Starvation induces changes in abundance and small RNA cargo of extracellular vesicles

The lethal malaria parasite Plasmodium falciparum needs to constantly respond and adapt to changes within the human host in order to survive and transmit. One such change is composed of nutritional limitation, which is augmented with increased parasite loads and intimately linked to severe disease development. Extracellular vesicles released from infected red blood cells have been proposed as important mediators of disease pathogenesis and intercellular communication but whether important for the parasite response to nutritional availability is unknown.

Karolinska Institutet researchers investigated the abundance and small RNA cargo of extracellular vesicles released upon short-term nutritional starvation of P. falciparum in vitro cultures. They show that primarily ring-stage parasite cultures respond to glucose and amino acid deprivation with an increased release of extracellular vesicles. Small RNA sequencing of these extracellular vesicles further revealed human miRNAs and parasitic tRNA fragments as the main constituent biotypes. Short-term starvations led to alterations in the transcriptomic profile, most notably in terms of the over-represented biotypes. These data suggest a potential role for extracellular vesicles released from P. falciparum infected red blood cells in the response to nutritional perturbations, their potential as prognostic biomarkers and point towards an evolutionary conserved role among protozoan parasites.

The parasitic small RNA cargo of EVs is correlated
to the degree and type of nutritional starvation

(A) Supervised correlation heatmap of normalized read counts for all parasitic transcripts displaying Log₂ FC ≤ − 1 or ≥ 1 from three biological replicates of the different starvation conditions compared to control. Rows were ordered based on transcript biotypes whereas columns were clustered based on treatment conditions. (B) Correlation heatmap of all parasitic tRNAs fragments displaying Log₂ FC ≤ − 1 or ≥ 1 from three biological replicates of starvations. Rows represents unique tRNA fragments and columns the different starvation conditions. (C) GO term enrichment analysis of biological processes for all parasite transcripts with an average Log₂ FC ≤ − 1 or ≥ 1. The top 15 GO terms (all with p ≤ 0.05) are displayed. (D) KEGG pathway analysis for all parasite transcripts with an average Log₂ FC ≤ − 1 or ≥ 1. All significantly enriched (p ≤ 0.05) pathways are displayed.