bluuebunny/crossref_metadata_2025_split huggingface dataset:
Genetic Evidence that
Legionella pneumophila
RpoS Modulates Expression of the Transmission Phenotype in Both the Exponential Phase and the Stationary Phase
Authors: Bachman Michael A. , Swanson Michele S. 
Published: April 2004

ABSTRACT

The opportunistic pathogen
Legionella pneumophila
alternates between two states: replication within phagocytes and transmission between host amoebae or macrophages. In broth cultures that model this life cycle, during the replication period, CsrA inhibits expression of transmission traits. When nutrients become limiting, the alarmone (p)ppGpp accumulates and the sigma factors RpoS and FliA and the positive activators LetA/S and LetE promote differentiation to the transmissible form. Here we show that when cells enter the postexponential growth phase, RpoS increases expression of the transmission genes
fliA
,
flaA
, and
mip
, factors
L. pneumophila
needs to establish a new replication niche. In contrast, in exponential (E)-phase cells whose (p)ppGpp levels are low,
rpoS
inhibits expression of transmission traits, on the basis of three separate observations. First,
rpoS
RNA levels peak in the E phase, suggestive of a role for RpoS during replication. Second, in multiple copies,
rpoS
decreases the amounts of
csrA
,
letE
,
fliA
, and
flaA
transcripts and inhibits the transmission traits of motility, infectivity, and cytotoxicity. Third,
rpoS
blocks expression of cytotoxicity and motility by E-phase bacteria that have been induced to express the LetA activator ectopically. The data are discussed in the context of a model in which the alarmone (p)ppGpp enables RpoS to outcompete other sigma factors for binding to RNA polymerase to promote transcription of transmission genes, while LetA/S acts in parallel to relieve CsrA posttranscriptional repression of the transmission regulon. By coupling transcriptional and posttranscriptional control pathways, intracellular
L. pneumophila
could respond to stress by rapidly differentiating to a transmissible form.
Involvement of Lipoprotein NlpI in the Virulence of Adherent Invasive
Escherichia coli
Strain LF82 Isolated from a Patient with Crohn's Disease
Authors: Barnich Nicolas , Bringer Marie-Agnès , Claret Laurent , Darfeuille-Michaud Arlette 
Published: April 2004

ABSTRACT

Escherichia coli
strain LF82 recovered from a chronic lesion of a patient with Crohn's disease (CD) is able to adhere to and invade cultured intestinal epithelial cells and to replicate within macrophages. One mutant selected for its impaired ability to invade epithelial cells had an insertion of a Tn
phoA
transposon within the
nlpI
gene encoding the lipoprotein NlpI. A NlpI-negative isogenic mutant showed a 35-fold decrease in its ability to adhere to and a 45-fold decrease in its ability to invade Intestine-407 cells, but its ability to survive and to replicate within macrophages was similar to that of wild-type strain LF82. In addition, this mutant did not express flagella and synthesized very small amounts of type 1 pili. Downregulation of type 1 pili in the NlpI-negative mutant resulted from a preferential switch toward the OFF position of the invertible DNA element located upstream of the
fim
operon. The FimB and FimE recombinases act in concert to control the switch, and a large decrease in
fimB
and
fimE
mRNA levels was observed. The absence of flagellar structures correlated with a drastic 19-fold decrease in the
fliC
mRNA level, regardless of the FlhD
2
C
2
transcriptional regulator and of the σ
28
transcription factor. The key role of NlpI in virulence is independent of type 1 pili and motility, since induced type 1 pilus expression and/or forced contact between bacteria and intestinal epithelial cells did not restore the ability of the NlpI mutant to adhere to and to invade intestinal epithelial cells.
Caspase-8 Activation Precedes Alterations of Mitochondrial Membrane Potential during Monocyte Apoptosis Induced by Phagocytosis and Killing of
Staphylococcus aureus
Authors: Weęglarczyk Kazimierz , Baran Jarosław , Zembala Marek , Pryjma Juliusz 
Published: April 2004

ABSTRACT

Human peripheral blood monocytes become apoptotic following phagocytosis and killing of
Staphylococcus aureus
. Although this type of monocyte apoptosis is known to be initiated by Fas-Fas ligand (FasL) interactions, the downstream signaling pathway has not been determined. In this work the involvement of mitochondria and the kinetics of caspase-8 and caspase-3 activation after phagocytosis of
S. aureus
were studied. Caspase-8 activity was measured in cell lysates by using the fluorogenic substrate Ac-IETD-AFC. Active caspase-3 levels and mitochondrial membrane potential (Δψ
m
) were measured in whole cells by flow cytometry using monoclonal antibodies reacting with activated caspase-3 and chloromethyl-X-rosamine, respectively. The results show that caspase-8 was activated shortly after phagocytosis of bacteria. Caspase-8 activation was followed by progressive disruption of Δψ
m
, which is associated with the production of reactive oxygen intermediates. The irreversible caspase-8 inhibitor zIETD-FMK prevented the disruption of Δψ
m
and the release of cytochrome
c
from
S. aureus
-exposed monocytes. Caspase-3 activation occurred following disruption of Δψ
m
. These results strongly suggest that apoptosis of monocytes that have phagocytosed and killed
S. aureus
is driven by the Fas-FasL-initiated pathway, which is typical for type II cells.
Impairment of Tetanus-Specific Cellular and Humoral Responses following Tetanus Vaccination in Human Lymphatic Filariasis
Authors: Nookala Suba , Srinivasan Sundaram , Kaliraj Perumal , Narayanan Rangarajan Badri , Nutman Thomas B. 
Published: April 2004

ABSTRACTTo investigate the consequences of the impaired parasite-specific immune response in lymphatic filariasis, the effect of concurrentWuchereria bancroftiinfection on the immune response to tetanus toxoid (TT) following tetanus vaccination was studied in 20 asymptomatic microfilaremic (MF) patients, 20 patients with chronic lymphatic obstruction/elephantiasis (chronic pathology [CP]), and 10 endemic normal (EN) control individuals at baseline and at 3 and 6 months after TT vaccination. Peripheral blood mononuclear cell (PBMC) proliferative responses to TT before vaccination were not significantly different between the EN control and CP groups, but the MF group showed significantly lower baseline proliferative responses to TT compared with either the EN or CP group. Six months following vaccination, the change in proliferative response to TT was significantly greater in the EN and CP groups than in the MF group. This difference in proliferative response was reiterated in the gamma interferon (IFN-γ) response in the EN group, in that they increased IFN-γ production by 400% at 6 months, in contrast to that seen in the filaria-infected groups. In contrast to the IFN-γ responses, PBMCs from the MF group produced significantly increased levels of TT-specific IL-10 compared with PBMCs from the EN group. Although there was significantly greater TT-specific immunoglobulin G (IgG) production at baseline between the EN and MF groups, postvaccination IgG (and IgG1 isotype) responses did not differ among the groups, whereas TT-specific IgG2, IgG3, and IgG4 were all increased in the EN group compared with the filaria-infected groups. These studies indicate that concurrent infection withW. bancroftican diminish the immune response to an unrelated antigen by a mechanism that is likely to involve IL-10.
Intranasal Immunization with a Colloid-Formulated Bacterial Extract Induces an Acute Inflammatory Response in the Lungs and Elicits Specific Immune Responses
Authors: Rial A. , Lens D. , Betancor L. , Benkiel H. , Silva J. S. , Chabalgoity J. A. 
Published: April 2004

ABSTRACTNonspecific stimulation of lung defenses by repeated oral administration of immunomodulators, such as bacterial extracts, has shown potential for the prevention of respiratory tract infections. Here, we show that intranasal (i.n.) immunization with a bacterial extract formulated as a colloid induces an acute inflammatory response in the lungs characterized by increased production of CCL and CXCL chemokines and a major influx of dendritic cells (DCs) and neutrophils, with a higher proportion of DCs showing an activated phenotype (high CD80/CD86 expression). Cytokine levels measured in bronchoalveolar-lavage samples showed a small increase in the production of tumor necrosis factor alpha and similar levels of the other cytokines measured (interleukin 10 [IL-10], IL-12, and gamma interferon [IFN-γ]) in immunized mice compared with control mice. However, the recall response of primed animals after antigenic challenge induced increased expression of IL-12 and IFN-γ mRNAs in lung homogenates. Overall, all these effects were not due to the lipopolysaccharide content in the bacterial extract. Furthermore, we found that three i.n. doses administered 2 to 3 weeks apart were enough to elicit long-lasting specific serum immunoglobulin G (IgG) and secretory IgA antibody responses. Assessment of IgG subclasses showed a balanced pattern of IgG1-IgG2a responses. The serum total IgE concentrations were also elevated in immunized mice 2 weeks after the third dose, but they significantly decreased soon afterwards. Our results suggest that simple formulations of bacterial extracts administered i.n. are highly immunogenic, eliciting local and systemic immune responses, and may serve as the basis for cost-effective immunotherapies for the prevention and treatment of respiratory infections.
Dialysis Unmasks the Fungicidal Properties of Glandular Salivary Secretions
Authors: Helmerhorst Eva J. , Flora Bianca , Troxler Robert F. , Oppenheim Frank G. 
Published: April 2004

ABSTRACT

Several salivary proteins exhibit fungicidal activity against the opportunistic oral pathogen
Candida albicans
when they are tested as pure proteins in vitro. However, salivary secretions that are examined by the same assays either lack or exhibit very low candidacidal activity. Since ionic strength is known to have an inhibitory effect on the fungicidal activities of some proteins, parotid secretion was subjected to dialysis with membranes having molecular weight cutoffs (MWCOs) of 500, 1,000, 10,000, and 25,000. Dialysis with membranes with MWCOs of ≥1,000 promoted fungicidal activity of parotid secretion, and this activity was dose dependent. The addition of sodium chloride to dialyzed, fungicidal parotid secretion abolished this activity, indicating that the fungicidal component was salt sensitive. Similar results were obtained with submandibular and sublingual secretions. Polyacrylamide gel electrophoresis under native and denaturing conditions was used to analyze the composition of the dialysate. Unexpectedly, proteins with MWs much lower than the nominal MWCOs of the membranes were not lost during dialysis. Among the retained proteins, the two fractions with MWs of approximately 17,000 and 4,000 exhibited fungicidal activity. These results are consistent with the presence of lysozyme and histatins, respectively, which may represent the major candidacidal capacity of dialyzed parotid secretion.
Enhanced Mucosal Delivery of Antigen with Cell Wall Mutants of Lactic Acid Bacteria
Authors: Grangette Corinne , Müller-Alouf Heide , Hols Pascal , Goudercourt Denise , Delcour Jean , Turneer Mireille , Mercenier Annick 
Published: April 2004

ABSTRACTThe potential of recombinant lactic acid bacteria (LAB) to deliver heterologous antigens to the immune system and to induce protective immunity has been best demonstrated by using the C subunit of tetanus toxin (TTFC) as a model antigen. Two types of LAB carriers have mainly been used,Lactobacillus plantarumandLactococcus lactis, which differ substantially in their abilities to resist passage through the stomach and to persist in the mouse gastrointestinal tract. Here we analyzed the effect of a deficiency in alanine racemase, an enzyme that participates in cell wall synthesis, in each of these bacterial carriers. Recombinant wild-type and mutant strains ofL. plantarumNCIMB8826 andL. lactisMG1363 producing TTFC intracellularly were constructed and used in mouse immunization experiments. Remarkably, we observed that the two cell wall mutant strains were far more immunogenic than their wild-type counterparts when the intragastric route was used. However, intestinal TTFC-specific immunoglobulin A was induced only after immunization with the recombinantL. plantarummutant strain. Moreover, the alanine racemase mutant of either LAB strain allowed induction of a much stronger serum TTFC-specific immune response after immunization via the vagina, which is a quite different ecosystem than the gastrointestinal tract. The design and use of these mutants thus resulted in a major improvement in the mucosal delivery of antigens exhibiting vaccine properties.
Bovine Leukocyte Antigen Major Histocompatibility Complex Class IIDRB3*2703andDRB3*1501Alleles Are Associated with Variation in Levels of Protection againstTheileria parvaChallenge following Immunization with the Sporozoite p67 Antigen
Authors: Ballingall Keith T. , Luyai Anthony , Rowlands G. John , Sales Jill , Musoke Anthony J. , Morzaria Subash P. , McKeever Declan J. 
Published: April 2004

ABSTRACTInitial laboratory trials of an experimental subunit vaccine againstTheileria parvabased on the 67-kDa major sporozoite surface antigen revealed a range of responses to challenge. We have analyzed convergence in seven sets of monozygotic twins which suggests that genetic factors may have an influence in determining the degree of protection provided by p67 immunization. In addition, we have examined whether allelic diversity at major histocompatibility complex class II loci influences protection. Analysis of bovine leukocyte antigenDRB3diversity in 201 animals identified significant associations with vaccine success (DRB3*2703;P= 0.027) and vaccine failure (DRB3*1501;P= 0.013). Furthermore,DRB3*2703was associated with the likelihood of immunized animals showing little to no clinical signs of disease following challenge. We discuss the acquired and innate immune mechanisms that may be behind the associations described here.
Mucosal and Cellular Immune Responses Elicited by RecombinantLactococcus lactisStrains Expressing Tetanus Toxin Fragment C
Authors: Robinson K. , Chamberlain L. M. , Lopez M. C. , Rush C. M. , Marcotte H. , Le Page R. W. F. , Wells J. M. 
Published: April 2004

ABSTRACTThe mucosal and cellular responses of mice were studied, following mucosal-route administration of recombinantLactococcus lactisexpressing tetanus toxin fragment C (TTFC), which is a known immunogen protective against tetanus. A TTFC-specific T-cell response with a mixed profile of T-helper (Th) subset-associated cytokines was elicited in the intestine, with a Th2 bias characteristic of a mucosal response. These results correlated with the humoral response, where equivalent titers of anti-TTFC immunoglobulin G1 (IgG1) and IgG2a in serum were accompanied by an elevated IgA-specific response at more than one mucosal site. The route of vaccination had an important role in determining the immune response phenotype, as evidenced by the fact that an IgG1-biased subclass profile was obtained when lactococci were administered parenterally. Stimulation of splenic or mesenteric lymph node cells with lactococci resulted in their proliferation and the secretion of gamma interferon via antigen-specific and innate immune mechanisms. The data therefore provide further evidence of the potential of recombinant lactococcal vaccines for inducing systemic and mucosal immune responses.
Differential Regulation of β-Defensin Gene Expression duringCryptosporidium parvumInfection
Authors: Zaalouk Tarek K. , Bajaj-Elliott Mona , George John T. , McDonald Vincent 
Published: April 2004

ABSTRACTInvasion of enterocytes by pathogenic microbes evokes both innate and adaptive immune responses, and microbial pathogens have developed strategies to overcome the initial host immune defense. β-Defensins are potentially important endogenous antibiotic-like effectors of innate immunity expressed by intestinal epithelia. In this study, the interplay between the enteric protozoan parasiteCryptosporidium parvumand host epithelial β-defensin expression was investigated. Using human and murine models of infection, we demonstrated thatC. parvuminfection differentially regulates β-defensin gene expression. Downregulation of murine β-defensin-1 mRNA and protein was observed in both in vitro and in vivo models of infection. Infection of the human colonic HT29 cell line with the parasite resulted in differential effects on various members of the defensin gene family. Partial reduction in human β-defensin-1 (hBD-1), induction of hBD-2, and no effect on hBD-3 gene expression was observed. Recombinant hBD-1 and hBD-2 peptides exhibited significant antimicrobial activity againstC. parvumsporozoites in vitro. These findings demonstrate thatC. parvuminfection of enterocytes may affect the expression of various defensins in different ways and suggest that the overall outcome of the effect of antimicrobial peptides on early survival of the parasite may be complex.
Binding of Hematin by a New Class of Glutathione Transferase from the Blood-Feeding Parasitic NematodeHaemonchus contortus
Authors: van Rossum Arjan J. , Jefferies James R. , Rijsewijk Frans A. M. , LaCourse E. James , Teesdale-Spittle Paul , Barrett John , Tait Andrew , Brophy Peter M. 
Published: April 2004

ABSTRACTThe phase II detoxification system glutathione transferase (GST) is associated with the establishment of parasitic nematode infections within the gastrointestinal environment of the mammalian host. We report the functional analysis of a GST from an important worldwide parasitic nematode of small ruminants,Haemonchus contortus. This GST shows limited activity with a range of classical GST substrates but effectively binds hematin. The high-affinity binding site for hematin was not present in the GST showing the most identity, CE07055 from the free-living nematodeCaenorhabditis elegans. This finding suggests that the high-affinity binding of hematin may represent a parasite adaptation to blood or tissue feeding from the host.
Functional Transfer of
Salmonella
Pathogenicity Island 2 to
Salmonella bongori
and
Escherichia coli
Authors: Hansen-Wester Imke , Chakravortty Dipshikha , Hensel Michael 
Published: April 2004

ABSTRACT

The type III secretion system (T3SS) encoded by the
Salmonella
pathogenicity island 2 (SPI2) has a central role in systemic infections by
Salmonella enterica
and for the intracellular phenotype. Intracellular
S. enterica
uses the SPI2-encoded T3SS to translocate a set of effector proteins into the host cell, which modify host cell functions, enabling intracellular survival and replication of the bacteria. We sought to determine whether specific functions of the SPI2-encoded T3SS can be transferred to heterologous hosts
Salmonella bongori
and
Escherichia coli
Mutaflor, species that lack the SPI2 locus and loci encoding effector proteins. The SPI2 virulence locus was cloned and functionally expressed in
S. bongori
and
E. coli
. Here, we demonstrate that
S. bongori
harboring the SPI2 locus is capable of secretion of SPI2 substrate proteins under culture conditions, as well as of translocation of effector proteins under intracellular conditions. An SPI2-mediated cellular phenotype was induced by
S. bongori
harboring the SPI2 if the
sifA
locus was cotransferred. An interference with the host cell microtubule cytoskeleton, a novel SPI2-dependent phenotype, was observed in epithelial cells infected with
S. bongori
harboring SPI2 without additional effector genes.
S. bongori
harboring SPI2 showed increased intracellular persistence in a cell culture model, but SPI2 transfer was not sufficient to confer to
S. bongori
systemic pathogenicity in a murine model. Transfer of SPI2 to heterologous hosts offers a new tool for the study of SPI2 functions and the phenotypes of individual effectors.
Macrophages Release Tumor Necrosis Factor Alpha and Interleukin-12 in Response to Intracellular
Bacillus anthracis
Spores
Authors: Pickering Alison K. , Merkel Tod J. 
Published: April 2004

ABSTRACT

Herein we report that infection of a murine macrophage cell line with
Bacillus anthracis
results in the production of tumor necrosis factor alpha and interleukin-12 (IL-12). When infected with
B. anthracis
spores in combination with lipopolysaccharide, macrophages release increased amounts of IL-12. We found no evidence of inhibition of cytokine responses in macrophages infected with
B. anthracis
spores.
Pneumococcal Surface Protein C Contributes to Sepsis Caused byStreptococcus pneumoniaein Mice
Authors: Iannelli Francesco , Chiavolini Damiana , Ricci Susanna , Oggioni Marco Rinaldo , Pozzi Gianni 
Published: April 2004

ABSTRACTThe role of pneumococcal surface protein C (PspC; also called SpsA, CbpA, and Hic) in sepsis byStreptococcus pneumoniaewas investigated in a murine infection model. ThepspCgene was deleted in strains D39 (type 2) and A66 (type 3), and the mutants were tested by being injected intravenously into mice. The animals infected with the mutant strains showed a significant increase in survival, with the 50% lethal dose up to 250-fold higher than that for the wild type. Our findings indicate that PspC affords a decisive contribution to sepsis development.
A CLEAR AND PRESENT DANGER: "WAHHABISM" AS A RHETORICAL FOIL
Authors: Knysh Alexander 
Published: April 2004

Abstract"We shall not return to the state anterior to discourse—in which nothing has yet been said, and in which things are only just beginning to emerge out of the grey light; and we shall not pass beyond discourse in order to rediscover the forms that it has created and left behind it; we shall remain, or try to remain, at the level of discourse itself…A task consists of not—of no longer—treating discourses as groups of signs (signifying elements referring to contents or representations) but as practices that systematically form the objects of which they speak."
Structure of a population of the lizard Podarcis bocagei in northwest Spain: variations in age distribution, size distribution and sex ratio
Authors: Galán Pedro 
Published: April 2004

AbstractMark-recapture techniques were used to investigate population size, age distribution, size distribution and sex ratio in a population of the lacertid lizard Podarcis bocagei in an abandoned gravel pit in northwest Spain. The study was carried out over a 2-year period. Despite relatively high maximum longevity, the population age distribution was characteristic of small, short-lived lizard species (i.e., there was a relatively high proportion of immature individuals). Population size declined over the study period, largely because of a drop in the number of immature animals: this may be partially attributable to density-dependent factors, but was probably due largely to a decline in habitat favourability as a result of colonisation of the study site by vegetation. The sex ratio was significantly female-biased in all cohorts studied, not only among adults but also among juveniles and sub-adults. However, sex ratio at hatching (as investigated by laboratory hatching of clutches laid by captured pregnant females) did not differ significantly from one-to-one. There was no difference found in survival probabilities between males and females. The observed bias in sex ratio must therefore be attributed to between-sex differences in net emigration.