Authors

S Clancy¹; M Robinson¹; RM Morphew²; SA Huws¹;  ¹ Queen's University Belfast, UK;  ² Aberystwyth University, UK

Discussion

The rumen fluke, Calicophoron daubneyi, is a parasitic trematode that infects ruminants such as sheep and cattle. Adult parasites reside within the rumen, where they attach themselves to the epithelium using a muscular posterior sucker. This location means that they are in intimate contact with host tissues as well as the rumen microbiome, a unique collection of bacteria, archaea, fungi and protozoa. To date, few studies have investigated the relationship between helminth parasites and the microbiome of domestic livestock. Here, we have exploited multi-omics resources for C. daubneyi in order to identify potential homologs of innate immune system molecules secreted by the parasite. These include molecules which may either possess direct antimicrobial activity or function as pathogen recognition receptors (PRRs), innate immune system molecules that recognise pathogen-associated molecular patterns (PAMPs). Whilst a number of innate immune molecule homologs have been identified, two putative PRRs, namely, peptidoglycan-recognition receptors (PGRPs) and DM9-containing proteins (DM9CPs), were found to exist as multi-member families which have undergone significant expansion in C. daubneyi compared to other helminth species. A family of saposin-like proteins (SAPLIPs), with putative antimicrobial activity, have undergone similar expansion in C. daubneyi. Our data suggest that, due to the unique selection pressures associated with its microbe-rich niche, C. daubneyi has have evolved a complex innate immune system which allows the parasite to recognise and respond to microbes within the rumen. This research represents an important first step towards a greater understanding of rumen fluke-microbiome interactions and provides a framework for functional studies of helminth innate immune system molecules.