National Key Laboratory of Agricultural Microbiology, College of Fisheries, Huazhong Agricultural University, Wuhan, 430070, Hubei, China; Hubei Engineering Technology Research Center for Aquatic Animal Diseases Control and Prevention, Wuhan, 430070, Hubei, China.
College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, 430070, Hubei, China.
Fish Shellfish Immunol. 2024 Nov;154:109875. doi: 10.1016/j.fsi.2024.109875. Epub 2024 Sep 3.
Largemouth bass virus (LMBV) is a highly pathogenic pathogen that often causes high mortality of affected largemouth bass and significant financial losses. Type I interferon as an effective and broad spectrum tool has been successfully used for therapeutic or prophylactic treatment some viral infections. However, the implementation of immunotherapies based on interferon administration to combat LMBV infections has not been reported. And Lactic Acid Bacteria (LAB) are a powerful vehicle for expressing cytokines or immunostimulant peptides at the gastrointestinal level after oral administration. In this study, Lactococcus lactis (L. lactis) expression system with lactose as a screening marker was utilized to express the Micropterus salmoides interferon a3 (IFNa3) protein and orally administered to largemouth bass. The genetically engineered strain pNZ8149-Usp45-IFNa3-6His/L. lactis NZ3900 was successfully constructed, and its potential to elicit immune protection response by oral administration was evaluated. After orally administration, the recombinant L. lactis was detected in guts of experimental fish and remained detectable for 72 h. Additionally, IFNa3 was able to enhance the test fish's immune response, as determined by the relatively increased mRNA relative expression of immune-related genes in the liver, spleen, and kidney tissues, including IFN-γ, TNF-α, IL-1β, IL-8, IgM and IgT. Following LMBV challenge, the experiment group of pNZ8149-Usp45-IFNa3-6His/L. lactis NZ3900 exhibited a 70 % survival rate, while survival rate were 15 % in the PBS control group, 45 % in the pNZ8149/L. lactis NZ3900 group. Furthermore, the viral load in the surviving fish was significantly lower than that of the control groups. These findings suggest that oral administration of recombinant L. lactis producing IFNa3 induces largemouth bass immune responses at a systemic level to effective prevent and combat of LMBV infection.
大口黑鲈病毒（LMBV）是一种高致病性病原体，常导致受感染的大口黑鲈高死亡率和重大经济损失。I 型干扰素作为一种有效且广谱的工具，已成功用于治疗或预防某些病毒感染。然而，基于干扰素给药的免疫疗法在对抗 LMBV 感染方面尚未有报道。并且，乳酸菌（LAB）是一种强大的载体，可在口服后在胃肠道水平表达细胞因子或免疫刺激肽。在这项研究中，利用乳糖作为筛选标记的乳球菌（L. lactis）表达系统表达了斑点叉尾鮰干扰素 a3（IFNa3）蛋白，并口服施用于大口黑鲈。成功构建了携带乳糖筛选标记的 pNZ8149-Usp45-IFNa3-6His/L. lactis NZ3900 基因工程菌，并评估了其经口服给药引发免疫保护应答的潜力。口服给药后，重组 L. lactis 可在实验鱼的肠道中检测到，并可在 72 小时内检测到。此外，IFNa3 能够增强试验鱼的免疫反应，这可以通过肝脏、脾脏和肾脏组织中免疫相关基因的相对 mRNA 相对表达来确定，包括 IFN-γ、TNF-α、IL-1β、IL-8、IgM 和 IgT。在受到 LMBV 攻击后，pNZ8149-Usp45-IFNa3-6His/L. lactis NZ3900 实验组的存活率为 70%，而 PBS 对照组的存活率为 15%，pNZ8149/L. lactis NZ3900 组的存活率为 45%。此外，幸存鱼体内的病毒载量明显低于对照组。这些发现表明，口服给予表达 IFNa3 的重组 L. lactis 可诱导大口黑鲈全身免疫反应，从而有效预防和对抗 LMBV 感染。
