bluuebunny/crossref_metadata_2025_split huggingface dataset:
Beneficial or Deleterious Effects of a Preexisting Hypersensitivity to Bacterial Components on the Course and Outcome of Infection
Authors: Gumenscheimer Marina , Mitov Ivan , Galanos Chris , Freudenberg Marina A. 
Published: September 2002

ABSTRACTPriming with heat-killedPropionibacterium acnesenhances the sensitivity of mice to lipopolysaccharide (LPS) and other biologically active bacterial components. We show thatP. acnespriming has protective and deleterious effects on a subsequent serovar Typhimurium infection. It may result in a complete protection or prolonged survival, or it may accelerate mortality of the infected mice, depending on the number of serovar Typhimurium bacteria administered and on the degree of LPS hypersensitivity at the time of infection. Both effects ofP. acnes-induced hypersensitivity are mediated by gamma interferon (IFN-γ) and are based on a differential activation of the innate immune mechanisms which recognize and react against the LPS present in infecting bacteria. InP. acnes-primed mice null for LPS-binding protein (LBP−/−mice), the impaired LPS recognition, due to the absence of LBP, resulted in a higher resistance to serovar Typhimurium infection. A similarP. acnespriming of mice had a protective, but no deleterious effect on a subsequentL. monocytogenesinfection. This effect was IFN-γ dependent but independent of LBP.
The Human Complement Regulator Factor H Binds Pneumococcal Surface Protein PspC via Short Consensus Repeats 13 to 15
Authors: Duthy Thomas G. , Ormsby Rebecca J. , Giannakis Eleni , Ogunniyi A. David , Stroeher Uwe H. , Paton James C. , Gordon David L. 
Published: September 2002

ABSTRACTThe innate ability ofStreptococcus pneumoniaeto resist complement activation and complement-mediated phagocytosis may be a direct consequence of the ability of the bacteria to bind components of the complement regulatory system. One such component, factor H (fH), is a crucial fluid-phase negative regulator of the alternative pathway of complement and is utilized by a number of pathogenic organisms to resist complement attack. The pneumococcal surface protein C (PspC [also known as CbpA] and SpsA) has been shown to bind fH, although the exact binding site within one or more of the 20 short consensus repeats (SCRs) of the molecule is not known. The purpose of the current study was to map specific SCRs on fH responsible for this binding. Initial experiments utilizing type 2 pneumococcal strain D39 and its isogenic PspC-negative derivative (D39/pspCmutant) showed that fH binding was PspC dependent. A purified recombinant protein derivative of PspC that lacked the proline-rich region (PspCΔPro) had a reduced binding efficiency for fH, thereby directly showing the importance of this region for the fH interaction. We have specifically shown by inhibition experiments that SCRs responsible for heparin and C3b binding of fH are not involved in binding PspC and the interaction between fH and PspC is largely hydrophobic, since no inhibition was observed in the presence of high concentrations of NaCl. Construction of SCR proteins encompassing the whole fH molecule showed that SCRs 8 to 15 (SCR 8-15) mediated binding to PspC. Further localization experiments revealed that SCR 13 and SCR 15 were required for full binding, although partial binding was retained when either SCR was removed.
Characterization of P40, a Cytadhesin of
Mycoplasma agalactiae
Authors: Fleury Bénédicte , Bergonier Dominique , Berthelot Xavier , Peterhans Ernst , Frey Joachim , Vilei Edy M. 
Published: September 2002

ABSTRACT

An immunodominant protein, P40, of
Mycoplasma agalactiae
was analyzed genetically and functionally. The gene encoding P40 was cloned from type strain PG2, sequenced, submitted to point mutagenesis in order to convert mycoplasma-specific TGA
Trp
codon to the universal TGG
Trp
codon, and subsequently expressed in
Escherichia coli
. Nucleotide sequence-derived amino acid sequence comparisons revealed a similarity of P40 to the adhesin P50 of
Mycoplasma hominis
and to protein P89 of
Spiroplasma citri
, which is expected to be involved in adhesion. The amino acid sequence of P40 revealed a recognition site for a signal peptidase and strong antigenic and hydrophilic motifs in the C-terminal domain. Triton X-114 phase partitioning confirmed that P40 is a membrane protein. Fab fragments of antibodies directed against recombinant purified P40 significantly inhibited adherence of
M. agalactiae
strains PG2 to lamb joint synovial cells LSM 192. Sera taken sequentially from sheep infected with PG2 revealed that P40 induced a strong and persistent immune response that gave strong signals on immunoblots containing recombinant P40 even 3 months after infection. The gene encoding P40 was present in a single copy in all of the 26 field strains of
M. agalactiae
analyzed and was not detected in closely related mycoplasma species. P40 was expressed as a protein with an apparent molecular mass of 37 kDa on sodium dodecyl sulfate-acrylamide gels by all
M. agalactiae
strains except for serotype C strains, which showed nonsense mutations in their
p40
genes.
Oral Immunization with aSalmonella entericaSerovar Typhi Vaccine Induces Specific Circulating Mucosa-Homing CD4+and CD8+T Cells in Humans
Authors: Lundin B. Samuel , Johansson Camilla , Svennerholm Ann-Mari 
Published: September 2002

ABSTRACTThe kinetics and homing characteristics of T-cell responses in humans after mucosal immunizations have not been well characterized. Therefore, we have investigated the magnitude and duration of such responses as well as the homing receptor expression of antigen-specific peripheral blood T cells by using an oral model vaccine, i.e., the live, attenuatedSalmonella entericaserovar Typhi vaccine (Ty21a). Eight volunteers were each given three doses of the vaccine 2 days apart, and blood samples, from which CD4+and CD8+T cells were selected by the use of magnetic beads, were collected before vaccination and at regular intervals thereafter. To purify the potentially antigen-specific gut-homing T cells, CD45RA−integrin β7+cells were further sorted by flow cytometry. The sorted cells were then stimulated in vitro with the serovar Typhi vaccine strain, and the proliferation of cells and the cytokine production were measured. Following vaccination, there was a large increase in both the proliferation of and the gamma interferon (IFN-γ) production by blood T cells stimulated with the vaccine strain. The responses were seen among both CD4+and CD8+T cells, although the CD8+cells produced the largest amounts of IFN-γ. Peak responses were seen 7 to 14 days after the onset of vaccination. Furthermore, most of the IFN-γ produced by both CD4+and CD8+cells emanated from cells with the potential to home to mucosal tissues, as the integrin β7-expressing memory T cells produced around 10-fold more IFN-γ than the remaining populations. In conclusion, we demonstrate that oral vaccination with a live oral bacterial vaccine induces antigen-specific CD4+and CD8+memory T cells, almost all of which express the gut-homing integrin β7.
VirulentMycobacterium fortuitumRestricts NO Production by a Gamma Interferon-Activated J774 Cell Line and Phagosome-Lysosome Fusion
Authors: da Silva Tânia Regina Marques , de Freitas Juliana Ribeiro , Silva Queilan Chagas , Figueira Cláudio Pereira , Roxo Eliana , Leão Sylvia Cardoso , de Freitas Luiz Antônio Rodrigues , Veras Patrícia Sampaio Tavares 
Published: September 2002

ABSTRACTThe virulence of different isolates ofMycobacteriumhas been associated with two morphologically distinguishable colonial variants: opaque (SmOp) and transparent (SmTr). In this report we used an in vitro assay to compare macrophage (Mφ) responses to SmOp and SmTrMycobacterium fortuitumvariants, taking advantage of the fact that these variants were derived from the same isolate. Cells preactivated or not with gamma interferon (IFN-γ) were infected with SmOp or SmTrM. fortuitum. We showed that SmOp and SmTr induced different levels of nitric oxide (NO) production by IFN-γ-stimulated Mφ. Indeed, the amount of IFN-γ-induced NO production by J774 cells was 4.8 to 9.0 times higher by SmOp (23.1 to 37.7 μM) compared to SmTr infection (3.9 to 4.8 μM) (P= 0.0332), indicating that virulent SmTr bacilli restricted NO production. In addition, IFN-γ-induced NO production by Mφ was higher when correlated with reduction of only avirulent SmOp bacillus viability. SNAP (S-nitroso-N-acetyl-dl-penicillamine)-induced NO production did not modify SmTr viability, indicating its resistance to nitrogen radicals. Electron microscopy studies were performed to evaluate the capacity of phagosomes to fuse with lysosomes labeled with bovine serum albumin-colloidal gold particles. By 24 h postinfection, 69% more phagosome-containing SmOp variant had fused with lysosomes compared to the SmTr-induced phagosomes. In conclusion, these data indicate that virulent SmTr bacilli may escape host defense by restricting IFN-γ-induced NO production, resisting nitrogen toxic radicals, and limiting phagosome fusion with lysosomes.
N-Acylhomoserine Lactones Undergo Lactonolysis in a pH-, Temperature-, and Acyl Chain Length-Dependent Manner during Growth ofYersinia pseudotuberculosisandPseudomonas aeruginosa
Authors: Yates Edwin A. , Philipp Bodo , Buckley Catherine , Atkinson Steve , Chhabra Siri Ram , Sockett R. Elizabeth , Goldner Morris , Dessaux Yves , Cámara Miguel , Smith Harry , Williams Paul 
Published: September 2002

ABSTRACTIn gram-negative bacterial pathogens, such asPseudomonas aeruginosaandYersinia pseudotuberculosis, cell-to-cell communication via theN-acylhomoserine lactone (AHL) signal molecules is involved in the cell population density-dependent control of genes associated with virulence. This phenomenon, termed quorum sensing, relies upon the accumulation of AHLs to a threshold concentration at which target structural genes are activated. By using biosensors capable of detecting a range of AHLs we observed that, in cultures ofY. pseudotuberculosisandP. aeruginosa, AHLs accumulate during the exponential phase but largely disappear during the stationary phase. When added to late-stationary-phase, cell-free culture supernatants of the respective pathogen, the majorP. aeruginosa[N-butanoylhomoserine lactone (C4-HSL) andN-(3-oxododecanoyl)homoserine lactone (3-oxo-C12-HSL)] andY. pseudotuberculosis[N-(3-oxohexanoyl)homoserine lactone (3-oxo-C6-HSL) andN-hexanoylhomoserine lactone (C6-HSL)] AHLs were inactivated. Short-acyl-chain compounds (e.g., C4-HSL) were turned over more extensively than long-chain molecules (e.g., 3-oxo-C12-HSL). Little AHL inactivation occurred with cell extracts, and no evidence for inactivation by specific enzymes was apparent. This AHL turnover was discovered to be due to pH-dependent lactonolysis. By acidifying the growth media to pH 2.0, lactonolysis could be reversed. By using carbon-13 nuclear magnetic resonance spectroscopy, we found that the ring opening of homoserine lactone (HSL),N-propionyl HSL (C3-HSL), and C4-HSL increased as pH increased but diminished as theN-acyl chain was lengthened. At low pH levels, the lactone rings closed but not via a simple reversal of the ring opening reaction mechanism. Ring opening of C4-HSL, C6-HSL, 3-oxo-C6-HSL, andN-octanoylhomoserine lactone (C8-HSL), as determined by the reduction of pH in aqueous solutions with time, was also less rapid for AHLs with more electron-donating longer side chains. Raising the temperature from 22 to 37°C increased the rate of ring opening. Taken together, these data show that (i) to be functional under physiological conditions in mammalian tissue fluids, AHLs require anN-acyl side chain of at least four carbons in length and (ii) that the longer the acyl side chain the more stable the AHL signal molecule.
Virulence Effect of
Enterococcus faecalis
Protease Genes and the Quorum-Sensing Locus
fsr
in
Caenorhabditis elegans
and Mice
Authors: Sifri Costi D. , Mylonakis Eleftherios , Singh Kavindra V. , Qin Xiang , Garsin Danielle A. , Murray Barbara E. , Ausubel Frederick M. , Calderwood Stephen B. 
Published: September 2002

ABSTRACT

The expression of two
Enterococcus faecalis
extracellular virulence-related proteins, gelatinase (GelE) and serine protease (SprE), has been shown to be positively regulated by the
fsr
quorum-sensing system. We recently developed a novel system for studying
E. faecalis
pathogenicity that involves killing of the nematode worm
Caenorhabditis elegans
and showed that an
E. faecalis fsrB
mutant (strain TX5266) exhibited attenuated killing. We explore here the role of the
fsr
/
gelE
-
sprE
locus in pathogenicity by comparing results obtained in the nematode system with a mouse peritonitis model of
E. faecalis
infection. Insertion mutants of
fsrA
(TX5240) and
fsrC
(TX5242), like
fsrB
(TX5266), were attenuated in their ability to kill
C. elegans
. A deletion mutant of
gelE
(TX5264) and an insertion mutant of
sprE
(TX5243) were also attenuated in
C. elegans
killing, although to a lesser extent than the
fsr
mutants. Complementation of
fsrB
(TX5266) with a 6-kb fragment containing the entire
fsr
locus restored virulence in both the nematode and the mouse peritonitis models. The
fsr
mutants were not impaired in their ability to colonize the nematode intestine. These data show that extracellular proteases and the quorum-sensing
fsr
system are important for
E. faecalis
virulence in two highly divergent hosts: nematodes and mice.
Interleukin-4 Receptor α Chain and STAT6 Signaling Inhibit Gamma Interferon but Not Th2 Cytokine Expression within Schistosome Granulomas
Authors: Metwali Ahmed , Blum Arthur , Elliott David E. , Weinstock Joel V. 
Published: September 2002

ABSTRACTCompared to wild-type (WT) mice, schistosome granulomas in Stat6 knockout (KO) mice lacked eosinophils and had Th1 features. Interleukin-4 (IL-4) acts through Stat6 in assisting Th2 cell development. The importance of Stat6 for Th2-cell development within schistosome granulomas had not been explored. Therefore we studied gamma interferon (IFN-γ), IL-4, and IL-5 production in granulomas from Stat6 KO and WT mice. Dispersed granuloma cells from Stat6 KO and WT mice made similar amounts of IL-4 and IL-5. Only Stat6 KO granuloma cells released IFN-γ. Granuloma T cells contained most of the IL-4, IL-5, and IFN-γ mRNA and secreted these cytokines. In Stat6 KO mice, 16.6% of the granuloma cells were CD4+. Of these, 10.7% stained for IFN-γ and/or IL-4 by intracytoplasmic flow analysis. Few CD4−T cells stained positively. The IL-4-producing T cells did not stain for DX5 or with labeled α-GalCer CD1d tetramer, suggesting an absence of NK T cells. Thus, conventional Th cells in Stat6 KO granulomas produce IFN-γ and Th2 cytokines. Stat6 limits IFN-γ production but is unnecessary for Th2-cell development or localization within the granuloma.
Legionella pneumophila feoABPromotes Ferrous Iron Uptake and Intracellular Infection
Authors: Robey Marianne , Cianciotto Nicholas P. 
Published: September 2002

ABSTRACTIn order to determine the role of ferrous iron transport inLegionellapathogenesis, we identified and mutated thefeoBgene in virulentLegionella pneumophilastrain 130b. As it is inEscherichia coli, theL. pneumophila feoBgene was contained within a putativefeoABoperon.L. pneumophila feoBinsertion mutants exhibited decreased ferrous but not ferric iron uptake compared to the wild type. Growth on standard buffered charcoal yeast extract agar or buffered yeast extract broth was unaffected by the loss ofL. pneumophilaFeoB. However, theL. pneumophila feoBmutant had a reduced ability to grow on buffered charcoal yeast extract agar with a reduced amount of its usual iron supplementation, a phenotype that could be complemented by the addition offeoBintrans. In unsupplemented buffered yeast extract broth, thefeoBmutant also had a growth defect, which was further exacerbated by the addition of the ferrous iron chelator, 2,2′-dipyridyl. ThefeoBmutant was also 2.5 logs more resistant to streptonigrin than wild-type 130b, confirming its decreased ability to acquire iron during extracellular growth. Decreased replication of thefeoBmutant was noted within iron-depletedHartmannella vermiformisamoebae and human U937 cell macrophages. The reduced intracellular infectivity of thefeoBmutant was complemented by the introduction of a plasmid containingfeoAB. TheL. pneumophila feoBgene conferred a modest growth advantage for the wild type over the mutant in a competition assay within the lungs of A/J mice. Taken together, these results indicate thatL. pneumophilaFeoB is a ferrous iron transporter that is important for extracellular and intracellular growth, especially in iron-limited environments. These data represent the first evidence for the importance of ferrous iron transport for intracellular replication by a human pathogen.
Genetic Analysis of a
Cryptosporidium parvum
Human Genotype 1 Isolate Passaged through Different Host Species
Authors: Akiyoshi D. E. , Feng X. , Buckholt M. A. , Widmer G. , Tzipori S. 
Published: September 2002

ABSTRACT

Cryptosporidium parvum
TU502, a genotype 1 isolate of human origin, was passaged through three different mammalian hosts, including humans, pigs, and calves. It was confirmed to be genotype 1 by PCR-restriction fragment length polymorphism analysis of the
Cryptosporidium
oocyst wall protein gene, direct sequencing of PCR fragments of the small subunit rRNA and β-tubulin genes, and microsatellite analysis. This isolate was shown to be genetically stable when passaged through the three mammalian species, with no evidence of the emergence of new subpopulations as observed by a genotype-specific PCR assay. TU502 oocysts from different sources failed to infect gamma interferon knockout mice, a characteristic of genotype 1 isolates. The genotypic and phenotypic characterization of TU502 is significant since it is the isolate selected to sequence the genome of
C. parvum
genotype 1 and is currently used in several research projects including human volunteer studies.
Secreted Metalloprotease Gene Family of
Microsporum canis
Authors: Brouta Frédéric , Descamps Frédéric , Monod Michel , Vermout Sandy , Losson Bertrand , Mignon Bernard 
Published: September 2002

ABSTRACT

Keratinolytic proteases secreted by dermatophytes are likely to be virulence-related factors.
Microsporum canis
, the main agent of dermatophytosis in dogs and cats, causes a zoonosis that is frequently reported. Using
Aspergillus fumigatus
metalloprotease genomic sequence (
MEP
) as a probe, three genes (
MEP1
,
MEP2
, and
MEP3
) were isolated from an
M. canis
genomic library. They presented a quite-high percentage of identity with both
A. fumigatus MEP
and
Aspergillus oryzae
neutral protease I genes. At the amino acid level, they all contained an HEXXH consensus sequence, confirming that these
M. canis
genes (
MEP
genes) encode a zinc-containing metalloprotease gene family. Furthermore,
MEP3
was found to be the gene encoding a previously isolated
M. canis
43.5-kDa keratinolytic metalloprotease, and was successfully expressed as an active recombinant enzyme in
Pichia pastoris
. Reverse transcriptase nested PCR performed on total RNA extracted from the hair of
M. canis
-infected guinea pigs showed that at least MEP2 and MEP3 are produced during the infection process. This is the first report describing the isolation of a gene family encoding potential virulence-related factors in dermatophytes.
Relationship of the Glyoxylate Pathway to the Pathogenesis of
Cryptococcus neoformans
Authors: Rude Thomas H. , Toffaletti Dena L. , Cox Gary M. , Perfect John R. 
Published: September 2002

ABSTRACT

Functional genomics has become a major focus in the study of microbial pathogenesis. This study used a functional genomic tool, differential display reverse transcription-PCR, to identify a transcriptional profile of
Cryptococcus neoformans
cells as they produced meningitis in an immunosuppressed host. This serial global gene expression during infection allowed for the identification of up- and down-regulated genes during infection. During this profiling, a single gene for the enzyme isocitrate lyase (ICL1) was found to be up regulated at 1 week of infection in a rabbit meningitis model and during a time of maximum host cellular response. The finding suggested that this enzyme and the glyoxylate shunt pathway are important to this yeast's energy production during infection. However, site-directed
icl1
mutants had no apparent virulence defect in two animal models and no growth defect within macrophages. These observations suggest that although the yeast responded to a certain environmental cue(s) by an increase in ICL1 expression during infection, this gene was not necessary for progression of a
C. neoformans
infection. Compounds that specifically target only ICL1 are unlikely to cripple
C. neoformans
growth in vivo.
Modulation of an Interleukin-12 and Gamma Interferon Synergistic Feedback Regulatory Cycle of T-Cell and Monocyte Cocultures byPorphyromonas gingivalisLipopolysaccharide in the Absence or Presence of Cysteine Proteinases
Authors: Yun Peter L. W. , DeCarlo Arthur A. , Collyer Charles , Hunter Neil 
Published: September 2002

ABSTRACTInterleukin 12 (IL-12) is an efficient inducer and enhancer of gamma interferon (IFN-γ) production by both resting and activated T cells. There is evidence that human monocytes exposed to IFN-γ have enhanced ability to produce IL-12 when stimulated with lipopolysaccharide (LPS). In this study, it was demonstrated that LPS from the oral periodontal pathogenPorphyromonas gingivalisstimulated monocytes primed with IFN-γ to release IL-12, thereby enhancing IFN-γ accumulation in T-cell populations. P. gingivalisLPS was shown to enhance IL-12 induction of IFN-γ in T cells in a manner independent from TNF-α contribution. The levels of T-cell IL-12 receptors were not affected byP. gingivalisLPS and played only a minor role in the magnitude of the IFN-γ response. These data suggest that LPS fromP. gingivalisestablishes an activation loop with IL-12 and IFN-γ with potential to augment the production of inflammatory cytokines in relation to the immunopathology of periodontitis. We previously reported that the major cysteine proteinases (gingipains) copurifying with LPS in this organism were responsible for reduced IFN-γ accumulation in the presence of IL-12. However, the addition of the gingipains in the presence of LPS resulted in partial restoration of the IFN-γ levels. In the destructive periodontitis lesion, release of gingipains from the outer membrane (OM) ofP. gingivaliscould lead to the downregulation of Th1 responses, while gingipain associated with LPS in the OM or in OM vesicles released from the organism could have net stimulatory effects.