Role of skin prions in disease transmission and diagnostic testing of human prion disease

摘要 朊病毒（或PrPSc）是致命的传染性朊病毒疾病（包括散发性）的病原体。 人类的克雅氏病（sCJD，最常见的人类朊病毒病）以及 羊瘙痒病、疯牛病和动物慢性消耗病。sCJD可通过医疗或 由于患者大脑中大量感染性朊病毒的污染，值得注意的是，一些 流行病学研究也将sCJD风险与非神经外科手术联系起来，但实验证据表明， 因为缺乏这样的联系。sCJD目前无法治愈。在临床症状出现时，永久性的大脑 损害已经发生。缺乏针对该疾病的侵入性较小的早期诊断测试可能导致 错过了未来治疗的关键窗口，由于文化限制，脑尸检率较低 阻碍了对sCJD的监测，而这对于有效预防医源性sCJD至关重要 传动.我们最近的研究使用高灵敏度的实时quaking-induced转换（RT- QuIC）测定和基于人源化转基因（Tg）小鼠的生物测定显示，sCJD的皮肤 患者携带有传染性朊病毒（Orrú等人，2017年）。我们新的初步结果进一步表明， PrPSc可以通过RT-QuIC和系列蛋白质错误折叠循环扩增（sPMCA）测定来检测，即使 在朊病毒感染的动物模型中的无症状阶段。我们假设皮肤PrPSc可以是 医源性朊病毒传播的来源和临床前/死亡前/死亡后的生物标志物 朊病毒疾病的诊断测试。为了检验假设，将追求以下四个目标： (1)定量sCJD患者皮肤朊病毒的感染性，（2）确定PrPSc在 皮肤，（3）评估皮肤PrPSc作为医源性传播来源的潜力，以及（4）验证 皮肤PrPSc作为朊病毒病诊断生物标志物我们预计，拟议的研究不仅将 揭示了通过皮肤朊病毒在人与人之间传播sCJD的潜在风险， 朊病毒疾病的替代临床前/死亡前/死亡后诊断测定。此外，新 这项研究产生的知识可能适用于更常见的神经退行性疾病， 如阿尔茨海默氏症和帕金森氏症，其中疾病特异性错误折叠蛋白质已经 在各个患者的皮肤中观察到。

ABSTRACT Prions (or PrPSc) are the causal agents of fatal transmissible prion diseases including sporadic Creutzfeldt-Jakob disease (sCJD, the most common human prion disease) in humans as well as scrapie, mad cow disease and chronic wasting disease in animals. sCJD is transmissible via medical or surgical procedures due to contamination by abundant infectious prions in the brain of patients. Notably, some epidemiological studies have also associated sCJD risk with non-neurosurgeries but experimental evidence for such a link is lacking. sCJD is currently incurable. At the onset of clinical symptoms, permanent brain damages already occurred. The absence of less invasive early diagnostic tests for the disease can result in missing the critical window for future treatments, and low brain autopsy rate due to cultural constraints prevents the surveillance of sCJD that is essential for effective prevention of iatrogenic sCJD transmissions. Our recent study using the highly sensitive real-time quaking-induced conversion (RT- QuIC) assay and humanized transgenic (Tg) mice-based bioassay revealed that the skin of sCJD patients harbors infectious prions (Orrú et al., 2017). Our new preliminary results further indicate that skin PrPSc is detectable by both RT-QuIC and serial protein misfolding cyclic amplification (sPMCA) assays even at the asymptomatic stage in a prion-infected animal model. We hypothesize that skin PrPSc can be both a source of iatrogenic prion transmission and a biomarker for preclinical/premortem/postmortem diagnostic testing of prion diseases. To test for the hypothesis, the following four Aims will be pursued: (1) to quantitate infectivity of skin prions from sCJD patients, (2) to pinpoint the distribution of PrPSc within the skin, (3) to evaluate the potential of skin PrPSc as the source of iatrogenic transmission, and (4) to validate skin PrPSc as a biomarker for diagnosis of prion diseases. We expect that the proposed study will not only shed light on the potential risk of human-to-human sCJD transmission via skin prions but also establish alternative preclinical/premortem/postmortem diagnostic assays for prion diseases. Moreover, new knowledge generated from this study may apply to much more common neurodegenerative diseases such as Alzheimer’s and Parkinson’s diseases where the disease-specific misfolded proteins have been observed in the skin of respective patients.