IMMUNOBIOLOGY OF SCRAPIE VIRUS INFECTION

羊瘙痒症是绵羊和山羊的海绵状脑病， 实验性地传播给其他几种动物。 类似 在牛和人类中发现的疾病。 没有病原体 被识别。 然而，蛋白酶K抗性形式（PrP-res）的 一种称为朊病毒蛋白（PrP）的内源性蛋白质， 传染性，并对疾病的发病机制很重要。 我们开发了一种敏感的PrP-res检测方法， 羊瘙痒病 基于PrP-res检测的分析更多 比目前使用的诊断方法更准确，主观性更低 基于对大脑的显微评估。 我们还发现PrP- 脾脏或淋巴结的res分析与 的大脑。 我们正在确定PrP-res是否在临床前积累 淋巴结疾病。此外，我们还分析了羊胎盘 为了确定PrP-res是否在临床疾病之前积累， 容易获得的组织。如果PrP-res在临床疾病之前蓄积 在胎盘或淋巴结中，用于感染死前试验可 第一次可以使用。我们还使用PrP-res分析， 测试牛的组织，以确定海绵状 脑病目前存在于美国牛，因此，是否 在美国可能发生类似于英国BSE的流行病。 RES分析还应该与人类疾病的诊断相关 同行 特异性PrP基因序列对种间传播的影响 海绵状脑病也在研究中。 为此，我们必须 在羊瘙痒病感染的小鼠中表达各种小鼠-仓鼠PrP构建体 神经母细胞瘤（MNB）细胞，现在正在小鼠和仓鼠中进行分析 来确定物种的向性是否发生了改变小鼠神经母细胞瘤 细胞也被用于研究PrP蛋白的正常功能 以及找出可能导致 导致内源性PrP蛋白转化为 疾病相关PrP-res形式。 使用转基因小鼠进行了类似的体内实验， 表达仓鼠PrP和不产生PrP的转基因小鼠（PrP 无效小鼠）。

Scrapie is a spongiform encephalopathy of sheep and goats which can be transmitted experimentally to several other animal species. Similar diseases are recognized in cattle and humans. No etiologic agent has been identified. However, the proteinase K resistant form (PrP-res) of an endogenous protein designated prion protein (PrP) purifies with infectivity and is important to disease pathogenesis. We developed a sensitive assay for PrP-res and utilized it to diagnose scrapie in sheep. Analysis based on PrP-res detection was much more accurate and less subjective than the currently used method of diagnosis based on the microscopic evaluation of brain. We also showed that PrP- res analysis of spleen or lymph node was nearly as accurate as analysis of brain. We are determining if PrP-res accumulates prior to clinical disease in lymph node. In addition we have analyzed placenta from sheep to determine if PrP-res accumulates prior to clinical disease in this easily obtained tissue. If PrP-res accumulates prior to clinical disease in either placenta or lymph node an ante mortem test for infection may for the first time be available. We are also using PrP-res analyses to test tissues from cattle in order to determine if spongiform encephalopathy currently exists in U.S. cattle and, thereby, whether an epidemic similar to BSE in Great Britain is possible in the U.S.A. PrP- res analysis should also be relevant for diagnosis of the human disease counterparts. The influence of specific PrP gene sequences on interspecies transmission of spongiform encephalopathies is also being studied. To do so, we have expressed various mouse-hamster PrP constructs in scrapie-infected mouse neuroblastoma (MNB) cells and are now analyzing them in mice and hamsters to determine if species tropism has been altered. Mouse neuroblastoma cells are also being used to study the normal function of the PrP protein as well as to identify factors which might account for the biochemical changes which lead to the conversion of the endogenous PrP protein to the disease associated PrP-res form. Similar experiments are being done in vivo using transgenic mice which express hamster PrP and transgenic mice which do not produce PrP (PrP null mice).