Cytokine induction by Gram-positive bacteria

革兰氏阳性菌和革兰氏阴性菌引起的炎症反应在临床上是相似的。虽然革兰氏阴性内毒素(脂多糖)的结构/功能关系已经建立，但对于同样重要的革兰氏阳性病原体，这类研究还缺乏。我们最近从金黄色葡萄球菌中分离到脂磷壁酸(LTA)，并对其结构进行了分析，结果表明LTA是一种通过TLR-2受体发挥作用的免疫激活剂。然而，LTA引起的炎症反应范围比内毒素更窄。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对小鼠来说是有毒的。工作计划是：比较TLR-2激动剂如LTA(各种物种)、念珠菌甘露聚糖、疏螺旋体抗原、阿拉伯甘露聚糖脂和MALP-2从血液中释放的细胞因子，以检查缺乏IL-12诱导是否代表TLR-2激动剂的一般特征。原代小鼠巨噬细胞的反应应与人类单核细胞进行比较。然后，将寻找转录激活物的IL-12启动子基序，以寻找内毒素和LTA信号之间的可能差异。在前人工作的基础上，我们将测试肌多肽、商业超抗原和细菌DNA对IFNG的独立或协同诱导作用。通过分级分离/溶剂萃取/层析的方法对该生物活性进行纯化和鉴定是首要目标。已确定的增效成分将与LTA一起应用于小鼠，以建立类似于内毒素休克或氨基半乳糖/脂多糖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.