Laboratory of Persistent Viral Diseases, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, Hamilton, MT 59840, USA.
Proc Natl Acad Sci U S A. 2011 Nov 29;108(48):E1244-53. doi: 10.1073/pnas.1111255108. Epub 2011 Nov 7.
Prions are unconventional infectious agents that cause transmissible spongiform encephalopathy (TSE) diseases, or prion diseases. The biochemical nature of the prion infectious agent remains unclear. Previously, using a protein misfolding cyclic amplification (PMCA) reaction, infectivity and disease-associated protease-resistant prion protein (PrPres) were both generated under cell-free conditions, which supported a nonviral hypothesis for the agent. However, these studies lacked comparative quantitation of both infectivity titers and PrPres, which is important both for biological comparison with in vivo-derived infectivity and for excluding contamination to explain the results. Here during four to eight rounds of PMCA, end-point dilution titrations detected a >320-fold increase in infectivity versus that in controls. These results provide strong support for the hypothesis that the agent of prion infectivity is not a virus. PMCA-generated samples caused the same clinical disease and neuropathology with the same rapid incubation period as the input brain-derived scrapie samples, providing no evidence for generation of a new strain in PMCA. However, the ratio of the infectivity titer to the amount of PrPres (specific infectivity) was much lower in PMCA versus brain-derived samples, suggesting the possibility that a substantial portion of PrPres generated in PMCA might be noninfectious.
朊病毒是一种非常规的传染性病原体，可引起传染性海绵状脑病（TSE）或朊病毒病。朊病毒感染性病原体的生化性质仍不清楚。以前，使用蛋白质错误折叠循环扩增（PMCA）反应，在无细胞条件下均产生感染性和与疾病相关的蛋白酶抗性朊蛋白（PrPres），这支持了该病原体的非病毒假说。然而，这些研究缺乏对感染性滴度和 PrPres 的定量比较，这对于与体内获得的感染性进行生物学比较以及排除污染以解释结果都很重要。在此期间，在 4 到 8 轮 PMCA 中，终点稀释滴定检测到感染性比对照增加了 >320 倍。这些结果强烈支持了这样的假设，即朊病毒感染性的病原体不是病毒。PMCA 产生的样本与输入的脑源性瘙痒样本引起相同的临床疾病和神经病理学，并具有相同的快速潜伏期，没有证据表明在 PMCA 中产生了新的菌株。然而，与脑源性样本相比，PMCA 中感染性滴度与 PrPres 量的比值（特异性感染性）要低得多，这表明 PMCA 中产生的大量 PrPres 可能没有感染性。
