The CD152, as named CTLA-4 (Cytotoxic T lymphocyte-associated antigen-4), is an important costimulatory molecule on the surface of T cells and plays an essential role in the cell-mediated immune response. In this work, Nile tilapia (Oreochromis niloticus) CD152 (OnCD152) was successfully cloned, and its characterization in response to bacterial pathogens and interaction with its ligand OnCD80/86 was also investigated. The open reading frame (ORF) of OnCD152 was 705 bp, encoding a polypeptide with 234 amino acids. The OnCD152 protein shared some homology with other known CD152 molecule from teleost species, containing conservative key sites, namely YPPPY, GNGT and four cysteine residues (Cys 45, Cys 97, Cys 123, Cys 151). The mRNA level of OnCD152 was extensively expressed in the collected healthy tissues. Following the stimulation of Poly (I:C), Streptococcus agalactiae and Aeromonas hydrophila, CD152 was significantly upregulated in the head kidney and spleen. The transcriptional upregulations of OnCD152 were also detected in Nile tilapia leukocytes after in vitro stimulations with Poly (I:C), S. agalactiae and A. hydrophila. In addition, the recombinant protein (r)OnCD152 was purified, and its binding ability to (r)CD80/86 strengthen with the increase of concentration. Taken together, this study demonstrated that OnCD152 was likely involved in host immune response against bacterial pathogens. Moreover, this research first cover about the capacity of OnCD152 binding with ligand CD80/86 in Nile tilapia (Oreochromis niloticus), which enrich the understanding for exploring the CD152 function in immune response in teleost fish in the future.

CD152，命名为CTLA-4（细胞毒性T淋巴细胞相关抗原4），是T细胞表面重要的共刺激分子，在细胞介导的免疫反应中起重要作用。在这项工作中，尼罗罗非鱼 ( Oreochromis niloticus ) CD152 ( OnCD152 ) 被成功克隆，并研究了其响应细菌病原体的特性以及与其配体 OnCD80/86 的相互作用。OnCD152的开放阅读框（ORF）为705 bp，编码234个氨基酸的多肽。OnCD152 蛋白与来自硬骨鱼物种的其他已知 CD152 分子具有一些同源性，包含保守的关键位点，即 YPPPY、GNGT 和四个半胱氨酸残基（Cys 45、Cys 97、Cys 123、Cys 151）。OnCD152的 mRNA 水平在收集的健康组织中广泛表达。在 Poly (I:C)、无乳链球菌和嗜水气单胞菌刺激后，CD152在头肾和脾脏中显着上调。在用 Poly (I:C) 、无乳链球菌和嗜水链球菌进行体外刺激后，在尼罗罗非鱼白细胞中也检测到OnCD152的转录上调。此外，重组蛋白(r)OnCD152得到纯化，其与(r)CD80/86的结合能力随着浓度的增加而增强。总之，这项研究表明 OnCD152 可能参与宿主针对细菌病原体的免疫反应。此外，本研究首次涵盖了OnCD152与尼罗罗非鱼（Oreochromis niloticus）配体CD80/86结合的能力，丰富了未来探索CD152在硬骨鱼免疫反应中的作用的认识。