Eliciting lung-localized CD4 T cell responses against Mycobacterium tuberculosis in preventive and post-exposure settings

总结 迫切需要有效的疫苗接种战略来对抗结核病（TB）的全球祸害。由于 已知CD 4 T细胞和IFNγ在抗结核免疫中的重要性，目前的疫苗工作集中在 提高大量产生IFNγ的CD 4 T细胞的数量（即，Th 1细胞）。然而，这些努力只是 在动物模型中对结核病的保护作用取得了适度的成功，最近的一项人体功效试验 一种新的候选疫苗未能提供可测量的保护，尽管显着提高了Th 1 反应因此，人们越来越担心靶向Th 1细胞的TB疫苗可能不足以 有效我们和其他人最近发现，完全分化的Th 1细胞的过继转移， 表达高水平的Th 1-促进转录因子T-bet，提供很少或没有保护， 鼠结核病，至少部分是因为他们定位不良的肺实质，感染的主要部位。在 相比之下，分化程度较低的CD 4 T细胞，表达中等水平的T-bet，并与CD 4 T细胞具有相同的特性。 Tfh和中央记忆T细胞，很容易回到M。结核病（Mtb）感染的肺实质， 介导上级保护。然而，重要的是，我们最近也表明，结核分枝杆菌感染本身驱动 Th 1细胞向终末分化而呈非保护性状态。这使疫苗的方法变得复杂， 世界上结核病流行的地区，因为大多数受益于免疫接种的人 已经暴露于结核分枝杆菌或持续感染。本提案的目的是阐明 使保护性CD 4 T细胞群能够进入并维持在肺内的机制 并评价接种期间既存Mtb感染对这些参数的影响 在动物模型和人类临床试验中。在目标1中，我们将确定决定 CD 4 T细胞定位于实质，主要假设T细胞KLRG 1结合N-钙粘蛋白 对血管内皮细胞的作用，从而阻止进入。此外，关键细胞因子和糖脂的作用 还将探讨肉芽肿相关的高内皮微静脉中的相互作用。在目标2中，我们将评估 疫苗依赖性CD 103表达是否用于将保护性CD 4 T细胞保留在实质内， 如果是，这对免疫力是有利还是有害。最后，在目标3中，我们将确定 疫苗剂量对引发保护性、肺归巢CD 4 T细胞应答以及既往Mtb暴露的影响 影响了这种启动。从受感染个体的剂量递增研究中获得临床样本 提供了一个独特的机会，比较人类免疫概况，在小鼠中观察到的，并翻译 将我们在小鼠中的发现转化为人类结核病的可验证假设。拟议的实验将提供 未来设计新型疫苗递送策略的框架，具有诱导和维持肺- 即使在结核病流行地区也能定位T细胞。

SUMMARY An effective vaccination strategy is urgently needed to combat the global scourge of tuberculosis (TB). Due to the known importance of CD4 T cells and IFNγ in immunity against TB, current vaccine efforts are focused on boosting bulk IFNγ-producing CD4 T cell numbers (i.e., Th1 cells). These efforts, however, have been only moderately successful in conferring protection against TB in animal models, and a recent human efficacy trial of a novel candidate vaccine failed to confer measurable protection despite significantly boosting a Th1 response. Thus, there is growing concern that TB vaccines that target Th1 cells may not be adequately effective. We, and others, have recently discovered that adoptive transfer of fully differentiated Th1 cells, expressing high levels of the Th1-promoting transcription factor T-bet, provide little or no protection against murine TB, at least in part because they localize poorly to the lung parenchyma, the primary site of infection. In contrast, less-differentiated CD4 T cells, expressing intermediate levels of T-bet and sharing properties with Tfh and central memory T cells, readily home to the M. tuberculosis (Mtb)-infected lung parenchyma and mediate superior protection. Importantly, however, we have also recently shown that Mtb infection itself drives Th1 cells toward terminal differentiation and a non-protective state. This complicates vaccine approaches in regions of the world in which TB is endemic because most individuals who would benefit from immunization have already been exposed to Mtb or are persistently infected. The goal of this proposal is to elucidate the mechanisms that enable protective CD4 T cell populations to enter and be maintained within the lung parenchyma and to evaluate the influence of pre-existing Mtb infection on these parameters during vaccination in both animal models and human clinical trials. In Aim 1, we will determine the factors that govern the localization of CD4 T cells into the parenchyma, with the prime hypothesis that T cell KLRG1 binds N-cadherin on vascular endothelial cells, thus preventing entry. In addition, the role of key cytokines and glycolipid interactions in granuloma-associated high endothelial venules will also be explored. In Aim 2, we will assess whether vaccine-dependent CD103 expression serves to retain protective CD4 T cells within the parenchyma, and if so, whether this is beneficial or detrimental to immunity. Finally, in Aim 3, we will determine the impact of vaccine dose on priming protective, lung-homing CD4 T cell responses and how previous Mtb exposure influences this priming. The access to clinical samples from dose escalation studies of infected individuals provides a unique opportunity to compare human immune profiles to those observed in mice and to translate our murine findings into testable hypotheses for human TB. The proposed experiments will provide a framework for the future design of novel vaccine delivery strategies with the ability to induce and maintain lung- localizing T cells even in TB endemic regions.