Role of RIP2 in Biodefense Against Listeria Infection

描述(申请人提供)：这项建议的长期目标是深入了解受体相互作用蛋白2(RIP2)在宿主对单核细胞增多性李斯特菌感染的生物防御中的作用机制。RIP2是丝氨酸/苏氨酸(Ser/Thr)激酶RIP家族的成员。它与NOD受体家族蛋白激活的信号转导通路有关，NOD受体家族蛋白是细胞内病原体的潜在受体。我们最近创造了缺乏RIP2基因的基因敲除小鼠，并发现RIP2-/-小鼠防御单核细胞增多性李斯特菌感染的能力严重受损。我们的初步结果还表明，RIP2-/-巨噬细胞已经失去了对来自革兰氏阳性细菌的肽聚糖的最小免疫刺激亚基--胞壁二肽(MDP)的反应能力。此外，RIP2-/-T辅助细胞1(THL)和自然杀伤细胞(NK)在IL-12刺激下减少了干扰素-γ(干扰素-γ)的产生。我们推测RIP2可能参与多种信号和细胞事件，以协调宿主对病原体感染的生物防御中的先天和获得性免疫反应。我们建议通过实验来研究RIP2介导的信号转导途径，并确定RIP2在病原体感染期间的免疫反应中的作用。首先，我们假设RIP2参与了MDP诱导的天然免疫反应的激活。我们将确定RIP2在巨噬细胞对MDP刺激的信号转导和细胞因子产生中的作用和机制。第二，我们假设RIP2通过调节IL-12诱导的STAT4激活和干扰素-γ的产生而参与Th1的分化。我们将首先确认RIP2-/-THL细胞的内在缺陷，然后探索RIP2可能参与IL-12诱导的STAT4激活和干扰素产生的潜在信号事件。第三，我们假设RIP2通过影响先天免疫反应和获得性免疫反应参与宿主对微生物感染的防御。我们将测定RIP2-/-小鼠对革兰氏阳性和革兰氏阴性细胞外和细胞内细菌的敏感性，以了解RIP2在确定病原体特异性方面的作用。我们还将使用单核细胞增多性乳杆菌感染RIP2-/-小鼠作为模型，以确定RIP2在针对微生物感染的先天和获得性免疫反应中的贡献。我们相信，从这些研究中获得的见解将为病原体识别和先天性免疫系统与获得性免疫系统之间的协调提供新的知识，并为预防和治疗许多人类传染病提供新的免疫干预途径。

DESCRIPTION (provided by applicant): The long-term objective of this proposal is to gain insight into the mechanisms of action of the receptor interacting protein 2 (RIP2) in host biodefense against Listeria monocytogenes infection. RIP2 is a member of the RIP family of serine/threonine (Ser/Thr) kinases. It has been implicated in the signal transduction pathways activated by the Nod receptor family proteins, potential receptors for intracellular pathogens. We recently created knockout mice lacking the RIP2 gene, and found that RIP2-/- mice are severely impaired in their ability to defend against infection with L. monocytogenes. Our preliminary results also indicated that RIP2-/- macrophages have lost their ability to respond to muramyl dipeptide (MDP), the minimal immunostimulatory subunit of peptidoglycan from gram positive bacteria. In addition, RIP2-/- T helper 1 (Thl) and natural killer (NK) cells have reduced interferon gamma (IFN-gamma) production upon IL-12 stimulation. We hypothesize that RIP2 may be involved in multiple signaling and cellular events to coordinate innate and adaptive immune responses in host biodefense against pathogen infection. We propose experiments to investigate RIP2- mediated signal transduction pathways and to determine the in vivo role of RIP2 in immune responses during pathogen infections. First, we hypothesize that RIP2 is involved in MDP-induced activation of innate immune responses. We will determine the role and the mechanism of RIP2 in mediating signal transduction and cytokine production by macrophages in response to MDP stimulation. Second, we hypothesize that RIP2 is involved in Thl differentiation by modulating the activity of IL-12-induced STAT4 activation and interferon gamma (IFN-gamma) production. We will first confirm the intrinsic defects of RIP2-/- Thl cells, and then explore potential signaling events where RIP2 might be involved in IL-12-induced STAT4 activation and interferon IFN-(, production. Third, we hypothesize that RIP2 is involved in host defense against microbial infections by affecting both innate and adaptive immune responses. We will determine the susceptibility of RIP2-/- mice to gram-positive and gram-negative extracellular and intracellular bacteria to understand the role of RIP2 in determining the pathogen specificity. We will also use L. monocytogenes infection of RIP2-/- mice as a model to determine the contribution of RIP2 in innate and adaptive immune responses against microbial infections. We believe that the insights obtained from these studies will provide new knowledge about pathogen recognition and coordination between innate and adaptive immune systems, and suggest new avenues of immunologic intervention to prevent and treat many human infectious diseases.