miRNA profile of extracellular vesicles isolated from saliva of Haemaphysalis longicornis tick

Extracellular vesicles (EVs) play a key role in host-parasite interactions. Previous studies have shown that parasites can release microRNA (miRNA) containing EVs, which can transfer their contents to host cells and regulate gene expression in recipient cells. However, a little is known about the secretion of EVs by the ticks. This study was therefore, carried out to examine the saliva of ticks for the presence of miRNA containing EVs. Vesicles were purified from saliva of partially engorged Haemaphysalis longicornis ticks. Transmission electron microscopy (TEM) was carried out to confirm that vesicles within saliva were EVs based on size and morphology. Total RNA was extracted from EVs and was analyzed by deep sequencing to determine miRNA profile. TEM analysis confirmed the presence of extracellular vesicle-like structures within tick saliva. RNA-seq analysis showed that tick-derived EVs contained small non-coding RNA populations including miRNAs. The analysis of tick-derived EVs identified 36 known miRNAs, 34 novel miRNAs and 842 novel Piwi-interacting RNAs (piRNA). The results of this study provide evidence that EVs containing miRNAs can be secreted by the ticks and suggest that vesicles could transfer these miRNAs to modulate host cell functions.