Department of Microbiology and Immunology, Institute of Biomedicine, University of Gothenburg Vaccine Research Institute (GUVAX), Sahlgrenska Academy at University of Gothenburg, Gothenburg, Sweden.
Department of Organismal Biology, Uppsala University, Uppsala, Sweden.
Front Immunol. 2019 Feb 19;10:269. doi: 10.3389/fimmu.2019.00269. eCollection 2019.
Cholera toxin (CT) is widely used as an effective adjuvant in experimental immunology for inducing mucosal immune responses; yet its mechanisms of adjuvant action remain incompletely defined. Here, we demonstrate that mice lacking NFκB, compared to wild-type (WT) mice, had a 90% reduction in their systemic and mucosal immune responses to oral immunization with a model protein antigen [Ovalbumin (OVA)] given together with CT. Further, NFκB mouse dendritic cells (DCs) stimulated with CT showed reduced expression of MHCII and co-stimulatory molecules, such as CD80 and CD86, as well as of IL-1β, and other pro-inflammatory cytokines compared to WT DCs. Using a human monocyte cell line THP1 with an NFκB activation reporter system, we show that CT induced NFκB signaling in human monocytes, and that inhibition of the cyclic AMP-protein kinase A (cAMP-PKA) pathway abrogated the activation and nuclear translocation of NFκB. In a human monocyte-CD4 T cell co-culture system we further show that the strong Th17 response induced by CT treatment of monocytes was abolished by blocking the classical but not the alternative NFκB signaling pathway of monocytes. Our results indicate that activation of classical (canonical) NFκB pathway signaling in antigen-presenting cells (APCs) by CT is important for CT's adjuvant enhancement of Th17 responses. Similar findings were obtained using the almost completely detoxified mmCT mutant protein as adjuvant. Altogether, our results demonstrate that activation of the classical NFκB signal transduction pathway in APCs is important for the adjuvant action of both CT and mmCT.
霍乱毒素 (CT) 广泛用作实验免疫学中的有效佐剂，以诱导粘膜免疫反应；然而，其佐剂作用的机制仍不完全明确。在这里，我们证明与野生型 (WT) 小鼠相比，缺乏 NFκB 的小鼠对口服免疫用模型蛋白抗原 [卵清蛋白 (OVA)] 与 CT 一起给予的全身性和粘膜免疫反应降低了 90%。此外，用 CT 刺激的 NFκB 小鼠树突状细胞 (DCs) 与 WT DCs 相比，表达 MHCII 和共刺激分子（如 CD80 和 CD86）以及 IL-1β 和其他促炎细胞因子的表达降低。使用具有 NFκB 激活报告系统的人单核细胞系 THP1，我们表明 CT 诱导人单核细胞中的 NFκB 信号转导，并且抑制环 AMP-蛋白激酶 A (cAMP-PKA) 途径会阻断 NFκB 的激活和核易位。在单核细胞-CD4 T 细胞共培养系统中，我们进一步表明 CT 处理单核细胞诱导的强烈 Th17 反应被阻断单核细胞经典而非替代 NFκB 信号通路所消除。我们的结果表明，抗原呈递细胞 (APC) 中 CT 激活经典 (经典) NFκB 途径信号转导对于 CT 增强 Th17 反应的佐剂作用很重要。使用几乎完全解毒的 mmCT 突变蛋白作为佐剂也获得了类似的发现。总之，我们的结果表明，APC 中经典 NFκB 信号转导通路的激活对于 CT 和 mmCT 的佐剂作用都很重要。
