Oligodeoxynucleotides CpGs increase silver catfish (Rhamdia quelen) resistance to Aeromonas hydrophila challenge

Immune modulation stands up as a strategic management procedures that might overcome the challenges of water-borne pathogens. Synthetic oligodeoxynucleotides (ODNs) containing cytidine-phosphate-guanosine (CpG) motifs are known to activate vertebrate innate immune cells and have been evaluated in several fish species but, to our knowledge, not yet in silver catfish. In this study we analyzed the effect of selected ODN CpGs on their ability to enhance the resistance of silver catfish to a lethal infection with Aeromonas hydrophila. We found that silver catfish pretreated with some ODN CpGs had lower bacterial counts in the blood and the percentile of bacteremic fish was lower compared to control fish. In addition, the survival rate of ODN CpG-treated fish was higher following challenge with A. hydrophila. The effect of ODN CpG 1668, which provided higher protection against challenging bacteria, was dose and time dependent. Our results demonstrate that ODN CpG can induce disease resistance in silver catfish.