As an economically important marine fish, the large yellow croaker Larimichthys crocea suffered from marine white spot disease caused by the ectoparasite Cryptocaryon irritans in recent years. This disease not only could result in physiological damage, but also lead to secondary bacterial invasion. Reports indicated some AMPs (antimicrobial peptides) were of antiparasitic activity to C. irritans. Hepcidin-like (Lc-HepL) was one of the significant differential expression genes excavated from the transcriptome following a challenge with C. irritans. In this study, we characterized this AMP’s bioactivity based on the levels of mRNA and protein. After challenged by C. irritans, qRT-PCR showed Lc-HepL was significantly upregulated in six tissues, including gill, muscle, liver, head kidney and spleen during theront infection, trophont falling off, and secondary bacterial invasion stages, which implicated a role Lc-HepL played in the immune defense against C. irritans and secondary bacterial infection. Recombinant Lc-HepL (rLc-HepL) was induced and purified successfully. rLc-HepL exhibited antibacterial activity to certain bacteria in a dose- and time-dependent manners. Anti-C. irritans activity was explored for the first time and found it could cause the theronts membrane rupture and contents leakage. These results provided the first evidence that Lc-HepL had strong antiparasitic activity against marine fish ectoparasites C. irritans theronts. Together, data indicated that Lc-HepL might be an important component in the innate immune system against C. irritans and has the potential to be employed in future drug development.

作为经济上重要的海水鱼，大型黄花鱼Larimichthys crocea近年来遭受了由外寄生虫Cryptocaryon irritans引起的海洋白斑病。这种疾病不仅会导致生理损伤，还会导致继发性细菌入侵。报告指出一些AMPS（抗菌肽）是抗寄生虫活性对C. irritans。Hepcidin-like（Lc-HepL）是在用C. irritans攻击后从转录组中挖掘出的重要差异表达基因之一。在这项研究中，我们基于mRNA和蛋白质的水平来表征AMP的生物活性。在受到C. irritans的挑战后qRT-PCR显示，Lc-HepL在6种组织中显着上调，包括the，肌肉，肝脏，头部肾脏和脾脏，这些组织在继发感染，Trophont脱落和继发性细菌入侵阶段均参与其中，这暗示了Lc-HepL在肝细胞感染中的作用。免疫抵抗弧菌和继发性细菌感染。成功诱导并纯化了重组Lc-HepL（rLc-HepL）。rLc-HepL以剂量和时间依赖性方式表现出对某些细菌的抗菌活性。抗C. irritans首次对活性进行了探索，发现其可能导致火膜破裂和内容物泄漏。这些结果提供了第一个证据，表明Lc-HepL对海水鱼类的体外寄生虫C. irritans theronts具有很强的抗寄生虫活性。总之，数据表明，LC-HEPL可能是针对先天免疫系统的重要组成部分C. irritans，并在未来的药物研发中采用的潜力。