Th9 cells and protective TB immunity

产生-γ的Th1细胞已被广泛研究用于开发抗结核分枝杆菌（Mtb）感染的新型疫苗和治疗方法。然而，最近的研究表明，单独的mtb特异性Th1细胞不能预测对结核病（TB）的保护作用。因此，尽管控制结核分枝杆菌复制需要Th1细胞，但可能需要其他类型的免疫细胞来预防感染和根除细菌。我们最近发现产生il -9的CD4+ T细胞（Th9）的一个亚群可以介导对结核杆菌感染的保护性免疫。Th9细胞可通过TGF-β和IL-4从naïve CD4+ T细胞分化而来，在抗肿瘤免疫和过敏反应相关免疫中发挥重要作用。然而，Th9细胞在结核分枝杆菌感染中的作用在很大程度上仍然未知。当我们分析接种卡介苗的健康志愿者和潜伏性结核感染（LTBI）患者的CD4+ T细胞的转录组时，我们发现了Th9细胞在结核病免疫中的作用。CD4+ T细胞IL-9 mRNA在卡介苗接种和LTBI后升高的基因中居首位。仅在LTBI患者和口服（PO）卡介苗疫苗接种者中，观察到感染性结核刺激后支气管肺泡灌洗（BAL）细胞IL-9产生的显著增加，表明诱导了结核特异性Th9记忆反应。为了检验Th9细胞是否介导细胞内Mtb杀伤，我们从ESAT6-TCR转基因小鼠中分化Mtb特异性Th9细胞，并将这些Th9细胞与感染Mtb的小鼠巨噬细胞共培养。巨噬细胞与Th9细胞相互作用后，胞内分枝杆菌生长明显减少。此外，中和IL-9可消除Th9细胞的抑制作用，而单独添加重组IL-9可抑制细胞内细菌的生长。此外，将Mtb特异性Th9细胞过继转移到同源RAG1/2-/-小鼠体内可抑制Mtb的生长。此外，我们发现在缺乏MCPIP1（一种影响T细胞活化的新的rna结合蛋白）的小鼠中，IL-9增加，Mtb生长减少。Th9细胞中MCPIP1的缺失导致IL-9的产生在再刺激时显著增加。基于我们的初步发现，我们假设mtb特异性Th9细胞代表CD4+ T细胞的一个独特亚群，对保护性结核病免疫很重要。诱导结核分枝杆菌特异性Th9细胞的策略可用于开发更有效的结核疫苗和/或免疫疗法。我们提出了三个目标来验证这一新的假设：目的1确定mtb特异性Th9细胞对保护性TB免疫的影响；目的2确定IL-9在基因工程小鼠疫苗诱导的抗结核感染保护中的作用，目的3确定IL-9在卡介苗接种个体PBMC和BAL细胞中的来源，以及Mtb特异性Th9细胞介导的人巨噬细胞细菌杀伤机制。这些研究将对提高我们对抗结核分枝杆菌感染的宿主保护性免疫机制的理解产生重大影响，并为靶向Mtb特异性Th9细胞作为开发更有效的结核病疫苗和/或抗结核分枝杆菌感染免疫疗法的新策略提供依据。

-γ-producing Th1 cells have been extensively studied for development of novel vaccines and therapeutics against Mycobacterium tuberculosis (Mtb) infection. However, recent studies demonstrate that Mtb-specific Th1 cells alone do not predict protection against tuberculosis (TB). Therefore, although Th1 cells are required for controlling Mtb replication, other types of immune cells may be needed to prevent infection and eradicate the bacteria. We recently found that a subset of IL-9-producing CD4+ T cells (Th9) can mediate protective immunity against Mtb infection. Th9 cells can be differentiated from naïve CD4+ T cells with TGF-β and IL-4, and play important roles in antitumor immunity and immunity related to allergic reactions. The role of Th9 cells in Mtb infection, however, remain largely unknown. We discovered a role for Th9 cells in TB immunity when we analyzed the transcriptomes in CD4+ T cells from healthy volunteers vaccinated with BCG and from people with latent TB infection (LTBI). IL-9 mRNA in CD4+ T cells topped the list of genes increased after BCG vaccination and LTBI. A significant increase in IL-9 production by bronchoalveolar lavage (BAL) cells after stimulation with infectious Mtb was observed only in LTBI patients and people vaccinated with oral (PO) BCG, indicating induction of Mtb-specific Th9 memory responses. To test whether Th9 cells mediate intracellular Mtb killing, we differentiated Mtb-specific Th9 cells from ESAT6-TCR transgenic mice and co-cultured these Th9 cells with Mtb-infected murine macrophages. Intracellular mycobacterial growth was significantly reduced in macrophages after interacting with Th9 cells. Moreover, neutralizing IL-9 abolished the inhibitory effects of Th9 cells, while addition of recombinant IL-9 alone inhibited intracellular bacterial growth. Furthermore, adoptive transfer of Mtb-specific Th9 cells into syngeneic RAG1/2-/- mice suppresses Mtb growth in vivo. In addition, we found that IL-9 was increased and Mtb growth decreased in mice deficient in MCPIP1, a new RNA-binding protein affecting T cell activation. Deletion of MCPIP1 in Th9 cells resulted in a significantly enhanced IL-9 production upon restimulation. Based on our preliminary findings, we hypothesize that Mtb-specific Th9 cells represent a distinct subset of CD4+ T cells important for protective TB immunity. Strategies inducing Mtb- specific Th9 cells could be used to develop more effective TB vaccines and/or immunotherapies. We propose three aims to test this novel hypothesis: Aim 1 to determine the effects of Mtb-specific Th9 cells on protective TB immunity; Aim 2 to define the roles of IL-9 in vaccine-induced protection against Mtb infection using genetically engineered mice, and Aim 3 to identify the source for IL-9 in PBMC and BAL cells from BCG vaccinated individuals, and the mechanisms of Mtb-specific Th9 cell-mediated bacterial killing in human macrophages. These studies will have a significant impact on improving our understanding of host protective immune mechanisms against Mtb infection, and provide the rationale for targeting Mtb-specific Th9 cells as a new strategy for more effective TB vaccines and/or immunotherapies against Mtb infection.