Moore S Jo, West Greenlee M Heather, Kondru Naveen, Manne Sireesha, Smith Jodi D, Kunkle Robert A, Kanthasamy Anumantha, Greenlee Justin J
Virus and Prion Research Unit, National Animal Disease Center, USDA, Agricultural Research Service, Ames, Iowa, USA.
Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee, USA.
J Virol. 2017 Sep 12;91(19). doi: 10.1128/JVI.00926-17. Print 2017 Oct 1.
Chronic wasting disease (CWD) is a naturally occurring, fatal neurodegenerative disease of cervids. The potential for swine to serve as hosts for the agent of CWD is unknown. The purpose of this study was to investigate the susceptibility of swine to the CWD agent following experimental oral or intracranial inoculation. Crossbred piglets were assigned to three groups, intracranially inoculated ( = 20), orally inoculated ( = 19), and noninoculated ( = 9). At approximately the age at which commercial pigs reach market weight, half of the pigs in each group were culled ("market weight" groups). The remaining pigs ("aged" groups) were allowed to incubate for up to 73 months postinoculation (mpi). Tissues collected at necropsy were examined for disease-associated prion protein (PrP) by Western blotting (WB), antigen capture enzyme immunoassay (EIA), immunohistochemistry (IHC), and real-time quaking-induced conversion (RT-QuIC). Brain samples from selected pigs were also bioassayed in mice expressing porcine prion protein. Four intracranially inoculated aged pigs and one orally inoculated aged pig were positive by EIA, IHC, and/or WB. By RT-QuIC, PrP was detected in lymphoid and/or brain tissue from one or more pigs in each inoculated group. The bioassay was positive in four out of five pigs assayed. This study demonstrates that pigs can support low-level amplification of CWD prions, although the species barrier to CWD infection is relatively high. However, detection of infectivity in orally inoculated pigs with a mouse bioassay raises the possibility that naturally exposed pigs could act as a reservoir of CWD infectivity. We challenged domestic swine with the chronic wasting disease agent by inoculation directly into the brain (intracranially) or by oral gavage (orally). Disease-associated prion protein (PrP) was detected in brain and lymphoid tissues from intracranially and orally inoculated pigs as early as 8 months of age (6 months postinoculation). Only one pig developed clinical neurologic signs suggestive of prion disease. The amount of PrP in the brains and lymphoid tissues of positive pigs was small, especially in orally inoculated pigs. Regardless, positive results obtained with orally inoculated pigs suggest that it may be possible for swine to serve as a reservoir for prion disease under natural conditions.
慢性消耗病（CWD）是一种自然发生的、致命的鹿科动物神经退行性疾病。猪作为慢性消耗病病原体宿主的可能性尚不清楚。本研究的目的是调查实验性经口或颅内接种后猪对慢性消耗病病原体的易感性。将杂交仔猪分为三组，分别为颅内接种组（n = 20）、经口接种组（n = 19）和未接种组（n = 9）。在商品猪达到上市体重的大致年龄时，每组中的一半猪被宰杀（“上市体重”组）。其余的猪（“老龄”组）在接种后长达73个月（mpi）的时间内进行培育。尸检时收集的组织通过蛋白质免疫印迹法（WB）、抗原捕获酶免疫测定法（EIA）、免疫组织化学法（IHC）和实时颤抖诱导转化法（RT-QuIC）检测与疾病相关的朊病毒蛋白（PrP）。还对选定猪的脑样本在表达猪朊病毒蛋白的小鼠中进行生物测定。4只颅内接种的老龄猪和1只经口接种的老龄猪通过EIA、IHC和/或WB检测呈阳性。通过RT-QuIC，在每个接种组的一只或多只猪的淋巴组织和/或脑组织中检测到PrP。在接受生物测定的5只猪中，有4只呈阳性。本研究表明，尽管慢性消耗病感染的种间屏障相对较高，但猪能够支持慢性消耗病朊病毒的低水平扩增。然而，用小鼠生物测定法在经口接种的猪中检测到传染性增加了自然暴露的猪可能成为慢性消耗病传染性储存宿主的可能性。我们通过直接脑内接种（颅内）或经口灌胃（经口）用慢性消耗病病原体感染家猪。早在8月龄（接种后6个月）时，在颅内和经口接种猪的脑和淋巴组织中就检测到了与疾病相关的朊病毒蛋白（PrP）。只有1只猪出现了提示朊病毒病的临床神经症状。阳性猪脑和淋巴组织中的PrP含量很少，尤其是经口接种的猪。尽管如此，经口接种猪获得的阳性结果表明，在自然条件下猪有可能成为朊病毒病的储存宿主。
