bluuebunny/crossref_metadata_2025_split huggingface dataset:
Immunomodulatory Role of Endogenous Interleukin-18 in Gamma Interferon-Mediated Resolution of ReplicativeLegionella pneumophilaLung Infection
Authors: Brieland Joan K. , Jackson Craig , Hurst Steve , Loebenberg David , Muchamuel Tony , Debets Reno , Kastelein Rob , Churakova Tatyana , Abrams John , Hare Roberta , O'Garra Anne 
Published: July 2002

ABSTRACTThe in vivo role of endogenous interleukin-18 (IL-18) in modulating gamma interferon (IFN-γ)-mediated resolution of replicativeLegionella pneumophilalung infection was assessed using a murine model of Legionnaires' disease. Intratracheal inoculation of A/J mice with virulent bacteria (106L. pneumophilaorganisms per mouse) resulted in induction of IL-18 protein in bronchoalveolar lavage fluid (BALF) and intrapulmonary expression of IL-18 mRNA. Real-time quantitative RT-PCR analysis of infected lung tissue demonstrated that induction of IL-18 in BALF preceded induction of IL-12 and IFN-γ mRNAs in the lung. Blocking intrapulmonary IL-18 activity by administration of a monoclonal antibody (MAb) to the IL-18 receptor (anti-IL-18R MAb) prior toL. pneumophilainfection inhibited induction of intrapulmonary IFN-γ production but did not significantly alter resolution of replicativeL. pneumophilalung infection. In contrast, blocking endogenous IL-12 activity by administration of anti-IL-12 MAb) alone or in combination with anti-IL-18R MAb inhibited induction of intrapulmonary IFN-γ and resulted in enhanced intrapulmonary growth of the bacteria within 5 days postinfection. Taken together, these results demonstrate that IL-18 plays a key role in modulating induction of IFN-γ in the lung in response toL. pneumophilaand that together with IL-12, IL-18 regulates intrapulmonary growth of the bacteria.
Activation of Human Peripheral Blood Mononuclear Cells by Nonpathogenic Bacteria In Vitro: Evidence of NK Cells as Primary Targets
Authors: Haller D. , Blum S. , Bode C. , Hammes W. P. , Schiffrin E. J. 
Published: July 2002

ABSTRACTThe interaction of commensal bacteria with immunocompetent cells may occur in definite compartments of the mucosal immune system, as limited translocation through the epithelial barrier cannot be excluded. In this study the stimulation of human peripheral blood mononuclear cells and purified lymphocyte subsets by nonpathogenic gram-positive lactobacilli (Lactobacillus johnsoniiandLactobacillus sakei) and gram-negativeEscherichia coliwas investigated. The various bacterial strains induced a differential cytokine pattern. WhereasL. johnsoniiandL. sakeistrongly induced gamma interferon (IFN-γ) and interleukin-12 (IL-12),E. coliand lipopolysaccharide (LPS) preferentially induced IL-10 after 16 h of stimulation. Expression of activation antigens CD69 and CD25 was observed on (CD3−CD56+) natural killer (NK) cells after stimulation of total human peripheral blood mononuclear cells. All bacteria mediated the proliferation of human peripheral blood mononuclear cells, and the strongest proliferative response was observed withL. johnsonii. Purified CD4+, CD8+, and CD19+lymphocyte subsets were not activated upon bacterial stimulation but showed normal response to a mitogenic stimulus. In contrast, purified NK cells upregulated the IL-2Rα chain (CD25) and underwent proliferation when stimulated byL. johnsonii. E. coliand LPS were less effective in inducing proliferation. Expression of CD25 or secretion of IFN-γ from purified NK cells was significantly increased in the presence of bacterially primed macrophages, indicating that full activation required both bacterium- and cell contact-based signals derived from accessory cells.
Role of Group A Streptococcal Virulence Factors in Adherence to Keratinocytes
Authors: Darmstadt Gary L. , Mentele Laurel , Podbielski Andreas , Rubens Craig E. 
Published: July 2002

ABSTRACTTo evaluate the role of putative group A streptococcal virulence factors in the initiation of skin infections, we compared the adherence of a wild-type M49-protein skin-associated strain to that of a series of 16 isogenic mutants created by insertional inactivation of virulence genes. None of the mutants, including the M-protein-deficient (emmmutant) strain, displayed reduced adherence to early-passage cultured human keratinocytes, but adherence of the mutant lacking hyaluronic acid capsule expression (hasmutant) was increased 13-fold. In contrast, elimination of capsule expression in M2-, M3-, and M18-proteinhasmutants increased adherence only slightly (1.3- to 2.3-fold) compared to their respective wild-type strains. A mutant with inactivation of bothemmandhasdisplayed high-level adherence (34.9 ± 4.1%) equal to that of thehasmutant strain (40.7 + 8.0%), confirming the lack of involvement of M49 protein in attachment. Moreover, adherence of the M49-protein-deficient (emmmutant) and wild-type strains was increased to the same level (57 and 55%, respectively) following enzymatic digestion of their hyaluronic acid capsule. Adherence of mutants lacking oligopeptide permease (Opp) expression was increased 3.8- to 5.5-fold, in association with decreased cell-associated hyaluronic acid capsule. Finally, soluble CD46 failed to inhibit adherence of M49- and M52-serotype skin strains. We conclude that (i) bacterial M protein and keratinocyte CD46 do not mediate adherence of M49 skin-associatedStreptococcus pyogenesto epidermal keratinocytes, (ii) hyaluronic acid capsule impedes the interaction of bacterial adhesins with keratinocyte receptors, (iii) modulation of capsule expression may be important in the pathogenesis of skin infections, and (iv) the molecular interactions in attachment of skin strains ofS. pyogenesto keratinocytes are unique and remain unidentified.
Cloning of the
Streptococcus mutans
Gene Encoding Glucan Binding Protein B and Analysis of Genetic Diversity and Protein Production in Clinical Isolates
Authors: Mattos-Graner Renata O. , Jin Song , King William F. , Chen Tsute , Smith Daniel J. , Duncan Margaret J. 
Published: July 2002

ABSTRACT

Streptococcus mutans
, the primary etiological agent of dental caries, produces several activities that promote its accumulation within the dental biofilm. These include glucosyltransferases, their glucan products, and proteins that bind glucan. At least three glucan binding proteins have been identified, and GbpB, the protein characterized in this study, appears to be novel. The
gbpB
gene was cloned and the predicted protein sequence contained several unusual features and shared extensive homology with a putative peptidoglycan hydrolase from group B streptococcus. Examination of
gbpB
genes from clinical isolates of
S. mutans
revealed that DNA polymorphisms, and hence amino acid changes, were limited to the central region of the gene, suggesting functional conservation within the amino and carboxy termini of the protein. The GbpB produced by clinical isolates and laboratory strains showed various distributions between cells and culture medium, and amounts of protein produced by individual strains correlated positively with their ability to grow as biofilms in an in vitro assay.
Localization of Functional Domains of the Mitogenic Toxin of
Pasteurella multocida
Authors: Pullinger Gillian D. , Sowdhamini R. , Lax Alistair J. 
Published: July 2002

ABSTRACT

The locations of the catalytic and receptor-binding domains of the
Pasteurella multocida
toxin (PMT) were investigated. N- and C-terminal fragments of PMT were cloned and expressed as fusion proteins with affinity tags. Purified fusion proteins were assessed in suitable assays for catalytic activity and cell-binding ability. A C-terminal fragment (amino acids 681 to 1285) was catalytically active. When microinjected into quiescent Swiss 3T3 cells, it induced changes in cell morphology typical of toxin-treated cells and stimulated DNA synthesis. An N-terminal fragment with a His tag at the C terminus (amino acids 1 to 506) competed with full-length toxin for binding to surface receptors and therefore contains the cell-binding domain. The inactive mutant containing a mutation near the C terminus (C1165S) also bound to cells in this assay. Polyclonal antibodies raised to the N-terminal PMT region bound efficiently to full-length native toxin, suggesting that the N terminus is surface located. Antibodies to the C terminus of PMT were microinjected into cells and inhibited the activity of toxin added subsequently to the medium, confirming that the C terminus contains the active site. Analysis of the PMT sequence predicted a putative transmembrane domain with predicted hydrophobic and amphipathic helices near the N terminus over the region of homology to the cytotoxic necrotizing factors. The C-terminal end of PMT was predicted to be a mixed α/β domain, a structure commonly found in catalytic domains. Homology to proteins of known structure and threading calculations supported these assignments.
Identification of the
sigB
Operon in
Staphylococcus epidermidis
: Construction and Characterization of a
sigB
Deletion Mutant
Authors: Kies Stefanie , Otto Michael , Vuong Cuong , Götz Friedrich 
Published: July 2002

ABSTRACT

The role of the alternative sigma factor ς
B
in
Staphylococcus epidermidis
was investigated by the construction, complementation, and characterization of a
sigB
deletion mutant. Electrophoretic analyses confirmed a profound influence of ς
B
on the expression of exoproteins and cytoplasmic proteins. Detailed investigation revealed reduced lipase and enhanced protease activity in the ς
B
mutant. Furthermore, no significant influence of ς
B
on heterologous biofilm formation or on the activity of the global regulator
agr
was detected.
Interleukin-10 StimulatesCoxiella burnetiiReplication in Human Monocytes through Tumor Necrosis Factor Down-Modulation: Role in Microbicidal Defect of Q Fever
Authors: Ghigo Eric , Capo Christian , Raoult Didier , Mege Jean-Louis 
Published: July 2002

ABSTRACTCoxiella burnetii, an obligate intracellular bacterium, is the agent of Q fever. The chronic form of the disease is associated with the overproduction of interleukin-10 and deficientC. burnetiikilling by monocytes. We hypothesized that the replication ofC. burnetiiinside monocytes requires a macrophage-deactivating cytokine such as interleukin-10. In the absence of interleukin-10,C. burnetiisurvived but did not replicate in monocytes.C. burnetiireplication (measured 15 days) was induced in interleukin-10-treated monocytes. This effect of interleukin-10 is specific since transforming growth factor β1 had no effect on bacterial replication.C. burnetiireplication involves the down-modulation of tumor necrosis factor (TNF) release. First, interleukin-10 suppressedC. burnetii-stimulated production of TNF. Second, the addition of recombinant TNF to interleukin-10-treated monocytes inhibited bacterial replication. Third, the incubation of infected monocytes with neutralizing anti-TNF antibodies favoredC. burnetiireplication. On the other hand, deficientC. burnetiikilling by monocytes from patients with chronic Q fever involves interleukin-10. Indeed,C. burnetiireplication was observed in monocytes from patients with Q fever endocarditis, but not in those from patients with acute Q fever. Bacterial replication was inhibited by neutralizing anti-interleukin-10 antibodies. As monocytes from patients with endocarditis overproduced interleukin-10, the defective bacterial killing is likely related to endogenous interleukin-10. These results suggest that interleukin-10 enables monocytes to supportC. burnetiireplication and to favor the development of chronic Q fever.
Mannan-Binding Lectin Enhances Susceptibility to Visceral Leishmaniasis
Authors: de Miranda Santos Isabel K. F. , Costa Carlos H. N. , Krieger Henrique , Feitosa Mary F. , Zurakowski David , Fardin Babak , Gomes Regis B. B. , Weiner Debra L. , Harn Donald A. , Ezekowitz R. Alan B. , Epstein Judith E. 
Published: July 2002

ABSTRACTLevels of the serum opsonin mannan-binding lectin (MBL) were directly correlated with the probability of developing visceral leishmaniasis. Monocytes infected with MBL-opsonizedLeishmania chagasipromastigotes secreted higher levels of tumor necrosis factor alpha and interleukin-6 than cells infected with nonopsonized parasites. Our findings indicate that MBL can modulate the clinical outcome of infection withL. chagasiand the function of infected macrophages.
Functional Differences among FimA Variants of
Porphyromonas gingivalis
and Their Effects on Adhesion to and Invasion of Human Epithelial Cells
Authors: Nakagawa Ichiro , Amano Atsuo , Kuboniwa Masae , Nakamura Takayuki , Kawabata Shigetada , Hamada Shigeyuki 
Published: July 2002

ABSTRACT

Fimbriae of
Porphyromonas gingivalis
, a periodontopathogen, play an important role in its adhesion to and invasion of host cells. The
fimA
genes encoding fimbrillin (FimA), a subunit protein of fimbriae, have been classified into five types, types I to V, based on nucleotide sequences. We previously reported that
P. gingivalis
with type II
fimA
was strongly associated with adult periodontitis. In the present study, we compared the abilities of recombinant FimA (rFimA) types I to V to adhere to and invade human gingival fibroblasts (HGF) and a human epithelial cell line (HEp-2 cells) by using rFimA-conjugated microspheres (rFimA-MS). There were no significant differences in the abilities of the rFimA-MS to adhere to HGF; however, the adhesion of type II rFimA-MS to HEp-2 cells was significantly greater than those of other types of rFimA-MS. We also observed that type II rFimA-MS invaded epithelial cells and accumulated around the nuclei. These adhesion and invasion characteristics were eliminated by the addition of antibodies to type II rFimA and α5β1-integrin. In contrast, Arg-Gly-Asp-Ser peptide and a synthetic peptide of proline-rich protein C had negligible inhibitory effects. Furthermore,
P. gingivalis
strain HW24D1 with type II
fimA
adhered to cells and invaded them more than strains with other
fimA
genotypes. These results suggest that type II FimA can bind to epithelial cells most efficiently through specific host receptors.
Phase Variation ofCampylobacter jejuni81-176 Lipooligosaccharide Affects Ganglioside Mimicry and Invasiveness In Vitro
Authors: Guerry Patricia , Szymanski Christine M. , Prendergast Martina M. , Hickey Thomas E. , Ewing Cheryl P. , Pattarini Dawn L. , Moran Anthony P. 
Published: July 2002

ABSTRACTThe outer cores of the lipooligosaccharides (LOS) of many strains ofCampylobacter jejunimimic human gangliosides in structure. A population of cells ofC. jejunistrain 81-176 produced a mixture of LOS cores which consisted primarily of structures mimicking GM2and GM3gangliosides, with minor amounts of structures mimicking GD1band GD2. Genetic analyses of genes involved in the biosynthesis of the outer core ofC. jejuni81-176 revealed the presence of a homopolymeric tract of G residues within a gene encoding CgtA, anN-acetylgalactosaminyltransferase. Variation in the number of G residues withincgtAaffected the length of the open reading frame, and these changes incgtAcorresponded to a change in LOS structure from GM2to GM3ganglioside mimicry. Site-specific mutation ofcgtAin 81-176 resulted in a major LOS core structure that lacked GalNAc and resembled GM3ganglioside. Compared to wild-type 81-176, thecgtAmutant showed a significant increase in invasion of INT407 cells. In comparison, a site-specific mutation of theneuC1gene resulted in the loss of sialic acid in the LOS core and reduced resistance to normal human serum but had no affect on invasion of INT407 cells.
Pulmonary Inflammation Induced byPseudomonas aeruginosaLipopolysaccharide, Phospholipase C, and Exotoxin A: Role of Interferon Regulatory Factor 1
Authors: Wieland Catharina W. , Siegmund Britta , Senaldi Giorgio , Vasil Michael L. , Dinarello Charles A. , Fantuzzi Giamila 
Published: July 2002

ABSTRACTChronic pulmonary infection withPseudomonas aeruginosais common in cystic fibrosis (CF) patients.P. aeruginosalipopolysaccharide (LPS), phosholipase C (PLC), and exotoxin A (ETA) were evaluated for their ability to induce pulmonary inflammation in mice following intranasal inoculation. Both LPS and PLC induced high levels of tumor necrosis factor alpha (TNF-α), interleukin 1β (IL-1β), IL-6, gamma interferon (IFN-γ), MIP-1α and MIP-2 in the lungs but did not affect IL-18 levels. ETA did not induce TNF-α and was a weak inducer of IL-1β, IL-6, macrophage inflammatory protein 1α (MIP-1α), and MIP-2. Remarkably, ETA reduced constitutive lung IL-18 levels. LPS was the only factor inducing IFN-γ. LPS, PLC, and ETA all induced cell infiltration in the lungs. The role of interferon regulatory factor-1 (IRF-1) in pulmonary inflammation induced by LPS, PLC, and ETA was evaluated. When inoculated with LPS, IRF-1 gene knockout (IRF-1 KO) mice produced lower levels of TNF-α, IL-1β, and IFN-γ than did wild-type (WT) mice. Similarly, a milder effect of ETA on IL-1β and IL-18 was observed for IRF-1 KO than for WT mice. In contrast, the cytokine response to PLC did not differ between WT and IRF-1 KO mice. Accordingly, LPS and ETA, but not PLC, induced expression of IRF-1 mRNA. IRF-1 deficiency had no effect on MIP-1α and MIP-2 levels and on cell infiltration induced by LPS, PLC, or ETA. Flow cytometric evaluation of lung mononuclear cells revealed strongly reduced percentages of CD8+and NK cells in IRF-1 KO mice compared to percentages observed for WT mice. These data indicate that different virulence factors fromP. aeruginosainduce pulmonary inflammation in vivo and that IRF-1 is involved in some of the cytokine responses to LPS and ETA.
β-Chemokines Are Induced byMycobacterium tuberculosisand Inhibit Its Growth
Authors: Saukkonen Jussi J. , Bazydlo Beth , Thomas Michael , Strieter Robert M. , Keane Joseph , Kornfeld Hardy 
Published: July 2002

ABSTRACTChemokines (CK) are potent leukocyte activators and chemoattractants and aid in granuloma formation, functions critical for the immune response toMycobacterium tuberculosis. We hypothesized that infection of alveolar macrophages (AM) with different strains ofM. tuberculosiselicits distinct profiles of CK, which could be altered by human immunodeficiency virus (HIV) infection. RANTES, macrophage inflammatory protein-1α (MIP-1α), and MIP-1β were the major β-CK produced in response toM. tuberculosisinfection. VirulentM. tuberculosis(H37Rv) induced significantly less MIP-1α than did the avirulent strain (H37Ra), while MIP-1β and RANTES production was comparable for both strains. MIP-1α and MIP-1β were induced by the membrane, but not cytosolic, fraction ofM. tuberculosis.M. tuberculosis-induced CK secretion was partly dependent on tumor necrosis factor alpha (TNF-α). AM from HIV-infected individuals produced less TNF-α and MIP-1β than did normal AM in response to eitherM. tuberculosisstrain. We tested the functional significance of decreased β-CK secretion by examining the ability of β-CK to suppress intracellular growth ofM. tuberculosis. MIP-1β and RANTES suppressed intracellular growth ofM. tuberculosistwo- to threefold, a novel finding. Thus, β-CK contribute to the innate immune response toM. tuberculosisinfection, and their diminution may promote the intracellular survival ofM. tuberculosis.
Proteolysis of CD14 on Human Gingival Fibroblasts by Arginine-Specific Cysteine Proteinases fromPorphyromonas gingivalisLeading to Down-Regulation of Lipopolysaccharide-Induced Interleukin-8 Production
Authors: Tada Hiroyuki , Sugawara Shunji , Nemoto Eiji , Takahashi Nobuhiro , Imamura Takahisa , Potempa Jan , Travis James , Shimauchi Hidetoshi , Takada Haruhiko 
Published: July 2002

ABSTRACTArginine-specific cysteine proteinases (gingipains-R) from periodontopathicPorphyromonas gingivaliscleaved CD14, a bacterial pattern recognition receptor, on human gingival fibroblasts (HGF). Consequently, gingipains-R reduced lipopolysaccharide-induced interleukin-8 production by HGF, indicating that gingipains-R inhibited CD14-dependent HGF activation and are involved in immune evasion by the bacterium in periodontal tissues.
The H
2
Sensor of
Ralstonia eutropha
Is a Member of the Subclass of Regulatory [NiFe] Hydrogenases
Authors: Kleihues Laura , Lenz Oliver , Bernhard Michael , Buhrke Thorsten , Friedrich Bärbel 
Published: July 2002

ABSTRACT

Two energy-generating hydrogenases enable the aerobic hydrogen bacterium
Ralstonia eutropha
(formerly
Alcaligenes eutrophus
) to use molecular hydrogen as the sole energy source. The complex synthesis of the nickel-iron-containing enzymes has to be efficiently regulated in response to H
2
, which is available in low amounts in aerobic environments. H
2
sensing in
R. eutropha
is achieved by a hydrogenase-like protein which controls the hydrogenase gene expression in concert with a two-component regulatory system. In this study we show that the H
2
sensor of
R. eutropha
is a cytoplasmic protein. Although capable of H
2
oxidation with redox dyes as electron acceptors, the protein did not support lithoautotrophic growth in the absence of the energy-generating hydrogenases. A specifically designed overexpression system for
R. eutropha
provided the basis for identifying the H
2
sensor as a nickel-containing regulatory protein. The data support previous results which showed that the sensor has an active site similar to that of prototypic [NiFe] hydrogenases (A. J. Pierik, M. Schmelz, O. Lenz, B. Friedrich, and S. P. J. Albracht, FEBS Lett. 438:231–235, 1998). It is demonstrated that in addition to the enzymatic activity the regulatory function of the H
2
sensor is nickel dependent. The results suggest that H
2
sensing requires an active [NiFe] hydrogenase, leaving the question open whether only H
2
binding or subsequent H
2
oxidation and electron transfer processes are necessary for signaling. The regulatory role of the H
2
-sensing hydrogenase of
R. eutropha
, which has also been investigated in other hydrogen-oxidizing bacteria, is intimately correlated with a set of typical structural features. Thus, the family of H
2
sensors represents a novel subclass of [NiFe] hydrogenases denoted as the “regulatory hydrogenases.”
Contribution of Cysteine Desulfurase (NifS Protein) to the Biotin Synthase Reaction of
Escherichia coli
Authors: Kiyasu Tatsuya , Asakura Akira , Nagahashi Yoshie , Hoshino Tatsuo 
Published: July 2002

ABSTRACT

The contribution of cysteine desulfurase, the NifS protein of
Klebsiella pneumoniae
and the IscS protein of
Escherichia coli
, to the biotin synthase reaction was investigated in in vitro and in vivo reaction systems with
E. coli
. When the
nifS
and
nifU
genes of
K. pneumoniae
were coexpressed in
E. coli
, NifS and NifU proteins in complex (NifU/S complex) and NifU monomer forms were observed. Both the NifU/S complex and the NifU monomer stimulated the biotin synthase reaction in the presence of
l
-cysteine in an in vitro reaction system. The NifU/S complex enhanced the production of biotin from dethiobiotin by the cells growing in an in vivo reaction system. Moreover, the IscS protein of
E. coli
stimulated the biotin synthase reaction in the presence of
l
-cysteine in the cell-free system. These results strongly suggest that cysteine desulfurase participates in the biotin synthase reaction, probably by supplying sulfur to the iron-sulfur cluster of biotin synthase.