The eel farming industry is highly susceptible to . Although various types of vaccines against have been investigated, there is limited research on decreasing the virulence of s through gene knockout and utilizing it as live attenuated vaccines (LAV). In this study, we aim to develop a LAV candidate against infection in American eels () using a ferric uptake regulator () gene mutant strain of (Δ mutant). After the eels were administrated with the Δ mutant at the dose of 4 × 10 cfu/g body weight, the phagocytic activity of the leucocytes, plasma IgM antibody titers, activity of lysozyme and Superoxide Dismutase (SOD) enzyme, and gene expression levels of 18 immune related proteins were detected to evaluate the protection effect of the LAV. Preliminary findings suggest that the LAV achieved over 60% relative percent survival (RPS) after the American eels were challenged by a wild-type strain of infection on 28 and 42 days post the immunization (dpi). The protection was mainly attributed to increased plasma IgM antibody titers, higher levels of lysozyme, enhanced activity of SOD and some regulated genes encoded immune related proteins. Together, the Δ mutant strain of , as a novel LAV vaccine, demonstrates promising protective effects against infection in American eels, thus presenting a potential candidate vaccine for fish farming.

中文翻译：

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Δfur突变体作为潜在的减毒活疫苗（LAV）候选者可保护美国鳗鱼（Anguilla rostrata）免受哈维氏弧菌感染

鳗鱼养殖业极易受到感染。尽管已经研究了各种类型的疫苗，但通过基因敲除降低s的毒力并将其用作减毒活疫苗（LAV）的研究有限。在这项研究中，我们的目标是使用（Δ突变体）的铁吸收调节（）基因突变株来开发一种抗美国鳗鱼（）感染的LAV候选药物。鳗鱼以4×10 cfu/g体重的剂量施用Δ突变体后，观察白细胞吞噬活性、血浆IgM抗体滴度、溶菌酶和超氧化物歧化酶（SOD）酶活性以及检测18种免疫相关蛋白，评价LAV的保护效果。初步研究结果表明，美国鳗鱼在免疫后 28 天和 42 天 (dpi) 受到野生型感染菌株的攻击后，LAV 的相对存活率 (RPS) 超过 60%。这种保护作用主要归因于血浆IgM抗体滴度增加、溶菌酶水平升高、SOD活性增强以及一些编码免疫相关蛋白的调节基因。总之，作为一种新型 LAV 疫苗，Δ 突变株在美国鳗鱼中表现出有希望的针对感染的保护作用，从而为养鱼业提供了一种潜在的候选疫苗。