Department of Animal and Aquaculture Sciences, Faculty of Biosciences, Norwegian University of Life Sciences, Oluf Thesens Vei 6, 1433, Ås, Norway.
Department of Animal and Aquaculture Sciences, Faculty of Biosciences, Norwegian University of Life Sciences, Oluf Thesens Vei 6, 1433, Ås, Norway.
Fish Shellfish Immunol. 2024 May;148:109506. doi: 10.1016/j.fsi.2024.109506. Epub 2024 Mar 18.
Paecilomyces variotii (a filamentous fungus), is a promising novel protein source in fish feeds due to its high nutritional value. Also, P. variotii has Microbial-Associated Molecular Patterns (MAMPs) such as glucans and nucleic acids that could modulate the host's immune response. To understand the potential bioactive properties of this fungus in Atlantic salmon (Salmo salar), our study was conducted to evaluate the gene expression of immune-related biomarkers (e.g., cytokines, effector molecules and receptors) on primary cultures from salmon head kidney (HKLs) and spleen leukocytes (SLs) exposed to either UV inactivated or fractions from P. variotii with or without inactivated Moritella viscosa (a skin pathogen in salmonids). Moreover, the effect of the fermentation conditions and down-stream processing on the physical ultrastructure and cell wall glucan content of P. variotii was characterized. The results showed that drying had a significant effect on the cell wall ultrastructure of the fungi and the choice of fermentation has a significant effect on the quantity of β-glucans in P. variotii. Furthermore, stimulating Atlantic salmon HKLs and SLs with P. variotii and its fractions induced gene expression related to pro-inflammatory (tnfα, il1β) and antimicrobial response (cath2) in HKLs, while response in SLs was related to both pro-inflammatory and regulatory response (tnfα, il6 and il10). Similarly, the stimulation with inactivated M. viscosa alone led to an up-regulation of genes related to pro-inflammatory (tnfα, il1β, il6) antimicrobial response (cath2), intra-cellular signalling and recognition of M. viscosa (sclra, sclrb) and a suppression of regulatory response (il10) in both HKLs and SLs. Interestingly, the co-stimulation of cells with P. variotii and M. viscosa induced immune homeostasis (il6, tgfβ) and antimicrobial response (cath2) in SLs at 48h. Thus, P. variotii induces immune activation and cellular communication in Atlantic salmon HKLs and SLs and modulates M. viscosa induced pro-inflammatory responses in SLs. Taken together, the results from physical and chemical characterization of the fungi, along with the differential gene expression of key immune biomarkers, provides a theoretical basis for designing feeding trials and optimize diets with P. variotii as a functional novel feed ingredient for Atlantic salmon.
多形拟青霉（一种丝状真菌）因其具有高营养价值，是鱼类饲料中很有前途的新型蛋白质来源。此外，多形拟青霉具有微生物相关分子模式（MAMPs），如葡聚糖和核酸，这些物质可以调节宿主的免疫反应。为了了解这种真菌在大西洋鲑鱼（Salmo salar）中的潜在生物活性特性，我们进行了这项研究，以评估在暴露于紫外线失活的多形拟青霉或其无活性的粘质沙雷氏菌（鲑科鱼类的皮肤病原体）的多形拟青霉的 fractions 时，从鲑鱼头肾（HKL）和脾脏白细胞（SL）的原代培养物中免疫相关生物标志物（例如细胞因子、效应分子和受体）的基因表达。此外，还表征了发酵条件和下游加工对多形拟青霉的物理超微结构和细胞壁葡聚糖含量的影响。结果表明，干燥对真菌细胞壁的超微结构有显著影响，发酵方式的选择对多形拟青霉β-葡聚糖的含量有显著影响。此外，用多形拟青霉及其 fractions 刺激大西洋鲑鱼的 HKL 和 SL 会诱导 HKL 中与促炎（tnfα、il1β）和抗微生物反应（cath2）相关的基因表达，而 SL 中的反应则与促炎和调节反应（tnfα、il6 和 il10）有关。同样，单独用失活的粘质沙雷氏菌刺激会导致与促炎（tnfα、il1β、il6）抗微生物反应（cath2）、细胞内信号转导和粘质沙雷氏菌识别（sclra、sclrb）以及调节反应（il10）抑制相关基因的上调，HKL 和 SL 中均有此反应。有趣的是，细胞与多形拟青霉和粘质沙雷氏菌的共同刺激会诱导 SL 中免疫稳态（il6、tgfβ）和抗微生物反应（cath2）在 48 小时内的反应。因此，多形拟青霉会诱导大西洋鲑鱼 HKL 和 SL 的免疫激活和细胞通讯，并调节 SL 中粘质沙雷氏菌诱导的促炎反应。总之，真菌的物理和化学特性的表征以及关键免疫生物标志物的差异基因表达为设计以多形拟青霉为功能新型饲料成分的大西洋鲑鱼喂养试验和优化饮食提供了理论依据。
