五环三萜类手足口病病毒抑制剂的作用机制与结构优化研究

Hand,foot, and mouth disease (HFMD) is an acute infectious disease often broken out among the preschoolers. The seriously sick children are easily suffered from severe encephalitis, meningitis and other neurological damage.The HFMD harm has exceeded Japanese encephalitis and meningococcal meningitis. Entrovirus 71 (EV71)is the main causative pathogen of hand, foot and mouth disease. However, currently there is no clinically effective anti-viral drugs available for the treatment of EV71 HFMD. Our previous studies have found that a series of pentacyclic triterpenes have significant anti-EV71 viral activity, among which the best active compound has an IC50 value of 41 nM. Preliminary mechanism studies indicate that the pentacyclic triterpenes likely bind to the hydrophobic pocket on the EV71 capsid protein VP1, replacing the "pocket factor" so that the capsid protein is more stable and less susceptible to the release of viral genes to infect host cells. This application project is to study the mechanism of pentacyclic triterpenes as EV71 virus inhibitors, including to determine their anti- EV71 virus targets and modes of action. Based on the resulting findings, rational drug design, synthesis and biological evaluation of EV71 virus inhibitors will also be conducted with pentacyclic triterpenes as the skeletons. This research is expected to find a new direction for the development of anti- EV71 viral drugs and identify candidate compounds with drug likability to pave the way to drug discovery for treatment of hand foot and mouth disease.

手足口病是多发于学龄前儿童的急性传染病，重症患儿易出现脑炎、脑膜炎等神经系统伤害，其危害已超过流行性乙型脑炎和流行性脑脊髓膜炎。肠道病毒EV71型是手足口病的主要致病原，然而目前在临床上尚无有效的抗EV71病毒药物可用于手足口病的治疗。前期研究发现，一系列五环三萜化合物具有显著的抗EV71病毒活性，其中活性最好的化合物IC50值达41nM。初步的机制研究表明，五环三萜极可能结合于EV71病毒衣壳蛋白VP1上的疏水口袋，取代其中的"口袋因子"，使衣壳蛋白更稳定，病毒基因不易被释放感染宿主细胞。本课题研究五环三萜类EV71病毒抑制剂的作用机制，确定其抗EV71病毒的作用靶标和作用模式。并基于上述研究结果，以五环三萜为骨架进行EV71病毒抑制剂的合理药物设计、合成及生物活性研究。期望通过本项目研究为开发抗EV71病毒药物提供新方向，并发现具有成药性的候选化合物，为开发手足口病治疗药物奠定基础。

手足口病多发生于5岁以下儿童，其危害性已超过流行性乙型脑炎和流行性脑脊髓膜炎这两种乙类传染病。肠道病毒71型（EV71）是手足口病最主要的致病原，然而临床上尚无有效的抗EV71病毒药物。本项目研究发现齐墩果酸等天然五环三萜对EV71病毒具有显著的抑制活性。在此基础上，以天然五环三萜作为先导化合物，设计合成了200多个五环三萜化合物，并评价其对EV71病毒的抑制活性。通过本研究，一系列天然难得的五环三萜化合物如α-香树精(α-amyrin)、β-香树精(β-amyrin)、δ-齐墩果酸的合成方法得以建立，为深入发掘这类化合物的医药价值奠定了基础。通过结构优化获得了一批IC50达nM级的新型强效EV71抑制剂，为研制手足口病防治药物提供了潜在候选化合物。本项目还探讨了五环三萜类EV71抑制剂的可能作用机制，研究表明五环三萜化合物可能结合于对EV71病毒基因感染起关键作用的衣壳蛋白VP1上。本课题组研究还发现五环三萜化合物具有显著的降胆固醇作用，其能抑制在胆固醇合成中起关键作用的氧化角鲨烯环合酶(OSC)和在胆固醇转运中起关键作用的胆固醇脂转移蛋白(CETP)。鉴于病毒感染与宿主细胞脂质微环境密切相关，该发现为深入研究五环三萜类EV71抑制剂的作用机制提供了新思路，即五环三萜也可能通过干预宿主细胞脂质微环境而发挥EV71抑制活性。