title: CpG-ODN increases resistance of olive flounder (Paralichthys olivaceus) against Philasterides dicentrarchi (Ciliophora: Scuticociliatia) infection.
abstract: 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.
authors.affiliation: Department of Aquatic Life Medicine, Pukyong National University, Namgu, Busan, South Korea.
authors.forename: Eun Hye
authors.initials: EH
authors.lastname: Lee
authors.forename: Ki Hong
authors.initials: KH
authors.lastname: Kim
mesh_terms: 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
chemical_list: D000276:Adjuvants, Immunologic; D009838:Oligodeoxyribonucleotides