Molecular characterization of a DyP-type peroxidase from the human parasitic cestode Echinococcus multilocularis

The lethal zoonosis alveolar echinococcosis is caused by the metacestode larval stage of the tapeworm Echinococcus multilocularis. During the chronic phase of the disease, metacestode tissue is growing infiltratively into liver tissue and provokes an immunes response of the host. Mechanisms of parasite defence against reactive oxygen species (ROS), which are produced during parasite growth and host immune responses, are incompletely understood so far. We herein describe the characterization of an Echinococcus Dyp (dye decolorizing) - type peroxidase, EmDyp, family members of which are typically expressed by bacteria and fungi. EmDyp showed significant homologies to bacterial and fungal Dyp peroxidases and recombinantly expressed EmDyp displayed profound enzymatic activity towards different substrates such as 3,3-diaminobenzidine or luminol. Furthermore, although structurally not being related to classical catalases, EmDyp showed catalase activity in respective activity gels. In situ hybridization experiments showed expression of the EmDyp expressing gene, emdyp, in the germinal layer of the metacestode as well as in the posterior region of the protoscolex, both in differentiated and in germinative (stem) cells of the parasite. Interestingly, RT-qPCR experiments demonstrated that emdyp expression is induced in the metacestode upon growth under aerobic conditions. Particularly high expression of emdyp was observed under in vivo growth conditions in jirds within the liver. These data indicate a role of EmDyp in the defence of the metacestode against host- and/or parasite-derived ROS during chronic alveolar echinococcosis. Since Dyp-type peroxidases are not encoded on the genomes of mammalian hosts for E. multilocularis, EmDyp might be used as a target molecule for developing novel therapeutics against the parasite.