BackgroundControlled human malaria infection (CHMI) accelerates development of anti-malarial interventions. So far, CHMI is done by exposure of volunteers to bites of five mosquitoes carrying Plasmodium falciparum sporozoites (PfSPZ), a technique available in only a few centres worldwide. Mosquito-mediated CHMI is logistically complex, exact PfSPZ dosage is impossible and live mosquito-based interventions are not suitable for further clinical development.MethodsAn open-labelled, randomized, dose-finding study in 18–45 year old, healthy, malaria-naïve volunteers was performed to assess if intravenous (IV) injection of 50 to 3,200 aseptic, purified, cryopreserved PfSPZ is safe and achieves infection kinetics comparable to published data of mosquito-mediated CHMI. An independent study site verified the fully infectious dose using direct venous inoculation of PfSPZ. Parasite kinetics were assessed by thick blood smear microscopy and quantitative real time PCR.ResultsIV inoculation with 50, 200, 800, or 3,200 PfSPZ led to parasitaemia in 1/3, 1/3, 7/9, and 9/9 volunteers, respectively. The geometric mean pre-patent period (GMPPP) was 11.2 days (range 10.5–12.5) in the 3,200 PfSPZ IV group. Subsequently, six volunteers received 3,200 PfSPZ by direct venous inoculation at an independent investigational site. All six developed parasitaemia (GMPPP: 11.4 days, range: 10.4–12.3). Inoculation of PfSPZ was safe. Infection rate and pre-patent period depended on dose, and injection of 3,200 PfSPZ led to a GMPPP similar to CHMI with five PfSPZ-infected mosquitoes. The infectious dose of PfSPZ predicted dosage of radiation-attenuated PfSPZ required for successful vaccination.ConclusionsIV inoculation of PfSPZ is safe, well tolerated and highly reproducible. It shall further accelerate development of anti-malarial interventions through standardization and facilitation of CHMI. Beyond this, rational dose selection for whole PfSPZ-based immunization and complex study designs are now possible.Trial registrationClinicalTrials.gov NCT01624961 and NCT01771848.

Die Umsetzung des Carbodiphosphorans Ph3P=C=PPh3 (1) mit InMe3 in THF und von AlBr3 in Toluol liefert die Addukte [Me3In{C(PPh3)2}] (2) und [Br3Al{C(PPh3)2}] (3) mit sehr guten Ausbeuten. 1 reagiert nicht mit SnCl2 und Me3SnCl; als Nebenprodukt konnten jedoch geringe Mengen des Hydrolyseprodukts [HC(PPh3)2][Me3SnCl2] (6) als Einkristalle erhalten werden. 2 löst sich in HCCl3 unter Bildung der Salze [HC(PPh3)2][MeInCl3] (5a) und [HC(PPh3)2][Me2InCl2] (5b). Wenige Kristalle von [HC(PPh3)2][Me2In(OSiMe2OSiMe2O)] (4) wurden als Reaktionsprodukt von 2 mit dem Silikon‐Schliffett bei Kristallisationsversuchen von 2 erhalten. Beim Versuch, 2 mit CS2 in THF umzusetzen wurde das THF‐Spaltungsprodukt [HC(PPh3)2][CH3CH2CH2OCS2] (7) in 60 %iger Ausbeute erhalten. Sämtliche Verbindungen wurden durch Einkristallstrukturanalysen charakterisiert, inklusive das bei der Darstellung von 3 angefallene Nebenprodukt [Br3Al{OP(C6H5)2CH2P(C6H5)3}][AlBr4] (8) sowie die zur Synthese von 1 verwendete salzartige Verbindung [ClC(PPh3)2]Cl (9).

Specific inhibition of enzymes of the non-mevalonate pathway is a promising strategy for the development of novel antiplasmodial drugs. α-Aryl-substituted β-oxa isosteres of fosmidomycin with a reverse orientation of the hydroxamic acid group were synthesized and evaluated for their inhibitory activity against recombinant 1-deoxy-d-xylulose 5-phosphate reductoisomerase (IspC) of Plasmodium falciparum and for their in vitro antiplasmodial activity against chloroquine-sensitive and resistant strains of P. falciparum . The most active derivative inhibits IspC protein of P. falciparum (PfIspC) with an IC(50) value of 12 nM and shows potent in vitro antiplasmodial activity. In addition, lipophilic ester prodrugs demonstrated improved P. falciparum growth inhibition in vitro.

The duration of intrahost replication influences in vitro var gene transcript patterns. Differences between premosquito and postpatient cultures decrease with prolonged in vitro growth.