bluuebunny/crossref_metadata_2025_split huggingface dataset:
Streptococcal Erythrogenic Toxin B Abrogates Fibronectin-Dependent Internalization of
Streptococcus pyogenes
by Cultured Mammalian Cells
Authors: Chaussee Michael S. , Cole Robert L. , van Putten Jos P. M. 
Published: July 2002

ABSTRACT

Streptococcus pyogenes
secretes several proteins that influence host-pathogen interactions. A tissue-culture model was used to study the influence of the secreted cysteine protease streptococcal erythrogenic toxin B (SPE B) on the interaction between
S. pyogenes
strain NZ131 (serotype M49) and mammalian cells. Inactivation of the
speB
gene enhanced fibronectin-dependent uptake of the pathogen by Chinese hamster ovary (CHO-K1) cells compared to that in the isogenic wild-type strain. Preincubation of the NZ131
speB
mutant with purified SPE B protease significantly inhibited fibronectin-dependent uptake by both CHO-K1 and CHO-
pgs
745 cells. The effect was attributed to an abrogation of fibronectin binding to the surface of the bacteria that did not involve either the M49 protein or the streptococcal fibronectin-binding protein SfbI. In contrast, pretreatment of the NZ131
speB
mutant with SPE B did not influence sulfated polysaccharide-mediated uptake by CHO-
pgs
745 cells. The results indicate that the SPE B protease specifically alters bacterial cell surface proteins and thereby influences pathogen uptake.
The Relapsing Fever Spirochete
Borrelia hermsii
Contains Multiple, Antigen-Encoding Circular Plasmids That Are Homologous to the cp32 Plasmids of Lyme Disease Spirochetes
Authors: Stevenson Brian , Porcella Stephen F. , Oie Katrina L. , Fitzpatrick Cecily A. , Raffel Sandra J. , Lubke Lori , Schrumpf Merry E. , Schwan Tom G. 
Published: July 2002

ABSTRACT

Borrelia hermsii
, an agent of tick-borne relapsing fever, was found to contain multiple circular plasmids approximately 30 kb in size. Sequencing of a DNA library constructed from circular plasmid fragments enabled assembly of a composite DNA sequence that is homologous to the cp32 plasmid family of the Lyme disease spirochete,
B. burgdorferi
. Analysis of another relapsing fever bacterium,
B. parkeri
, indicated that it contains linear homologs of the
B. hermsii
and
B. burgdorferi
cp32 plasmids. The
B. hermsii
cp32 plasmids encode homologs of the
B. burgdorferi
Mlp and Bdr antigenic proteins and BlyA/BlyB putative hemolysins, but homologs of
B. burgdorferi erp
genes were absent. Immunoblot analyses demonstrated that relapsing fever patients produced antibodies to Mlp proteins, indicating that those proteins are synthesized by the spirochetes during human infection. Conservation of cp32-encoded genes in different
Borrelia
species suggests that their protein products serve functions essential to both relapsing fever and Lyme disease spirochetes. Relapsing fever borreliae replicate to high levels in the blood of infected animals, permitting direct detection and possible functional studies of Mlp, Bdr, BlyA/BlyB, and other cp32-encoded proteins in vivo.
Allelic Diversity of the Two Transferrin Binding Protein B Gene Isotypes among a Collection of
Neisseria meningitidis
Strains Representative of Serogroup B Disease: Implication for the Composition of a Recombinant TbpB-Based Vaccine
Authors: Rokbi Bachra , Renauld-Mongenie Geneviève , Mignon Michèle , Danve B. , Poncet David , Chabanel Christophe , Caugant Dominique A. , Quentin-Millet Marie-José 
Published: July 2002

ABSTRACT

The distribution of the two isotypes of
tbpB
in a collection of 108 serogroup B meningococcal strains belonging to the four major clonal groups associated with epidemic and hyperendemic disease (the ET-37 complex, the ET-5 complex, lineage III, and cluster A4) was determined. Isotype I strains (with a 1.8-kb
tbpB
gene) was less represented than isotype II strains (19.4 versus 80.6%). Isotype I was restricted to the ET-37 complex strains, while isotype II was found in all four clonal complexes. The extent of the allelic diversity of
tbpB
in these two groups was studied by PCR restriction analysis and sequencing of 10 new
tbpB
genes. Four major
tbpB
gene variants were characterized: B16B6 (representative of isotype I) and M982, BZ83, and 8680 (representative of isotype II). The relevance of these variants was assessed at the antigenic level by the determination of cross-bactericidal activity of purified immunoglobulin G preparations raised to the corresponding recombinant TbpB (rTbpB) protein against a panel of 27 strains (5 of isotype I and 22 of isotype II). The results indicated that rTbpB corresponding to each variant was able to induce cross-bactericidal antibodies. However, the number of strains killed with an anti-rTbpB serum was slightly lower than that obtained with an anti-TbpA
+
B complex. None of the sera tested raised against an isotype I strain was able to kill an isotype II strain and vice versa. None of the specific antisera tested (anti-rTbpB or anti-TbpA
+
B complex) was able to kill all of the 22 isotype II strains tested. Moreover, using sera raised against the C-terminus domain of TbpB M982 (amino acids 352 to 691) or BZ83 (amino acids 329 to 669) fused to the maltose-binding protein, cross-bactericidal activity was detected against 12 and 7 isotype II strains, respectively, of the 22 tested. These results suggest surface accessibility of the C-terminal end of TbpB. Altogether, these results show that although more than one rTbpB will be required in the composition of a TbpB-based vaccine to achieve a fully cross-bactericidal activity, rTbpB and its C terminus were able by themselves to induce cross-bactericidal antibodies.
Fecal Antibodies toCryptosporidium parvumin Healthy Volunteers
Authors: Dann Sara M. , Okhuysen Pablo C. , Salameh Bassam M. , DuPont Herbert L. , Chappell Cynthia L. 
Published: July 2002

ABSTRACTThis study examined the intestinal antibody response in 26 healthy volunteers challenged withCryptosporidium parvumoocysts. Fecal extracts were assayed for total secretory immunoglobulin A (IgA) andC. parvum-specific IgA reactivity. Specific IgA reactivity was standardized to IgA concentration and expressed as a reactivity index (RI). Anti-C. parvumfecal IgA (fIgA) increased significantly in 17 of 26 (65.4%) following oocyst ingestion. Of those with detectable responses, 59, 76.5, and 94.1% were positive by days 7, 14, and 30, respectively. Volunteers receiving high challenge doses (>1,000 and 300 to 500 oocysts) had higher RIs (RI = 5.57 [P= 0.027] and RI = 1.68 [P= 0.039], respectively) than those ingesting low doses (30 to 100 oocysts; RI = 0.146). Subjects shedding oocysts and experiencing a diarrheal illness had the highest fIgA reactivity. When evaluated separately, oocyst excretion was associated with an increased fIgA response compared to nonshedders (RI = 1.679 versus 0.024, respectively;P= 0.003). However, in subjects experiencing diarrhea with or without oocyst shedding, a trend toward a higher RI (P= 0.065) was seen. Extracts positive for fecal IgA were further examined for IgA subclass. The majority of stools contained both IgA1 and IgA2, and the relative proportions did not change following challenge. Also, noC. parvum-specific IgM or IgG was detected in fecal extracts. Thus, fecal IgA toC. parvumantigens was highly associated with infection in subjects who had no evidence of previous exposure and may provide a useful tool in detecting recent infections.
Induction of Colony-Stimulating Factor Expression followingStaphylococcusorSalmonellaInteraction with Mouse or Human Osteoblasts
Authors: Bost Kenneth L. , Bento Jennifer L. , Ellington John K. , Marriott Ian , Hudson Michael C. 
Published: July 2002

ABSTRACTStaphylococcus aureusandSalmonellaspp. are common causes of bone diseases; however, the immune response during such infections is not well understood. Colony-stimulating factors (CSF) have a profound influence on osteoclastogenesis, as well as the development of immune responses following infection. Therefore, we questioned whether interaction of osteoblasts with two very different bacterial pathogens could affect CSF expression by these cells. Cultured mouse and human osteoblasts were exposed to various numbers ofS. aureusorSalmonella dublinbacteria, and a comprehensive analysis of granulocyte-macrophage (GM)-CSF, granulocyte (G)-CSF, macrophage (M)-CSF, and interleukin-3 (IL-3) mRNA expression and cytokine secretion was performed. Expression of M-CSF and IL-3 mRNAs by mouse osteoblasts was constitutive and did not increase significantly following bacterial exposure. In contrast, GM-CSF and G-CSF mRNA expression by mouse osteoblasts was dramatically upregulated following interaction with either viableS. aureusorSalmonella. This increased mRNA expression also translated into high levels of GM-CSF and G-CSF secretion by mouse and human osteoblasts following bacterial exposure. ViableS. aureusandSalmonellainduced maximal levels of CSF mRNA expression and cytokine secretion compared to UV-killed bacteria. Furthermore, GM-CSF and G-CSF mRNA expression could be induced in unexposed osteoblasts separated by a permeable Transwell membrane from bacterially exposed osteoblasts. M-CSF secretion was increased in cultures of exposed human osteoblasts but not in exposed mouse osteoblast cultures. Together, these studies are the first to define CSF expression and suggest that, following bacterial exposure, osteoblasts may influence osteoclastogenesis, as well as the development of an immune response, via the production of these cytokines.
Uptake and Killing of
Leptospira interrogans
and
Borrelia burgdorferi
, Spirochetes Pathogenic to Humans, by Reticuloendothelial Cells in Perfused Rat Liver
Authors: Marangoni Antonella , Aldini Rita , Sambri Vittorio , Montagnani Marco , Ballardini Giorgio , Storni Elisa , Cevenini Roberto 
Published: July 2002

ABSTRACT

In situ-perfused rat livers were infused with a single dose of 1.5 × 10
7
radiolabeled cells of
Leptospira interrogans
serovar icterohaemorrhagiae, the agent of leptospirosis, or with
Borrelia burgdorferi
IRS, the agent of Lyme disease. Significant (
P
< 0.0001) differences in the liver uptake of
L. interrogans
and of
B. burgdorferi
were observed, the uptakes being 37.4% ± 2.3% for
L. interrogans
and 60.5% ± 3.1% for
B. burgdorferi
. Leptospires, in contrast to borreliae, were recovered from the livers when liver samples were cultured in growth medium. Leptospires but not borreliae were recovered in bile within 30 min of infusion. The association of leptospires and borreliae with reticuloendothelial cells of the liver was demonstrated by immunohistochemistry. Leptospires and borreliae were found to be associated with vimentin-positive cells and not with desmin-positive cells. Few leptospires but no borreliae were also seen associated with vimentin- and desmin-negative cells, suggesting the presence of leptospires outside the sinusoidal spaces, in the liver parenchyma.
Mapping of Binding Domains of Nontypeable
Haemophilus influenzae
HMW1 and HMW2 Adhesins
Authors: Dawid Suzanne , Grass Susan , St. Geme Joseph W. 
Published: July 2002

ABSTRACT

Nontypeable
Haemophilus influenzae
is an important cause of localized respiratory tract disease, which begins with colonization of the upper respiratory mucosa. In previous work we reported that the nontypeable
H. influenzae
HMW1 and HMW2 proteins are high-molecular-weight nonpilus adhesins responsible for attachment to human epithelial cells, an essential step in the process of colonization. Interestingly, although HMW1 and HMW2 share significant sequence similarity, they display distinct cellular binding specificities. In order to map the HMW1 and HMW2 binding domains, we generated a series of complementary HMW1-HMW2 chimeric proteins and examined the ability of these proteins to promote in vitro adherence by
Escherichia coli
DH5α. Using this approach, we localized the HMW1 and HMW2 binding domains to an ∼360-amino-acid region near the N terminus of the mature HMW1 and HMW2 proteins. Experiments with maltose-binding protein fusion proteins containing segments of either HMW1 or HMW2 confirmed these results and suggested that the fully functional binding domains may be conformational structures that require relatively long stretches of sequence. Of note, the HMW1 and HMW2 binding domains correspond to areas of maximal sequence dissimilarity, suggesting that selective advantage associated with broader adhesive potential has been a major driving force during
H. influenzae
evolution. These findings should facilitate efforts to develop a subcomponent vaccine effective against nontypeable
H. influenzae
disease.
Comparison of CXC Chemokines ENA-78 and Interleukin-8 Expression inHelicobacter pylori-Associated Gastritis
Authors: Rieder Gabriele , Einsiedl Wolfgang , Hatz Rudolf A. , Stolte Manfred , Enders Georg A. , Walz Alfred 
Published: July 2002

ABSTRACTColonization of the gastric mucosa withHelicobacter pyloriis associated with a dense infiltration of granulocytes into the lamina propria in the active phase of gastritis. In this study, we investigated the involvement of epithelial cell-derived neutrophil-activating protein 78 (ENA-78) in development ofH. pylori-associated gastritis. Antral biopsies from 27 patients withH. pylori-associated gastritis and 25 fromH. pylori-negative individuals were first analyzed for ENA-78 and interleukin-8 (IL-8) mRNA by semiquantitative reverse transcription (RT)-PCR. InH. pylori-positive patients, significantly elevated levels were found for both chemokines (P< 0.05). Only IL-8 mRNA levels differed significantly (P< 0.05) inH. pylori-infected individuals who had serum antibodies for cytotoxin-associated protein CagA versusH. pylori-infected CagA-negative persons. Quantification of ENA-78 transcript levels by competitive RT-PCR yielded a significant 45-fold upregulation for ENA-78 transcripts in biopsies ofH. pylori-positive versusH. pylori-negative patients (P< 0.05). In contrast to earlier findings with IL-8, the degree of ENA-78 mRNA upregulation was independent of the grade of activity of gastritis. Immunofluorescence studies on tissues of antral biopsies localized ENA-78 protein expression mainly to the gastric epithelium ofH. pylori-positive patients, while control tissues were negative. Upregulation of ENA-78 and IL-8 mRNA and protein expression was also observed in an in vitro system using a gastric adenocarcinoma cell line. Only viableH. pyloriyielded a strong ENA-78 and IL-8 induction, whileH. pyloriouter membrane proteins or water-soluble proteins had no significant effect. These data provide evidence for the importance of both IL-8 and ENA-78 in the development and perpetuation ofH. pylori-associated gastritis.
Population Dynamics of
Streptococcus mitis
in Its Natural Habitat
Authors: Hohwy Jesper , Reinholdt Jesper , Kilian Mogens 
Published: July 2002

ABSTRACT

The purpose of this study was to examine the genetic structure of the typical commensal
Streptococcus mitis
biovar 1 in its natural habitat in the human oral cavity and pharynx and to investigate the role that selected microbial properties and host, spatial, and temporal factors play in determining the structure of the bacterial population. Consecutive samples were collected from buccal and pharyngeal mucosal surfaces of two infants, their four parents, and two elderly individuals over a period of approximately 1 year. A total of 751 isolates identified as
S. mitis
biovar 1 were typed by restriction endonuclease analysis (REA) and representative clones were typed by multilocus enzyme electrophoresis (MLEE). The genetic diversity of the
S. mitis
biovar 1 isolates collected from single infant hosts over a period of 9 to 10 months was found to be between 0.69 and 0.76, which is considerably higher than that previously observed for intestinal populations of
Escherichia coli
. The study provides evidence of the existence of both transient and persistent clones in adult individuals. In the two infants, however, none of 42 demonstrated clones were detected on more than a single occasion. Statistical calculations showed that the ability to persist was not distributed at random in the
S. mitis
biovar 1 population. However, neither immunoglobulin A1 protease activity nor the ability to bind α-amylase from saliva was a preferential characteristic of persistent genotypes. In contrast to current concepts of climax ecosystems, the species niche in the habitat appears to be maintained predominantly by a succession of clones rather than by stable strains. Several lines of evidence suggest that the major origin of “new” clones is the many other habitats in the respiratory tract that are occupied by this species.
Epidemic Population Structure of
Pseudomonas aeruginosa
: Evidence for a Clone That Is Pathogenic to the Eye and That Has a Distinct Combination of Virulence Factors
Authors: Lomholt Jeanet A. , Poulsen Knud , Kilian Mogens 
Published: July 2002

ABSTRACT

The genetic structure of a population of
Pseudomonas aeruginosa
, isolated from patients with keratitis, endophthalmitis, and contact lens-associated red eye, contact lens storage cases, urine, ear, blood, lungs, wounds, feces, and the environment was determined by multilocus enzyme electrophoresis. The presence and characteristics of virulence factors were determined by restriction fragment length polymorphism analysis with DNA probes for
lasA
,
lasB
,
aprA
,
exoS
,
exoT
,
exoU
, and
ctx
and by zymography of staphylolysin, elastase, and alkaline protease. These analyses revealed an epidemic population structure of
P. aeruginosa
, characterized by frequent recombination in which a particular successful clone may increase, predominate for a time, and then disasappear as a result of recombination. Epidemic clones were found among isolates from patients with keratitis. They were characterized by high activity of a hitherto-unrecognized size variant of elastase, high alkaline protease activity, and possession of the
exoU
gene encoding the cytotoxic exoenzyme U. These virulence determinants are not exclusive traits in strains causing keratitis, as strains with other properties may cause keratitis in the presence of predisposing conditions. There were no uniform patterns of characteristics of isolates from other types of infection; however, all strains from urinary tract infections possessed the
exoS
gene, all strains from environment and feces and the major part of keratitis and wound isolates exhibited high elastase and alkaline protease activity, and all strains from feces showed high staphylolysin activity, indicating that these virulence factors may be important in the pathogenesis of these infectious diseases.
Reassessing the Role of
Staphylococcus aureus
Clumping Factor and Fibronectin-Binding Protein by Expression in
Lactococcus lactis
Authors: Que Yok-Ai , François Patrice , Haefliger Jacques-Antoine , Entenza José-Manuel , Vaudaux Pierre , Moreillon Philippe 
Published: July 2002

ABSTRACT

Since
Staphylococcus aureus
expresses multiple pathogenic factors, studying their individual roles in single-gene-knockout mutants is difficult. To circumvent this problem,
S. aureus
clumping factor A (
clfA
) and fibronectin-binding protein A (
fnbA
) genes were constitutively expressed in poorly pathogenic
Lactococcus lactis
using the recently described pOri23 vector. The recombinant organisms were tested in vitro for their adherence to immobilized fibrinogen and fibronectin and in vivo for their ability to infect rats with catheter-induced aortic vegetations. In vitro, both
clfA
and
fnbA
increased the adherence of lactococci to their specific ligands to a similar extent as the
S. aureus
gene donor. In vivo, the minimum inoculum size producing endocarditis in ≥80% of the rats (80% infective dose [ID
80
]) with the parent lactococcus was ≥10
7
CFU. In contrast,
clfA
-expressing and
fnbA
-expressing lactococci required only 10
5
CFU to infect the majority of the animals (
P
< 0.00005). This was comparable to the infectivities of classical endocarditis pathogens such as
S. aureus
and streptococci (ID
80
= 10
4
to 10
5
CFU) in this model. The results confirmed the role of
clfA
in endovascular infection, but with a much higher degree of confidence than with single-gene-inactivated staphylococci. Moreover, they identified
fnbA
as a critical virulence factor of equivalent importance. This was in contrast to previous studies that produced controversial results regarding this very determinant. Taken together, the present observations suggest that if antiadhesin therapy were to be developed, at least both of the
clfA
and
fnbA
products should be blocked for the therapy to be effective.
Vibrio cholerae-Induced Cellular Responses of Polarized T84 Intestinal Epithelial Cells Are Dependent on Production of Cholera Toxin and the RTX Toxin
Authors: Fullner Karla Jean , Lencer Wayne I. , Mekalanos John J. 
Published: July 2002

ABSTRACTTo study the utility of in vitro-polarized intestinal cell monolayers for modelingVibrio cholerae-host cell interactions, we added liveV. choleraebacteria to the apical surfaces of polarized T84 cell monolayers and monitored changes in electrical properties. We found that both classical and El Tor strains produce cholera toxin after addition to the monolayer, but induction is most likely due to medium components rather than bacterium-cell interactions. We also found that the RTX toxin is produced by El Tor strains. This toxin caused a loss of the barrier function of the paracellular tight junction that was measured as a decrease in transepithelial resistance. This decrease occurred when bacteria were added to either the apical or basolateral surfaces, indicating that the RTX toxin receptor is expressed on both surfaces. These results are discussed with regard to the applicability of the polarized T84 cell monolayers as an in vitro model of host-pathogen interactions.
Cloning, Nucleotide Sequence, and Expression of the
Brucella melitensis sucB
Gene Coding for an Immunogenic Dihydrolipoamide Succinyltransferase Homologous Protein
Authors: Zygmunt Michel S. , Dı́az Marı́a A. , Teixeira-Gomes Ana P. , Cloeckaert Axel 
Published: July 2002

ABSTRACT

The
Brucella melitensis sucB
gene encoding the dihydrolipoamide succinyltransferase (E2o) enzyme (previously identified as an immunogenic protein in infected sheep) was cloned and sequenced. The amino acid sequence predicted from the cloned gene revealed 88.8 and 51.2% identity to the dihydrolipoamide succinyltransferase SucB protein from
Brucella abortus
and
Escherichia coli
, respectively. Sera from naturally infected sheep showed antibody reactivity against the recombinant SucB protein.
Dual Role of Lipopolysaccharide (LPS)-Binding Protein in Neutralization of LPS and Enhancement of LPS-Induced Activation of Mononuclear Cells
Authors: Gutsmann Thomas , Müller Mareike , Carroll Stephen F. , MacKenzie Roger C. , Wiese Andre , Seydel Ulrich 
Published: July 2002

ABSTRACTThe lipopolysaccharide (LPS)-binding protein (LBP) has a concentration-dependent dual role in the pathogenesis of gram-negative sepsis: low concentrations of LBP enhance the LPS-induced activation of mononuclear cells (MNC), whereas the acute-phase rise in LBP concentrations inhibits LPS-induced cellular stimulation. In stimulation experiments, we have found that LBP mediates the LPS-induced cytokine release from MNC even under serum-free conditions. In biophysical experiments we demonstrated that LBP binds and intercalates into lipid membranes, amplified by negative charges of the latter, and that intercalated LBP can mediate the CD14-independent intercalation of LPS into membranes in a lipid-specific and temperature-dependent manner. In contrast, prior complexation of LBP and LPS inhibited binding of these complexes to membranes due to different binding of LBP to LPS or phospholipids. This results in a neutralization of LPS and, therefore, to a reduced production of tumor necrosis factor by MNC. We propose that LBP is not only present as a soluble protein in the serum but may also be incorporated as a transmembrane protein in the cytoplasmic membrane of MNC and that the interaction of LPS with membrane-associated LBP may be an important step in LBP-mediated activation of MNC, whereas LBP-LPS complexation in the serum leads to a neutralization of LPS.