Résumé
MiRNAs are short, single-stranded non-coding sequences that play a crucial role in the regulation of gene transcription in many biological processes such as embryonic development, cell proliferation, apoptosis or immunity. Indeed, miRNAs are known to regulate the host’s internal defense system and the immune cell response, which is a crucial process in host-parasite interactions. We have previously described a constitutive set of miRNAs, the so-called miRNome, in Biomphalaria glabrata snails, the primary intermediate host of the trematode parasite Schistosoma mansoni, the causative agent of schistosomiasis. This B. glabrata miRNome is characterized from the hemolymph, known as the main immune-related tissue of the snail, which contains circulating haemocytes, the snail’s innate immune cells. Here, we investigate thanks to a massive sequencing approach of small RNAs, if some parasite’s miRNAs may be identified in haemocytes or circulating in the snail hemolymph. The present study was done by comparing different strains of parasite originating from different geographical localities and interacting with strains of B. glabrata respectively selected for their high level of compatibility. Our results reveal specific miRNAs that are exclusively expressed in some specific strains of parasites, suggesting a specificity of expression for the miRNAs. In vitro and in vivo approaches revealed the strategy of cell-to-cell communication of S. mansoni using exosome-like vesicles to target specific cells or tissue of his host and deliver his miRNAs. One question remains : does the parasite unify infection strategies in intermediate and final host infections ?