A new synergy for flavivirus therapy: RNAi enhancement and viral mutagens

描述（由申请人提供）：黄病毒属，包括80种单链阳性RNA病毒，包括大量全球重要的新兴病原体。在过去50年中，许多黄病毒，如登革热病毒、西尼罗河病毒和蜱传脑炎病毒，在发病率、疾病严重程度和/或地理范围上都有显著增加。例如，全世界每年的登革出血热病例数已从20世纪50年代的近0例上升到今天的50万例。由于未能控制病媒以限制病毒传播，以及缺乏针对登革热和西尼罗河等病毒的疫苗，这些趋势更加恶化。因此，迫切需要有效的抗病毒治疗来减轻黄病毒带来的疾病负担。然而，目前尚无针对黄病毒的许可疗法，这主要是因为现有的广谱药物对黄病毒没有疗效，或者产生了不可接受的高毒性。为了克服这些限制，不仅需要开发新的抗病毒药物，还需要开发创新的策略来降低其有效剂量，从而减轻毒性。最近发现，某些fda批准的氟喹诺酮类抗生素可以增强RNA干扰途径的活性，这是一种有希望的新策略。RNA干扰是真核生物普遍存在的抗病毒防御，它通过靶向小干扰RNA （siRNA）到病毒基因组的互补区域起作用；与siRNA结合的基因组被标记为切割和降解。由于siRNA与目标序列的结合需要近乎完美的互补性，因此RNAi对破坏这种互补性的病毒突变施加了选择压力。本研究将验证以下假设：增强RNAi会增强致突变核苷类似物对登革热病毒突变率和复制的影响，以及RNAi增强的协同效应会加速核苷类似物驱动的致死性突变。如果这一假设是正确的，本研究的发现将代表黄病毒病新疗法发展的重大进展。

DESCRIPTION (provided by applicant): The genus Flavivirus, comprising 80 species of single-stranded, positive-sense RNA viruses, includes a large number of globally significant emerging pathogens. In the last 50 years many flaviviruses, such as dengue, West Nile, and tick-borne encephalitis viruses, have exhibited dramatic increases in incidence, disease severity and/or geographic range. For example the annual number of cases of dengue hemorrhagic fever cases worldwide has risen from nearly 0 in the 1950's to 500,000 today. These trends are exacerbated by failure of vector control to limit virus spread as well as the absence of vaccines for viruses such as dengue and West Nile. Thus effective antiviral therapies are urgently needed to ameliorate the disease burden imposed by flaviviruses. At present, however, no licensed therapies are available for any flavivirus, largely because existing broad-spectrum drugs have failed to show efficacy against flaviviruses or have generated unacceptably high levels of toxicity. To overcome these limitations, it will be necessary to develop not only new antiviral drugs but also innovative strategies to lower their effective dose and thereby mitigate toxicity. The recent discovery that certain FDA-approved fluoroquinolone antibiotics enhance the activity of the RNA interference pathway suggests one promising new strategy. RNA interference is a ubiquitious antiviral defense of eukaryotes that acts by targeting small interfering RNA's (siRNA's) to complementary regions in the viral genome; genomes bound to siRNA's are marked for cleavage and degradation. Because binding of siRNA's to a target sequence requires nearly perfect complementarity, RNAi imposes selection pressure for viral mutation that disrupts such complementarity. The proposed research will test the hypothesis that enhancing RNAi will amplify the effect of mutagenic nucleoside analogs on dengue virus mutation rate and replication, and that the synergistic effect of RNAi enhancement will accelerate lethal mutagenesis driven by nucleoside analogs. If this hypothesis is correct, the finding of this study will represent a significant advance in the development of new therapies for flaviviral disease.