The Role of LPS and Toll-like Receptors in Plague

革兰氏阴性菌鼠疫耶尔森氏菌是鼠疫的病原体。Y.鼠疫菌和一些其它病原体具有修饰其脂多糖（LPS）/脂质A中的酰基链以使Toll样受体4（TLR 4）信号传导最小化的能力。因此，Y.鼠疫杆菌在37 ℃下产生TLR 4活化能力差的四酰基LPS，而在26 ℃下合成有效的六酰基脂质。我们已经证明，在37 ℃下产生的先天免疫应答的逃避是Y。通过产生也在37 ℃下合成六酰化的TLR 4活化LPS的修饰的细菌菌株，改造后的菌株中含有大肠杆菌的脂质A合成酶LpxL。coli中，Y.鼠疫，并具有超过一百万倍的毒性降低。我们的主要假设是，逃避LPS-TLR 4信号是必不可少的致病力的Y。鼠疫杆菌，并且脂质A结构的严格调节是发生这种逃避所必需的。我们建议使用Y。鼠疫菌株产生修饰的LPS，以研究鼠疫杆菌对先天免疫的逃避和激活。我们的模型系统似乎非常适合描述有效的先天免疫机制，对Y。我们的长期目标是确定这种机制和细菌对策。1)Y.鼠疫杆菌表达LpxP，这是一种脂质A生物合成基因，可能是在较低温度下产生六酰基TLR 4活化LPS所必需的。我们建议在37 C研究LpxP表达的调节，因为调节对于毒力是必要的。2)我们还希望研究LPS-TLR 4信号的逃避在Y染色体进化中的作用。鼠疫杆菌从其最接近的祖先Y.假结核（Y. ptb），只会引致轻微肠胃炎。有趣的是，Y。ptb具有LpxL基因。建议对Y. ptb LpxL函数，这将包括Y的表达。在Y.鼠疫菌的LPS活性和结构。3)初步结果表明，白细胞介素-1（IL-1）的释放和信号转导在清除Y. pestis-LpxL，高于TNF和I型IFN。我们将分析Y.鼠疫杆菌在体内外诱导IL-1并受IL-1控制。

The gram-negative bacterium Yersinia pestis is the causative agent of plague. Y. pestis and some other pathogens have the ability to modify the acyl chains in their lipopolysaccharide (LPS) /lipid A in order to minimize Toll-like receptor 4 (TLR4) signaling. Consequently, Y. pestis produces a tetra-acyl LPS with poor TLR4-activating ability at 37C, while synthesizing a potent hexa-acyl lipid at 26C. We have shown that the resulting evasion of innate immune responses at 37C is necessary for Y. pestis virulence via the peripheral route, by generating a modified bacterial strain synthesizing a hexa-acylated TLR4-activating LPS also at 37C. The modified strain contained LpxL, a lipid A biosynthesis enzyme from E. coli, that is absent in Y. pestis, and has more than a million-fold reduced virulence. Our main hypothesis is that evasion of LPS-TLR4 signaling is essential for the virulence of Y. pestis, and that a tight regulation of lipid A structure is necessary for this evasion to occur. We propose to use Y. pestis strains that generate modified LPS to study evasion and activation of innate immunity by the plague bacillus. Our model system appears well suited to describe efficient innate immune mechanisms against Y. pestis, and our long-term goal is to define such mechanisms and bacterial countermeasures. 1) Y. pestis expresses LpxP, a lipid A biosynthesis gene that likely is necessary for the production of a hexa-acyl TLR4-activating LPS at lower temperatures. We propose to study regulation of LpxP expression at 37C, as regulation appears necessary for virulence. 2) We also wish to study the role of evasion of LPS-TLR4 signaling in the evolution of Y. pestis to a highly virulent pathogen from its closest ancestor, Y. pseudotuberculosis (Y. ptb), which only may cause a mild gastroenteritis. Interestingly, Y. ptb harbors an LpxL gene. Our proposal suggests studies of Y. ptb LpxL function, this will include expression of Y. ptb LpxL in Y. pestis, and study LPS activity and structures. 3) Preliminary results indicate that interleukin-1 (IL-1) release and signaling is effective in clearing infection with Y. pestis-LpxL, more so than TNF and type I IFN. We will analyze mechanisms by which Y. pestis induces and is controlled by IL-1, in vitro and in vivo.