Artemia has been used extensively in aquaculture as fodder for larval fish, shrimp, and shellfish. Epinecidin-1, an
antimicrobial peptide, was isolated from grouper (Epinephelus coioides) in 2005. Epinecidin-1 has been previously reported to possess antimicrobial activity against several Gram-positive and Gram-negative bacterial species, including Staphylococcus
coagulase, Pseudomonas aeruginosa, Streptococcus pyogenes, and Vibrio vulnificus. In this study, we used electroporation to introduce plasmid
DNA encoding a
green fluorescent protein (EGFP)-epinecidin-1 fusion
protein under the control of the cytomegalovirus (CMV) promoter into decapsulated Artemia
cysts. Optimization of various properties (including
cyst weight (0.2 g), plasmid concentration (50 μg/100 μl), and pulse voltage (150 V), length (10 ms), and number (2)) resulted in a hatching rate of 41.15%, a transfection efficiency of 49.81%, and a fluorescence intensity (A.U.) of 47.46. The expression of EGFP-epinecidin-1 was first detected by quantitative RT-PCR at 120 h post-electroporation, and
protein was identified by Western blot at the same time. Furthermore, the EGFP-epinecidin-1
protein inhibited V. vulnificus (204) growth, as demonstrated by zone of inhibition studies. Zebrafish fed on transgenic Artemia expressing CMV-gfp-epi combined with commercial fodder were more resistant to
infection by V. vulnificus (204): survival rate was enhanced by over 70% at 7, 14, and 21 days post-
infection, and bacterial numbers in the liver and intestine were reduced. In addition, feeding of transgenic Artemia to zebrafish affected the immunomodulatory response to V. vulnificus (204)
infection; expression of immune-responsive genes, including
hepcidin and defbl2, was altered, as shown by qPCR. These findings suggest that feeding transgenic Artemia expressing CMV-gfp-epi to larval fish has antimicrobial effects, without the drawbacks of introducing drug residues or inducing bacterial drug resistance.