Development of a mouse model of peptidoglycan-induced pathology

描述(申请人提供)：肽聚糖(PGN)是一种高度保守的病原体相关分子模式，在革兰氏阳性细菌中含量特别高。人类和非人类灵长类动物在体外通过产生炎性细胞因子和激活血小板来应答PGN，在体内通过全身炎症和弥漫性血管内凝血(DIC)应答。矛盾的是，小鼠和小鼠细胞对PGN的反应最小。我们最近发现，人类和非人类灵长类动物都自然表达与来自各种病原体的PGN交叉反应的IgG抗体，而小鼠则缺乏这些抗体。根据以下观察结果，抗PGN抗体对PGN反应是必不可少的：1.所有受访健康人都表达抗PGN抗体，该抗体能调理PGN。2.PGN激活人血清和血浆中的经典补体途径。3.正常人免疫球蛋白F(ab‘)2片段完整但不支持PGN诱导的人天然免疫细胞产生炎性细胞因子。4.人免疫球蛋白G受体Fc？RIIA在HEK293细胞中的表达可使细胞以人免疫球蛋白依赖的方式结合和吞噬PGN。5.狒狒对PGN体内攻击的反应具有全身炎症和DIC的特征，这种反应与其个体的抗PGN抗体效价直接相关。我们推测，抗PGN-Ig G的存在和水平与由PGN引起的病理有关，从而与革兰氏阳性病原体有关。该项目将通过将含有抗PGN抗体的人免疫球蛋白抗体被动转移到人Fc？RIIA转基因小鼠中，直接测试人中抗-PGN抗体的存在是否参与了PGN的致病效应。我们还将通过使小鼠对PGN免疫，在体内挑战免疫或幼稚的小鼠，并测量炎症迹象，来建立PGN诱导的病理的小鼠模型。小鼠模型将是一个重要的突破，因为它将允许更好地了解对所有革兰氏阳性病原体共有的PGN病原体相关分子模式的反应。

DESCRIPTION (provided by applicant): Peptidoglycan (PGN) is a highly-conserved pathogen-associated molecular pattern that is present in especially high amounts in Gram-positive bacteria. Humans and non-human primates respond to PGN in vitro by production of inflammatory cytokines and platelet activation and in vivo by systemic inflammation and disseminated intravascular coagulation (DIC). Paradoxically, mice and mouse cells show minimal responses to PGN. We recently discovered that both humans and non-human primates naturally express IgG antibodies that cross-react with PGN derived from a variety of pathogens, while mice lack these antibodies. The anti-PGN antibodies were essential for PGN responses, based on the following observations: 1. All surveyed healthy humans express anti-PGN antibodies that opsonize PGN. 2. PGN activates the classical complement pathway in human serum and plasma. 3. Intact but not F(ab')2 fragments of normal human IgG support PGN-triggered inflammatory cytokine production in human innate immune cells. 4. Expression of the human IgG receptor Fc?RIIa in HEK293 cells permitted the cells to bind and phagocytose PGN in a human IgG-dependent manner. 5. Baboons responded to an in vivo challenge of PGN with features of systemic inflammation and DIC; the response directly correlated with their individual titer of anti-PGN IgG antibodies. We hypothesize that the presence and level of anti-PGN IgG is associated with the pathology caused by PGN and thus of Gram-positive pathogens. This project will directly test whether the presence of the anti-PGN IgG in humans contributes to the pathogenic effects of PGN by passive transfer of human IgG containing anti-PGN antibodies to human Fc?RIIA-transgenic mice. We will also generate a mouse model for PGN-induced pathology by making mice immune to PGN, challenging immune or naive mice in vivo, and measuring signs of inflammation. A mouse model will be an important breakthrough as it will permit a better understanding of the response to the PGN pathogen-associated molecular pattern, shared by all Gram-positive pathogens.