For most frequent respiratory viruses, there is an urgent need for a universal influenza vaccine to provide cross-protection against intra- and heterosubtypes. We previously developed an Escherichia coli fusion protein expressed extracellular domain of matrix 2 (M2e) and nucleoprotein, named NM2e, and then combined it with an aluminum adjuvant, forming a universal vaccine. Although NM2e has demonstrated a protective effect against the influenza virus in mice to some extent, further improvement is still needed for the induction of immune responses ensuring adequate cross-protection against influenza. Herein, we fabricated a cationic solid lipid nanoadjuvant using poly(lactic acid) (PLA) and dimethyl-dioctadecyl-ammonium bromide (DDAB) and loaded NM2e to generate an NM2e@DDAB/PLA nanovaccine (Nv). In vitro experiments suggested that bone marrow-derived dendritic cells incubated with Nv exhibited ∼4-fold higher antigen (Ag) uptake than NM2e at 16 h along with efficient activation by NM2e@DDAB/PLA Nv. In vivo experiments revealed that Ag of the Nv group stayed in lymph nodes (LNs) for more than 14 days after initial immunization and DCs in LNs were evidently activated and matured. Furthermore, the Nv primed T and B cells for robust humoral and cellular immune responses after immunization. It also induced a ratio of IgG_2a/IgG₁ higher than that of NM2e to a considerable extent. Moreover, NM2e@DDAB/PLA Nv quickly restored body weight and improved survival of homo- and heterosubtype influenza challenged mice, and the cross-protection efficiency was over 90%. Collectively, our study demonstrated that NM2e@DDAB/PLA Nv could offer notable protection against homo- and heterosubtype influenza virus challenges, offering the potential for the development of a universal influenza vaccine.

中文翻译：

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二甲基双十八烷基溴化铵/聚乳酸纳米佐剂增强基于 NM2e 的通用流感疫苗的免疫和交叉保护

对于最常见的呼吸道病毒，迫切需要一种通用流感疫苗来提供针对亚型内和异亚型的交叉保护。我们之前开发了表达基质2胞外域（M2e）和核蛋白的大肠杆菌融合蛋白，命名为NM2e，然后将其与铝佐剂结合，形成通用疫苗。尽管NM2e已在小鼠体内表现出一定程度的针对流感病毒的保护作用，但仍需要进一步改进以诱导免疫反应，确保充分的针对流感的交叉保护。在此，我们使用聚乳酸（PLA）和二甲基双十八烷基溴化铵（DDAB）制备了阳离子固体脂质纳米佐剂，并负载NM2e以生成NM2e@DDAB/PLA纳米疫苗（Nv）。体外实验表明，与 Nv 一起孵育的骨髓源性树突状细胞在 16 小时时表现出比 NM2e 高约 4 倍的抗原 (Ag) 摄取，并且被 NM2e@DDAB/PLA Nv 有效激活。体内实验显示，初次免疫后，Nv组的Ag在淋巴结（LN）中停留时间超过14天，且LN中的DC明显活化和成熟。此外，Nv 还可以在免疫后引发 T 和 B 细胞产生强大的体液和细胞免疫反应。它还诱导了相当程度高于NM2e的IgG _2a /IgG ₁比率。此外，NM2e@DDAB/PLA Nv能快速恢复同型和异型流感攻击小鼠的体重并提高其存活率，交叉保护效率超过90%。总的来说，我们的研究表明，NM2e@DDAB/PLA Nv 可以针对同型和异型流感病毒的挑战提供显着的保护，为开发通用流感疫苗提供了潜力。