Identification of duck liver-expressed antimicrobial peptide 2 (LEAP-2) and characterization of its bactericidal activity

Authors: HONG, YEOJIN - Chung-Ang University; TRUONG, ANH DUC - Chung-Ang University; LEE, JANGGEUN - Chung-Ang University; LEE, KYUNGBAEK - Chung-Ang University; KIM, GEUN-BAE - Chung-Ang University; HEO, KANG-NYEONG - Rural Development Administration - Korea; Lillehoj, Hyun; HONG, YEONG HO - Chung-Ang University

Submitted to: Asian-Australasian Journal of Animal Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/26/2018
Publication Date: 10/29/2018
Citation: Hong, Y., Truong, A., Lee, J., Lee, K., Kim, G., Heo, K., Lillehoj, H.S., Hong, Y. 2018. Identification of duck liver-expressed antimicrobial peptide 2 (LEAP-2) and characterization of its bactericidal activity. Asian-Australasian Journal of Animal Sciences. https://doi.org/10.5713/ajas.18.0571.
DOI: https://doi.org/10.5713/ajas.18.0571

Interpretive Summary: With increasing concerns about food and environmental safety with respect to the emergence of antibiotic resistance in pathogens and the increasing presence of antibiotic residues in meat products in the last few decades, novel strategies for alternatives to antibiotics to reduce the usage of antibiotic growth promoters (AGPs) in poultry production are critically needed. One of novel approaches involves antimicrobial peptides (AMPs) which play crucial function in innate host protection against many pathogens. In this paper, ARS scientists collaborated with Korean scientists to characterize chicken liver-expressed antimicrobial peptide 2 (LEAP-2) which was first reported in humans in 2003. In poultry, LEAP-2 sequences have been characterized several years ago but its function was not studied. In this paper, the authors report anti-microbial activity of recombinant duck LEAP-2 protein against Gram-positive and Gram-negative bacteria. Furthermore, importance of disulfide bonds in anti-microbial activity has been shown to be associated with its killing effect by disrupting the bacterial cell envelope. This finding suggest that duck LEAP-2 can be used as antibiotic alternative for effective treatment of some bacterial infections.

Technical Abstract: Objective: This study was conducted to identify duck liver-expressed antimicrobial peptide 2 (LEAP-2) and demonstrate its antimicrobial activity against various pathogens. Methods: Tissue samples were collected from 6 -8-week-old Pekin duck (Anas platyrhynchos domesticus), total RNA was extracted and cDNA was synthesized. To confirm the duck LEAP-2 transcript expression levels, qRT-PCR was conducted. Two kinds of peptides (a linear peptide and a disulfide-type peptide) were synthesized to compare the antimicrobial activity. Then, antimicrobial activity assay and fluorescence microscopic analysis were conducted to demonstrate duck LEAP-2 bactericidal activity. Results: The duck LEAP-2 peptide sequence showed high identity with those of other avian species (>85%), as well as more than 55% of identity with mammalian sequences. LEAP-2 mRNA was highly expressed in the liver with duodenum next, and then followed by lung, spleen, bursa and jejunum and was the lowest in the muscle. Both of LEAP-2 peptides efficiently killed bacteria, although the disulfide-type LEAP-2 showed more powerful bactericidal activity. Also, Gram-positive bacteria was more susceptible to duck LEAP-2 than Gram-negative bacteria. Using microscopy, we confirmed that LEAP-2 peptides could kill bacteria by disrupting the bacterial cell envelope. Conclusion: Duck LEAP-2 showed its antimicrobial activity against both Gram-positive and Gram-negative bacteria. In particular, disulfide bonds were important for a powerful killing effect by disrupting the bacterial cell envelope. Therefore, duck LEAP-2 can be used for effective antibiotics alternatives.