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

摘要 迫切需要一种有效的疫苗接种战略来抗击结核病的全球祸害。由于 已知的CD4T细胞和干扰素γ在抗结核免疫中的重要性，目前的疫苗努力集中在 增加大量产生干扰素γ的CD4T细胞数量(即Th1细胞)。然而，这些努力只是 在动物模型和最近的一项人类功效试验中，对结核病的保护取得了一定的成功 一种新的候选疫苗未能提供可测量的保护，尽管显著提高了Th1 回应。因此，人们越来越担心针对Th1细胞的结核病疫苗可能不够充分。 有效。我们和其他人最近发现，完全分化的Th1细胞的过继转移， 高水平表达Th1促进转录因子T-bet，对 小鼠结核病，至少部分是因为它们不能很好地定位于肺实质，而肺实质是感染的主要部位。在……里面 相比之下，分化较低的CD4T细胞，表达中等水平的T-bet，并具有与 TFH和中央记忆T细胞，很容易成为结核分枝杆菌(Mtb)感染的肺实质的宿主，以及 调解高级保护。然而，重要的是，我们最近也表明，结核分枝杆菌感染本身会推动 Th1细胞向终末分化，处于非保护性状态。这使疫苗接种方法变得复杂 世界上结核病流行的地区，因为大多数将从免疫中受益的人 已经接触过结核分枝杆菌或持续感染。这项提议的目的是澄清 使保护性的CD4T细胞群进入肺内并在肺内维持的机制 在接种过程中，评估预先存在的结核分枝杆菌感染对这些参数的影响 在动物模型和人类临床试验中都是如此。在目标1中，我们将确定支配 T细胞KLRG1结合N-钙粘附素的基本假设下，CD4T细胞在实质内的定位 在血管内皮细胞上，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小静脉之间的相互作用。在目标2中，我们将评估 疫苗依赖的CD103表达是否有助于将保护性的CD4T细胞保留在实质内， 如果是这样，这对免疫力是有利的还是有害的。最后，在目标3中，我们将确定 疫苗剂量对免疫保护性、肺归巢的CD4T细胞反应以及以前接触结核分枝杆菌的影响 会影响这个引爆。从感染者剂量递增研究中获取临床样本 提供了一个独特的机会来比较人类免疫图谱与在老鼠身上观察到的免疫图谱，并将其翻译成 我们的小鼠发现了人类结核病的可验证假说。拟议的实验将提供一种 未来设计新的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要定位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.