Extracellular Vesicles from Parasitic Helminths Contain Specific Excretory/Secretory Proteins and Are Internalized in Intestinal Host Cells

TLDR

Host–parasite interaction research has focused on parasite surface or excretory/secretory proteins as therapeutic or diagnostic targets, while recent advances in extracellular vesicle biology reveal exosomes (30–100 nm) that carry atypical secreted proteins across diverse organisms, including parasitic protozoa. This study seeks to demonstrate that trematodes *Echinostoma caproni* and *Fasciola hepatica* produce exosome‑like vesicles. The authors provide experimental evidence—proteomic analysis, immunogold labeling, and electron microscopy—to confirm the existence of these vesicles. The vesicles are actively released, internalized by host intestinal cells, contain most known parasite ESP proteins as well as host proteins, indicating a potential role in host‑parasite communication.

Abstract

The study of host-parasite interactions has increased considerably in the last decades, with many studies focusing on the identification of parasite molecules (i.e. surface or excretory/secretory proteins (ESP)) as potential targets for new specific treatments and/or diagnostic tools. In parallel, in the last few years there have been significant advances in the field of extracellular vesicles research. Among these vesicles, exosomes of endocytic origin, with a characteristic size ranging from 30-100 nm, carry several atypical secreted proteins in different organisms, including parasitic protozoa. Here, we present experimental evidence for the existence of exosome-like vesicles in parasitic helminths, specifically the trematodes Echinostoma caproni and Fasciola hepatica. These microvesicles are actively released by the parasites and are taken up by host cells. Trematode extracellular vesicles contain most of the proteins previously identified as components of ESP, as confirmed by proteomic, immunogold labeling and electron microscopy studies. In addition to parasitic proteins, we also identify host proteins in these structures. The existence of extracellular vesicles explains the secretion of atypical proteins in trematodes, and the demonstration of their uptake by host cells suggests an important role for these structures in host-parasite communication, as described for other infectious agents.