Temasek Life Sciences Laboratory, 1 Research Link, National University of Singapore, Singapore, Singapore.
Front Immunol. 2023 Feb 20;14:1146387. doi: 10.3389/fimmu.2023.1146387. eCollection 2023.
Mucosal immunity plays a critical role in the protection of teleost fish against infection, but mucosal immunoglobulin of important aquaculture species unique to Southeast Asia remained greatly understudied. In this study, the sequence of immunoglobulin T (IgT) from Asian sea bass (ASB) is described for the first time. IgT of ASB possesses the characteristic structure of immunoglobulin with a variable heavy chain and four CH4 domains. The CH2-CH4 domains and full-length IgT were expressed and CH2-CH4 specific antibody was validated against full-length IgT expressed in Sf9 III cells. Subsequent use of the anti-CH2-CH4 antibody in immunofluorescence staining confirmed the presence of IgT-positive cells in the ASB gill and intestine. The constitutive expression of ASB IgT was characterized in different tissues and in response to red-spotted grouper nervous necrosis virus (RGNNV) infection. The highest basal expression of secretory IgT (sIgT) was observed in the mucosal and lymphoid tissues such as the gills, intestine and head kidney. Following NNV infection, IgT expression was upregulated in the head kidney and mucosal tissues. Moreover, a significant increase in localized IgT was found in gills and intestines of infected fish on day 14 post-infection. Interestingly, a significant increase in NNV-specific IgT secretion was only observed in the gills of the infected group. Our results suggest that ASB IgT may play an important role in the adaptive mucosal immune responses against viral infection and could potentially be adapted as a tool for the evaluation of prospective mucosal vaccines and adjuvants for the species.
黏膜免疫在保护鱼类免受感染方面起着至关重要的作用，但东南亚特有水产养殖物种的黏膜免疫球蛋白仍未得到充分研究。本研究首次描述了亚洲海鲈（ASB）的免疫球蛋白 T（IgT）序列。ASB 的 IgT 具有免疫球蛋白的特征结构，包括可变重链和四个 CH4 结构域。CH2-CH4 结构域和全长 IgT 得到了表达，并针对 Sf9 III 细胞中表达的全长 IgT 进行了 CH2-CH4 特异性抗体验证。随后，使用抗-CH2-CH4 抗体进行免疫荧光染色，证实了 IgT 阳性细胞存在于 ASB 的鳃和肠道中。在不同组织中以及对红鳍东方鲀神经坏死病毒（RGNNV）感染的反应中，对 ASB IgT 的组成型表达进行了特征描述。在黏膜和淋巴组织（如鳃、肠和头肾）中观察到分泌型 IgT（sIgT）的基础表达最高。在 NNV 感染后，头肾和黏膜组织中的 IgT 表达上调。此外，在感染后第 14 天，感染鱼的鳃和肠道中发现局部 IgT 显著增加。有趣的是，仅在感染组的鳃中观察到 NNV 特异性 IgT 分泌的显著增加。我们的结果表明，ASB IgT 可能在针对病毒感染的适应性黏膜免疫反应中发挥重要作用，并可能被用作评估该物种潜在黏膜疫苗和佐剂的工具。
