IMMUNOBIOLOGY OF SCRAPIE VIRUS INFECTION

绵羊瘙痒病是一组疾病的集体原型 被命名为传染性海绵状脑病(TSE)。谢霆锋 疾病影响的物种范围很广，包括羊、牛、水貂、 人类、鹿、麋鹿和其他动物。小组的最新成员，牛人 海绵状脑病还是疯牛病？被认为是 都是从感染了瘙痒病的绵羊身上提取的。没有证据表明 羊瘙痒病会感染人类。然而，绵羊瘙痒病的传播 通过牛似乎改变了它的生物学特性 使疯牛病可以传染给人类。猪瘟的种间传播 疾病很难预测，但可能涉及复杂的问题 该物种特定蛋白质分子之间的相互作用 被认为，特别是一种被指定为PrP的蛋白质。 该项目的总体目标是确定PrP和其他 因素和条件控制着从一个物种向另一个物种的传播。 干预传播或疾病过程的策略将 将根据这些调查结果进行开发。猪瘟的种间传播 现在已知不同物种之间的疾病包括 所涉及物种的PrP之间的相互作用。 例如，在小鼠中引起疾病的TSE试剂可以在几个月内 环境会引起仓鼠的疾病，但仓鼠剂不会 在小鼠身上引起临床疾病。确定PrP如何影响 从仓鼠到小鼠的传播我们已经培育出转基因小鼠 表达仓鼠蛋白(HPRP)。HPRP已经表达了 使用包括神经元特异性烯醇化酶在内的各种启动子 针对神经元表达的启动子(NSE)，GFAP特异性 启动子针对星形胶质细胞和天然启动子的表达 导致在许多组织中表达。每一种类型的老鼠都有 培育出不表达PrP的PrP基因缺失小鼠。因此，我们 有几种我们用来研究的小鼠 PrP在特定细胞类型中的表达如何影响易感性 以及HPRP和小鼠PrP(MoPrP)如何相互作用。 在自然或NSE启动子控制下的表达HPRP是 对脑内感染的仓鼠瘙痒病完全敏感 接种疫苗。这一结果表明PrP在传播中起着关键作用 而这种仅限于神经元的表达足以 将会发生传播。如果NSE/HPRP在缺乏NSE/HPRP的小鼠中表达 功能性MoPrP表达，潜伏期缩短 表明MoPrP的存在在某种程度上与HPRP竞争 延缓疾病的发病。该药对小鼠有保护作用。 这种疾病要么被推迟了，要么完全被避免了。老鼠 在GFAP启动子(GFAP/HPRP)控制下表达HPRP不 接种仓鼠瘙痒病疫苗后出现临床症状。 然而，如果GFAP/HPRP在缺乏MoPrP的小鼠中表达， 在接种仓鼠制剂后，他们确实生病了。 这一结果表明，星形胶质细胞特异性表达HPRP是 也足以进行传输，尽管效率要低得多 如果表达仅限于神经元，情况就不是这样了。此外，这一点 结果显示MoPrP和HPRP之间存在很强的干扰 表达这两种基因的小鼠。因为TSE疾病被认为是 经口传播，我们还接种了NSE/HPRP TG小鼠和另一只 TG系标记为Tg7，其中HPRP在多个组织中表达， 用仓鼠瘙痒剂口服和腹腔注射。大多数 通过这些途径接种的小鼠如果同时表达两种小鼠 和HPRP。这些结果表明，对TSE进行治疗性干预 疾病可能基于这些干扰机制。我们还发现 这种仓鼠瘙痒病病原体在正常小鼠身上持续存在(被认为是 对仓鼠瘙痒病的抵抗力)，甚至超过了预期寿命 尽管这些小鼠没有瘙痒病的症状。这种坚持是 依赖于PrP的存在。我们还测定了它的动力学 仓鼠剂从老鼠体内清除。我们证明了尽管大多数特工 被迅速消除的那些坚持下来的最终可以适应 新物种通过盲目途径进入第二个接受者群体 必填项。这一结果与疯牛病是 来自绵羊，但在牛身上并不表现为临床疾病 直到在卡特尔发生了不止一次初级传球。坚持不懈和 最终适应一个“抗性”物种表明，类似的 这种情况可能发生在其他物种的组合中。

Scrapie of sheep is the prototype of a group of diseases collectively designated the transmissible spongiform encephalopathies (TSE). TSE diseases affect a wide range of species including sheep, cattle, mink, humans,deer,elk and others. The newest member of the group, bovine spongiform encephalopathy (BSE) or ?mad cow disease? is believed to have been derived from scrapie infected sheep. There is no evidence that sheep scrapie infects humans. However, passage of sheep scrapie through cattle appears to have altered its biological characteristics making BSE transmissible to humans. Interspecies transmission of TSE diseases is difficult to predict but probably involves complex interactions between specific protein molecules of the species considered and in particular a protein designated prion protein (PrP). The overall objective of this project is to determine how PrP and other factors and conditions govern transmission from one species to another. Strategies to interfere with the transmission or disease process will be developed based on these findings. Interspecies transmission of TSE diseases between and among various species is now known to involve interactions between the prion proteins (PrP) of the species involved. For example, the TSE agent which causes disease in mice can in a few circumstances cause disease in hamsters but the hamster agent does not cause clinical disease in mice. To determine how PrP influences transmission from hamsters to mice we have developed transgenic mice which express hamster prion protein (HPrP). The HPrP has been expressed using a variety of promoters including the neuron-specific enolase promoter (NSE) which targets expression to neurons, the GFAP specific promoter to target expression to astrocytes and natural promoters which result in expression in many tissues. Each of these types of mice has been bred to PrP null mice which do not express mouse PrP. Thus, we have available several types of mice which we have used to investigate how expression of PrP in specific cell types influences susceptibility to scrapie and how HPrP and mouse PrP (MoPrP) interact.Mice which express HPrP under the control of natural or NSE promoters are completely susceptible to hamster scrapie agent following intracerebral inoculation. This result showed that PrP is critical to transmission and that expression restricted to neurons is sufficient for transmission to occur. If NSE/HPrP was expressed in mice which lacked functional MoPrP expression, the incubation period was reduced indicating that the presence of MoPrP in some way competed with HPrP to delay the onset of disease. The effect was protective for the mice in that disease was either delayed or completely circumvented. Mice which express HPrP under the control of the GFAP promoter (GFAP/HPrP) did not become clinically sick after inoculation of hamster scrapie agent. However, if GFAP/HPrP was expressed in mice which lacked MoPrP, expression they did become sick following hamster agent inoculation. This result suggested that astrocyte specific expression of HPrP was also sufficient for transmission to occur though much less efficiently than was true if expression was limited to neurons. Furthermore, this result demonstrated very strong interference between MoPrP and HPrP in the mice which expressed both. Because TSE diseases are thought to be transmitted orally we also inoculated the NSE/HPrP Tg mice and another Tg line designated Tg7, where HPrP is expressed in multiple tissues, with hamster scrapie agent orally and intraperitoneally. Most of the mice inoculated by these routes survived if they expressed both mouse and HPrP. These results suggested that therapeutic intervention in TSE diseases could be based on these interference mechanisms.We also found that hamster scrapie agent persisted in normal mice, (thought to be resistant to hamster scrapie), over their expected lifespans even though the mice remained free of scrapie symptoms. This persistence was dependent on the presence of PrP. We also determined the kinetics of hamster agent clearance from mice. We showed that although most agent is rapidly eliminated that which persists can eventually adapt to the new species though blind passage to a second recipient group was required. This result is consistent with the theory that BSE was derived from sheep but was not manifest as clinical disease in cattle until more than a primary pass in cattlr had occurred. Persistence and eventual adaptation to a "resistant" species suggests that similar situations could occur in other species combinations.