Identification of concealed antigens in fish ectoparasites.

The present project application aims at identifying novel concealed antigens in monogenean fish ectoparasites. Identified antigens will be important candidates for inclusion in future specific vaccines. Efforts will be focused on detecting parasite substa nces that interfere with, or inhibit, the activity of the complement system of the fish host. The complement system is an important part of the innate immune system, with direct killing effects, but also with ability to augment the effect of specific anti bodies binding to pathogen structures. In monogeneans, the activity of complement is lethal when applied to the thick-walled body surface, but not after ingestion via the feed. This apparent paradox suggests that the monogenean parasites are dependent on inhibition of complement in the gut via specific inhibitors, as it has been shown for ectoparasites on terrestrial animals. Monogenean ectoparasites constitute a severe threat to several wild and cultured fish species. In aquaculture, control with parasit e infections can be accomplished by use of chemicals, but this practice is accompanied by several, and increasing, problems. Hence, the development and use of specific vaccines will be a highly valuable contribution to a sustainable aquaculture. Developm ent of ectoparasite vaccines in general, has proven to be a formidable challenge to science, with identification of truly protective antigens as the single-most difficult task. The present project responds to this challenge by using modern phage display t echnology to identify parasite substances that interact directly with host immune factors.