Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Bundoora, Vic., Australia.
School of Medicine, Deakin University, Waurn Ponds, Vic., Australia.
FEBS J. 2021 May;288(10):3164-3185. doi: 10.1111/febs.15654. Epub 2020 Dec 18.
CD4 T cells recognize peptides presented by major histocompatibility complex class II molecules (MHC-II). These peptides are generally derived from exogenous antigens. Macroautophagy has been reported to promote endogenous antigen presentation in viral infections. However, whether influenza A virus (IAV) infection-induced macroautophagy also leads to endogenous antigen presentation through MHC-II is still debated. In this study, we show that IAV infection leads to endogenous presentation of an immunodominant viral epitope NP by MHC-II to CD4 T cells. Mechanistically, such MHC-II-restricted endogenous IAV antigen presentation requires de novo protein synthesis as it is inhibited by the protein synthesis inhibitor cycloheximide, and a functional ER-Golgi network as it is totally blocked by Brefeldin A. These results indicate that MHC-II-restricted endogenous IAV antigen presentation is dependent on de novo antigen and/or MHC-II synthesis, and transportation through the ER-Golgi network. Furthermore, such endogenous IAV antigen presentation by MHC-II is enhanced by TAP deficiency, indicating some antigenic peptides are of cytosolic origin. Most importantly, the bulk of such MHC-II-restricted endogenous IAV antigen presentation is blocked by autophagy inhibitors (3-MA and E64d) and deletion of autophagy-related genes, such as Beclin1 and Atg7. We have further demonstrated that in dendritic cells, IAV infection prevents autophagosome-lysosome fusion and promotes autophagosome fusion with MHC class II compartment (MIIC), which likely promotes endogenous IAV antigen presentation by MHC-II. Our results provide strong evidence that IAV infection-induced autophagosome formation facilitates endogenous IAV antigen presentation by MHC-II to CD4 T cells. The implication for influenza vaccine design is discussed.
CD4 T 细胞识别主要组织相容性复合体 II 类分子（MHC-II）呈递的肽。这些肽通常来自外源性抗原。据报道，巨自噬可促进病毒感染中的内源性抗原呈递。然而，甲型流感病毒（IAV）感染诱导的巨自噬是否也通过 MHC-II 导致内源性抗原呈递仍存在争议。在这项研究中，我们表明 IAV 感染导致 MHC-II 对 CD4 T 细胞呈递免疫优势病毒表位 NP。从机制上讲，这种 MHC-II 限制的内源性 IAV 抗原呈递需要从头合成蛋白质，因为它被蛋白质合成抑制剂环己酰亚胺抑制，并且需要功能正常的内质网-高尔基体网络，因为它被布雷菲德菌素 A 完全阻断。这些结果表明，MHC-II 限制的内源性 IAV 抗原呈递依赖于从头抗原和/或 MHC-II 合成以及通过内质网-高尔基体网络的运输。此外，MHC-II 呈递的这种内源性 IAV 抗原呈递被 TAP 缺乏增强，表明一些抗原肽来源于细胞质。最重要的是，这种 MHC-II 限制的内源性 IAV 抗原呈递的大部分被自噬抑制剂（3-MA 和 E64d）和自噬相关基因（如 Beclin1 和 Atg7）的缺失所阻断。我们进一步证明，在树突状细胞中，IAV 感染阻止自噬体-溶酶体融合并促进自噬体与 MHC Ⅱ类隔室（MIIC）融合，这可能促进 MHC-II 呈递内源性 IAV 抗原。我们的研究结果为 IAV 感染诱导的自噬体形成促进 MHC-II 呈递内源性 IAV 抗原呈递提供了有力证据。讨论了流感疫苗设计的含义。
