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Abstract

BackgroundIntraerythrocytic malaria parasites actively import obligate nutrients from serum and export proteins and lipids to erythrocyte cytoplasm and membrane. The import of macromolecules in the malaria parasite has been the subject of many debates. To understand the import of macromolecules by the parasite, we studied the uptake of proteins by Plasmodium falciparum infected human erythrocyte.MethodsProteins were biotin labelled individually, purified on a gel filtration column and added to uninfected and infected asynchronized culture. The uptake of these proteins by malaria parasites was determined by western blot analysis of parasite pellet and their different fractions using streptavidin-horseradish conjugate. To further confirm this import, we studied the uptake of 125I-labelled proteins by western blot analysis as well as used direct immunofluorescence method.ResultsHere we show that biotin labelled and radio-iodinated polypeptides of molecular sizes in the range of 45 to 206 kDa, when added in the culture medium, get direct access to the parasite membrane through a membrane network by by-passing the erythrocyte cytosol. The import of these polypeptides is ATP-dependent as sodium azide treatment blocks this uptake. We also show that malaria parasites have the ability to take up and degrade biotin labelled human serum albumin, which has been shown to be essential for the parasite growth.ConclusionsThese results can be used, as a basis to explore the role of human serum albumin in the intraerythrocytic development of parasites, and this in turn can be an important adjunct to the development of novel antimalarial drugs.

An amphiphilic graft copolymer-based nanoparticle platform for reduction-responsive anticancer and antimalarial drug delivery

“…6 The relatively small average size of maximum 50 nm provides the basis for targeting cancer metastasis 7 and iRBCs in case of malaria. 36,41,42 Interestingly, the average diameter of self--assembled nanoparticles decreased with increasing hydrophilic content (f (PMOXA) , Fig. 1C).…”

“…38,39 Surprisingly, there is evidence that proteins, such as antibodies, 40 and small nanoparticles up to about 80 nm diameter have direct access to the parasite inside the RBC. 36,41,42 Several mechanisms for specific uptake of large molecules and nanoparticles by parasitized RBCs compared to RBCs have been proposed, 43 but this is an ongoing controversy. Similarly to passive tumor targeting via the EPR effect, this controversial "leakiness" of Plasmodium--infected RBCs (iRBCs) 36,41,42 can be exploited via a passive targeting strategy using non--functionalized, antimalarial--loaded nanoparticles.…”

“…36,41,42 Several mechanisms for specific uptake of large molecules and nanoparticles by parasitized RBCs compared to RBCs have been proposed, 43 but this is an ongoing controversy. Similarly to passive tumor targeting via the EPR effect, this controversial "leakiness" of Plasmodium--infected RBCs (iRBCs) 36,41,42 can be exploited via a passive targeting strategy using non--functionalized, antimalarial--loaded nanoparticles. Also here, smaller sized nanoparticles (sub--80 nm diameter) are needed, because the size--cutoff to efficiently reach intracellular malaria parasites of iRBCs is about 80 nm.…”

“…This delivery mechanism was also proposed by other research groups. 36,41,42 To reflect the potency of nanoparticle--based stabilization and delivery of small compounds, a one--day--old NileRed aqueous solution was additionally tested in the same way and compared to a fresh NileRed solution. It clearly showed that this model hydrophobic compound was not stable enough in solution for one day; it did not readily appear in the iRBCs compared to fresh dye (Fig.…”

“…In these in vitro settings, where no other cells apart from RBCs and iRBCs were present, developed antimalarials intrinsically target the iRBCs and uptake of bigger nanoparticles is slower compared to small molecule uptake. However, nanoparticles (< 80 nm diameter) 36,41,42 also passively target iRBCs compared to RBCs.…”