of many temperate phages. Both treatments caused a significant increase in the transcription of
pblA
. Treatment with mitomycin C or UV light also caused a substantial increase in the expression of PblA and PblB, as detected by Western blot analysis of proteins in the SF100 cell wall. By electron microscopy, phage particles were readily visible in the supernatants from induced cultures of SF100. The phage, designated SM1, had a double-stranded DNA genome of approximately 35 kb. Southern blot analysis of phage DNA indicated that
pblA
and
pblB
were contained within the SM1 genome. Furthermore, Western blot analysis of phage proteins revealed that both PblA and PblB were present in the phage particles. These findings indicate that PblA and PblB are encoded by a lysogenic bacteriophage, which could facilitate the dissemination of these potential virulence determinants to other bacterial pathogens.
Targeting of Nasal Mucosa-Associated Antigen-Presenting Cells In Vivo with an Outer Membrane Protein A Derived fromKlebsiellapneumoniae
Authors: Goetsch Liliane , Gonzalez Alexandra , Plotnicky-Gilquin Hélène , Haeuw Jean François , Aubry Jean Pierre , Beck Alain , Bonnefoy Jean Yves , Corvaı̈a Nathalie 
Published: July 2002

ABSTRACTAdministration of vaccines by the nasal route has recently proven to be one of the most efficient ways for inducing both mucosal and systemic antibody responses in experimental animals. Our results demonstrate that P40, a well-defined outer membrane protein A fromKlebsiellapneumoniae, is indeed a carrier molecule suitable for nasal immunization. Using fragments from the respiratory syncytial virus subgroup A (RSV-A) G protein as antigen models, it has been shown that P40 is able to induce both systemic and mucosal immunity when fused or coupled to a protein or a peptide and administered intranasally (i.n.) to naive orK.pneumoniae-primed mice. Confocal analyses of nasal mucosa-associated lymphoid tissue after i.n. instillation of P40 showed that this molecule is able to cross the nasal epithelium and target CD11c-positive cells likely to be murine dendritic cells or macrophages. More importantly, this targeting of antigen-presenting cells following i.n. immunization with a subunit of the RSV-A molecule in the absence of any mucosal adjuvant results in both upper and lower respiratory tract protection against RSV-A infection.
Association of Mitogen-Activated Protein Kinase Pathways with Gingival Epithelial Cell Responses toPorphyromonas gingivalisInfection
Authors: Watanabe Kiyoko , Yilmaz Özlem , Nakhjiri Simin F. , Belton Carol M. , Lamont Richard J. 
Published: July 2002

ABSTRACTMitogen-activated protein (MAP) kinase pathways are key factors in host signaling events and can also play important roles in the internalization of pathogenic bacteria by host cells.Porphyromonas gingivalis, a periodontal pathogen,can efficiently invade human gingival epithelial cells (GECs). In this study, we examined the activation of MAP kinase pathways in GECs infected withP. gingivalis. c-Jun N-terminal kinase (JNK) was activated after 5 min of infection withP. gingivalis,whereas noninvasiveStreptococcus gordoniidid not have a significant effect on JNK activation. In contrast, extracellular signal-regulated kinase (ERK) 1/2 was downregulated in a dose-dependent manner byP. gingivalis, but not byS. gordonii, after a 15-min exposure. Nonmetabolically activeP. gingivaliscells were unable to modulate MAP kinase activity. U0126, a specific inhibitor of MEK1/2 (ERK1/2 kinase), and toxin B, a specific inhibitor of Rho family GTPases, had no effect onP. gingivalisinvasion. Genistein, a tyrosine protein kinase inhibitor, blocked uptake ofP. gingivalis. The transcriptional regulator NF-κB was not activated byP. gingivalis. These results suggest thatP. gingivaliscan selectively target components of the MAP kinase pathways. ERK1/2, while not involved inP. gingivalisinvasion of GECs, may be downregulated by internalizedP. gingivalis. Activation of JNK is associated with the invasive process ofP. gingivalis.
Koala Biovar of
Chlamydia pneumoniae
Infects Human and Koala Monocytes and Induces Increased Uptake of Lipids In Vitro
Authors: Coles Katie A. , Timms Peter , Smith David W. 
Published: July 2002

ABSTRACT

We examined the ability of the koala biovar of
Chlamydia pneumoniae
to infect both Hep-2 cells and human monocytes and the effect of infection on the formation of foam cells. The koala biovar produced large inclusions in both human and koala monocytes and in Hep-2 cells. Koala
C. pneumoniae
induced foam cell formation with and without added low-density lipoprotein, in contrast to TW183, which produced increased foam cell formation only in the presence of low-density lipoprotein.
Neural Route of CerebralListeria monocytogenesMurine Infection: Role of Immune Response Mechanisms in Controling Bacterial Neuroinvasion
Authors: Jin Yuxuan , Dons Lone , Kristensson Krister , Rottenberg Martı́n E. 
Published: July 2002

ABSTRACTThe pathologic features of cerebralListeria monocytogenesinfection strongly suggest that besides hematogenous spread, bacteria might also spread via a neural route. We propose that after snout infection of recombination activating gene 1 (RAG-1)-deficient mice,L. monocytogenesspreads to the brain via a neural route. The neural route of invasion is suggested by (i) the immunostaining ofL. monocytogenesin the trigeminal ganglia (TG) and brain stem but not in other areas of the brain; (ii) the kinetics of bacterial loads in snout, TG, and brain; and (iii) the increased resistance of mice infected with aplcBbacterial mutant (unable to spread from cell to cell). Gamma interferon (IFN-γ) plays a protective role in neuroinvasion; inducible nitric oxide synthase (iNOS) accounts only partially for the protection, as shown by a comparison of the susceptibilities of IFN-γ receptor (IFN-γR)-deficient, iNOS-deficient, and wild-type mice to snout infection withL. monocytogenes. The dramatically enhanced susceptibility ofRAG-1-deficient, IFN-γR gene-deficient mice indicated the overall importance of innate immune cells in the release of protective levels of IFN-γ. The source of IFN-γ appeared to be NK cells, as shown by use ofRAG-1-deficient, γ-chain receptor gene-deficient mice; NK cells played a relevant protective role in neuroinvasion through a perforin-independent mechanism. In vitro evidence indicated that IFN-γ can directly induce bacteriostatic mechanisms in neural tissue.
T Cells That React to the ImmunodominantLeishmania majorLACK Antigen Prevent Early Dissemination of the Parasite in Susceptible BALB/c Mice
Authors: Schilling Sabrina , Glaichenhaus Nicolas 
Published: July 2002

ABSTRACTSusceptibility of BALB/c mice toLeishmania majordepends on the early production of IL-4 by CD4+T cells which react to the parasite LACK antigen. Here, we show that LACK-specific cells are rapidly recruited to the site of infection and favor the early dissemination ofL. majorto the internal organs.
Restoration of Mga Function to aStreptococcus pyogenesStrain (M Type 50) That Is Virulent in Mice
Authors: Limbago Brandi , McIver Kevin S. , Penumalli Vikram , Weinrick Brian , Scott June R. 
Published: July 2002

ABSTRACTThe Mga protein in B514Sm, aStreptococcus pyogenesstrain isolated as a mouse pathogen, contains amino acid substitutions at conserved sites that render the protein defective. Replacement ofmga50with the functional homologmga4.1restored full expression of Mga-regulated proteins. Restoration of Mga function did not affect fibrinogen binding, nor did it affect virulence in several mouse models of group A streptococcus infection.
Commercial Preparations of Lipoteichoic Acid Contain Endotoxin That Contributes to Activation of Mouse Macrophages In Vitro
Authors: Gao Jian Jun , Xue Qiao , Zuvanich Eleanor G. , Haghi Kevin R. , Morrison David C. 
Published: July 2002

ABSTRACT

Lipoteichoic acids (LTA), cell wall components of gram-positive bacteria, have been reported to induce various inflammatory mediators and to play a key role in gram-positive-microbe-mediated septic shock. In a large number of these studies, investigators used commercially available LTA purified from a variety of gram-positive bacteria, including
Staphylococcus aureus
,
Bacillus subtilis
, and
Streptococcus sanguis
. We report here that, although these commercially available LTA could be readily shown to stimulate production of nitric oxide (NO) in RAW 264.7 mouse macrophages, the activity was dramatically inhibited by polymyxin B, a relatively specific inhibitor of endotoxin biological activity. One-step purification of the commercially available
S. aureus
LTA using hydrophobic interaction chromatography resulted in two well-separated peak fractions, one highly enriched for LTA and a second highly enriched for endotoxin. The LTA-enriched fractions did not induce production of NO in RAW 264.7 macrophages, although they caused a dose-dependent induction of NO in the presence of low concentrations of gamma interferon (IFN-γ) (which by itself induced little NO), regardless of the presence of polymyxin B. In contrast, the endotoxin-enriched fractions by themselves inhibited in high levels of NO in RAW 264.7 macrophages but activity was almost completely inhibited in the presence of polymyxin B. Consistent with these findings, our data also indicate that commercial LTA preparations from
S. aureus
,
B. subtilis
, and
S. sanguis
were not able to induce NO from lipopolysaccharide-hyporesponsive C3H/HeJ mouse peritoneal macrophages, but in the presence of IFN-γ, these LTA preparations were able to induce relatively high levels of NO from C3H/HeJ macrophages. These results indicate that commercially available LTA can contain contaminating and potentially significant levels of endotoxin that can be expected to contribute to the putative macrophage-stimulating effects of LTA as assessed by NO production. The fact that the purified LTA, by itself, was not able to induce significant levels of NO secretion in RAW 264.7 macrophages supports the conclusion that caution in attributing high-level biological activity to this microbial cell wall constituent should be exercised.
Pulmonary Inflammation Disrupts Surfactant Function duringPneumocystis cariniiPneumonia
Authors: Wright Terry W. , Notter Robert H. , Wang Zhengdong , Harmsen Allen G. , Gigliotti Francis 
Published: July 2002

ABSTRACTDuringPneumocystis cariniipneumonia (PCP) in mice, the degree of pulmonary inflammation correlates directly with the severity of lung function deficits. Therefore, studies were undertaken to determine whether the host inflammatory response contributes to PCP-related respiratory impairment, at least in part, by disrupting the pulmonary surfactant system. Protein and phospholipid content and surfactant activity were measured in the lavage fluid of infected mice in either the absence or presence of an inflammatory response. At 9 weeks postinfection withP. carinii, nonreconstituted SCID mice exhibited no signs of pulmonary inflammation, respiratory impairment, or surfactant dysfunction. Lavage fluid obtained from these mice had protein/phospholipid (Pr/PL) ratios (64% ± 4.7%) and minimum surface tension values (4.0 ± 0.9 mN/m) similar to those ofP. carinii-free control mice. However, when infected SCID mice were immunologically reconstituted, an intense inflammatory response ensued. Pr/PL ratios (218% ± 42%) and minimum surface tension values (27.2 ± 2.7 mN/m) of the lavage fluid were significantly elevated compared to those of the lavage fluid from infected, nonreconstituted mice (P< 0.05). To examine the specific role of CD8+T-cell-mediated inflammation in surfactant dysfunction during PCP, mice with defined T-cell populations were studied.P. carinii-infected, CD4+-depleted mice had elevated lavage fluid Pr/PL ratios (126% ± 20%) and elevated minimum surface tension values (16.3 ± 1.0 mN/m) compared to normal mice (P< 0.05). However, when infected mice were additionally depleted of CD8+cells, Pr/PL ratios were normal and surfactant activity was improved. These findings demonstrate that the surfactant pathology associated with PCP is related to the inflammatory process rather than being a direct effect ofP. carinii. Moreover, CD8+lymphocytes are involved in the mechanism leading to surfactant dysfunction.
Variant-Specific Surface Protein Switching inGiardia lamblia
Authors: Nash T. E. , Luján H. T. , Mowatt M. R. , Conrad J. T. 
Published: July 2002

ABSTRACTSurface antigen switching inGiardia lambliawas analyzed using monoclonal antibodies specific for two variant-specific surface proteins (VSPs). Two VSPs were detected on the surface of single trophozoites. Dual expression persisted for 13 h but disappeared at 36 h, as in other parasites that undergo surface antigenic variation.
Pseudomonas aeruginosa-Induced Apoptosis Involves Mitochondria and Stress-Activated Protein Kinases
Authors: Jendrossek Verena , Grassmé Heike , Mueller Ilka , Lang Florian , Gulbins Erich 
Published: July 2002

ABSTRACTPseudomonas aeruginosa, a gram-negative facultative pathogen, causes severe infections in immunocompromised and cystic fibrosis patients. However, the molecular details of the interaction betweenP. aeruginosaand mammalian cells are still largely unknown. Here we demonstrate that infection of human conjunctiva epithelial Chang cells with the well-characterizedP. aeruginosastrain PAO-I results in rapid induction of apoptosis. Apoptosis was mediated by mitochondrial alterations, in particular mitochondrial depolarization, synthesis of reactive oxygen intermediates, and release of cytochromec, as well as an activation of Jun N-terminal kinases (JNK). Stimulation of these events was dependent on upregulation of CD95 on infected cells, and a deficiency of CD95 or the CD95 ligand prevented mitochondrial changes, JNK activation, and apoptosis upon infection. Further, efficient apoptosis of Chang epithelial cells required infection with liveP. aeruginosa, adhesion but not invasion of the bacteria, and expression of the type III secretion system in PAO-I. The data indicate a type III secretion system-dependent, sequential activation of several signaling pathways byP. aeruginosaPAO-I, resulting in apoptosis of the infected cell.
Expression ofpls, a Gene Closely Associated with themecAGene of Methicillin-ResistantStaphylococcus aureus, Prevents Bacterial Adhesion In Vitro
Authors: Savolainen K. , Paulin L. , Westerlund-Wikström B. , Foster T. J. , Korhonen T. K. , Kuusela P. 
Published: July 2002

ABSTRACTTheplsgene, coding for a large surface protein of methicillin-resistantStaphylococcus aureus, was cloned from a strain which adheres poorly to several mammalian proteins. The structure ofplsrevealed three distinct repeat regions, one of which was a serine-aspartate repeat characteristic of the Clf-Sdr family of surface proteins in staphylococci. The lengths of the repeat regions varied in different clinical strains and could be used as epidemiological markers.plswas found to be closely associated with themecAgene by pulsed-field gel electrophoresis analysis ofSmaI-digested DNA. Aplsmutant constructed by allele replacement adhered well to immobilized fibronectin and immunoglobulin G, in contrast to the parental strain, suggesting that Pls could have a role in preventing adhesion at some stages during an infection.
Salmonella entericaSerovar-Host Specificity Does Not Correlate with the Magnitude of Intestinal Invasion in Sheep
Authors: Uzzau Sergio , Leori Guido S. , Petruzzi Valentino , Watson Patricia R. , Schianchi Giuseppe , Bacciu Donatella , Mazzarello Vittorio , Wallis Timothy S. , Rubino Salvatore 
Published: July 2002

ABSTRACTThe colonization of intestinal and systemic tissues bySalmonella entericaserovars with different host specificities was determined 7 days after inoculation of 1 to 2-month-old lambs. Following oral inoculation,S. entericaserovars Abortusovis, Dublin, and Gallinarum were recovered in comparable numbers from the intestinal mucosa, but serovar Gallinarum was recovered in lower numbers than the other serovars from systemic sites. The pattern of bacterial recovery from systemic sites following intravenous inoculation was similar. The magnitude of intestinal invasion was evaluated in ovine ligated ileal loops in vivo. Serovars Dublin and Gallinarum and the broad-host-rangeSalmonellaserovar Typhimurium were recovered in comparable numbers from ileal mucosa 3 h after loop inoculation, whereas the recovery of serovar Abortusovis was approximately 10-fold lower. Microscopic analysis of intestinal mucosae infected with serovars Typhimurium and Dublin showed dramatic morphological changes and infiltration of inflammatory cells, whereas mucosae infected with serovars Abortusovis and Gallinarum were indistinguishable from uninfected mucosae. Together these data suggest thatSalmonellaserovar specificity in sheep correlates with bacterial persistence at systemic sites. Intestinal invasion and avoidance of the host's intestinal inflammatory response may contribute to but do not determine the specificity of serovar Abortosovis for sheep. Intestinal invasion by serovar Abortusovis was significantly reduced after mutation ofinvHbut was not reduced following curing of the virulence plasmid, suggesting that theSalmonellapathogenicity island 1 influences but the virulence plasmid genes do not influence the ability of serovar Abortusovis to invade the intestinal mucosa in sheep.
Activation of Interleukin-1 Receptor-Associated Kinase by Gram-Negative Flagellin
Authors: Moors Marlena A. , Li Liwu , Mizel Steven B. 
Published: July 2002

ABSTRACTFlagellin from various species of gram-negative bacteria activates monocytes to produce proinflammatory cytokines. We have analyzed the pathway by whichSalmonella enteritidisflagellin (FliC) activates murine and human monocyte/macrophage-like cell lines. Since lipopolysaccharide (LPS), the principal immune stimulatory component of gram-negative bacteria, is known to signal through Toll-like receptor 4 (TLR4), we tested the possibility that FliC also signals via TLR4. When murine HeNC2 cells were stimulated with LPS in the presence of a neutralizing anti-TLR4 monoclonal antibody, tumor necrosis factor alpha (TNF-α) and nitric oxide (NO) production were markedly reduced. In contrast, FliC-mediated TNF-α and NO production were minimally affected by the anti-TLR4 antibody. Furthermore, FliC, unlike LPS, stimulated TNF-α production in the TLR4 mutant cell line, GG2EE, indicating that TLR4 is not essential for FliC-mediated signaling. To test the possibility that FliC signals via another TLR, we measured FliC-mediated activation of interleukin-1 (IL-1) receptor-associated kinase (IRAK), a central component in IL-1R/TLR signaling. FliC induced IRAK activation in HeNC2 and GG2EE cells as well as in the human promonocytic cell line THP-1. IRAK activation was rapid in HeNC2 cells, with maximal activity observed after 5 min of treatment with FliC. In addition, FliC-mediated IRAK activation exhibited the same concentration dependence as was demonstrated for the induction of TNF-α. These results represent the first demonstration of IRAK activation by a purified bacterial protein and strongly suggest that a TLR distinct from TLR4 is involved in the macrophage inflammatory response to FliC.
FlhA, a Component of the Flagellum Assembly Apparatus of
Pseudomonas aeruginosa
, Plays a Role in Internalization by Corneal Epithelial Cells
Authors: Fleiszig Suzanne M. J. , Arora Shiwani K. , Van Rajana , Ramphal Reuben 
Published: July 2002

ABSTRACT

Pseudomonas aeruginosa
invades various epithelial cell types in vitro and in vivo. The
P. aeruginosa
genome possesses a gene (
flhA
) which encodes a protein that is believed to be part of the export apparatus for flagellum assembly and which is homologous to
invA
of
Salmonella
spp. Because
invA
is required for invasion of
Salmonella
spp., a role for
flhA
in
P. aeruginosa
invasion was explored using cultured rabbit corneal epithelial cells. An
flhA
mutant of
P. aeruginosa
strain PAO1 was constructed and was shown to be nonmotile. Complementation with
flhA
in
trans
restored motility. Corneal cells were infected for 3 h with the wild type (PAO1), the
flhA
mutant, the
flhA
mutant complemented with
flhA
in
trans
, an
flhA
mutant containing the plasmid vector control, or an
fliC
mutant (nonmotile mutant control). Invasion was quantified by amikacin exclusion assays. Both the
flhA
and the
fliC
mutants invaded at a lower level than the wild-type strain did, suggesting that both
fliC
and
flhA
played roles in invasion. However, loss of motility was not sufficient to explain the reduced invasion by
flhA
mutants, since centrifugation of bacteria onto cells did not restore invasion to wild-type levels. Unexpectedly, the
flhA
mutant adhered significantly better to corneal epithelial cells than wild-type bacteria or the
fliC
mutant did. The percentage of adherent bacteria that invaded was reduced by ∼80% for the
flhA
mutant and ∼50% for the
fliC
mutant, showing that only part of the role of
flhA
in invasion involves
fliC
. Invasion was restored by complementing the
flhA
mutant with
flhA
in
trans
but not by the plasmid vector control. Intracellular survival assays, in which intracellular bacteria were enumerated after continued incubation in the presence of antibiotics, showed that although
flhA
and
fliC
mutants had a reduced capacity for epithelial cell entry, they were not defective in their ability to survive within those cells after entry. These results suggest that the flagellum assembly type III secretion system plays a role in
P. aeruginosa
invasion of epithelial cells. Since the
flhA
mutants were not defective in their ability to adhere to corneal epithelial cells, to retain viability at the cell surface, or to survive inside epithelial cells after entry, the role of
flhA
in invasion of epithelial cells is likely to occur during the process of bacterial internalization.