Brucella epitope recognition by CD8+T cells

描述（由申请人提供）：CD 8 +T细胞是重要的，因为它们清除细胞内感染;然而，破坏这些免疫细胞对长期感染有影响。我们将研究羊种布氏杆菌，一种兼性细胞内细菌，如何在免疫反应存在的情况下长期存在于动物体内。我们推测，低数量和无效的CD 8 +T细胞允许持续感染。我们发现BALB/c小鼠感染了B。使用生物发光布鲁氏菌，羊种布鲁氏菌病导致持续>12个月的慢性感染。对这些小鼠的CD 8 +T细胞记忆库的评估揭示了未能维持CD 8 +T细胞记忆表型（LFA 1hi、KLRG 1 lo和CD 127 hi）或多功能细胞因子表达（IL-2、IFN-？和TNF-？）。这些发现表明CD 8 +T细胞表达“耗竭”表型，表明布鲁氏菌逃避了这种已知的清除细胞内病原体的效应机制。此外，布鲁氏菌蛋白TcpB可以在体内抑制表达布鲁氏菌肽的靶细胞的CD 8 +T细胞杀伤。我们的长期目标是通过研究以下目标来了解细菌如何在存在免疫应答的情况下保持在慢性状态：目标1：确定BALB/c小鼠在急性和慢性感染期间的CD 8 +T细胞应答。我们将使用CD 8 + T效应和记忆标记物、转录因子表达、细胞因子产生和体内杀伤来比较急性和慢性感染期间小鼠中CD 8 + T细胞应答的幅度和有效性。影响：我们将确定急性和慢性感染之间的CD 8 +T细胞表型差异，并假设“耗尽”表型和无效的CD 8 + T细胞有助于慢性布鲁氏菌病。目的2：探讨布鲁氏菌诱导的记忆性CD 8 +T细胞的免疫保护能力。我们将研究过继转移的CD 8 +T细胞从急性与慢性感染，以保护首次感染的幼稚动物的能力。影响：我们预期来自急性感染小鼠的CD 8 + T细胞将比来自慢性感染小鼠的细胞更好地保护幼稚小鼠，支持慢性感染的功能性CD 8 + T细胞的丧失。目的3：检测布鲁氏菌TcpB对细胞毒性CD 8 +T细胞的抑制能力。我们将确定TcpB蛋白抑制细胞毒性CD 8 +T细胞杀死感染细胞的能力以及在感染期间体内这种抑制的动力学。影响：我们预期TcpB蛋白通过抑制CD 8 +T细胞杀伤来调节适应性免疫应答，从而允许布鲁氏菌感染细胞的长期存活。我们的研究代表了阐明布鲁氏菌感染如何塑造CD 8 +T细胞效应和记忆反应的关键第一步。这项工作将填补一个严重的空白，在理解的作用，CD 8 +T细胞在布鲁氏菌病，可能参与了该疾病的决议。

DESCRIPTION (provided by applicant): CD8+T cells are significant because they clear intracellular infections; however, subverting these immune cells has implications to long-term infections. We will study how Brucella melitensis, a facultative intracellular bacterium, chronically persists in animals in the presence of an immune response. We hypothesize that low numbers and ineffectual CD8+T cells permit continuing infection. We have found BALB/c mice infected with B. melitensis results in chronic infection lasting >12 months using bioluminescent Brucella. Evaluation of the CD8+T cell memory pool from these mice reveals a failure to maintain the CD8+T cell memory phenotype (LFA1hi, KLRG1lo, and CD127hi), or polyfunctional cytokine expression (IL-2, IFN-? and TNF-?). These findings indicate CD8+T cells express an "exhausted" phenotype suggesting that Brucella evades this known effector mechanism for removing intracellular pathogens. Further, a Brucella protein, TcpB, can inhibit CD8+T cell killing of Brucella peptide expressing target cells in vivo. Our long-term goal is to understand how the bacteria remain in a chronic state in the presence of an immune response, by investigating the following Aims: Aim 1: To determine the CD8+T cell response in BALB/c mice during acute and chronic infection. We will compare the magnitude and effectiveness of CD8+Tcell responses in mice during acute and chronic infection using CD8+Teffector and memory markers, transcription factor expression, cytokine production, and in vivo killing. Impact: We will identify CD8+T cell phenotypic differences between acute and chronic infection and hypothesize an "exhausted" phenotype and ineffectual CD8+Tcells contribute to chronic brucellosis. Aim 2: To determine the protective capacity of Brucella-induced memory CD8+T cells. We will examine the capacity of adoptively transferred CD8+T cells from acute versus chronic infections to protect naive animals from a first infection. Impact: We expect CD8+Tcells from acute infected mice will protect naive mice better than cells from chronically infected mice supporting a loss of functional CD8+Tcells with chronic infection. Aim 3: To determine the inhibitory ability of Brucella TcpB on cytotoxic CD8+T cells. We will determine the ability of the TcpB protein to inhibit cytotoxic CD8+T cell killing of infected cells and the kinetics of this inhibition in vivo during infection. Impact: We expect that TcpB protein modulates the adaptive immune response by inhibiting CD8+T cell killing permitting long-term survival of Brucella-infected cells. Our studies represent a critical first step in elucidating how Brucella infection shapes CD8+T cell effector and memory responses. This work will fill a serious void in understanding the role of CD8+T cells in brucellosis that likely participate in the resolution of tis disease.