Konold Timm, Lee Yoon Hee, Stack Michael J, Horrocks Claire, Green Robert B, Chaplin Melanie, Simmons Marion M, Hawkins Steve A C, Lockey Richard, Spiropoulos John, Wilesmith John W, Wells Gerald A H
Veterinary Laboratories Agency Weybridge, New Haw, Addlestone, UK.
BMC Vet Res. 2006 Oct 17;2:31. doi: 10.1186/1746-6148-2-31.
Given the theoretical proposal that bovine spongiform encephalopathy (BSE) could have originated from sheep scrapie, this study investigated the pathogenicity for cattle, by intracerebral (i.c.) inoculation, of two pools of scrapie agents sourced in Great Britain before and during the BSE epidemic. Two groups of ten cattle were each inoculated with pools of brain material from sheep scrapie cases collected prior to 1975 and after 1990. Control groups comprised five cattle inoculated with sheep brain free from scrapie, five cattle inoculated with saline, and for comparison with BSE, naturally infected cattle and cattle i.c. inoculated with BSE brainstem homogenate from a parallel study. Phenotypic characterisation of the disease forms transmitted to cattle was conducted by morphological, immunohistochemical, biochemical and biological methods.
Disease occurred in 16 cattle, nine inoculated with the pre-1975 inoculum and seven inoculated with the post-1990 inoculum, with four cattle still alive at 83 months post challenge (as at June 2006). The different inocula produced predominantly two different disease phenotypes as determined by histopathological, immunohistochemical and Western immunoblotting methods and biological characterisation on transmission to mice, neither of which was identical to BSE. Whilst the disease presentation was uniform in all scrapie-affected cattle of the pre-1975 group, the post-1990 inoculum produced a more variable disease, with two animals sharing immunohistochemical and molecular profile characteristics with animals in the pre-1975 group.
The study has demonstrated that cattle inoculated with different pooled scrapie sources can develop different prion disease phenotypes, which were not consistent with the phenotype of BSE of cattle and whose isolates did not have the strain typing characteristics of the BSE agent on transmission to mice.
鉴于有理论认为牛海绵状脑病（BSE）可能起源于羊瘙痒病，本研究通过脑内接种，调查了在BSE流行之前及期间源自英国的两批瘙痒病病原体对牛的致病性。两组各10头牛分别接种了1975年之前和1990年之后收集的羊瘙痒病病例的脑材料池。对照组包括5头接种无瘙痒病羊脑的牛、5头接种生理盐水的牛，以及为与BSE作比较的自然感染牛和在一项平行研究中脑内接种BSE脑干匀浆的牛。通过形态学、免疫组织化学、生物化学和生物学方法对传播给牛的疾病形式进行表型特征分析。
16头牛发病，9头接种1975年之前接种物，7头接种1990年之后接种物，4头牛在攻毒后83个月（截至2006年6月）仍存活。通过组织病理学、免疫组织化学和Western免疫印迹方法以及传播给小鼠后的生物学特征分析确定，不同接种物主要产生两种不同的疾病表型，均与BSE不同。虽然1975年之前组所有受瘙痒病感染的牛的疾病表现一致，但1990年之后的接种物产生的疾病更具变异性，有两头动物与1975年之前组的动物具有相同的免疫组织化学和分子谱特征。
该研究表明，接种不同批次瘙痒病病原体的牛可出现不同的朊病毒疾病表型，这些表型与牛BSE的表型不一致，且其分离株在传播给小鼠时不具有BSE病原体的毒株分型特征。
