Research on immunotherapeutic agents has become a focus for the treatment of fish diseases. The ability of algae to produce secondary metabolites of potential interest as immunotherapeutics has been documented. The present research intended to assess antiviral and antibacterial activities of macro- and microalgae extracts against viral and bacterial pathogens and explore their immunomodulatory potential using zebrafish (Danio rerio) larvae as a model organism. The cytotoxicity and antiviral activity of eight methanolic and ethanolic extracts from two macroalgae (Fucus vesiculosus, Ulva rigida) and two microalgae (Nannochloropsis gaditana, Chlorella sp.) were analyzed in established fish cell lines. Six extracts were selected to evaluate antibacterial activity by disk diffusion and growth inhibition assays. The three most promising extracts were characterized in terms of fatty acid composition, incorporated at 1% into a plant-based diet, and evaluated their effect on zebrafish immune response and intestinal morphology in a short-term feeding trial. All extracts exhibited in vitro antiviral activity against viral hemorrhagic septicemia and/or infectious pancreatic necrosis viruses. Methanolic extracts from F. vesiculosus and U. rigida were richer in saturated fatty acids and exhibited in vitro antibacterial action against several bacteria. Most promising results were obtained in vivo with F. vesiculosus methanol extract, which exerted an anti-inflammatory action when incorporated alone into diets and induced pro-inflammatory cytokine expression, when combined with the other extracts. Moreover, dietary inclusion of the extracts improved intestinal morphology. In summary, the results obtained in this study support the potential of algae as natural sources of bioactive compounds for the aquaculture industry.

免疫治疗剂的研究已成为鱼病治疗的热点。藻类产生作为免疫治疗剂具有潜在意义的次生代谢物的能力已被记录。本研究旨在评估大型和微藻提取物对病毒和细菌病原体的抗病毒和抗菌活性，并使用斑马鱼（ Danio rerio ）幼虫作为模式生物探索其免疫调节潜力。在已建立的鱼细胞系中分析了两种大型藻类（墨角藻、石莼）和两种微藻（微绿球藻、小球藻属）的八种甲醇和乙醇提取物的细胞毒性和抗病毒活性。选择六种提取物通过纸片扩散和生长抑制测定来评估抗菌活性。对三种最有前途的提取物的脂肪酸组成进行了表征，将其添加到植物性饮食中 1%，并在短期喂养试验中评估了它们对斑马鱼免疫反应和肠道形态的影响。所有提取物均表现出针对病毒性出血性败血症和/或传染性胰腺坏死病毒的体外抗病毒活性。 F.vesiculosus和U.rigida的甲醇提取物富含饱和脂肪酸，并且对多种细菌表现出体外抗菌作用。最有希望的结果是在体内使用水泡镰刀菌甲醇提取物获得的，该提取物单独掺入饮食中时发挥抗炎作用，与其他提取物结合时诱导促炎细胞因子表达。此外，饮食中添加提取物可以改善肠道形态。 总之，本研究获得的结果支持藻类作为水产养殖业生物活性化合物天然来源的潜力。