In subunit vaccines, aluminum salts (Alum) are commonly used as adjuvants, but with limited cellular immune responses. To overcome this limitation, CpG oligodeoxynucleotides (ODNs) have been used in combination with Alum. However, current combined usage of Alum and CpG is limited to linear mixtures, and the underlying interaction mechanism between CpG and Alum is not well understood. Thus, we propose to chemically conjugate Alum nanoparticles and CpG (with 5′ or 3′ end exposed) to design combination adjuvants. Our study demonstrates that compared to the 3′-end exposure, the 5′-end exposure of CpG in combination adjuvants (Al-CpG-5′) enhances the activation of bone-marrow derived dendritic cells (BMDCs) and promotes Th1 and Th2 cytokine secretion. We used the SARS-CoV-2 receptor binding domain (RBD) and hepatitis B surface antigen (HBsAg) as model antigens to demonstrate that Al-CpG-5′ enhanced antigen-specific antibody production and upregulated cytotoxic T lymphocyte markers. Additionally, Al-CpG-5′ allows for coordinated adaptive immune responses even at lower doses of both CpG ODNs and HBsAg antigens, and enhances lymph node transport of antigens and activation of dendritic cells, promoting T cell differentiation and B cell activation. Our novel Alum-CPG strategy points the way towards broadening the use of nanoadjuvants for both prophylactic and therapeutic vaccines.

中文翻译：

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羟基氧化铝纳米颗粒上 CpG 结合的方向决定了组合佐剂的免疫刺激作用

在亚单位疫苗中，铝盐（明矾）通常用作佐剂，但细胞免疫反应有限。为了克服这一限制，CpG 寡脱氧核苷酸 (ODN) 已与明矾结合使用。然而，目前明矾和 CpG 的组合使用仅限于线性混合物，并且 CpG 和明矾之间的潜在相互作用机制尚不清楚。因此，我们建议将明矾纳米颗粒和 CpG（5' 或 3' 末端暴露）化学缀合来设计组合佐剂。我们的研究表明，与 3' 端暴露相比，组合佐剂 (Al-CpG-5') 中 CpG 的 5' 端暴露增强了骨髓源性树突状细胞 (BMDC) 的活化并促进 Th1 和 Th2细胞因子的分泌。我们使用 SARS-CoV-2 受体结合域 (RBD) 和乙型肝炎表面抗原 (HBsAg) 作为模型抗原，证明 Al-CpG-5' 增强抗原特异性抗体的产生并上调细胞毒性 T 淋巴细胞标记物。此外，即使在较低剂量的 CpG ODN 和 HBsAg 抗原下，Al-CpG-5' 也能实现协调的适应性免疫应答，并增强抗原的淋巴结转运和树突状细胞的活化，促进 T 细胞分化和 B 细胞活化。我们新颖的 Alum-CPG 策略为扩大纳米佐剂在预防性和治疗性疫苗中的应用指明了道路。