bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Tumor Necrosis Factor Alpha on Host Immune Response in Chronic Persistent Tuberculosis: Possible Role for Limiting Pathology
Authors: Mohan Vellore P. , Scanga Charles A. , Yu Keming , Scott Holly M. , Tanaka Kathryn E. , Tsang Enders , Tsai Ming Chih , Flynn JoAnne L. , Chan John 
Published: July 2002

ABSTRACTReactivation of latent tuberculosis contributes significantly to the incidence of disease caused byMycobacterium tuberculosis. The mechanisms involved in the containment of latent tuberculosis are poorly understood. Using the low-dose model of persistent murine tuberculosis in conjunction with MP6-XT22, a monoclonal antibody that functionally neutralizes tumor necrosis factor alpha (TNF-α), we examined the effects of TNF-α on the immunological response of the host in both persistent and reactivated tuberculous infections. The results confirm an essential role for TNF-α in the containment of persistent tuberculosis. TNF-α neutralization resulted in fatal reactivation of persistent tuberculosis characterized by a moderately increased tissue bacillary burden and severe pulmonic histopathological deterioration that was associated with changes indicative of squamous metaplasia and fluid accumulation in the alveolar space. Analysis of pulmonic gene and protein expression of mice in the low-dose model revealed that nitric oxide synthase was attenuated during MP6-XT22-induced reactivation, but was not totally suppressed. Interleukin-12p40 and gamma interferon gene expression in TNF-α-neutralized mice was similar to that in control mice. In contrast, interleukin-10 expression was augmented in the TNF-α-neutralized mice. In summary, results of this study suggest that TNF-α plays an essential role in preventing reactivation of persistent tuberculosis, modulates the pulmonic expression of specific immunologic factors, and limits the pathological response of the host.
Identification of Polymorphic Outer Membrane Proteins ofChlamydia psittaci6BC
Authors: Tanzer Regina J. , Longbottom David , Hatch Thomas P. 
Published: July 2002

ABSTRACTThe genomes ofChlamydiaspp. encode a family of putative outer membrane proteins, referred to as polymorphic outer membrane proteins (POMPs), which may play a role in the avoidance of host immune defenses. We analyzed avian strain 6BC ofChlamydia psittaciby polyacrylamide gel electrophoresis for the expression of POMPs. At least six putative POMPs were identified on the basis of their size (90 to 110 kDa) and labeling with an outer membrane-specific probe, 3-(trifluoromethyl)-3-(m-[125I]iodophenyl)diazirine. Three of the putative POMPs reacted with antiserum raised against a recombinant ovineC. psittacistrain POMP, and two possessed surface-exposed, trypsin-sensitive sites. The POMPs were dependent on disulfide bonds for their maintenance in sodium lauryl sarcosine- and sodium dodecyl sulfate-insoluble complexes but did not appear to be interpeptide disulfide bond cross-linked. The putative POMPs were found to be synthesized during the late phase of the chlamydial developmental cycle, cotemporally with the cysteine-rich doublet periplasmic proteins.
Granulomatous Skin Lesions in Moray Eels Caused by a NovelMycobacteriumSpecies Related toMycobacterium triplex
Authors: Herbst Lawrence H. , Costa Sylvia F. , Weiss Louis M. , Johnson Linda K. , Bartell John , Davis Raymond , Walsh Michael , Levi Michael 
Published: July 2002

ABSTRACTAn outbreak of granulomatous dermatitis was investigated in a captive population of moray eels. The affected eels had florid skin nodules concentrated around the head and trunk. Histopathological examination revealed extensive granulomatous inflammation within the dermis and subcutaneous fascial plane between the fat and axial musculature. Acid-fast rods were detected within the smallest lesions, which were presumably the ones that had developed earliest. Eventually, after several months of incubation at room temperature, a very slowly growing acid-fast organism was isolated. Sequencing of the 16S rRNA gene identified it as aMycobacteriumspecies closely related (0.59% divergence) toM. triplex, an SAV mycobacterium. Intradermal inoculation of healthy green moray eels with this organism reliably reproduced the lesion. Experimentally induced granulomatous dermatitis appeared within 2 weeks of inoculation and slowly but progressively expanded during the 2 months of the experiment. Live organisms were recovered from these lesions at all time points, fulfilling Koch's postulates for this bacterium. In a retrospective study of tissues collected between 1993 and 1999 from five spontaneous disease cases, acid-fast rods were consistently found within lesions, and a nested PCR for the rRNA gene also demonstrated the presence of mycobacteria within affected tissues.
SarT, a Repressor of α-Hemolysin in
Staphylococcus aureus
Authors: Schmidt Katherine A. , Manna Adhar C. , Gill Steven , Cheung Ambrose L. 
Published: July 2002

ABSTRACT

In searching the
Staphylococcus aureus
genome, we found several homologs to SarA. One of these genes,
sarT
, codes for a basic protein with 118 residues and a predicted molecular size of 16,096 Da. Northern blot analysis revealed that the expression of
sarT
was repressed by
sarA
and
agr
. An insertion
sarT
mutant generated in
S. aureus
RN6390 and 8325-4 backgrounds revealed minimal effect on the expression of
sarR
and
sarA
. The RNAIII level was notably increased in the
sarT
mutant, particularly in postexponential-phase cells, while the augmentative effect on RNAII was less. SarT repressed the expression of α-hemolysin, as determined by Northern blotting, Western blotting, and a rabbit erythrocyte hemolytic assay. This repression was relieved upon complementation. Similar to
agr
and
sarA
mutants, which predictably displayed a reduction in
hla
expression, the
agr sarT
mutant exhibited a lower level of
hla
transcription than the
sarT
mutant. In contrast,
hla
transcription was enhanced in the
sarA sarT
mutant compared with the single
sarA
mutant. Collectively, these results indicated that the
sarA
locus, contrary to the regulatory action of
agr
, induced α-hemolysin production by repressing
sarT
, a repressor of
hla
transcription.
Ongoing Horizontal and Vertical Transmission of Virulence Genes and
papA
Alleles among
Escherichia coli
Blood Isolates from Patients with Diverse-Source Bacteremia
Authors: Johnson James R. , O'Bryan Timothy T. , Kuskowski Michael , Maslow Joel N. 
Published: July 2002

ABSTRACT

The phylogenetic distributions of multiple putative virulence factors (VFs) and
papA
(P fimbrial structural subunit) alleles among 182
Escherichia coli
blood isolates from patients with diverse-source bacteremia were defined. Phylogenetic correspondence among these strains, the
E. coli
Reference (ECOR) collection, and other collections of extraintestinal pathogenic
E. coli
(ExPEC) was assessed. Although among the 182 bacteremia isolates phylogenetic group B2 predominated, exhibited the greatest concentration of individual VFs, and contained the largest number of familiar virulent clones, other phylogenetic groups exhibited greater concentrations of certain VFs than did group B2 and included several additional virulent clones. Certain of the newly detected VF genes, e.g.,
fyuA
(yersiniabactin; 76%) and
focG
(F1C fimbriae; 25%), were as prevalent or more prevalent than their more familiar traditional counterparts, e.g.,
iut
(aerobactin; 57%) and
sfaS
(S fimbriae; 14%), thus possibly offering additional useful targets for preventive interventions. Considerable diversity of VF profiles was observed at every level within the phylogenetic tree, including even within individual lineages. This suggested that many different pathways can lead to extraintestinal virulence in
E. coli
and that the evolution of ExPEC, which involves extensive horizontal transmission of VFs and continuous remodeling of pathogenicity-associated islands, is a highly active, ongoing process.
CD8+-T-Cell Immunity againstToxoplasma gondiiCan Be Induced but Not Maintained in Mice Lacking Conventional CD4+T Cells
Authors: Casciotti Lori , Ely Kenneth H. , Williams Martha E. , Khan Imtiaz A. 
Published: July 2002

ABSTRACTT-cell immunity is critical for survival of hosts infected withToxoplasma gondii.Among the cells in the T-cell population, CD8+T cells are considered the major effector cells against this parasite. It is believed that CD4+T cells may be crucial for induction of the CD8+-T-cell response againstT. gondii. In the present study, CD4−/−mice were used to evaluate the role of conventional CD4+T cells in the immune response againstT. gondiiinfection. CD4−/−mice infected withT. gondiiexhibited lower gamma interferon (IFN-γ) messages in the majority of their tissues. As a result, mortality due to a hyperinflammatory response was prevented in these animals. Interestingly,T. gondiiinfection induced a normal antigen-specific CD8+-T-cell immune response in CD4−/−mice. No difference in generation of precursor cytotoxic T lymphocytes (pCTL) or in IFN-γ production by the CD8+-T-cell populations from the knockout and wild-type animals was observed. However, the mutant mice were not able to sustain CD8+-T-cell immunity. At 180 days after infection, the CD8+-T-cell response in the knockout mice was depressed, as determined by pCTL and IFN-γ assays. Loss of CD8+-T-cell immunity at this time was confirmed by adoptive transfer experiments. Purified CD8+T cells from CD4−/−donors that had been immunized 180 days earlier failed to protect the recipient mice against a lethal infection. Our study demonstrated that although CD8+-T-cell immunity can be induced in the absence of conventional CD4+T cells, it cannot be maintained without such cells.
Adherence ofBurkholderia pseudomalleiCells to Cultured Human Epithelial Cell Lines Is Regulated by Growth Temperature
Authors: Brown Nat F. , Boddey Justin A. , Flegg Cameron P. , Beacham Ifor R. 
Published: July 2002

ABSTRACTWe have investigated the adherence ofBurkholderia pseudomallei, cultured under a number of different conditions, to six human epithelial cell lines. While several complex medium compositions had relatively little effect on adherence, growth at 30°C was found to significantly increase adherence to all cell lines relative to that of cultures grown at 37°C (P< 0.001).
Identification of a SecondArcanobacterium pyogenesNeuraminidase and Involvement of Neuraminidase Activity in Host Cell Adhesion
Authors: Jost B. Helen , Songer J. Glenn , Billington Stephen J. 
Published: July 2002

ABSTRACTArcanobacterium pyogenes, a common inhabitant of the upper respiratory and urogenital tracts of economically important animals, such as cattle and swine, is also an opportunistic pathogen associated with suppurative infections in these animals.A. pyogenesexpresses neuraminidase activity encoded by thenanHgene, and previously, construction of ananHmutant ofA. pyogenesBBR1 indicated that a second neuraminidase is present in this strain. A 5,112-bp gene,nanP, was cloned and sequenced, and this gene conferred neuraminidase activity on anEscherichia colihost strain. The predicted 186.8-kDa NanP protein exhibited similarity to a number of bacterial neuraminidases and contained the RIP/RLP motif and five copies of the Asp box motif found in all bacterial neuraminidases. As expected, insertional inactivation of thenanPgene inA. pyogenesBBR1 resulted in a mutant with reduced neuraminidase activity. However, insertional inactivation of thenanPgene in thenanHmutant strain resulted in a complete lack of neuraminidase activity. Like NanH, NanP was localized to theA. pyogenescell wall. However, unlike thenanHgene, which was present in 100% of the strains examined,nanPwas present in only 64.2% of the isolates (n= 53).A. pyogenesadheres to HeLa cells, and ananPmutant displayed a wild-type adhesion phenotype with these cells. In contrast, the ability of ananHnanPdouble mutant to bind to HeLa cells was reduced by 53%. The wild-type adhesion phenotype was restored by providingnanPintrans. These data indicate that the neuraminidases ofA. pyogenesplay a role in adhesion of this organism to host epithelial cells.
Molecular Analysis of the Contribution of the Capsular Polysaccharide and the Lipopolysaccharide O Side Chain to the Virulence of
Klebsiella pneumoniae
in a Murine Model of Pneumonia
Authors: Cortés Guadalupe , Borrell Nuria , de Astorza Beatriz , Gómez Cristina , Sauleda Jaume , Albertí Sebastián 
Published: July 2002

ABSTRACT

Klebsiella pneumoniae
is a common cause of gram-negative bacterial nosocomial pneumonia. Two surface polysaccharides, lipopolysaccharide (LPS) O side chain and capsular polysaccharide (CPS), are critical for the microorganism in causing sepsis, but little is known about their role in pneumonia. To investigate their contribution in the pathogenesis of
K. pneumoniae
pneumonia, we characterized the host response to bacterial challenge with a highly virulent clinical isolate or with isogenic insertion-duplication mutants deficient in CPS or LPS O side chain in a murine model of pneumonia. Animals challenged intratracheally with the wild-type or LPS O side chain-deficient strain developed pneumonia and became bacteremic before death. Extensive lung lesions as well as pleuritis, vasculitis, and edema were observed by histopathological examination, and polymorphonuclear infiltration was also demonstrated. In contrast, none of the animals challenged with the unencapsulated strain developed pneumonia or bacteremia. Examination of tissue from this group did not identify lung lesions, and none of the infected animals died. Analysis of the early host defense mechanisms that contributed to the clearance of the unencapsulated mutant showed that the levels of C3 deposited on the unencapsulated mutant surface were threefold higher than those for the wild-type and LPS O side chain-deficient strains. Furthermore, phagocytosis of the unencapsulated mutant by human alveolar macrophages (AM) was more efficient than that of the wild-type and LPS O side chain-deficient strains. We conclude that CPS, but not LPS O side chain, is essential for
Klebsiella
pneumonia because it modulates the deposition of C3 and protects the microorganisms against human AM phagocytosis.
Mycobacterium tuberculosis
Genes Induced during Infection of Human Macrophages
Authors: Dubnau Eugenie , Fontán Patricia , Manganelli Riccardo , Soares-Appel Sonia , Smith Issar 
Published: July 2002

ABSTRACT

We identified
Mycobacterium tuberculosis
genes preferentially expressed during infection of human macrophages using a promoter trap adapted for this pathogen.
inhA
encodes an enoyl-acyl carrier protein reductase that is required for mycolic acid biosynthesis (A. Quemard et al., Biochemistry
34:
8235-8241, 1995) and is a major target for isoniazid (INH) in mycobacterial species (A. Banerjee et al., Science
263:
227-230, 1994). Since overexpression of
inhA
confers INH resistance in
Mycobacterium smegmatis
(Banerjee et al., Science
263:
227-230, 1994), we designed a promoter trap based on this gene. A library of clones, containing small fragments of
M. tuberculosis
DNA cloned upstream of
inhA
in a plasmid vector, was electroporated into
M. tuberculosis
, and the resulting culture was used to infect the human monocytic THP-1 cell line. Selection was made for clones surviving INH treatment during infection but retaining INH sensitivity on plates. The DNA upstream of
inhA
was sequenced in each clone to identify the promoter driving
inhA
expression. Thirteen genes identified by this method were analyzed by quantitative reverse transcription-PCR (R. Manganelli et al., Mol. Microbiol.
31:
715-724, 1999), and eight of them were found to be differentially expressed from cultures grown in macrophages compared with broth-grown cultures. Several of these genes are presumed to be involved in fatty acid metabolism; one potentially codes for a unique DNA binding protein, one codes for a possible potassium channel protein, and the others code for proteins of unknown function. Genes which are induced during infection are likely to be significant for survival and growth of the pathogen; our results lend support to the view that fatty acid metabolism is essential for the virulence of
M. tuberculosis.
The
lbgAB
Gene Cluster of
Haemophilus ducreyi
Encodes a β-1,4-Galactosyltransferase and an α-1,6-
dd
-Heptosyltransferase Involved in Lipooligosaccharide Biosynthesis
Authors: Tullius Michael V. , Phillips Nancy J. , Scheffler N. Karoline , Samuels Nicole M. , Munson Robert S. , Hansen Eric J. , Stevens-Riley Marla , Campagnari Anthony A. , Gibson Bradford W. 
Published: July 2002

ABSTRACT

All
Haemophilus ducreyi
strains examined contain a lipooligosaccharide (LOS) consisting of a single but variable branch oligosaccharide that emanates off the first heptose (Hep-I) of a conserved Hep
3
-phosphorylated 3-deoxy-
d
-manno-octulosonic acid-lipid A core. In a previous report, identification of tandem genes,
lbgA
and
lbgB
, that are involved in LOS biosynthesis was described (Stevens et al., Infect. Immun. 65:651-660, 1997). In a separate study, the same gene cluster was identified and the
lbgB
(
losB
) gene was found to be required for transfer of the second sugar,
d
-
glycero
-
d
-
manno
-heptose (
dd
-Hep), of the major branch structure (Gibson et al., J. Bacteriol. 179:5062-5071, 1997). In this study, we identified the function of the neighboring upstream gene,
lbgA
, and found that it is necessary for addition of the third sugar in the dominant oligosaccharide branch, a galactose-linked β1→4, to the
dd
-Hep. LOS from an
lbgA
mutant and an
lbgAB
double mutant were isolated and were characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, carbohydrate analysis, mass spectrometry, and nuclear magnetic resonance spectroscopy. The results showed that the mutant strains synthesize truncated LOS glycoforms that terminate after addition of the first glucose (
lbgAB
) or the disaccharide
dd
-Hepα1→6Glcβ1 (
lbgA
) that is attached to the heptose core. Both mutants show a significant reduction in the ability to adhere to human keratinocytes. Although minor differences were observed after two-dimensional gel electrophoresis of total proteins from the wild-type and mutant strains, the expression levels of the vast majority of proteins were unchanged, suggesting that the differences in adherence and invasion are due to differences in LOS. These studies add to the mounting evidence for a role of full-length LOS structures in the pathophysiology of
H. ducreyi
infection.
LsaA, an Antigen Involved in Cell Attachment and Invasion, Is Expressed byLawsonia intracellularisduring Infection In Vitro and In Vivo
Authors: McCluskey Jackie , Hannigan Joanne , Harris Jennifer D. , Wren Brendan , Smith David G. E. 
Published: July 2002

ABSTRACTLawsonia intracellularishas been identified recently as the etiological agent of proliferative enteropathies, which are characterized by intestinal epithelial hyperplasia and associated moderate immune responses. This disease complex has been reported in a broad range of animals, prevalently in pigs, andL. intracellularishas been linked with ulcerative colitis in humans.L. intracellularisis an obligate intracellular bacterium, and the pathogenic mechanisms used to cause disease are unknown. Using in vitro-grown organisms as a source of genomic DNA, we identified aLawsoniagene which encodes a surface antigen, LsaA (forLawsoniasurface antigen), associated with attachment to and entry into cells. The deduced amino acid sequence of this protein showed some similarity to members of a novel protein family identified in a number of other bacterial pathogens but for which roles are not fully defined. Transcription of this gene was detected by reverse transcription-PCR inL. intracellularisgrown in vitro in IEC18 cells and in bacteria present in ileal tissue from infected animals. Immunohistochemistry with specific monoclonal antibody and immunoblotting with sera from infected animals demonstrated that LsaA protein is synthesized byL. intracellularisduring infection. Expression of this gene during infection in vitro and in vivo suggests that this surface antigen is involved during infection, and phenotypic analysis indicated a role duringL. intracellularisattachment to and entry into intestinal epithelial cells
Construction and Phenotypic Characterization of an Auxotrophic Mutant of
Mycobacterium tuberculosis
Defective in
l
-Arginine Biosynthesis
Authors: Gordhan Bhavna G. , Smith Debbie A. , Alderton Heidi , McAdam Ruth A. , Bancroft Gregory J. , Mizrahi Valerie 
Published: July 2002

ABSTRACT

A mutant of
Mycobacterium tuberculosis
defective in the metabolism of
l
-arginine was constructed by allelic exchange mutagenesis. The
argF
mutant strain required exogenous
l
-arginine for growth in vitro, and in the presence of 0.96 mM
l
-arginine, it achieved a growth rate and cell density in stationary phase comparable to those of the wild type. The mutant strain was also able to grow in the presence of high concentrations of argininosuccinate, but its auxotrophic phenotype could not be rescued by
l
-citrulline, suggesting that the Δ
argF
::
hyg
mutation exerted a polar effect on the downstream
argG
gene but not on
argH
. The mutant strain displayed reduced virulence in immunodeficient SCID mice and was highly attenuated in immunocompetent DBA/2 mice, suggesting that
l
-arginine availability is restricted in vivo.
Uptake ofAspergillus fumigatusConidia by Phagocytic and Nonphagocytic Cells In Vitro: Quantitation Using Strains Expressing Green Fluorescent Protein
Authors: Wasylnka Julie A. , Moore Margo M. 
Published: July 2002

ABSTRACTSeveral pathogenic fungal organisms enter eukaryotic cells and manipulate the host cell environment to favor their own growth and survival.Aspergillus fumigatusis a saprophytic fungus that causes invasive lung disease in the immunocompromised host. To determine whetherA. fumigatuscould enter eukaryotic cells, we studied the uptake of two different GFP-expressingA. fumigatusstrains into A549 lung epithelial cells, human umbilical vein endothelial (HUVE) cells, and J774 murine macrophages in vitro. A549 cells internalized 30% of the bound conidia whereas HUVE and J774 cells internalized 50 and 90%, respectively. Conidia within A549 cells remained viable for 6 h; however, 60 to 80% of conidia within J774 cells were killed after only 4 h. Live and heat-killed conidia were internalized to the same extent by A549 cells. After 6 h, almost none of the conidia inside A549 cells had germinated, whereas extracellular conidia had developed germ tubes. Internalization of conidia by A549 cells was a temperature-dependent process and required rearrangement of the underlying host cell cytoskeleton; uptake was inhibited by 75% with 0.5 μM cytochalasin D and by 65% with 5 μM colchicine. Fluorescent labeling of infected A549 cells with rhodamine phalloidin provided visible evidence of cytoskeletal alteration as many of the intracellular conidia were contained in actin-coated phagosomes. These data provide evidence that significant numbers ofA. fumigatusconidia can be internalized by nonprofessional phagocytes in vitro and these cells may serve as reservoirs for immune cell evasion and dissemination throughout the host.
Activation of the
Pseudomonas aeruginosa
Type III Secretion System Requires an Intact Pyruvate Dehydrogenase
aceAB
Operon
Authors: Dacheux Denis , Epaulard Olivier , de Groot Arjan , Guery Benoit , Leberre Rozen , Attree Ina , Polack Benoit , Toussaint Bertrand 
Published: July 2002

ABSTRACT

Pseudomonas aeruginosa
clinical cystic fibrosis isolate CHA was mutagenized with Tn
5
Tc to identify new genes involved in type III secretion system (TTSS)-dependent cytotoxicity toward human polymorphonuclear neutrophils. Among 25 mutants affected in TTSS function, 14 contained the insertion at different positions in the
aceAB
operon encoding the PDH-E1 and -E2 subunits of pyruvate dehydrogenase. In PDH mutants, no transcriptional activation of TTSS genes in response to calcium depletion occurred. Expression in
trans
of ExsA restored TTSS function and cytotoxicity.