Strategies to enhance vaccine-primed T cell immunity against HCV

摘要--项目2 该计划的一个中心假设是体液和细胞适应性免疫反应协同控制 丙型肝炎病毒感染。项目2的目标是开发一种引起泛基因型别的丙型肝炎疫苗成分 CD4+和CD8+T细胞记忆。当与一种旨在引起广泛中和的疫苗成分结合时 抗体(项目1)，我们希望产生等于或超过保护性适应性反应的免疫力 通过急性丙型肝炎病毒感染的自发解决而自然获得。 一些观察表明，疫苗诱导的T细胞免疫将是保护的关键。初始控制 急性丙型肝炎病毒复制的发生与功能性T细胞反应的开始在时间上有关。感染问题得到解决 只有在这种反应持续的情况下。耐久的T细胞记忆会形成，并可能阻止在重新启动时的持久性 感染。抗体介导的免疫黑猩猩再次感染前CD8+或CD4+T细胞的耗竭 引起长期或持续的感染。最后，针对异源丙型肝炎病毒基因型别的保护作用 在免疫黑猩猩中观察到，但可能失败，这表明丙型肝炎病毒遗传多样性限制了保护性T细胞 记忆。 疫苗开发的两大挑战是(I)丙型肝炎病毒基因类型的巨大遗传多样性和 (2)缺乏评估疫苗效力的动物挑战模型。为了提供广泛的T细胞免疫， 由来自丙型肝炎病毒GT1a、1b、GT2和GT3的保守的非结构蛋白组成的四价疫苗 将对序列进行评估。NS抗原将通过计算从大量可用的 丙型肝炎病毒序列，导致嵌合体不利于包含不常见的氨基酸，否则会 引起产量较低的疫苗或病毒株特异性T细胞反应。马赛克与天然马赛克难以区分 丙型肝炎病毒蛋白的序列和处理，为人类白细胞抗原呈递给T细胞。马赛克转基因将被运送到 通过两种病毒载体，Ad48(一种罕见的人类亚型)和MVA，可以翻译成人类疫苗。 一个关键的悬而未决的问题是，疫苗是否会产生组织驻留的记忆T细胞，以及它们是否会 相当于感染自发消退引起的感染。我们将进行第一次描述 来自黑猩猩的驻留在肝脏的CD4+和CD8+T细胞群自发地解决了丙型肝炎病毒感染。 这项分析将使用在暂停之前由NIH支持收集的冷冻保存的肝脏单个核细胞 黑猩猩在生物医学研究中的应用。衡量质量的关键指标(广度、频率和功能)将是 四价嵌合体猕猴体内组织驻留T细胞的建立和比较 疫苗。在与项目3的合作中，T细胞也将通过CITE-SEQ进行比较，以提供完整的细胞 蛋白质和转录组的测量。这些比较有望提供一种替代衡量标准 在没有病毒攻击模型的情况下疫苗激活的T细胞的有效性。

ABSTRACT – PROJECT 2 A central hypothesis of this Program is that humoral and cellular adaptive immune responses synergize to control HCV infection. The objective of Project 2 is to develop an HCV vaccine component that elicits pan-genotypic CD4+ and CD8+ T cell memory. When combined with a vaccine component designed to elicit broadly neutralizing antibodies (Project 1), we expect to generate immunity equaling or exceeding protective adaptive responses acquired naturally by spontaneous resolution of acute HCV infection. Several observations indicate that vaccine-induced T cell immunity will be essential for protection. Initial control of acute HCV replication is temporally associated with onset of a functional T cell response. Infections resolve only if this response is sustained. Durable T cell memory develops and may prevent persistence upon re- infection. Antibody-mediated depletion of CD8+ or CD4+ T cells from immune chimpanzees before re-infection caused prolonged or persistent infection. Finally, protection against heterologous HCV genotypes has been observed in immune chimpanzees, but can fail suggesting that HCV genetic diversity limits protective T cell memory. Two major challenges for vaccine development are (i) the tremendous genetic diversity of HCV genotypes and (ii) the lack of an animal challenge model to assess vaccine efficacy. To provide broad T cell immunity, a tetravalent vaccine comprised of conserved HCV non-structural proteins from HCV gt1a, 1b, gt2, and gt3 sequences will be assessed. NS antigens will be designed computationally from a large number of available HCV sequences, resulting in Mosaics that disfavor inclusion of uncommon amino acids that would otherwise elicit less productive vaccine- or virus strain-specific T cell responses. Mosaics are indistinguishable from natural HCV proteins in sequence and processing for HLA presentation to T cells. Mosaic transgenes will be delivered by two viral vectors, Ad48 (a rare human subtype) and MVA, that can be translated for human vaccination. A key unanswered question is whether vaccines generate tissue-resident memory T cells, and whether they are equivalent to those elicited by spontaneous resolution of infection. We will undertake the first characterization of liver-resident CD4+ and CD8+ T cell populations from chimpanzees that spontaneously resolved HCV infection. This analysis will use cryopreserved liver mononuclear cells collected with NIH support before the moratorium on chimpanzee use in biomedical research. Key measures of quality (breadth, frequency and function) will be established, and compared with tissue-resident T cells primed in rhesus macaques with the tetravalent Mosaic vaccine. In co-operation with Project 3, T cells will also be compared by Cite-Seq to provide integrated cellular protein and transcriptome measurements. These comparisons are expected to provide a surrogate measure of efficacy for vaccine-primed T cells in the absence of a virus challenge model.