Departamento de Biologia, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre s/n, Ed. FC4, 4169-007, Porto, Portugal; CIIMAR - Centro Interdisciplinar de Investigação Marinha e Ambiental, Terminal de Cruzeiros do Porto de Leixões, Av. General Norton de Matos s/n, 4450-208, Matosinhos, Portugal; CITAB - Centro de Investigação e Tecnologias Agroambientais e Biológicas, Universidade de Trás-os-Montes e Alto Douro, Quinta de Prados, 5000-801, Vila Real, Portugal; CECAV - Centro de Ciência Animal e Veterinária, Universidade de Trás-os-Montes e Alto Douro, P.O. Box 1013, 5001-801, Vila Real, Portugal.
Departamento de Biologia, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre s/n, Ed. FC4, 4169-007, Porto, Portugal.
Fish Shellfish Immunol. 2022 Feb;121:285-294. doi: 10.1016/j.fsi.2022.01.002. Epub 2022 Jan 8.
Stimulation of the fish immune system using immunostimulants is an environmentally friendly strategy to minimize bacterial outbreaks in aquaculture. Different biological and synthetic immunostimulants can enhance non-specific innate immune responses by directly activating immune cells. An example are Bacillus spp., known for their immunostimulatory effects, although the exact mechanisms by which Bacillus spp. offer protection against diseases remains to be elucidated. Furthermore, most studies have focused on Bacillus spp. cells, while the immunostimulant effect of their extracellular metabolome, known to harbour biologically important metabolites, including antimicrobial molecules, has been scarcely evaluated. Here, we evaluated the in vitro immune-modulatory properties of extracellular extracts of three Bacillus spp. strains (B. subtilis FI314, B. vezelensis FI436 and B. pumilus FI464), previously isolated from fish-guts and characterized for their in vitro and in vivo antimicrobial activity against a wide range of fish pathogens. Bacillus spp. extracellular extracts did not affect immune cells viability, but remarkably increased pathogens' phagocytosis when seabream head-kidney leukocytes were challenged with Vibrio anguillarum and Edwardsiella tarda. All extracts significantly increased the engulfment of bacterial pathogens 1 h post-infection. Cells stimulated with the extracellular extracts showed an up-regulation of the expression of immune-relevant genes associated with inflammation, including IL-1β, IL-6, and COX-2. In cells challenged with E. tarda, FI314 extracellular extract significantly increased the expression of IL-1β, IL-6, and COX-2, while FI436 and FI464 significantly increased IL-6 expression. The results of this study revealed that the extracellular molecules from Bacillus spp. fish isolates improved the in vitro response of gilthead seabream immune cells and are thus promising candidates to act as immunostimulants, helping fish fight diseases.
使用免疫刺激剂刺激鱼类的免疫系统是一种在水产养殖中最小化细菌爆发的环保策略。不同的生物和合成免疫刺激剂可以通过直接激活免疫细胞来增强非特异性先天免疫反应。芽孢杆菌属就是一个例子，它们以其免疫刺激作用而闻名，尽管芽孢杆菌属提供疾病保护的确切机制仍有待阐明。此外，大多数研究都集中在芽孢杆菌属细胞上，而其细胞外代谢组的免疫刺激作用，其中含有包括抗菌分子在内的具有重要生物学意义的代谢物，却很少被评估。在这里，我们评估了三种芽孢杆菌属（枯草芽孢杆菌 FI314、解淀粉芽孢杆菌 FI436 和地衣芽孢杆菌 FI464）的胞外提取物的体外免疫调节特性，这些菌株先前从鱼类肠道中分离出来，并因其对广泛的鱼类病原体的体外和体内抗菌活性而得到了表征。芽孢杆菌属胞外提取物不影响免疫细胞的活力，但当鲈鱼头肾白细胞受到鳗弧菌和迟缓爱德华氏菌的挑战时，它们显著增加了病原体的吞噬作用。所有提取物在感染后 1 小时显著增加了细菌病原体的吞噬作用。用胞外提取物刺激的细胞显示与炎症相关的免疫相关基因的表达上调，包括 IL-1β、IL-6 和 COX-2。在受到 E. tarda 挑战的细胞中，FI314 胞外提取物显著增加了 IL-1β、IL-6 和 COX-2 的表达，而 FI436 和 FI464 则显著增加了 IL-6 的表达。这项研究的结果表明，来自鱼类分离株的芽孢杆菌属胞外分子改善了鲈鱼免疫细胞的体外反应，因此是作为免疫刺激剂的有前途的候选物，可以帮助鱼类抵抗疾病。
