| Summary: | 碩士 === 國立屏東科技大學 === 動物疫苗科技研究所 === 101 === Antimicrobial peptides (AMPs) are cationic peptide widespread in living organisms and constitute an important component of innate immunity to microbial, fungi, virus and tumor infections. Since 1980s, more than 2000 different antimicrobial peptides had been isolated from mammals, amphibians, fish, insects, plants and bacterial species.Pleurocidin (Ple), a 25-residue peptides, is an α-helical cationic from the skin-secreted mucous of the winter flounder (Pleuronectes americanus). Ple shows potent antimicrobial activities against Gram-positive and -negative bacteria. However, naturally pleurocidin is highly susceptibe to degradation by proteases and exhibits a short half-life in target animals. The situation reduces its feasibility for farm and clinic use. Currently, some studies have demonstrated that the D-amino acid substitution stabilize, secondary structures, and membrane-activity of AMPs. In the present study, D-amino acid Ple (D-PLe) was synthesized to analyze its protease sensitivity and adjuvant effect. D-Ple showed not only its resistance to the degradation of trypsin and papain but also its antibacterial and low hemolytic effect. In the first animal experiment, each tilapia intraperitoneally (I.P.) received D-Ple (64 μg/fish) plus bovine serum albumin (BSA) showed higher sera responses against BSA. In the second animal experiment, results from ICR mice subcutaneously received either D-Ple (64 μg/mice) plus BSA ntigen revealed that D-Ple could induce not only high sera responses but also lymphocyte proliferation. In addition, INF-γ secreton was significantly observed in mice immunized with D-Ple plus BSA seven days after priming. IL-4 and IL-10 were then secreted fourteen days after priming. In conclusion, D-Ple can quickly elicit cellular immunity and then promot early humoral immune response. D-Ple displays the immunomodulating capacity and shows the potent adjuvant effect in fish and mice.
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