A Palindromic CpG-Containing Phosphodiester Oligodeoxynucleotide as a Mucosal Adjuvant Stimulates Plasmacytoid Dendritic Cell-Mediated TH1 Immunity

BackgroundCpG oligodeoxynucleotides (ODNs), resembling bacterial DNA, are currently tested in clinical trials as vaccine adjuvants. They have the nuclease-resistant phosphorothioate bond; the immune responses elicited differ according to the CpG ODN sequence and vaccination method. To develop a CpG ODN that can induce plasmacytoid dendritic cell (pDC)-mediated TH1 immunity through the mucosa, we constructed phosphodiester G9.1 comprising one palindromic CpG motif with unique polyguanosine-runs that allows degradation similar to naturally occurring bacterial DNA.MethodsTH1 and TH2 immunity activation was evaluated by cytokine production pattern and T-bet/GATA-3 ratio in human peripheral blood mononuclear cells and mouse bone marrow cells. Adjuvanticity was evaluated in mice administered G9.1 with diphtheria toxoid (DT) through nasal vaccination.ResultsG9.1 exhibited stronger IFN-α-inducing activity than A-class CpG ODN2216 and increased T-bet/GATA-3 ratio by enhancing T-bet expression. Nasally administered G9.1 plus DT induced DT-specific mucosal IgA and serum IgG, but not IgE, responses with antitoxin activity in C57BL/6 and BALB/c mice, possibly due to IFN/BAFF production. Induction of TH1, but not TH2, -type Abs depended completely on pDCs, the first in vivo demonstration by CpG ODNs.ConclusionsG9.1 is a promising mucosal adjuvant for induction of pDC-mediated TH1 immunity.背景：CpG寡脱氧核苷酸（CpG oligodeoxynucleotides, ODNs）结构类似细菌DNA，目前作为疫苗佐剂正处于临床试验阶段。这类分子带有抗核酸酶降解的硫代磷酸酯键，其诱导的免疫应答会因CpG ODN序列与接种方式的不同而存在差异。为开发一种可通过黏膜途径诱导浆细胞样树突状细胞（plasmacytoid dendritic cell, pDC）介导的TH1型免疫的CpG ODN，我们构建了磷酸二酯型G9.1，其包含一段回文CpG基序，带有独特的多聚鸟苷序列，可实现与天然细菌DNA相似的降解过程。 方法：通过检测人外周血单个核细胞与小鼠骨髓细胞中的细胞因子分泌模式及T-bet/GATA-3比值，评估TH1与TH2型免疫的激活情况；将G9.1与白喉类毒素（diphtheria toxoid, DT）联合经鼻内接种给药于小鼠，以此评价其佐剂活性。 结果：G9.1的IFN-α诱导活性优于A型CpG ODN2216，且可通过上调T-bet表达提升T-bet/GATA-3比值。在C57BL/6与BALB/c小鼠中，鼻内联合接种G9.1与DT可诱导出具有抗毒素活性的DT特异性黏膜IgA与血清IgG应答，而不引发IgE应答，该效应可能与IFN/BAFF的产生有关。TH1型而非TH2型抗体的诱导完全依赖于pDC，这是CpG ODN首次在体内证实该作用机制。 结论：G9.1是一种极具潜力的黏膜佐剂，可诱导pDC介导的TH1型免疫。