Molecular characterisation of extracellular vesicles released by Strongyloides stercoralis infective larvae isolated from a clinical sample

Background: Extracellular vesicles (EVs) represent a key mechanism of host–pathogen crosstalk. Numerous helminth parasites have already been reported to shed EV-like structures carrying biomolecules, including small RNAs (sRNAs), with functional effects on target cells. However, the ability of Strongyloides stercoralis to release EVs has yet to be demonstrated. Methods and results: Following the isolation of S. stercoralis infective larvae (iL3s) from faecal samples obtained from a patient with strongyloidiasis, we showed that iL3s maintained in vitro for up to 48 h release EV-like structures. Transmission electron microscopy and nanoparticle tracking analysis highlighted vesicular structures enclosed by a bilayer and with a diameter of 120 nm in range. Small RNA sequencing identified multiple EV-associated sRNA types, including miRNAs, only partly overlapping with the previously described somatic miRNome. Comparative analyses revealed that several EV-associated miRNAs were conserved amongst Strongyloides spp., whereas others appeared specific to S. stercoralis. Prediction analyses indicated that miRNAs and other sRNAs may target human genes associated with the regulation of gene expression and immune response, supporting a potential role in host–parasite interaction. Conclusions: These findings provide the first experimental evidence that S. stercoralis iL3s release EVs carrying regulatory sRNAs and suggest that EV-mediated RNA delivery may represent an additional tool for host–pathogen interaction. More in-depth investigations of these EVs may provide novel insights into the pathophysiology of strongyloidiasis as well as novel targets for clinical applications.