Extracellular vesicles: new targets for vaccines against helminth parasites

Graphical abstract
Highlights • Current vaccine candidates against helminth infection have shown limited success. • Helminths release extracellular vesicles (EVs) which act on host cells and are a rich source of antigens for new vaccines. • The biogenesis, release and immunomodulatory functions of helminth EVs are reviewed. • Utilisation of EVs in vaccine generation are discussed, including potential antigens and routes of delivery.
The hunt for effective vaccines against the major helminth diseases of humans has yet to bear fruit despite much effort over several decades. No individual parasite antigen has proved to elicit full protective immunity, suggesting that combinatorial strategies may be required. Recently it has been discovered that extracellular vesicles released by parasitic helminths contain multiple potential immune modulators, which could together be targeted by a future vaccine. Increasing knowledge of helminth extracellular vesicle components, both enclosed by and exposed on the membrane, will open up a new field of targets for an effective vaccine. This review discusses the interactions between helminth extracellular vesicles and the immune system discovered thus far, and the advantages of targeting these lipid-bound packages with a vaccine. In addition, we also comment upon specific antigens that may be the best targets for an anti-helminth vaccine. In the future, extensive knowledge of the parasites' full arsenal in controlling their host may finally provide us with the ideal target for a fully effective vaccine.