Molecular changes in Opisthorchis viverrini (Southeast Asian liver fluke) during the transition from the juvenile to adult stage
The Southeast Asian liver fluke (Opisthorchis viverrini) chronically infects and affects millions of people in parts of Asia. The disease caused by this parasite (= opisthorchiasis) can lead to chronic illness and, importantly, is known to induce malignant cancer (= cholangiocarcinoma). In spite of the substantial socio-economic impact of O. viverrini, little is known, at the molecular level, about the parasite itself, its interplay with its hosts and the mechanisms underpinning disease and/or carcinogenesis. Here, we generated extensive RNA-seq data from transcript libraries representing adult and juvenile stages of O. viverrini using the Illumina GAII platform. These data were combined with previously published transcriptomic data for this species (based on 454 technology), yielding a combined assembly of significantly increased quality and allowing quantitative assessment of transcription in the juvenile and adult stage of this species. This new assembly reveals that despite the substantial biological similarities between the human liver flukes, Clonorchis sinensis and Opisthorchis viverinni, there are distinct and previously unrecognized differences in major aspects of their molecular biology, including significant differences in the asparaginyl endopeptidase-like and cathepsin L-like cysteine peptidases (which are highly transcribed in juvenile O. viverrini) which are known to play key roles in major parasitological functions including tissue migration, immuno-evasion and feeding. We also propose an alternative hypothesis for the evolution of these key molecules (which are both drug and vaccine targets) among the socioeconomically important trematodes that suggests gene loss as a major shaping force among the fluke cysteine peptidases.