Identification And Analysis Of The Immune Effects Of CpG Motifs That Protect Turbot And Japanese Flounder Against Bacterial Infection

Resently, oligodeoxynucleotides (ODNs) containing unmethylated CpG motifs in certain contexts are known to be immunostimulatory in vertebrate systems.In this study, a turbot-effective CpG ODN, ODN 205, was identified. When administered into turbot via intraperitoneal (i.p.) injection, both ODN 205 and pCN5 could protect against lethal bacterial(such as E. tarda TX1 and V. harveyi T4) challenge. Immunological analyses showed that ODN 205 and pCN5 induced immune responses to turbot .To examine whether ODN 205 and pCN5 had any effect on specific immunity, ODN 205 and pCN5 were co-administered into turbot with a Vibrio harveyi subunit vaccine, DegQ. The results showed that pCN5, but not ODN 205, significantly increased the immunoprotective efficacy of DegQ and enhanced the production of specific serum antibodies in the vaccinated fish.Further, SixteenCpG ODNs were synthesized and examined for the ability to inhibit bacterial dissemination in Japanese flounder. Four ODNs with the strongest inhibitory effects were selected. In addition, a plasmid, pCN6, was constructed from pCN3 that contains the sequences of the four selected ODNs.When used as a DNA vaccine to immunize Japanese flounder, pCN6 conferred apparent protections against the challenges of two different fish pathogens (Edwardsiella tarda,Aeromonas hydrophila)at 4-week post-vaccination.