Level Of IL-6,TNF-α In Peripheral Blood And Apoptosis Of Brain Cells In Mice Infected By Enterovirus 71

Objective To observe mice reaction to enterovirus 71 infection, pathological changes on lung and brain tissues, the concentration of IL-6, TNF-αin mice peripheral blood and apoptosis of brain cells.Methods We chose five days balb/c mice to create an animal model of EV71 infection. All mice were divided into experimental group and control group according to different treatment factors. Mice in experimental group were infected intragastricly with 100TCID50 EV71 strains and others were injected intragastricly with same volume of RPMI1640 as controls. Symptoms in mice were observed after inoculated and graded daily; pathological changes on lung and brain tissues were observed through hematoxylin-eosin staining; EV71 mRNA in mice brain was detected by RT-PCR at different time (1d,3d,5d,7d) postinfection. Level of IL-6, TNF-a in peripheral blood was detected by ELISA. Brain single-celled levitation liquid was collected through nest screening method and the apoptosis in mice brain cells was analyzed by Annexin V/PI with flow cytometry. The results were analyzed by analysis of variance.Results (1) Symptoms such as less move, arch back and raising tail occurred in experimental group one day after infection, followed by weight dropping dramatically at day 3, then seven mice appeared hind limb paralysis, and then died at day 5 post-infection. Mice in control group remained healthy and grow normally. (2) Obvious pathologic changes appeared on lung tissue at 3 days after infection, with the performance of the alveolar walls thickening, large numbers of lymphocytes infiltration, pulmonary edema, and obvious performance on brain as large glial cells hyperplasia, no changes were seen in control group; (3) EV71 RNA could be detected by RT-PCR in brain at 5 days and 7 days postinfection. And EV71 RNA could not be detected at 1 day,3 day postinfection and in control group. (4) Levels of IL-6, TNF-αof experimental group were obviously higher than control group (p<0.05). And levels of IL-6, TNF-areached their peaks at 24-72h postinfection and then declined to the normal level at 7 days postinfection. (5)Apoptosis in mice brain cells can be detected at 3 days after infection, and levels reached their peaks at 5d postinfection. Levels of brain cells apoptosis were declined at 7d after infection, but still higher than that of control group. Conclusion (1) Symptoms occurred in normal mice after EV71 strain inoculation, pathological changes are seen on lung and brain tissues and EV71 RNA can be detected in brain tissue, therefore, this model can simulate central nervous system infection caused by EV71,but the outcome of infection may not ideal for application as animal model. (2) Level of IL-6, TNF-a in peripheral blood increases at early age after infection, then decreases after 72h,and remains normal at day 7,which can induce inflammatory reaction. (3) EV71 infection can induce apoptosis in brain cells at early age after infection, and reached their peaks at day 5, which is in accord with EV71 RNA detection. (4) Immune injury and apoptosis take place in the process of Central nervous system injury caused by EV71.