Rapid and Quantitative Assay of Amyloid-Seeding Activity in Human Brains Affected with Prion Diseases.

The infectious agents of the transmissible spongiform encephalopathies are composed of amyloidogenic prion protein, PrPSc. Real-time quaking-induced conversion can amplify very small amounts of PrPSc seeds in tissues/body fluids of patients or animals. Using this in vitro PrP-amyloid amplification assay, we quantitated the seeding activity of affected human brains. End-point assay using serially diluted brain homogenates of sporadic Creutzfeldt–Jakob disease patients demonstrated that 50% seeding dose (SD50) is reached approximately 1010/g brain (values varies 108.79–10.63/g). A genetic case (GSS-P102L) yielded a similar level of seeding activity in an autopsy brain sample. The range of PrPSc concentrations in the samples, determined by dot-blot assay, was 0.6–5.4 μg/g brain; therefore, we estimated that 1 SD50 unit was equivalent to 0.06–0.27 fg of PrPSc. The SD50 values of the affected brains dropped more than three orders of magnitude after autoclaving at 121°C. This new method for quantitation of human prion activity provides a new way to reduce the risk of iatrogenic prion transmission.

传染性海绵状脑病的病原体由具有淀粉样变特性的朊病毒蛋白PrPSc组成。实时震荡诱导转化能够扩增患者或动物组织/体液中极少量的PrPSc种子。利用这种体外PrP - 淀粉样蛋白扩增检测方法，我们对受影响的人脑的播种活性进行了定量。对散发性克雅氏病患者的脑匀浆进行系列稀释后进行终点检测，结果表明，达到50%播种剂量（SD50）约为每克脑10¹⁰（数值在每克10⁸.⁷⁹ - 10¹⁰.⁶³之间变化）。一个遗传性病例（GSS - P102L）在尸检脑样本中显示出相似水平的播种活性。通过斑点印迹法测定的样本中PrPSc浓度范围为每克脑0.6 - 5.4微克；因此，我们估计1个SD50单位相当于0.06 - 0.27飞克的PrPSc。在121°C高压灭菌后，受影响大脑的SD50值下降了三个多数量级。这种定量检测人朊病毒活性的新方法为降低医源性朊病毒传播风险提供了一种新途径。