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[Display omitted] • Total small extracellular vesicle (sEV) number and protein concentration positively correlated with parasitaemia. • Circulating sEVs contain parasite- and host-derived proteins implicated with immunity. • Novel sEV proteins are potential targets for protective immunity and vaccination. • sEVs may work as therapeutic targets or vehicles for immunomodulatory control. Small extracellular vesicles, including exosomes, are formed by the endocytic pathway and contain genetic and protein material which reflect the contents of their cells of origin. These contents have a role in vesicle-mediated information transfer, as well as physiological and pathological functions. Thus, these vesicles are of great interest as therapeutic targets, or as vehicles for immunomodulatory control. In Plasmodium spp. infections, vesicles derived from the parasite or parasite-infected cells have been shown to induce the expression of pro-inflammatory elements, which have been correlated with manifestations of clinical disease. Herein, we characterised the protein cargo of naturally occurring sEVs in the plasma of P. yoelii -infected mice. After in vivo infections, extracellular vesicles in the size range of exosomes were collected by sequential centrifugation/ultracentrifugation followed by isopycnic gradient separation. Analysis of the vesicles was performed by transmission electron microscopy, dynamic light scattering, SDS–PAGE and flow cytometry. LC-MS analysis followed by bioinformatics analysis predicted parasite protein cargo associated with exosomes. Within these small extracellular vesicles, we identified proteins of interest as vaccine candidates, uncharacterized proteins which may be targets of T cell immunoreactivity, and proteins involved in metabolic processes, regulation, homeostasis and immunity. Importantly, the small extracellular vesicles studied in our work were obtained from in vivo infection rather than from the supernatant of in vitro cultures. These findings add to the growing interest in parasite small extracellular vesicles, further our understanding of the interactions between host and parasite, and identify novel proteins which may represent potential targets for vaccination against malaria. [ABSTRACT FROM AUTHOR]

Herein we show for the first time that Schistosoma mansoni adult worms secrete exosome-like extracellular vesicles ranging from 50 to 130 nm in size. Extracellular vesicles were collected from the excretory/secretory products of cultured adult flukes and purified by Optiprep density gradient, resulting in highly pure extracellular vesicle preparations as confirmed by transmission electron microscopy and Nanosight tracking analysis. Extracellular vesicle proteomic analysis showed numerous known vaccine candidates, potential virulence factors and molecules implicated in feeding. These findings provide new avenues for the exploration of host–schistosome interactions and offer a potential mechanism by which some vaccine antigens exert their protective efficacy. [ABSTRACT FROM AUTHOR]

The tegument of Schistosoma mansoni plays an integral role in host–parasite interactions, particularly during the transition from the free-living cercariae to the intra-mammalian schistosomula stages. This developmental period is characterised by the transition from a trilaminate surface to a heptalaminate tegument that plays key roles in immune evasion, nutrition and excretion. Proteins exposed at the surface membranes of newly transformed schistosomula are therefore thought to be prime targets for the development of new vaccines and drugs for schistosomiasis. Using a combination of tegumental labelling and high-throughput quantitative proteomics, more than 450 proteins were identified on the apical membrane of S. mansoni schistosomula, of which 200 had significantly regulated expression profiles at different stages of schistosomula development in vitro, including glucose transporters, sterols, heat shock proteins, antioxidant enzymes and peptidases. Current vaccine antigens were identified on the apical membrane ( Sm -TSP-1, calpain) or sub-tegumental ( Sm -TSP-2, Sm 29) fractions of the schistosomula, displaying localisation patterns that, in some cases, differ from that in the adult stage fluke. This work provides the first known in-depth proteomic analysis of the surface-exposed proteins in the schistosomula tegument, and some of the proteins identified are clear targets for the generation of new vaccines and drugs against schistosomiasis. [ABSTRACT FROM AUTHOR]

Abstract: The ability of the mammalian blood fluke Schistosoma japonicum to survive in the inhospitable environment of the mammalian bloodstream can be attributed, at least in part, to its host-exposed outer surface, called the tegument. The tegument is a dynamic organ and is involved in nutrition, immune evasion and modulation, excretion, osmoregulation and signal transduction. Given its importance for parasite survival, proteins exposed to the host at the surface of the tegument are ideal targets for the development of vaccines and drugs. By biotinylating live adult worms and using a combination of OFFGEL electrophoresis and tandem mass spectrometry 54 proteins were identified as putatively host-exposed in S. japonicum. These included glucose transport proteins, an amino permease, a leucine aminopeptidase and a range of transporters, heat shock proteins and novel immune-active proteins. Members of the tetraspanin protein family and a homologue of Sm 29, a tegument membrane protein from Schistosoma mansoni, both effective vaccine antigens in S. mansoni, were also identified. The fate of labelled surface proteins was monitored over time using electron microscopy and revealed that biotinylated proteins were rapidly internalised from the surface of the tegument and trafficked into the cytoplasmic bridges that connect the distal cytoplasm of the tegument to the underlying cell bodies. The results reported herein dramatically increase the number of S. japonicum proteins known to be exposed to the host and, hence, those of interest as therapeutic targets. The ability of the parasite to rapidly internalise proteins at its surface has implications for the development of vaccines and may explain how these parasites are able to avoid the host immune system for long periods of time. [Copyright &y& Elsevier]