Focussed on Plasmodium falciparum blood stages, our research integrates identification of parasite virulence factors, disease mechanisms and field studies alongside investigations on potential drug targets, with the aim of developing new intervention tools, including improved therapy.

Parasite virulence factors & disease mechanisms

We concentrate on parasite factors remodelling the red blood cell (RBC) membrane. PfRESA, inserted during invasion, interacts with human spectrin. Reverse genetics, imaging and nanomechanics showed that PfRESA is essential to overcome the adverse consequences of exposure to febrile temperatures [1] and contributes to decreased deformability of ring-infected RBCs [2]. Work is underway to fine-dissect its role in the alterations of the RBC membrane in ring stages.

The varO adhesin, exported by mature parasite stages onto the RBC surface, mediates binding of uninfected RBCs (rosetting) (see Figure). Rosetting is consistently associated with severe malaria in African children. Studies in the Saimiri monkey showed that varO rosetting contributes to increased multiplication rate in vivo [3]. Recombinant proteins expressing individual PfEMP1VarO domains in their native conformation have been produced. Current work includes unravelling the molecular interactions involved in rosetting and investigation of acquisition of specific antibodies in populations living in malaria-endemic areas.

Comparison of the transcriptome of parasites from patients ex vivo and after culture adaptation identified genes only expressed in vivo. We concentrate on the subset coding for proteins with an export motif to the erythrocyte membrane, using a combination of reverse genetics, cellular biology and immunochemistry.

The spleen plays a central role in determining the fate of the RBCs in infected patients, and in controlling parasite load. To get insights into the physiology of parasite handling by the spleen, we have established an experimental isolated-perfused human spleen system, functionally validated by the efficient processing of artesunate-treated infected RBCs [4]. Current work dissects handling of untreated RBC infected with ring or mature stages. We seek to determine the respective contribution of altered mechanical vs. novel surface and antigenic properties to parasite retention /clearance.

Drug therapy, diagnostics and resistance

In collaboration with the Réseau des Instituts Pasteur, we investigate molecular mechanisms associated with emerging resistance to artemether [5] and spreading of resistant parasites in field settings. Current work includes analysis of the dynamic changes of the parasite transcriptome after exposure to lethal doses of artesunate.

In parallel, we invest efforts to develop novel diagnostic assays aiming at getting a better quantification of the parasite load in malaria patients.

We pursue efforts on promising novel anti-malarial drug target. SUB2 is a subtilisin-like protease involved in the essential maturation of merozoite surface proteins, a processing conserved across Plasmodium species. Current efforts concern the characterisation of the catalytic properties of SUB2, the development and selection PfSUB2-specific inhibitors using several strategies.

Keywords: red cell membrane, virulence, fever, pathogenicity, clearance, antimalarials, resistance

1. Diez Silva M, Cooke BM, Guillotte M, Buckingham DW, Sauzet JP, Le Scanf C, Contamin H, David P, Mercereau-Puijalon O, Bonnefoy S. 2005. A role for the Plasmodium falciparum RESA protein in resistance against heat shock demonstrated using gene disruption. Mol Microbiol. May;56(4):990-1003. PMID: 15853885

2. Mills JP, Diez-Silva M, Quinn DJ, Dao M, Tan KSW, Lim CT, Milon G, David PH, Mercereau-Puijalon O, Bonnefoy S, Suresh S. Effect of plasmodial RESA protein on deformability of human red blood cells harboring Plasmodium falciparum. Proc Nat Acad Sci USA 2007, 104 (22): 9213-9217

3. Jambou R, Legrand E, Niang M, Khim N, Lim P, Volney B, Ekala MT, Bouchier C, Esterre P, Fandeur T, Mercereau-Puijalon O. 2005. Resistance of Plasmodium falciparum field isolates to in-vitro artemether and point mutations of the SERCA-type PfATPase6. Lancet Dec 3;366(9501):1960-3. PMID: 16325698

4. Le Scanf C, Vigan-Womas I, Contamin H, Guillotte M , Bischoff E, Mercereau-Puijalon O. Rosetting is associated with increased Plasmodium falciparum in vivo multiplication rate in the Saimiri sciureus monkey. Microbes and Infection 2008, in press

5. Buffet PA, Milon G, Brousse V, Correas JM, Dousset B, Couvelard A, Kianmanesh R, Farges O, Sauvanet A, Paye F, Ungeheuer MN, Ottone C, Khun H, Fiette L, Guigon G, Huerre M, Mercereau-Puijalon O, David PH. 2006. Ex-vivo perfusion of human spleens maintains clearing and processing functions Blood, May 1;107(9):3745-52. PMID: 16384927