Characterization of pathological changes and immune-related gene expression in yellow drum (Nibea albiflora) in response to Pseudomonas plecoglossicida and poly I:C challenge

Abstract The yellow drum (Nibea albiflora; Na) constitutes an important seafood fish species that is subjected to intensive cage culture in China. The fish is susceptible to infection by bacteria and virtual pathogens, which results in considerable economic loss. In the present study, the pathogenic characteristics and immune response of the yellow drum were analyzed after Pseudomonas plecoglossicida or poly I:C challenge. Tissue sections revealed cell vacuolization in the liver and obvious macrophage infiltration in the spleen following P. plecoglossicida infection, whereas these tissues exhibited no significant lesions upon poly I:C challenge. Superoxide dismutases (SODs) and heat shock proteins (HSPs), which play important roles in the immune response of fish in defense against environmental threats or stresses, were further analyzed. The quantitative real time PCR (qPCR) analysis showed that mRNAs for intracellular copper/zinc-SOD (NaSOD1), manganese SOD (NaSOD2), extracellular copper/zinc-SOD (NaSOD3), HSP70, and HSP90 were expressed in 11 tested tissues including high levels in the liver, spleen, kidney, and gill; further significant increase was observed in the liver, spleen, and gill following P. plecoglossicida or poly I:C challenge. Moreover, the activities of total SOD and the contents of NaHSP70 and NaHSP90 in the liver were up-regulated after P. plecoglossicida or poly I:C challenge, which was generally similar to the fluctuations of mRNA expression in the tissue. The results showed that the dynamic changes in SODs and HSPs exhibited a similar tendency, which might indicate a coordinate action against P. plecoglossicida or poly I:C challenge. These findings will contribute towards better understanding of the biological process involved in defending against pathogenic bacteria and virtual challenge, as well as provide insight regarding the molecular mechanisms of the initial immune response in the yellow drum.