bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthetic Peptide Immunogens Elicit Polyclonal and Monoclonal Antibodies Specific for Linear Epitopes in the D Motifs of
Staphylococcus aureus
Fibronectin-Binding Protein, Which Are Composed of Amino Acids That Are Essential for Fibronectin Binding
Authors: Huesca Mario , Sun Qing , Peralta Robert , Shivji Gulnar M. , Sauder Daniel N. , McGavin Martin J. 
Published: July 2002

ABSTRACT

A fibronectin (Fn)-binding adhesin of
Staphylococcus aureus
contains three tandem 37- or 38-amino-acid motifs (D1, D2, and D3), which function to bind Fn. Plasma from patients with
S. aureus
infections contain antibodies that preferentially recognize ligand induced binding sites in the D motifs and do not inhibit Fn binding (F. Casolini, L. Visai, D. Joh, P. G. Conaldi, A. Toniolo, M. Höök, and P. Speziale, Infect. Immun. 66:5433–5442, 1998). To eliminate the influence of Fn binding on antibody development, we used synthetic peptide immunogens D1
21–34
and D3
20–33
, which each contain a conserved pattern of amino acids that is essential for Fn binding but which cannot bind Fn without N- or C-terminal extensions. The D3
20–33
immunogen promoted the production of polyclonal antibodies that were 10-fold more effective as inhibitors of Fn-binding to the D3 motif than antibodies obtained by immunizing with an extended peptide D3
16–36
, which exhibits functional Fn binding. The D3
20–33
immunogen also facilitated the production of a monoclonal antibody, 9C3, which was highly specific for the epitope SVDFEED, and abolished Fn binding by the D3 motif. When mixed with polyclonal anti-D1
21–34
immunoglobulin G, 70% inhibition of Fn binding to the three tandem D motifs was achieved compared to no more than 30% inhibition with either antibody preparation alone. Therefore, by immunizing with short synthetic peptides that are unable to bind Fn, we have effectively stimulated the production of antibodies specific for epitopes comprised of amino acids that are essential for Fn binding. Although these epitopes occur within a conserved pattern of amino acids that is required for Fn binding, the antibodies recognized specific linear epitope sequences and not a conserved structure common to all repeated motifs.
Lipopolysaccharide Entry in the Damaged Cornea and Specific Uptake by Polymorphonuclear Neutrophils
Authors: Schultz C. L. , Buret A. G. , Olson M. E. , Ceri H. , Read R. R. , Morck D. W. 
Published: July 2002

ABSTRACT

Bacterial lipopolysaccharide (LPS) is an important agent of induction of ocular pathology following corneal injury or wearing of contaminated contact lenses. The mechanism of LPS uptake through the corneal epithelium is unclear, and the role played by inflammatory cells in this phenomenon has not been previously assessed. Fluorescein isothiocyanate-labeled LPS from
Escherichia coli
was deposited onto the abraded corneas of New Zealand White rabbits. Epifluorescence microscopy of living excised corneas revealed diffuse LPS staining in the epithelial and stromal layers only in the vicinity of the abrasion. In addition, specific cellular uptake of LPS was suggested by fluorescence staining of cells along the abrasion site. In a second series of experiments, an anti-CD18 polyclonal antibody was used to block infiltration of polymorphonuclear neutrophils (PMN) into the cornea. In these experiments, a diffuse distribution of fluorescent LPS was still observed along the abrasion, but the specific cellular uptake was abolished. The findings indicate that LPS enters the cornea via diffuse penetration at sites of injury and that specific cellular uptake of LPS occurs within the cornea via PMN which have migrated into the damaged tissue.
Immunoglobulin G3 Antibodies Specific for the 19-Kilodalton Carboxyl-Terminal Fragment ofPlasmodium yoeliiMerozoite Surface Protein 1 Transfer Protection to Mice Deficient in Fc-γRI Receptors
Authors: Vukovic Peter , Hogarth P. Mark , Barnes Nadine , Kaslow David C. , Good Michael F. 
Published: July 2002

ABSTRACTMerozoite surface protein 1 (MSP-119) is a leading malaria vaccine candidate. Specific antibodies contribute to immunity; binding to macrophages is believed to represent the main action of malaria antibodies. We show that an MSP-119-specific immunoglobulin G3 (IgG3) monoclonal antibody can passively transfer protection to mice deficient in the α chain of Fc-γRI whose macrophages cannot bind IgG3.
Transcriptional Organization and Function of Invasion Genes within
Salmonella enterica
Serovar Typhimurium Pathogenicity Island 1, Including the
prgH
,
prgI
,
prgJ
,
prgK
,
orgA
,
orgB
, and
orgC
Genes
Authors: Klein Joanna R. , Fahlen Thomas F. , Jones Bradley D. 
Published: July 2002

ABSTRACT

Salmonella enterica
serovar Typhimurium initiates infection of a host by inducing its own uptake into specialized M cells which reside within the epithelium overlaying Peyer's patches. Entry of
Salmonella
into intestinal epithelial cells is dependent upon invasion genes that are clustered together in
Salmonella
pathogenicity island 1 (SPI-1). Upon contact between serovar Typhimurium and epithelial cells targeted for bacterial internalization, bacterial proteins are injected into the host cell through a type III secretion system that leads to internalization of the bacteria. Previous work has established that the
prgH
, -
I
, -
J
, and -
K
and
orgA
genes reside in SPI-1, and the products of these genes are predicted to be components of the invasion secretion apparatus. We report that an error in the published
orgA
DNA sequence has been identified so that this region encodes two small genes rather than a single large open reading frame. These genes have been designated
orgA
and
orgB
. Additionally, an opening reading frame downstream of
orgB
, which we have designated
orgC
, has been identified and partially characterized. Previously published work has indicated that the
prgH
, -
I
, -
J
, and -
K
genes are transcribed from a promoter distinct from that used by the gene immediately downstream,
orgA
. Here, we present experiments indicating that
orgA
expression is driven by the
prgH
promoter. In addition, using reverse transcriptase PCR analysis, we have found that this polycistronic message extends downstream of
prgH
to include a total of 10 genes. To more fully characterize this invasion operon, we demonstrate that the
prgH
,
prgI
,
prgJ
,
prgK
,
orgA
, and
orgB
genes are each required for invasion and secretion, while
orgC
is not essential for the invasive phenotype.
The Capsule Is a Virulence Determinant in the Pathogenesis ofPasteurella multocidaM1404 (B:2)
Authors: Boyce John D. , Adler Ben 
Published: July 2002

ABSTRACTCapsules from a range of pathogenic bacteria are key virulence determinants, and the capsule has been implicated in virulence inPasteurella multocida. We have previously identified and determined the nucleotide sequence of theP. multocidaM1404 (B:2) capsule biosynthetic locus (J. D. Boyce, J. Y. Chung, and B. Adler, Vet. Microbiol. 72:121–134, 2000). Thecaplocus consists of 15 genes, which can be grouped into three functional regions. Regions 1 and 3 contain genes proposed to encode proteins involved in capsule export, and region 2 contains genes proposed to encode proteins involved in polysaccharide biosynthesis. In order to construct a mutant impaired in capsule export, the final gene of region 1,cexA, was disrupted by insertion of a tetracycline resistance cassette by allelic replacement. The genotype of thetet(M) ΩcexAmutant was confirmed by Southern hybridization and PCR. The acapsular phenotype was confirmed by immunofluorescence, and the strain could be complemented and returned to capsule production by the presence of a cloned uninterrupted copy ofcexA. Wild-type, mutant, and complemented strains were tested for virulence by intraperitoneal challenge of mice; the presence of the capsule was shown to be a crucial virulence determinant. Following intraperitoneal challenge of mice, the acapsular bacteria were removed efficiently from the blood, spleen, and liver, while wild-type bacteria multiplied rapidly. Acapsular bacteria were readily taken up by murine peritoneal macrophages, but wild-type bacteria were significantly resistant to phagocytosis. Both wild-type and acapsular bacteria were resistant to complement in bovine and murine serum.
Detection of Phase Variation in Expression of Proteins Involved in Hemoglobin and Hemoglobin-Haptoglobin Binding by Nontypeable
Haemophilus influenzae
Authors: Cope Leslie D. , Hrkal Zbynek , Hansen Eric J. 
Published: July 2002

ABSTRACT

Haemophilus influenzae
can utilize different protein-bound forms of heme for growth in vitro. A previous study (I. Maciver, J. L. Latimer, H. H. Liem, U. Muller-Eberhard, Z. Hrkal, and E. J. Hansen. Infect. Immun. 64:3703–3712, 1996) indicated that nontypeable
H. influenzae
(NTHI) strain TN106 expressed a protein that bound hemoglobin-haptoglobin and was encoded by an open reading frame (ORF) that contained a CCAA nucleotide repeat. Southern blot analysis revealed that several NTHI strains contained between three and five chromosomal DNA fragments that bound an oligonucleotide probe for CCAA repeats. Three ORFs containing CCAA repeats were identified in NTHI strain N182; two of these ORFs were arranged in tandem. The use of translational fusions involving these three ORFs and the β-lactamase gene from pBR322 revealed that these three ORFs, designated
hgbA
,
hgbB
, and
hgbC
, encoded proteins that could bind hemoglobin, hemoglobin-haptoglobin, or both compounds. Monoclonal antibodies (MAbs) specific for the HgbA, HgbB, and HgbC proteins were produced by immunizing mice with synthetic peptides unique to each protein. Both HgbA and HgbB were readily detected by Western blot analysis in N182 cells grown in the presence of hemoglobin as the sole source of heme, whereas expression of HgbC was found to be much less abundant than that of HgbA and HgbB. The use of these MAbs in a colony blot radioimmunoassay analysis revealed that expression of both HgbA and HgbB was subject to phase variation. PCR and nucleotide sequence analysis were used in conjunction with Western blot analyses to demonstrate that this phase variation involved the CCAA repeats in the
hgbA
and
hgbB
ORFs.
Up-Regulation of Both Intimin and
eae
-Independent Adherence of Shiga Toxigenic
Escherichia coli
O157 by
ler
and Phenotypic Impact of a Naturally Occurring
ler
Mutation
Authors: Ogierman Monica A. , Paton Adrienne W. , Paton James C. 
Published: July 2002

ABSTRACT

Shiga toxigenic
Escherichia coli
(STEC) strains are important human pathogens which are capable of causing diarrhea, hemorrhagic colitis, and the potentially fatal hemolytic-uremic syndrome (HUS). An important virulence trait of certain STEC strains, such as those belonging to serogroup O157, is the capacity to produce attaching and effacing (A/E) lesions on enterocytes, a property encoded by the locus for enterocyte effacement (LEE). LEE contains the
eae
gene, which encodes intimin, an outer membrane protein which mediates the intimate attachment of bacteria to the host epithelial cell surface, and
eae
is routinely used as a marker for LEE-positive STEC strains. However, the O157:H
−
STEC strain 95SF2 carries
eae
but did not produce A/E lesions on HEp-2 cells, as judged by a fluorescent actin staining assay. In this assay, 95SF2 adhered poorly to the HEp-2 cells, and those that did bind exhibited abnormal cell division. In contrast, the O157:H7 STEC strain EDL933 adhered strongly and produced typical A/E lesions. We have demonstrated that 95SF2 carries a defective LEE regulatory gene,
ler
, with a single base change with respect to that published for
ler
of EDL933, resulting in an Ile
57
-to-Thr substitution. Ler shows homology to H-NS-like regulators, which are modulators of transcription, and the mutation occurs in a domain implicated in oligomerization. 95SF2 was able to adhere and produce A/E lesions on HEp-2 cells when EDL933
ler
was expressed from a multicopy plasmid. Conversely, introduction of a plasmid carrying 95SF2
ler
into EDL933 abolished adherence and capacity to form A/E lesions. Studies with
eae
deletion derivatives of 95SF2 and EDL933 demonstrated that the
ler
-mediated adherence to HEp-2 cells is largely independent of intimin. We have also demonstrated that EDL933
ler
, but not 95SF2
ler
, increases the level of intimin in O157 STEC.
Amino Acid Transport into Cultured McCoy Cells Infected with
Chlamydia trachomatis
Authors: Harper Angela , Pogson Christopher I. , Pearce John H. 
Published: July 2002

ABSTRACT

Amino acid transport into McCoy cells infected with strains representative of the two major biovars of
Chlamydia trachomatis
has been studied to determine if uptake is increased during infection. Preliminary work suggested that the transport systems L, A/ASC (for neutral amino acid transport), N (for transport of Asn, Gln, and His) and y+ (for cationic amino acids) were present in McCoy cells. With lymphogranuloma venereum biovar strain 434, little difference in the influx of representative amino acids Trp, His, and Lys or the analogue 2-aminoisobutyric acid (AIB) was observed during infection. With trachoma biovar strain DK20, a small increase in the initial entry rate and equilibrium concentration of each amino acid was found. McCoy cells appear to have great capacity for concentrating amino acids, which might obviate the need for transport induction by chlamydiae under conditions favoring the growth of infectious organisms.
Role of Plasma, Lipopolysaccharide-Binding Protein, and CD14 in Response of Mouse Peritoneal Exudate Macrophages to Endotoxin
Authors: Heumann Didier , Adachi Yoshiyuki , Le Roy Didier , Ohno Naohito , Yadomae Toshiro , Glauser Michel Pierre , Calandra Thierry 
Published: July 2002

ABSTRACTPlasma lipopolysaccharide (LPS)-binding protein (LBP) and membrane CD14 function to enhance the responses of monocytes to low concentrations of endotoxin. Surprisingly, recent reports have suggested that LBP or CD14 may be dispensable for macrophage responses to low concentrations of LPS or may even exert an inhibitory effect in the case of LBP. We therefore investigated whether LBP and CD14 participated in the response of mouse peritoneal exudate macrophages (PEM) to LPS stimulation. In the presence of a low amount of plasma (<1%) or of recombinant mouse or human LBP, PEM were found to respond to low concentrations of LPS (<5 to 10 ng/ml) in an LBP- and CD14-dependent manner. However, tumor necrosis factor production (not interleukin-6 production) by LPS-stimulated PEM was reduced when cells were stimulated in the presence of higher concentrations of plasma or serum (5 or 10%). Yet, the inhibitory effect of plasma or serum was not mediated by LBP. Taken together with previous results obtained withLBPandCD14knockout mice in models of experimental endotoxemia, the present data confirm a critical part for LBP and CD14 in innate immune responses of both blood monocytes and tissue macrophages to endotoxins.
Tir Tyrosine Phosphorylation and Pedestal Formation Are Delayed in Enteropathogenic
Escherichia coli sepZ
::Tn
phoA
Mutant 30-5-1(3)
Authors: Devinney Rebekah , Nisan Israel , Ruschkowski Sharon , Rosenshine Ilan , Finlay B. Brett 
Published: July 2002

ABSTRACT

Enteropathogenic
Escherichia coli
(EPEC) strain 30-5-1(3) has been reported to form attaching and effacing (A/E) lesions without Tir tyrosine phosphorylation. In this study, we show that 30-5-1(3), which has a transposon insertion within the
sepZ
gene, forms wild-type A/E lesions including Tir tyrosine phosphorylation, but at a slower rate. A/E lesion formation by 30-5-1(3) occurs without detectable secretion of Tir or other EPEC Esp secreted proteins.
Mannheimia haemolyticaLeukotoxin Activates a Nonreceptor Tyrosine Kinase Signaling Cascade in Bovine Leukocytes, Which Induces Biological Effects
Authors: Jeyaseelan S. , Kannan M. S. , Briggs R. E. , Thumbikat P. , Maheswaran S. K. 
Published: July 2002

ABSTRACTThe leukotoxin (LktA) produced byMannheimia haemolyticabinds to bovine lymphocyte function-associated antigen 1 (LFA-1) and induces biological effects in bovine leukocytes in a cellular and species-specific fashion. We have previously shown that LktA also binds to porcine LFA-1 without eliciting any effects. These findings suggest that the specificity of LktA effects must entail both binding to LFA-1 and activation of signaling pathways which are present in bovine leukocytes. However, the signaling pathways leading to biological effects upon LktA binding to LFA-1 have not been characterized. In this context, several reports have indicated that ligand binding to LFA-1 results in activation of a nonreceptor tyrosine kinase (NRTK) signaling cascade. We designed experiments with the following objectives: (i) to determine whether LktA binding to LFA-1 leads to activation of NRTKs, (ii) to examine whether LktA-induced NRTK activation is target cell specific, and (iii) to determine whether LktA-induced NRTK activation is required for biological effects. We used a biologically inactive mutant leukotoxin (ΔLktA) for comparison with LktA. Our results indicate that LktA induces tyrosine phosphorylation (TP) of the CD18 tail of LFA-1 in bovine leukocytes. The ΔLktA mutant does not induce TP of the CD18 tail, albeit binding to bovine LFA-1. LktA-induced TP of the CD18 tail was attenuated by an NRTK inhibitor, herbimycin A; a phosphatidylinositol 3′-kinase (PI 3-kinase) inhibitor, wortmannin; and a Src kinase inhibitor, PP2, in a concentration-dependent manner. Furthermore, LktA induces TP of the CD18 tail in bovine, but not porcine, leukocytes. Moreover, LktA-induced intracellular calcium ([Ca2+]i) elevation was also inhibited by herbimycin A, wortmannin, and PP2. Thus, our data represent the first evidence that binding of LktA to bovine LFA-1 induces a species-specific NRTK signaling cascade involving PI 3-kinase and Src kinases and that this signaling cascade is required for LktA-induced biological effects.
Immunization with Components of Two Iron Uptake ABC Transporters Protects Mice against Systemic
Streptococcus pneumoniae
Infection
Authors: Brown Jeremy S. , Ogunniyi A. David , Woodrow Matthew C. , Holden David W. , Paton James C. 
Published: July 2002

ABSTRACT

There has been considerable recent research into protein based
Streptococcus pneumoniae
vaccines as alternatives to the existing capsular antigen vaccines. PiuA and PiaA (formerly Pit1A and Pit2A) are recently identified lipoprotein components of
S. pneumoniae
iron uptake ABC transporters which are required for full virulence and are likely to be expressed on the surface of the bacterial cell membrane. We investigated the efficacy of recombinant PiuA and PiaA proteins at eliciting protective immunity in mice against systemic infection with
S. pneumoniae
. Both recombinant PiuA and PiaA generated antibody responses that cross-reacted with each other but not with pneumolysin and reacted with identical proteins from nine different
S. pneumoniae
serotypes. Mice immunized with recombinant PiuA and PiaA were protected against systemic challenge to a degree similar to those immunized with an existing protein vaccine candidate, PdB (a genetically modified pneumolysin toxoid). Immunization with a combination of both PiuA and PiaA resulted in additive protection and was highly protective against systemic infection with
S. pneumoniae
. PiuA and PiaA are therefore promising additional candidates for a novel
S. pneumoniae
vaccine using protein antigens.
Regulated Expression and Effect of Galectin-1 onTrypanosoma cruzi-Infected Macrophages: Modulation of Microbicidal Activity and Survival
Authors: Zúñiga Elina , Gruppi Adriana , Hirabayashi Jun , Kasai Ken I. , Rabinovich Gabriel A. 
Published: July 2002

ABSTRACTGalectin-1 is a β-galactoside-binding protein with potent anti-inflammatory and immunoregulatory effects. However, its expression and function have not been assessed in the context of an infectious disease. The present study documents, for the first time, the regulated expression of galectin-1 in the context of an infectious process and its influence in the modulation of macrophage microbicidal activity and survival. A biphasic modulation in parasite replication and cell viability was observed when macrophages isolated fromTrypanosoma cruzi-infected mice were exposed to increasing concentrations of galectin-1. While low concentrations of this protein increased parasite replication and did not affect macrophage survival, higher inflammatory doses of galectin-1 were able to commit cells to apoptosis and inhibited parasite replication. Furthermore, galectin-1 at its lowest concentration was able to down-regulate critical mediators for parasite killing, such as interleukin 12 (IL-12) and nitric oxide, while it did not affect IL-10 secretion. Finally, endogenous galectin-1 was found to be up-regulated and secreted by the J774 macrophage cell line cultured in the presence of trypomastigotes. This result was extended in vivo by Western blot analysis, flow cytometry, and reverse transcription-PCR using macrophages isolated fromT. cruzi-infected mice. This study documents the first association between galectin-1's immunoregulatory properties and its role in infection and provides new clues to the understanding of the mechanisms implicated in host-parasite interactions during Chagas' disease and other parasite infections.
Effect of Deficiency of Tumor Necrosis Factor Alpha or Both of Its Receptors onStreptococcus pneumoniaeCentral Nervous System Infection and Peritonitis
Authors: Wellmer Andreas , Gerber Joachim , Ragheb Jasmin , Zysk Gregor , Kunst Tammo , Smirnov Alexander , Brück Wolfgang , Nau Roland 
Published: July 2002

ABSTRACTTumor necrosis factor alpha (TNF-α) and TNF-β are key mediators in bacterial inflammation. We therefore examined the role of TNF-α and its two receptors in murine pneumococcal central nervous system infection. TNF-α knockout mice and age- and sex-matched controls and TNF receptor (p55 and p75)-deficient mice and heterozygous littermates were infected intracerebrally with aStreptococcus pneumoniaetype 3 strain. Mice were monitored until death or were killed 36 h after infection. Bacterial titers in blood, spleen, and brain homogenates were determined. Leukocyte infiltration and neuronal damage were assessed by histological scores. TNF-α-deficient mice died earlier than the controls after intracerebral infection although overall survival was similar. TNF-α deficiency did not inhibit leukocyte recruitment into the subarachnoid space and did not lead to an increased density of bacteria in brain homogenates. However, it caused a substantial rise of the concentration ofS. pneumoniaecells in blood and spleen. Spleen bacterial titers were also increased in p55- and p75-deficient mice. TNF receptor-deficient mice showed decreased meningeal inflammation. Neuronal damage was not affected by either TNF-α or TNF receptor deficiency. In a murine model of pneumococcal peritonitis, 102CFU ofS. pneumoniaeproduced fatal peritonitis in TNF-α-deficient, but not wild-type, mice. Early leukocyte influx into the peritoneum was impaired in TNF-α-deficient mice. The lack of TNF-α or its receptors renders mice more susceptible toS. pneumoniaeinfections.