Targeting innate immunity to prevent CNS injury in neonatal meningitis

描述（由申请人提供）：B群链球菌（GBS）是生命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会导致严重的不可逆转的认知和身体残疾，导致终生损害，尽管进行了高效的抗菌治疗。我们已经成功地开发了体外模型，该模型提供了证据，表明当热灭活GBS或GBS产生的可溶性因子（GBS- f）仅在小胶质细胞存在时处理皮质神经元时，细胞会死亡。此外，我们通过表明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）和信号接头蛋白MyD88的功能性表达来定义信号转导途径的相关成分。最后，我们确定，当小胶质细胞缺乏功能性TLR2或MyDSS时，GBS或GBS- f的神经毒性反应不会发生。我们的初步数据表明革兰氏阳性菌感染、CMS先天免疫激活和随后的神经退行性变之间存在因果关系。这些结果支持开发针对调节小胶质细胞活动的特异性治疗方法，作为预防细菌性脑膜炎神经系统后果的一种手段。这项转化研究如果取得积极进展，将导致治疗剂和临床试验的开发。我们的总体假设是，通过TLR2-MyD88依赖机制激活CMS中的先天免疫是导致GBS脑膜炎背景下发生的神经元旁观者损伤的原因。我们提出了两个特定目的，这将使我们能够在体内测试该途径的作用：特定目的1：确定GBS（热失活）介导的先天免疫激活是否会导致神经元损伤，并依赖于体内的功能性TLR2和MyD88。假设：将热灭活GBS引入新生小鼠CMS会引起神经元损伤，这种影响依赖于功能性TLR2和/或MyD88的表达。特异性目的2：确定GBS（活生物体）脑膜炎的神经元损伤是否依赖于功能性TLR2和MyD88。假设：在使用标准抗菌药物治疗的GBS（活）脑膜炎中，缺乏功能性TLR2或MyD88的动物的神经元损伤将受到限制。

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.