title: Chicken-type lysozyme in channel catfish: expression analysis, lysozyme activity, and efficacy as immunostimulant against Aeromonas hydrophila infection.
abstract: To understand whether chicken-type lysozyme (Lys-c) in channel catfish was induced by infection of Aeromonas hydrophila, the transcriptional levels of Lys-c in skin, gut, liver, spleen, posterior kidney, and blood cells in healthy channel catfish was compared to that in channel catfish infected with A. hydrophila by bath immersion. Quantitative PCR revealed that the transcription levels of Lys-c in infected catfish were significantly (P < 0.05) induced in all five tissues tested as well as in blood cells. Recombinant CC-Lys-c produced in Escherichia coli expression system (R-CC-Lys-c) exhibited significant (P < 0.05) lytic activity to Gram-positive Micrococcus lysodeikticus and Gram-negative A. hydrophila. When pcDNA3.2-vectored recombinant channel catfish lysozyme-c (pcDNA-Lys-c) was transfected in channel catfish gill cells G1B, the over-expression of pcDNA-Lys-c offered significant (P < 0.05) protection to G1B against A. hydrophila infection. When channel catfish were intraperitoneally injected with QCDCR adjuvant formulated pcDNA-Lys-c and challenged with a highly virulent A. hydrophila strain AL-09-71 at 1-, 2-, 14-, and 28-days post treatment, pcDNA-Lys-c offered 75%, 100%, 60%, and 77% protection to channel catfish, respectively. Macrophages of fish treated with pcDNA-Lys-c produced significantly (P < 0.05) higher amounts of reactive oxygen species and nitric oxide than that of fish treated with pcDNA vector alone. Taken together, our results suggest that pcDNA-Lys-c could be used as a novel immunostimulant to protect channel catfish against A. hydrophila infection.
authors.affiliation: Aquatic Animal Health Research Unit, USDA-ARS, 990 Wire Road, Auburn, AL 36832, USA. Julia.Pridgeon@ars.usda.gov
authors.forename: Julia W
authors.initials: JW
authors.lastname: Pridgeon
authors.forename: Phillip H
authors.initials: PH
authors.lastname: Klesius
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Dominowski
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Yancey
authors.forename: Michele S
authors.initials: MS
authors.lastname: Kievit
mesh_terms: D016980:Aeromonas hydrophila; D000818:Animals; D005393:Fish Diseases / Q000276:immunology / Q000382:microbiology*; D029941:Fish Proteins / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation / Q000276:immunology*; D016905:Gram-Negative Bacterial Infections / Q000276:immunology / Q000382:microbiology / Q000662:veterinary*; D007059:Ictaluridae; D009113:Muramidase / Q000378:metabolism*; D009569:Nitric Oxide; D010802:Phylogeny; D017382:Reactive Oxygen Species
chemical_list: D029941:Fish Proteins; D017382:Reactive Oxygen Species; D009569:Nitric Oxide; D009113:Muramidase
keywords: Aeromonas hydrophila; Channel catfish; Immunostimulant; Lysozyme-c