Cytokine induction by Gram-positive bacteria

革兰氏阳性菌和革兰氏阴性菌诱导的炎症反应在临床上相似。虽然建立了革兰氏阴性内毒素（脂多糖，LPS）的结构/功能关系，但对于同样重要的革兰氏阳性病原体，缺乏此类研究。我们最近从金黄色葡萄球菌中分离出脂磷壁酸（LTA），分析了其结构，并表明LTA是通过TLR-2受体起作用的免疫激活剂。然而，LTA诱导的炎症反应谱比LPS更窄。为了解释LTA较低的动物毒性，我们将其归因于缺乏IL-12和随后的IFNg诱导。事实上，当IFNg被取代时，LTA在小鼠中变得有毒。工作方案为：将比较TLR-2激动剂如LTA（各种物种）、甘露假丝酵母、疏螺旋体抗原、脂阿拉伯甘露聚糖和MALP-2从血液中释放的细胞因子，以检查IL-12诱导的缺乏是否代表TLR-2激动剂的一般特征。原代小鼠巨噬细胞的反应应与人单核细胞进行比较。然后，将搜索转录激活因子的IL-12启动子基序，以确定LPS和LTA信号传导之间的推定差异。基于先前的工作，将测试由胞肽、商业超抗原和细菌DNA独立或协同诱导IFNg。通过分级分离/溶剂萃取/色谱法纯化和鉴定这种生物活性是主要目标。将鉴定的协同组分与LTA一起给予小鼠，以建立类似于LPS休克或半乳糖胺/LPS肝损伤的革兰氏阳性动物模型。将研究这种动物模型的基本特征（剂量依赖性、细胞因子模式、组织病理学）。

Gram-positive and Gram-negative bacteria induce inflammatory reactions which are clinically similar. While structure/ function relationships for Gram-negative endotoxins (lipopoly- saccharides, LPS) are established, for the equally important Gram-positive pathogens such studies are lacking. We have recently isolated the lipoteichoic acid (LTA) from Staphylo- coccus aureus, analyzed the structure and shown that LTA is the an immune activator operating via the tlr-2 receptor. LTA however, induces a more narrow spectrum of inflammatory reactions than LPS. To explain the lower animal toxicity of LTA, we attributed this to a lack of IL-12 and subsequent IFNg induction. Indeed, LTA became toxic in mice when IFNg was substituted. Work program is: The cytokine release from blood by tlr-2 agonists such as LTA (various species), candida mannans, Borrelia antigens, lipoarabinomannan and MALP-2, will be compared to check whether the lack of IL-12 induction represents a general characteristics of tlr-2 agonists. The response of primary mouse macrophages shall be compared to human monocytes. Then, the IL-12 promoter motifs for transcriptional activators will be searched for putative differences between LPS and LTA signaling. Based on previous work, the independent or synergistic induction of IFNg by muropeptides, commercial superantigens and bacterial DNA will be tested. Purification and identification by fractionation/solvent extraction/chroma- tography of this bioactivity is primary goal. The identified synergistic component will be given to mice together with LTA in order to establish a Gram-positive animal model analogous to LPS shock or galactosamine/LPS liver injury. The basic characteristics of such an animal model (dose-dependence, cytokine pattern, histopathology) will be studied.