Detoxome Capacity of the Adult Rumen Fluke Calicophoron daubneyi Extends into Its Secreted Extracellular Vesicles

Helminth parasites have long adapted to survive hostile host environments and can likely adapt against the chemical anthelmintic challenge. One proposed adaptation route is via Phase I and II xenobiotic metabolizing enzymes (XMEs). For successful Helminth pharmacotherapy discovery programs, a working understanding of Helminth-derived chemical detoxification, the Helminth detoxome, is a must. At present, the detoxome of a newly emerging Helminth parasite, the rumen fluke Calicophoron daubneyi, remains unexplored. Thus, a combined bioinformatics, sub-, and global-proteomic approach has been employed to examine the detoxome of adult C. daubneyi. Transcriptome analysis revealed a complement of Phase I (cytochrome P450s and monoamine oxygenases) and Phase II (glutathione transferases [GSTs] and sulfotransferases) XMEs. Affinity-led subproteomic exploration of the GSTs revealed six GST isoforms in adult rumen fluke (CdGST-Mu1-2, S1, and S3-5), with global approaches identifying additional GSTs (CdGST-O1-2, Z1, and S2) and a unique egg-specific variant (CdGST-S6). Examination of C. daubneyi extracellular vesicles revealed a GST profile replicating that of the adult with the absence of two isoforms (CdGST-S2 and S4), with an additional identification of a sulfotransferase. These data represent the first exploration into the complete rumen fluke detoxification capacity and will provide direction for future anthelmintic discovery programs.