Berezow Alex B, Ernst Robert K, Coats Stephen R, Braham Pamela H, Karimi-Naser Lisa M, Darveau Richard P
Department of Microbiology, University of Washington School of Medicine, Seattle, WA 98195, USA.
Microb Pathog. 2009 Aug;47(2):68-77. doi: 10.1016/j.micpath.2009.04.015. Epub 2009 May 19.
Lipid A structural modifications can substantially impact the host's inflammatory response to bacterial LPS. Bacteroides fragilis, an opportunistic pathogen associated with life-threatening sepsis and intra-abdominal abscess formation, and Bacteroides thetaiotaomicron, a symbiont pivotal for proper host intestinal tissue development, both produce an immunostimulatory LPS comprised of penta-acylated lipid A. Under defined conditions, Porphyromonas gingivalis, an oral pathogen associated with periodontitis, also produces an LPS bearing a penta-acylated lipid A. However, this LPS preparation is 100-1000 times less potent than Bacteroides LPS in stimulating endothelial cells. We analyzed Bacteroides and P. gingivalis lipid A structures using MALDI-TOF MS and gas chromatography to determine the structural basis for this phenomenon. Even though both Bacteroides and P. gingivalis lipid A molecules are penta-acylated and mono-phosphorylated, subtle differences in mass and fatty acid content could account for the observed difference in LPS potency. This fatty acid heterogeneity is also responsible for the peak "clusters" observed in the mass spectra and obfuscates the correlation between LPS structure and immunostimulatory ability. Further, we show the difference in potency between Bacteroides and P. gingivalis LPS is TLR4-dependent. Altogether, the data suggest subtle changes in lipid A structure may profoundly impact the host's innate immune response.
脂多糖A的结构修饰可显著影响宿主对细菌脂多糖（LPS）的炎症反应。脆弱拟杆菌是一种与危及生命的败血症和腹腔内脓肿形成相关的机会致病菌，而多形拟杆菌是宿主肠道组织正常发育的关键共生菌，二者均产生由五酰化脂多糖A组成的免疫刺激性脂多糖。在特定条件下，与牙周炎相关的口腔病原菌牙龈卟啉单胞菌也会产生一种带有五酰化脂多糖A的脂多糖。然而，这种脂多糖制剂在刺激内皮细胞方面的效力比拟杆菌脂多糖低100 - 1000倍。我们使用基质辅助激光解吸电离飞行时间质谱（MALDI - TOF MS）和气相色谱分析了拟杆菌和牙龈卟啉单胞菌的脂多糖A结构，以确定这一现象的结构基础。尽管拟杆菌和牙龈卟啉单胞菌的脂多糖A分子均为五酰化且单磷酸化，但质量和脂肪酸含量的细微差异可能解释了所观察到的脂多糖效力差异。这种脂肪酸异质性也是质谱中观察到的峰“簇”的原因，并模糊了脂多糖结构与免疫刺激能力之间的相关性。此外，我们表明拟杆菌和牙龈卟啉单胞菌脂多糖之间的效力差异是依赖于Toll样受体4（TLR4）的。总之，数据表明脂多糖A结构的细微变化可能会深刻影响宿主的先天免疫反应。
