Aminoquinolines afford resistance to cerebral malaria in susceptible mice

Objectives: Malaria treatment is impeded by increasing resistance to conventional antimalarial drugs. Here we explored the activity of ten novel benzothiophene, thiophene and benzene aminoquinolines. Methods: In vitro testing was performed by the lactate dehydrogenase assay in chloroquine (CQ)-sensitive Plasmodium falciparum strain 3D7 and CQ-resistant (CQ(R)) P. falciparum strain Dd2. In vivo activity was evaluated by a modified Thompson test using C57BL/6 mice infected with Plasmodium berghei ANKA strain. Results: Nine of the ten compounds had a lower 50% inhibitory concentration (IC50) than CQ against the CQ(R) strain Dd2. Five of these compounds that were available for in vivo evaluation were shown to be nontoxic. All five compounds administered at a dose of 160 mg/kg/day for 3 days prolonged the survival of treated compared with untreated mice. Untreated control mice died by Day 7 with a mean parasitaemia of 15%. Among treated mice, a dichotomous outcome was observed, with a two-third majority of treated mice dying by Day 17 with a low mean parasitaemia of 5%, whilst one-third survived longer with a mean hyperparasitaemia of 70%; specifically, five of these mice survived a mean of 25 days, whilst two even survived past Day 31. Conclusions: The significant antimalarial potential of this aminoquinoline series is illustrated by its excellent in vitro activity against the CQ(R) P. falciparum strain and significant in vivo activity. Interestingly, compounds CIAQ7, CIAQ9 and CIAQ11 were able to confer resistance to cerebral malaria and afford a switch to hyperparasitaemia to mice prone to the neurological syndrome

Completing the hypusine pathway in Plasmodium: Deoxyhypusine hydroxylase is an E-Z type HEAT repeat protein

In searching for new targets for antimalarials we investigated the biosynthesis of hypusine present in eukaryotic initiation factor-5A (eIF-5A) in Plasmodium. Here, we describe the cloning and expression of deoxyhypusine hydroxylase (DOHH), which completes the modi. cation of eIF-5A through hydroxylation of deoxyhypusine. The dohh cDNA sequence revealed an ORF of 1236 bp encoding a protein of 412 amino acids with a calculated molecular mass of 46.45 kDa and an isoelectric point of 4.96. Interestingly, DOHH from Plasmodium has a FASTA SCORE of only 27 compared with its human ortholog and contains several matches similar to E-Z-type HEAT-like repeat proteins (IPR004155 (InterPro), PF03130 (Pfam), SM00567 (SMART) present in the phycocyanin lyase subunits of cyanobacteria. Purified DOHH protein displayed hydroxylase activity in a novel in vitro DOHH assay, but phycocyanin lyase activity was absent. dohh is present as a single-copy gene and is transcribed in the asexual blood stages of the parasite. A signal peptide at the N-terminus might direct the protein to a different cellular compartment. During evolution, Plasmodium falciparum acquired an apicoplast that lost its photosynthetic function. It is possible that plasmodial DOHH arose from an E/F-type phycobilin lyase that gained a new role in hydroxylation