Mechanisms of Prostaglandin E2 induction by Francisella tularensis

描述（由申请人提供）：病原菌和它们的宿主已经进行了数百万年的双向对话。宿主已经发展了复杂的机制来保护自己免受病原体的侵害，而病原菌也已经发展了改变和逃避宿主免疫反应的机制。土拉热弗朗西丝菌是一种兼性胞内微生物，是土拉菌病的病原体。由于该生物体的感染剂量低，发病率和死亡率高，而且美国和苏联都将其武器化，因此它被指定为A类生物恐怖主义制剂。因此，迫切需要了解生物体的生物学以及F。土拉热会改变宿主的免疫系统。最近的研究清楚地表明，F。土拉菌能够调节宿主的免疫应答，并创造有利于其在宿主中存活的环境。然而，我们对F。土拉热会改变宿主的免疫系统F.土拉热通过抑制细胞因子和T细胞应答而明显改变免疫应答。F.土拉热菌感染导致受感染的抗原呈递细胞（APC）产生前列腺素E2（PGE2）。由APC产生的PGE2抑制T细胞的增殖和活化。此外，在呼吸性土拉菌病期间PGE2的延长诱导抑制了稳健的适应性T细胞应答的产生，因此显著延迟了生物体的清除。在初步研究结果中，筛选了Francisella转座子突变体文库，并鉴定了20个与PGE2诱导相关的候选基因。该提案的第一个目标是确定负责诱导PGE2的效应分子。这将通过利用候选基因的非极性无标记干净缺失以及候选基因的真核表达来完成。第二个目标是确定负责识别F.土拉菌产物。这将通过使用酵母双杂交筛选来实现。这种分子相互作用的鉴定和表征可以想象地用于抗微生物化疗靶点。

DESCRIPTION (provided by applicant): Pathogenic bacteria and their hosts have had a two way conversation for millions of years. The host has developed sophisticated mechanisms to protect itself against pathogens and in turn pathogenic bacteria have developed mechanisms to alter and evade the host immune response. Francisella tularensis is a facultative intracellular organism and the causative agent of tularemia. Due to the organism's low infective dose, high morbidity and mortality, and the fact that it was weaponized by both the U.S.A. and the USSR it has been designated a category A bioterrorism agent. Consequently, there is an urgent need to understand the biology of the organism and the underlying molecular and cellular mechanisms by which F. tularensis alters the immune system of its hosts. Recent studies clearly demonstrate that F. tularensis is able to modulate the host immune response and create an environment in favor of its survival in the host. However, we have only sketchy knowledge about the mechanisms by which F. tularensis alters the host immune system. F. tularensis clearly alters the immune response by inhibiting cytokine and T cell responses. F. tularensis infection results in prostaglandin E2 (PGE2) production by infected antigen presenting cells (APC). PGE2 produced by APC inhibits the proliferation and activation of T cells. Furthermore, the prolonged induction of PGE2 during respiratory tularemia dampens the generation of a robust adaptive T cell response and as a result, significantly delays the clearance of the organism. In preliminary findings a Francisella transposon mutant library was screened and 20 candidate genes associated with induction of PGE2 were identified. The first goal of this proposal will identify the effector molecule responsible for the induction of PGE2. This will be done by utilizing nonpolar markerless clean deletions of candidate genes, as well as eukaryotic expression of candidate genes. The second goal will be to determine the eukaryotic sensor responsible for identifying the F. tularensis product. This will be accomplished with the use of a yeast two hybrid screen. The identification and characterization of this molecular interaction could be conceivably exploited for antimicrobial chemotherapy targets.