Abstract
Background: Many pathogens secrete effector molecules to subvert host immune responses, to acquire nutrients, and/or to prepare host cells for invasion. One of the ways that effector molecules are secreted is through extracellular vesicles (EVs) such as exosomes. Recently, the malaria parasite P. falciparum has been shown to produce EVs that can mediate transfer of genetic material between parasites and induce sexual commitment. Characterizing the content of these vesicles may improve our understanding of P. falciparum pathogenesis and virulence. Methods: Previous studies of P. falciparum EVs have been limited to long-term adapted laboratory isolates. In this study, we isolated EVs from a Kenyan P. falciparum clinical isolate adapted to in vitro culture for a short period and characterized their protein content by mass spectrometry (data are available via ProteomeXchange, with identifier PXD006925). Results: We show that P. falciparum extracellular vesicles (PfEVs) are enriched in proteins found within the exomembrane compartments of infected erythrocytes such as Maurer’s clefts (MCs), as well as the secretory endomembrane compartments in the apical end of the merozoites, suggesting that these proteins play a role in parasite-host interactions. Comparison of this novel clinically relevant dataset with previously published datasets helps to define a core secretome present in Plasmodium EVs. Conclusions: P. falciparum extracellular vesicles contain virulence-associated parasite proteins. Therefore, analysis of PfEVs contents from a range of clinical isolates, and their functional validation may improve our understanding of the virulence mechanisms of the parasite, and potentially identify targets for interventions or diagnostics.
Highlights
Plasmodium falciparum malaria remains a major public health problem, with 212 million cases of malaria and half a million deaths due to severe malaria reported worldwide in 20151
Extracellular vesicles were purified from culture conditioned media of a recently adapted P. falciparum isolate We isolated Pf extracellular vesicles (EVs) from culture-conditioned media of a Kenyan P. falciparum clinical isolate adapted to in vitro culture
To further purify the pelleted vesicles, the pellet was re-suspended in PBS and subjected to OptiPrep density gradient ultracentrifugation as described in the Methods. 1ml fractions drawn from the top of the gradient were collected, and as shown in Figure 1c, lane 9, 10, and 11 contained several protein bands, whereas the rest of the fractions contained a single band representing albumin, a common contaminant co-pelleted with EVs
Summary
Plasmodium falciparum malaria remains a major public health problem, with 212 million cases of malaria and half a million deaths due to severe malaria reported worldwide in 20151. Results: We show that P. falciparum extracellular vesicles (PfEVs) are enriched in proteins found within the exomembrane compartments of infected erythrocytes such as Maurer’s clefts (MCs), as well as the secretory endomembrane compartments in the apical end of the merozoites, suggesting that PfEVs may play a role in parasite-host interactions. Comparison of this dataset with previously published datasets helps to define a core secretome present in PfEVs. Conclusions: P. falciparum extracellular vesicles contain virulence-associated parasite proteins. Analysis of PfEVs contents from a range of clinical isolates, and their functional validation may improve our understanding of the virulence mechanisms of the parasite, and potentially identify new targets for interventions or diagnostics
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