bluuebunny/crossref_metadata_2025_split huggingface dataset:
Recombinant
Neisseria meningitidis
Transferrin Binding Protein A Protects against Experimental Meningococcal Infection
Authors: West David , Reddin Karen , Matheson Mary , Heath Robert , Funnell Simon , Hudson Michael , Robinson Andrew , Gorringe Andrew 
Published: July 2002

ABSTRACT

To better characterize the vaccine potential of
Neisseria meningitidis
transferrin binding proteins (Tbps), we have overexpressed TbpA and TbpB from
Neisseria meningitidis
isolate K454 in
Escherichia coli
. The ability to bind human transferrin was retained by both recombinant proteins, enabling purification by affinity chromotography. The recombinant Tbps were evaluated individually and in combination in a mouse intraperitoneal-infection model to determine their ability to protect against meningococcal infection and to induce cross-reactive and bactericidal antibodies. For the first time, TbpA was found to afford protection against meningococcal challenge when administered as the sole immunogen. In contrast to the protection conferred by TbpB, this protection extended to a serogroup C isolate and strain B16B6, a serogroup B isolate with a lower-molecular-weight TbpB than that from strain K454. However, serum from a TbpB-immunized rabbit was found to be significantly more bactericidal than that from a TbpA-immunized animal. Our evidence demonstrates that TbpA used as a vaccine antigen may provide protection against a wider range of meningococcal strains than does TbpB alone. This protection appears not to be due to complement-mediated lysis and indicates that serum bactericidal activity may not always be the most appropriate predictor of efficacy for protein-based meningococcal vaccines.
Haemophilus ducreyi
Associates with Phagocytes, Collagen, and Fibrin and Remains Extracellular throughout Infection of Human Volunteers
Authors: Bauer Margaret E. , Goheen Michael P. , Townsend Carisa A. , Spinola Stanley M. 
Published: July 2002

ABSTRACT

In a previous study,
Haemophilus ducreyi
was found in the pustule and dermis of samples obtained at the clinical end point in the human model of infection. To understand the kinetics of localization, we examined infected sites at 0, 24, and 48 h after inoculation and at the clinical end point. Immediately after inoculation, bacteria were found predominantly in the dermis but also in the epidermis. Few bacteria were detectable at 24 h; however, by 48 h, bacteria were readily seen in the pustule and dermis.
H. ducreyi
was associated with polymorphonuclear leukocytes and macrophages in the pustule and at its base, but was not associated with T cells, Langerhans' cells, or fibroblasts.
H. ducreyi
colocalized with collagen and fibrin but not laminin or fibronectin. Association with phagocytes, collagen, and fibrin was seen as early as 48 h and persisted at the pustular stage of disease. Optical sectioning by confocal microscopy and transmission electron microscopy both failed to demonstrate intracellular
H. ducreyi
. These data identify collagen and fibrin as potentially important targets of adherence in vivo and strongly suggest that
H. ducreyi
remains extracellular throughout infection and survives by resisting phagocytic killing in vivo.
Identification of the Exported Proteins of the Oral Opportunistic Pathogen
Actinobacillus actinomycetemcomitans
by Using Alkaline Phosphatase Fusions
Authors: Ward John , Fletcher Julie , Nair Sean P. , Wilson Michael , Williams Rachel J. , Poole Stephen , Henderson Brian 
Published: July 2002

ABSTRACT

A
phoA
fusion library of
Actinobacillus actinomycetemcomitans
genomic DNA has been screened to identify genes encoding exported and secreted proteins. A total of 8,000 colonies were screened, and 80 positive colonies were detected. From these, 48 genes were identified with (i) more than half having homology to known or hypothetical
Haemophilus influenzae
genes, (ii) 14 having no ascribed function, and (iii) 4 having very limited or no homology to known genes. The proteins encoded by these genes may, by virtue of their presence on the cell surface, be novel virulence determinants.
Complement Evasion byBorrelia burgdorferi: Serum-Resistant Strains Promote C3b Inactivation
Authors: Alitalo Antti , Meri Taru , Rämö Lasse , Jokiranta T. Sakari , Heikkilä Tero , Seppälä Ilkka J. T. , Oksi Jarmo , Viljanen Matti , Meri Seppo 
Published: July 2002

ABSTRACTThe most characteristic features of the Lyme disease pathogens, theBorrelia burgdorferisensu lato (s.l.) group, are their ability to invade tissues and to circumvent the immune defenses of the host for extended periods of time, despite elevated levels of borrelia-specific antibodies in serum and other body fluids. Our aim in the present study was to determine whetherB. burgdorferiis able to interfere with complement (C) at the level of C3 by accelerating C3b inactivation and thus to inhibit the amplification of the C cascade. Strains belonging to different genospecies (Borrelia garinii,B. burgdorferisensu stricto, andBorrelia afzelii) were compared for their sensitivities to normal human serum and abilities to promote factor I-mediated C3b degradation.B. burgdorferisensu stricto andB. afzeliistrains were found to be serum resistant. When the spirochetes were incubated with radiolabeled C3b, factor I-mediated degradation of C3b was observed in the presence of C-resistantB. afzelii(n= 3) andB. burgdorferisensu stricto (n= 1) strains but not in the presence of C-sensitiveB. garinii(n= 7) strains or control bacteria (Escherichia coli,Staphylococcus aureus,andEnterococcus faecalis). Immunoblotting and radioligand binding analyses showed that the C-resistant strains had the capacity to acquire the C inhibitors factor H and factor H-like protein 1 (FHL-1) from growth medium and human serum. A novel surface protein with an apparent molecular mass of 35 kDa was found to preferentially bind to the N terminus region of factor H. Thus, the serum-resistantB. burgdorferis.l. strains can circumvent C attack by binding the C inhibitors factor H and FHL-1 to their surfaces and promoting factor I-mediated C3b degradation.
Cloning, Overexpression, Purification, and Immunobiology of an 85-Kilodalton Outer Membrane Protein fromHaemophilus ducreyi
Authors: Thomas Kevin L. , Leduc Isabelle , Olsen Bonnie , Thomas Christopher E. , Cameron D. William , Elkins Christopher 
Published: July 2002

ABSTRACTWe have identified an 85-kDa outer membrane protein that is expressed by all tested strains ofHaemophilus ducreyi. Studies of related proteins from other pathogenic bacteria, includingHaemophilus influenzae, Pasteurella multocida, Neisseria gonorrhoeae, Neisseria meningitidis, andShigella dysenteriae, suggested a role for these proteins in pathogenesis and immunity. In keeping with the first such described protein fromHaemophilus influenzaetype B, we termed theH. ducreyiprotein D15. The gene encoding theH. ducreyiD15 protein was cloned and sequenced, and the deduced amino acid sequence was found to be most similar to sequences of the D15-related proteins from otherPasteurellaspp. The arrangement of the flanking genes was similar to that ofH. influenzaeRd and suggested that D15 was part of a multigene operon. Attempts to make a null mutation of the D15 gene were unsuccessful, paralleling results in other D15 gene studies. Overexpression ofH. ducreyiD15 inEscherichia coliresulted in a source of recombinant D15 (rD15) from which it was readily purified. rD15 was immunogenic, and it was found that immunization of rabbits with an rD15 vaccine preparation conferred partial protection against a virulent challenge infection. Antisera to an N-terminal peptide recognized all tested strains ofH. ducreyi.
Dr Operon-Associated Invasiveness of
Escherichia coli
from Pregnant Patients with Pyelonephritis
Authors: Goluszko Pawel , Niesel David , Nowicki Bogdan , Selvarangan Rangaraj , Nowicki Stella , Hart Audrey , Pawelczyk Edyta , Das Margaret , Urvil Petri , Hasan Rafia 
Published: July 2002

ABSTRACT

We used a gentamicin protection assay to assess the ability of gestational pyelonephritis isolates of
Escherichia coli
to invade HeLa cells. The ability to enter HeLa cells was strongly associated with the presence of Dr operons coding for Dr adhesins. In contrast, the nonivasive isolates predominantly expressed
papG
, coding for P fimbriae.
Escherichia coliEnterotoxin B Subunit Triggers Apoptosis of CD8+T Cells by Activating Transcription Factor c-Myc
Authors: Soriani Marco , Williams Neil A. , Hirst Timothy R. 
Published: July 2002

ABSTRACTHeat-labile enterotoxin from enterotoxinogenicEscherichia coliis not only an important cause of diarrhea in humans and domestic animals but also possesses potent immunomodulatory properties. Recently, the nontoxic, receptor-binding B subunit of heat-labile enterotoxin (EtxB) was found to induce the selective death of CD8+T cells, suggesting that EtxB may trigger activation of proapoptotic signaling pathways. Here we show that EtxB treatment of CD8+T cells but not of CD4+T cells triggers the specific up-regulation of the transcription factorc-myc, implicated in the control of cell proliferation, differentiation, and death. A concomitant elevation in Myc protein levels was also evident, with peak expression occurring 4 h posttreatment. Preincubation with c-mycantisense oligodeoxynucleotides demonstrated that Myc expression was necessary for EtxB-mediated apoptosis. Myc activation was also associated with an increase of IκBα turnover, suggesting that elevated Myc expression may be dependent on NF-κB. When CD8+T cells were pretreated with inhibitors of IκBα turnover and NF-κB translocation, this resulted in a marked reduction in both EtxB-induced apoptosis and Myc expression. Further, a non-receptor-binding mutant of EtxB, EtxB(G33D), was shown to lack the capacity to activate Myc transcription. These findings provide further evidence that EtxB is a signaling molecule that triggers activation of transcription factors involved in cell survival.
Coupled Phase-Variable Expression and Epitope Masking of Selective Surface Lipoproteins Increase Surface Phenotypic Diversity in
Mycoplasma hominis
Authors: Zhang Qijing , Wise Kim S. 
Published: July 2002

ABSTRACT

A new mechanism expanding mycoplasmal surface diversity is described. Exposure of surface epitopes on a constitutively expressed membrane protein (P56) of
Mycoplasma hominis
was subject to high-frequency phase variation due to phase-variable expression of the P120 antigen and its selective masking of P56 epitopes. Phase-variable masking may confer previously unrealized adaptive capabilities on mycoplasmas.
Borrelia burgdorferi
RevA Antigen Is a Surface-Exposed Outer Membrane Protein Whose Expression Is Regulated in Response to Environmental Temperature and pH
Authors: Carroll James A. , El-Hage Nazira , Miller Jennifer C. , Babb Kelly , Stevenson Brian 
Published: July 2002

ABSTRACT

Borrelia burgdorferi
, the causative agent of Lyme disease, produces RevA protein during the early stages of mammalian infection.
B. burgdorferi
apparently uses temperature as a cue to its location, producing proteins required for infection of warm-blooded animals at temperatures corresponding to host body temperature, but does not produce such virulence factors at cooler, ambient temperatures. We have observed that
B. burgdorferi
regulates expression of RevA in response to temperature, with the protein being synthesized by bacteria cultivated at 34°C but not by those grown at 23°C. Tissues encountered by
B. burgdorferi
during its infectious cycle vary in their pH values, and the level of RevA expression was also found to be dependent upon pH of the culture medium. The cellular localization of RevA was also analyzed. Borrelial inner and outer membranes were purified by isopycnic centrifugation, and membrane fractions were conclusively identified by immunoblot analysis using antibodies raised against the integral inner membrane protein MotB and outer membrane-associated Erp lipoproteins. Immunoblot analyses indicated that RevA is located in the
B. burgdorferi
outer membrane. These analyses also demonstrated that an earlier report (H. A. Bledsoe et al., Infect. Immun. 176:7447–7455, 1994) had misidentified such
B. burgdorferi
membrane fractions. RevA was further demonstrated to be exposed to the external environment, where it could facilitate interactions with host tissues.
Growth Phase Influences Complement Resistance ofBordetella pertussis
Authors: Barnes Michael G. , Weiss Alison A. 
Published: July 2002

ABSTRACTThe BrkA protein ofBordetella pertussisinhibits killing by the antibody-dependent classical pathway of complement; however, susceptibility to complement can be highly variable. Log-phase bacteria grown in Stainer-Scholte (SS) broth plated on Bordet-Gengou (BG) agar were about 500 times more sensitive to killing by complement than stationary-phase SS-BG cultures. While always more susceptible to complement than the wild-type strain, a BrkA mutant displayed a similar growth phase variation in susceptibility to complement. Growth phase susceptibility to complement was also observed for a mutant constitutive for Bvg activation of BrkA, suggesting that modulation of virulence factor expression was not responsible for sensitivity to complement. Susceptibility was not due to differential antigenic expression, since serum adsorbed with complement-resistant, stationary-phase SS-BG cultures lacked bactericidal activity againstB. pertussisharvested at all times during the growth cycle. These results suggest that log-phase susceptibility to complement is not due to variable expression of BrkA or antigenic differences and may be an inherent property of rapidly growing cultures. Implications for vaccine development are discussed.
Identification and Characterization of a Nonimmunoglobulin Factor in Human Saliva That Inhibits
Streptococcus mutans
Glucosyltransferase
Authors: Jespersgaard Christina , Hajishengallis George , Russell Michael W. , Michalek Suzanne M. 
Published: July 2002

ABSTRACT

Saliva contains an array of nonimmunoglobulin defense factors which are thought to contribute to the protection of the hard and soft tissue surfaces of the oral cavity by modulating microbial colonization and metabolism. Here we report the discovery of a putative innate defense factor in human saliva that inhibits the glucosyltransferase (GTF) of
Streptococcus mutans
, a virulence enzyme involved in oral colonization by this pathogen. The GTF-inhibiting factor (GIF) was initially identified as a nonimmunoglobulin salivary component that interfered with detection of antibodies to the glucan-binding region (GLU) of GTF by an enzyme-linked immunosorbent assay. This inhibitory activity was present in whole saliva and submandibular-sublingual saliva, but it was essentially absent from parotid saliva. GIF inhibited the recognition of
S. mutans
cell surface-associated GTF by specific antibodies but had no effect on antibodies to other cell surface antigens, suggesting that GIF specifically binds to GTF on
S. mutans.
GIF purified by size exclusion or affinity chromatography was used for biochemical and functional characterization. Analysis of GIF by sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed a high-molecular-weight glycoprotein after staining with Coomassie blue or Schiff's reagent. Heating and reduction with 2-mercaptoethanol of GIF resulted in the release of a ∼58-kDa protein that was identified as α-amylase by Western blotting using anti-α-amylase antibodies. GLU bound blotted α-amylase, suggesting that the latter molecule is the GLU-binding component of the GIF complex. The ability of GTF to synthesize extracellular glucans was inhibited by GIF but not by uncomplexed α-amylase or an unrelated high-molecular-weight glycoprotein. In conclusion, our findings demonstrate that in human saliva, there is a high-molecular-weight glycoprotein-α-amylase complex which is capable of inhibiting GTF and may contribute to control of
S. mutans
colonization in the oral cavity.
Fibronectin FacilitatesMycobacterium tuberculosisAttachment to Murine Alveolar Macrophages
Authors: Pasula Rajamouli , Wisniowski Paul , Martin William J. 
Published: July 2002

ABSTRACTMycobacterium tuberculosisremains a major cause of pulmonary infection worldwide. Attachment ofM. tuberculosisorganisms to alveolar macrophages (AMs) represents the earliest phase of primary infection in pulmonary tuberculosis. In this study fibronectin (Fn), an adhesive protein, is shown to bindM. tuberculosisorganisms and facilitates attachment ofM. tuberculosisto murine AMs. A monoclonal antibody (MAb) specific to the heparin binding domain (HBD) of Fn decreases125I-Fn binding toM. tuberculosis; whereas MAbs specific to either the cell binding domain (CBD) or the gelatin binding domain (GBD) have no effect on Fn binding toM. tuberculosis. In the presence of exogenous Fn (10 μg/ml)M. tuberculosisattachment to AMs increased significantly from control levels (means ± standard errors of the means) of 11.5% ± 1.1% to 44.2% ± 4.2% (P< 0.05). Fn-enhanced attachment was significantly decreased from 44.2% ± 4.2% to 10.8% ± 1.2% (P< 0.05) in the presence of anti-Fn polyclonal antibodies. The attachment is also inhibited in the presence of MAbs specific for the HBD and CBD, whereas MAbs specific to GBD did not affect the attachment. Further, an Fn cell binding peptide, Arg-Gly-Asp-Ser (RGDS), decreased the attachment from 44.2% ± 4.2% to 15.3% ± 1.2% (P< 0.05), whereas addition of a control peptide, Arg-Gly-Glu-Ser (RGES) did not affect the attachment (40.5% ± 1.8%). These results suggest that Fn-mediated attachment ofM. tuberculosiscan occur through the binding of Fn to the AM via the CBD and toM. tuberculosisorganisms via the HBD.
Transmission Intensity Affects Both Antigen-Specific and Nonspecific T-Cell Proliferative Responses inLoa loaInfection
Authors: Akue Jean Paul , Devaney Eileen 
Published: July 2002

ABSTRACTT-cell proliferative responses were studied in two villages in Gabon with different levels ofLoa loatransmission. The first village (Okoumbi) had an annual transmission potential (ATP) of ≈9,000 infective larvae (L3)/person/year (high transmission village), while the second village (Ndjokaye) had an ATP of ≈1,000 L3/person/year (low transmission village). Proliferation and cytokine assays were performed on peripheral blood mononuclear cells (PBMC) from individuals aged 18 years and over using either mitogens (concanavalin A or phytohemagglutinin), antigens (purified protein derivative [PPD], irrelevant antigen), or soluble extracts of L3, microfilariae, or adultL. loa. PBMC from individuals in the low transmission village responded better to stimulation with adult antigen and to PPD than did PBMC from individuals in the high transmission village (P= 0.0031 andP= 0.0012, respectively). These data suggest that high levels of transmission ofL. loadepress both specific and nonspecific T-cell proliferative responses in infected humans.
Disruption of the
Candida albicans TPS2
Gene Encoding Trehalose-6-Phosphate Phosphatase Decreases Infectivity without Affecting Hypha Formation
Authors: Van Dijck Patrick , De Rop Larissa , Szlufcik Karolina , Van Ael Elke , Thevelein Johan M. 
Published: July 2002

ABSTRACT

Deletion of trehalose-6-phosphate phosphatase, encoded by
TPS2
, in
Saccharomyces cerevisiae
results in accumulation of trehalose-6-phosphate (Tre6P) instead of trehalose under stress conditions. Since trehalose is an important stress protectant and Tre6P accumulation is toxic, we have investigated whether Tre6P phosphatase could be a useful target for antifungals in
Candida albicans
. We have cloned the
C. albicans TPS2
(
CaTPS2
) gene and constructed heterozygous and homozygous deletion strains. As in
S. cerevisiae
, complete inactivation of Tre6P phosphatase in
C. albicans
results in 50-fold hyperaccumulation of Tre6P, thermosensitivity, and rapid death of the cells after a few hours at 44°C. As opposed to inactivation of Tre6P synthase by deletion of
CaTPS1
, deletion of
CaTPS2
does not affect hypha formation on a solid glucose-containing medium. In spite of this, virulence of the homozygous deletion mutant is strongly reduced in a mouse model of systemic infection. The pathogenicity of the heterozygous deletion mutant is similar to that of the wild-type strain.
CaTPS2
is a new example of a gene not required for growth under standard conditions but required for pathogenicity in a host. Our results suggest that Tre6P phosphatase may serve as a potential target for antifungal drugs. Neither Tre6P phosphatase nor its substrate is present in mammals, and assay of the enzymes is simple and easily automated for high-throughput screening.
Purification and Characterization of Arginine Carboxypeptidase Produced by
Porphyromonas gingivalis
Authors: Masuda Kaname , Yoshioka Masami , Hinode Daisuke , Nakamura Ryo 
Published: July 2002

ABSTRACT

Arginine carboxypeptidase was isolated from the cytoplasm of
Porphyromonas gingivalis
381 and purified by DEAE-Sephacel column chromatography, followed by high-performance liquid chromatography on DEAE-5PW and TSK G2000SW
XL
. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the purified enzyme revealed the presence of three major bands at 42, 33, and 32 kDa with identical N-terminal sequences. By Western blotting analysis and immunoelectron microscopy, the arginine carboxypeptidase was found to be widely distributed in the cytoplasm and on the surface of the outer membrane. The open reading frame corresponding to the N-terminal amino acids of the arginine carboxypeptidase was detected by a search of the sequence of the
P. gingivalis
W83 genome. This sequence showed homology with mammalian carboxypeptidases (M, N, and E/H) and included a zinc-binding region signature, suggesting that the enzyme is a member of the zinc carboxypeptidase family. The purified enzyme was inhibited by EGTA,
o
-phenanthroline,
dl
-2-mercaptomethyl-3-guanidinoethylthiopropanoic acid, and some metal ions, such as Cu
2+
, Zn
2+
, and Cd
2+
. On the other hand, Co
2+
activated the enzyme. The enzyme released arginine and/or lysine from biologically active peptides containing these amino acids at the C terminus but did not cleave substrates when proline was present at the penultimate position. These results indicate that the arginine carboxypeptidase produced by
P. gingivalis
is an exo type of metallocarboxypeptidase. This enzyme may function to release arginine in collaboration with an arginine aminopeptidase, e.g., Arg-gingipain, to obtain specific amino acids from host tissues during the growth of
P. gingivalis
.