IMMUNOBIOLOGY OF SCRAPIE VIRUS INFECTION

瘙痒症是一种自然发生的海绵状脑病， 引起临床和病理变化的绵羊和山羊 类似于人类的克雅氏病和库鲁病。 一种名为朊病毒蛋白（PrP）的独特蛋白质被发现是一种 羊瘙痒病感染性纯化样品的主要成分， 被一些人认为是真正的传染源 我们 先前从小鼠中分离出两个PrP mRNA的cDNA克隆 羊瘙痒病感染的老鼠大脑 我们已经将克隆小鼠 将PrP cDNA导入含牛乳头状瘤的表达质粒 病毒（BPV），并已诱导PrP的合成在小鼠上皮细胞 细胞 为了测试这些表达的蛋白质的可能感染性， 将超声处理的细胞悬浮液脑内接种到 断奶RML小鼠。 接种后160天， 出现瘙痒症的临床体征，表明PrP可能不是 传染性羊瘙痒症病原体，但更可能是一个正常的 以聚集形式积累的细胞蛋白质， 疾病过程的结果。 可能性是- 内源基因产物的翻译修饰导致 在创造传染性羊瘙痒病病原体方面， 完全排除在外。 因为动物组织不能提供令人满意的基质 为了进行羊瘙痒病病原体的生化分析或分离，我们 一直致力于开发羊瘙痒病感染组织 文化体系。 为了实现这一目标， 用羊瘙痒病因子成功地感染了小鼠源。 感染的培养物保持21代，良好 超过了确保复制所需的数量， 发生了。 该病原体的感染似乎具有种属特异性 来自仓鼠脑的病毒没有感染来自小鼠的病毒， 神经母细胞瘤细胞系。 阳性克隆已经被 从这些原始文化中。 它们包含大约50-100个 比在原始培养物中发现的多一倍， 提供了一种新的、更同质的瘙痒病病原体来源。

Scrapie is a naturally occurring spongiform encephalopathy of sheep and goats which causes clinical and pathological changes similar to those of Creutzfeld-Jakob and Kuru diseases of man. A unique protein called prion protein (PrP) has been found to be a major component of purified samples of scrapie infectivity and is believed by some people to be the actual infectious agent. We previously isolated two cDNA clones of the PrP mRNA from scrapie-infected mouse brain. We have ligated the cloned mouse PrP cDNA into an expression plasmid containing bovine papilloma virus (BPV) and have induced PrP synthesis in mouse epithelial cells. To test the possible infectivity of these expressed proteins, sonicated cell suspensions were inoculated intracerebrally into weanling RML mice. By 160 days post-inoculation no mice had developed clinical signs of scrapie suggesting that PrP may not be the infectious scrapie agent, but is more likely to be a normal cellular protein which accumulates in aggregated forms as a result of the disease process. The possibility that post- translational modification of the endogenous gene product results in creation of the infectious scrapie agent has not been completely excluded. Because animal tissues have not provided satisfactory substrates for the biochemical analysis or isolation of the scrapie agent, we have continued to work on development of scrapie infected tissue culture systems. Toward this goal neuroblastoma cell lines of mouse origin were successfully infected with scrapie agent. Infected cultures were maintained through 21 passages, well beyond the number needed to assure that replication had occurred. Infection appeared to be species-specific in that agent derived from hamster brain did not infect the mouse derived neuroblastoma cell lines. Positive clones have now been derived from these original cultures. They contain approximately 50-100 fold more agent than was found in the original cultures and should provide a new, more homogenous source of scrapie agent.