bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mucosal Immune Responses and Protection against Tetanus Toxin after Intranasal Immunization with RecombinantLactobacillus plantarum
Authors: Grangette Corinne , Müller-Alouf Heide , Goudercourt Denise , Geoffroy Marie-Claude , Turneer Mireille , Mercenier Annick 
Published: July 2002

ABSTRACTThe use of live microorganisms as an antigen delivery system is an effective means to elicit local immune responses and thus represents a promising strategy for mucosal vaccination. In this respect, lactic acid bacteria represent an original and attractive approach, as they are safe organisms that are used as food starters and probiotics. To determine whether an immune response could be elicited by intranasal delivery of recombinant lactobacilli, aLactobacillus plantarumstrain of human origin (NCIMB8826) was selected as the expression host. Cytoplasmic production of the 47-kDa fragment C of tetanus toxin (TTFC) was achieved at different levels depending on the plasmid construct. All recombinant strains proved to be immunogenic by the intranasal route in mice and able to elicit very high systemic immunoglobulin G (IgG1, IgG2b, and IgG2a) responses which correlated to the antigen dose. No significant differences in enzyme-linked immunosorbent assay IgG titers were observed when mice were immunized with live or mitomycin C-treated recombinant lactobacilli. Nevertheless, protection against the lethal effect of tetanus toxin was obtained only with the strains producing the highest dose of antigen and was greater following immunization with live bacteria. Significant TTFC-specific mucosal IgA responses were measured in bronchoalveolar lavage fluids, and antigen-specific T-cell responses were detected in cervical lymph nodes, both responses being higher in mice receiving a double dose of bacteria (at a 24-h interval) at each administration. These results demonstrate that recombinant lactobacilli can induce specific humoral (protective) and mucosal antibodies and cellular immune response against protective antigens upon nasal administration.
Novel Genetic and Phenotypic Heterogeneity in
Bordetella bronchiseptica
Pertactin
Authors: Register Karen B. 
Published: July 2002

ABSTRACT

The
Bordetella bronchiseptica
outer membrane protein pertactin is believed to function as an adhesin and is an important protective immunogen. Previous sequence analysis of the pertactin gene identified two regions predicted to encode amino acid repeat motifs. Recent studies have documented DNA sequence heterogeneity in both regions. The present study describes additional variants in these regions, which form the basis for six novel pertactin types. Immunoblotting demonstrated phenotypic heterogeneity in pertactin consistent with the predicted combined sizes of the repeat regions. A revised system for classifying
B. bronchiseptica
pertactin variants is proposed.
Induction of Inducible Nitric Oxide Synthase-NO· by Lipoarabinomannan ofMycobacterium tuberculosisIs Mediated by MEK1-ERK, MKK7-JNK, and NF-κB Signaling Pathways
Authors: Chan Edward D. , Morris Kristin R. , Belisle John T. , Hill Preston , Remigio Linda K. , Brennan Patrick J. , Riches David W. H. 
Published: July 2002

ABSTRACTNitric oxide (NO· ) expression by inducible nitric oxide synthase (iNOS) is an important host defense mechanism againstMycobacterium tuberculosisin mononuclear phagocytes. The objective of this investigation was to examine the role of mitogen-activated protein (MAP) kinase (MAPK) and nuclear factor κB (NF-κB) signaling pathways in the regulation of iNOS and NO· by a mycobacterial cell wall lipoglycan known as mannose-capped lipoarabinomannan (ManLAM). Specific pharmacologic inhibition of the extracellular-signal-regulated kinase (ERK) or NF-κB pathway revealed that both these signaling cascades were required in gamma interferon (IFN-γ)-ManLAM-induced iNOS protein and NO2−expression in mouse macrophages. Transient cotransfection of dominant-negative protein mutants of the c-Jun NH2-terminal kinase (JNK) pathway revealed that the MAP kinase kinase 7 (MKK7)-JNK cascade also mediated IFN-γ–ManLAM induction of iNOS promoter activity whereas MKK4 did not. Overexpression of null mutant IκBα, a potent inhibitor of NF-κB activation, confirmed that the IκBα kinase (IKK)–NF-κB signaling pathway enhanced IFN-γ–ManLAM-induced iNOS promoter activity. By contrast, activated p38mapkinhibited iNOS induction. These results indicate that combined IFN-γ and ManLAM stimulation induced iNOS and NO· expression and that MEK1-ERK, MKK7-JNK, IKK–NF-κB, and p38mapksignaling pathways play important regulatory roles.
Increased Immunogenicity and Induction of Class Switching by Conjugation of Complement C3d to Pneumococcal Serotype 14 Capsular Polysaccharide
Authors: Test Samuel T. , Mitsuyoshi Joyce , Connolly Charles C. , Lucas Alexander H. 
Published: July 2002

ABSTRACTPrevious studies have demonstrated an adjuvant effect for the C3d fragment of complement C3 when coupled to T-dependent protein antigens. In this study, we examined the antibody response to covalent conjugates of C3d and a T-independent antigen, the capsular polysaccharide of serotype 14Streptococcus pneumoniae(PPS14). We prepared a conjugate of mouse C3d and PPS14 and compared its immunogenicity with that of a conjugate of PPS14 and ovalbumin (OVA). When BALB/c mice were immunized with PPS14-C3d, there was a significant increase in serum anti-PPS14 concentrations compared with either native PPS14 or control PPS14-glycine conjugates. This was accompanied by a switch in anti-PPS14 from predominantly immunoglobulin M (IgM) to IgG1 by day 25 following primary immunization. Following secondary immunization with PPS14-C3d, there was a marked booster response and a further increase in the ratio of IgG1 to IgM anti-PPS14. Although the primary antibody response to the PPS14-OVA conjugate exceeded that induced by immunization with PPS14-C3d, serum anti-PPS14 concentrations after a second injection of PPS14-C3d were nearly identical to those induced by secondary immunization with PPS14-OVA. Experiments with athymic nude mice suggested that T cells were not required for the adjuvant effect of C3d on the primary immune response to PPS14 but were necessary for enhancement of the memory response after a second injection of PPS14-C3d. These studies show that the adjuvant effects of C3d extend to T-independent antigens as well as T-dependent antigens. As a means of harnessing the adjuvant potential of the innate immune system, C3d conjugates may prove useful as a component of vaccines against encapsulated bacteria.
Down-Regulation of Glycosylphosphatidylinositol-Specific Phospholipase D Induced by Lipopolysaccharide and Oxidative Stress in the Murine Monocyte- Macrophage Cell Line RAW 264.7
Authors: Du Xiaohan , Low Martin G. 
Published: July 2002

ABSTRACTSerum glycosylphosphatidylinositol-specific phospholipase D (GPI-PLD) activity is reduced over 75% in systemic inflammatory response syndrome. To investigate the mechanism of this response, expression of the GPI-PLD gene was studied in the mouse monocyte-macrophage cell line RAW 264.7 stimulated with lipopolysaccharide (LPS; 0.5 to 50 ng/ml). GPI-PLD mRNA was reduced approximately 60% in a time- and dose-dependent manner. Oxidative stress induced by 0.5 mM H2O2or 50 μM menadione also caused a greater than 50% reduction in GPI-PLD mRNA. The antioxidantN-acetyl-l-cysteine attenuated the down-regulatory effect of H2O2but not of LPS. Cotreatment of the cells with actinomycin D inhibited down-regulation induced by either LPS or H2O2. The half-life of GPI-PLD mRNA was not affected by LPS, or decreased slightly with H2O2, indicating that the reduction in GPI-PLD mRNA is due primarily to transcriptional regulation. Stimulation with tumor necrosis factor alpha (TNF-α) resulted in ∼40% reduction in GPI-PLD mRNA in human A549 alveolar carcinoma cells but not RAW 264.7 cells, suggesting that alternative pathways could exist in different cell types for down-regulating GPI-PLD expression during an inflammatory response and the TNF-α autocrine signaling mechanism alone is not sufficient to recapitulate the LPS-induced reduction of GPI-PLD in macrophages. Sublines of RAW 264.7 cells with reduced GPI-PLD expression exhibited increased cell sensitivity to LPS stimulation and membrane-anchored CD14 expression on the cell surface. Our data suggest that down-regulation of GPI-PLD could play an important role in the control of proinflammatory responses.
Complete DNA Sequence and Analysis of the Large Virulence Plasmid of
Shigella flexneri
Authors: Venkatesan Malabi M. , Goldberg Marcia B. , Rose Debra J. , Grotbeck Erik J. , Burland Valerie , Blattner Frederick R. 
Published: July 2002

ABSTRACT

The complete sequence analysis of the 210-kb
Shigella flexneri
5a virulence plasmid was determined.
Shigella
spp. cause dysentery and diarrhea by invasion and spread through the colonic mucosa. Most of the known
Shigella
virulence determinants are encoded on a large plasmid that is unique to virulent strains of
Shigella
and enteroinvasive
Escherichia coli
; these known genes account for approximately 30 to 35% of the virulence plasmid. In the complete sequence of the virulence plasmid, 286 open reading frames (ORFs) were identified. An astonishing 153 (53%) of these were related to known and putative insertion sequence (IS) elements; no known bacterial plasmid has previously been described with such a high proportion of IS elements. Four new IS elements were identified. Fifty putative proteins show no significant homology to proteins of known function; of these, 18 have a G+C content of less than 40%, typical of known virulence genes on the plasmid. These 18 constitute potentially unknown virulence genes. Two alleles of
shet2
and five alleles of
ipaH
were also identified on the plasmid. Thus, the plasmid sequence suggests a remarkable history of IS-mediated acquisition of DNA across bacterial species. The complete sequence will permit targeted characterization of potential new
Shigella
virulence determinants.
Periodontal Pathogens Produce Quorum Sensing Signal Molecules
Authors: Frias Jorge , Olle Ester , Alsina Merce 
Published: July 2002

ABSTRACT

Different species of bacteria important in the composition of dental plaque were tested for production of extracellular autoinducer-like activities that stimulate the expression of the luminescence genes in
Vibrio harveyi
. Several strains of
Prevotella intermedia, Fusobacterium nucleatum
, and
Porphyromonas gingivalis
were found to produce such activities. Interestingly, these bacteria belong to the same phylogenetic group, and they are periodontal pathogens important in the development of periodontal disease. They specifically produce extracellular signaling molecule related autoinducer-2 from
V. haveyi
. Nevertheless, they seem to be unable to produce homologues of acyl-homoserine lactones. Furthermore,
Escherichia coli
DH5α can be complemented by the introduction of a
P. gingivalis
gene with high homology to the
luxS
gene, which has been called
luxS
P.g.
.
Biological Activity of a C-Terminal Fragment ofPasteurella multocidaToxin
Authors: Busch Christian , Orth Joachim , Djouder Nabil , Aktories Klaus 
Published: July 2002

ABSTRACTThe protein toxin ofPasteurella multocidaPMT is a potent mitogen and activator of phospholipase Cβ. In this study different toxin fragments were investigated. A C-terminal fragment encompassing amino acids 581 through 1285 (PMT581C) was constructed, which was inactive toward intact embryonic bovine lung (EBL) cells after addition to culture medium but caused reorganization of the actin cytoskeleton and rounding up of cells when introduced into the cells by electroporation. As the holotoxin, the toxin fragment PMT581C induced an increase in total inositol phosphate levels after introduction into the cell by electroporation. A C-terminal fragment shorter than PMT581C as well as N-terminal fragments were inactive. Exchange of cysteine-1165 for serine in the holotoxin resulted in a complete loss of the ability to increase inositol phosphate levels. Correspondingly, the mutated toxin fragment PMT581C.C1165S was inactive after cell introduction by electroporation, suggesting an essential role of Cys-1165 in the biological activity of the toxin.
Diepitopic Construct of Functionally and Epitopically Complementary Peptides Enhances Immunogenicity, Reactivity with Glucosyltransferase, and Protection from Dental Caries
Authors: Taubman Martin A. , Holmberg Cynthia J. , Smith Daniel J. 
Published: July 2002

ABSTRACTCoimmunization with peptide constructs from catalytic (CAT) and glucan-binding (GLU) domains of glucosyltransferase (GTF) of mutans streptococci has resulted in enhanced levels of antibody to the CAT construct and to GTF. We designed and synthesized a diepitopic construct (CAT-GLU) containing two copies of both CAT (B epitope only) and GLU (B and T epitope) peptides. The immunogenicity of this diepitopic construct was compared with that of individual CAT and GLU constructs by immunizing groups of Sprague-Dawley rats subcutaneously in the salivary gland vicinity with the CAT-GLU, CAT, or GLU construct or by treating rats by sham immunization. Levels of serum immunoglobulin G (IgG) antibody to GTF or CAT in the CAT-GLU group were significantly greater than in GLU- or CAT-immunized groups. Immunization with CAT-GLU was compared to coimmunization with a mixture of CAT and GLU in a second rodent experiment under a similar protocol. CAT-GLU immunization resulted in serum IgG and salivary IgA responses to GTF and CAT which were greater than after coimmunization. Immunization with the diepitopic construct and communization with CAT and GLU constructs showed proliferation of T lymphocytes to GTF. Immunization with either the CAT or GLU construct has been shown to elicit significant protection in a rodent dental caries model. Similarly in this study, the enhanced response to GTF after immunization with the CAT-GLU construct resulted in protective effects on dental caries. Therefore, the CAT-GLU diepitopic construct can be a potentially important antigen for a caries vaccine, giving rise to greater immune response than after immunization with CAT, GLU, or a mixture of the two.
Traversal of
Candida albicans
across Human Blood-Brain Barrier In Vitro
Authors: Jong Ambrose Y. , Stins Monique F. , Huang Sheng-He , Chen Steven H. M. , Kim Kwang Sik 
Published: July 2002

ABSTRACT

Candida albicans
is an opportunistic pathogen, which primarily affects neonates and immunocompromised individuals. The pathogen can invade the central nervous system, resulting in meningitis. At present, the pathogenesis of
C. albicans
meningitis is unclear. We used an in vitro model of the human blood-brain barrier to investigate the interaction(s) of
C. albicans
with human brain microvascular endothelial cells (BMEC). Binding of
C. albicans
to human BMEC was time and inoculum dependent. Invasion of
C. albicans
into human BMEC was demonstrated by using an enzyme-linked immunosorbent assay based on fluorescent staining of
C. albicans
with calcoflour. In contrast, avirulent
Candida
mutant strains and nonpathogenic yeast
Saccharomyces cerevisiae
were not able to bind and invade human BMEC. Morphological studies revealed that on association with human BMEC,
C. albicans
formed germ tubes and was able to bud intracellularly. Transmission electron microscopy showed various stages of
C. albicans
interactions with human BMEC, e.g., pseudopod-like structures on human BMEC membrane and intracellular vacuole-like structures retaining
C. albicans
. Of interest,
C. albicans
was able to bud and develop pseudohyphae inside human BMEC without apparent morphological changes of the host cells. In addition,
C. albicans
penetrates through human BMEC monolayers without a detectable change in transendothelial electrical resistance and inulin permeability. This is the first demonstration that
C. albicans
is able to adhere, invade, and transcytose across human BMEC without affecting monolayer integrity. A complete understanding of the interaction(s) of
C. albicans
with human BMEC should contribute to the understanding of the pathogenic mechanism(s) of
C. albicans
meningitis.
Role of Inflammatory Mediators in Resistance and Susceptibility to Pneumococcal Infection
Authors: Kerr Alison R. , Irvine June J. , Search Jennifer J. , Gingles Neill A. , Kadioglu Aras , Andrew Peter W. , McPheat William L. , Booth Charles G. , Mitchell Tim. J. 
Published: July 2002

ABSTRACTVariations in the host response during pneumonia caused byStreptococcus pneumoniaein susceptible (CBA/Ca) and resistant (BALB/c) inbred mouse strains were investigated. Significant differences were detected in survival time, core body temperature, lung-associated and systemic bacterial loads, mast cell numbers, magnitude and location of cytokine production, lung disruption, and ability of isolated lung cells to release the cytokine tumor necrosis factor (TNF) alpha in vitro. Overall, the results indicate that the reduced capacity of CBA/Ca mice to induce rapid TNF activity within the airways following infection withS. pneumoniaemay be a factor in their elevated susceptibility to pneumococcal pneumonia.
A Gene from the Locus of Enterocyte Effacement That Is Required for EnteropathogenicEscherichia coliTo Increase Tight-Junction Permeability Encodes a Chaperone for EspF
Authors: Elliott Simon J. , O'Connell Colin B. , Koutsouris Athanasia , Brinkley Carl , Donnenberg Michael S. , Hecht Gail , Kaper James B. 
Published: July 2002

ABSTRACTDisruption of the barrier properties of the enterocyte tight junction is believed to be important in the pathogenesis of diarrhea caused by enteropathogenicEscherichia coli(EPEC). This phenotype can be measured in vitro as the ability of EPEC to reduce transepithelial resistance (TER) across enterocyte monolayers and requires the products of the locus of enterocyte effacement (LEE) and, in particular, the type III secreted effector protein EspF. We report a second LEE-encoded gene that is also necessary for EPEC to fully reduce TER.rorf10is not necessary for EPEC adherence, EspADB secretion, or formation of attaching and effacing lesions. However,rorf10mutants have a diminished TER phenotype, reduced intracellular levels of EspF, and a reduced ability to translocate EspF into epithelial cells. The product ofrorf10is a 14-kDa intracellular protein rich in α-helices that specifically interacts with EspF but not with Tir or other EPEC secreted proteins. These properties are consistent with the hypothesis thatrorf10encodes a type III secretion chaperone for EspF, and we rename this protein CesF, the chaperone for EPEC secreted protein F.
DsbA and DsbC Are Required for Secretion of Pertussis Toxin by
Bordetella pertussis
Authors: Stenson Trevor H. , Weiss Alison A. 
Published: July 2002

ABSTRACT

The Dsb family of enzymes catalyzes disulfide bond formation in the gram-negative periplasm, which is required for folding and assembly of many secreted proteins. Pertussis toxin is arguably the most complex toxin known: it is assembled from six subunits encoded by five genes (for subunits S1 to S5), with 11 intramolecular disulfide bonds. To examine the role of the Dsb enzymes in assembly and secretion of pertussis toxin, we identified and mutated the
Bordetella pertussis dsbA
,
dsbB
, and
dsbC
homologues. Mutations in
dsbA
or
dsbB
resulted in decreased levels of S1 (the A subunit) and S2 (a B-subunit protein), demonstrating that DsbA and DsbB are required for toxin assembly. Mutations in
dsbC
did not impair assembly of periplasmic toxin but resulted in decreased toxin secretion, suggesting a defect in the formation of the Ptl secretion complex.
Construction and Characterization of an Acapsular Mutant of
Mannheimia haemolytica
A1
Authors: McKerral Linda J. , Lo Reggie Y. C. 
Published: July 2002

ABSTRACT

The
nmaA
and
nmaB
genes, which code for UDP-GlcNAc-2-epimerase and UDP-ManNAc-dehydrogenase, respectively, are involved in capsular polysaccharide biosynthesis in
Mannheimia haemolytica
A1. A chloramphenicol resistance (Cm
r
) cassette cloned behind an
M. haemolytica
A1 promoter,
plpcat
, was created and used to interrupt
nmaA
and
nmaB
. A 1.3-kbp DNA fragment that encompasses part of
nmaA
and
nmaB
was replaced by the 1.0-kbp
plpcat
, resulting in a knockout mutant which is Cm
r
and unable to synthesize
N
-acetylmannosamine (ManNAc) and
N
-acetylmannosaminuronic acid (ManNAcA). The DNA replacement was confirmed by Southern hybridization and PCR analyses of the
nmaA
and
nmaB
loci. Electron microscopy examination of the mutant showed the absence of capsular materials compared to the parent strain. The loss of NmaA and NmaB activity was confirmed by analysis of carbohydrate moieties using capillary electrophoresis. Serum sensitivity assays indicated that the acapsular mutant is as resistant as the encapsulated parent to complement-mediated killing by colostrum-deprived calf serum but is more sensitive to killing by immune bovine serum. Analysis of lipopolysaccharide prepared from the acapsular mutant and encapsulated parent confirmed that these strains have long O-polysaccharide chains, possibly conferring resistance to serum-mediated killing.
Effect of Low- and High-Virulence
Yersinia enterocolitica
Strains on the Inflammatory Response of Human Umbilical Vein Endothelial Cells
Authors: Denecker Geertrui , Tötemeyer Sabine , Mota Luís J. , Troisfontaines Paul , Lambermont Isabelle , Youta Carine , Stainier Isabelle , Ackermann Martin , Cornelis Guy R. 
Published: July 2002

ABSTRACT

Pathogenic strains of
Yersinia
spp. inject a set of Yop effector proteins into eukaryotic cells by using a plasmid-encoded type III secretion system. In this study, we analyzed the inflammatory response of human umbilical vein endothelial cells (HUVECs) after infection with different
Yersinia enterocolitica
strains. We found that both expression of intercellular adhesion molecule 1 and release of the cytokines interleukin-6 (IL-6) and IL-8 by HUVECs are downregulated in a YopP-dependent way, demonstrating that YopP plays a major role in the inflammatory response of these cells. Infection of HUVECs with several low-virulence (biotype 2, 3, and 4) and high-virulence (biotype 1B)
Y. enterocolitica
strains showed that biotype 1B isolates are more efficient in inhibiting the inflammatory response than low-virulence
Y. enterocolitica
strains and that this effect depends on the time of contact. We extended the results of Ruckdeschel et al. and found that on the basis of the presence or absence of arginine-143 of YopP (K. Ruckdeschel, K. Richter, O. Mannel, and J. Heesemann, Infect. Immun.
69:
7652-7662, 2001) all the
Y. enterocolitica
strains used fell into two groups, which correlate with the low- and high-virulence phenotypes. In addition, we found that high-virulence strains inject more YopP into the cytosol of eukaryotic target cells than do low-virulence strains.