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Title: G-protein coupled receptor 18 (GPR18) in channel catfish: Expression analysis and efficacy as immunostimulant against Aeromonas hydrophila infection

Author
item Wei Pridgeon, Yuping
item Klesius, Phillip

Submitted to: Fish and Shellfish Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/9/2013
Publication Date: 9/6/2013
Publication URL: https://handle.nal.usda.gov/10113/58427
Citation: Wei Pridgeon, Y., Klesius, P.H. 2013. G-protein coupled receptor 18 (GPR18) in channel catfish: Expression analysis and efficacy as immunostimulant against Aeromonas hydrophila infection. Fish and Shellfish Immunology. 35:1070-1078.

Interpretive Summary: Molecular analysis revealed that the transcription levels of GPR18 in all tissues of infected catfish were significantly induced except in the intestine. When recombinant GPR18 was expressed in catfish gill cells G1B, the over-expression of GPR18 offered significant protection to G1B cells against Aeromonas hydrophila infection. When channel catfish were injected with adjuvanted recombinant GPR18 DNA and challenged with a highly virulent A. hydrophila strain at 1-, 2-, 14-, and 28- days post treatment, pcDNA-GPR18 offered 50%, 100%, 57%, and 55% protection to channel catfish, respectively. Macrophages of fish treated with pcDNA-GPR18 produced significantly higher amounts of reactive oxygen species and nitric oxide than that of fish treated with DNA vector alone. In addition, serum lysozyme activity of catfish injected with recombinant GPR18 DNA was significantly increased. Taken together, our results suggest that pcDNA-GPR18 could be used as a novel immunostimulant to provide immediate protection to channel catfish against A. hydrophila infection.

Technical Abstract: The objectives of this study were: 1) to determine the transcriptional profiles of G-protein coupled receptor 18 (GPR18) in channel catfish after infection with A. hydrophila compared to that in healthy catfish; 2) to determine whether over-expression of GPR18 in catfish gill cells will offer protection against infection of A. hydrophila; 3) to determine whether recombinant pcDNA-GPR18 could be used as an immunostimulant to protect channel catfish against A. hydrophila infection. Quantitative PCR revealed that the transcription levels of GPR18 in all tissues of infected catfish were significantly (P < 0.05) induced except in the intestine. When pcDNA3.2-vectored recombinant GPR18 was transfected in catfish gill cells G1B, the over-expression of pcDNA-GPR18 offered significant (P < 0.05) protection to G1B cells against A. hydrophila infection. When channel catfish were intraperitoneally injected with QCDCR adjuvant formulated pcDNA-GPR18 and challenged with a highly virulent A. hydrophila strain at 1-, 2-, 14-, and 28- days post treatment, pcDNA-GPR18 offered 50%, 100%, 57%, and 55% protection to channel catfish, respectively. Macrophages of fish treated with pcDNA-GPR18 produced significantly (P<0.05) higher amounts of reactive oxygen species and nitric oxide than that of fish treated with pcDNA vector alone. In addition, serum lysozyme activity of catfish injected with pcDNA-GPR18 was significantly (P<0.08) increased. Taken together, our results suggest that pcDNA-GPR18 could be used as a novel immunostimulant to provide immediate protection to channel catfish against A. hydrophila infection.