title: Identification and analysis of the immune effects of CpG motifs that protect Japanese flounder (Paralichthys olivaceus) against bacterial infection.
abstract: CpG-containing oligodeoxynucleotides (ODNs) are known to be immunostimulatory in vertebrate systems and can activate both innate and adaptive immune responses. In this report, we described the selection, identification, and analysis of CpG motifs with immunoprotective effects in Japanese flounder. Sixteen CpG ODNs were synthesized and examined for the ability to inhibit bacterial dissemination in Japanese flounder blood. Four ODNs with the strongest inhibitory effects were selected and mixed to form ODNs 4M. In addition, a plasmid, pCN6, was constructed that contains the sequences of the four selected ODNs. When administered into Japanese flounder via intraperitoneal injection, both ODNs 4M and pCN6 could, in dose and time dependent manners, afford short-term protection against the infections of two different bacterial pathogens. Immunological analyses showed that ODNs 4M and, especially, pCN6 activated head kidney macrophages and enhanced serum bactericidal activity via probably the alternative pathway of complement activation. When used as a DNA vaccine to immunize Japanese flounder, pCN6 conferred apparent protections (42.9% and 52.6%, respectively, in terms of relative percent survival) against the challenges of two different fish pathogens at 4-week post-vaccination. Transcriptional analysis showed that vaccination with pCN6 upregulated the expression of the genes encoding NKEF, MHC IIalpha, IL-1beta, Mx, and MHC Ialpha. These results demonstrate that ODNs 4M and pCN6 are immunostimulatory in Japanese flounder and can induce short- and long-term nonspecific protections against bacterial infections.
authors.affiliation: Institute of Oceanology, Chinese Academy of Sciences, 7 Nanhai Road, Qingdao 266071, PR China.
authors.forename: Chun-sheng
authors.initials: CS
authors.lastname: Liu
authors.forename: Yun
authors.initials: Y
authors.lastname: Sun
authors.forename: Yong-hua
authors.initials: YH
authors.lastname: Hu
authors.forename: Li
authors.initials: L
authors.lastname: Sun
mesh_terms: D000276:Adjuvants, Immunologic / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D005393:Fish Diseases / Q000276:immunology* / Q000517:prevention & control; D005432:Flounder / Q000276:immunology*; D005786:Gene Expression Regulation / Q000187:drug effects*; D016905:Gram-Negative Bacterial Infections / Q000276:immunology / Q000517:prevention & control / Q000662:veterinary*; D007113:Immunity, Innate / Q000187:drug effects; D008264:Macrophages / Q000187:drug effects; D009838:Oligodeoxyribonucleotides; D019444:Vaccines, DNA / Q000276:immunology
chemical_list: D000276:Adjuvants, Immunologic; D000900:Anti-Bacterial Agents; C408982:CPG-oligonucleotide; D009838:Oligodeoxyribonucleotides; D019444:Vaccines, DNA