Table_1_Supplementation of Dietary Crude Lentinan Improves the Intestinal Microbiota and Immune Barrier in Rainbow Trout (Oncorhynchus mykiss) Infected by Infectious Hematopoietic Necrosis Virus.doc

The effects of crude lentinan (CLNT) on the intestinal microbiota and the immune barrier were evaluated in rainbow trout (Oncorhynchus mykiss) infected by infectious hematopoietic necrosis virus (IHNV). The results showed that supplementary CLNT declined the rainbow trout mortality caused by IHNV, which suggested that CLNT has preventive effects on IHNV infection. IHNV destroyed intestinal integrity, as well as caused the intestinal oxidative and damage in rainbow trout. Supplementary CLNT significantly strengthened the intestinal immune barrier by declining intestinal permeability, as well as enhancing intestinal antioxidant and anti-inflammatory abilities in IHNV-infected rainbow trout (P<0.05). In addition, CLNT modified the aberrant changes of intestinal microbiota induced by IHNV, mainly represented by promoting the growths of Carnobacterium and Deefgea and inhibiting Mycobacterium and Nannocystis. Especially, supplementing with CLNT significantly promoted the growth of short-chain fatty acid–producing bacteria (P<0.05) and consequently increased the production of acetic acid, butanoic acid, and hexanoic acid in the intestine of IHNV-infected rainbow trout. Furthermore, it was speculated that CLNT could regulate the self-serving metabolic pathways of intestinal microbiota induced by IHNV, such as fatty acid metabolism and amino acid metabolism. Together, CLNT played the antiviral effects on IHNV infection through strengthening the intestinal immune barrier, as well as regulating intestinal microbiota and SCFA metabolism in rainbow trout. The present data revealed that CLNT exerted a promising prebiotic role in preventing the rainbow trout from IHNV infection.

本研究评估了粗制香菇多糖（crude lentinan, CLNT）对感染传染性造血器官坏死病毒（infectious hematopoietic necrosis virus, IHNV）的虹鳟（Oncorhynchus mykiss）肠道菌群与肠道免疫屏障的影响。结果显示，补充CLNT可降低IHNV感染诱导的虹鳟死亡率，表明CLNT对IHNV感染具有预防作用。IHNV可破坏虹鳟肠道完整性，并引发肠道氧化损伤。补充CLNT可通过降低肠通透性、增强IHNV感染虹鳟的肠道抗氧化与抗炎能力，显著强化肠道免疫屏障（P<0.05）。此外，CLNT可改善IHNV诱导的肠道菌群异常改变，主要表现为促进肉杆菌属（Carnobacterium）与迪夫吉亚菌属（Deefgea）的增殖，抑制分枝杆菌属（Mycobacterium）与小囊菌属（Nannocystis）的生长。尤为关键的是，补充CLNT可显著促进产短链脂肪酸菌（short-chain fatty acid–producing bacteria）的增殖（P<0.05），进而提升IHNV感染虹鳟肠道内乙酸、丁酸与己酸的生成水平。进一步推测，CLNT可调控IHNV诱导的肠道菌群自身代谢通路，如脂肪酸代谢与氨基酸代谢。综上，CLNT可通过强化肠道免疫屏障、调节虹鳟肠道菌群与短链脂肪酸代谢，发挥抗IHNV感染的作用。本研究数据表明，CLNT在预防虹鳟IHNV感染方面具有极具潜力的益生元功效。