Effect of Thiopurines on RNA Viruses/Hepatitis C Virus

描述（由申请人提供）：来自黄病毒科的病毒，包括西尼罗病毒、登革热病毒和丙型肝炎病毒（HCV），是导致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HCV或RNA病毒的潜在影响一直相对缺乏研究。我们已经确定条件下，硫嘌呤核苷类似物抑制模型黄病毒科，牛病毒性腹泻病毒（BVDV），在细胞培养无细胞毒性。另一种嘌呤类似物利巴韦林可以提高干扰素治疗的效果。关于利巴韦林如何起作用，已经提出了多种机制，但尚不清楚哪种机制占主导地位。HCV阳性移植患者经常暴露于长期免疫抑制剂，包括硫嘌呤，也会改变嘌呤代谢。由于这些药物与利巴韦林有一些共同的机制选择，但不是全部，我们将比较每种药物对病毒复制的影响。本提案的目标是将这些发现扩展到HCV并确定作用机制。将测试硫嘌呤对丙型肝炎病毒复制子的抗病毒作用，以及它们是否对病毒聚合酶施加选择性压力。硫嘌呤将被HCV和BVDV聚合酶识别和利用，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池的大小和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。该建议将确定硫嘌呤对RNA病毒复制的相对直接和间接影响，以及该影响对使用相关嘌呤（如利巴韦林）治疗HCV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.