[Prevention and treatment of malaria: in vitro evaluation of new compounds]. / Prophylaxie et traitement du paludisme: évaluation in vitro de nouveaux composés.

One of the current options for reducing the morbidity and mortality of malaria are chemoprophylaxis and chemotherapy. For this reason, the increasing prevalence of strains of Plasmodium falciparum resistant to chloroquine and other antimalarial drugs poses a serious problem for control of malaria. There is an urgent need to find and develop novel compounds and to identify novel chemotherapeutic targets. Different approaches to discover new compounds are presented from examples of molecules studied in the Tropical Medicine Institute of the French Army Health Service (IMTSSA) evaluation against isolates of compounds in pharmaceutical development in collaboration with pharmaceuticals (pyronaridine, benflumetol, ferrochloroquine), screening of molecules which are still registered for other pathologies (antibiotics), screening of new synthesized compounds (artemisinin derivatives) and identification of parasitical targets and essential metabolic ways for parasite, and identification of molecules acting on these targets (reversal of resistance to chloroquine, iron chelators).

Recombinant human thrombomodulin(csa+): a tool for analyzing Plasmodium falciparum adhesion to chondroitin-4-sulfate.

The proteoglycan thrombomodulin has been shown to be involved, via its chondroitin-sulfate moiety, in the cytoadhesion of chondroitin-4-sulfate-binding-Plasmodium falciparum-infected erythrocytes to endothelial cells and syncytiotrophoblasts. We cloned and expressed in CHO and COS-7 cells a gene encoding soluble human recombinant thrombomodulin, with a chondroitin-4-sulfate moiety. This system is complementary to the in vitro cell models currently used to study the chondroitin-4-sulfate-binding phenotype. It also provides a means of overcoming the lack of specificity observed in interactions of infected erythrocytes with modified chondroitin-4-sulfate. This thrombomodulin displayed normal activity in coagulation, indicating that it was in a functional conformation. The recombinant protein, whether produced in CHO or COS-7 cells, inhibited cytoadhesion to Saimiri brain microvascular endothelial cells 1D infected with Palo-Alto(FUP)1 parasites selected for chondroitin-4-sulfate receptor preference. Thus, the recombinant protein was produced with a chondroitin-sulfate moiety, identified as a chondroitin-4-sulfate, in both cell types. In both cases, the recombinant protein bound to the chondroitin-4-sulfate phenotype, but not to CD36- and ICAM-1-binding parasites. The chondroitin-4-sulfate was 36 kDa in size for CHO and 17.5 kDa for COS-7 cells. There was, however, no difference in the capacities of the recombinant proteins produced by the two cell types to inhibit the cytoadhesion of infected erythrocytes. Thrombomodulin immobilized on plastic or coupled to Dynabeads was used to purify specifically the infected erythrocytes that bind to chondroitin-4-sulfate. These infected erythrocytes were cultured to establish parasite lines of this phenotype. We then showed that the thrombomodulin, labeled with FITC, could be used to detect this phenotype in blood samples. Finally, the direct binding of infected erythrocytes to immobilized thrombomodulin was used to screen for anti-chondroitin-4-sulfate-binding antibodies.