Targeting innate immunity to prevent CNS injury in neonatal meningitis

描述(申请人提供)：B组链球菌(GBS)是第一年细菌性脑膜炎的最常见原因，占所有新生儿脑膜炎病例的近50%。新生儿细菌性脑膜炎导致严重的不可逆转的认知和身体残疾，导致终生残疾，尽管进行了高效的抗菌治疗。我们已经成功地建立了体外模型，提供了证据表明，只有在小胶质细胞存在的情况下，经热灭活的GBS或GBS产生的可溶性因子(GBS-F)处理的皮质神经元才会发生细胞死亡。此外，我们定义了信号转导途径的相关组件，表明GBS和GBS-F介导的小胶质细胞激活都需要细胞表面受体Toll样受体2(TLR2)和信号适配器蛋白MyD88的功能表达。最后，我们证实，当小胶质细胞缺乏功能性TLR2或MyDSS时，GBS或GBS-F的反应不会发生神经毒性。我们的初步数据表明，感染革兰氏阳性细菌、CMS天然免疫激活和随后的神经变性之间存在因果关系。这些结果支持针对调节小胶质细胞活动的特定疗法的开发潜力，作为预防细菌性脑膜炎的神经后果的一种手段。这项转化性研究如果呈阳性，将导致治疗剂的开发和临床试验。我们的总体假设是，通过TLR2-MyD88依赖的机制激活CMS中的天然免疫是导致GBS脑膜炎时神经元发生旁观者损伤的原因。我们提出了两个特定的目标，使我们能够在体内测试这一途径的作用：特定的目标1：确定GBS(热灭活)介导的天然免疫激活是否会导致神经元损伤，并依赖于体内功能的TLR2和MyD88。假设：将热灭活的GBS引入新生小鼠的CMS会引起神经元损伤，这种作用将依赖于功能性TLR2和/或MyD88的表达。具体目的2：确定活体脑膜炎的神经元损伤是否依赖于功能上的TLR2和MyD88。假设：在使用标准抗菌治疗的GBS(活体)脑膜炎中，缺乏功能性TLR2或MyD88的动物的神经元损伤将是有限的。

DESCRIPTION (provided by applicant): Group B streptococcus (GBS) is the most common cause of bacterial, meningitis in the first year of life and accounts for nearly 50% of all cases of neonatal meningitis. Bacterial meningitis in newborn infants causes severe irreversible cognitive and physical disability resulting in life long impairment despite highly effective antimicrobial therapy. We have successfully developed in vitro modeling which provides evidence that cortical neurons undergo cell death when treated with heat-inactivated GBS or a soluble factor produced by GBS (GBS-F) only when microglia are present. Furthermore, we defined relevant components of the signal transduction pathway by showing that both GBS and GBS-F mediated activation of microglia require functional expression the cell surface receptor toll-like receptor 2 (TLR2) and the signaling adaptor protein MyD88. Finally, we established that the neurotoxicity in response to GBS or GBS-F failed to occur when microglia lacked functional TLR2 or MyDSS. Our preliminary data suggest a causal relationship between infection with gram-positive bacteria, activation of CMS innate immunity, and subsequent neurodegeneration. These results support the potential for development of specific therapies directed towards modulating microglial activity as a means of preventing the neurological consequences of bacterial meningitis. This translational research, if positive, will then lead to development of a therapeutic agent and clinical trial. Our overall hypothesis is that activation of innate immunity in the CMS through a TLR2-MyD88 dependent mechanism is responsible for the bystander injury that occurs to neurons in the setting of GBS meningitis. We propose two specific aims that will allow us to test the role of this pathway in vivo: Specific Aim 1: To determine if GBS (heat inactivated) mediated activation of innate immunity causes neuronal injury and is dependent on functional TLR2 and MyD88 in vivo. Hypothesis: Heat inactivated GBS introduced into the CMS of neonatal mice will cause neuronal injury and this effect will be dependent on expression of functional TLR2 and or MyD88. Specific Aim 2: To determine if neuronal injury in GBS (live organism) meningitis is dependent upon functional TLR2 and MyD88. Hypothesis: In GBS (live) meningitis treated with standard antimicrobial therapy, neuronal injury will be limited in animals lacking functional TLR2 or MyD88.