bluuebunny/crossref_metadata_2025_split huggingface dataset:
Protection against Bacterial Superantigen Staphylococcal Enterotoxin B by Passive Vaccination
Authors: LeClaire Ross D. , Hunt Robert E. , Bavari Sina 
Published: July 2002

ABSTRACTWe investigated the ability of two overlapping fragments of staphylococcal enterotoxin B (SEB), which encompass the whole toxin, to induce protection and also examined if passive transfer of chicken anti-SEB antibodies raised against the holotoxin could protect rhesus monkeys against aerosolized SEB. Although both fragments of SEB were highly immunogenic, the fragments failed to protect mice whether they were injected separately or injected together. Passive transfer of antibody generated in chickens (immunoglobulin Y [IgY]) against the whole toxin suppressed cytokine responses and was protective in mice. All rhesus monkeys treated with the IgY specific for SEB up to 4 h after challenge survived lethal SEB aerosol exposure. These findings suggest that large fragments of SEB may not be ideal for productive vaccination, but passive transfer of SEB-specific antibodies protects nonhuman primates against lethal aerosol challenge. Thus, antibodies raised in chickens against the holotoxin may have potential therapeutic value within a therapeutic window of opportunity after SEB encounter.
Mycoplasma hyopneumoniaeIncreases Intracellular Calcium Release in Porcine Ciliated Tracheal Cells
Authors: Park Seung-Chun , Yibchok-Anun Sirintorn , Cheng Henrique , Young Theresa F. , Thacker Eileen L. , Minion F. Chris , Ross Richard F. , Hsu Walter H. 
Published: July 2002

ABSTRACTWe investigated the effects of intact pathogenicMycoplasma hyopneumoniae, nonpathogenicM. hyopneumoniae, andMycoplasma flocculareon intracellular free Ca2+concentrations ([Ca2+]i) in porcine ciliated tracheal epithelial cells. The ciliated epithelial cells had basal [Ca2+]iof 103 ± 3 nM (n= 217 cells). The [Ca2+]iincreased by 250 ± 19 nM (n= 47 cells) from the basal level within 100 s of the addition of pathogenicM. hyopneumoniaestrain 91-3 (300 μg/ml), and this increase lasted ∼60 s. In contrast, nonpathogenicM. hyopneumoniaeandM. flocculareat concentrations of 300 μg/ml failed to increase [Ca2+]i. In Ca2+-free medium, pathogenicM. hyopneumoniaestill increased [Ca2+]iin tracheal cells. Pretreatment with thapsigargin (1 μM for 30 min), which depleted the Ca2+store in the endoplasmic reticulum, abolished the effect ofM. hyoneumoniae. Pretreatment with pertussis toxin (100 ng/ml for 3 h) or U-73122 (2 μM for 100 s), an inhibitor of phospholipase C, also abolished the effect ofM. hyopneumoniae. The administration of mastoparan 7, an activator of pertussis toxin-sensitive proteins Giand Go, increased [Ca2+]iin ciliated tracheal cells. These results suggest that pathogenicM. hyopneumoniaeactivates receptors that are coupled to Gior Go, which in turn activates a phospholipase C pathway, thereby releasing Ca2+from the endoplasmic reticulum. Thus, an increase in Ca2+may serve as a signal for the pathogenesis ofM. hyopneumoniae.
Differential Regulation of the Mitogen-Activated Protein Kinases by Pathogenic and Nonpathogenic Mycobacteria
Authors: Roach Shannon K. , Schorey Jeffrey S. 
Published: July 2002

ABSTRACTMycobacteria are the etiologic agents of numerous diseases which account for significant morbidity and mortality in humans and other animal species. Many mycobacteria are intramacrophage pathogens and therefore the macrophage response to infection, which includes synthesis of cytokines such as tumor necrosis factor alpha (TNF-α) and production of nitric oxide, has important consequences for host immunity. However, very little is known about the macrophage cell signaling pathways initiated upon infection or how pathogenic mycobacteria may modulate the macrophage responses. Using primary murine bone marrow macrophages, we established that p38 and extracellular signal-regulated kinases 1 and 2 of the mitogen-activated protein kinase (MAPK) pathways are activated upon infection with different species of mycobacteria. However, we observed decreased MAPK activity over time in macrophages infected with pathogenicMycobacterium aviumstrains relative to infections with nonpathogenic mycobacteria. Furthermore, macrophages infected withM. aviumproduced lower levels of TNF-α, interleukin 1β, and inducible nitric oxide synthase 2 than macrophages infected with nonpathogenic species. Inhibitor studies indicate that the MAPKs are required for theMycobacterium-mediated induction of these effector proteins. Our data indicate that MAPKs are activated in macrophages upon invasion by mycobacteria and that this activation is diminished in macrophages infected with pathogenic strains ofM. avium, resulting in decreased production of important immune effector proteins. The decreased MAPK activation associated withM. aviuminfections suggests a novel point of immune intervention by this mycobacterial species.
Mice Lacking Monocyte Chemoattractant Protein 1 Have Enhanced Susceptibility to an Interstitial Polymicrobial Infection Due to Impaired Monocyte Recruitment
Authors: Chae P. , Im M. , Gibson F. , Jiang Y. , Graves D. T. 
Published: July 2002

ABSTRACTMonocyte chemoattractant protein 1 (MCP-1) is an important chemokine that induces monocyte recruitment in a number of different pathologies, including infection. To investigate the role of MCP-1 in protecting a host from a chronic interstitial polymicrobial infection, dental pulps of MCP-1−/−mice and controls were inoculated with six different oral pathogens. In this model the recruitment of leukocytes and the impact of a genetic deletion on the susceptibility to infection can be accurately assessed by measuring the progression of soft tissue necrosis and osteolytic lesion formation. The absence of MCP-1 significantly impaired the recruitment of monocytes, which at later time points was threefold higher in the wild-type mice than in MCP-1−/−mice (P< 0.05). The consequence was significantly enhanced rates of soft tissue necrosis and bone resorption (P< 0.05). We also determined that the MCP-1−/−mice were able to recruit polymorphonuclear leukocytes (PMNs) to a similar or greater extent as controls and to produce equivalent levels ofPorphyromonas gingivalis-specific total immunoglobulin G (IgG) and IgG1. These results point to the importance of MCP-1 expression and monocyte recruitment in antibacterial defense and demonstrate that antibacterial defense is not due to an indirect effect on PMN recruitment or modulation of the adaptive immune response.
Protection of Mice against Brucellosis by Intranasal Immunization withBrucella melitensisLipopolysaccharide as a Noncovalent Complex withNeisseria meningitidisGroup B Outer Membrane Protein
Authors: Bhattacharjee Apurba K. , Van De Verg Lillian , Izadjoo Mina J. , Yuan Liang , Hadfield Ted L. , Zollinger Wendell D. , Hoover David L. 
Published: July 2002

ABSTRACTIntranasal immunization of mice with purifiedBrucella melitensislipopolysaccharide (LPS) as a noncovalent complex withNeisseria meningitidisgroup B outer membrane protein (GBOMP) elicited a high-titer anti-LPS systemic antibody response and a significant mucosal antibody response. The anti-LPS immunoglobulin G (IgG) antibody was predominantly of the IgG1 subtype, although there was some response of the IgG2a, IgG2b, and IgG3 subtypes. The antibody titer remained high for 16 weeks postimmunization. Immunized mice and sham-immunized control mice were challenged intranasally with 104CFU of virulentB. melitensisstrain 16 M 4 weeks after the second dose of vaccine. The numbers of bacteria in lungs, livers, and spleens at 3 days, 9 days, and 8 weeks postchallenge were determined. Bacteria were found in lungs of all mice on day 3, but there was no disseminated infection of liver or spleen. By day 9, 40% of the mice had infected spleens and livers. At 8 weeks postchallenge, spleens of 25 of 62 immunized mice were infected, compared to 61 of 62 control mice (P< 0.0001). The livers of 12 of 43 immunized mice were infected, compared to 22 of 36 control mice (P= 0.005). In contrast, the lungs of 26 of 46 immunized mice were still infected, compared to 27 of 44 control mice. The numbers of bacterial CFU in lungs of immunized and control animals were identical. These studies show that intranasal immunization withB. melitensisLPS-GBOMP subunit vaccine significantly protects mice against intranasal challenge with virulentB. melitensis.Vaccination reduces bacterial dissemination to spleen and liver but has no effect on the course of lung infection.
Human Monocytes KillShigella flexneribut Then Die by Apoptosis Associated with Suppression of Proinflammatory Cytokine Production
Authors: Hathaway Lucy J. , Griffin George E. , Sansonetti Philippe J. , Edgeworth Jonathan D. 
Published: July 2002

ABSTRACTShigella flexneriinfection of human macrophages is followed by rapid bacterial escape into the cytosol and secretion of IpaB, which activates caspase-1 to mediate cell death and release of mature interleukin (IL)-1β. Here we report a different outcome following infection of human peripheral blood monocytes.S. flexneriinfects monocytes inefficiently in the absence of complement and, following complement-dependent uptake, cannot escape the endosomal compartment. Consequently, bacteria are killed within the first 60 min in the absence of monocyte cell death, as demonstrated by immunofluorescence and electron microscopy and enumeration of colonies in a gentamicin protection assay. Despite early bacterial death, wild-typeS. flexneriinfluenced the subsequent monocyte proinflammatory cytokine response and cell fate. Infection with wild-typeS. flexneriresulted in IpaB-dependent suppression of IL-1β, tumor necrosis factor alpha, and IL-6 compared with that of plasmid-cured avirulentS. flexneri-infected cells. Furthermore, over the following 6 to 8 h, virulentS. flexneri-infected monocytes died by apoptosis whereas avirulent infected monocytes died by necrosis. Together, these results imply that monocytes migrating into the inflammatory site during the early stages of shigellosis killS. flexneribut that during bacterial uptake, they receive virulence signals fromS. flexneriwhich induce delayed apoptosis associated with suppression of the proinflammatory cytokine response to bacterial phagocytosis. This delayed apoptosis may have important effects on the ordered initiation of the innate immune response, leading to the excessive inflammatory response characteristic of shigellosis.
Expression and Characterization of the Chitin-Binding Domain of Chitinase A1 from
Bacillus circulans
WL-12
Authors: Hashimoto Masayuki , Ikegami Takahisa , Seino Shizuka , Ohuchi Nobuhumi , Fukada Harumi , Sugiyama Junji , Shirakawa Masahiro , Watanabe Takeshi 
Published: July 2002

ABSTRACT

Chitinase A1 from
Bacillus circulans
WL-12 comprises an N-terminal catalytic domain, two fibronectin type III-like domains, and a C-terminal chitin-binding domain (ChBD). In order to study the biochemical properties and structure of the ChBD, ChBD
ChiA1
was produced in
Escherichia coli
using a pET expression system and purified by chitin affinity column chromatography. Purified ChBD
ChiA1
specifically bound to various forms of insoluble chitin but not to other polysaccharides, including chitosan, cellulose, and starch. Interaction of soluble chitinous substrates with ChBD
ChiA1
was not detected by means of nuclear magnetic resonance and isothermal titration calorimetry. In addition, the presence of soluble substrates did not interfere with the binding of ChBD
ChiA1
to regenerated chitin. These observations suggest that ChBD
ChiA1
recognizes a structure which is present in insoluble or crystalline chitin but not in chito-oligosaccharides or in soluble derivatives of chitin. ChBD
ChiA1
exhibited binding activity over a wide range of pHs, and the binding activity was enhanced at pHs near its pI and by the presence of NaCl, suggesting that the binding of ChBD
ChiA1
is mediated mainly by hydrophobic interactions. Hydrolysis of β-chitin microcrystals by intact chitinase A1 and by a deletion derivative lacking the ChBD suggested that the ChBD is not absolutely required for hydrolysis of β-chitin microcrystals but greatly enhances the efficiency of degradation.
Distinctiveness of Genotypes ofHelicobacter pyloriin Calcutta, India
Authors: Mukhopadhyay Asish K. , Kersulyte Dangeruta , Jeong Jin-Yong , Datta Simanti , Ito Yoshiyuki , Chowdhury Abhijit , Chowdhury Sujit , Santra Amal , Bhattacharya Sujit K. , Azuma Takeshi , Nair G. Balakrish , Berg Douglas E. 
Published: July 2002

ABSTRACTThe genotypes of 78 strains ofHelicobacter pylorifrom Calcutta, India (55 from ulcer patients and 23 from more-benign infections), were studied, with a focus on putative virulence genes and neutral DNA markers that were likely to be phylogenetically informative. PCR tests indicated that 80 to 90% of Calcutta strains carried thecagpathogenicity island (PAI) and potentially toxigenicvacAs1alleles of the vacuolating cytotoxin gene (vacA), independent of disease status. This was higher than in the West (wherecagPAI+vacAs1genotypes are disease associated) but lower than in east Asia. TheiceA2gene was weakly disease associated in Calcutta, whereas in the West the alternative but unrelatediceA1gene at the same locus is weakly disease associated. DNA sequence motifs ofvacAm1(middle region) alleles formed a cluster that was distinct from those of east Asia and the West, whereas thecagAsequences of Calcutta and Western strains were closely related. An internal deletion found in 20% of CalcuttaiceA1genes was not seen in any of ∼200 strains studied from other geographic regions and thus seemed to be unique to thisH. pyloripopulation. Two mobile DNAs that were rare in east Asian strains were also common in Calcutta. About 90% of Calcutta strains were metronidazole resistant. These findings support the idea thatH. pylorigene pools differ regionally and emphasize the potential importance of studies of Indian and other non-WesternH. pyloripopulations in developing a global understanding of this gastric pathogen and associated disease.
The Archaeon
Sulfolobus solfataricus
Contains a Membrane-Associated Protein Kinase Activity That Preferentially Phosphorylates Threonine Residues In Vitro
Authors: Lower Brian H. , Bischoff Kenneth M. , Kennelly Peter J. 
Published: July 2002

ABSTRACT

The extreme acidothermophilic archaeon
Sulfolobus solfataricus
harbors a membrane-associated protein kinase activity. Its solubilization and stabilization required detergents, suggesting that this activity resides within an integral membrane protein. The archaeal protein kinase utilized purine nucleotides as phosphoryl donors in vitro. A noticeable preference for nucleotide triphosphates over nucleotide diphosphates and for adenyl nucleotides over the corresponding guanyl ones was observed. The molecular mass of the solubilized, partially purified enzyme was estimated to be ≈125 kDa by gel filtration chromatography. Catalytic activity resided in a polypeptide with an apparent molecular mass of ≈67 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Challenges with several exogenous substrates revealed the protein kinase to be relatively selective. Only casein, histone H4, reduced carboxyamidomethylated and maleylated lysozyme, and a peptide modeled after myosin light chains (KKRAARATSNVFA) were phosphorylated to appreciable levels in vitro. All of the aforementioned substrates were phosphorylated on threonine residues, while histone H4 was phosphorylated on serine as well. Substitution of serine for the phosphoacceptor threonine in the myosin light chain peptide produced a noticeably inferior substrate. The protein kinase underwent autophosphorylation on threonine and was relatively insensitive to a set of known inhibitors of “eukaryotic” protein kinases.
Influence of Deletions within Domain II of Exotoxin A on Its Extracellular Secretion from
Pseudomonas aeruginosa
Authors: Voulhoux Romé , Taupiac Marie-Pierre , Czjzek Mirjam , Beaumelle Bruno , Filloux Alain 
Published: July 2002

ABSTRACT

Pseudomonas aeruginosa
is a gram-negative bacterium that secretes many proteins into the extracellular medium via the Xcp machinery. This pathway, conserved in gram-negative bacteria, is called the type II pathway. The exoproteins contain information in their amino acid sequence to allow targeting to their secretion machinery. This information may be present within a conformational motif. The nature of this signal has been examined for
P. aeruginosa
exotoxin A (PE). Previous studies failed to identify a common minimal motif required for Xcp-dependent recognition and secretion of PE. One study identified a motif at the N terminus of the protein, whereas another one found additional information at the C terminus. In this study, we assess the role of the central PE domain II composed of six α-helices (A to F). The secretion behavior of PE derivatives, individually deleted for each helix, was analyzed. Helix E deletion has a drastic effect on secretion of PE, which accumulates within the periplasm. The conformational rearrangement induced in this variant is predicted from the three-dimensional PE structure, and the molecular modification is confirmed by gel filtration experiments. Helix E is in the core of the molecule and creates close contact with other domains (I and III). Deletion of the surface-exposed helix F has no effect on secretion, indicating that no secretion information is contained in this helix. Finally, we concluded that disruption of a structured domain II yields an extended form of the molecule and prevents formation of the conformational secretion motif.
Metronidazole Activation Is Mutagenic and Causes DNA Fragmentation in
Helicobacter pylori
and in
Escherichia coli
Containing a Cloned
H. pylori rdxA
+
(Nitroreductase) Gene
Authors: Sisson Gary , Jeong Jin-Yong , Goodwin Avery , Bryden Louis , Rossler Norma , Lim-Morrison Sabrina , Raudonikiene Ausra , Berg Douglas E. , Hoffman Paul S. 
Published: July 2002

ABSTRACT

Much of the normal high sensitivity of wild-type
Helicobacter pylori
to metronidazole (Mtz) depends on
rdxA
(HP0954), a gene encoding a novel nitroreductase that catalyzes the conversion of Mtz from a harmless prodrug to a bactericidal agent. Here we report that levels of Mtz that partially inhibit growth stimulate forward mutation to rifampin resistance in
rdxA
+
(Mtz
s
) and also in
rdxA
(Mtz
r
)
H. pylori
strains, and that expression of
rdxA
in
Escherichia coli
results in equivalent Mtz-induced mutation. A reversion test using defined
lac
tester strains of
E. coli
carrying
rdxA
+
indicated that CG-to-GC transversions and AT-to-GC transitions are induced more frequently than other base substitutions. Alkaline gel electrophoretic tests showed that Mtz concentrations near or higher than the MIC for growth also caused DNA breakage in
H. pylori
and in
E. coli
carrying
rdxA
+
, suggesting that this damage may account for most of the bactericidal action of Mtz. Coculture of Mtz
s
H. pylori
with
E. coli
(highly resistant to Mtz) in the presence of Mtz did not stimulate forward mutation in
E. coli
, indicating that the mutagenic and bactericidal products of Mtz metabolism do not diffuse significantly to neighboring (bystander) cells. Our results suggest that the widespread use of Mtz against other pathogens in people chronically infected with
H. pylori
may stimulate mutation and recombination in
H. pylori
, thereby speeding host-specific adaptation, the evolution of virulence, and the emergence of resistance against Mtz and other clinically useful antimicrobials.
Predicted Highly Expressed Genes of Diverse Prokaryotic Genomes
Authors: Karlin Samuel , Mrázek Jan 
Published: July 2002

ABSTRACT

Our approach in predicting gene expression levels relates to codon usage differences among gene classes. In prokaryotic genomes, genes that deviate strongly in codon usage from the average gene but are sufficiently similar in codon usage to ribosomal protein genes, to translation and transcription processing factors, and to chaperone-degradation proteins are predicted highly expressed (PHX). By these criteria, PHX genes in most prokaryotic genomes include those encoding ribosomal proteins, translation and transcription processing factors, and chaperone proteins and genes of principal energy metabolism. In particular, for the fast-growing species
Escherichia coli
,
Vibrio cholerae
,
Bacillus subtilis
, and
Haemophilus influenzae
, major glycolysis and tricarboxylic acid cycle genes are PHX. In
Synechocystis
, prime genes of photosynthesis are PHX, and in methanogens, PHX genes include those essential for methanogenesis. Overall, the three protein families—ribosomal proteins, protein synthesis factors, and chaperone complexes—are needed at many stages of the life cycle, and apparently bacteria have evolved codon usage to maintain appropriate growth, stability, and plasticity. New interpretations of the capacity of
Deinococcus radiodurans
for resistance to high doses of ionizing radiation is based on an excess of PHX chaperone-degradation genes and detoxification genes. Expression levels of selected classes of genes, including those for flagella, electron transport, detoxification, histidine kinases, and others, are analyzed. Flagellar PHX genes are conspicuous among spirochete genomes. PHX genes are positively correlated with strong Shine-Dalgarno signal sequences. Specific regulatory proteins, e.g., two-component sensor proteins, are rarely PHX. Genes involved in pathways for the synthesis of vitamins record low predicted expression levels. Several distinctive PHX genes of the available complete prokaryotic genomes are highlighted. Relationships of PHX genes with stoichiometry, multifunctionality, and operon structures are discussed. Our methodology may be used complementary to experimental expression analysis.
Bacillus subtilis ccpA
Gene Mutants Specifically Defective in Activation of Acetoin Biosynthesis
Authors: Turinsky Andrew J. , Moir-Blais Tessa R. , Grundy Frank J. , Henkin Tina M. 
Published: July 2002

ABSTRACT

A large number of carbon source utilization pathways are repressed in
Bacillus subtilis
by the global regulator CcpA, which also acts as an activator of carbon excretion pathways during growth in media containing glucose. In this study, CcpA mutants defective in transcriptional activation of the
alsSD
operon, which is involved in acetoin biosynthesis, were identified. These mutants retained normal glucose repression of
amyE
, encoding α-amylase, and
acsA
, encoding acetyl-coenzyme A synthetase, and normal activation of
ackA
, which is involved in acetate excretion; in these
ccpA
mutants the CcpA functions of activation of the acetate and acetoin excretion pathways appear to be separated.