Priem Jan, Langeveld Jan P M, van Keulen Lucien J M, van Zijderveld Fred G, Andreoletti Olivier, Bossers Alex
Department of Infection Biology, Central Veterinary Institute of Wageningen UR, Lelystad, The Netherlands.
J Virol. 2014 Mar;88(5):2903-12. doi: 10.1128/JVI.02446-13. Epub 2013 Dec 26.
Bovine spongiform encephalopathy (BSE) can be efficiently transmitted to small ruminants (sheep and goats) with certain prion protein (PrP) genotypes. Polymorphisms in PrP of both the host and donor influence the transmission efficiency of transmissible spongiform encephalopathies (TSEs) in general. These polymorphisms in PrP also modulate the PrP conversion underlying TSE agent replication. Here we demonstrate that single-round protein misfolding cyclic amplification (PMCA) can be used to assess species and polymorphism barriers at the molecular level. We assessed those within and between the ovine and bovine species in vitro using a variety of natural scrapie and experimentally generated cross-species BSE agents. These BSE agents include ovBSE-ARQ isolates (BSE derived from sheep having the ARQ/ARQ PrP genotype), and two unique BSE-derived variants: BSE passaged in VRQ/VRQ sheep and a cow BSE agent isolate generated by back-transmission of ovBSE-ARQ into its original host. PMCA allowed us to quantitatively determine PrP conversion profiles that correlated with known in vivo transmissibility and susceptibility in the two ruminant species in which strain-specific molecular signatures, like its molecular weight after protease digestion, were maintained. Furthermore, both BSE agent isolates from ARQ and VRQ sheep demonstrated a surprising transmission profile in which efficient transmissions to both sheep and bovine variants was combined. Finally, all data support the notion that ARQ-derived sheep BSE points to a significant increase in virulence compared to all other tested scrapie- and BSE-derived variants reflected by the increased conversion efficiencies of previously inefficient convertible PrP variants (including the so-called "resistant" sheep ARR variant).
Prion diseases such as scrapie in sheep and goats, BSE in cattle, and Creutzfeldt-Jakob disease (CJD) in humans are fatal neurodegenerative diseases caused by prions. BSE is known to be transmissible to a variety of hosts, including sheep and humans. Based on the typical BSE agent strain signatures and epidemiological data, the occurrence of a novel variant of CJD in humans was linked to BSE occurrence in the United Kingdom. Measures, including genetic selection of sheep toward less susceptible PrP genotypes, have been implemented to lower the risk of BSE transmission into sheep, since the disease could potentially spread into a natural reservoir. In this study, we demonstrated using molecular PrP conversion studies that when BSE is first transmitted through sheep, the host range is modified significantly and the PrP converting potency increased, allowing the ovine BSE to transmit more efficiently than cow BSE into supposedly less susceptible hosts.
牛海绵状脑病（BSE）可有效地传播给具有特定朊病毒蛋白（PrP）基因型的小型反刍动物（绵羊和山羊）。宿主和供体的PrP多态性通常会影响传染性海绵状脑病（TSE）的传播效率。PrP中的这些多态性也会调节TSE病原体复制所依赖的PrP转化。在此，我们证明单轮蛋白错误折叠循环扩增（PMCA）可用于在分子水平评估物种和多态性屏障。我们使用多种天然痒病和实验产生的跨物种BSE病原体，在体外评估了绵羊和牛物种内部以及它们之间的屏障。这些BSE病原体包括ovBSE - ARQ分离株（源自具有ARQ/ARQ PrP基因型绵羊的BSE），以及两种独特的BSE衍生变体：在VRQ/VRQ绵羊中传代的BSE，以及通过将ovBSE - ARQ回传给其原始宿主而产生的一种牛BSE病原体分离株。PMCA使我们能够定量确定PrP转化谱，这些谱与两种反刍动物物种中已知的体内传染性和易感性相关，在这两种物种中，菌株特异性分子特征（如蛋白酶消化后的分子量）得以保留。此外，来自ARQ和VRQ绵羊的两种BSE病原体分离株都表现出令人惊讶的传播谱，即能够高效传播给绵羊和牛的变体。最后，所有数据都支持这样一种观点，即源自ARQ的绵羊BSE与所有其他测试的痒病和BSE衍生变体相比，毒力显著增加，这体现在先前转化效率较低的PrP变体（包括所谓的“抗性”绵羊ARR变体）的转化效率提高上。
绵羊和山羊的痒病、牛的BSE以及人类的克雅氏病（CJD）等朊病毒疾病是由朊病毒引起的致命神经退行性疾病。已知BSE可传播给多种宿主，包括绵羊和人类。基于典型的BSE病原体菌株特征和流行病学数据，人类新型变异型CJD的出现与英国的BSE疫情相关。由于该疾病可能传播到自然宿主库中，已采取措施，包括对绵羊进行遗传选择，培育具有不易感PrP基因型的绵羊，以降低BSE传播给绵羊的风险。在本研究中，我们通过分子PrP转化研究表明，当BSE首次通过绵羊传播时，宿主范围会发生显著改变，PrP转化能力增强，使得绵羊BSE比牛BSE能更有效地传播到原本认为不易感的宿主中。
