Reconhecimento do desenvolvimento dos parasitas mixosporídeos e interações moleculares com o peixe hospedeiro, usando Kudoa dicentrarchi como modelo in vivo

The project presented in this proposal acknowledges that the spread of myxosporeans in fish farms is one of aquaculture’s biggest challenges. Myxosporean infections cause production inefficiencies, poor fish welfare, and significant economic losses, with the occurrence of outbreaks being an increasing concern under expanding aquaculture and global climate change [2, 5-10]. Gaining insight on the fish immune response, parasite development, evasion and immunomodulation throughout the infection is critical for the rational design of efficient prophylactic and therapeutic strategies against myxosporeans. To do this, the research plan outlined in this proposal aims to attain a better understanding of myxosporean-fish interactions, in order to investigate the fish immune response and molecular crosstalk taking place during distinct steps of infection. Several objectives will be pursued, including (1) the establishment and maintenance of a myxosporean in vivo model; (2) recognition of the site of parasite entry, and subsequent routes of migration, proliferation, and development within the fish; and (3) analysis of the parasite and host gene expression at selected infection time points. (1) The establishment of Kudoa dicentrarchi as a novel myxosporean in vivo model constitutes an ambitious objective, given known difficulties associated with maintaining these parasites under laboratory conditions [4, 15]. However, the team extensive expertise with this species, and previous success in maintaining both its hosts in controlled laboratory systems foresees the successful achievement of this objective, which will constitute a valuable advance to myxosporean research. Taking advantage of the access to a controlled source of parasites, another early-stage objective will be the de novo assembly of the K. dicentrarchi genome. Per se, this will constitute an important outcome given the paucity of myxosporean genomic datasets available, further allowing the reliable analysis of the parasite transcriptome. (2) Resorting to controlled fish experimental infections, the team will then endeavor to study the route of parasite entry, migration, and proliferation within the fish, characterizing different developmental stages and determining the time required for their occurrence. Myxosporean migration routes are mostly unknown [14], so this objective will increase knowledge of myxosporean-fish interactions, laying the foundation for the development of new prophylactic and therapeutic strategies for aquaculture. (3) Based on the data acquired, the next objective will be to study the immune response of D. labrax at selected infection time points and obtain novel transcriptomic datasets allowing a comprehensive analysis of both parasite and host gene expression profiles throughout the infection. This is a novel and promising approach as both parasite infection strategies and the host response will be analyzed simultaneously to understand how the fish immunity is modulated by changes in the parasite transcriptome and vice versa. Ultimately, the information acquired will provide an innovative and holistic overview of myxosporean infection, allowing for the identification of vaccine targets, infection biomarkers and drug targets. Such knowledge will allow the development and implementation of more efficient measures promoting the sustainability and economic growth of the aquaculture sector.