Authors

Discussion

Proteins of unknown function are commonly found in genomic, transcriptomic and proteomic studies of parasites. Notably, many of these proteins possess limited homologies that are often restricted to parasitic species, highlighting these proteins as potential intervention targets. One of these unknown proteins, Smp_075420, has been found to be present in extracellular vesicles and the tegument of the parasitic trematode Schistosoma mansoni. Therefore this protein has been named, S. mansoni Extracellular vesicle/Tegumental Unknown protein -1 (SmETU-1). Through extensive genomic searches, PCR cloning, transcription analysis, homolog searches and phylogenetics we describe the current knowledge of how widespread the ETU family are within parasite species. We find nine family members within S. mansoni (SmETU-1-9) with differing expression patterns across the parasite lifecycle and homologs in key platyhelminth species but not outside this phylum. Importantly, searches of published proteomic data find that the association of this novel protein family with Extracellular vesicles continues outside of the schistosome genus. Finally recombinant expression of SmETU-1 has been carried out for the purposes of testing serological immunogenicity in infected mouse and human studies via ELISA. These show antibody responses to this unknown protein are present in both experimental models and natural infection in endemic communities. In future, we aim to use localisation experiments such as whole-mount in situ hybridisation and additional functional and immunological studies to characterise this novel protein family further.