Biomedical subjects

Anne-Laure Page

Publications and source records attributed to Anne-Laure Page.

9 recordsLinked to original sources

PubMed2005

The Shigella flexneri effector OspG interferes with innate immune responses by targeting ubiquitin-conjugating enzymes.

Bacteria of Shigella spp. are responsible for shigellosis in humans. They use a type III secretion system to inject effector proteins into host cells and induce their entry into epithelial cells or trigger apoptosis in macrophages. We present evidence that the effector OspG is a protein kinase that binds various ubiquitinylated ubiquitin-conjugating enzymes, including UbcH5, which belongs to the stem cell factor SCF(beta-TrCP) complex promoting ubiquitination of phosphorylated inhibitor of NF-kappaB type alpha (phospho-IkappaBalpha). Transfection experiments indicated that OspG can prevent phospho-IkappaBalpha degradation and NF-kappaB activation induced by TNF-alpha stimulation. Infection of epithelial cells by the S. flexneri wild-type strain, but not an ospG mutant, led to accumulation of phospho-IkappaBalpha, consistent with OspG inhibiting SCF(beta-TrCP) activity. Upon infection of ileal loops in rabbits, the ospG mutant induced a stronger inflammatory response than the wild-type strain. This finding indicates that OspG negatively controls the host innate response induced by S. flexneri upon invasion of the epithelium.

Animals↗

PubMed2005

A mass vaccination campaign targeting adults and children to prevent typhoid fever in Hechi; expanding the use of Vi polysaccharide vaccine in southeast China: a cluster-randomized trial.

BACKGROUND: One of the goals of this study was to learn the coverage, safety and logistics of a mass vaccination campaign against typhoid fever in children and adults using locally produced typhoid Vi polysaccharide (PS) and group A meningococcal PS vaccines in southern China. METHODS: The vaccination campaign targeted 118,588 persons in Hechi, Guangxi Province, aged between 5 to 60 years, in 2003. The study area was divided into 107 geographic clusters, which were randomly allocated to receive one of the single-dose parenteral vaccines. All aspects regarding vaccination logistics, feasibility and safety were documented and systematically recorded. Results of the logistics, feasibility and safety are reported. RESULTS: The campaign lasted 5 weeks and the overall vaccination coverage was 78%. On average, the 30 vaccine teams gave immunizations on 23 days. Vaccine rates were higher in those aged < or = 15 years (90%) than in adolescents and young adults (70%). Planned mop-up activities increased the coverage by 17%. The overall vaccine wastage was 11%. The cold chain was maintained and documented. 66 individuals reported of adverse events out of all vaccinees, where fever (21%), malaise (19%) and local redness (19%) were the major symptoms; no life-threatening event occurred. Three needle-sharp events were reported. CONCLUSION: The mass immunization proved feasible and safe, and vaccine coverage was high. Emphasis should be placed on: injection safety measures, community involvement and incorporation of mop-up strategies into any vaccination campaign. School-based and all-age Vi mass immunizations programs are potentially important public health strategies for prevention of typhoid fever in high-risk populations in southern China.

Adolescent↗

PubMed2005

A multi-country cluster randomized controlled effectiveness evaluation to accelerate the introduction of Vi polysaccharide typhoid vaccine in developing countries in Asia: rationale and design.

Phase-III vaccine efficacy trials typically employ individually randomized designs intended to ensure that measurements of vaccine protective efficacy reflect only direct vaccine effects. As a result, decisions about introducing newly licensed vaccines into public health programmes often fail to consider the substantially greater protection that may occur when a vaccine is deployed in public health programmes, due to the combination of direct plus indirect vaccine protective effects. Vaccine total protection can be better evaluated with cluster randomized trials. Such a design was considered to generate policy relevant data to accelerate the rationale introduction of the licensed typhoid fever Vi polysaccharide (PS) vaccine in Asia by the Diseases of the Most Impoverished (DOMI) typhoid fever programme. The DOMI's programme multi-country study is one of the largest cluster randomized vaccine trials ever mounted in Asia, which includes approximately 200,000 individuals. Its main objective is to determine the effectiveness of a licensed Vi PS vaccine. The rationale and design of this study are discussed. Preliminary results are presented that determined the final planning of the trial before immunization. Important methodological and practical issues regarding vaccine cluster randomized designs are illustrated.

Adolescent↗

PubMed2004

The role of epidemiology in the introduction of vi polysaccharide typhoid fever vaccines in Asia.

Despite the availability of at least two licensed typhoid fever vaccines--injectable sub-unit Vi polysaccharide vaccine and live, oral Ty21a vaccine--for the last decade, these vaccines have not been widely introduced in public-health programmes in countries endemic for typhoid fever. The goal of the multidisciplinary DOMI (Diseases of the Most Impoverished) typhoid fever programme is to generate policy-relevant data to support public decision-making regarding the introduction of Vi polysaccharide typhoid fever immunization programmes in China, Viet Nam, Pakistan, India, Bangladesh, and Indonesia. Through epidemiological studies, the DOMI Programme is generating these data and is offering a model for the accelerated, rational introduction of new vaccines into health programmes in low-income countries. Practical and specific examples of the role of epidemiology are described in this paper. These examples cover: (a) selection of available typhoid fever vaccines to be introduced in the programme, (b) generation of policy-relevant data, (c) providing the 'backbone' for the implementation of other multidisciplinary projects, and (d) generation of unexpected but useful information relevant for the introduction of vaccines. Epidemiological studies contribute to all stages of development of vaccine evaluation and introduction.

Asia↗

PubMed2003

The various and varying roles of specific chaperones in type III secretion systems.

The type III secretion pathway is used by numerous Gram-negative pathogenic bacteria to deliver proteins within the membrane or the cytoplasm of eukaryotic cells with which these bacteria interact. Secretion is regulated by external signals. This requires that, before being secreted, proteins are stored in the cytoplasm where they need to be stabilised, separated from other interaction partners, and maintained in a secretion-competent state. Specialised, energy-independent chaperones play various roles in these functions by associating in the cytoplasm with proteins before their secretion. Some chaperones are also directly involved in modulating transcription in response to secretion.

Binding Sites↗

PubMed2003

MxiK and MxiN interact with the Spa47 ATPase and are required for transit of the needle components MxiH and MxiI, but not of Ipa proteins, through the type III secretion apparatus of Shigella flexneri.

The type III secretion (TTS) pathway is used by numerous Gram-negative pathogens to inject virulence factors into eukaryotic cells. The Shigella flexneri TTS apparatus (TTSA) spans the bacterial envelope and its assembly requires the products of approximately 20 mxi and spa genes. We present a functional analysis of the mxiK, mxiN and mxiL genes. Inactivation of mxiK and mxiN, but not mxiL, resulted in the assembly of a non-functional TTSA that lacked the outer needle. The amounts of needle components MxiH and MxiI were drastically reduced in mxiK and mxiN mutants and in the secretion defective spa47 mutant, indicating that MxiH and MxiI are degraded if they do not transit through the TTSA. Remarkably, expression of MxiH-His in the mxiN mutant and MxiI-His in the mxiK mutant restored assembly of a functional TTSA, as shown by the ability of these strains to enter into epithelial cells and to secrete Ipa proteins in response to activation by Congo red. Using a two-hybrid screen in yeast and immunoprecipitation assays from S. flexneri extracts, we identified interactions between MxiK and Spa33 and Spa47 and between MxiN and Spa33 and Spa47. These results suggest that transit of the needle components MxiH and MxiI through the TTSA involves the concerted action of the cytoplasmic proteins Spa47, Spa33, MxiK and MxiN. They also show that neither MxiK nor MxiN are absolutely required for secretion of Ipa proteins, provided that the TTSA is correctly assembled.

Adenosine Triphosphatases↗

PubMed2002

Spa15 of Shigella flexneri, a third type of chaperone in the type III secretion pathway.

The type III secretion (TTS) pathway is used by numerous Gram-negative pathogens to inject virulence factors into eukaryotic cells. In addition to a functional TTS apparatus, secretion of effector proteins depends upon specific chaperones. Using a two-hybrid screen in yeast and a co-purification assay in Shigella flexneri, we demonstrated that Spa15, which is encoded by an operon for components of the TTS apparatus, is associated in the cytoplasm with three proteins that are secreted by the TTS pathway, IpaA, IpgB1 and OspC3. Spa15 was found to be necessary for stability of IpgB1 but not IpaA, and for secretion of IpaA molecules that were stored in the cytoplasm but not those that were synthesized while the secretion apparatus was active. The ability of Spa15 to associate with several non-homologous secreted proteins, the presence of Spa15 homologues in other TTS systems and the location of the corresponding genes within operons for components of the TTS apparatus suggest that Spa15 belongs to a new class of TTS chaperones.

Amino Acid Sequence↗

PubMed2002

Regulation of transcription by the activity of the Shigella flexneri type III secretion apparatus.

The virulence plasmid-encoded type III secretion system of Shigella flexneri consists of the Mxi-Spa secretion apparatus, secreted proteins IpaA-D and IpgD involved in entry of bacteria into epithelial cells,cytoplasmic chaperones IpgC and IpgE and 15 other secreted proteins of unknown function, including VirA and members of the IpaH family. The activity of the Mxi-Spa apparatus is regulated by external signals, and transcription of virA and IpaH genes is specifically induced in conditions of active secretion. We present genetic evidence that regulation of these genes involves both MxiE, the transcriptional activator of the AraC family encoded by the mxi operon, and IpgC, the chaperone for IpaB and IpaC. We also show that together MxiE and IpgC are sufficient to activatevirA and IpaH 9.8 promoters in Escherichia coli. InS. flexneri, increasing the expression of IpgC led to a concomitant increase in IpaH production in conditions of non-secretion. This suggests that the activity of secretion is sensed by the presence of free IpgC, which acts as a coactivator to allow MxiE to activate transcription at its target promoters.

Animals↗

PubMed2002

Chaperones of the type III secretion pathway: jacks of all trades.

The type III secretion (TTS) pathway is used by many Gram-negative bacteria to inject virulence proteins into cells of their host. The activity of the TTS apparatus is controlled by external signals and, in certain conditions, production and secretion are not coupled. Storage of some proteins before secretion involves their association with specific chaperones. Three classes of TTS chaperones have been distinguished according to whether they associate with: (i) one; (ii) several effector proteins; or (iii) the two translocators that allow passage of effectors across the membrane of eukaryotic cells. These chaperones are required for stabilization of their substrate(s) and prevention of their premature interactions with other partners during storage. They also play a role in secretion of their substrate(s). Some chaperones are also involved in transcriptional regulation of certain genes in response to the activity of secretion. The flagellar export apparatus is closely related to the TTS apparatus and some proteins of the flagellar export system have also been proposed to be chaperones that prevent premature interactions between the flagellum subunits.

Bacterial Proteins↗