BACKGROUNDThe replication-competent recombinant vesicular stomatitis virus (rVSV)-based vaccine expressing a Zaire ebolavirus (ZEBOV) glycoprotein was selected for rapid safety and immunogenicity testing before its use in West Africa. METHODSWe performed three open-label, dose-escalation phase 1 trials and one randomized, double-blind, controlled phase 1 trial to assess the safety, side-effect profile, and immunogenicity of rVSV-ZEBOV at various doses in 158 healthy adults in Europe and Africa. All participants were injected with doses of vaccine ranging from 300,000 to 50 million plaque-forming units (PFU) or placebo. RESULTSNo serious vaccine-related adverse events were reported. Mild-to-moderate early-onset reactogenicity was frequent but transient (median, 1 day). Fever was observed in up to 30% of vaccinees. Vaccine viremia was detected within 3 days in 123 of the 130 participants (95%) receiving 3 million PFU or more; rVSV was not detected in saliva or urine. In the second week after injection, arthritis affecting one to four joints developed in 11 of 51 participants (22%) in Geneva, with pain lasting a median of 8 days (interquartile range, 4 to 87); 2 self-limited cases occurred in 60 participants (3%) in Hamburg, Germany, and Kilifi, Kenya. The virus was identified in one synovial-fluid aspirate and in skin vesicles of 2 other vaccinees, showing peripheral viral replication in the second week after immunization. ZEBOV-glycoprotein-specific antibody responses were detected in all the participants, with similar glycoprotein-binding antibody titers but significantly higher neutralizing antibody titers at higher doses. Glycoprotein-binding antibody titers were sustained through 180 days in all participants. CONCLUSIONSIn these studies, rVSV-ZEBOV was reactogenic but immunogenic after a single dose and warrants further evaluation for safety and efficacy.

Artemisinins are derived from extracts of sweet wormwood (Artemisia annua) and are well established for the treatment of malaria, including highly drug-resistant strains. Their efficacy also extends to phylogenetically unrelated parasitic infections such as schistosomiasis. More recently, they have also shown potent and broad anticancer properties in cell lines and animal models. In this review, we discuss recent advances in defining the role of artemisinins in medicine, with particular focus on their controversial mechanisms of action. This safe and cheap drug class that saves lives at risk from malaria can also have important potential in oncology.

In human erythrocytes infected with the mature form of the malaria parasite Plasmodium falciparum, the cytosolic concentration of Na(+) is increased and that of K(+) is decreased. In this study, the membrane transport changes underlying this perturbation were investigated using a combination of (86)Rb(+), (43)K(+), and (22)Na(+) flux measurements and a semiquantitative hemolysis technique. From >15 h postinvasion, there appeared in the infected erythrocyte membrane new permeation pathways (NPP) that caused a significant increase in the basal ion permeability of the erythrocyte membrane and that were inhibited by furosemide (0.1 mM). The NPP showed the selectivity sequence Cs(+) > Rb(+) > K(+) > Na(+), with the K(+)-to-Na(+) permeability ratio estimated as 2.3. From 18 to 36 h postinvasion, the activity of the erythrocyte Na(+)/K(+) pump increased in response to increased cytosolic Na(+) (a consequence of the increased leakage of Na(+) via the NPP) but underwent a progressive decrease in the latter 12 h of the parasite's occupancy of the erythrocyte (36-48 h postinvasion). Incorporation of the measured ion transport rates into a mathematical model of the human erythrocyte indicates that the induction of the NPP, together with the impairment of the Na(+)/K(+) pump, accounts for the altered Na(+) and K(+) levels in the host cell cytosol, as well as predicting an initial decrease, followed by a lytic increase in the volume of the host erythrocyte.

A recent study on malaria‐infected human red blood cells (RBCs) has shown induced ion channel activity in the host cell membrane, but the questions of whether they are host‐ or parasite‐derived and their molecular nature have not been resolved. Here we report a comparison of a malaria‐induced anion channel with an endogenous anion channel in Plasmodium falciparum‐infected human RBCs. Ion channel activity was measured using the whole‐cell, cell‐attached and excised inside‐out configurations of the patch‐clamp method. Parasitised RBCs were cultured in vitro, using co‐cultured uninfected RBCs as controls. Unstimulated uninfected RBCs possessed negligible numbers of active anion channels. However, anion channels could be activated in the presence of protein kinase A (PKA) and ATP in the pipette solution or by membrane deformation. These channels displayed linear conductance (∼15 pS), were blocked by known anion channel inhibitors and showed the permeability sequence I− > Br− > Cl−. In addition, in less than 5 % of excised patches, an outwardly rectifying anion channel (∼80 pS, outward conductance) was spontaneously active. The host membrane of malaria‐infected RBCs possessed spontaneously active anion channel activity, with identical conductances, pharmacology and selectivity to the linear conductance channel measured in stimulated uninfected RBCs. Furthermore, the channels measured in malaria‐infected RBCs were shown to have a low open‐state probability (Po) at positive potentials, which explains the inward rectification of membrane conductance observed when using the whole‐cell configuration. The data are consistent with the presence of two endogenous anion channels in human RBCs, of which one (the linear conductance channel) is up‐regulated by the malaria parasite P. falciparum.

Iron is an essential micronutrient but is also highly toxic. In yeast and plant cells, a key detoxifying mechanism involves iron sequestration into intracellular storage compartments, mediated by members of the vacuolar iron-transporter (VIT) family of proteins. Here we study the VIT homologue from the malaria parasites Plasmodium falciparum (PfVIT) and Plasmodium berghei (PbVIT). PfVIT-mediated iron transport in a yeast heterologous expression system is saturable (Km∼14.7 μM), and selective for Fe2+ over other divalent cations. PbVIT-deficient P. berghei lines (Pbvit−) show a reduction in parasite load in both liver and blood stages of infection in mice. Moreover, Pbvit− parasites have higher levels of labile iron in blood stages and are more sensitive to increased iron levels in liver stages, when compared with wild-type parasites. Our data are consistent with Plasmodium VITs playing a major role in iron detoxification and, thus, normal development of malaria parasites in their mammalian host.