bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of Recombinant, Ureolytic
Streptococcus mutans
Demonstrates an Inverse Relationship between Dental Plaque Ureolytic Capacity and Cariogenicity
Authors: Clancy K. Anne , Pearson Sylvia , Bowen William H. , Burne Robert A. 
Published: July 2002

ABSTRACT

Dental caries results from prolonged plaque acidification that leads to the establishment of a cariogenic microflora and demineralization of the tooth. Urease enzymes of oral bacteria hydrolyze urea to ammonia, which can neutralize plaque acids. To begin to examine the relationship between plaque ureolytic activity and the incidence of dental caries, recombinant, ureolytic strains of
Streptococcus mutans
were constructed. Specifically, the
ureABCEFGD
operon from
Streptococcus salivarius
57.I was integrated into the
S. mutans
chromosome in such a way that the operon was transcribed from a weak, cognate promoter in
S. mutans
ACUS4 or a stronger promoter in
S. mutans
ACUS6. Both strains expressed NiCl
2
-dependent urease activity, but the maximal urease levels in ACUS6 were threefold higher than those in ACUS4. In vitro pH drop experiments demonstrated that the ability of the recombinant
S. mutans
strains to moderate a decrease in pH during the simultaneous metabolism of glucose and urea increased proportionately with the level of urease activity expressed. Specific-pathogen-free rats that were infected with ACUS6 and fed a cariogenic diet with drinking water containing 25 mM urea and 50 μM NiCl
2
had relatively high levels of oral urease activity, as well as dramatic decreases in the prevalence of smooth-surface caries and the severity of sulcal caries, relative to controls. Urease activity appears to influence plaque biochemistry and metabolism in a manner that reduces cariogenicity, suggesting that recombinant, ureolytic bacteria may be useful to promote dental health.
Protection Elicited by Native Outer Membrane Protein Oms66 (p66) against Host-AdaptedBorrelia burgdorferi: Conformational Nature of Bactericidal Epitopes
Authors: Exner Maurice M. , Wu Xiaoyang , Blanco David R. , Miller James N. , Lovett Michael A. 
Published: July 2002

ABSTRACTOms66 is aBorrelia burgdorferiouter membrane porin protein whose role in Lyme disease pathogenesis and immunity has not been well established. Oms66 was solubilized from whole-cell lysates of strain B313 (which is derived from B31 but lacks OspA, -B, -C, and -D) and purified to homogeneity by fast-protein liquid chromatography. Purified native Oms66 (nOms66), which retained the ability to form large channels in a planar lipid bilayer model membrane system, and denatured Oms66 (hOms66) were used to immunize New Zealand White rabbits. The resulting Oms66 antisera were tested in a complement-dependent borreliacidal assay in parallel with basal serum and with serum from rabbits immune to reinfection withB. burgdorferi(IRS). IRS showed high-titer complement-dependent killing of both strains B31 and B313. Sera from animals immunized with nOms66 showed high-titer complement-dependent killing activity against strain B313 but exhibited no killing of B31. By comparison, serum generated from immunizations with hOms66 showed no killing activity against either strain. Following adsorption of antiserum to nOms66 with recombinant Oms66 (rOms66), the serum antibodies no longer bound to rOms66 or to nOms66 that had been denatured with 8 M urea. However, the antibodies still bound to nOms66 and killing activity against B313 was retained, thus suggesting that native, conformational epitopes are targets of this bactericidal activity. Six C3H HeJ mice were immunized with nOms66 and were challenged using “host-adapted”B. burgdorferiB31 by skin implantation of infected mouse ear tissue. Four of the six mice were protected against both localized and disseminated infection. These findings indicate that native Oms66 can elicit potent bactericidal activity and significant protective immunity against host-adapted organisms.
Parenteral Adjuvant Activities ofEscherichia coliHeat-Labile Toxin and Its B Subunit for Immunization of Mice against GastricHelicobacter pyloriInfection
Authors: Weltzin Richard , Guy Bruno , Thomas William D. , Giannasca Paul J. , Monath Thomas P. 
Published: July 2002

ABSTRACTThe heat-labile toxin (LT) ofEscherichia coliis a potent mucosal adjuvant that has been used to induce protective immunity againstHelicobacter felisandHelicobacter pyloriinfection in mice. We studied whether recombinant LT or its B subunit (LTB) has adjuvant activity in mice when delivered withH. pyloriurease antigen via the parenteral route. Mice were immunized subcutaneously or intradermally with urease plus LT, recombinant LTB, or a combination of LT and LTB prior to intragastric challenge withH. pylori. Control mice were immunized orally with urease plus LT, a regimen shown previously to protect againstH. pylorigastric infection. Parenteral immunization using either LT or LTB as adjuvant protected mice againstH. pylorichallenge as effectively as oral immunization and enhanced urease-specific immunoglobulin G (IgG) responses in serum as effectively as aluminum hydroxide adjuvant. LT and LTB had adjuvant activity at subtoxic doses and induced more consistent antibody responses than those observed with oral immunization. A mixture of a low dose of LT and a high dose of LTB stimulated the highest levels of protection and specific IgG in serum. Urease-specific IgG1 and IgG2a antibody subclass responses were stimulated by all immunization regimens tested, but relative levels were dependent on the adjuvant used. Compared to parenteral immunization with urease alone, LT preferentially enhanced IgG1, while LTB or the LT-LTB mixture preferentially enhanced IgG2a. Parenteral immunization using LT or LTB as adjuvant also induced IgA to urease in the saliva of some mice. These results show that LT and LTB stimulate qualitatively different humoral immune responses to urease but are both effective parenteral adjuvants for immunization of mice againstH. pyloriinfection.
Inducible Expression of Human β-Defensin 2 byFusobacterium nucleatumin Oral Epithelial Cells: Multiple Signaling Pathways and Role of Commensal Bacteria in Innate Immunity and the Epithelial Barrier
Authors: Krisanaprakornkit Suttichai , Kimball Janet R. , Weinberg Aaron , Darveau Richard P. , Bainbridge Brian W. , Dale Beverly A. 
Published: July 2002

ABSTRACTHuman gingival epithelial cells (HGE) express two antimicrobial peptides of the β-defensin family, human β-defensin 1 (hBD-1) and hBD-2, as well as cytokines and chemokines that contribute to innate immunity. In the present study, the expression and transcriptional regulation of hBD-2 was examined. HBD-2 mRNA was induced by cell wall extract ofFusobacterium nucleatum, an oral commensal microorganism, but not by that ofPorphyromonas gingivalis, a periodontal pathogen. HBD-2 mRNA was also induced by the proinflammatory cytokine tumor necrosis factor alpha (TNF-α) and phorbol myristate acetate (PMA), an epithelial cell activator. HBD-2 mRNA was also expressed in 14 of 15 noninflamed gingival tissue samples. HBD-2 peptide was detected by immunofluorescence in HGE stimulated withF. nucleatumcell wall, consistent with induction of the mRNA by this stimulant. Kinetic analysis indicates involvement of multiple distinct signaling pathways in the regulation of hBD-2 mRNA; TNF-α andF. nucleatumcell wall induced hBD-2 mRNA rapidly (2 to 4 h), while PMA stimulation was slower (∼10 h). In contrast, each stimulant induced interleukin 8 (IL-8) within 1 h. The role of TNF-α as an intermediary inF. nucleatumsignaling was ruled out by addition of anti-TNF-α that did not inhibit hBD-2 induction. However, inhibitor studies show thatF. nucleatumstimulation of hBD-2 mRNA requires both new gene transcription and new protein synthesis. Bacterial lipopolysaccharides isolated fromEscherichia coliandF. nucleatumwere poor stimulants of hBD-2, although they up-regulated IL-8 mRNA. Collectively, our findings show inducible expression of hBD-2 mRNA via multiple pathways in HGE in a pattern that is distinct from that of IL-8 expression. We suggest that different aspects of innate immune responses are differentially regulated and that commensal organisms have a role in stimulating mucosal epithelial cells in maintaining the barrier that contributes to homeostasis and host defense.
Blood Group A Antigen Is a Coreceptor in
Plasmodium falciparum
Rosetting
Authors: Barragan Antonio , Kremsner Peter G. , Wahlgren Mats , Carlson Johan 
Published: July 2002

ABSTRACT

The malaria parasite
Plasmodium falciparum
utilizes molecules present on the surface of uninfected red blood cells (RBC) for rosette formation, and a dependency on ABO antigens has been previously shown. In this study, the antirosetting effect of immune sera was related to the blood group of the infected human host. Sera from malaria-immune blood group A (or B) individuals were less prone to disrupt rosettes from clinical isolates of blood group A (or B) patients than to disrupt rosettes from isolates of blood group O patients. All fresh clinical isolates and laboratory strains exhibited distinct ABO blood group preferences, indicating that utilization of blood group antigens is a general feature of
P. falciparum
rosetting. Soluble A antigen strongly inhibited rosette formation when the parasite was cultivated in A RBC, while inhibition by glycosaminoglycans decreased. Furthermore, a soluble A antigen conjugate bound to the cell surface of parasitized RBC. Selective enzymatic digestion of blood group A antigen from the uninfected RBC surfaces totally abolished the preference of the parasite to form rosettes with these RBC, but rosettes could still form. Altogether, present data suggest an important role for A and B antigens as coreceptors in
P. falciparum
rosetting.
Characterization of FimY as a Coactivator of Type 1 Fimbrial Expression in
Salmonella enterica
Serovar Typhimurium
Authors: Tinker Juliette K. , Clegg Steven 
Published: July 2002

ABSTRACT

Type 1 fimbriae of
Salmonella enterica
serovar Typhimurium are surface appendages that carry adhesins specific for mannosylated host glycoconjugates. Regulation of the major fimbrial subunit is thought to be controlled by a number of ancillary
fim
genes, including
fimZ
,
fimY
,
fimW
, and
fimU
. Previous studies using a FimZ mutant have indicated that this protein is necessary for
fimA
expression, and in vitro DNA binding assays determined that FimZ is a transcriptional activator that binds directly to the
fimA
promoter. To determine the role of FimY as a potential regulator of fimbrial expression, a
fimY
mutant of serovar Typhimurium was generated by allelic exchange. This mutant was found to be phenotypically nonfimbriate. No transcription from the
fimA
promoter was detected in a
fimY
mutant containing a
fimA-lacZ
reporter construct located on the chromosome. In addition, transcription from the cloned
fimY
promoter was not detected in
Escherichia coli
unless both FimZ and FimY were present, indicating that these proteins also act as coactivators of
fimY
expression. Consistent with these results, there is no transcription from a
fimY-lacZ
reporter construct within a serovar Typhimurium
fimY
or
fimZ
mutant. Studies using the
fimY-lacZ
construct reveal that expression of this gene varies with environmental conditions in a manner similar to
fimA
expression. Extensive in vitro DNA binding assays using extracts from
E. coli
that overexpress FimY, as well as partially purified FimY, were unable to identify a specific interaction between FimY and the
fimA
or
fimY
promoter. The results indicate that FimY is a positive regulator of fimbrial expression and that this protein acts in cooperation with FimZ to regulate the expression of
Salmonella
type 1 fimbrial appendages.
Schistosoma mansoniPhosphoenolpyruvate Carboxykinase, a Novel Egg Antigen: Immunological Properties of the Recombinant Protein and Identification of a T-Cell Epitope
Authors: Asahi Hiroko , Osman Ahmed , Cook Rosemary M. , LoVerde Philip T. , Stadecker Miguel J. 
Published: July 2002

ABSTRACTIn schistosomiasis mansoni, hepatic granulomatous inflammation surrounding parasite eggs is mediated by CD4+T helper (Th) cells sensitized to schistosomal egg antigens (SEA). We previously showed that a prominent lymphoproliferative response of CD4+Th cells from schistosome-infected C57BL/6 (BL/6) mice was directed against a 62-kDa component of SEA. A partial amino acid sequence of the 62-kDa component was found to be identical with one present in the enzyme phosphoenolpyruvate carboxykinase (PEPCK). Based on this sequence, a cDNA clone containing the entire coding region of PEPCK was identified, and the full recombinantSchistosoma mansoniPEPCK (rSm-PEPCK) of 626 amino acids was purified from a prokaryotic expression system. rSm-PEPCK strongly stimulated a specific T-cell hybridoma, 4E6, as well as CD4+Th cells from SEA-immunized BL/6 mice and from infected BL/6, CBA, and BALB/c mice. In the infected mice, rSm-PEPCK elicited significant gamma interferon production as well as, to a lesser extent, production of interleukin-2 and -5. In BL/6 and BALB/c mice, the CD4+Th cell response to rSm-PEPCK was greater than that directed against the egg antigen Sm-p40; conversely, CBA mice responded better to Sm-p40 than to Sm-PEPCK. A 12-amino-acid region (residues 398 to 409: DKSKDPKAHPNS) was demonstrated to contain a T-cell epitope; synthetic peptides containing this epitope significantly stimulated specific hybridoma 4E6 and polyclonal CD4+Th cells. The identification and characterization of immunogenic egg components will contribute to the understanding and possible control of T-cell-mediated schistosomal disease.
In Vivo Administration of Mycobacterial Cord Factor (Trehalose 6,6′-Dimycolate) Can Induce Lung and Liver Granulomas and Thymic Atrophy in Rabbits
Authors: Hamasaki Naoko , Isowa Ko-Ichi , Kamada Kohachi , Terano Yoshitake , Matsumoto Takayuki , Arakawa Tetsuo , Kobayashi Kazuo , Yano Ikuya 
Published: July 2002

ABSTRACT

Trehalose 6,6′-dimycolate (TDM) is a cell surface molecule of
Mycobacterium tuberculosis
. TDM induced a loss of body weight and prominent granulomas in the liver and lungs by the intravenous injection of TDM into rabbits. TDM also induced atrophy of the thymus and spleen due to apoptosis. By contrast, sulfolipid (2,3,6,6′-tetraacyl trehalose 2′-sulfate) induced neither toxicity, nor granuloma formation, nor atrophy of the thymus and spleen. In rabbits the histopathological changes were more dramatic than in mice. The rabbit model may be more sensitive and may provide more information on the beneficial or pathological effects of TDM.
Ruminant Gastrointestinal Cell Proliferation and Clearance of
Escherichia coli
O157:H7
Authors: Magnuson Bernadene A. , Davis Margaret , Hubele Suzanna , Austin Paula R. , Kudva Indira T. , Williams Christopher J. , Hunt Carl W. , Hovde Carolyn J. 
Published: July 2002

ABSTRACT

Human infections with
Escherichia coli
O157:H7 cause hemorrhagic colitis that can progress to a life-threatening sequelae. The most common mode of disease transmission is ingestion of contaminated bovine food products, and it is well established that
E. coli
O157:H7 is a transient member of the bovine microbiota. However, the conditions that induce acquisition and subsequent clearance of this bacterium from the ruminant gastrointestinal tract (GIT) are not understood. Evidence that the rates of epithelial cell proliferation in the lower GIT of cattle are associated with the duration animals remained
E. coli
O157:H7 culture positive is presented. Cattle with slower rates of intestinal cell proliferation in the cecum and the distal colon were culture positive significantly longer than cohort cattle with faster cell proliferation rates. Cell death rates (apoptotic indices) between the short- and long-term culture-positive animals were not different. Typical grain-based finishing diets and forage-based growing diets did not effect GIT cell proliferation or the duration animals remained
E. coli
O157:H7 culture positive. To identify a dietary intervention that would effect GIT cell proliferation, we used sheep as a model ruminant. A fasting-refeeding regime that increased the rate of GIT cell proliferation was developed. The fasting-refeeding protocol was used in cattle to test the hypothesis that feeding interventions that increase the rate of GIT cell proliferation induce the clearance of
E. coli
O157:H7 from the bovine GIT.
Clostridium perfringens
Iota-Toxin Requires Activation of Both Binding and Enzymatic Components for Cytopathic Activity
Authors: Gibert Maryse , Petit Laetitia , Raffestin Stephanie , Okabe Akinobu , Popoff Michel R. 
Published: July 2002

ABSTRACT

Iota-toxin is produced by
Clostridium perfringens
type E strains and consists of two independent components, the enzymatic and binding components, referred to as Ia and Ib, respectively. A recombinant
C. perfringens
strain, strain 667/pMRP147, produced processed Ia and partially processed Ib, while a recombinant
C. perfringens
type A strain, strain TS133/pMRP147, in which the VirR-VirS two-component system is inactivated, produced only precursor forms of Ia and Ib. This suggests that iota-toxin is processed by a VirR-VirS-responsive protease, although not completely in the recombinant type A strain. The precursor forms of Ia and Ib were purified from cultures of the latter strain, and their proteolytic activation was examined. Treatment with proteases cleaved off small peptides (9 to 13 amino acid residues) and a 20-kDa peptide from the N termini of the Ia and Ib precursors, respectively, leading to their active forms. They were activated efficiently by α-chymotrypsin, pepsin, proteinase K, subtilisin, and thermolysin but only weakly by trypsin, as demonstrated by the cell-rounding assay. λ-Protease from the
C. perfringens
type E strain, which was found to be a zinc-dependent protease related to thermolysin, activated iota-toxin as efficiently as did α-chymotrypsin. These results suggest that λ-protease is most responsible for the activation of iota-toxin in type E strains.
Low Interleukin-12 Activity in SeverePlasmodium falciparumMalaria
Authors: Luty Adrian J. F. , Perkins Douglas J. , Lell Bertrand , Schmidt-Ott Ruprecht , Lehman Leopold G. , Luckner Doris , Greve Bernhard , Matousek Peter , Herbich Klaus , Schmid Daniela , Weinberg J. Brice , Kremsner Peter G. 
Published: July 2002

ABSTRACTWe compared interleukin-12 (IL-12) and other cytokine activities during and after an acute clinical episode in a matched-pair case-control study of young African children who presented with either mild or severePlasmodium falciparummalaria. The acute-phase, pretreatment plasma IL-12 and alpha interferon (IFN-α) levels, as well as the acute-phase mitogen-stimulated whole-blood production capacity of IL-12, were significantly lower in children with severe rather than mild malaria. IL-12 levels, in addition, showed strong inverse correlations both with parasitemia and with the numbers of circulating malaria pigment-containing neutrophils. Acute-phase plasma tumor necrosis factor (TNF) and IL-10 levels were significantly higher in those with severe malaria, and the concentrations of both of these cytokines were positively correlated both with parasitemia and with the numbers of pigment-containing phagocytes in the blood. Children with severe anemia had the highest levels of TNF in plasma. In all the children, the levels in plasma and production capacities of all cytokines normalized when they were healthy and parasite free. The results indicate that severe but not mildP. falciparummalaria in young, nonimmune African children is characterized by down-regulated IL-12 activity, contrasting markedly with the up-regulation of both TNF and IL-10 in the same children. A combination of disturbed phagocyte functions resulting from hemozoin consumption, along with reduced IFN-γ responses, may contribute to these differential effects.
Identification and Subcellular Localization of the
Legionella pneumophila
IcmX Protein: a Factor Essential for Establishment of a Replicative Organelle in Eukaryotic Host Cells
Authors: Matthews Miguelina , Roy Craig R. 
Published: July 2002

ABSTRACT

The gram-negative respiratory pathogen
Legionella pneumophila
infects and grows within mammalian macrophages and protozoan host cells. Upon uptake into macrophages,
L. pneumophila
establishes a replicative organelle that avoids fusion with endocytic vesicles. There are 24
dot/icm
genes on the
L. pneumophila
chromosome required for biogenesis of this vacuole. Many of the Dot/Icm proteins are predicted to be components of a membrane-bound secretion apparatus similar to type IV conjugal transfer systems. We have been investigating the function of
L. pneumophila dot/icm
gene products that do not have obvious orthologs in other type IV transfer systems, since these determinants could govern processes unique to phagosome biogenesis. The
icmX
gene product falls into this category. To understand the role of the IcmX protein in pathogenesis, we have detailed interactions between an
L. pneumophila icmX
deletion mutant and murine bone marrow-derived macrophages. These data demonstrate that
icmX
is required for biogenesis of the
L. pneumophila
replicative organelle. Immunoblot analysis indicates that the
icmX
gene product is a polypeptide with an estimated molecular mass of 50 kDa. The IcmX protein was localized to the bacterial periplasm, and periplasmic translocation was mediated by an N-terminal
sec
-dependent leader peptide. A truncated IcmX product was secreted into culture supernatants by wild-type
L. pneumophila
growing extracellularly in liquid media; however, transport of the IcmX protein into eukaryotic host cells was not detected. Proteins similar in molecular weight to IcmX were identified in other
Legionella
species by immunoblot analysis using a monoclonal antibody specific for
L. pneumophila
IcmX protein. From these data, we conclude that the IcmX protein is an essential component of the
dot/icm
secretion apparatus, and that a conserved mechanism of host cell parasitism exists for members of the
Legionellaceae
family.
The Human Cationic Antimicrobial Protein (hCAP-18) Is Expressed in the Epithelium of Human Epididymis, Is Present in Seminal Plasma at High Concentrations, and Is Attached to Spermatozoa
Authors: Malm Johan , Sørensen Ole , Persson Terese , Frohm-Nilsson Margareta , Johansson Bengt , Bjartell Anders , Lilja Hans , Ståhle-Bäckdahl Mona , Borregaard Niels , Egesten Arne 
Published: July 2002

ABSTRACTInnate immunity is important for the integrity of the host against potentially invasive pathogenic microorganisms in the environment. Antibiotic peptides with broad antimicrobial activity are part of the innate immune system. We investigated the presence of the cathelicidin, human cationic antimicrobial protein (hCAP-18), in the male reproductive system. We found strong expression of the hCAP-18 gene by in situ hybridization and hCAP-18 protein, as detected by immunohistochemistry, in the epithelium of the epididymis, but not in the testis. The highest expression in the epididymis was in the caudal part. Western blotting showed a doublet band, the upper part corresponding to the size of hCAP-18 in plasma and neutrophils. Using a specific enzyme-linked immunosorbent assay (ELISA), levels of 86.5 ± 37.8 μg/ml (mean ± standard deviation; range, 41.8 to 142.8 μg/ml;n= 10) were detected in seminal plasma from healthy donors, which is 70-fold higher than the level in blood plasma. Flow cytometry and immunocytochemistry revealed the presence of hCAP-18 on spermatozoa. ELISA measurement showed levels of 196 ng/106spermatozoa, corresponding to 6.6 × 106molecules of hCAP-18 per spermatozoon. Our results suggest a key role for hCAP-18 in the antibacterial integrity of the male reproductive system. The attachment of hCAP-18 to spermatozoa may implicate a role for hCAP-18 in conception.