bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparison of Alteration of Cell Surface Carbohydrates of the Chinchilla Tubotympanum and Colonial Opacity Phenotype of
Streptococcus pneumoniae
during Experimental Pneumococcal Otitis Media with or without an Antecedent Influenza A Virus Infection
Authors: Tong H. H. , Grants I. , Liu X. , DeMaria T. F. 
Published: July 2002

ABSTRACT

Experimental and clinical studies suggest that influenza A virus promotes
Streptococcus pneumoniae
-induced otitis media; however, the mechanism underlying this synergistic interaction has not been completely defined. In this study, glycoconjugate expression patterns were evaluated on the cell surface in the chinchilla eustachian tube (ET) lumen of a cohort challenged intranasally (i.n.) with
S. pneumoniae
type 6A, which is predominantly transparent and a cohort with an antecedent influenza A virus infection, followed by i.n. inoculation with
S. pneumoniae
. The labeling patterns obtained with six lectin probes revealed that the binding of
Bandeiraea simplicifolia
lectin II, succinylated wheat germ agglutinin, and peanut agglutinin were significantly increased in the lumenal surface of the ET in the cohort infected with both pathogens compared to the cohort inoculated with only
S. pneumoniae
, which indicated that
N
-acetylglucosamine (GlcNAc) and
d
-galactose residues were exposed. A significant decreased labeling with
Sambucus nigra
agglutinin in the combined influenza A virus and pneumococcus infection cohort suggested that there were few sialic acid residues remaining in the ET epithelium. In addition, the colonial opacity of
S. pneumoniae
during the disease course was examined. The opaque phenotype was predominant among the pneumococcus isolates from the middle-ear fluid in the cohort infected with the both pathogens. Together, these data suggest that the synergic effect of influenza A virus and
S. pneumoniae
on the changes of the carbohydrate moieties in the ET epithelium and that the selection of the opaque variant may facilitate the pneumococcal invasion of the middle ear.
Inflammatory Cytokines Enhance the Interaction of
Mannheimia haemolytica
Leukotoxin with Bovine Peripheral Blood Neutrophils In Vitro
Authors: Leite F. , O'Brien S. , Sylte M. J. , Page T. , Atapattu D. , Czuprynski C. J. 
Published: July 2002

ABSTRACT

Mannheimia
(
Pasteurella
)
haemolytica
A1 produces several virulence factors that play an important role in the pathogenesis of bovine pneumonic pasteurellosis. Foremost among these is a leukotoxin (LKT) that specifically kills ruminant leukocytes. Recent evidence suggests that
M. haemolytica
LKT binding to bovine leukocytes is mediated by the β
2
-integrin CD11a/CD18 (lymphocyte function-associated antigen 1 [LFA-1]), which subsequently induces activation and cytolysis of these cells. Inflammatory cytokines, which are released during viral and bacterial infection, are reported to increase LFA-1 expression and conformational activation. We investigated the effects of the inflammatory cytokines interleukin-1β (IL-1β), tumor necrosis factor alpha (TNF-α), and gamma interferon (IFN-γ) on the interaction of
M. haemolytica
LKT with bovine peripheral blood neutrophils (PMNs). In this study we demonstrated, by flow cytometry, that bovine PMNs increased their binding to an anti-bovine LFA-1 monoclonal antibody (BAT75A) following in vitro incubation with IL-1β, TNF-α, or IFN-γ. Incubation with cytokines also increased CD18 expression, as assessed by real-time PCR and by Western blotting. Increased LFA-1 expression by PMNs exposed to cytokines was associated with increased LKT binding and cytotoxicity. The latter represented, at least in part, enhanced PMN apoptosis, as assessed by propidium iodine staining and caspase-3 activation. The results of this study suggest that inflammatory cytokines may play an important role in enhancing the biological response of bovine PMNs to
M. haemolytica
LKT.
Flavohemoglobin Hmp ProtectsSalmonella entericaSerovar Typhimurium from Nitric Oxide-Related Killing by Human Macrophages
Authors: Stevanin Tânia M. , Poole Robert K. , Demoncheaux Eric A. G. , Read Robert C. 
Published: July 2002

ABSTRACTSurvival of macrophage microbicidal activity is a prerequisite for invasive disease caused by the enteric pathogenSalmonella entericaserovar Typhimurium. Flavohemoglobins, such as those ofEscherichia coli,Salmonella, and yeast, play vital roles in protection of these microorganisms in vitro from nitric oxide (NO) and nitrosative stress. ASalmonella hmpmutant defective in flavohemoglobin (Hmp) synthesis exhibits growth that is hypersensitive to nitrosating agents. We found that respiration of this mutant exhibited increased inhibition by NO, whereas wild-type cells pregrown with sodium nitroprusside orS-nitrosoglutathione showed enhanced tolerance of NO. Most significantly,hmpmutants internalized by primary human peripheral monocyte-derived macrophages survived phagocytosis relatively poorly compared with similarly bound and internalized wild-type cells. That the enhanced sensitivity to macrophage microbicidal activity is due primarily to the failure ofSalmonellato detoxify NO was suggested by the ability ofl-NG-monomethyl arginine—an inhibitor of NO synthase—to eliminate the difference in killing between wild-type andhmpmutantSalmonellacells. These observations suggest thatSalmonellaHmp contributes to protection from NO-mediated inhibition by human macrophages.
Loss of Regulatory Protein RfaH Attenuates Virulence of Uropathogenic
Escherichia coli
Authors: Nagy Gábor , Dobrindt Ulrich , Schneider György , Khan A. Salam , Hacker Jörg , Emödy Levente 
Published: July 2002

ABSTRACT

RfaH is a regulatory protein in
Escherichia coli
and
Salmonella enterica
serovar Typhimurium. Although it enhances expression of different factors that are proposed to play a role in bacterial virulence, a direct effect of RfaH on virulence has not been investigated so far. We report that inactivation of
rfaH
dramatically decreases the virulence of uropathogenic
E. coli
strain 536 in an ascending mouse model of urinary tract infection. The mortality rate caused by the wild-type strain in this assay is 100%, whereas that of its isogenic
rfaH
mutant does not exceed 18%. In the case of coinfection, the wild-type strain 536 shows higher potential to colonize the urinary tract even when it is outnumbered 100-fold by its
rfaH
mutant in the inoculum. In contrast to the wild-type strain, serum resistance of strain 536
rfaH
::
cat
is fully abolished. Furthermore, we give evidence that, besides a major decrease in the amount of hemin receptor ChuA (G. Nagy, U. Dobrindt, M. Kupfer, L. Emody, H. Karch, and J. Hacker, Infect. Immun. 69:1924-1928, 2001), loss of the RfaH protein results in an altered lipopolysaccharide phenotype as well as decreased expression of K15 capsule and alpha-hemolysin, whereas levels of other pathogenicity factors such as siderophores, flagella, Prf, and S fimbriae appear to be unaltered in strain 536
rfaH
::
cat
in comparison to the wild-type strain.
trans c
omplementation of the mutant strain with the
rfaH
gene restores wild-type levels of the affected virulence factors and consequently restitutes virulence in the mouse model of ascending urinary tract infection.
Interleukin-10 Controls the Onset of Irreversible Septic Shock
Authors: Latifi Samir Q. , O'Riordan Mary Ann , Levine Alan D. 
Published: July 2002

ABSTRACTLethality from sepsis is believed to be mediated by a proinflammatory cytokine cascade, yet blocking the proinflammatory cytokines tumor necrosis factor alpha (TNF-α) and interleukin-1 (IL-1) fails to prevent mortality in human disease and a mouse model of sepsis induced by cecal ligation and puncture (CLP). The role of the antiinflammatory cytokine IL-10 in the CLP model of sepsis is unclear, with either protective or harmful effects demonstrated, depending upon the time of intervention. We therefore hypothesize that IL-10 functions as a temporal regulator of the transition from early reversible sepsis to the late phase of irreversible shock. Transition from reversible sepsis to irreversible shock in the CLP model was defined as the time when removal of the necrotic cecum by rescue surgery is no longer effective. We subjected IL-10-deficient (IL-10−/−) and wild-type (IL-10+/+) mice to CLP and monitored the progression of sepsis, the onset of irreversible shock, and mortality. Onset of lethality in IL-10−/−mice occurred significantly earlier than in IL-10+/+mice and was associated with 15-fold-higher serum levels of TNF-α and IL-6. Consistent with these findings, the efficacy of rescue surgery after lethal CLP is lost 10 h earlier in IL-10−/−mice than in IL-10+/+mice. Treatment with recombinant human IL-10 5 h after CLP significantly improved survival and lengthened the therapeutic window for rescue surgery in both strains of mice. These results demonstrate that IL-10 controls the onset of irreversible septic shock after CLP.
Autotransported Serine Protease A of
Neisseria meningitidis
: an Immunogenic, Surface-Exposed Outer Membrane, and Secreted Protein
Authors: Turner David P. J. , Wooldridge Karl G. , Ala'Aldeen Dlawer A. A. 
Published: July 2002

ABSTRACT

Several autotransporter proteins have previously been identified in
Neisseria meningitidis
. Using molecular features common to most members of the autotransporter family of proteins, we have identified an additional novel ca. 112-kDa autotransporter protein in the meningococcal genomic sequence data. This protein, designated autotransported serine protease A (AspA), has significant N-terminal homology to the secreted serine proteases (subtilases) from several organisms and contains a serine protease catalytic triad. The amino acid sequence of AspA is well-conserved in serogroup A, B, and C meningococci. In
Neisseria gonorrhoeae
, the AspA homologue appears to be a pseudogene. The gene encoding AspA was cloned and expressed from meningococcal strain MC58 (B15:P1.16b). Anti-AspA antibodies were detected in patients' convalescent-phase sera, suggesting that AspA is expressed in vivo during infection and is immunogenic and cross-reactive. Rabbit polyclonal monospecific anti-AspA serum was used to probe whole-cell proteins from a panel of wild-type meningococcal strains and two AspA mutant strains. Expression of the ca. 112-kDa precursor polypeptide was detected in 12 of 20 wild-type meningococcal strains examined, suggesting that AspA expression is phase variable. Immunogold electron microscopy and cellular fractionation studies showed that the AspA precursor is transported to the outer membrane and remains surface exposed. Western blot experiments confirmed that smaller, ca. 68- or 70-kDa components of AspA (AspA68 and AspA70, respectively) are then secreted into the meningococcal culture supernatant. Site-directed mutagenesis of S426 abolished secretion of both rAspA68 and rAspA70 in
Escherichia coli
, confirming that AspA is an autocleaved autotransporter protein. In conclusion, we characterized a novel, surface-exposed and secreted, immunogenic, meningococcal autotransporter protein.
Tumor Necrosis Factor Alpha Stimulates Killing ofMycobacterium tuberculosisby Human Neutrophils
Authors: Kisich Kevin O. , Higgins Michael , Diamond Gill , Heifets Leonid 
Published: July 2002

ABSTRACTThe ability of human neutrophils to aid in defense against pulmonary infection withMycobacterium tuberculosisis controversial. In this study, we have shown that neutrophils respond to and phagocytoseM. tuberculosisin human lesions. Neutrophils from healthy individuals were able to kill significant fractions of an inoculum ofM. tuberculosiswithin 1 h of phagocytosis, and this ability was enhanced by tumor necrosis factor alpha but not by gamma interferon. The mycobactericidal mechanism was nonoxidative, as inhibitors of reactive oxygen or reactive nitrogen intermediates did not interfere with killing. However, the mycobactericidal mechanism was associated with increased exposure of intracellularM. tuberculosisto neutrophil defensins. In vitro, human neutrophil peptides 1 to 3 were not able to kill the bacilli even at much higher levels. These studies support the concept that human neutrophils are directly involved in defense against infection withM. tuberculosis.
Acylation of the Lipooligosaccharide ofHaemophilus influenzaeand Colonization: anhtrBMutation Diminishes the Colonization of Human Airway Epithelial Cells
Authors: Swords W. Edward , Chance Deborah L. , Cohn Leah A. , Shao Jianqiang , Apicella Michael A. , Smith Arnold L. 
Published: July 2002

ABSTRACTHaemophilus influenzaeis a commensal and opportunistic pathogen of the human airways. A number of surface molecules contribute to colonization of the airways byH. influenzae, such as adhesins, including structures found in the lipooligosaccharide (LOS). A human bronchiolar xenograft model was employed to investigate the host-bacterial interactions involved in the colonization of the airway byH. influenzae. Differential display was used to identifyH. influenzaemRNA that reflect genes which were preferentially expressed in the xenograft compared to growth. Eleven mRNA fragments had consistent increased expression when the bacteria grew in xenografts. On sequencing these fragments, eight open reading frames were identified. Three of these had no match in the NCBI or the TIGR database, while an additional three were homologous to genes involved in heme or iron acquisition and utilization: two of the mRNAs encoded proteins homologous to enzymes involved in LOS biosynthesis: a heptosyl transferase (rfaF) involved in the synthesis of the LOS core and a ketodeoxyoctonate phosphate-dependent acyltransferase (htrB) that performs one of the late acylation reactions in lipid A synthesis. Inoculation of human bronchiolar xenografts revealed a significant reduction in colonization capacity byhtrBmutants. In vitro,htrBmutants elicited lesser degrees of cytoskeletal rearrangement and less stimulation of host cell signaling with 16HBE14o−cells and decreased intracellular survival. These results implicate acylation ofH. influenzaelipid A as playing a key role in the organisms' colonization of the normal airway.
Escherichia coli
Shiga-Like Toxins Induce Apoptosis and Cleavage of Poly(ADP-Ribose) Polymerase via In Vitro Activation of Caspases
Authors: Ching Joyce C. Y. , Jones Nicola L. , Ceponis Peter J. M. , Karmali Mohamed A. , Sherman Philip M. 
Published: July 2002

ABSTRACT

Shiga-like toxin-producing
Escherichia coli
causes hemorrhagic colitis and hemolytic-uremic syndrome in association with the production of Shiga-like toxins, which induce cell death via either necrosis or apoptosis. However, the abilities of different Shiga-like toxins to trigger apoptosis and the sequence of intracellular signaling events mediating the death of epithelial cells have not been completely defined. Fluorescent dye staining with acridine orange and ethidium bromide showed that Shiga-like toxin 1 (Stx1) induced apoptosis of HEp-2 cells in a dose- and time-dependent manner. Stx2 also induced apoptosis in a dose-dependent manner. Apoptosis induced by Stx1 (200 ng/ml) and apoptosis induced by Stx2 (200 ng/ml) were maximal following incubation with cells for 24 h (94.3% ± 1.8% and 81.7% ± 5.2% of the cells, respectively). Toxin-treated cells showed characteristic features of apoptosis, including membrane blebbing, DNA fragmentation, chromatin condensation, cell shrinkage, and the formation of apoptotic bodies, as assessed by transmission electron microscopy. Stx2c induced apoptosis weakly even at a high dose (1,000 ng/ml for 24 h; 26.7% ± 1.3% of the cells), whereas Stx2e did not induce apoptosis of HEp-2 cells. Thin-layer chromatography confirmed that HEp-2 cells express the Stx1-Stx2-Stx2c receptor, globotriaosylceramide (Gb3), but not the Stx2e receptor, globotetraosylceramide (Gb4). Western blot analysis of poly(ADP-ribose) polymerase (PARP), a DNA repair enzyme, demonstrated that incubation with Stx1 and Stx2 induced cleavage, whereas incubation with Stx2e did not result in cleavage of PARP. A pan-caspase inhibitor (Z-VAD-FMK) and a caspase-8-specific inhibitor (Z-IETD-FMK) eliminated, in a dose-dependent fashion, the cleavage of PARP induced by Shiga-like toxins. Caspase-8 activation was confirmed by detection of cleavage of this enzyme by immunoblotting. Cleavage of caspase-9 and the proapoptotic member of the Bcl-2 family BID was also induced by Stx1, as determined by immunoblot analyses. We conclude that different Shiga-like toxins induce different degrees of apoptosis that correlates with toxin binding to the glycolipid receptor Gb3 and that caspases play an integral role in the signal transduction cascade leading to toxin-mediated programmed cell death.
Identification of
Klebsiella pneumoniae
Genes Involved in Intestinal Colonization and Adhesion Using Signature-Tagged Mutagenesis
Authors: Maroncle Nathalie , Balestrino Damien , Rich Chantal , Forestier Christiane 
Published: July 2002

ABSTRACT

Klebsiella pneumoniae
is an opportunistic pathogen responsible for nosocomial infections that initially colonize the intestinal tract of patients. Signature-tagged mutagenesis was used to identify genes required for this function. A library of 2,200 mutants was analyzed for the inability of the mutants to survive in a murine model of intestinal colonization and to adhere to human intestinal cells (Int-407) in vitro. Twenty-nine attenuated mutants were selected for further analyses after competition assays against the wild-type strain. Whatever the screening model, most of the transposon insertions occurred in genes involved in metabolic pathways, membrane transport, DNA metabolism, transcriptional regulation, and unknown functions. Only one mutant was attenuated in both the murine colonization and the in vitro adhesion models, and the sequence disrupted by the transposon had homology to adhesin-encoding genes of
Haemophilus
sp.
Interleukin-8 Secretion fromMycobacterium tuberculosis-Infected Monocytes Is Regulated by Protein Tyrosine Kinases but Not by ERK1/2 or p38 Mitogen-Activated Protein Kinases
Authors: Ameixa Clara , Friedland Jon S. 
Published: July 2002

ABSTRACTMycobacterium tuberculosisupregulates NF-κB binding and interleukin-8 (IL-8) gene expression and secretion in primary human monocytes. Inhibition of tyrosine protein kinases but not of ERK1/2 or p38 mitogen-activated protein kinases downregulates tuberculosis-induced IL-8 secretion. The inhibitor genistein decreased NF-κB nuclear translocation and IL-8 gene transcription in addition to acting on posttranscriptional processing.
Phase Variation Analysis of
Coxiella burnetii
during Serial Passage in Cell Culture by Use of Monoclonal Antibodies
Authors: Hotta Akitoyo , Kawamura Midori , To Ho , Andoh Masako , Yamaguchi Tsuyoshi , Fukushi Hideto , Hirai Katsuya 
Published: July 2002

ABSTRACT

Antigenic changes in
Coxiella burnetii
Nine Mile strain phase I during serial passages in cell culture were analyzed with three groups of monoclonal antibodies (MAbs) against lipopolysaccharide. The MAbs of group 1 did not react with organisms that were passaged over five times, and the MAbs of group 2 did not react with organisms that were passaged over eight times. The MAbs of group 3 reacted with organisms passaged up to 15 times but did not react with phase II cells. These results suggest that
C. burnetii
could be differentiated into four phase states during phase variation.
Mice That Are Congenic for the
char2
Locus Are Susceptible to Malaria
Authors: Burt Rachel A. , Marshall Vikki M. , Wagglen Jamie , Rodda Fleur R. , Senyschen Danielle , Baldwin Tracey M. , Buckingham Lynn A. , Foote Simon J. 
Published: July 2002

ABSTRACT

A major advance has been made towards the positional cloning of
char2
(a quantitative trait locus encoding resistance to
Plasmodium chabaudi
malaria). Mice congenic for the locus have been used to fine map the gene and to prove that
char2
plays a significant role in the outcome of malarial infection, independently of other resistance loci.
ASalmonella entericaSerovar TyphimuriumhemAMutant Is Highly Susceptible to Oxidative DNA Damage
Authors: Elgrably-Weiss Maya , Park Sunny , Schlosser-Silverman Eliana , Rosenshine Ilan , Imlay James , Altuvia Shoshy 
Published: July 2002

ABSTRACTThe first committed step in the biosynthesis of heme, an important cofactor of two catalases and a number of cytochromes, is catalyzed by thehemAgene product.Salmonella entericaserovar TyphimuriumhemA26::Tn10d(hemA26) was identified in a genetic screen of insertion mutants that were sensitive to hydrogen peroxide. Here we show that thehemA26mutant respires at half the rate of wild-type cells and is highly susceptible to the effects of oxygen species. Exposure of thehemA26strain to hydrogen peroxide results in extensive DNA damage and cell death. The chelation of intracellular free iron fully abrogates the sensitivity of this mutant, indicating that the DNA damage results from the iron-catalyzed formation of hydroxyl radicals. The inactivation of heme synthesis does not change the amount of intracellular iron, but by diminishing the rate of respiration, it apparently increases the amount of reducing equivalents available to drive the Fenton reaction. We also report that hydrogen peroxide has opposite effects on the expression ofhemAandhemH, the first and last genes of heme biosynthesis pathway, respectively.hemAmRNA levels decrease, while the transcription ofhemHis induced by hydrogen peroxide, in anoxyR-dependent manner. TheoxyR-dependent induction is suppressed under conditions that accelerate the Fenton reaction by a mechanism that is not yet understood.
RelA Protein Is Involved in Induction of Genetic Competence in CertainBacillus subtilisStrains by Moderating the Level of Intracellular GTP
Authors: Inaoka Takashi , Ochi Kozo 
Published: July 2002

ABSTRACTWe found that the ability to develop genetic competence of a certain relaxed (relA) aspartate-auxotrophic strain ofBacillus subtilisis significantly lower than that of the isogenic stringent (relA+) strain. Transcriptional fusion analysis utilizing alacZreporter gene indicated that the amount of the ComK protein, known as the key protein for competence development, is greatly reduced in the relaxed strain than in the stringent strain. We also found that the addition of decoyinine, a GMP synthetase inhibitor, induces expression of a competence gene (comG) in the relaxed strain, accompanied by a pronounced decrease in the level of intracellular GTP as measured by high-performance liquid chromatography. The transformation efficiency of the relaxed strain increased 100-fold when decoyinine was added att0(the transition point between exponential to stationary growth phase). Conversely, supplementation of guanosine together with decoyinine completely abolished the observed effect of adding decoyinine on competence development. Furthermore, the impaired ability of the relaxed strain for competence development was completely restored by disrupting thecodYgene, which is known to negatively controlcomKexpression. Our results indicate that the RelA protein plays an essential role in the induction of competence development at least under certain physiological conditions by reducing the level of intracellular GTP and overcoming CodY-mediated regulation.