ARS | Publication request: Expression profiles of seven channel catfish antimicrobial peptides in response to Edwardsiella ictaluri infection

Submitted to: Journal of Fish Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 27, 2011
Publication Date: February 10, 2012
Repository URL: http://hdl.handle.net/10113/55455
Citation: Wei Pridgeon, Y., Mu, X., Klesius, P.H. 2012. Expression profiles of seven channel catfish antimicrobial peptides in response to Edwardsiella ictaluri infection. Journal of Fish Diseases. 35:227-237.

Interpretive Summary: Using real time PCR technique, the relative transcriptional levels of seven channel catfish antimicrobial peptides in response to acute infection of bacterium Edwardsiella ictaluri were determined. At 2-h post infection, no antimicrobial peptide gene was significantly upregulated. At 4-, 6-, and 12- post infection, hepcidin antimicrobial peptide was the only one that was significantly upregulated. At 24- and 48-h post injection, three antimicrobial peptide genes were significantly upregulated. Among all the AMPs that were significantly upregulated at different time points, hepcidin at 4-, 6-, and 12-h post infection was induced the highest. The upregulation of hepcidin induced by E. ictaluri infection was dose-dependent. In vitro growth studies revealed that the presence of synthetic hepcidin peptide at concentration of 80 uM or higher significantly inhibited the growth of E. ictaluri. Taken together, our results suggest that hepcidin plays an essential role at the early infection stage to protect channel catfish from E. ictaluri infection.

Technical Abstract: Using quantitative PCR technique, the relative transcriptional levels of seven channel catfish antimicrobial peptide (AMP) genes [NK-lysin type 1, NK-lysin type 2, NK-lysin type 3, bactericidal permeability-increasing protein (BPI), cathepsin D, hepcidin, and liver-expressed antimicrobial peptide 2 (LEAP2)] in response to acute infection of Edwardsiella ictaluri were determined. At 2-h post infection, no AMP gene was significantly upregulated. At 4-, 6-, and 12- post infection, hepcidin was the only one that was significantly (P < 0.05) upregulated (132 +/- 44, 152 +/- 36, 92 +/- 14 fold, respectively). At 24-h post injection, three AMP (hepcidin, NK-lysin type 3, and cathepsin D) were significantly (P<0.05) upregulated. At 48-h post injection, three AMP (NK-lysin type 1, NK-lysin type 3 and BPI) were significantly (P<0.05) upregulated. Among all the AMPs that were significantly upregulated at different time points, hepcidin at 4-, 6-, and 12-h post infection was induced the highest. The upregulation of hepcidin induced by E. ictaluri infection was dose-dependent. In vitro growth studies revealed that the presence of synthetic hepcidin peptide at concentration of 80 uM or higher significantly inhibited the growth of E. ictaluri. Taken together, our results suggest that hepcidin plays an essential role at the early infection stage to protect channel catfish from E. ictaluri infection.