Naturally Occurring Lipid A Mutants in Neisseria meningitidis from Patients with Invasive Meningococcal Disease Are Associated with Reduced Coagulopathy
Naturally Occurring Lipid A Mutants in Neisseria meningitidis from Patients with Invasive Meningococcal Disease Are Associated with Reduced Coagulopathy
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DOI：
10.1371/journal.ppat.1000396
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发表时间：
2009-04-01
期刊：
影响因子：
6.7
通讯作者：
van der Ley, Peter
中科院分区：
文献类型：
--
作者：
Fransen, Floris;Heckenberg, Sebastiaan G. B.;van der Ley, Peter
脑膜炎奈瑟菌是全世界细菌性脑膜炎和败血症的主要原因。内毒素是革兰氏阴性细菌外膜的主要成分，通过Toll样受体4(TLR4)被哺乳动物细胞感知，从而激活促炎细胞因子途径。TLR4识别脂多糖分子的脂类A部分，脂类A的化学组成决定了TLR4识别它的程度。据报道，脑膜炎奈瑟氏菌产生含有六个酰基链的类脂A，这是识别TLR4的最佳数量。事实上，脑膜炎双球菌败血症通常被视为典型的内毒素介导的疾病。在目前的研究中，我们从464名患者中筛选出脑膜炎双球菌分离株，以了解它们在体外诱导细胞因子产生的能力。我们发现，其中约9%的菌株的效力明显低于野生型菌株。对几个低活性菌株的脂类A进行了质谱分析，发现它们是五酰化的，这表明添加二级酰链所需的lpxL1或lpxL2基因发生了突变。对这些基因的测序显示，所有低活性菌株都有使lpxL1基因失活的突变。为了了解lpxL1突变是否会给出不同的临床图景，我们在一项针对成人脑膜炎双球菌脑膜炎的前瞻性全国观察性队列研究中调查了这些突变的临床相关性。感染lpxL1突变的患者出现皮疹的频率显著减少，血小板计数增加，这与细胞因子诱导减少和组织因子介导的凝血障碍激活减少一致。总之，我们首次报道，由于lpxL1基因的突变，令人惊讶的是，有很大一部分脑膜炎双球菌临床分离株存在脂多糖和低酰化的脂蛋白A。由此产生的低活性内毒素可能通过帮助细菌逃避天然免疫系统而在毒力方面发挥重要作用。我们的结果提供了第一个脑膜炎奈瑟氏菌特定突变的例子，这种突变可以与脑膜炎双球菌疾病的临床病程相关。
Neisseria meningitidis is a major cause of bacterial meningitis and sepsis worldwide. Lipopolysaccharide (LPS), a major component of the Gram-negative bacterial outer membrane, is sensed by mammalian cells through Toll-like receptor 4 (TLR4), resulting in activation of proinflammatory cytokine pathways. TLR4 recognizes the lipid A moiety of the LPS molecule, and the chemical composition of the lipid A determines how well it is recognized by TLR4. N. meningitidis has been reported to produce lipid A with six acyl chains, the optimal number for TLR4 recognition. Indeed, meningococcal sepsis is generally seen as the prototypical endotoxin-mediated disease. In the present study, we screened meningococcal disease isolates from 464 patients for their ability to induce cytokine production in vitro. We found that around 9% of them were dramatically less potent than wild-type strains. Analysis of the lipid A of several of the low-activity strains by mass spectrometry revealed they were penta-acylated, suggesting a mutation in the lpxL1 or lpxL2 genes required for addition of secondary acyl chains. Sequencing of these genes showed that all the low activity strains had mutations that inactivated the lpxL1 gene. In order to see whether lpxL1 mutants might give a different clinical picture, we investigated the clinical correlate of these mutations in a prospective nationwide observational cohort study of adults with meningococcal meningitis. Patients infected with an lpxL1 mutant presented significantly less frequently with rash and had higher thrombocyte counts, consistent with reduced cytokine induction and less activation of tissue-factor mediated coagulopathy. In conclusion, here we report for the first time that a surprisingly large fraction of meningococcal clinical isolates have LPS with underacylated lipid A due to mutations in the lpxL1 gene. The resulting low-activity LPS may have an important role in virulence by aiding the bacteria to evade the innate immune system. Our results provide the first example of a specific mutation in N. meningitidis that can be correlated with the clinical course of meningococcal disease.