Chemical Biology and Therapeutics Science, Broad Institute of Harvard and MIT, Cambridge, MA 02142;
Program in Biological and Biomedical Sciences, Harvard Medical School, Boston, MA 02115.
Proc Natl Acad Sci U S A. 2019 Apr 16;116(16):7793-7798. doi: 10.1073/pnas.1901947116. Epub 2019 Apr 1.
Reduction of native prion protein (PrP) levels in the brain is an attractive strategy for the treatment or prevention of human prion disease. Clinical development of any PrP-reducing therapeutic will require an appropriate pharmacodynamic biomarker: a practical and robust method for quantifying PrP, and reliably demonstrating its reduction in the central nervous system (CNS) of a living patient. Here we evaluate the potential of ELISA-based quantification of human PrP in human cerebrospinal fluid (CSF) to serve as a biomarker for PrP-reducing therapeutics. We show that CSF PrP is highly sensitive to plastic adsorption during handling and storage, but its loss can be minimized by the addition of detergent. We find that blood contamination does not affect CSF PrP levels, and that CSF PrP and hemoglobin are uncorrelated, together suggesting that CSF PrP is CNS derived, supporting its relevance for monitoring the tissue of interest and in keeping with high PrP abundance in brain relative to blood. In a cohort with controlled sample handling, CSF PrP exhibits good within-subject test-retest reliability (mean coefficient of variation, 13% in samples collected 8-11 wk apart), a sufficiently stable baseline to allow therapeutically meaningful reductions in brain PrP to be readily detected in CSF. Together, these findings supply a method for monitoring the effect of a PrP-reducing drug in the CNS, and will facilitate development of prion disease therapeutics with this mechanism of action.
降低大脑中原发性朊病毒蛋白 (PrP) 的水平是治疗或预防人类朊病毒病的一种有吸引力的策略。任何降低 PrP 的治疗药物的临床开发都需要适当的药效学生物标志物：一种实用且稳健的方法来定量 PrP，并可靠地证明其在活患者的中枢神经系统 (CNS) 中减少。在这里，我们评估了基于 ELISA 的人脑脊液 (CSF) 中 PrP 定量作为降低 PrP 治疗药物的生物标志物的潜力。我们表明 CSF PrP 在处理和储存过程中对塑料吸附非常敏感，但通过添加去污剂可以最大限度地减少其损失。我们发现血液污染不会影响 CSF PrP 水平，并且 CSF PrP 和血红蛋白之间没有相关性，这表明 CSF PrP 来自中枢神经系统，支持其用于监测感兴趣的组织的相关性，并且与大脑中相对于血液的高 PrP 丰度一致。在一个控制样本处理的队列中，CSF PrP 表现出良好的个体内测试-重测可靠性（相隔 8-11 周采集的样本中平均变异系数为 13%），基线足够稳定，可以很容易地在 CSF 中检测到大脑 PrP 的治疗性有意义减少。总之，这些发现提供了一种监测 CNS 中降低 PrP 药物作用的方法，并将促进具有这种作用机制的朊病毒病治疗药物的开发。
