Both host and parasite non-coding RNAs co-ordinate the regulation of macrophage gene expression to reduce pro-inflammatory immune responses and promote tissue repair pathways during infection with fasciola hepatica

Parasitic worms (helminths) ensure their survival to establish chronic infection within mammalian hosts by strategically regulating their host s immune responses. Deciphering the mechanisms behind this immune modulation will inform the development of novel strategies for infection control. It is now understood that the co-ordinated control of gene expression by non-coding RNAs (ncRNA) underpins the activation and regulation of immune cells. However, it is also clear that pathogens (including helminths) secrete their own ncRNAs to manipulate host gene expression and influence immune outcomes to infection. To discriminate the contribution of host and helminth derived ncRNAs to the activation and/or regulation of innate immune responses during infection, we examined ncRNA expression in the peritoneal macrophages from mice infected with Fasciola hepatica. This revealed an enrichment of several parasitic-derived miRNAs (fhe-miR-277b-3p, fhe-miR-71a-5p, fhe-miR-125b-5p, fhe-miR-125a-5p) within macrophages at 6hr and 18hr after infection which is coincident with the parasite s migration through the peritoneal cavity. Target prediction analysis indicated that these Fasciola miRNAs regulated host genes associated with the activation of host pro-inflammatory macrophages (Hif1 , Nod1, Nlrp6 and P2rx7). Concomitantly, there was a distinct shift in host ncRNA expression in response to infection, which was most significant at 5 days post-infection. Although, analysis suggested that these host ncRNAs target a different cohort of genes (Adar1, Igf1 and Plec) to the parasite miRNAs, the functional outcome was predicted to be the same, with a reduced pro-inflammatory response and the promotion of a reparative/tolerant phenotype. Combined, these observations uncover the interplay between host and parasitic ncRNAs and reveals a complementary regulation of the immune response that allows the parasite to evade immune detection and promotes tissue repair for the host. This level of characterisation of the ncRNA landscape during helminth infection is highly novel and provides a new understanding of the molecular impact that these parasites have on host immune cells. Performed RNAseq and miRNA-seq on total RNA isolated from peritoneal macrophages harvested from mice infected with Fasciola hepatica at different timepoints including 6hr, 18hr and 5 days post infection and uninfected mice. Mice miRNAs, lncRNAs and mRNAs were assessed and Fasciola hepatica miRNAs were identified.