小鼠VSV病毒性脑膜脑炎感染模型的建立

Model establishment of VSV-caused meningoenencephalitis in mouse

目的摸索稳定、确实的VSV病毒性脑炎的感染指标,为筛选有效的抑制性ODN建立动物模型。方法经滴鼻给Balb/c雌性小鼠接种VSV病毒,感染后每天记录小鼠体重变化,在感染鼠体重最低点取小鼠脑组织:用HE染色法观察病理改变,用伊文氏兰染色法观察血脑屏障的破坏情况;用VSV易感的Vero细胞测定脑组织VSV毒力。结果Balb/c小鼠经滴鼻感染VSV病毒后第6天体重下降最为明显,此后体重呈平缓升高。取感染后第6天的小鼠脑组织作HE染色,发现如下病理改变:血管出血、充血和淋巴细胞套;噬神经细胞现象;软化灶和胶质小结的形成;脑膜炎反应;海马颗粒消失。此外用伊文氏兰染色发现VSV感染小鼠血脑屏障破坏。但是脑组织悬液中VSV病毒含量在感染后第6天已呈现下降的趋势。结论观察到VSV病毒感染后炎症改变最为明显的时间点要滞后于脑组织中病毒含量最高的时间点,推测病毒本身并非造成炎症改变的直接原因,结合文献报道,考虑可能是免疫系统在应答过程中攻击了机体自身组织的结果,所以该模型可以作为筛选抑制免疫反应过强的抑制性ODN的体内筛选平台。

Objective To find out the encephalitis signs of VSV-infected mice as in vivo model to screen effective suppressive ODN for antivirus purpose. Methods Balb/c mice were challenged by 20 μL of 500 × TCID50 （ tissue culture infectivity dose） VSV that was equally administrated to both nostrils. PBS was used as the negative control. After VSV infection, the meuse was sacrificed following deep anesthesia with isoflurane and the whole brain of mouse was removed at different time. Hematoxylin and eosin （HE） stainings of one-half of the brain were applied to observe pathological changes, and Vero cell, which was sensitive to VSV, was used to detect VSV virulence in the suspension from the other-half of the brain. The permeability of blood brain barrier was evaluated via tail vein injection of Evan＇ s blue. Resulfs After being infected with VSV, the weights of mice lost daily till to the sixth day and then re-increased gradually. On day 6, significant changes of viral encephalitis were showed upon pathological detection of brain tissue： inflammatory response of blood vessel, neuronophagia phenomenon, occurrence of soften focus, the formation of glial nodule, meningitis response and the disappearance of hippocampus granules. Meanwhile, the blood braind barrier breakdown of infected mice was observed by obvious blue staining of the whole brain. Surprisingly, brain suspension from VSV-infected mice on day 6 presented weak infectivity compared with that on day 3. Conclusion Compared with high VSV concentration on day 3 after virus infection, delayed occurrence of significant inflammatory changes on day 6 indicates that virus itself might not be the direct reason for the inflammation. Thus, VSV-infected encephalitis may become a reasonable in vivo model for the screening of suppressive ODN, which has the potential to negatively regulate the immune response and reduce the symptoms caused by the inflammation.