Seasonal malaria chemoprevention combined with community case management of malaria in children under 10 years of age, over 5 months, in south-east Senegal: A cluster-randomised trial.

BACKGROUND: Seasonal malaria chemoprevention (SMC) is recommended in the Sahel region of Africa for children under 5 years of age, for up to 4 months of the year. It may be appropriate to include older children, and to provide protection for more than 4 months. We evaluated the effectiveness of SMC using sulfadoxine-pyrimethamine plus amodiaquine given over 5 months to children under 10 years of age in Saraya district in south-east Senegal in 2011. METHODS AND FINDINGS: Twenty-four villages, including 2,301 children aged 3-59 months and 2,245 aged 5-9 years, were randomised to receive SMC with community case management (CCM) (SMC villages) or CCM alone (control villages). In all villages, community health workers (CHWs) were trained to treat malaria cases with artemisinin combination therapy after testing with a rapid diagnostic test (RDT). In SMC villages, CHWs administered SMC to children aged 3 months to 9 years once a month for 5 months. The study was conducted from 27 July to 31 December 2011. The primary outcome was malaria (fever or history of fever with a positive RDT). The prevalence of anaemia and parasitaemia was measured in a survey at the end of the transmission season. Molecular markers associated with resistance to SMC drugs were analysed in samples from incident malaria cases and from children with parasitaemia in the survey. SMC was well tolerated with no serious adverse reactions. There were 1,472 RDT-confirmed malaria cases in the control villages and 270 in the SMC villages. Among children under 5 years of age, the rate difference was 110.8/1,000/month (95% CI 64.7, 156.8; p < 0.001) and among children 5-9 years of age, 101.3/1,000/month (95% CI 66.7, 136.0; p < 0.001). The mean haemoglobin concentration at the end of the transmission season was higher in SMC than control villages, by 6.5 g/l (95% CI 2.0, 11; p = 0.007) among children under 5 years of age, and by 5.2 g/l (95% CI 0.4, 9.9; p = 0.035) among children 5-9 years of age. The prevalence of parasitaemia was 18% in children under 5 years of age and 25% in children 5-9 years of age in the control villages, and 5.7% and 5.8%, respectively, in these 2 age groups in the SMC villages, with prevalence differences of 12.5% (95% CI 6.8%, 18.2%; p < 0.001) in children under 5 years of age and 19.3% (95% CI 8.3%, 30.2%; p < 0.001) in children 5-9 years of age. The pfdhps-540E mutation associated with clinical resistance to sulfadoxine-pyrimethamine was found in 0.8% of samples from malaria cases but not in the final survey. Twelve children died in the control group and 14 in the SMC group, a rate difference of 0.096/1,000 child-months (95% CI 0.99, 1.18; p = 0.895). Limitations of this study include that we were not able to obtain blood smears for microscopy for all suspected malaria cases, such that we had to rely on RDTs for confirmation, which may have included false positives. CONCLUSIONS: In this study SMC for children under 10 years of age given over 5 months was feasible, well tolerated, and effective in preventing malaria episodes, and reduced the prevalence of parasitaemia and anaemia. SMC with CCM achieved high coverage and ensured children with malaria were promptly treated with artemether-lumefantrine. TRIAL REGISTRATION: www.clinicaltrials.gov NCT01449045

Potasium nutrition in rice under salt stress: role of arbuscular mycorrhizal symbiosis?

International audienceArbuscular mycorrhizal fungi (AMF) establish a symbiotic association with the roots of 80% of terrestrial plants and form complex tree-shaped feeding structures called arbuscules in colonized root cells. This association with AMF not only provides more efficient uptake of nutrients for the plant, but also confers protection against pathogens and increased tolerance to environmental stress such as salt stress [1]. Rice (Oryza sativa), the most salt-sensitive crop species amongst cereals, has a productivity strongly reduced around the world due to soil salinity/salinization and increased sea level (in deltas). High Na+ concentrations (salt stress conditions) impairs K+ uptake and inhibits many K+-activated enzymes. Rice exhibits molecular mechanisms to alleviate salt stress such as maintaining a high cellular K+/Na+ ratio, e.g. by a more efficient K+ uptake, which was recently shown to occur upon root/AMF interaction [2]. Knowledge on the role of root/AMF interaction on K+/Na+ transport upon salt stress is sparse [2, 3]. The aim of the research is to understand the mechanisms by which AMF improve plant K+ nutrition upon salt stress, taking Rhizophagus irregularis (model AMF)-rice interaction as a model. We will investigate the mechanisms by which AMF mediate K+ uptake and translocation towards root cells. Rice loss-of-function mutants for each of the three major K+ uptake systems of the plant, OsAKT1, OsHAK5 and OsHAK1, were inoculated with R. irregularis and submitted to salt stress, and their K+ contents and K+/Na+ ratios were monitored to identify key player(s) for AMF-mediated improved rice K+ nutrition and salt tolerance

Search for potassium transport systems involved in arbuscular mycorrhiza-rice symbiotic interactions

International audienceArbuscular mycorrhizal fungi (AMF) develop interdependent connections with roots of about90% of plant species. These interactions increase availability as well as translocation ofnutrients (especially N and P), and thereby improve plant nutrition and growth. Moreover,resistance to a variety of stresses, among which salt stress, has been shown to be improved byAMF-plant interactions, for example in rice. Intense research to explain the molecularmechanisms of AMF-plant beneficial interactions led to the identification of phosphate andammonium transporters involved in nutrient exchanges from AMF to the plant, in several plantspecies. In spite of the importance of potassium (K+) for plant physiology, the contribution ofAMF symbiosis to plant K+ nutrition has been little documented. Over-expression of plant K+transporters has been described in Lotus japonicus and tomato in condition of AMF symbiosis.Furthermore, K+ transport systems in the AMF Rhizophagus irregularis have been identified insilico. Here, K+ nutrition in rice colonized by R. irregularis has been analyzed at molecular andphysiological levels. Surprisingly, major K+ transport systems in rice were down-regulated uponAMF interactions, suggesting strong increase in K+ availability for uptake by root cells insymbiotic conditions. Role of K+ in the relationships between rice and R. irregularis will also bediscusse

Recherche de systèmes de transport de potassium impliqués dans le transfert de K+ de la mycorhize arbusculaire au riz lors d'interactions symbiotiques

National audienceLes champignons mycorhiziens à arbuscules (CMA) développent des connexions interdépendantes avec les racines d'environ 90% des espèces végétales. Ces interactions augmentent la disponibilité ainsi que la translocation des nutriments (en particulier N et P), et améliorent ainsi la nutrition et la croissance des plantes. De plus, la résistance à une variété de stress, parmi lesquels le stress salin, s'est avérée améliorée par les interactions CMA-plante, par exemple chez le riz. Des recherches intenses pour expliquer les mécanismes moléculaires des interactions bénéfiques CMA-plante ont conduit à l'identification de transporteurs de phosphate et d'ammonium impliqués dans les échanges de nutriments du CMA vers la plante, chez plusieurs espèces végétales. Malgré l'importance du potassium (K+) pour la physiologie des plantes, la contribution de la symbiose mycorhizienne à arbuscule à la nutrition en K+ des plantes a été peu documentée. La surexpression des transporteurs de K+ végétaux a été décrite chez Lotus japonicus et la tomate en condition de symbiose mycorhizienne à arbuscule. Ici, la nutrition en K+ du riz colonisé par Rhizophagus irregulis a été analysée aux niveaux moléculaire et physiologique. Étonnamment, les principaux systèmes de transport de K+ dans le riz étaient régulés à la baisse lors des interactions AMF, suggérant une forte augmentation de la disponibilité de K+ pour l'absorption par les cellules racinaires dans des conditions symbiotiques. De plus, des systèmes de transport de K+ dans le CMA R. irregularis ont été identifiés in silico. La fonction de l’un d’entre eux a été analysée. Le rôle de K+ dans les relations entre le riz et R. irregularis sera également discuté

Arbuscular mycorrhizal fungus Rhizophagus irregularis expresses an outwardly Shaker-like channel involved in potassium nutrition of rice ( Oryza sativa L.)

Abstract Potassium (K + ) plays crucial roles in many physiological, molecular and cellular processes in plants. Direct uptake of this nutrient by root cells has been extensively investigated, however, indirect uptake of K + mediated by the interactions of the roots with fungi in the frame of a mutualistic symbiosis, also called mycorrhizal nutrient uptake pathway, is much less known. We identified an ion channel in the arbuscular mycorrhizal (AM) fungus Rhizophagus irregularis . This channel exhibits the canonical features of Shaker-like channel shared in other living kingdoms and is named RiSKC3. Transcriptionally expressed in hyphae and in arbuscules of colonized rice roots, RiSKC3 has been shown to be located in the plasma membrane. Voltage-clamp functional characterization in Xenopus oocytes revealed that RiSKC3 is endowed with outwardly-rectifying voltage-gated activity with a high selectivity for K + over sodium ions. RiSKC3 may have a role in the AM K + pathway for rice nutrition in normal and salt stress conditions. The current working model proposes that K + ions taken up by peripheral hyphae of R. irregularis are secreted towards the host root into periarbuscular space by RiSKC3. Significance Statement Mutualistic symbiosis with arbuscular mycorrhizal (AM) fungi are beneficial for about 80% of land plants thanks to an exchange of nutrients. The AM pathway responsible for potassium (K + ) nutrition of the plant is not known. Here we uncovered a key step of this phenomenon, by functionally characterizing the first transport system in the AM fungus Rhizophagus irregularis , and we univocally demonstrated that RiSKC3 is an K + outwardly-rectifying voltage-gated Shaker-like channel

Bland-Altman plot of the whole data.

<p>The x-axis represents the average of CD4 count between the PIMA and the BD FACSCount^TM, and the y-axis represents the bias (difference) between the PIMA^TM Alere and the BD FACSCount^TM. The solid blue line represents the mean of the difference between the two measurements, and the light black lines represent the upper and lower limits of agreement (ULA: mean differences plus and 1,96 x standard deviation of the mean difference; LLA: mean differences minus and 1,96 x standard deviation of the mean difference). Legend for CD4 categories: 1: CD4 T-cells < 200/mm³; 2: CD4 T-cells between 200 and 350/mm³; 3: CD4 T-cells between 351 and 500/mm³; 4: CD4 T-cells above 500/mm³.</p

Bland-Altman analysis.

<p>Bland-Altman plots of <b>(A)</b> CD4 T-cells < 200/mm³, <b>(B)</b> between 200 and 350/mm³, <b>(C)</b> between 350 and 500/mm³, and <b>(D)</b> above 500/mm³ according the CD4 cell count levels. For each plot, the x-axis represents the average of CD4 count between the PIMA and the BD FACSCount^TM, and the y-axis represents the bias (difference) between the PIMA^TM Alere and the BD FACSCount^TM. The solid red line represents the mean of the difference between the two measurements, and the light black lines represent the upper and lower limits of agreement (ULA: mean differences plus and 1,96 x standard deviation of the mean difference; LLA: mean differences minus and 1,96 x standard deviation of the mean difference)</p

Passing-Bablok regression between PIMA^TM Alere CD4 and BD FACSCount^TM.

<p>The x-axis represents CD4 counts provided by the BD FACSCount^TM reference and the y-axis represents the CD4 counts provided by the PIMA^TM CD4. The solid line represents the regression line, and the dashed line represents the line y = x. The linear equation of the regression is y = 0.9347 x + 11.</p