Exploring immune modulating strategies to restore antiviral effector functions of intrahepatic CD8 T cells

通过接种疫苗重建抗病毒免疫是特异性控制慢性乙肝病毒感染的一个有吸引力的选择。我们建立了1.4HBVSmut转基因(TG)品系，该品系在肝脏中含有可复制的HBV基因组，可产生HBV大/中表面(S)和核心/前C(C/E)抗原，但不分泌小S颗粒和HBV病毒粒子。DNA疫苗有效地诱导核心(但不是S)特异性的CD8T细胞反应，暂时抑制1.4HBVSMUT转基因小鼠肝脏中的乙肝病毒复制。在接种1.4HBV-Smut TG小鼠的肝脏内，特异性CD8T细胞的表型和细胞因子谱显示出可重复的变化，这与它们的抗病毒活性丧失(“衰竭”)相一致。该提案旨在阐明导致接种1.4HBVSmut TG小鼠的特定CD8 T细胞“耗尽”的系统和肝内调节效应。我们将使用1.4只HBVSMUT转基因小鼠与明确定义的TG或KO系(缺乏共抑制分子、调节细胞或细胞因子)杂交，并接种HBcAg或HBs Ag编码的疫苗。我们将把特定疫苗接种与抗病毒药物(替诺福韦®)治疗和/或免疫调节方案相结合，试图在特定的肝内T细胞中保持抗病毒表型。我们特别感兴趣的是：(I)wt和tg动物中原始和增强的CD8T细胞反应的动力学特征；(Ii)CD8T细胞和肝细胞表型和细胞因子分泌的变化；以及(Iii)CD8T细胞的表位特异性。为了选择性地分析肝内效应分子CD8T细胞的反应，我们将使用过继转移实验(将接种疫苗的wt或ko小鼠的CD8T细胞转移到wt或ko 1.4HBVSmut Tg小鼠)。这些研究可能有助于合理设计特定的免疫干预方案，以减轻慢性嗜肝病毒感染时CD8T细胞的功能耗竭。

Reconstitution of antiviral immunity by vaccination is an attractive option to specifically control chronic hepatitis B virus (HBV) infection. To characterize HBV-specific CD8 T cell responses in the presence of a liver that produces all HBV antigens, we established the 1.4HBV-Smut transgenic (tg) line that harbours a replicating HBV genome in the liver, produces HBV large/middle surface (S) and core/precore (C/E) antigens but secretes neither small S particles, nor HBV virions. DNA vaccines efficiently induce core- (but not S-) specific CD8 T cell responses that transiently suppress HBV replication in the liver of 1.4HBV-Smut tg mice. Intrahepatic, specific CD8 T cells in vaccinated 1.4HBV-Smut tg mice show reproducible changes in their phenotype and cytokine profile that coincide with their loss of antiviral activity (‘exhaustion’). The proposal aims to elucidate systemic and intrahepatic regulatory effects that set off ´exhaustion´ of specific CD8 T cells in vaccinated 1.4HBV-Smut tg mice. We will use 1.4HBV-Smut tg mice crossed to well-defined tg or KO lines (deficient for coinhibitory molecules, regulator cells or cytokines) and vaccinated with HBcAg- or HBsAg-encoding vaccines. We will combine specific vaccination with antiviral drug (Tenofovir®) treatment and/or immune modulating protocols in an attempt to maintain an antiviral phenotype in the specific, intrahepatic T cells. We are in particular interested in: (i) the characterization of the kinetics of primary and boosted CD8 T cell responses in wt versus tg animals; (ii) changes in phenotype and cytokine secretion of CD8 T cells and hepatocytes; and (iii) epitope specificities of CD8 T cells. To selectively analyze intrahepatic effector CD8 T cell responses, we will use adoptive transfer experiments (CD8 T cells from vaccinated wt or KO mice transferred into wt or KO 1.4HBV-Smut tg mice). These studies may help to rationally design specific immune intervention protocols that attenuate the functional ‘exhaustion’ of CD8 T cells in chronic infection with hepatotropic viruses.