bluuebunny/crossref_metadata_2025_split huggingface dataset:
Naturally Acquired Antibody Responses toPlasmodium falciparumMerozoite Surface Protein 4 in a Population Living in an Area of Endemicity in Vietnam
Authors: Wang Lina , Richie Thomas L. , Stowers Anthony , Nhan Doan Hanh , Coppel Ross L. 
Published: July 2002

ABSTRACTMerozoite surface protein 4 (MSP4) ofPlasmodium falciparumis a glycosylphosphatidylinositol-anchored integral membrane protein that is being developed as a component of a subunit vaccine against malaria. We report here the measurement of naturally acquired antibodies to MSP4 in a population of individuals living in the Khanh-Hoa region of Vietnam, an area where malaria is highly endemic. Antibodies to MSP4 were detected in 94% of the study population at titers of 1:5,000 or greater. Two forms of recombinant MSP4 produced in eitherEscherichia coliorSaccharomyces cerevisiaewere compared as substrates in the enzyme-linked immunosorbent assay. There was an excellent correlation between reactivity measured to either, although the yeast substrate was recognized by a higher percentage of sera. Four different regions of MSP4 were recognized by human antibodies, demonstrating that there are at least four distinct epitopes in this protein. In the carboxyl terminus, where the single epidermal growth factor-like domain is located, the reactive epitope(s) was shown to be conformation dependent, as disruption of the disulfide bonds almost completely abolished reactivity with human antibodies. The anti-MSP4 antibodies were mainly of the immunoglobulin G1 (IgG1) and IgG3 subclasses, suggesting that such antibodies may play a role in opsonization and complement-mediated lysis of free merozoites. Individuals in the study population were drug-cured and followed up for 6 months; no significant correlation was observed between the anti-MSP4 antibodies and the absence of parasitemia during the surveillance period. As a comparison, antibodies to MSP119, a leading vaccine candidate, were measured, and no correlation with protection was observed in these individuals. The anti-MSP119antibodies were predominantly of the IgG1 isotype, in contrast to the IgG3 predominance noted for MSP4.
Decreased Amounts of Cell Wall-Associated Protein A and Fibronectin-Binding Proteins in
Staphylococcus aureus sarA
Mutants due to Up-Regulation of Extracellular Proteases
Authors: Karlsson Anna , Saravia-Otten Patricia , Tegmark Karin , Morfeldt Eva , Arvidson Staffan 
Published: July 2002

ABSTRACT

Data have been presented indicating that
Staphylococcus aureus
cell surface protein can be degraded by extracellular proteases produced by the same bacterium. We have found that in
sarA
mutant cells, which produce high amounts of four major extracellular proteases (staphylococcal serine protease [V8 protease] [SspA], cysteine protease [SspB], aureolysin [metalloprotease] [Aur], and staphopain [Scp]), the levels of cell-bound fibronectin-binding proteins (FnBPs) and protein A were very low compared to those of wild-type cells, in spite of unaltered or increased transcription of the corresponding genes. Cultivation of
sarA
mutant cells in the presence of the global protease inhibitor α
2
-macroglobulin resulted in a 16-fold increase in cell-bound FnBPs, indicating that extracellular proteases were responsible for the decreased amounts of FnBPs in
sarA
mutant cells. The protease inhibitor E64 had no effect on the level of FnBPs, indicating that cysteine proteases were not involved. Inactivation of either
ssp
or
aur
in the prototype
S. aureus
strain 8325-4 resulted in a threefold increase in the amount of cell-bound FnBPs. Inactivation of the same protease genes in a
sarA
mutant of 8325-4 resulted in a 10- to 20-fold increase in cell-bound protein A. As the serine protease requires aureolysin to be activated, it can thus be concluded that the serine protease is the most important protease in the release of cell-bound FnBPs and protein A.
Diversity in Antistaphylococcal Mechanisms among Membrane-Targeting Antimicrobial Peptides
Authors: Koo Su-Pin , Bayer Arnold S. , Yeaman Michael R. 
Published: July 2002

ABSTRACT

Many antimicrobial peptides permeabilize the bacterial cytoplasmic membrane. However, it is unclear how membrane permeabilization and antimicrobial activity are related for distinct peptides. This study investigated the relationship between
Staphylococcus aureus
membrane permeabilization and cell death due to the following antistaphylococcal peptides: thrombin-induced platelet microbicidal protein 1 (tPMP-1), gramicidin D, and protamine. Isogenic
S. aureus
strains ISP479C and ISP479R (tPMP-1 susceptible and resistant, respectively), were loaded with the fluorochrome calcein and exposed to a range of concentrations of each peptide. Flow cytometry was then used to monitor membrane permeabilization by quantifying the release of preloaded calcein. Killing was determined by quantitative culture at time points simultaneous to measurement of membrane permeabilization. Membrane permeabilization and killing caused by tPMP-1 occurred in a time- and concentration-dependent manner, reflecting the intrinsic tPMP-1 susceptibilities of ISP479C and ISP479R. In comparison, gramicidin D killed both
S. aureus
strains to equivalent extents in a concentration-dependent manner between 0.5 to 50 μg/ml, but cell permeabilization only occurred at the higher peptide concentrations (25 and 50 μg/ml). Protamine permeabilized, but did not kill, either strain at concentrations up to 10 mg/ml. Regression analyses revealed different relationships between membrane permeabilization and staphylocidal activity for the distinct antimicrobial peptides. Taken together, these findings demonstrate that permeabilization, per se, does not invariably result in staphylococcal death due to distinct antimicrobial peptides. Thus, although each of these peptides interacts with the
S. aureus
cytoplasmic membrane, diversity exists in their mechanisms of action with respect to the relationship between membrane permeabilization and staphylocidal activity.
Bartonella henselaeInduces NF-κB-Dependent Upregulation of Adhesion Molecules in Cultured Human Endothelial Cells: Possible Role of Outer Membrane Proteins as Pathogenic Factors
Authors: Fuhrmann Oliver , Arvand Mardjan , Göhler Alexander , Schmid Michael , Krüll Matthias , Hippenstiel Stefan , Seybold Joachim , Dehio Christoph , Suttorp Norbert 
Published: July 2002

ABSTRACTThe endothelium is a specific target forBartonella henselae, and endothelial cell infection represents an important step in the pathogenesis of cat scratch disease and bacillary angiomatosis. Mechanisms ofBartonella-endothelial cell interaction as well as signaling pathways involved in target cell activation were analyzed.B. henselaestrain Berlin-1, isolated from bacillary angiomatosis lesions of a human immunodeficiency virus-infected patient, potently stimulated human umbilical cord vein endothelial cells (HUVEC), as determined by NF-κB activation and enhanced adhesion molecule expression. These effects were accompanied by increased PMN rolling on and adhesion to infected endothelial cell monolayers, as measured in a parallel-plate flow chamber assay. Monoclonal antibodies against E-selectin significantly reduced PMN rolling and adhesion. In our hands,B. henselaeBerlin-1 was substantially more active than the typing strainB. henselaeATCC 49882. E-selectin and ICAM-1 upregulation occurred for up to 9 days, as verified by Northern blotting and cell surface enzyme-linked immunosorbent assay. Induction of adhesion molecules was mediated via NF-κB activation and could be blocked by a specific NF-κB inhibitor. Additional studies indicated thatB. henselae-induced effects did not require living bacteria orBartonellalipopolysaccharides. Exposure of HUVEC to purifiedB. henselaeouter membrane proteins (OMPs), however, reproduced all aspects of endothelial cell activation. In conclusion,B. henselae, the causative agent of cat scratch disease and bacillary angiomatosis, infects and activates endothelial cells.B. henselaeOMPs are sufficient to induce NF-κB activation and adhesion molecule expression followed by enhanced rolling and adhesion of leukocytes. These observations identify important new properties ofB. henselae, demonstrating its capacity to initiate a cascade of events culminating in a proinflammatory phenotype of infected endothelial cells.
Localization of Surface Immunogenic Protein on Group B Streptococcus
Authors: Rioux Stéphane , Martin Denis , Ackermann Hans-Wolfgang , Dumont Julie , Hamel Josée , Brodeur Bernard R. 
Published: July 2002

ABSTRACT
The localization and accessibility of the group B streptococcus (GBS) surface immunogenic protein (Sip) at the surface of intact GBS cells were studied by flow cytometric assay and immunogold electron microscopy. Antibodies present in pooled sera collected from mice after immunization with purified recombinant Sip efficiently recognized native Sip at the surfaces of the different GBS strains tested, which included representatives of all nine serotypes. Examination of GBS cells by immunogold electron microscopy revealed that the Sip-specific antibodies attached preferentially to polar sites and the septal region. This result confirmed that Sip is exposed at the intact-cell surface, but it also suggests that its distribution is restricted to certain regions of the cell.
Novel Extracellular x-Prolyl Dipeptidyl-Peptidase (DPP) from
Streptococcus gordonii
FSS2: an Emerging Subfamily of Viridans Streptococcal x-Prolyl DPPs
Authors: Goldstein J. M. , Banbula A. , Kordula T. , Mayo J. A. , Travis J. 
Published: July 2002

ABSTRACT

Streptococcus gordonii
is generally considered a benign inhabitant of the oral microflora, and yet it is a primary etiological agent in the development of subacute bacterial endocarditis (SBE), an inflammatory state that propagates thrombus formation and tissue damage on the surface of heart valves. Strain FSS2 produced several extracellular aminopeptidase and fibrinogen-degrading activities during growth in culture. In this report we describe the purification, characterization, and cloning of a serine class dipeptidyl-aminopeptidase, an x-prolyl dipeptidyl-peptidase (Sg-xPDPP, for
S. gordonii
x-prolyl dipeptidyl-peptidase), produced in a pH-controlled batch culture. Purification of this enzyme by anion exchange, gel filtration, and hydrophobic interaction chromatography yielded a protein monomer of approximately 85 kDa, as shown by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (PAGE) under denaturing conditions. However, under native conditions, the protein appeared to be a homodimer on the basis of gel filtration and PAGE. Kinetic studies indicated that purified enzyme had a unique and stringent x-prolyl specificity that is comparable to both the dipeptidyl-peptidase IV/CD26 and lactococcal x-prolyl dipeptidyl-peptidase families. Nested PCR cloning from an
S. gordonii
library enabled the isolation and sequence analysis of the full-length gene. A 759-amino-acid polypeptide with a theoretical molecular mass of 87,115 Da and a calculated pI of 5.6 was encoded by this open reading frame. Significant homology was found with the PepX gene family from
Lactobacillus
and
Lactococcus
spp. and putative x-prolyl dipeptidyl-peptidases from other streptococcal species. Sg-xPDPP may serve as a critical factor for the sustained bacterial growth in vivo and furthermore may aid in the proteolysis of host tissue that is commonly observed during SBE pathology.
Functional Specific Binding of Testosterone toSchistosoma haematobium28-Kilodalton GlutathioneS-Transferase
Authors: Remoué Franck , Mani Jean-Claude , Pugnière Martine , Schacht Anne-Marie , Capron André , Riveau Gilles 
Published: July 2002

ABSTRACTDuring parasitic disease such as schistosomiasis, sex hormones have an important influence on the age- and gender-dependent level of infection. Since mammal glutathioneS-transferase (GST) has the ability to bind hormones and particularly sexual steroids to influence their transport, metabolism, and physiological action, we have evaluated the capacity of testosterone to bind the 28-kDa GST of theSchistosoma haematobiumparasite (Sh28GST). For the first time, we have demonstrated a specific binding of testosterone to parasite GST protein with high affinity (Kd= 2.57 × 10−7M). In addition, we have assessed the effect of this binding on Sh28GST enzymatic activity, a mechanism closely associated with the reduction ofSchistosomafecundity. We showed that testosterone has the functional ability to inhibit the Sh28GST enzymatic activity in a dose-dependent manner, suggesting that this hormone could be directly involved in an antifecundity mechanism. This effect seemed to be related to the binding of testosterone to one peptide involved in the enzymatic site (i.e., amino acids 24 to 43). During human infection, binding of sexual hormones toSchistosomaSh28GST could play a key role in parasite metabolism, especially the decrease of fecundity, and could be involved in the sex-dependent immune response to Sh28GST that we have previously observed in infected adults.
Control of ExperimentalTrypanosoma bruceiInfections Occurs Independently of Lymphotoxin-α Induction
Authors: Magez S. , Stijlemans B. , Caljon G. , Eugster H.-P. , De Baetselier P. 
Published: July 2002

ABSTRACTTrypanosome infections are marked by severe pathological features, including anemia, splenomegaly, and suppression of T-cell proliferation. We have used lymphotoxin-α-deficient (LT-α−/−) mice, as well as LT-α-tumor necrosis factor-double-deficient (LT-α−/−TNF−/−) mice, to analyze the contributions of these related cytokines in both induction of trypanosomosis-associated immunopathology and infection control. Moreover, as the cytokine-deficient mice used have no detectable lymph nodes and lack germinal-center formation upon immune stimulation, we have analyzed the functional importance of both the lymph nodes and spleen during experimentalTrypanosoma bruceiinfections. First, we show that the absence of LT-α does not significantly alter early trypanosomosis development or pathology but does result in better control of late-stage parasitemia levels and slightly prolonged survival. This increased survival of infected LT-α−/−mice coincides with the appearance of increased chronic-stage anti-trypanosome immunoglobulin M (IgM)-IgG2a serum titers that are generated in the absence of functional peripheral lymphoid tissue and do not require germinal-center formation. Second, we show that splenectomized mice control their parasitemia to the same extent as fully immune-competent littermates. Finally, using LT-α−/−TNF−/−double-deficient mice, we show that in these miceT. bruceiinfections are very well controlled during the chronic infection stage and that infection-induced pathology is minimized. Together, these findings indicate that while increased IgM-IgG2a anti-trypanosome antibody titers (generated in the absence of LT-α, peripheral lymph nodes, and germinal-center formation) coincide with improved parasitemia control, it is TNF that has a major impact on trypanosomosis-associated immunopathology.
Survival ofTropheryma whipplei, the Agent of Whipple's Disease, Requires Phagosome Acidification
Authors: Ghigo Eric , Capo Christian , Aurouze Marianne , Tung Ching-Hsuan , Gorvel Jean-Pierre , Raoult Didier , Mege Jean-Louis 
Published: July 2002

ABSTRACTTropheryma whippleiwas established as the agent of Whipple's disease in 2000, but the mechanisms by which it survives within host cells are still unknown. We show here thatT. whippleisurvives within HeLa cells by controlling the biogenesis of its phagosome. Indeed,T. whippleicolocalized with lysosome-associated membrane protein 1, a membrane marker of late endosomal and lysosomal compartments, but not with cathepsin D, a lysosomal hydrolase. This defect in phagosome maturation is specific to live organisms, since heat-killed bacilli colocalized with cathepsin D. In addition,T. whippleisurvived within HeLa cells by adapting to acidic pH. The vacuoles containingT. whippleiwere acidic (pH 4.7 ± 0.3) and acquired vacuolar ATPase, responsible for the acidic pH of late phagosomes. The treatment of HeLa cells with pH-neutralizing reagents, such as ammonium chloride,N-ethylmaleimide, bafilomycin A1, and chloroquine, increased the intravacuolar pH and promoted the killing ofT. whipplei. The ability ofT. whippleito survive in an acidic environment and to interfere with phagosome-lysosome fusion is likely critical for its prolonged persistence in host cells during the course of Whipple's disease. Our results suggest that manipulating the intravacuolar pH may provide a new approach for the treatment of Whipple's disease.
Deletion of T Cells Bearing the Vβ8.1 T-Cell Receptor following Mouse Mammary Tumor Virus 7 Integration Confers Resistance to Murine Cerebral Malaria
Authors: Gorgette Olivier , Existe Alexandre , Boubou Mariama Idrissa , Bagot Sébastien , Guénet Jean-Louis , Mazier Dominique , Cazenave Pierre-André , Pied Sylviane 
Published: July 2002

ABSTRACTPlasmodium bergheiANKA induces a fatal neurological syndrome known as cerebral malaria (CM) in susceptible mice. Host genetic elements are among the key factors determining susceptibility or resistance to CM. Analysis of mice of the sameH-2haplotype revealed that mouse mammary tumor virus 7 (MTV-7) integration into chromosome 1 is one of the key factors associated with resistance to neurological disease duringP. bergheiANKA infection. We investigated this phenomenon by infecting a series of recombinant inbred mice (CXD2), derived from BALB/c (susceptible to CM) and DBA/2 (resistant to CM) mice, withP. bergheiANKA. We observed differences in susceptibility to CM induced by thisPlasmodiumstrain. Mice with the MTV-7 sequence in their genome were resistant to CM, whereas those without integration of this gene were susceptible. Thus, an integrated proviral open reading frame or similar genomic sequences may confer protection against neuropathogenesis during malaria, at least in mice.
Treponema denticolaIs Resistant to Human β-Defensins
Authors: Brissette Catherine A. , Lukehart Sheila A. 
Published: July 2002

ABSTRACTSpirochetes, includingTreponema denticola, are implicated in the pathogenesis of periodontal disease. BecauseT. denticolalacks lipopolysaccharides that serve as targets for human β-defensin (hβD) binding, we postulated thatT. denticolawould resist killing by hβD. We showed thatT. denticolais resistant to hβD-1 and -2. Protease inhibitors did not enhance killing ofT. denticolaby hβD-2, suggesting that degradation of hβD-2 by treponemal proteases is not a major factor inT. denticolaresistance.
FabG, an NADPH-Dependent 3-Ketoacyl Reductase ofPseudomonas aeruginosa, Provides Precursors for Medium-Chain-Length Poly-3-Hydroxyalkanoate Biosynthesis inEscherichia coli
Authors: Ren Qun , Sierro Nicolas , Witholt Bernard , Kessler Birgit 
Published: July 2002

ABSTRACTEscherichia colihosts expressingfabGofPseudomonas aeruginosashowed 3-ketoacyl coenzyme A (CoA) reductase activity towardR-3-hydroxyoctanoyl-CoA. Furthermore,E. colirecombinants carrying the poly-3-hydroxyalkanoate (PHA) polymerase-encoding genephaCin addition tofabGaccumulated medium-chain-length PHAs (mcl-PHAs) from alkanoates. WhenE. coli fadBorfadAmutants, which are deficient in steps downstream or upstream of the 3-ketoacyl-CoA formation step during β-oxidation, respectively, were transformed withfabG, higher levels of PHA were synthesized inE. coli fadA, whereas similar levels of PHA were found inE. coli fadB, compared with those of the corresponding mutants carryingphaCalone. These results strongly suggest that FabG ofP. aeruginosais able to reduce mcl-3-ketoacyl-CoAs generated by the β-oxidation to 3-hydroxyacyl-CoAs to provide precursors for the PHA polymerase.
Proteolysis of Bacteriophage λ CII by
Escherichia coli
FtsH (HflB)
Authors: Shotland Yoram , Shifrin Amir , Ziv Tamar , Teff Dinah , Koby Simi , Kobiler Oren , Oppenheim Amos B. 
Published: July 2002

ABSTRACT
FtsH (HflB) is a conserved, highly specific, ATP-dependent protease for which a number of substrates are known. The enzyme participates in the phage λ lysis-lysogeny decision by degrading the lambda CII transcriptional activator and by its response to inhibition by the λ CIII gene product. In order to gain further insight into the mechanism of the enzymatic activity of FtsH (HflB), we identified the peptides generated following proteolysis of the phage λ CII protein. It was found that FtsH (HflB) acts as an endopeptidase degrading CII into small peptides with limited amino acid specificity at the cleavage site. β-Casein, an unstructured substrate, is also degraded by FtsH (HflB), suggesting that protein structure may play a minor role in determining the products of proteolysis. The majority of the peptides produced were 13 to 20 residues long.
Hypersensitivity of
Escherichia coli Δ
(
uvrB-bio
) Mutants to 6-Hydroxylaminopurine and Other Base Analogs Is Due to a Defect in Molybdenum Cofactor Biosynthesis
Authors: Kozmin Stanislav G. , Pavlov Youri I. , Dunn Ronnie L. , Schaaper Roel M. 
Published: July 2002

ABSTRACT

We have shown previously that
Escherichia coli
and
Salmonella enterica
serovar Typhimurium strains carrying a deletion of the
uvrB-bio
region are hypersensitive to the mutagenic and toxic action of 6-hydroxylaminopurine (HAP) and related base analogs. This sensitivity is not due to the
uvrB
excision repair defect associated with this deletion because a
uvrB
point mutation or a
uvrA
deficiency does not cause hypersensitivity. In the present work, we have investigated which gene(s) within the deleted region may be responsible for this effect. Using independent approaches, we isolated both a point mutation and a transposon insertion in the
moeA
gene, which is located in the region covered by the deletion, that conferred HAP sensitivity equal to that conferred by the
uvrB-bio
deletion. The
moeAB
operon provides one of a large number of genes responsible for biosynthesis of the molybdenum cofactor. Defects in other genes in the same pathway, such as
moa
or
mod
, also lead to the same HAP-hypersensitive phenotype. We propose that the molybdenum cofactor is required as a cofactor for an as yet unidentified enzyme (or enzymes) that acts to inactivate HAP and other related compounds.
Requirements for Conversion of the Na
+
-Driven Flagellar Motor of
Vibrio cholerae
to the H
+
-Driven Motor of
Escherichia coli
Authors: Gosink Khoosheh K. , Häse Claudia C. 
Published: July 2002

ABSTRACT

Bacterial flagella are powered by a motor that converts a transmembrane electrochemical potential of either H
+
or Na
+
into mechanical work. In
Escherichia coli
, the MotA and MotB proteins form the stator and function in proton translocation, whereas the FliG protein is located on the rotor and is involved in flagellar assembly and torque generation. The sodium-driven polar flagella of
Vibrio
species contain homologs of MotA and MotB, called PomA and PomB, and also contain two other membrane proteins called MotX and MotY, which are essential for motor rotation and that might also function in ion conduction. Deletions in
pomA
,
pomB
,
motX
, or
motY
in
Vibrio cholerae
resulted in a nonmotile phenotype, whereas deletion of
fliG
gave a nonflagellate phenotype.
fliG
genes on plasmids complemented
fliG
-null strains of the parent species but not
fliG
-null strains of the other species. FliG-null strains were complemented by chimeric FliG proteins in which the C-terminal domain came from the other species, however, implying that the C-terminal part of FliG can function in conjunction with the ion-translocating components of either species. A
V. cholerae
strain deleted of
pomA
,
pomB
,
motX
, and
motY
became weakly motile when the
E. coli motA
and
motB
genes were introduced on a plasmid. Like
E. coli
, but unlike wild-type
V. cholerae
, motility of some
V. cholerae
strains containing the hybrid motor was inhibited by the protonophore carbonyl cyanide
m
-chlorophenylhydrazone under neutral as well as alkaline conditions but not by the sodium motor-specific inhibitor phenamil. We conclude that the
E. coli
proton motor components MotA and MotB can function in place of the motor proteins of
V. cholerae
and that the hybrid motors are driven by the proton motive force.