Innocent Safeukui - Academia.edu (original) (raw)

Papers by Innocent Safeukui

Journal of Blood Disorders and Transfusion, Nov 29, 2013

Scientific Reports, Jan 20, 2014

The mechanisms underlying reduced red blood cell (RBC) deformability during Plasmodium falciparum... more The 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 5 0.69; p 5 0.01) and weakly with parasitemia (r 5 20.38; p 5 0.006). In vitro, day0 patient's plasma incubated with ring-stage cultures at 416C reduced RBC deformability, and this effect correlated strongly with plasma L-arginine levels (r 5 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.

doi:10.1182/blood-2008-03-146779Prepublished online June 25, 2008;2008 112: 2520-2528€€€€Odile Me... more doi:10.1182/blood-2008-03-146779Prepublished online June 25, 2008;2008 112: 2520-2528€€€€Odile Mercereau-Puijalon, Genevieve Milon, Peter H. David and Pierre A. BuffetKerneis, Huot Khun, Ines Vigan-Womas, Catherine Ottone, Thierry Jo Molina, Jean-Marc Treluyer,Sebastien Mule, Mickael Lesurtel, Nicolas Goasguen, Alain Sauvanet, Anne Couvelard, Sophie Innocent Safeukui, Jean-Michel Correas, Valentine Brousse, Deborah Hirt, Guillaume Deplaine,€

Blood, Jan 10, 2014

Patients with severe malaria treated with artesunate sometimes experience a delayed hemolytic epi... more Patients with severe malaria treated with artesunate sometimes experience a delayed hemolytic episode. Artesunate (AS) induces pitting, a splenic process whereby dead parasites are expelled from their host erythrocytes. These once-infected erythrocytes then return to the circulation. We analyzed hematologic parameters in 123 travelers treated with AS for severe malaria. Among 60 nontransfused patients observed for more than 8 days, 13 (22%) had delayed hemolysis. The peak concentration of circulating once-infected erythrocytes was measured during the first week in 21 patients and was significantly higher in 9 patients with delayed hemolysis than in 12 with other patterns of anemia (0.30 vs 0.07; P = .0001). The threshold of 180 million once-infected erythrocytes per liter discriminated patients with delayed hemolysis with 89% sensitivity and 83% specificity. Once-infected erythrocyte morphology analyzed by using ImageStream in 4 patients showed an 8.9% reduction in their projected a...

Encyclopedia of Malaria, 2015

PLoS ONE, 2011

Malaria parasites induce complex cellular and clinical phenotypes, including anemia, cerebral mal... more 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 Dmsp7 mutant is associated with an abrogation of death and a decrease from 3% to 2% in peak, circulating parasitemia. The Dmsp7 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.

Current Opinion in Hematology, 2009

Purpose of review Splenomegaly is frequent in acute or chronic forms of Plasmodium falciparum mal... more Purpose of review Splenomegaly is frequent in acute or chronic forms of Plasmodium falciparum malaria, and splenectomy is associated with more frequent fever and parasitaemia. A novel role for the spleen in malaria is indicated by recent epidemiological and experimental data, bringing about a novel paradigm on severe malaria pathogenesis. Recent findings In Sudanese children, severe malarial anaemia was associated with larger spleen, longer fever duration, and lower parasitaemia than cerebral malaria. These findings are consistent with evolution toward severe malarial anaemia being linked to the presence of a spleen-dependent mechanism that is absent or inefficient in cerebral malaria. An isolated-perfused human spleen model revealed unexpected retention of numerous erythrocytes harbouring young parasite stages (rings), probably through an innate mechanical process. Summary A new paradigm is discussed, whereby the extent of erythrocyte retention in the spleen conditions not only haemoglobin concentration and spleen size but also the rate of parasite load increase. The prediction is that, in nonimmune children, stringent splenic retention of rings and uninfected erythrocytes reduces the risk of cerebral malaria (a complication associated with high parasite loads) but increases the risk of severe malarial anaemia. This hypothesis casts new light on epidemiological, genetic, and experimental studies in malaria pathogenesis.

Blood, 2008

The current paradigm in Plasmodium falciparum malaria pathogenesis states that young, ring-infect... more The current paradigm in Plasmodium falciparum malaria pathogenesis states that young, ring-infected erythrocytes (rings) circulate in peripheral blood and that mature stages are sequestered in the vasculature, avoiding clearance by the spleen. Through ex vivo perfusion of human spleens, we examined the interaction of this unique blood-filtering organ with P falciparum–infected erythrocytes. As predicted, mature stages were retained. However, more than 50% of rings were also retained and accumulated upstream from endothelial sinus wall slits of the open, slow red pulp microcirculation. Ten percent of rings were retained at each spleen passage, a rate matching the proportion of blood flowing through the slow circulatory compartment established in parallel using spleen contrast-enhanced ultrasonography in healthy volunteers. Rings displayed a mildly but significantly reduced elongation index, consistent with a retention process, due to their altered mechanical properties. This raises t...

Blood, 2011

Infection of erythrocytes with the human malaria parasite, Plasmodium falciparum, results in dram... more Infection of erythrocytes with the human malaria parasite, Plasmodium falciparum, results in dramatic changes to the host cell structure and morphology. The predicted functional localization of the STEVOR proteins at the erythrocyte surface suggests that they may be involved in parasite-induced modifications of the erythrocyte membrane during parasite development. To address the biologic function of STEVOR proteins, we subjected a panel of stevor transgenic parasites and wild-type clonal lines exhibiting different expression levels for stevor genes to functional assays exploring parasite-induced modifications of the erythrocyte membrane. Using this approach, we show that stevor expression impacts deformability of the erythrocyte membrane. This process may facilitate parasite sequestration in deep tissue vasculature.

Blood, 2010

Clinical manifestations of Plasmodium falciparum infection are induced by the asexual stages of t... more Clinical manifestations of Plasmodium falciparum infection are induced by the asexual stages of the parasite that develop inside red blood cells (RBCs). Because splenic microcirculatory beds filter out altered RBCs, the spleen can innately clear subpopulations of infected or uninfected RBC modified during falciparum malaria. The spleen appears more protective against severe manifestations of malaria in naïve than in immune subjects. The spleen-specific pitting function accounts for a large fraction of parasite clearance in artemisinin-treated patients. RBC loss contributes to malarial anemia, a clinical form associated with subacute progression, frequent splenomegaly, and relatively low parasitemia. Stringent splenic clearance of ring-infected RBCs and uninfected, but parasite-altered, RBCs, may altogether exacerbate anemia and reduce the risks of severe complications associated with high parasite loads, such as cerebral malaria. The age of the patient directly influences the risk o...

Blood, 2012

Splenic sequestration of RBCs with reduced surface area and cellular deformability has long been ... more Splenic sequestration of RBCs with reduced surface area and cellular deformability has long been recognized as contributing to pathogenesis of several RBC disorders, including hereditary spherocytosis. However, the quantitative relationship between the extent of surface area loss and splenic entrapment remains to be defined. To address this issue, in the present study, we perfused ex vivo normal human spleens with RBCs displaying various degrees of surface area loss and monitored the kinetics of their splenic retention. Treatment with increasing concentrations of lysophosphatidylcholine resulted in a dose-dependent reduction of RBC surface area at constant volume, increased osmotic fragility, and decreased deformability. The degree of splenic retention of treated RBCs increased with increasing surface area loss. RBCs with a > 18% average surface area loss (> 27% reduced surface area-to-volume ratio) were rapidly and completely entrapped in the spleen. Surface-deficient RBCs ap...

mBio, 2015

Severe malarial anemia (SMA) in semi-immune individuals eliminates both infected and uninfected e... more Severe malarial anemia (SMA) in semi-immune individuals eliminates both infected and uninfected erythrocytes and is a frequent fatal complication. It is proportional not to circulating parasitemia but total parasite mass (sequestered) in the organs. Thus, immune responses that clear parasites in organs may trigger changes leading to anemia. Here, we use an outbred-rat model where increasing parasite removal in the spleen escalated uninfected-erythrocyte removal. Splenic parasite clearance was associated with activated CD8 + T cells, immunodepletion of which prevented parasite clearance. CD8 + T cell repletion and concomitant reduction of the parasite load was associated with exacerbated (40 to 60%) hemoglobin loss and changes in properties of uninfected erythrocytes. Together, these data suggest that CD8 + T cell-dependent parasite clearance causes erythrocyte removal in the spleen and thus anemia. In children infected with the human malaria parasite Plasmodium falciparum, elevation...

Microbes and Infection, 2008

In contrast to young rats, adult rats given i.p. Plasmodium berghei Anka (PbA) control the parasi... more In contrast to young rats, adult rats given i.p. Plasmodium berghei Anka (PbA) control the parasitaemia and repair their anaemia. Here, we investigated whether IgE and CD23/NO immune pathway could be implicated in this age-related resistance of adult rats to PbA. Eight-week-old rats displayed significantly higher levels of plasma total IgE (p ¼ 0.01) and soluble CD23 (p ¼ 0.003) during the peak of parasitaemia, compared to 4-week-old rats. IgE Fc-binding antibody or aminoguanidine administration to parasitized 8-week-old rats slightly delayed blood parasite clearance or exacerbated anaemia. These data suggest that IgE and CD23/NO could play an important role in the resistance of adult rats experiencing PbA primary intraerythrocytic development.

Malaria Journal, 2008

Background: A simple real-time PCR assay using one set of primer and probe for rapid, sensitive a... more Background: A simple real-time PCR assay using one set of primer and probe for rapid, sensitive and quantitative detection of Plasmodium species, with simultaneous differentiation of Plasmodium falciparum from the three other Plasmodium species (Plasmodium vivax, Plasmodium ovale and Plasmodium malariae) in febrile returning travellers and migrants was developed and evaluated. Methods: Consensus primers were used to amplify a species-specific region of the multicopy 18S rRNA gene, and fluorescence resonance energy transfer hybridization probes were used for detection in a LightCycler platform (Roche). The anchor probe sequence was designed to be perfect matches to the 18S rRNA gene of the fourth Plasmodium species, while the acceptor probe sequence was designed for P. falciparum over a region containing one mismatched, which allowed differentiation of the three other Plasmodium species. The performance characteristics of the realtime PCR assay were compared with those of conventional PCR and microscopy-based diagnosis from 119 individuals with a suspected clinical diagnostic of imported malaria. Results: Blood samples with parasite densities less than 0.01% were all detected, and analytical sensitivity was 0.5 parasite per PCR reaction. The melt curve means Tms (standard deviation) in clinical isolates were 60.5°C (0.6°C) for P. falciparum infection and 64.6°C (1.8°C) for non-P. falciparum species. These Tms values of the P. falciparum or non-P. falciparum species did not vary with the geographic origin of the parasite. The real-time PCR results correlated with conventional PCR using both genus-specific (Kappa coefficient: 0.95, 95% confidence interval: 0.9-1) or P.

Biochemical Pharmacology, 2004

In Plasmodium falciparum-infected cells or in P. berghei infected mice, increase of reduced gluta... more In Plasmodium falciparum-infected cells or in P. berghei infected mice, increase of reduced glutathione (GSH) levels confers resistance to chloroquine (CQ). GSH is synthesized within the cells through a complex biochemical pathway composed of several well known enzymes, in which glucose-6-phosphate dehydrogenase (G6PD) plays an important role. The physiological hormone dehydroepiandrosterone sulfate (DHEAS) is a potent inhibitor of G6PD activity, and G6PD deficiency is known to exert antimalaria protection. This study aimed to investigate the ability of DHEAS to enhance the antimalarial activity of CQ, via an inhibition of G6PD activity and GSH synthesis. Two P. berghei CQ resistant strains (CQR6 and CQR30) were selected in vivo from the sensitive strain NK65. Drug effects were checked both by monitoring the evolution of parasitaemia and by the survival of infected mice. In addition, intra-parasite levels of GSH and G6PD activity were measured before and after the treatment. Results demonstrate that acquisition of CQ resistance in P. berghei is associated with a significant increase in parasite G6PD activity and GSH level. Combination of CQ with DHEAS or buthionin sulfoximin (BSO, a specific inhibitor of GSH synthesis) significantly increased sensitivity of resistant parasites to CQ and increased the survival period of the infected mice. This reduction of parasitaemia and improvement of the survival of infected mice were associated with intraparasite depletion of GSH and inhibition of G6PD activity due to DHEAS action. This experimental study suggests that DHEAS could be used to potentiate antimalarial action of CQ, particularly on CQ resistant strains.

Biochimica et Biophysica Acta (BBA) - Biomembranes, 1982

PLOS Medicine

Background A very large biomass of intact asexual-stage malaria parasites accumulates in the sple... more Background A very large biomass of intact asexual-stage malaria parasites accumulates in the spleen of asymptomatic human individuals infected with Plasmodium vivax. The mechanisms underlying this intense tropism are not clear. We hypothesised that immature reticulocytes, in which P. vivax develops, may display high densities in the spleen, thereby providing a niche for parasite survival. Methods and findings We examined spleen tissue in 22 mostly untreated individuals naturally exposed to P. vivax and Plasmodium falciparum undergoing splenectomy for any clinical indication in malaria-endemic Papua, Indonesia (2015 to 2017). Infection, parasite and immature reticulocyte density, and splenic distribution were analysed by optical microscopy, flow cytometry, and molecular assays. Nine non-endemic control spleens from individuals undergoing spleno-pancreatectomy in France (2017 to 2020) were also examined for reticulocyte densities. There were no exclusion criteria or sample size consid...