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The aim of this study was to assess the effect of oral vaccination against Yersinia ruckeri based on oxidative stress biomarkers in different tissues of rainbow trout (Oncorhynchus mykiss Walbaum). Vaccine consisted of three Y. ruckeri strains (O1 serotype) that originated from rainbow trout cultured on the different farms, where fish exhibited clinical signs of enteric redmouth disease. Concentrated vaccine was incorporated in the fish food; treatment was delivers three times at one day intervals. One month after immunization, gills, hepatic and cardiac tissues were sampled. The vaccinated trout showed tissue-specific oxidative stress responses in the gills, liver, and heart. The gill tissue was the most sensitive to oxidative damage among the samples. Accumulation of oxidative stress biomarkers in the rainbow trout was tissue-specific with following accumulation: gills > heart > liver. These results suggest that the trout expressed tissue-specific oxidative stress mechanisms due to anti-Yersinia vaccine treatment. There were no statistically significant alterations in the activities of antioxidant defenses instead superoxide dismutase activity in the hepatic and cardiac tissue and glutathione peroxidase activity in the gills of vaccinated trout. Correlative analysis confirmed the role of catalase in the antioxidant defense in vaccinated trout. The oxidative stress biomarkers, i.e. content of oxidative modified proteins in the gills, and liver, and 2-thiobarbituric acid reactive substances level in the gills, and total antioxidant capacity in the liver, were sensitive to vaccination of trout against
Y. ruckeri and may potentially be used as biomarkers in evaluating vaccine toxicity in rainbow trout.