Activation of complement system in central nervous system (CNS) of the patients suffering from prion diseases or animal models infected with prion agents experimentally is reported repeatedly, but which pathways are involved in the complement system during prion infection is not well documented. Here, we evaluated the level of complement factor B (CFB), which is the key factor that triggers alterative pathway (AP) of complement in the brain tissues of scrapie-infected mice with various methodologies. We found that the levels of mRNA and protein of CFB significantly increased in the brain tissues of scrapie-infected mice. Morphologically, the increased CFB-specific signal overlapped with the elevated C3 signal in brain sections of scrapie-infected mice, meanwhile overlapped with damaged neurons and activated microglia, but not with the proliferative astrocytes. Additionally, the level of complement factor P (CFP), the key positive regulator of AP, also increased remarkably in the brain tissues of infected mice. The transcriptional levels of CD55 and CD46, two negative regulators of AP, decreased without significance in brain tissues of scrapie-infected mice at the terminal stage. However, the mRNA and protein levels of CFH, another negative regulator of AP, increased. Through the dynamic analyses of the expressions of CFB, CFP, and CFH in brain sections of 139A-infected mice, which were collected at different time-points during incubation period, illustrated time-dependent increase levels of each factor during the incubation period of scrapie infection. Taken together, our data here demonstrate that the AP of complement cascade is activated in the CNS microenvironment during prion infection.

中文翻译：

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在瘙痒病感染的啮齿动物的大脑中激活了替代补体途径。

重复报道了实验性repeatedly病毒疾病或感染animal病毒剂动物模型的患者中枢神经系统（CNS）中补体系统的激活，但病毒感染过程中补体系统涉及哪些途径尚未得到充分报道。在这里，我们用各种方法评估了补体因子B（CFB）的水平，补体因子B（CFB）是触发瘙痒病感染小鼠脑组织中补体改变途径（AP）的关键因素。我们发现在瘙痒病感染的小鼠的脑组织中，CFB的mRNA和蛋白水平显着增加。从形态上讲，在瘙痒病感染的小鼠脑部，增加的CFB特异性信号与升高的C3信号重叠，同时与受损的神经元和活化的小胶质细胞重叠，但不与增生星形胶质细胞有关。此外，AP的关键正调节因子补体因子P（CFP）的水平在受感染小鼠的脑组织中也显着增加。AP的两个负调控因子CD55和CD46的转录水平在终末期被瘙痒病感染小鼠的脑组织中降低而无意义。然而，APH的另一种负调节剂CFH的mRNA和蛋白质水平却增加了。通过动态分析139A感染小鼠在潜伏期的不同时间点大脑切片中CFB，CFP和CFH的表达，阐明了瘙痒病潜伏期各因子随时间的升高水平感染。在一起