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

通过疫苗接种重建抗病毒免疫是一种有吸引力的选择，专门控制慢性乙型肝炎病毒（HBV）感染。为了表征在产生所有HBV抗原的肝脏存在下HBV特异性CD8 T细胞反应，我们建立了1.4HBV smut转基因（tg）系，该系在肝脏中含有复制HBV基因组，产生HBV大/中表面(S)和核心/前核（C/E）抗原，但既不分泌小S颗粒，也不分泌HBV病毒粒子。DNA疫苗可有效诱导核心特异性CD8 T细胞反应，短暂抑制1.4HBV- smuttg小鼠肝脏中的HBV复制。接种1.4HBV-Smut小鼠的肝内特异性CD8 T细胞在表型和细胞因子谱上显示出可重复的变化，这与它们抗病毒活性的丧失（“耗竭”）相一致。该提案旨在阐明在接种1.4HBV-Smut小鼠中引发特异性CD8 T细胞“耗竭”的全身和肝内调节作用。我们将使用1.4HBV-Smut小鼠杂交到定义明确的tg或KO系（缺乏共抑制分子，调节细胞或细胞因子），并接种HBcAg或hbsag编码疫苗。我们将结合特异性疫苗接种与抗病毒药物（替诺福韦®）治疗和/或免疫调节方案，试图维持特异性肝内T细胞的抗病毒表型。我们特别感兴趣的是：(i) wt与tg动物中原代和增强CD8 T细胞反应动力学的表征；（ii） CD8 T细胞和肝细胞表型和细胞因子分泌的变化；（iii） CD8 T细胞的表位特异性。为了选择性地分析肝内效应CD8 T细胞反应，我们将使用过继性转移实验（将接种过的wt或KO小鼠的CD8 T细胞转移到wt或KO 1.4HBV-Smut小鼠中）。这些研究可能有助于合理设计特异性免疫干预方案，以减轻慢性嗜肝病毒感染中CD8 T细胞的功能性“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.