Contributions of prion strains and substrains to prion zoonotic potential and evolution

朊病毒是一种传染性蛋白质的人畜共患病原体，可以在新的复制环境中迅速进化。 朊病毒菌株由PrPSc的菌株特异性构象编码，PrPSc是宿主编码的朊病毒的感染性形式。 朊病毒蛋白科林格和克拉克假设朊病毒株是一种优势朊病毒株的混合物， 和亚株。为了支持这一假设，我们和其他人已经表明：i）用抗朊病毒治疗朊病毒 药物可导致耐药菌株的出现，ii）物理方法（例如热稳定性）， 部分朊病毒可以选择具有改变的菌株特性的朊病毒，和iii）给定宿主内的菌株 物种可以有不同的宿主范围。尽管有这些数据，直接证据的存在，预先存在的 缺乏亚株，因此，亚株对朊病毒进化的贡献还没有得到证实。 探讨了这项工作的长期目标是防止朊病毒进化到一个新的复制环境。的 本申请的总体目的是确定优势朊病毒株的相对贡献， 朊病毒种间传播的亚型。在这个应用程序中，我们将测试的假设是，朊病毒 亚株驱动朊病毒传播到新的PrP基因型。这个假设是基于我们的新发现， 选择性减少PrPSc从生物克隆仓鼠适应嗜睡（DY）株的传染性 水貂脑病（TME），使用两种机制不同的方法，允许出现， 分离与DY不同的预先存在的亚株。此外，该亚株出乎意料地具有 与DY TME不同的主机范围。为了验证我们的假设，我们将首先探讨 使用互补方法从稳定和不稳定朊病毒菌株中获得预先存在的亚株（构象 稳定性、蛋白酶消化、热稳定性）以选择性地减少优势菌株的数量。的频率和 分离的亚株的多样性将使用互补的体外朊病毒检测方法来确定， 动物生物测定第二，我们将探索充分研究仓鼠/小鼠物种屏障， 互补的体外和体内方法，以确定优势菌株的相对贡献， 种间传播的亚型。优势菌株与优势菌株之间的菌株干扰概念 将对亚株进行种间传播试验。这些研究意义重大，因为它对 了解作为当前朊病毒治疗方法的亚株对朊病毒进化的贡献， 针对优势菌株的开发（疫苗接种、抗朊病毒药物、环境缓解程序）。它 因此，这些方法可能会无意中导致预先存在的朊病毒株的出现， 具有改变的人畜共患病潜力和/或增加的致病性。总的来说，这些研究将直接测试 Collinge和Clark模型的朊病毒应变动力学，并将允许更精确的评价朊病毒的潜力 菌株以适应新的复制环境（例如，慢性消耗性疾病传播给人类）。

Prions are infectious protein-only zoonotic agents that can rapidly evolve in a new replication environment. Prion strains are encoded by strain-specific conformations of PrPSc, the infectious form of the host-encoded prion protein, PrPC. Collinge and Clarke hypothesized that prion strains are a mixture of a dominant prion strain and substrains. In support of this hypothesis, we and others have shown: i) treatment of prions with anti-prion drugs can result in the emergence of a drug resistant strain, ii) physical methods (e.g. thermostability) that partially inactivate prions can select for prions with altered strain properties, and iii) strains within a given host species can have different host ranges. Despite these data, direct evidence for the existence of preexisting substrains is lacking and, consequently, the contributions of substrains to prion evolution has not been explored. The long-term goal of this work is to prevent prion evolution to a new replicative environment. The overall objective of this application is to determine the relative contributions of the dominant prion strain and substrains to interspecies transmission of prions. In this application we will test the hypothesis is that prion substrains drive prion transmission to a new PrP genotype. The hypothesis is based on our new discovery that selective reduction of PrPSc from the biologically cloned hamster-adapted drowsy (DY) strain of transmissible mink encephalopathy (TME), using two mechanistically different methods, allows for the emergence and isolation of a preexisting substrain that is distinct from DY. Moreover, this substrain unexpectedly has a different host range than DY TME. To test our hypothesis, we will first explore the frequency and diversity of preexisting substrains from stable and unstable prion strains using complimentary methods (conformational stability, protease digestion, thermostability) to selectively depopulate the dominant strain. The frequency and diversity of substrains isolated will be determined using complementary in vitro prion detection methods and animal bioassay. Second, we will explore the well-studied hamster/mouse species barrier using complementary in vitro and in vivo methods to determine the relative contributions of the dominant strain and substrains to interspecies transmission. The concept of strain interference between the dominant strain and substrains will be tested in regards interspecies transmission. These studies are significant since it is critical to understand the contributions of substrains to prion evolution as current prion treatment methods in development (vaccination, anti-prion drugs, environmental mitigation procedures) target the dominant strain. It is therefore possible that these methods will inadvertently result in the emergence of preexisting prion strains with altered zoonotic potential and/or increased pathogenicity. Overall, these studies will directly test the Collinge and Clark model of prion strain dynamics and will allow for a more precise evaluation potential of prion strains to adapt to a new replication environment (e.g., chronic wasting disease transmission to humans).