Study of CWD Deer and Elk Prion Disease in Nonhuman Primates

为了研究CWD跨物种传播的可能性，两种非人灵长类动物，松鼠猴和食蟹猴，经口或脑内感染来自CWD受影响的鹿或麋鹿的脑材料。 在2013财政年度结束时，13只脑内感染的松鼠猴中有13只出现了临床神经系统症状，并通过脑生化和病理学检测证实患有朊病毒病。在2014财政年度结束时，11只经口感染松鼠猴中有11只也发病。 在2016财年结束时，共对12只（2016财年为2只）感染CWD的食蟹猴实施了安乐死，并进行了朊病毒疾病筛查。 无论接种途径如何，这12只食蟹猴均未发生朊病毒疾病。三只食蟹猴仍在研究的这一部分，并计划在2016财年结束时对剩余的猴子实施安乐死并筛选朊病毒疾病。 在2008财年期间，用CWD感染松鼠猴的脑匀浆接种两只食蟹猴和两只松鼠猴，以评价CWD适应非人灵长类宿主的能力。在FY10期间，接种了适应性CWD的松鼠猴的两只松鼠猴均发生了疾病。 该接种物的潜伏期快得多，临床体征略有不同，表明适应了新的宿主或接种物的滴度更高。 来自松鼠猴的慢性消耗病成功传播到其他松鼠猴中证实了朊病毒感染性的存在。这一确认是重要的，因为相同的松鼠猴CWD接种物没有在表达人或鹿朊病毒蛋白的转基因小鼠中引起疾病，并且没有在仍在研究的任何食蟹猴中引起疾病。在FY13期间，其中一只食蟹猴因慢性体重减轻和肝功能衰竭而被人道处死。 对这只猴子进行了TSE疾病检测，结果为阴性，表明松鼠猴适应的CWD可能仍然无法感染非人灵长类动物的其他物种。本研究中剩余的猴子将在2016财年结束时被处以安乐死并进行朊病毒病检测。 除了测试受感染的松鼠猴大脑，我们还评估了受感染松鼠猴血液中朊病毒的感染性。在2016财年结束时，血液制品受体猴均未显示任何疾病体征。 为了进一步测试CWD对人类嗜性的适应性，我们在FY11期间将来自临床患病的第二代松鼠猴的材料接种到表达人朊病毒蛋白（tg66）的转基因小鼠中。在FY12期间，这些tg66小鼠被安乐死并检测朊病毒疾病。第二次传代研究中的所有小鼠均为朊病毒感染阴性。 没有传播到“人源化”小鼠是令人鼓舞的数据，支持CWD可能不会感染人类的结论。在FY15期间，我们开始了一项研究，以直接测试鹿源CWD向tg66小鼠的传播。 这些小鼠已接种疫苗，在2016财年结束时未发生疾病。 他们将继续接受朊病毒病的监测。

To study the possibility of cross-species transmission of CWD, two species of nonhuman primates, squirrel monkeys and cynomologus macaques, were infected orally or intracerebrally with brain material derived from CWD affected deer or elk. At the conclusion of FY13 thirteen of thirteen intracerebrally infected squirrel monkeys had developed clinical neurological signs and were confirmed by biochemical and pathological testing of brain to have a prion disease. At the conclusion of FY14 11 of 11 orally infected squirrel monkeys also developed disease. At the conclusion of FY16 a total of twelve (2 in FY16)CWD-infected cynomologus macaques had been euthanized and screened for prion disease. None of these twelve cynomologus macaques have developed prion disease regardless of inoculation route. Three cynomologus macaques remain on this portion of the study and plans to euthanize and screen the remaining monkeys for prion disease at the end of FY16 are in place. During FY08 two cynomologus macaques and two squirrel monkeys were inoculated with brain homogenates derived from a CWD infected squirrel monkey to evaluate the ability of CWD to adapt to a nonhuman primate host. During FY10 both squirrel monkeys inoculated with squirrel monkey adapted CWD developed disease. The incubation period from this inocula was much faster and clinical signs were slightly different suggesting adaptation to a new host or a higher titer of inocula. The successful passage of CWD derived from a squirrel monkey into additional squirrel monkeys confirms the presence of prion infectivity. This confirmation was important since the same squirrel monkey CWD inocula did not cause disease in transgenic mice expressing human or deer prion protein and has not caused disease in any of the cynomolgus macaques still under study. During FY13 one of the cynomologus macaques was euthanized due to chronic weight loss and liver failure. This monkey was tested for TSE disease and was negative, indicating that squirrel monkey adapted CWD may still be unable to infect other species on non-human primates. The remaining monkey in this study will be euthanized and tested for prion disease at the end of FY16. In addition to testing infected squirrel monkey brain we are also evaluating blood from infected squirrel monkeys for the presence of prion infectivity. None of the blood product recipient monkeys have shown any signs of disease at the close of FY16. To further test adaptation of CWD to either a human tropism we inoculated material from the clinically ill second passage squirrel monkeys into transgenic mice expressing human prion protein (tg66) during FY11. During FY12 these tg66 mice were euthanized and tested for prion disease. All of the mice in this second passage study were negative for prion infection. The lack of transmission to the "humanized" mice is encouraging data that supports the conclusion that CWD will likely not infect humans. During FY15 we started a study to directly test the transmission of cervid dervied CWD into the tg66 mice. These mice have been inoculated and have not developed disease at the end of FY16. They will continue to be monitored for prion disease onset.