IgG acquisition against PfEMP1 PF11_0521 domain cassette DC13, DBLß3_D4 domain, and peptides located within these constructs in children with cerebral malaria.

The Plasmodium falciparum erythrocyte-membrane-protein-1 (PF3D7_1150400/PF11_0521) contains both domain cassette DC13 and DBLß3 domain binding to EPCR and ICAM-1 receptors, respectively. This type of PfEMP1 proteins with dual binding specificity mediate specific interactions with brain micro-vessels endothelium leading to the development of cerebral malaria (CM). Using plasma collected from children at time of hospital admission and after 30 days, we study an acquisition of IgG response to PF3D7_1150400/PF11_0521 DC13 and DBLß3_D4 recombinant constructs, and five peptides located within these constructs, specifically in DBLα1.7_D2 and DBLß3_D4 domains. We found significant IgG responses against the entire DC13, PF11_0521_DBLß3_D4 domain, and peptides. The responses varied against different peptides and depended on the clinical status of children. The response was stronger at day 30, and mostly did not differ between CM and uncomplicated malaria (UM) groups. Specifically, the DBLß3 B3-34 peptide that contains essential residues involved in the interaction between PF11_0521 DBLß3_D4 domain and ICAM-1 receptor demonstrated significant increase in reactivity to IgG1 and IgG3 antibodies at convalescence. Further, IgG reactivity in CM group at time of admission against functionally active (ICAM-1-binding) PF11_0521 DBLß3_D4 domain was associated with protection against severe anemia. These results support development of vaccine based on the PF3D7_1150400/PF11_0521 structures to prevent CM.

Synthesis and antiplasmodial activity of new indolone N-oxide derivatives.

A series of 66 new indolone-N-oxide derivatives was synthesized with three different methods. Compounds were evaluated for in vitro activity against CQ-sensitive (3D7), CQ-resistant (FcB1), and CQ and pyrimethamine cross-resistant (K1) strains of Plasmodium falciparum (P.f.), as well as for cytotoxic concentration (CC(50)) on MCF7 and KB human tumor cell lines. Compound 26 (5-methoxy-indolone-N-oxide analogue) had the most potent antiplasmodial activity in vitro (<3 nM on FcB1 and = 1.7 nM on 3D7) with a very satisfactory selectivity index (CC(50) MCF7/IC(50) FcB1: 14623; CC(50) KB/IC(50) 3D7: 198823). In in vivo experiments, compound 1 (dioxymethylene derivatives of the indolone-N-oxide) showed the best antiplasmodial activity against Plasmodium berghei, 62% inhibition of the parasitaemia at 30 mg/kg/day.

Molecular epidemiology of malaria in Cameroon. XXVIII. In vitro activity of dihydroartemisinin against clinical isolates of Plasmodium falciparum and sequence analysis of the P. falciparum ATPase 6 gene.

The Plasmodium falciparum ATPase 6 (Pfatp6), homolog of sarco-endoplasmic reticulum, calcium-dependent ATPase in malaria parasites, has been proposed to be the main target of artemisinins. Four distinct point mutations (L263E, E431K, A623E, and S769N) have been reported to be associated with artemisinin resistance. The Pfatp6 sequence polymorphism was determined to evaluate the prevalence of these mutations in fresh clinical isolates in Yaounde, Cameroon, and compare sequence data with in vitro response to dihydroartemisinin. Two major haplotypes were observed: the wild-type LEAS (n = 60, 62%) and a single mutant LKAS (n = 35, 36%). These amino acid substitutions did not influence the level of in vitro response to dihydroartemisinin (P > 0.05). Plasmodium falciparum isolates from Cameroon are highly sensitive in vitro to artemisinins. However, the relatively high prevalence of E431K may be a warning signal that warrants a regular monitoring of these molecular markers and/or in vitro activity of artemisinin derivatives.