CpG-ODN increases resistance of olive flounder (Paralichthys olivaceus) against Philasterides dicentrarchi (Ciliophora: Scuticociliatia) infection.
Unmethylated cytosine-phosphate-guanine (CpG) dinucleotides flanked by specific bases in bacterial DNA induce a favorable immune response by acting as danger signals to the host. Synthetic oligodeoxynucleotides containing CpG motifs (CpG-ODNs) also act like the unmethylated CpG oligonucleotides in bacterial DNA. In the present study, we investigated the effects of synthetic CpG-ODN on the protection of olive flounder (Paralichthys olivaceus) against infection by Philasterides dicentrarchi, a pathogen of scuticociliatosis, through two consecutive experiments (trial I and II). Fish were intraperitoneally (i.p.) injected with CpG-ODN 1668 or GpC-ODN 1720 at different doses (3 microg in trial I and 10 microg in trial II), and after one week the fish were i.p. challenged with P. dicentrarchi. In both trial I and II, fish injected with CpG-ODN 1668 showed significantly higher serum scuticocidal activity than fish injected with PBS alone, while the scuticocidal activity disappeared by heat-inactivation. This result suggests that CpG-ODN might activate an alternative pathway of complement of olive flounder, and complement-mediated killing might be an important innate immune factor in the resistance against P. dicentrarchi infection. Although the cumulative mortality was largely different between trials I and II, the relative survival rate of fish injected with a high dose of CpG-ODN 1668 was considerably higher than that of fish injected with a low dose of this ODN, while the relative survival rate was not different between fish injected with the high dose and low dose of GpC-ODN 1720. The results of the present study suggest that CpG-ODNs may be used as potential immunostimulants to lessen cultured fish loss caused by scuticociliates.
Lee
Eun Hye
EH
Department of Aquatic Life Medicine, Pukyong National University, Namgu, Busan, South Korea.
Kim
Ki Hong
KH
D000276:Adjuvants, Immunologic / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D016798:Ciliophora / Q000502:physiology; D016770:Ciliophora Infections / Q000276:immunology / Q000401:mortality / Q000517:prevention & control / Q000662:veterinary*; D018899:CpG Islands / Q000276:immunology*; D005393:Fish Diseases / Q000276:immunology / Q000469:parasitology / Q000517:prevention & control; D005432:Flounder / Q000276:immunology*; D007113:Immunity, Innate / Q000187:drug effects*; D009838:Oligodeoxyribonucleotides / Q000008:administration & dosage / Q000494:pharmacology*; D016019:Survival Analysis
D000276:Adjuvants, Immunologic; D009838:Oligodeoxyribonucleotides