HBV-ODN诱导乙型肝炎病毒免疫耐受的研究

Hepatitis B virus-induced immune tolerance is a key factor for persistent infection. However, the mechanism by which HBV contributes to negative regulation and thus immune tolerance is still poorly understood. In our previous researches, we reported that unmethylated CpG ODNs (HBV-CpG) from the HBV genome (HBV-CpG) induced robust expression of IFN-α by pDCs. We also identified inhibitory guanosine-rich ODNs in the HBV genome (HBV-ODN) that are capable of blocking HBV-CpG-induced IFN-α production. Meanwhile, we found that the HBV-ODN could induce high levels of IL-10, a cytokine with negative regulatory properties. Thus, we hypothesize that the HBV-ODN could be related to the maintenance of immune tolerance of Hepatitis B. Therefore we would like to prove that the HBV-ODN inhibit HBV-CpG-induced IFN-α production and induce the production of IL-10, and lead to immune tolerance, and furthermore we will investigate how the mechanism works. Through this study on the phenomenon and mechanism of negative regulation of the immune system of HBV genome, we can not only enrich the theoretical connotation of immune tolerance, but also provide new pathological targets for the therapy of chronic hepatitis B.

HBV诱导机体免疫耐受是病毒持续性感染的重要原因，而关于HBV如何诱导负向免疫调控进而导致免疫耐受我们知之甚少。前期工作中我们发现HBV基因组来源的非甲基化的CpG寡核苷酸(HBV-CpG)诱导人pDCs大量表达干扰素-α，同时我们发现HBV基因组来源的富含鸟苷的寡核苷酸(HBV-ODN)可特异性地抑制HBV-CpG诱导的干扰素-α表达，我们也发现HBV-ODN具有诱导免疫负调分子IL-10高表达的能力。由此，我们推测HBV-ODN可能是诱导乙型肝炎病毒免疫耐受的重要分子。本课题旨在证明HBV-ODN抑制干扰素-α表达并诱导IL-10的产生，进而导致病毒免疫耐受，并进一步探讨HBV-ODN参与免疫调控和介导免疫耐受的机制。希望通过对HBV基因组参与免疫负调现象的证明和机制的研究，不仅进一步丰富HBV免疫耐受的理论内涵，也为慢性乙型肝炎治疗提供新的靶标。

众所周知乙型肝炎病毒感染后IFN-α表达缺陷，但是临床报道可见其它嗜肝DNA病毒（HSV、HCMV、EBV）感染机体后却可诱导大量IFN-α表达。我们将HBV和其它嗜肝DNA病毒的DNA分别提取后刺激细胞，检测发现HBV的DNA诱导IFN-α能力缺失，而其它嗜肝DNA病毒DNA均能诱导IFN-α表达。进而发现DNA病毒均可通过基因组特异性刺激性CpG寡核苷酸诱导IFN-α表达，同时又可通过基因组特异性的抑制性polyG 寡核苷酸（ODN）抑制CpG所诱导的IFN-α表达，但是CpG与ODN均可活化pDC细胞并上调炎性因子IL-6和TNF-α的表达。通过生物信息学研究发现，HBV与其它嗜肝DNA病毒基因组不同之处与CpG与ODN在不同病毒DNA上比例关系不同有关：HBV基因组上含有低比例的IFN-α活化性基序CpG，同时含有高比例的IFN-α抑制性基序ODN，而其它嗜肝DNA病毒CpG与ODN组成比例恰好相反。由此我们推断HBV通过自身DNA上富含polyG的ODN基序抑制IFN-α表达，这也是第一次揭示polyG ODN基序在DNA病毒中IFN-α免疫调节功能。