Department of Aquaculture, National Taiwan Ocean University, Keelung, Taiwan.
Department of Aquaculture, National Taiwan Ocean University, Keelung, Taiwan; College of Aquaculture and Fisheries, Can Tho University, Viet Nam.
Fish Shellfish Immunol. 2022 Jul;126:34-46. doi: 10.1016/j.fsi.2022.05.032. Epub 2022 May 19.
Nile tilapia (Oreochromis niloticus) is an important food fish species that is mainly cultivated in tropical and subtropical countries. However, microbial diseases have created various difficulties for this industry. The fundamental prerequisite for tackling disease outbreak prevention and disease resistance is to know how hosts' immune responses against invading microbes are initiated. Toll-like receptors (TLRs) are vital pattern recognition receptors and play pivotal roles in the cellular innate immunity defense that is able to recognize pathogen-associated molecular patterns (PAMPs). In this study, Oreochromis niloticus TLR23 (OnTLR23) was cloned and bioinformatic analyses revealed that OnTLR23 is not an ortholog of mammalian TLR13 as previously suggested. The basal transcript level of OnTLR23 was found to be higher in the immune-related organs and was upregulated in the spleen and/or head kidney following Aeromonas hydrophila, Streptococcus agalactiae or poly I:C injections, and increased in the melanomacrophage-like tilapia head kidney (THK) cell line after LPS and zymosan stimulation. Furthermore, we demonstrated for the first time that OnTLR23 locates mainly in the intracellular region in fish cells and the constitutively active form of OnTLR23 promotes the expression of molecules related to antigen presentation, proinflammatory cytokines, antimicrobial peptides and type I interferon in THK cells. A co-immunoprecipitation assay revealed that OnTLR23 can interact with both OnMyD88 and OnTRIF, but not with OnTIRAP. A luciferase assay showed that the NF-κB activity was not elevated in the OnTLR23 overexpressed THK cells after treatment with ligand for TLR13 as well as other known purified bacterial-derived ligands of TLRs. Taken together, OnTLR23 is likely to recruit OnMyD88 and OnTRIF as adaptors to induce the expression of various effectors in melanomacrophages, but its corresponding ligand is an issue awaiting further investigation.
尼罗罗非鱼（Oreochromis niloticus）是一种重要的食用鱼类，主要在热带和亚热带国家养殖。然而，微生物疾病给这个产业带来了各种困难。应对疾病爆发预防和抗病性的根本前提是要了解宿主对入侵微生物的免疫反应是如何启动的。Toll 样受体（TLRs）是重要的模式识别受体，在细胞固有免疫防御中发挥关键作用，能够识别病原体相关分子模式（PAMPs）。在这项研究中，克隆了尼罗罗非鱼 TLR23（OnTLR23），生物信息学分析表明，OnTLR23 不是哺乳动物 TLR13 的同源物，如先前所述。OnTLR23 的基础转录水平在免疫相关器官中较高，在受到嗜水气单胞菌、无乳链球菌或聚 I:C 注射后，在脾脏和/或头肾中上调，并在 LPS 和酵母聚糖刺激后在黑色素巨噬细胞样罗非鱼头肾（THK）细胞系中增加。此外，我们首次证明 OnTLR23 主要位于鱼类细胞的细胞内区域，并且 OnTLR23 的组成激活形式促进了 THK 细胞中与抗原呈递、促炎细胞因子、抗菌肽和 I 型干扰素相关分子的表达。共免疫沉淀试验表明，OnTLR23 可以与 OnMyD88 和 OnTRIF 相互作用，但不能与 OnTIRAP 相互作用。荧光素酶测定显示，在用 TLR13 的配体以及其他已知的纯化细菌衍生的 TLR 配体处理后，OnTLR23 过表达的 THK 细胞中 NF-κB 活性没有升高。综上所述，OnTLR23 可能招募 OnMyD88 和 OnTRIF 作为接头，诱导黑色素巨噬细胞中各种效应子的表达，但它的相应配体是一个有待进一步研究的问题。
