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

描述(申请人提供)：黄病毒属，由80种单链、阳性RNA病毒组成，包括大量具有全球意义的新兴病原体。在过去的50年里，许多黄病毒，如登革热、西尼罗河病毒和壁虱传播的脑炎病毒，在发病率、疾病严重性和/或地理范围方面都出现了戏剧性的增长。例如，全世界每年的登革热出血热病例已从20世纪50年代的近0例上升到今天的50万例S。病媒控制未能限制病毒传播，以及登革热和西尼罗河等病毒缺乏疫苗，加剧了这些趋势。因此，迫切需要有效的抗病毒疗法来减轻黄病毒造成的疾病负担。然而，目前还没有针对任何黄病毒的许可疗法，主要是因为现有的广谱药物未能显示出对黄病毒的疗效，或者产生了令人无法接受的高毒性。为了克服这些限制，不仅有必要开发新的抗病毒药物，而且有必要开发创新的战略，以降低其有效剂量，从而减轻毒性。最近发现，FDA批准的某些氟喹诺酮类抗生素可以增强RNA干扰途径的活性，这表明了一种有希望的新策略。RNA干扰是真核生物普遍存在的一种抗病毒防御机制，它通过将小干扰RNA(SiRNA)靶向病毒基因组中的互补区域来发挥作用；与siRNA结合的基因组被标记为切割和降解。由于siRNA与靶序列的结合需要几乎完全的互补，RNAi对破坏这种互补的病毒突变施加了选择压力。这项拟议的研究将检验这样一种假设，即增强RNAi将放大诱变核苷类似物对登革病毒突变率和复制的影响，以及RNAi增强的协同效应将加速由核苷类似物驱动的致命性突变。如果这一假设是正确的，这项研究的发现将代表着黄病毒疾病新疗法开发的重大进步。

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.