Chen Chen, Men Zhichao, Pu Xianglin, Lu Mingmin, Xu Lixin, Yan Ruofeng, Li Xiangrui, Song Xiaokai
Ministry of Education (MOE) Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210095, PR China.
Ministry of Education (MOE) Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210095, PR China.
Poult Sci. 2025 Jul 3;104(10):105525. doi: 10.1016/j.psj.2025.105525.
Toll-like receptor (TLR)-mediated recognition of specific ligands is critical for initiating innate immunity against Eimeria infections. However, the avian-specific TLR15 has unclear immunological functions, including its specific ligands and role in anti-coccidia immunity. In this study, an aspartyl protease from Eimeria tenella (EteASP) was identified as a potential TLR15 ligand by co-immunoprecipitation. Two distinct TLR15-expressing innate immune cell populations, macrophages and dendritic cells, were employed as models to investigate the immune responses triggered by recombinant EteASP protein (rEteASP). In macrophages, rEteASP induced robust immune activation, associated with the stimulation of both NF-κB and MAPK pathways. This activation correlated with increased production of pro-inflammatory cytokines (IL-1β, IL-6, TNF-α), nitric oxide, and reactive oxygen species, alongside enhanced phagocytosis. Furthermore, rEteASP promoted classical dendritic cell activation in chicken bone marrow-derived dendritic cells, marked by stellate morphology and upregulated CD11c and MHC II surface expression. The activation patterns in chBMDCs mirrored those in macrophages, characterized by increased production of immune mediators. A mixed lymphocyte reaction (MLR) further demonstrated that rEteASP-activated dendritic cells efficiently triggered naive T cell activation, driving a shift towards balanced Th1/Th2-type cellular immune response. Collectively, these findings establish EteASP as a potent immunomodulator capable of activating key innate immune effector functions in macrophages and dendritic cells, and bridging to adaptive immunity. Our data implicate TLR15 as a potential receptor contributing to these responses, broadening the investigation of TLR15 ligands in protozoa and offering novel insights into Eimeria-host immune interactions. However, the potential involvement of additional pattern recognition receptors in EteASP recognition and the definitive role of TLR15 requires further investigation.
Toll样受体（TLR）介导的对特定配体的识别对于启动针对艾美耳球虫感染的固有免疫至关重要。然而，禽类特异性TLR15的免疫功能尚不清楚，包括其特异性配体以及在抗球虫免疫中的作用。在本研究中，通过免疫共沉淀鉴定出一种来自柔嫩艾美耳球虫的天冬氨酸蛋白酶（EteASP）作为潜在的TLR15配体。以两种表达TLR15的不同固有免疫细胞群体，即巨噬细胞和树突状细胞为模型，研究重组EteASP蛋白（rEteASP）引发的免疫反应。在巨噬细胞中，rEteASP诱导强烈的免疫激活，这与NF-κB和MAPK途径的刺激相关。这种激活与促炎细胞因子（IL-1β、IL-6、TNF-α）、一氧化氮和活性氧的产生增加以及吞噬作用增强相关。此外，rEteASP促进鸡骨髓来源的树突状细胞中经典树突状细胞的激活，其特征为星状形态以及CD11c和MHC II表面表达上调。鸡骨髓来源的树突状细胞中的激活模式与巨噬细胞中的相似，其特征为免疫介质的产生增加。混合淋巴细胞反应（MLR）进一步证明，rEteASP激活的树突状细胞有效地触发了初始T细胞的激活，促使向平衡的Th1/Th2型细胞免疫反应转变。总体而言，这些发现确立了EteASP作为一种有效的免疫调节剂，能够激活巨噬细胞和树突状细胞中的关键固有免疫效应功能，并与适应性免疫相衔接。我们的数据表明TLR15作为可能参与这些反应的受体，拓宽了对原生动物中TLR15配体的研究，并为艾美耳球虫与宿主的免疫相互作用提供了新的见解。然而，其他模式识别受体在EteASP识别中的潜在参与以及TLR15的确切作用仍需进一步研究。
