| Summary: | Trabajo presentado en 3rd International Conference on Fish and Shellfish Immunology (ISFSI), celebrado en Gran Canaria (España), del 16 al 20 de junio de 2019 Philasterides dicentrarchi is a marine scuticociliate that causes scuticociliatosis in farmed fish worldwide and is currently considered one of the most important pathogens of cultured flatfish. Although there is abundant information about the infections caused by P. dicentrarchi in fish and about how the ciliates and fish immune cells interact in vitro, little is known about the interaction between this ciliate and the fish immune system in vivo. In the present study, turbot (Scophthalmus maximus) were exposed twice to the parasite (on days 1 and 21). Immersion infection was performed by adding ciliates to tanks of seawater (18 ºC) to yield a final concentration of 4.5 x 104 ciliates/mL. Fish were exposed to the ciliates by immersion in the seawater for 20 min and were then transferred to tanks of clean seawater for 60 days. Control fish were immersed in seawater with no ciliates, and were subjected to the same conditions as the experimental fish. Four fish died of scuticociliatosis during the experiment. Fish (eight per group) were sampled on days 3, 7, 21 after the first exposure to P. dicentrarchi and on days 3, 7 and 40 after the second exposure. The presence of ciliates on the skin and gills was evaluated by qPCR. The IgM, IgT and IgD levels were measured in serum on days 3, 7 and 40 and in mucus on day 40 after the second exposure. Changes in gene expression of immunoglobulins, MHCII and other immune-related genes were determined by qPCR, in gills, skin, and spleen at all sampling times. There were no significant differences in serum IgM, IgD and IgT levels between experimental and control groups at any of the sampling times; however, there was a significant increase in mucus IgT levels 40 days after administration of the second exposure. The results of the qPCR analysis showed few changes of the immunoglobulin expression in the analyzed organs ...
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