Association with coregulators is the major determinant governing peroxisome proliferator-activated receptor mobility in living cells.

The nucleus is an extremely dynamic compartment, and protein mobility represents a key factor in transcriptional regulation. We showed in a previous study that the diffusion of peroxisome proliferator-activated receptors (PPARs), a family of nuclear receptors regulating major cellular and metabolic functions, is modulated by ligand binding. In this study, we combine fluorescence correlation spectroscopy, dual color fluorescence cross-correlation microscopy, and fluorescence resonance energy transfer to dissect the molecular mechanisms controlling PPAR mobility and transcriptional activity in living cells. First, we bring new evidence that in vivo a high percentage of PPARs and retinoid X receptors is associated even in the absence of ligand. Second, we demonstrate that coregulator recruitment (and not DNA binding) plays a crucial role in receptor mobility, suggesting that transcriptional complexes are formed prior to promoter binding. In addition, association with coactivators in the absence of a ligand in living cells, both through the N-terminal AB domain and the AF-2 function of the ligand binding domain, provides a molecular basis to explain PPAR constitutive activity.

Chlamydiaceae and Chlamydia-like organisms in free-living small mammals in Europe and Afghanistan.

Few data are available on the occurrence of chlamydial infections in wild small mammals. We investigated the significance of free-living small mammals as reservoirs or transmission hosts for microorganisms of the phylum/class Chlamydiae. We obtained 3,664 tissue samples from 911 animals in Switzerland, Germany, Austria, the Czech Republic, and Afghanistan. Samples included internal organs (n = 3,652) and feces (n = 12) from 679 rodents (order Rodentia) and 232 insectivores (order Soricomorpha) and were tested by three TaqMan® real-time PCRs specific for members of the family Chlamydiaceae and selected Chlamydia-like organisms such as Parachlamydia spp. and Waddlia spp. Only one of 911 (0.11%) animals exhibited a questionable positive result by Chlamydiaceae-specific real-time PCR. Five of 911 animals were positive by specific real-time PCR for Parachlamydia spp. but could not be confirmed by quantitative PCR targeting the Parachlamydia acanthamoebae secY gene (secY qPCR). One of 746 animals (0.13%) was positive by real-time PCR for Waddlia chondrophila. This result was confirmed by Waddlia secY qPCR. This is the first detection of Chlamydia-like organisms in small wildlife in Switzerland. Considering previous negative results for Chlamydiaceae in wild ruminant species from Switzerland, these data suggest that wild small mammals are unlikely to be important carriers or transport hosts for Chamydiaceae and Chlamydia-like organisms.

Repeated exposure to Lutzomyia intermedia sand fly saliva induces local expression of interferon-inducible genes both at the site of injection in mice and in human blood.

During a blood meal, Lutzomyia intermedia sand flies transmit Leishmania braziliensis, a parasite causing tegumentary leishmaniasis. In experimental leishmaniasis, pre-exposure to saliva of most blood-feeding sand flies results in parasite establishment in absence of any skin damages in mice challenged with dermotropic Leishmania species together with saliva. In contrast, pre-immunization with Lu. intermedia salivary gland sonicate (SGS) results in enhanced skin inflammatory exacerbation upon co-inoculation of Lu. intermedia SGS and L. braziliensis. These data highlight potential unique features of both L. braziliensis and Lu. intermedia. In this study, we investigated the genes modulated by Lu. intermedia SGS immunization to understand their potential impact on the subsequent cutaneous immune response following inoculation of both SGS and L. braziliensis. The cellular recruitment and global gene expression profile was analyzed in mice repeatedly inoculated or not with Lu. intermedia. Microarray gene analysis revealed the upregulation of a distinct set of IFN-inducible genes, an immune signature not seen to the same extent in control animals. Of note this INF-inducible gene set was not induced in SGS pre-immunized mice subsequently co-inoculated with SGS and L. braziliensis. These data suggest the parasite prevented the upregulation of this Lu. intermedia saliva-related immune signature. The presence of these IFN-inducible genes was further analyzed in peripheral blood mononuclear cells (PBMCs) sampled from uninfected human individuals living in a L. braziliensis-endemic region of Brazil thus regularly exposed to Lu. intermedia bites. PBMCs were cultured in presence or absence of Lu. intermedia SGS. Using qRT-PCR we established that the IFN-inducible genes induced in the skin of SGS pre-immunized mice, were also upregulated by SGS in PBMCs from human individuals regularly exposed to Lu. intermedia bites, but not in PBMCs of control subjects. These data demonstrate that repeated exposure to Lu. intermedia SGS induces the expression of potentially host-protective IFN-inducible genes.

Towards robust network based complex systems : from evolutionary cellular automata to biological models

Abstract Sitting between your past and your future doesn't mean you are in the present. Dakota Skye Complex systems science is an interdisciplinary field grouping under the same umbrella dynamical phenomena from social, natural or mathematical sciences. The emergence of a higher order organization or behavior, transcending that expected of the linear addition of the parts, is a key factor shared by all these systems. Most complex systems can be modeled as networks that represent the interactions amongst the system's components. In addition to the actual nature of the part's interactions, the intrinsic topological structure of underlying network is believed to play a crucial role in the remarkable emergent behaviors exhibited by the systems. Moreover, the topology is also a key a factor to explain the extraordinary flexibility and resilience to perturbations when applied to transmission and diffusion phenomena. In this work, we study the effect of different network structures on the performance and on the fault tolerance of systems in two different contexts. In the first part, we study cellular automata, which are a simple paradigm for distributed computation. Cellular automata are made of basic Boolean computational units, the cells; relying on simple rules and information from- the surrounding cells to perform a global task. The limited visibility of the cells can be modeled as a network, where interactions amongst cells are governed by an underlying structure, usually a regular one. In order to increase the performance of cellular automata, we chose to change its topology. We applied computational principles inspired by Darwinian evolution, called evolutionary algorithms, to alter the system's topological structure starting from either a regular or a random one. The outcome is remarkable, as the resulting topologies find themselves sharing properties of both regular and random network, and display similitudes Watts-Strogtz's small-world network found in social systems. Moreover, the performance and tolerance to probabilistic faults of our small-world like cellular automata surpasses that of regular ones. In the second part, we use the context of biological genetic regulatory networks and, in particular, Kauffman's random Boolean networks model. In some ways, this model is close to cellular automata, although is not expected to perform any task. Instead, it simulates the time-evolution of genetic regulation within living organisms under strict conditions. The original model, though very attractive by it's simplicity, suffered from important shortcomings unveiled by the recent advances in genetics and biology. We propose to use these new discoveries to improve the original model. Firstly, we have used artificial topologies believed to be closer to that of gene regulatory networks. We have also studied actual biological organisms, and used parts of their genetic regulatory networks in our models. Secondly, we have addressed the improbable full synchronicity of the event taking place on. Boolean networks and proposed a more biologically plausible cascading scheme. Finally, we tackled the actual Boolean functions of the model, i.e. the specifics of how genes activate according to the activity of upstream genes, and presented a new update function that takes into account the actual promoting and repressing effects of one gene on another. Our improved models demonstrate the expected, biologically sound, behavior of previous GRN model, yet with superior resistance to perturbations. We believe they are one step closer to the biological reality.

Sibling rivalry and vocal negotiation in the barn owl Tyto alba

Chez les animaux, les jeunes dépendant des parents durant leur développement sont en compétition pour obtenir la nourriture, qu'ils quémandent par des cris et postures ostentatoires et se disputent physiquement. Les frères et soeurs n'ont pas la même compétitivité, en particulier s'ils diffèrent en âge, et leur niveau de faim fluctue dans le temps. Comme dans tout type de compétition, chacun doit ajuster son investissement aux rivaux, c'est à dire aux besoins et comportements de ses frères et soeurs. Dans le contexte de la famille, selon la théorie de sélection de parentèle, les jeunes bénéficient de leur survie mutuelle et donc de la propagation de la part de gènes qu'ils ont en commun. L'hypothèse de la « négociation frères-soeurs » prédit que, sous certaines conditions, les jeunes négocient entre eux la nourriture, ce qui réduit les coûts de compétition et permet de favoriser les frères et soeurs les plus affamés. La littérature actuelle se focalise sur les signaux de quémande entre enfants et parents et les interactions compétitives frères-soeurs sont étudiées principalement au sein de paires, alors que les nichées ou portées en comprennent souvent de nombreux. Cette thèse vise à mieux comprendre comment et jusqu'à quel point plusieurs jeunes ajustent mutuellement leurs signaux de besoin. C'est une question importante, étant donné que cela influence la répartition de nourriture entre eux, donc la résolution du conflit qui les oppose et à terme leur valeur évolutive. Le modèle d'étude est la chouette effraie (Tyto alba), chez laquelle jusqu'à neufs poussins émettent des milliers de cris chacun par nuit. Ils négocieraient entre eux la prochaine proie indivisible rapportée au nid avant que les parents ne reviennent : un poussin affamé crie plus qu'un autre moins affamé, ce qui dissuade ce dernier de crier en retour et par la suite de quémander la nourriture aux parents. L'investissement optimal correspondrait donc à écarter son frère en permanence vu que l'arrivée des parents est imprévisible, mais à moindre coût. Dans un premier axe, nous avons exploré au sein de dyades les mécanismes acoustiques permettant aux poussins de doser leur effort vocal durant les heures de compétition où ils sont laissés seuls au nid. Nous avons trouvé que les poussins évitent de crier simultanément, ce qui optimiserait la discrimination du nombre et de la durée de leurs cris, lesquels reflètent de façon honnête leur niveau de faim et donc leur motivation. L'alternance des cris paraît particulièrement adaptée au fait que les poussins se fient à des variations temporelles subtiles dans le rythme et la durée de leurs vocalisations pour prendre la parole. En particulier, allonger ses cris tout en criant moins dissuade efficacement le rival de répondre, ce qui permet de monopoliser la parole dans de longs « monologues ». Ces règles seraient universelles puisqu'elles ne dépendent pas de la séniorité, de la faim, ni de la parenté et les poussins répondent à un playback de façon similaire à un vrai frère. Tous ces résultats apportent la première preuve expérimentale que les juvéniles communiquent de façon honnête sur leurs besoins, ajustent activement le rythme de leurs cris et utilisent des composantes multiples de leurs vocalisations d'une façon qui réduit le coût de la compétition. De plus, il s'agit de la première démonstration que des règles de conversation régissent de longs échanges vocaux chez les animaux de façon comparable aux règles basiques observées chez l'Homme. Dans un second axe, nous avons exploré les stratégies comportementales que les poussins adoptent pour rivaliser avec plusieurs frères et soeurs, par le biais d'expériences de playback. Nous avons trouvé que les poussins mémorisent des asymétries de compétitivité entre deux individus qui dialoguent et répondent plus agressivement au moins compétitif une fois qu'ils sont confrontés à chacun isolément. Dans la même ligne, quand ils entendent un nombre variable d'individus criant à un taux variable, les poussins investissent le plus contre des rivaux moins nombreux et moins motivés. En accord avec les prédictions des modèles théoriques, les poussins de chouette effraie escaladent donc les conflits pour lesquels leur chance de gagner contrebalance le plus l'énergie dépensée. Nous révélons ainsi que 1) les jeunes frères et soeurs 'espionnent' les interactions de leurs rivaux pour évaluer leur compétitivité relative, ce qui est sans doute moins coûteux qu'une confrontation directe avec chacun, et 2) dosent leur investissement vocal en fonction du nombre de rivaux actuellement en compétition et de leur motivation de façon concomitante. Ces résultats montrent que les interactions entre frères et soeurs au nid reposent sur des mécanismes similaires à ceux observés, mais encore de façon anecdotique, chez les adultes non apparentés qui se disputent les territoires et partenaires sexuels. Cette thèse souligne donc combien il est crucial de considérer dorénavant la famille comme un réseau de communication à part entière pour mieux comprendre comment les jeunes résolvent les conflits autour du partage des ressources parentales. Plus généralement, elle révèle l'importance de la dynamique temporelle des vocalisations dans les conflits et la communication des animaux. A la lumière de nos résultats, la chouette effraie apparaît comme un modèle clé pour de futures recherches sur la résolution des conflits et la communication acoustique. - In species with parental care, offspring contest priority access to food by begging through conspicuous postures and vocalisations and by physically jockeying. Siblings differ in their competitiveness, especially in the case of age and size hierarchies, and their hunger level fluctuates in time. As in competition in general, each individual should adjust its investment to opponents that is to say to its siblings' needs and behaviours. In the particular context of family, according to kin selection theory, siblings derive extra fitness benefits from their mutual survival and hence the spreading of the genes they share. The "sibling negotiation" predicts that, under certain conditions, young would negotiate among them priority access to food, which reduces competition costs and enables promoting the most hungry siblings. To date, the literature focuses on signals of need between parents and offspring and competitive interactions (in particular among siblings) are mostly studied within pairwise interactions, yet they commonly involve more numerous rivals. This PhD aims at better understanding how and the extent to which several young siblings compete through signalling. This is important since this influences how food is allocated among them, thus the outcome of sibling rivalry and ultimately their fitness. I use the barn owl (Tyto alba) as a model, in which the one to nine nestlings emit a simple noisy call thousands of times per night. Thereby, they would negotiate among them priority access to the indivisible food next delivered prior to parents' feeding visits. A hungry nestling emits more calls than a less hungry sibling, which deters it to call in return and ultimately beg food at parents. The optimal investment thus corresponds to constantly deterring the rival to compete, given that parents' arrival is unpredictable, but at the lowest costs. In the first axis of my thesis, we explored within dyads the acoustic mechanisms by which owlets dose vocal effort when competing during the hours they are left alone. We found that owlets avoid overlapping each other's calls. This would enhance the discrimination of both call number and duration, which honestly reflect individuals' hunger level and hence motivation to compete. Such antiphony seems best adapted to the fact that siblings actually use subtle temporal variations in the rhythm and duration of their calls to take or give their turn. Owlets alternate monologs, in which lengthening calls efficiently deters the rival to respond while reducing call number. Such rules depend neither on seniority, hunger level nor kinship since nestlings responded similarly to a live sibling and an unrelated playback individual. Taken together, these findings provide the first experimental proof that dependent young honestly communicate about their need, actively adjust the timing of their calls and use multicomponent signals in a way that reduces vocal costs. Moreover, this is the first demonstration of conversational rules underlying animal long-lasting vocal exchanges comparable to the basic turn-taking signals observed in humans. In the second axis, we focused on the behavioural strategies owlets adopt to compete with more than one sibling, using playback experiments. We found that singleton bystanders memorised competitive asymmetries between two playback individuals dialoguing and responded more aggressively to the submissive one once they later faced each of both alone. Moreover, when hearing a varying number of nestlings calling at varying rates, owlets vocally invested the most towards fewer and less motivated rivals. In line with predictions from models on conflict settlement, barn owls thus escalate contests in which their chance of winning best counterbalances the energy spent. These results reveal that young socially eavesdrop on their siblings' interactions to assess their relative competitiveness at likely lower costs than direct confrontation, and dose vocal effort relative to both their number and motivation. This shows that young siblings' interactions imply mechanisms similar to those observed, yet still anecdotally, in unrelated adults that contest mates and territories. This PhD therefore highlights how crucial it is to further consider family as a communication network to better understand how siblings resolve conflicts over the share of parental resources. More generally, it provides important insights into the role of the temporal dynamics of signalling during animal contests and communication. In the light of our findings, the barn owl emerges as a key model for future research on conflict resolution and acoustic communication in animals.

Condom use with steady partners among heterosexual people living with HIV in Europe: testing the information-motivation-behavioral skills model.

Guided by a modified information-motivation-behavioral skills model, this study identified predictors of condom use among heterosexual people living with HIV with their steady partners. Consecutive patients at 14 European HIV outpatient clinics received an anonymous, standardized, self-administered questionnaire between March and December 2007. Data were analyzed using descriptive statistics and two-step backward elimination regression analyses stratified by gender. The survey included 651 participants (n = 364, 56% women; n = 287, 44%). Mean age was 39 years for women and 43 years for men. Most had acquired HIV sexually and more than half were in a serodiscordant relationship. Sixty-three percent (n = 229) of women and 59% of men (n = 169) reported at least one sexual encounter with a steady partner 6 months prior to the survey. Fifty-one percent (n = 116) of women and 59% of men (n = 99) used condoms consistently with that partner. In both genders, condom use was positively associated with subjective norm conducive to condom use, and self-efficacy to use condoms. Having a partner whose HIV status was positive or unknown reduced condom use. In men, higher education and knowledge about condom use additionally increased condom use, while the use of erectile-enhancing medication decreased it. For women, HIV disclosure to partners additionally reduced the likelihood of condom use. Positive attitudes to condom use and subjective norm increased self-efficacy in both genders, however, a number of gender-related differences appeared to influence self-efficacy. Service providers should pay attention to the identified predictors of condom use and adopt comprehensive and gender-related approaches for preventive interventions with people living with HIV.

Development and Validation of Decision Rules to Guide Frequency of Monitoring CD4 Cell Count in HIV-1 Infection before Starting Antiretroviral Therapy.

Background: Although CD4 cell count monitoring is used to decide when to start antiretroviral therapy in patients with HIV-1 infection, there are no evidence-based recommendations regarding its optimal frequency. It is common practice to monitor every 3 to 6 months, often coupled with viral load monitoring. We developed rules to guide frequency of CD4 cell count monitoring in HIV infection before starting antiretroviral therapy, which we validated retrospectively in patients from the Swiss HIV Cohort Study.Methodology/Principal Findings: We built up two prediction rules ("Snap-shot rule" for a single sample and "Track-shot rule" for multiple determinations) based on a systematic review of published longitudinal analyses of CD4 cell count trajectories. We applied the rules in 2608 untreated patients to classify their 18 061 CD4 counts as either justifiable or superfluous, according to their prior >= 5% or < 5% chance of meeting predetermined thresholds for starting treatment. The percentage of measurements that both rules falsely deemed superfluous never exceeded 5%. Superfluous CD4 determinations represented 4%, 11%, and 39% of all actual determinations for treatment thresholds of 500, 350, and 200x10(6)/L, respectively. The Track-shot rule was only marginally superior to the Snap-shot rule. Both rules lose usefulness for CD4 counts coming near to treatment threshold.Conclusions/Significance: Frequent CD4 count monitoring of patients with CD4 counts well above the threshold for initiating therapy is unlikely to identify patients who require therapy. It appears sufficient to measure CD4 cell count 1 year after a count > 650 for a threshold of 200, > 900 for 350, or > 1150 for 500x10(6)/L, respectively. When CD4 counts fall below these limits, increased monitoring frequency becomes advisable. These rules offer guidance for efficient CD4 monitoring, particularly in resource-limited settings.

Role and regulation of polyphosphate in leishmania parasites

Le protozoaire unicellulaire Leishmania est l'agent responsable de la leishmaniose, une maladie parasitaire humaine qui se manifeste par des lésions de la peau, se résolvant le plus souvent spontanément, jusqu'à des lésions viscérales fatales. Le parasite est transmis de l'insecte à l'hôte mammifère lors d'un repas sanguin de la mouche des sables et y réside respectivement sous formes extra- et intracellulaires. On estime que cette maladie touche environ 12 millions de personnes dans 98 pays. Etant donné que les médicaments disponibles à ce jour sont faiblement efficaces et/ou hautement toxiques, il est indispensable de consolider les connaissances sur le fonctionnement et la survie du parasite pour pouvoir développer de nouvelles stratégies de traitements et de préventions. Tous les organismes vivants, dont Leishmania, contiennent du polyphopshate (polyP). Cette molécule chargée négativement est constituée de trois jusqu'à plusieurs centaines de résidus de phosphates reliées par des liaisons à haute énergie. Le polyP sert donc de source d'énergie et de réservoir de phosphate; dans certaines espèces, il joue aussi un rôle dans l'adaptation au stress et la virulence de pathogènes. Ceci nous a amené à étudier le rôle du polyP dans le parasite Leishmania. L'enzyme responsable de la synthèse de polyP a été identifié récemment dans la levure : il s'agit de la chaperone de transport vacuolaire 4 (Vtc4). Nous avons identifié un homologue de Vtc4 chez les Trypanosomatidae, et avons donc décidé d'examiner sa fonction dans le métabolisme du polyP chez Leishmania. En éliminant l'expression de Vtc4 chez L. major et L. guyanensis, nous avons pu démontrer qu'il est indispensable pour la production de polyP chez Leishmania. De plus, nous avons constaté que ces parasites possèdent des chaînes de polyP allant de trois jusqu'à environ 300 résidus de phosphate. Le taux de polyP dans la cellule est précisément régulé et varie entre un très haut niveau durant la phase proliférative des promastigotes à un niveau bas en phase stationnaire tardive, alors que l'expression de Vtc4p reste stable. Dans les amastigotes intracellulaires, seulement des petites quantités de polyP et de Vtc4p sont détectées. En outre, l'absence de Vc4p et de polyP n'a pas d'effet significatif sur les infections in vivo de souris, ce qui indique que le polyP n'est pas nécessaire au développement de la leishmaniose. Ceci suggère que Vtc4p n 'est pas une bonne cible pour le développement de nouveaux traitements contre Leishmania. "Néanmoins, la présence du polyP favorise fortement la survie du parasite suite à un choc de température (37°C) et aide ainsi à sa persistance intracellulaire pendant les premiers jours d'infection de macrophages. En résumé, nos résultats indiquent que si le polyP a peu d'importance pendant l'infection et le développement de la leishmaniose chez la souris, il est par contre crucial pour l'adaptation à des situations de stress comme l'augmentation de la température. Le fait que le polyP a été conservé dans tous les organismes durant l'évolution suggère toutefois que cette molécule joue un rôle fondamental. Etant donné que l'absence de polyP n'a pas d'effet sur la survie des amastigotes, il pourrait être plus important dans la forme promastigote infectant la mouche des sables. - The unicellular protozoan parasite Leishmania is the causative agent of the human disease leishmaniasis, which can range from self-healing skin lesions to fatal visceral lesions. The parasite is transmitted from the insect vector to the mammalian host when the sand fly takes its blood meal and exists in an extra- and an intracellular form, respectively. The disease is estimated to affect 12 million people in 98 countries and currently available drug treatments are of relatively low potency and/or high toxicity. Thus, investigating parasite survival mechanisms and parasite adaptation to the two host environments contributes to the general understanding of Leishmania propagation and might therefore help to develop future treatments or preventions. All living cells, including Leishmania, contain a negatively charged polymer of a few up to several hundred phosphate residues. These so-called polyphosphates (polyPs) serve as an energy source and phosphate reservoir. In some organisms, polyP is also involved in adaptation to stresses and virulence of pathogens. Therefore we were interested in investigating the importance of polyP in Leishmania parasites. Recently, an eukaryotic enzyme responsible for polyP synthesis has been identified as the vacuolar transporter chaperone 4 (Vtc4) in yeast. We, and others, found a Vtc4 homologue in trypanosomatids and decided to examine its potential function in polyP metabolism. By generating VTC4 knock-out cell lines in L. major and Vtc4 knock-down cell lines in L. guyanensis, we were able to demonstrate that Vtc4p is responsible for the total amount of cellular polyP. We also observed that Leishmania polyP chain length ranges from a few up to around 300 residues and that its level is tightly regulated. PolyP abundance is highest during the logarithmic proliferating phase of promastigotes and decreases in the stationary phase, while Vtc4 protein expression remains stable during both phases. In the intracellular amastigote form, only low amounts of polyP and Vtc4p were detectable. Furthermore, absence of Vtc4p and polyP did not have a significant effect on in vivo mouse infections, indicating that polyP is not necessary for Leishmania disease progression. This suggests that Vtc4p would be a poor drug target against Leishmania infection. However, presence of the polymer strongly supported parasite survival during heat shock (37°C) and thereby promoted intracellular persistence during the first days of macrophage infections. Taken together, we found that polyP has little importance in Leishmania {in vivo) infection but that it plays a crucial role during adaptation to stress, such as heat shock. Given that polyP has been preciously conserved in all organisms during evolution it seems to play a fundamental role. Since absence of polyP does not affect amastigote survival, it might be significant for promastigote existence in the sand fly vector.

Vaccine potentials of an intrinsically unstructured fragment derived from the blood stage-associated Plasmodium falciparum protein PFF0165c.

We have identified new malaria vaccine candidates through the combination of bioinformatics prediction of stable protein domains in the Plasmodium falciparum genome, chemical synthesis of polypeptides, in vitro biological functional assays, and association of an antigen-specific antibody response with protection against clinical malaria. Within the predicted open reading frame of P. falciparum hypothetical protein PFF0165c, several segments with low hydrophobic amino acid content, which are likely to be intrinsically unstructured, were identified. The synthetic peptide corresponding to one such segment (P27A) was well recognized by sera and peripheral blood mononuclear cells of adults living in different regions where malaria is endemic. High antibody titers were induced in different strains of mice and in rabbits immunized with the polypeptide formulated with different adjuvants. These antibodies recognized native epitopes in P. falciparum-infected erythrocytes, formed distinct bands in Western blots, and were inhibitory in an in vitro antibody-dependent cellular inhibition parasite-growth assay. The immunological properties of P27A, together with its low polymorphism and association with clinical protection from malaria in humans, warrant its further development as a malaria vaccine candidate.

L'autonomie obligatoire : analyse sociologique des dispositifs scolaires de l'autonomie

La thèse traite des injonctions à l'autonomie dans le champ scolaire et des pratiques destinées à favoriser son développement chez les élèves. Elle se base sur une enquête ethnographique réalisée dans une école primaire genevoise, réunissant des observations menées durant deux ans et demi dans des classes allant de la 2° enfantine à la 3e primaire (2P-5P, selon HARMOS) et des entretiens d'enseignants, complétée par des observations dans les familles et des entretiens d'enfants et de leurs parents. Elle met en évidence le paradoxe auquel sont quotidiennement confrontés les enseignants qui doivent amener les élèves à découvrir et s'approprier les savoirs et les règles scolaires de manière autonome, tout en encadrant leurs pratiques afin que ceux-ci se conforment aux attentes de l'institution scolaire. La notion de dispositif, en tant qu'échelle intermédiaire d'analyse (Bonnéry, 2009), rend possible l'articulation des niveaux macro- et micro-sociologique dans l'analyse des pratiques. L'analyse des dispositifs scolaires de l'autonomie considère la traduction de la norme d'autonomie et des injonctions institutionnelles dans les pratiques individuelles. L'autonomie est ici définie comme un principe de socialisation, sur le mode de l'engagement : les dispositifs scolaires de l'autonomie visent à amener les élèves à choisir, vouloir, aimer ce que l'institution scolaire leur demande. Cette analyse permet de dégager plusieurs types de dispositifs et surtout de mettre en lumière leurs contradictions internes lorsque ne sont pas perçues ou partagées par les acteurs les attentes implicites ou explicites contenues dans les dispositifs. L'analyse des dispositifs porte également, dans une perspective plus interactionniste, sur les stratégies individuelles de gestion des contradictions et la retraduction des normes par les acteurs. Les dispositifs sont alors examinés sous l'angle des processus d'étiquetage réalisé par les enseignants et des formes de déviances qu'ils font apparaître chez les élèves et les parents. - The thesis deals with injunctions to autonomy in the field of education and practices used to facilitate its development in students. It is based on an ethnographic survey in Geneva elementary school, bringing together observations made during two and a half years in classes ranging from 2P to 5P (according HARMOS), interviews with teachers, observations in families and interviews with children and their parents. It highlights the paradox that teachers are daily confronted to, as they should encourage students to discover and acquire the knowledge and school rules independently, while framing their practices so that they conform to the expectations of the educational institution. The concept of dispositif as an intermediary level of analysis (Bonnéry, 2009) makes possible the articulation of the macro- and micro-sociological analysis in practices. The analysis of pedagogic dispositives considers the translation of the norm of autonomy and institutional injunctions in individual practices. In this perspective, autonomy is defined as principle of socialization, on the mode of engagement : pedagogic autonomy dispositives designed to encourage students to choose, want, love what institution demands. This analysis identifies several types of dispositives and highlights their internal contradictions when actors do not share expectations. In a more interactionnist perspective, the analysis also includes individual strategies to deal with contradictions and the retranslation of norms by actors. The dispositives are then examined in term of the labelling process conducted by teachers and forms of deviance among students and parents.

Local selection rules that can determine specific pathways of DNA unknotting by type II DNA topoisomerases.

We performed numerical simulations of DNA chains to understand how local geometry of juxtaposed segments in knotted DNA molecules can guide type II DNA topoisomerases to perform very efficient relaxation of DNA knots. We investigated how the various parameters defining the geometry of inter-segmental juxtapositions at sites of inter-segmental passage reactions mediated by type II DNA topoisomerases can affect the topological consequences of these reactions. We confirmed the hypothesis that by recognizing specific geometry of juxtaposed DNA segments in knotted DNA molecules, type II DNA topoisomerases can maintain the steady-state knotting level below the topological equilibrium. In addition, we revealed that a preference for a particular geometry of juxtaposed segments as sites of strand-passage reaction enables type II DNA topoisomerases to select the most efficient pathway of relaxation of complex DNA knots. The analysis of the best selection criteria for efficient relaxation of complex knots revealed that local structures in random configurations of a given knot type statistically behave as analogous local structures in ideal geometric configurations of the corresponding knot type.

Posttranscriptional repression of GacS/GacA-controlled genes by the RNA-binding protein RsmE acting together with RsmA in the biocontrol strain Pseudomonas fluorescens CHA0.

In the plant-beneficial soil bacterium Pseudomonas fluorescens CHA0, the production of biocontrol factors (antifungal secondary metabolites and exoenzymes) is controlled at a posttranscriptional level by the GacS/GacA signal transduction pathway involving RNA-binding protein RsmA as a key regulatory element. This protein is assumed to bind to the ribosome-binding site of target mRNAs and to block their translation. RsmA-mediated repression is relieved at the end of exponential growth by two GacS/GacA-controlled regulatory RNAs RsmY and RsmZ, which bind and sequester the RsmA protein. A gene (rsmE) encoding a 64-amino-acid RsmA homolog was identified and characterized in strain CHA0. Overexpression of rsmE strongly reduced the expression of target genes (hcnA, for a hydrogen cyanide synthase subunit; aprA, for the main exoprotease; and phlA, for a component of 2,4-diacetylphloroglucinol biosynthesis). Single null mutations in either rsmA or rsmE resulted in a slight increase in the expression of hcnA, aprA, and phlA. By contrast, an rsmA rsmE double mutation led to strongly increased and advanced expression of these target genes and completely suppressed a gacS mutation. Both the RsmE and RsmA levels increased with increasing cell population densities in strain CHA0; however, the amount of RsmA showed less variability during growth. Expression of rsmE was controlled positively by GacA and negatively by RsmA and RsmE. Mobility shift assays demonstrated specific binding of RsmE to RsmY and RsmZ RNAs. The transcription and stability of both regulatory RNAs were strongly reduced in the rsmA rsmE double mutant. In conclusion, RsmA and RsmE together account for maximal repression in the GacS/GacA cascade of strain CHA0.

Social Cognition is not Reducible to Theory of Mind. When Children use Deontic Rules to Predict Others' Behaviors

The objective of this paper is to discuss whether children have a capacity for deonticreasoning that is irreducible to mentalizing. The results of two experiments point tothe existence of such non-mentalistic understanding and prediction of the behaviourof others. In Study 1, young children (3- and 4-year-olds) were told different versionsof classic false-belief tasks, some of which were modified by the introduction of a ruleor a regularity. When the task (a standard change of location task) included a rule, theperformance of 3-year-olds, who fail traditional false-belief tasks, significantly improved.In Study 2, 3-year-olds proved to be able to infer a rule from a social situation and touse it in order to predict the behaviour of a character involved in a modified versionof the false-belief task. These studies suggest that rules play a central role in the socialcognition of young children and that deontic reasoning might not necessarily involvemind reading.

Transnational authority in the knowledge-based economy: Who sets the standards of ICT training and certification?

This article examines the extent and limits of nonstate forms of authority in international relations. It analyzes how the information and communication technology (ICT) infrastructure for the tradability of services in a global knowledge-based economy relies on informal regulatory practices for the adjustment of ICT-related skills. By focusing on the challenge that highly volatile and short-lived cycles of demands for this type of knowledge pose for ensuring the right qualification of the labor force, the article explores how companies and associations provide training and certification programs as part of a growing market for educational services setting their own standards. The existing literature on non-conventional forms of authority in the global political economy has emphasized that the consent of actors, subject to informal rules and some form of state support, remains crucial for the effectiveness of those new forms of power. However, analyses based on a limited sample of actors tend toward a narrow understanding of the issues concerned and fail to fully explore the differentiated space in which non state authority is emerging. This article develops a three-dimensional analytical framework that brings together the scope of the issues involved, the range of nonstate actors concerned, and the spatial scope of their authority. The empirical findings highlight the limits of these new forms of nonstate authority and shed light on the role of the state and international governmental organizations in this new context.