bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cloning and Sequencing of a Genomic Island Found in the Brazilian Purpuric Fever Clone of
Haemophilus influenzae
Biogroup Aegyptius
Authors: McGillivary Glen , Tomaras Andrew P. , Rhodes Eric R. , Actis Luis A. 
Published: March 2005

ABSTRACT

A genomic island was identified in the
Haemophilus influenzae
biogroup aegyptius Brazilian purpuric fever (BPF) strain F3031. This island, which was also found in other BPF isolates, could not be detected in non-BPF biogroup aegyptius strains or in nontypeable or typeable
H. influenzae
strains, with the exception of a region present in the type b Eagan strain. This 34,378-bp island is inserted, in reference to
H. influenzae
Rd KW20, within a choline transport gene and contains a mosaic structure of Mu-like prophage genes, several hypothetical genes, and genes potentially encoding an
Erwinia carotovora
carotovoricin Er-like bacteriocin. The product of the tail fiber ORF in the bacteriocin-like region shows a hybrid structure where the C terminus is similar to an
H. influenzae
phage HP1 tail protein implicating this open reading frame in altering host specificity for a putative bacteriocin. Significant synteny is seen in the entire genomic island with genomic regions from
Salmonella enterica
subsp.
enterica
serovar Typhi CT18,
Photorhabdus luminescens
subsp.
laumondii
TT01,
Chromobacterium violaceum
, and to a lesser extent
Haemophilus ducreyi
35000HP. In a previous work, we isolated several BPF-specific DNA fragments through a genome subtraction procedure, and we have found that a majority of these fragments map to this locus. In addition, several subtracted fragments generated from an independent laboratory by using different but related strains also map to this island. These findings underscore the importance of this BPF-specific chromosomal region in explaining some of the genomic differences between highly invasive BPF strains and non-BPF isolates of biogroup aegyptius.
The TibA Adhesin/Invasin from EnterotoxigenicEscherichia coliIs Self Recognizing and Induces Bacterial Aggregation and Biofilm Formation
Authors: Sherlock Orla , Vejborg Rebecca Munk , Klemm Per 
Published: March 2005

ABSTRACTEscherichia colistrains are responsible for many cases of gastrointestinal disease and represent a serious health problem worldwide. An essential step in the pathogenesis of such strains involves recognition and attachment to host intestinal surfaces. TibA is a potent bacterial adhesin associated with a number of enterotoxigenicE. colistrains and mediates bacterial attachment to a variety of human cells; additionally, it promotes invasion of such cells. This adhesin is a surface-displayed autotransporter protein and belongs to the exclusive group of bacterial glycoproteins; only the glycosylated form confers binding to and invasion of mammalian cells. Here we characterized TibA and showed that it possesses self-association characteristics and can mediate autoaggregation ofE. colicells. We demonstrated that intercellular TibA-TibA interaction is responsible for bacterial autoaggregation. Also, TibA expression significantly enhances biofilm formation byE. colion abiotic surfaces.
Interactions of
Neisseria gonorrhoeae
with Adherent Polymorphonuclear Leukocytes
Authors: Simons Mark P. , Nauseef William M. , Apicella Michael A. 
Published: March 2005

ABSTRACT

Neisseria gonorrhoeae
causes severe exudative urethritis. The exudates from infected individuals contain large numbers of polymorphonuclear leukocytes (PMN) with ingested gonococci. The fate of
N. gonorrhoeae
within PMN has been a topic of debate for years. In this study, we examined the interactions of
N. gonorrhoeae
with PMN adherent to surfaces as a system that better models events during clinical disease. Using chemiluminescence to measure reactive oxygen species (ROS), we found that
N. gonorrhoeae
stimulated PMN to produce a respiratory burst. Different kinetics were seen when PMN were stimulated with opsonized zymosan particles. In addition, ROS were produced predominantly inside the PMN in response to gonococci. Laser scanning confocal microscopy and transmission electron microscopy showed that
N. gonorrhoeae
rapidly associated with PMN under these experimental conditions and was internalized. Some gonococci were cleared in the first 30 to 60 min after phagocytosis, but a majority of the population persisted for 6 h after phagocytosis. Quantification of viable organisms showed that a significant portion of the population resisted killing. The viability of this subpopulation remained unchanged for 2 h after phagocytosis. A significant increase of viable gonococci from 1 to 6 h was also observed, suggesting intracellular replication. Four different
N. gonorrhoeae
strains demonstrated the same capacity to resist PMN-mediated killing, whereas
Escherichia coli
was rapidly killed by PMN under the same conditions. Taken together, these findings suggest that a subpopulation of
N. gonorrhoeae
resists killing and replicates within PMN phagosomes in spite of NADPH oxidase activation.
Differential Involvement of Toll-Like Receptors 2 and 4 in the Host Response to Acute Respiratory Infections with Wild-Type and MutantHaemophilus influenzaeStrains
Authors: Lorenz Eva , Chemotti Diana C. , Jiang Alice L. , McDougal Letitia D. 
Published: March 2005

ABSTRACTWe used a mouse model of acute respiratory infections to investigate the role of Toll-like receptor 2 (TLR2) and TLR4 in the host response toHaemophilus influenzae. Acute aerosol exposures to wild-type strains ofH. influenzaeshowed that TLR4 function was essential for TNF-α induction, neutrophil influx, and bacterial clearance. To determine how lipooligosaccharide (LOS) modifications would affect the role of TLR4 in inducing the host response, we used acute infections with anH. influenzaestrain expressing a mutation in thehtrBgene. This mutant strain expresses an LOS subunit with decreased acylation. In response toH. influenzae htrBinfection, tumor necrosis factor alpha (TNF-α) secretion remained TLR4 dependent. But the decrease in LOS acylation made the neutrophil influx and the bacterial clearance also dependent on TLR2, as shown by the decreased host response elicited in TLR2 knockout mice compared to C57BL/6 mice. A subsequent analysis of TLR2 and TLR4 gene expression by quantitative PCR indicated that TLR4 function induces TLR2 expression and vice versa. These results indicate that some changes in the LOS subunit ofH. influenzaecan favor signaling through non-TLR4 receptors, such as TLR2. The results also indicate a close interaction between TLR4 and TLR2 that tightly regulates the expression of both receptors.
A Deficiency in Gamma Interferon or Interleukin-10 Modulates T-Cell-Dependent Responses to Heat Shock Protein 60 fromHistoplasma capsulatum
Authors: Scheckelhoff Mark , Deepe George S. 
Published: March 2005

ABSTRACTImmunization of mice with heat shock protein 60 fromHistoplasma capsulatumor a polypeptide from the protein designated F3 confers protection. Vβ8.1/8.2+T cells are critically important for the protective efficacy of this antigen. The production of interleukin-10 and gamma interferon following vaccination is essential for efficacy. In this study, we sought to determine whether the absence of either cytokine modified the repertoire of antigen-reactive T cells and whether it altered the functional properties of T cells. Mice lacking gamma interferon or interleukin-10 manifested a skewed repertoire compared to that of wild-type mice. The bias was most marked in gamma interferon-deficient mice and modestly altered in interleukin-10-deficient animals. The altered repertoire in gamma interferon-deficient mice could not be explained at the level of antigen presentation or by the absence of this population from mice. The proportion of T cells from interleukin-10-deficient mice manifesting a Th1 phenotype was greatly increased compared to that from wild-type animals. Transfer of splenocytes from gamma interferon- or interleukin-10-deficient mice immunized with heat shock protein 60 failed to confer protection in T-cell receptor α/β−/−mice. The transfer of T-cell clones that did not produce both cytokines failed to prolong survival in T-cell receptor α/β−/−mice, whereas the clones with the same features that were derived from wild-type mice did. These results indicate that the cytokine milieu influences the shape of the T-cell receptor repertoire and support the importance of gamma interferon and interleukin-10 in the efficacy of heat shock protein 60.
Surfactant Protein D Is Present in Human Tear Fluid and the Cornea and Inhibits Epithelial Cell Invasion byPseudomonas aeruginosa
Authors: Ni Minjian , Evans David J. , Hawgood Samuel , Anders E. Margot , Sack Robert A. , Fleiszig Suzanne M. J. 
Published: March 2005

ABSTRACTWe have previously shown that human tear fluid protects corneal epithelial cells againstPseudomonas aeruginosain vitro and in vivo and that protection does not depend upon tear bacteriostatic activity. We sought to identify the responsible tear component(s). The hypothesis tested was that collectins (collagenous calcium-dependent lectins) were involved. Reflex tear fluid was collected from healthy human subjects and examined for collectin content by enzyme-linked immunosorbent assay (ELISA) and Western blot with antibody against surfactant protein D (SP-D), SP-A, or mannose-binding lectin (MBL). SP-D, but not SP-A or MBL, was detected by ELISA of human reflex tear fluid. Western blot analysis of whole tears and of high-performance liquid chromatography tear fractions confirmed the presence of SP-D, most of which eluted in the same fraction as immunoglobulin A. SP-D tear concentrations were calculated at ∼2 to 5 μg/ml. Depletion of SP-D with mannan-conjugated Sepharose or anti-SP-D antibody reduced the protective effect of tears againstP. aeruginosainvasion. Recombinant human or mouse SP-D used alone reducedP. aeruginosainvasion of epithelial cells without detectable bacteriostatic activity or bacterial aggregation. Immunofluorescence microscopy revealed SP-D antibody labeling throughout the corneal epithelium of normal, but not gene-targeted SP-D knockout mice. SP-D was also detected in vitro in cultured human and mouse corneal epithelial cells. In conclusion, SP-D is present in human tear fluid and in human and mouse corneal epithelia. SP-D is involved in human tear fluid protection againstP. aeruginosainvasion. Whether SP-D plays other roles in the regulation of other innate or adaptive immune responses at the ocular surface, as it does in the airways, remains to be explored.
Differential Effects of Prior Exposure to Environmental Mycobacteria on Vaccination withMycobacterium bovisBCG or a Recombinant BCG Strain Expressing RD1 Antigens
Authors: Demangel Caroline , Garnier Thierry , Rosenkrands Ida , Cole Stewart T. 
Published: March 2005

ABSTRACTIn silico analysis reveals that most protective antigens expressed by the antituberculous vaccineMycobacterium bovisBCG (BCG) are conserved inM. avium, supporting the hypothesis that exposure to environmental mycobacteria generates cross-reactive immune responses blocking BCG activity. We investigated the impact of sensitization withM. avium,M. scrofulaceum, orM. vaccaeon the protective efficacy of a recombinant BCG strain expressing RD1 antigens (BCG::RD1), using a mouse model of experimental tuberculosis (TB). No evidence that the RD1-encoded antigens ESAT-6, CFP-10, and PPE68 were expressed by these environmental strains could be demonstrated by Western blot analysis. Mice sensitized with each of these strains did not prime cellular immune responses cross-reacting with the immunodominant ESAT-6. Importantly, clearance of BCG::RD1 from the lungs and spleens of mice exposed to each of the environmental strains before vaccination was minimal compared to that of BCG. In mice sensitized withM. avium, increased persistence of BCG::RD1 correlated with stronger antimycobacterial gamma interferon responses and enhanced protection against aerosol infection withM. tuberculosis, compared to BCG. In contrast, animals exposed toM. scrofulaceumorM. vaccaeprior to vaccination with BCG or BCG::RD1 were better protected against TB than were the unsensitized controls. Our results suggest that the inhibitory effect of environmental mycobacteria on the protective efficacy of BCG depends critically on the extent of cross-recognition of antigens shared with the vaccine. In hosts sensitized withM. avium, potent immunogenicity of ESAT-6 and increased persistence of BCG::RD1 may allow this recombinant vaccine to overcome preexisting antimycobacterial responses.
Elucidation of the Monoclonal Antibody 5G8-Reactive, Virulence-Associated Lipopolysaccharide Epitope ofHaemophilus influenzaeand Its Role in Bacterial Resistance to Complement-Mediated Killing
Authors: Griffin Ruth , Cox Andrew D. , Makepeace Katherine , Richards James C. , Moxon E. Richard , Hood Derek W. 
Published: March 2005

ABSTRACTThe phase-variable locuslex2is required for expression of aHaemophilus influenzaelipopolysaccharide (LPS) epitope of previously unknown structure. This epitope, which is reactive with monoclonal antibody (MAb) 5G8, has been associated with virulence of type b strains. When strain RM118 (from the same source as strain Rd), in which thelex2locus and MAb 5G8 reactivity are absent, was transformed withlex2DNA, transformants that were reactive with MAb 5G8 were obtained. Surprisingly, the 5G8 reactivity of these transformants was phase variable, although thelex2locus lacked tetrameric repeats and was constitutively expressed. This phase variation was shown to be the result of phase-variable expression of phosphorylcholine (PCho) such that MAb 5G8 reacted only in the absence of PCho. Structural analysis showed that, compared to RM118, thelex2transformant had acquired a tetrasaccharide, Gal-α1,4-Gal-β1,4-Glc-β1,4-Glc-β1,4, linked to the proximal heptose (HepI). A terminal GalNAc was detected in a minority of glycoforms. LPS derived from a mutant of RM7004, a virulent type b strain which naturally expresseslex2and has LPS containing the same tetrasaccharide linked to HepI as the sole oligosaccharide extension from the inner core, confirmed that GalNAc is not a part of the MAb 5G8-reactive epitope. Thus, MAb 5G8 specifically binds to the structure Gal-α1,4-Gal-β1,4-Glc-β1,4-Glc-β attached via a 1,4 linkage to HepI ofH. influenzaeLPS, and we show that the ability to synthesize this novel tetrasaccharide was associated with enhanced bacterial resistance to complement-mediated killing.
Function of Neisserial Outer Membrane Phospholipase A in Autolysis and Assessment of Its Vaccine Potential
Authors: Bos Martine P. , Tefsen Boris , Voet Pierre , Weynants Vincent , van Putten Jos P. M. , Tommassen Jan 
Published: March 2005

ABSTRACT

Outer membrane phospholipase A (OMPLA) is an outer membrane-localized enzyme, present in many gram-negative bacterial species. It is implicated in the virulence of several pathogens. Here, we investigated the presence, function, and vaccine potential of OMPLA in the human pathogen
Neisseria meningitidis
. Immunoblot analysis showed the presence of OMPLA in 28 out of 33 meningococcal strains investigated. The OMPLA-negative strains all contained a
pldA
gene, but these alleles contained premature stop codons. All six
Neisseria gonorrhoeae
strains tested, but only two out of seven commensal neisserial strains investigated, expressed OMPLA, showing that OMPLA is expressed by, but not limited to, many pathogenic neisserial strains. The function of OMPLA was investigated by assessing the phenotypes of isogenic strains, expressing no OMPLA, expressing wild-type levels of OMPLA, or overexpressing OMPLA. OMPLA exhibited phospholipase activity against endogenous phospholipids. Furthermore, OMPLA was characterized as an autolysin that acted under specific conditions, such as prolonged growth of the bacteria. The vaccine potential of the protein was investigated by immunizing mice with in vitro refolded, recombinant OMPLA. High levels of antibody titers were obtained, but the murine sera were neither bactericidal nor protective. Also, convalescent patients and vaccinee sera did not contain detectable levels of anti-OMPLA antibodies, indicating that OMPLA may not be sufficiently immunogenic to be included in a meningococcal vaccine.
The Natural Killer Complex Regulates Severe Malarial Pathogenesis and Influences Acquired Immune Responses toPlasmodium bergheiANKA
Authors: Hansen Diana S. , Evans Krystal J. , D'Ombrain Marthe C. , Bernard Nicholas J. , Sexton Adrienne C. , Buckingham Lynn , Scalzo Anthony A. , Schofield Louis 
Published: March 2005

ABSTRACTThe natural killer complex (NKC) is a genetic region of highly linked genes encoding several receptors involved in the control of NK cell function. The NKC is highly polymorphic, and allelic variability of various NKC loci has been demonstrated in inbred mice. Making use of BALB.B6-Cmv1rcongenic mice, in which the NKC from disease-susceptible C57BL/6 mice has been introduced into the disease-resistant BALB/c background, we show here that during murine malaria infection, the NKC regulates a range of pathophysiological syndromes such as cerebral malaria, pulmonary edema, and severe anemia, which contribute to morbidity and mortality in human malaria. Parasitemia levels were not affected by the NKC genotype, indicating that control of malarial fatalities by the NKC cells does not operate through effects on parasite growth rate. Parasite-specific antibody responses and the proinflammatory gene transcription profile, as well as the TH1/TH2 balance, also appeared to be influenced by NKC genotype, providing evidence that this region, known to control innate immune responses via NK and/or NK T-cell activation, can also significantly regulate acquired immunity to infection. To date, NKC-encoded innate system receptors have been shown mainly to regulate viral infections. Our data provide evidence for critical NKC involvement in the broad immunological responses to a protozoan parasite.
Mouse Paneth Cell Secretory Responses to Cell Surface Glycolipids of Virulent and Attenuated Pathogenic Bacteria
Authors: Tanabe Hiroki , Ayabe Tokiyoshi , Bainbridge Brian , Guina Tina , Ernst Robert K. , Darveau Richard P. , Miller Samuel I. , Ouellette Andre J. 
Published: March 2005

ABSTRACTMouse Paneth cells respond to bacteria and bacterial cell surface antigens by discharging secretory granules into the lumen of small intestinal crypts (T. Ayabe et al., Nat. Immunol.1:113-118, 2000). To investigate mechanisms regulating these responses, purified surface glycolipid molecules with known acyl chain modifications and attenuated properties were tested for the ability to stimulate Paneth cell secretion. The antigens included lipopolysaccharide (LPS) from wild-type andmsbB-nullEscherichia coliandphoP-null andphoP-constitutiveSalmonella entericaserovar Typhimurium strains, as well as LPS, lipid A, and lipoteichoic acid fromPseudomonas aeruginosaandListeria monocytogenesgrown in Mg2+-limited media. Measurements of total secreted protein, secreted lysozyme, and the bactericidal peptide activities of collected secretions showed that the purified antigens elicited similar secretory responses from Paneth cells in mouse crypts ex vivo, regardless of glycolipid acyl chain modification. Despite their impaired Tlr4 pathway, Paneth cells in ex vivo C3H/HeJ mouse crypts released equivalent amounts of bactericidal peptide activity in response to purified bacterial antigens, including lipid A. Thus, mouse Paneth cells respond equivalently to purified bacterial cell envelope glycolipids, regardless of functional Tlr4, the structural properties of glycolipid acyl chains, or their association with virulence in humans.
Gene Expression inPorphyromonas gingivalisafter Contact with Human Epithelial Cells
Authors: Hosogi Yumiko , Duncan Margaret J. 
Published: March 2005

ABSTRACTPorphyromonas gingivalis, a gram-negative oral anaerobe, is strongly associated with adult periodontitis. The adherence of the organism to host epithelium signals changes in both cell types as bacteria initiate infection and colonization and epithelial cells rally their defenses. We hypothesized that the expression of a defined set ofP. gingivalisgenes would be consistently up-regulated during infection of HEp-2 human epithelial cells.P. gingivalisgenome microarrays were used to compare the gene expression profiles of bacteria that adhered to HEp-2 cells and bacteria that were incubated alone. Genes whose expression was temporally up-regulated included those involved in the oxidative stress response and those encoding heat shock proteins that are essential to maintaining cell viability under adverse conditions. The results suggest that contact with epithelial cells induces inP. gingivalisstress-responsive pathways that promote the survival of the bacterium.
The UspA2 Protein of
Moraxella catarrhalis
Is Directly Involved in the Expression of Serum Resistance
Authors: Attia Ahmed S. , Lafontaine Eric R. , Latimer Jo L. , Aebi Christoph , Syrogiannopoulos George A. , Hansen Eric J. 
Published: March 2005

ABSTRACT

Many strains of
Moraxella catarrhalis
are resistant to the bactericidal activity of normal human serum. Previous studies have shown that mutations involving the insertion of an antibiotic resistance cartridge into the
M. catarrhalis uspA2
gene resulted in the conversion of a serum-resistant strain to a serum-sensitive phenotype. In the present study, the deletion of the entire
uspA2
gene from the serum-resistant
M. catarrhalis
strain O35E resulted in a serum-sensitive phenotype and did not affect either the rate of growth or the lipooligosaccharide expression profile of this mutant. Inactivation of the classical complement pathway in normal human serum with Mg
2+
and EGTA resulted in the survival of this
uspA2
mutant. In contrast, blocking of the alternative complement pathway did not protect this
uspA2
mutant from complement-mediated killing. To determine whether the UspA2 protein is directly involved in serum resistance, transformation and allelic exchange were used to replace the
uspA2
gene in the serum-resistant strain O35E with the
uspA2
gene from the serum-sensitive
M. catarrhalis
strain MC317. The resultant O35E transformant exhibited a serum-sensitive phenotype. Similarly, when the
uspA2
gene from the serum-resistant strain O35E was used to replace the
uspA2
gene in the serum-sensitive strain MC317, the MC317 transformant acquired serum resistance. The use of hybrid O35E-MC317
uspA2
genes showed that the N-terminal half of the O35E protein contained a 102-amino-acid region that was involved in the expression of serum resistance. In addition, when the
uspA2
genes from strains O35E and MC317 were cloned and expressed in
Haemophilus influenzae
DB117, only the O35E UspA2 protein caused a significant increase in the serum resistance of the
H. influenzae
recombinant strain. These results prove that the UspA2 protein is directly involved in the expression of serum resistance by certain
M. catarrhalis
strains.