The aim of this study is to evaluate the effects of irradiated trophonts of Ichthyophthirius multifiliis and alginate/calcium phosphate nanoparticles on total sialic acid levels in immunized rainbow trout kidney, liver and spleen tissues. The 15 fish tissues of the treated and control groups were sampled at 30 days following the first immunization. Tissue samples were homogenized and centrifuged. The total sialic acid levels of the tissue samples were determined using a commercially available Quantitation Kit. Significant increases in kidney, spleen and liver TSA levels were determined in the treated groups in comparison to the controls. The immunosupportive effects of sialic acid were illustrated by the elevation in the amount of TSA in the kidneys, liver and spleen of the immunized fish. Also, the significant increase in the TSA levels in the rainbow trout treated with calcium phosphate nanoparticles could be attributed to the Ca-binding capacity of the glycerol side chain of the sialic acid. Finally, the results of this study showed that sialic acid may be a mediator in the development of long-circulating nanocarriers to advance the field of vaccine delivery in fish.

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