Molecular typing reveals substantial Plasmodium vivax infection in asymptomatic adults in a rural area of Cameroon

BACKGROUND: Malaria in Cameroon is due to infections by Plasmodium falciparum and, to a lesser extent, Plasmodium malariae and Plasmodium ovale, but rarely Plasmodium vivax. A recent report suggested “Plasmodium vivax–like” infections around the study area that remained unconfirmed. Therefore, molecular and antigenic typing was used to investigate the prevalence of P. vivax and Duffy in asymptomatic adults resident in Bolifamba. METHODS: A cross-sectional study was conducted from July 2008 to October 2009. The status of all parasite species was determined by nested PCR in 269 blood samples collected. The P. falciparum and P. vivax anti-MSP/CSP antibody status of each subject was also determined qualitatively by a rapid card assay. Parasite DNA was extracted from a sample infected with three parasite species, purified and sequenced. The Duffy antigen status of 12 subjects infected with P. vivax was also determined by sequencing. In silico web-based tools were used to analyse sequence data for similarities and matches to reference sequences in public DNA databases. RESULTS: The overall malaria parasite prevalence in 269 individuals was 32.3% (87) as determined by PCR. Remarkably, 14.9% (13/87) of infections were caused either exclusively or concomitantly by P. vivax, established both by PCR and microscopic examination of blood smears, in individuals both positive (50%, 6/12) and negative (50%, 6/12) for the Duffy receptor. A triple infection by P. falciparum, P. vivax and P. malariae, was detected in one infected individual. Anti-MSP/CSP antibodies were detected in 72.1% (194/269) of samples, indicating high and continuous exposure to infection through mosquito bites. DISCUSSION: These data provide the first molecular evidence of P. vivax in Duffy positive and negative Cameroonians and suggest that there may be a significant prevalence of P. vivax infection than expected in the study area. Whether the P. vivax cases were imported or due to expansion of a founder effect was not investigated. Notwithstanding, the presence of P. vivax may complicate control efforts if these parasites become hypnozoitic or latent as the liver stage. CONCLUSIONS: These data strongly suggest that P. vivax is endemic to the south-west region of Cameroon and should be taken into account when designing malaria control strategies

Remodeling of the malaria parasite and host human red cell by vesicle amplification that induces artemisinin resistance

Artemisinin resistance threatens worldwide malaria control and elimination. Elevation of phosphatidylinositol-3-phosphate (PI3P) can induce resistance in blood stages of Plasmodium falciparum The parasite unfolded protein response (UPR) has also been implicated as a proteostatic mechanism that may diminish artemisinin-induced toxic proteopathy. How PI3P acts and its connection to the UPR remain unknown, although both are conferred by mutation in P falciparum Kelch13 (K13), the marker of artemisinin resistance. Here we used cryoimmunoelectron microscopy to show that K13 concentrates at PI3P tubules/vesicles of the parasite's endoplasmic reticulum (ER) in infected red cells. K13 colocalizes and copurifies with the major virulence adhesin PfEMP1. The PfEMP1-K13 proteome is comprehensively enriched in multiple proteostasis systems of protein export, quality control, and folding in the ER and cytoplasm and UPR. Synthetic elevation of PI3P that induces resistance in absence of K13 mutation also yields signatures of proteostasis and clinical resistance. These findings imply a key role for PI3P-vesicle amplification as a mechanism of resistance of infected red cells. As validation, the major resistance mutation K13C580Y quantitatively increased PI3P tubules/vesicles, exporting them throughout the parasite and the red cell. Chemical inhibitors and fluorescence microscopy showed that alterations in PfEMP1 export to the red cell and cytoadherence of infected cells to a host endothelial receptor are features of multiple K13 mutants. Together these data suggest that amplified PI3P vesicles disseminate widespread proteostatic capacity that may neutralize artemisinins toxic proteopathy and implicate a role for the host red cell in artemisinin resistance. The mechanistic insights generated will have an impact on malaria drug development

A micro-bead device to explore Plasmodium falciparum-infected, spherocytic or aged red blood cells prone to mechanical retention by spleen endothelial slits

Présentation oraleInternational audiencen.

Deletion of a Malaria Invasion Gene Reduces Death and Anemia, in Model Hosts

Malaria parasites induce complex cellular and clinical phenotypes, including anemia, cerebral malaria and death in a wide range of mammalian hosts. Host genes and parasite ‘toxins’ have been implicated in malarial disease, but the contribution of parasite genes remains to be fully defined. Here we assess disease in BALB/c mice and Wistar rats infected by the rodent malaria parasite Plasmodium berghei with a gene knock out for merozoite surface protein (MSP) 7. MSP7 is not essential for infection but in P. falciparum, it enhances erythrocyte invasion by 20%. In vivo, as compared to wild type, the P. berghei Δmsp7 mutant is associated with an abrogation of death and a decrease from 3% to 2% in peak, circulating parasitemia. The Δmsp7 mutant is also associated with less anemia and modest increase in the size of follicles in the spleen. Together these data show that deletion of a single parasite invasion ligand modulates blood stage disease, as measured by death and anemia. This work is the first to assess the contribution of a gene present in all plasmodial species in severe disease

Analyse des facteurs épidémiologiques immunologiques et génétiques de prédisposition au paludisme grave dans une population d'enfants vivant à Bamako

En zone d'endémie palustre, de nombreuses études ont montré l'importance des facteurs épidémiologiques, immunologiques et génétiques dans le contrôle de l'infection à Plasmodium falciparum. Ces facteurs ont des effets quelquefois contradictoires ou varient en fonction du faciès épidémiologique de la zone. Les objectifs de notre étude, réalisée à Bamako, étaient : 1)- De rechercher des éléments en faveur d'un déterminisme génétique du paludisme grave. Ceci implique la mise en évidence d'un phénomène d'agrégation familiale des cas de paludisme grave dans cette population. 2)- D'identifier certains facteurs épidémiologiques de risque de développement d'un paludisme grave chez l'enfant. 3)- D'analyser certaines principales cytokines de la réponse immune (IFN-g, IL-4, IL-5, IL-10, IL-12 p70et IL-13) présentes dans le sang périphérique de patients atteints de neuropaludisme ou d'anémie palustre grave. 4)- De tester l'association entre des polymorphismes situés sur le gène IL12B (codant pour l'IL-12 p40) et le paludisme grave. Cette étude a mis en évidence l'existence d'une prédisposition individuelle et familiale du neuropaludisme et de l'anémie palustre grave dans cette population de Bamako. Par ailleurs, plusieurs facteurs de risque de paludisme grave chez l'enfant ont été identifiés dans cette population de Bamako. Ces facteurs sont principalement liés à l'enfant ou à leur mère. Ainsi, à l'exception de l'histoire de la vaccination contre la fièvre jaune chez l'enfant associée à une augmentation du risque de développement d'un paludisme grave chez l'enfant, l'étude souligne l'importance de facteurs maternels, tels que la durée d'allaitement, le niveau d'éducation, la connaissance du mode de transmission du paludisme et l'existence d'une maladie chronique qui affectent significativement le risque de développement d'un paludisme grave chez l'enfant. Ces études soulignent l'importance des programmes visant à améliorer à la fois la santé et l'éducation maternelles dans le contrôle du paludisme. L'analyse de certaines cytokines dans le sang périphérique de patients a mis en évidence le rôle protecteur de l'IFN-g contre le paludisme grave ou le décès dû au neuropaludisme. L'étude génétique met en évidence le rôle de l'IL-12 dans le déterminisme du neuropaludisme. Un polymorphisme (insertion-délétion de 4 bases) situé dans la région promotrice de l'IL12B associé à une variation du niveau d'expression du gène IL12B ou de la production d'IL12p40 ou d'IL12p70 ou du monoxyde d'azote est associé au neuropaludisme. Cette étude contribue à une meilleure compréhension de l'épidémiologie du paludisme grave et des mécanismes de résistance liés à cette infection. L'identification des facteurs épidémiologiques de risque de développement du paludisme grave chez l'enfant permettra de renforcer les stratégies de lutte contre cette infection ; celle des cytokines impliquées dans la protection contre cette maladie sera d'une aide précieuse pour l'élaboration de nouvelles stratégies thérapeutiques ou vaccinales.Several studies in endemic regions have shown the importance of epidemiological, immunological and genetic factors in the control of Plasmodium falciparum infection. The effects of these factors are sometime contradictory, or vary with epidemiological facies or the area. This study conducted in Bamako (a malaria endemic area) aims to : 1)- test whether cerebral malaria or severe malarial anaemia aggregated within families (as this is the first step towards a family-based approach to identify the environmental and genetic pathways). 2)- identify epidemiological risk factors fore severe malaria among children living in Bamako. 3)- quantify the level of some principal cytokines of immune response (IFN-g, IL-4, IL-5, IL-12 p70 et IL-13) in the peripheral blood of patient with cerebral malaria or severe malarial anaemia. 4)- test the association between IL12B gene (coding for IL-12 p40) polymorphisms in and severe malaria. Our data suggest strong individual and familial aggregation of cerebral malaria and severe malarial anaemia in population of Bamako. In addition, several epidemiological risk factors for severe malaria have been identified in this population. With the exception of a personal yellow fever vaccination histoty which is associated with an increase risk of severe malaria, al lthe studied independent factors associated with severe malaria were directly related to child's mother : her personal health status or her knowledge, attitude and practices. Programmes aiming to improve maternal health and education may thus reduce the incidence of severe malaria in Mali as well as in neighbouring countries, and should therefore be advocated. Quantification of some cytokines in the peripheral blood highlighted the protector role of IFN-g for severe malaria and death due to cerebral malaria. Genetic study underlines the role of IL-12 in the determinism of cerebral malaria. There is an association between cerebral malaria and an insertion-deletion of 4 bases in the IL12B promoter region ; this polymorphism has been associated with the reduce levels of IL12 p40, IL12 p70 and NO production. Together, our data provide further insight into the epidemiology of severe malaria and host mechanism of resistance to this infection. The identification of epidemiological risk factors for severe malaria will allow reinforcement of the strategies of control of this infection , definition of cytokines implicated in the protection against this disease will be an incaluable help in the elaboration of new therapeutic and vaccinal strategies.BORDEAUX2-BU Santé (330632101) / SudocSudocFranceF

Reduced erythrocyte deformability associated with hypoargininemia during Plasmodium falciparum malaria.

International audienceThe mechanisms underlying reduced red blood cell (RBC) deformability during Plasmodium falciparum (Pf) malaria remain poorly understood. Here, we explore the possible involvement of the L-arginine and nitric oxide (NO) pathway on RBC deformability in Pf-infected patients and parasite cultures. RBC deformability was reduced during the acute attack (day0) and returned to normal values upon convalescence (day28). Day0 values correlated with plasma L-arginine levels (r = 0.69; p = 0.01) and weakly with parasitemia (r = -0.38; p = 0.006). In vitro, day0 patient's plasma incubated with ring-stage cultures at 41°C reduced RBC deformability, and this effect correlated strongly with plasma L-arginine levels (r = 0.89; p < 0.0001). Moreover, addition of exogenous L-arginine to the cultures increased deformability of both Pf-free and trophozoite-harboring RBCs. NO synthase activity, evidenced in Pf-infected RBCs, induced L-arginine-dependent NO production. These data show that hypoargininemia during P. falciparum malaria may altogether impair NO production and reduce RBC deformability, particularly at febrile temperature

Association of a promoter polymorphism in the gene encoding interleukin-12 P40 (IL12B) with cerebral malaria in a population living in Bamako

International audienceno abstrac

RESEARCH Open Access Molecular typing reveals substantial Plasmodium

vivax infection in asymptomatic adults in a rura

Genomic Expression Analyses Reveal Lysosomal, Innate Immunity Proteins, as Disease Correlates in Murine Models of a Lysosomal Storage Disorder

<div><p>Niemann-Pick Type C (NPC) disease is a rare, genetic, lysosomal disorder with progressive neurodegeneration. Poor understanding of the pathophysiology and a lack of blood-based diagnostic markers are major hurdles in the treatment and management of NPC and several additional, neurological lysosomal disorders. To identify disease severity correlates, we undertook whole genome expression profiling of sentinel organs, brain, liver, and spleen of <em>Balb/c Npc1^−/−</em> mice relative to <em>Npc1^+/−</em> at an asymptomatic stage, as well as early- and late-symptomatic stages. Unexpectedly, we found prominent up regulation of innate immunity genes with age-dependent change in their expression, in all three organs. We shortlisted a set of 12 secretory genes whose expression steadily increased with age in both brain and liver, as potential plasma correlates of neurological and/or liver disease. Ten were innate immune genes with eight ascribed to lysosomes. Several are known to be elevated in diseased organs of murine models of other lysosomal diseases including Gaucher’s disease, Sandhoff disease and MPSIIIB. We validated the top candidate lysozyme, in the plasma of <em>Npc1^−/−</em> as well as <em>Balb/c Npc1^nmf164</em> mice (bearing a point mutation closer to human disease mutants) and show its reduction in response to an emerging therapeutic. We further established elevation of innate immunity in <em>Npc1^−/−</em> mice through multiple functional assays including inhibition of bacterial infection as well as cellular analysis and immunohistochemistry. These data revealed neutrophil elevation in the <em>Npc1</em>^−/− spleen and liver (where large foci were detected proximal to damaged tissue). Together our results yield a set of lysosomal, secretory innate immunity genes that have potential to be developed as pan or specific plasma markers for neurological diseases associated with lysosomal storage and where diagnosis is a major problem. Further, the accumulation of neutrophils in diseased organs (hitherto not associated with NPC) suggests their role in pathophysiology and disease exacerbation.</p> </div