Effect of Thiopurines on RNA Viruses/Hepatitis C Virus

描述(申请人提供)：来自黄病毒科的病毒，包括西尼罗河病毒、登革热病毒和丙型肝炎病毒(丙型肝炎病毒)，是发病率和死亡率的重要原因，但几乎没有治疗选择。脱氧核糖核苷类似物是人类免疫缺陷病毒(HIV)抗病毒治疗的重要组成部分，但核糖核苷类似物对丙型肝炎病毒或RNA病毒的潜在影响相对较少。我们已经确定了在细胞培养中硫嘌呤核苷类似物在无细胞毒性的情况下抑制模型黄病毒，牛病毒性腹泻病毒(BVDV)的条件。利巴韦林是另一种嘌呤类似物，可提高干扰素治疗的疗效。关于利巴韦林的作用机制已经提出了多种，但仍不清楚哪种机制(S)占主导地位。丙型肝炎病毒阳性的移植患者经常暴露于长期的免疫抑制药中，包括硫嘌呤，这些药物也会改变嘌呤代谢。由于这些药物都有利巴韦林的部分机制选择，但不是全部，我们将比较每种药物对病毒复制的影响。这项建议的目标是将这些发现推广到丙型肝炎病毒，并确定其作用机制。将测试硫嘌呤对丙型肝炎病毒复制子的抗病毒效果，以及它们是否对病毒聚合酶施加选择性压力。将通过丙型肝炎病毒聚合酶和BVDV聚合酶对硫嘌呤进行识别和利用测试，这将有助于我们设计更有效的核苷。最后，我们将通过观察嘌呤库的大小以及改变硫嘌呤代谢对硫嘌呤抗病毒能力的影响来进一步确定这种抑制的机制。这项建议将确定硫嘌呤对RNA病毒复制的相对直接和间接影响，以及这种影响对使用利巴韦林等相关嘌呤治疗丙型肝炎患者的影响。

DESCRIPTION (provided by applicant): Viruses from the Family Flaviviridae, including West Nile Virus, Dengue Virus and Hepatitis C Virus (HCV), are significant causes of morbidity and mortality, yet have few to no treatment options. Deoxyribonucleoside analogs form an important part of antiviral therapy for human immunodeficiency virus (HIV), but ribonucleoside analogs have been relatively unstudied for their potential to affect HCV or RNA viruses in general. We have determined conditions in which thiopurine nucleoside analogs inhibit a model Flaviviridae, Bovine Viral Diarrhea Virus (BVDV), in cell culture without cytotoxicity. Ribavirin, another purine analog, increases the efficacy of interferon treatment. Multiple mechanisms have been proposed for how ribavirin may act, but it remains unclear which mechanism(s) predominant. HCV positive transplant patients are often exposed to long-term immunosuppressive agents including thiopurines that also alter purine metabolism. Since these drugs share some, but not all of the mechanistic options for ribavirin, we will compare the effect of each on viral replication. The goal of this proposal is to extend these findings to HCV and determine the mechanism of action. Thiopurines will be tested for antiviral effect on the HCV replicon, and if they exert selective pressure on viral polymerases. Thiopurines will be tested for recognition, and utilization by the HCV and BVDV polymerase, which will aid us in designing more potent nucleosides. Finally we will further define the mechanism of this inhibition by looking at the size of purine pools and the effect of altering thiopurine metabolism on thiopurine's antiviral capacity. This proposal will determine the relative direct and indirect effect of thiopurines on RNA viral replication and the implications of that effect for the treatment of HCV patients with related purines such as ribavirin.