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Vaccination of rainbow trout against Yersiniosis confers a high degree of protection to the fish (Raida et al. 2011). On the other hand, vaccination could alter metabolitic reactions in organisms. Therefore, exploring the effects of vaccination against Y. ruckeri on health condition of trout in general, and oxidative stress biomarkers and biochemical alterations in different tissues specifically, would be valuable. This prompted us to investigate theeffects of vaccination against Y. ruckeri on muscle function, and the oxidative mechanism underlying those effects, by detecting relevant lipid peroxidation (2-thiobarbituric acid reactive substances, TBARS) and protein oxidation biomarkers (aldehydic derivatives and ketonic derivatives) as well as biochemical alterations (aminotransferases and lactate dehydrogenase activity, lactate and pyruvate levels) in rainbow trout Oncorhynchus mykiss following Y. ruckeri vaccination at first month after oral immunization. Concentrated vaccine with inactivated by formalin Y. ruckeri strains was enclosed by fish feed, and was administered three times every other day. Rainbow trout from each group were euthanized 30 days after the immunization, and then muscle tissue were sampled for analysis. The TBARS level in the muscle tissue of vaccinated group was at same level compared to unhandled group. The ketonic derivatives of oxidatively modified proteins in the trout following Y. ruckeri vaccination at first month after immunization were significantly increased compared to the level in the controls, while the aldehydic derivatives of oxidatively modified proteins were non-significantly increased. Pyruvate level was increased by 47% (p = 0.013) in vaccinated trout compared to values of untreated fish. Lactate level, aminotransferases and lactate dehydrogenase activities were non-significantly altered in vaccinated trout. Our results suggest that vaccination could promote the activation of the gluconeogenic substrate-providing enzymes, as well as substrates for aerobic metabolism that might in turn contribute to increase of oxidatively modified proteins. The oxidative stress biomarkers, i.e. content of oxidative protein damage, as well as biochemical enzymes and substrates were sensitive to vaccination of trout against Y. ruckeri and may potentially be used as biomarkers in evaluating vaccine toxicity in rainbow trout. From a practical point of view, the results may be useful in relation to studies of infections and the development, administration and uptake of new vaccines applicable for large amounts of fish.
Key words: yersiniosis, rainbow trout (Oncorhynchus mykiss), lipid peroxidation, oxidatively modified proteins, aminotransferases, lactate dehydrogenase, lactate, pyruvate