bluuebunny/crossref_metadata_2025_split huggingface dataset:
N-Formyl-Methionyl-Leucyl-Phenylalanine Inhibits both Gamma Interferon- and Interleukin-10-Induced Expression of FcγRI on Human Monocytes
Authors: Beigier-Bompadre Macarena , Barrionuevo Paula , Alves-Rosa Fernanda , Rubel Carolina J. , Palermo Marina S. , Isturiz Martı́n A. 
Published: July 2002

ABSTRACTThree different classes of receptors for the Fc portion of immunoglobulin G (FcγRs), FcγRI, FcγRII, and FcγRIII, have been identified on human leukocytes. One of them, FcγRI, is a high-affinity receptor capable of induction of functions that include phagocytosis, respiratory burst, antibody-dependent cell-mediated cytotoxicity (ADCC), and secretion of cytokines. This receptor is expressed on mononuclear phagocytes, and this expression is regulated by cytokines and hormones such as gamma interferon (IFN-γ), IFN-β, interleukin-10 (IL-10), and glucocorticoids. We have recently demonstrated that the chemotactic peptideN-formyl-methionyl-leucyl-phenylalanine (FMLP) is capable of inducing a time-dependent downregulation of both FcγRIIIB and FcγRII in human neutrophils, altering FcγR-dependent functions. Considering the biological relevance of the regulation of FcγRI, we investigated the effect of FMLP on the overexpression of FcγRI induced by both IFN-γ and IL-10 on human monocytes. We demonstrate that FMLP significantly abrogated IFN-γ- and IL-10-induced FcγRI expression, although its basal level of expression was not altered. However, other IFN-γ-mediated effects such as the overexpression of the major histocompatibility complex class II antigens and the enhancement of lipopolysaccharide-induced secretion of tumor necrosis factor alpha were not affected by FMLP treatment. The formyl peptide completely inhibited the IFN-γ- and IL-10-induced enhancement of ADCC and phagocytosis carried out by adherent cells. The inhibitory effect of FMLP on FcγRI upregulation could exert an important regulatory effect during the evolution of bacterial infections.
Induction of Mucosal Immune Response after Intranasal or Oral Inoculation of Mice with
Lactococcus lactis
Producing Bovine Beta-Lactoglobulin
Authors: Chatel Jean-Marc , Langella Philippe , Adel-Patient Karine , Commissaire Jacqueline , Wal Jean-Michel , Corthier Gérard 
Published: July 2002

ABSTRACT

The bovine beta-lactoglobulin (BLG) is a major cow's milk allergen. Here, we evaluated the immune response against BLG induced in mice, using the organism
Lactococcus lactis,
which has GRAS (“generally regarded as safe”) status, as a delivery vehicle. The cDNA of the
blg
gene, encoding BLG, was expressed and engineered for either intra- or extracellular expression in
L. lactis
. Using a constitutive promoter, the yield of intracellular recombinant BLG (rBLG) was about 20 ng per ml of culture. To increase the quantity of rBLG, the nisin-inducible expression system was used to produce rBLG in the cytoplasmic and extracellular locations. Although the majority of rBLG remained in the cytoplasm, the highest yield (2 μg per ml of culture) was obtained with a secreting strain that encodes a fusion between a lactococcal signal peptide and rBLG. Whatever the expression system, the rBLG is produced mostly in a soluble, intracellular, and denatured form. The BLG-producing strains were then administered either orally or intranasally to mice, and the immune response to BLG was examined. Specific anti-BLG immunoglobulin A (IgA) antibodies were detected 3 weeks after the immunization protocol in the feces of mice immunized with the secreting lactococcal strain. Specific anti-BLG IgA detected in mice immunized with lactococci was higher than that obtained in mice immunized with the same quantity of pure BLG. No specific anti-BLG IgE, IgA, IgG1, or IgG2a was detected in sera of mice. These recombinant lactococcal strains constitute good vehicles to induce a mucosal immune response to a model allergen and to better understand the mechanism of allergy induced by BLG.
Sensitive Microplate Assay for Detection of Bactericidal Antibodies to
Vibrio cholerae
O139
Authors: Attridge Stephen R. , Johansson Camilla , Trach Dang D. , Qadri Firdausi , Svennerholm Ann-Mari 
Published: July 2002

ABSTRACT

A microplate assay for the detection of bactericidal antibodies to
Vibrio cholerae
O139 is described. The assay is sensitive, highly reproducible, specific, and convenient to perform. It has been used to demonstrate the induction of serum bactericidal antibodies in Vietnamese recipients of an oral, inactivated, bivalent O1/O139 vaccine, as well as in Bangladeshi patients with O139 disease. In both study groups there was a significant inverse correlation between the preexposure level of antibodies in serum and the magnitude of the subsequent bactericidal response. Although infection generated stronger responses than vaccination, the proportion of responders was similar among individuals with low background titers.
Bordetella pertussisTonB, a Bvg-Independent Virulence Determinant
Authors: Pradel Elizabeth , Guiso Nicole , Menozzi Franco D. , Locht Camille 
Published: July 2002

ABSTRACTIn gram-negative bacteria, high-affinity iron uptake requires the TonB/ExbB/ExbD envelope complex to release iron chelates from their specific outer membrane receptors into the periplasm. Based on sequence similarities, theBordetella pertussis tonB exbB exbDlocus was identified on a cloned DNA fragment. The tight organization of the three genes suggests that they are cotranscribed. A putative Fur-binding sequence located upstream fromtonBwas detected in a Fur titration assay, indicating that thetonB exbB exbDoperon may be Fur-repressed in high-iron growth conditions. Putative structural genes of the β-subunit of the histone-like protein HU and of a new two-component regulatory system were identified upstream fromtonBand downstream fromexbD, respectively. AB. pertussis ΔtonB exbB::Kmrmutant was constructed by allelic exchange and characterized. The mutant was impaired for growth in low-iron medium in vitro and could not use ferrichrome, desferal, or hemin as iron sources. Levels of production of the major bacterial toxins and adhesins were similar in the TonB+/TonB−pair. The ΔtonB exbBmutant was still responsive to chemical modulators of virulence; thus, the BvgA/BvgS two-component system is not TonB dependent. Nevertheless, in vivo in the mouse respiratory infection model, the colonization ability of the mutant was reduced compared to the parental strain.
Epitope Mapping of the Immunodominant Invariable Region ofBorrelia burgdorferiVlsE in Three Host Species
Authors: Liang Fang Ting , Philipp Mario T. 
Published: July 2002

ABSTRACTVlsE, the variable surface antigen ofBorrelia burgdorferi, contains a 26-amino-acid-long immunodominant invariable region, IR6. In the present study, three overlapping 14-mer peptides reproducing the sequence of IR6were used as peptide-based enzyme-linked immunosorbent assay antigens to map this invariable region in infected monkeys, mice, and human Lyme disease patients. Antibodies of the two primate species appeared to recognize IR6as a single antigenic determinant, while mouse antibodies recognized multiple epitopes within this region.
Expression of
Staphylococcus aureus
Clumping Factor A in
Lactococcus lactis
subsp.
cremoris
Using a New Shuttle Vector
Authors: Que Yok-Ai , Haefliger Jacques-Antoine , Francioli Patrick , Moreillon Philippe 
Published: July 2002

ABSTRACT

Staphylococcus aureus
harbors redundant adhesins mediating tissue colonization and infection. To evaluate their intrinsic role outside of the staphylococcal background, a system was designed to express them in
Lactococcus lactis
subsp.
cremoris
1363. This bacterium is devoid of virulence factors and has a known genetic background. A new
Escherichia coli-L. lactis
shuttle and expression vector was constructed for this purpose. First, the high-copy-number lactococcal plasmid pIL253 was equipped with the
oriCol
E1 origin, generating pOri253 that could replicate in
E. coli
. Second, the lactococcal promoters
P23
or
P59
were inserted at one end of the pOri253 multicloning site. Gene expression was assessed by a luciferase reporter system. The plasmid carrying
P23
(named pOri23) expressed luciferase constitutively at a level 10,000 times greater than did the
P59
-containing plasmid. Transcription was absent in
E. coli
. The staphylococcal clumping factor A (
clfA
) gene was cloned into pOri23 and used as a model system. Lactococci carrying pOri23-
clfA
produced an unaltered and functional 130-kDa ClfA protein attached to their cell walls. This was indicated both by the presence of the protein in Western blots of solubilized cell walls and by the ability of ClfA-positive lactococci to clump in the presence of plasma. ClfA-positive lactococci had clumping titers (titer of 4,112) similar to those of
S. aureus
Newman in soluble fibrinogen and bound equally well to solid-phase fibrinogen. These experiments provide a new way to study individual staphylococcal pathogenic factors and might complement both classical knockout mutagenesis and modern in vivo expression technology and signature tag mutagenesis.
Use of RNA Arbitrarily Primed-PCR Fingerprinting To Identify
Vibrio cholerae
Genes Differentially Expressed in the Host following Infection
Authors: Chakrabortty Amit , Das Soumita , Majumdar Sabita , Mukhopadhyay Kanchan , Roychoudhury Susanta , Chaudhuri Keya 
Published: July 2002

ABSTRACT

Evidence suggests that a repertoire of
Vibrio cholerae
genes are differentially expressed in vivo, and regulation of virulence factors in vivo may follow a different pathway. Our work was aimed at characterization of in vivo-grown bacteria and identification of genes that are differentially expressed following infection by RNA arbitrarily primed (RAP)-PCR fingerprinting. The ligated rabbit ileal loop model was used. The motility of in vivo-grown bacteria increased by 350% over that of in vitro-grown bacteria. Also, the in vivo-grown cells were more resistant to killing by human serum. By using the RAP-PCR strategy, five differentially expressed transcripts were identified. Two in vitro-induced transcripts encoded polypeptides for the leucine tRNA synthatase and the 50S ribosomal protein, and the three in vivo-induced transcripts encoded the SucA and MurE proteins and a polypeptide of unknown function. MurE is a protein involved in the peptidoglycan biosynthetic pathway. The lytic profiles of in vivo- and in vitro-grown cells suspended in distilled water were compared; the former was found to be slightly less sensitive to lysis. Ultrathin sections of both cells observed under the transmission electron microscope revealed that in contrast to the usual wavy discontinuous membrane structure of the in vitro-grown cells, in vivo-grown cells had a more rigid, clearly visible double-layered structure. The
V. cholerae murE
gene was cloned and sequenced. The sequence contained an open reading frame of 1,488 nucleotides with its own ribosome-binding site. A plasmid containing the
murE
gene of
V. cholerae
was transformed into
V. cholerae
569B, and a transformed strain, 569BME, containing the plasmid was obtained. Ultrathin sections of 569BME viewed under a transmission electron microscope revealed a slightly more rigid cell wall than that of wild-type 569B. When
V. cholerae
569B and 569BME cells were injected separately into ligated rabbit ileal loops, the transformed cells had a preference for growth in the ileal loops versus laboratory conditions.
Expression Analysis of the Yersiniabactin Receptor Gene
fyuA
and the Heme Receptor
hemR
of
Yersinia enterocolitica
In Vitro and In Vivo Using the Reporter Genes for Green Fluorescent Protein and Luciferase
Authors: Jacobi Christoph A. , Gregor Sebastian , Rakin Alexander , Heesemann Jürgen 
Published: July 2002

ABSTRACT

The enteropathogenic
Yersinia enterocolitica
strains have several systems for scavenging iron from their environment. We have studied the expression of the
fyuA
gene, which encodes the outer membrane receptor for the siderophore yersiniabactin (Ybt), and the
hemR
gene, which encodes the receptor for heme, using the reporter genes
gfp
(encoding green fluorescent protein) and
luc
(encoding firefly luciferase). To study gene expression in vitro as well as in vivo, we have constructed several translational reporter gene fusions to monitor simultaneously expression of
fyuA
and
hemR
or expression of one gene by a
gfp
-
luc
tandem reporter. Results of the in vitro expression analysis (liquid media) indicated that
fyuA
and
hemR
are strongly derepressed under iron starvation conditions, resulting in strong fluorescence and/or luminescence at 27°C. In the in vivo BALB/C mouse infection model, tissue-specific expression of
fyuA
and
hemR
reporter fusions was observed. Surprisingly,
fyuA
and
hemR
reporter constructs were weakly expressed by yersiniae located in the liver and intestinal lumen, whereas strong expression was found for yersiniae in the peritoneal cavity and moderate expression was found in the spleen. Strikingly, yersiniae carrying
fyuA
or
hemR
reporter fusions exhibited threefold-stronger signals when grown in the peritoneal cavity of mice than those growing under iron derepression in vitro. This hyperexpression suggests that besides Fur derepression, additional activators may be involved in the enhanced expression of
fyuA
and
hemR
under peritoneal growth conditions. Differential expression of the
fyuA
and
hemR
reporter fusions could not be observed, suggesting similar regulation of
fyuA
and
hemR
in the mouse infection model.
Vacuolating Cytotoxin of
Helicobacter pylori
Plays a Role during Colonization in a Mouse Model of Infection
Authors: Salama Nina R. , Otto Glen , Tompkins Lucy , Falkow Stanley 
Published: July 2002

ABSTRACT

Helicobacter pylori
, the causative agent of gastritis and ulcer disease in humans, secretes a toxin called VacA (vacuolating cytotoxin) into culture supernatants. VacA was initially characterized and purified on the basis of its ability to induce the formation of intracellular vacuoles in tissue culture cells.
H. pylori
strains possessing different alleles of
vacA
differ in their ability to express active toxin. Those strains expressing higher toxin levels are correlated with more severe gastric disease. However, the specific role(s) played by VacA during the course of infection and disease is not clear. We have used a mouse model of
H. pylori
infection to begin to address this role. A null mutation of
vacA
compromises
H. pylori
in its ability to initially establish infection. If an infection by a
vacA
mutant is established, the bacterial load and degree of inflammation are similar to those associated with an isogenic wild-type strain. Thus, in this infection model,
vacA
plays a role in the initial colonization of the host, suggesting that strains of
H. pylori
expressing active alleles of
vacA
may be better adapted for host-to-host transmission.
Fate ofMycobacterium tuberculosiswithin Murine Dendritic Cells
Authors: Bodnar Kendra A. , Serbina Natalya V. , Flynn JoAnne L. 
Published: July 2002

ABSTRACTThe interaction of microbes with dendritic cells (DCs) is likely to have an enormous impact on the initiation of the immune response against a pathogen. In this study, we compared the interaction ofMycobacterium tuberculosiswith murine bone marrow-derived DCs and macrophages (Mφ) in vitro.M. tuberculosisgrew equally well within nonactivated DCs and Mφ. Activation of DCs and Mφ with gamma interferon and lipopolysaccharide inhibited the growth of the intracellular bacteria in a nitric oxide synthase-dependent fashion. However, while this activation enabled Mφ to kill the intracellular bacteria, theM. tuberculosisbacilli within activated DCs were not killed. Thus, DCs could restrict the growth of the intracellular mycobacteria but were less efficient than Mφ at eliminating the infection. These results may have implications for priming immune responses toM. tuberculosis. In addition, they suggest that DCs may serve as a reservoir forM. tuberculosisin tissues, including the lymph nodes and lungs.
Differential Regulation of Bvg-Activated Virulence Factors Plays a Role in
Bordetella pertussis
Pathogenicity
Authors: Kinnear Susan M. , Marques Ryan R. , Carbonetti Nicholas H. 
Published: July 2002

ABSTRACT

Bordetella pertussis
, the causative agent of whooping cough, regulates expression of many virulence factors via a two-component signal transduction system encoded by the
bvgAS
regulatory locus. It has been shown by transcription activation kinetics that several of the virulence factors are differentially regulated.
fha
is transcribed within 10 min following a
bvg
AS-inducing signal, while
prn
is transcribed after 1 h and
ptx
is not transcribed until 2 to 4 h after induction. These genes therefore represent early, intermediate, and late classes of
bvg
-activated promoters, respectively. Although there have been many insightful studies into the mechanisms of BvgAS-mediated regulation, the role that differential regulation of virulence genes plays in
B. pertussis
pathogenicity has not been characterized. We provide evidence that alterations to the promoter regions of
bvg
-activated genes can alter the kinetic pattern of expression of these genes without changing steady-state transcription levels. In addition,
B. pertussis
strains containing these promoter alterations that express either
ptx
at an early time or
fha
at a late time demonstrate a significant reduction in their ability to colonize respiratory tracts in an intranasal mouse model of infection. These data suggest a role for differential regulation of
bvg
-activated genes, and therefore for the BvgAS regulatory system, in the pathogenicity of
B. pertussis
.
LYT1 Protein Is Required for Efficient In Vitro Infection by
Trypanosoma cruzi
Authors: Manning-Cela Rebeca , Cortés Arantxa , González-Rey Elena , Van Voorhis Wesley C. , Swindle John , González Antonio 
Published: July 2002

ABSTRACT

Trypanosoma cruzi
invasion of host cells involves several discrete steps: attachment, parasite internalization mediated by recruitment and fusion of host cell lysosomes, and escape from the parasitophorous vacuole to liberate amastigotes to multiply freely in the cytosol. This report describes the initial characterization of the
LYT1
gene and the demonstration that the gene product is involved in cell lysis and infectivity. Mutational analysis demonstrated that deletion of
LYT1
resulted in attenuation of infection, which was associated with diminished hemolytic activity. Reintroduction of
LYT1
restored infectivity in null mutants, confirming the critical role of LYT1 in infection. Additionally, in vitro stage transition experiments with
LYT1
-deficient lines showed that these parasites converted to extracellular amastigote-like cells and metacyclic trypomastigotes more rapidly than wild-type parasites, suggesting that the diminished infectivity was not a result of the LYT1 deficiency that affected the parasite's ability to complete the life cycle.
Candidate Vaccine against Botulinum Neurotoxin Serotype A Derived from a Venezuelan Equine Encephalitis Virus Vector System
Authors: Lee John S. , Pushko Peter , Parker Michael D. , Dertzbaugh Mark T. , Smith Leonard A. , Smith Jonathan F. 
Published: July 2002

ABSTRACT

A candidate vaccine against botulinum neurotoxin serotype A (BoNT/A) was developed by using a Venezuelan equine encephalitis (VEE) virus replicon vector. This vaccine vector is composed of a self-replicating RNA containing all of the VEE nonstructural genes and
cis
-acting elements and also a heterologous immunogen gene placed downstream of the subgenomic 26S promoter in place of the viral structural genes. In this study, the nontoxic 50-kDa carboxy-terminal fragment (H
C
) of the BoNT/A heavy chain was cloned into the replicon vector (H
C
-replicon). Cotransfection of BHK cells in vitro with the H
C
-replicon and two helper RNA molecules, the latter encoding all of the VEE structural proteins, resulted in the assembly and release of propagation-deficient, H
C
VEE replicon particles (H
C
-VRP). Cells infected with H
C
-VRP efficiently expressed this protein when analyzed by either immunofluorescence or by Western blot. To evaluate the immunogenicity of H
C
-VRP, mice were vaccinated with various doses of H
C
-VRP at different intervals. Mice inoculated subcutaneously with H
C
-VRP were protected from an intraperitoneal challenge of up to 100,000 50% lethal dose units of BoNT/A. Protection correlated directly with serum enzyme-linked immunosorbent assay titers to BoNT/A. The duration of the immunity achieved was tested at 6 months and at 1 year postvaccination, and mice challenged at these times remained refractory to challenge with BoNT/A.
Identification of Novel
Plasmodium gallinaceum
Zygote- and Ookinete-Expressed Proteins as Targets for Blocking Malaria Transmission
Authors: Langer Rebecca C. , Li Fengwu , Vinetz Joseph M. 
Published: July 2002

ABSTRACT

The development of transmission-blocking vaccines is one approach to malaria control. To identify novel
Plasmodium
zygote- and ookinete-secreted proteins as targets of blocking malaria transmission, monoclonal antibodies (MAbs) were produced against parasite-secreted proteins found in
Plasmodium gallinaceum
ookinete culture supernatants. Four MAbs—1A6, 2A5, 2B5, and 4B6—were identified that bound to
P. gallinaceum
zygotes and ookinetes in diverse patterns in terms of spatial localization on parasites, time course of antigen expression, and Western immunoblot patterns. MAbs 2A5 and 4B6 recognized more than one protein band as detected by Western immunoblot of
P. gallinaceum
ookinete supernatants. Beginning at 0 h postfertilization, MAb 2A5 recognized a diverse set of antigens; at 10 h postfertilization, MAb 4B6 recognized several antigens as well. MAb 1A6 recognized a single ∼17-kDa protein, and 2B5 recognized a single ∼32-kDa protein at 15 h postfertilization. In membrane feeding assays to assess the effect of these MAbs on
P. gallinaceum
infectivity for
Aedes aegypti
mosquitoes, the addition of MAbs 1A6 and 2B5 to infectious blood meals significantly inhibited oocyst development in the mosquito midgut. In contrast, MAb 2A5 seemed to enhance infectivity. These results demonstrate that
Plasmodium
ookinetes secrete proteins (in addition to previously characterized chitinases) that may be targets for blocking malaria transmission. Future investigation of ookinete-secreted neutralization-sensitive molecules should provide valuable insight into mechanisms by which ookinetes exit the blood meal, penetrate and transverse the peritrophic matrix, and invade the mosquito midgut epithelium.